ISSN:0144-557X    

DOI:10.1039/AP99330FX033

出版商:RSC    

年代:1993

数据来源: RSC

摘要:

September 1993 Analytical Proceedings 367 369 37 1 372 374 ANPRDI 30(9) 353-384 (1 993) Proceedings of the Analytical Division of The Royal Society of Chemistry CONTENTS 353 VAM Viewpoint 354 Report of Meeting 355 Analytical Viewpoint ’Determination of Organosulfur Compounds and Amino Acid-Mustard Conjugates by Liquid Chromatography with Amperometric Detection‘ by A. J. Clark ‘Total and Bioavailable Aluminium in Foods and Beverages‘ by H. Trevor Delves, Christine E. Sieniawaska and Bharat Suchak 358 SUMMARIES OF PAPERS 358 Analytical Problems with Food 358 ‘Analytical Rationalization’ by Chris J. Goodwin ’Quantitative Determination of Sumatriptan by Capillary Electrophoresis’ by K. D. 365 361 Short Papers in Pharmaceutical Analysis 361 363 Altria and S.D. Filbey ’Enantiomeric Separation of Ciprofibrate and Analogues Using a Cellulose-based Chiral Stationary Phase‘ by A. Scott, P. R. Vojvodic, N. H. Anderson and B. J. Clark ’Inorganic Salts as Modifiers in the High-performance Liquid Chromatography Mobile Phase Used to Chromatograph AtenoIoI’ by Alison E. BretnaII and Thomas Cowen ‘Determination of Dextromethorphan and its Metabolites in Human Urine Using Solid-phase Extraction and Reversed-phase High-performance Liquid Chromatography’ by Rachel Howling and George Hutchinson ‘Development of a Method for the Detection of Angiotensin Converting Enzyme Inhibitors Using Electron Capture-Gas Chromatography Detection’ by K. M. Sereda, T. C. Hardman, M. R. Dilloway and A. F. Lant ’Determination of Total and Ionic Chloride and Bromide in a Cross-linked Quaternary, Ammonium-substituted Polymethacrylate by Ion Chromatography‘ by Ian D. Smith, Paul D. Blackler and David G. Waters ’Use of Radiolabelled Drug Substances to Investigate Mass Balance During Validation of a High-performance Liquid Chromatography Method for Impurities’ by A. A. Priestner 378 Equipment News 381 Conferences and Meetings 382 Courses 384 Analytical Division Diary 0144-557XC199319:1-3 ... 111 ANALYTICAL PROCEEDINGS, SEPTEMBER 1993, VOL 30

ISSN:0144-557X    

DOI:10.1039/AP99330BX035

出版商:RSC    

年代:1993

数据来源: RSC

摘要:

ANALYTICAL PROCEEDINGS, SEPTEMBER 1993, VOL 30 353 Bringing Microbiological Testing Under Control Over the last decade, quality assurance has attained a high profile within micro- biological testing laboratories. This is partly in response to an appreciation of the possible benefits by workers in micro- biology, and partly in response to the need to move in sympathy with similar developments in closely related fields. The need for quality control and assess- ment is underlined by the intrinsic nature of the science of microbiology, concerned as it is with living organisms which often display a great capacity for genetic varia- tion. The detection and identification of microbes involves the use of potentially variable reagents, such as antisera, and of inherently variable growth media and tissue culture cells.There is, therefore, a strong driving force to produce biological reference preparations or standards which can help to bring increased relia- bility and reproducibility to analytical procedures, and counter the perception of microbiology as a subjective science. The issuing of an incorrect laboratory report in microbiology can have serious consequences for public health. The pre- vention, early detection, and control of aq outbreak of disease or a food poisoning incident depends upon rapid and accurate laboratory tests. The microbiologists' day-to-day task of interpreting and reporting laboratory results accurately requires a degree of confidence in the various procedures in use. These include the means by which the samples are taken and transported to the laboratory, the sensitivity and specificity of the test method and reagents used, and their reproducibility in practice.Reporting procedures also need to be subject to quality control. The main aim of accredi- tation is to ensure that a quality system is in place which will enable effective labor- atory management, eliminate preventable inaccuracy and ensure accurate and timely reporting of results. Some of the areas which are likely to give rise to problems in achieving accredi- tation of microbiological testing include method validation, media production, use of autoclaves and staff training. There is often confusion between the terms method validation and quality control. Method validation measures what the method is capable of and defines its limiting characteristics, while quality con- trol systems show that the method is meet- ing pre-defined standards.Users must always validate a method before applying it in their laboratory, even in the case of published or standard methodologies. A particular problem is the tendency for users to modify standard or accredited methods by reducing volumes of reagents used for reasons of economy, either by the use of in-house produced reagents in combination with kit components, or by modification of procedures. Such modifi- cations are not necessarily harmful but they are quite likely to alter the operating characteristics of the test. Many labora- tories do not investigate these effects owing to a lack of time or resource. It is important to appreciate that modifica- tions of methods may have consequences which are difficult to predict and for this reason modified methods must be re- validated by the user.Culture media are vital to microbio- logy, as without good media there is little chance that good results will emerge from the laboratory. Most culture media used in the northern hemisphere are commer- cially produced and have passed fairly extensive testing before release. How- ever, as the media undergo reconstitu- tion, heat processing and perhaps supple- mentation with additives in the laboratory, it is essential to have control over these processes also, and to test the final media. Quality control testing of the final medium is not intended as a substi- tute for the proper control of culture medium processing, but is a reliable adjunct and will provide an indicator of performance in subsequent use. Physical characteristics should also be monitored.For example, a drift in pH may indicate that a batch of medium has been over autoclaved, and merely re-adjusting the pH prior to use (which is common prac- tice) does not compensate for all the effects of over-heating. It should be noted that in spite of extensive quality testing no culture medium is perfect and capable of recovering all strains of the target orga- nisms. This is mainly because testing protocols are designed to measure the major or significant characteristic of the medium. A quality control procedure has little value in a quality system unless it con- tributes to the over-all aim of ensuring that all measurements are fit for purpose.For example, there is little to be gained from undertaking duplicate analyses where negative results are anticipated, while spiked samples provide little extra data when dealing with positive samples. In the latter case, 5-10% duplicate test- ing is advisable. Every microbiological test should be controlled with both posit- ive and negative control strains, particu- larly test media and reagents immedi- ately after preparation and also after extended storage if the media are used infrequently. A correctly functioning autoclave is as important to good laboratory analysis as is the culture collection to quality control. Without it, the laboratory has no way of preparing sterile, high quality media, nor of disposing safely of con- taminated waste.Autoclaving is critical to the performance of the media and hence the final analysis. Despite much attention, several issues remain unre- solved. For example, a temperature of 121 "C for 15 min is commonly used for media sterilization but it is not clear whether this should be monitored in the media or in the autoclave chamber. It is also well known that distribution of tem- perature within an autoclave is not uniform and varies with load. For ex- ample, calibration tests in a fully loaded autoclave have shown that the top of the autoclave can take 15 min longer than the bottom to reach the correct holding temperature. The common practice is to compensate by adding 15 min to the over-all holding time for the load. While this practice ensures that the top of the autoclave receives the recommended sterilizing regime, the media at the bot- tom are grossly over-heated. Further- more, the range of temperatures within which effective sterilization occurs with- out unduly affecting the quality of the media is not well established. In addition to standardizing procedures and methodology, the importance of keeping effective records cannot be over- emphasized.The keeping of sample records provides assurance that quality control procedures have been carried out, aids the detection of faulty batches of media or reagents, encourages a methodi- cal approach to analysis, and underlines accountability. Effective implementation of analytical procedures is totally dependent upon the skills and knowledge of the operator.Training should be structured and under- taken by senior personnel as it is funda- mental to quality. Too often new entrants are taught procedures by junior employees. Objective rather than subjec- tive assessments should be in place. Although many laboratories initially train354 ANALYTICAL PROCEEDINGS, SEPTEMBER 1993, VOL 30 personnel and check their performance, little attention is given to maintaining and checking competence. Mis-reading test results because of lack of familiarity is an important cause of error. It must be noted that good academic qualifications do not signify good practical skills, especially as training courses with limited resources often concentrate on theory with insuf- ficient practical backup. The development and wider appli- cation of accreditation to microbiological testing is an area of growing interest and importance.As this article shows, there are many issues which need to be addressed and more are likely to emerge as our understanding of the underlying science develops. At present, across Europe, there is a wide diversity in the way accreditation authorities have approached microbiological testing, and this has resulted in some laboratories going for ‘overkill’ on procedures. EURACHEM and WELAC have recog- nized this problem, and a joint working group has begun the task of preparing guidance for both laboratories and assessors on the interpretation of the quality standard EN45001 and I S 0 Guide 25 for microbiological testing. For further information, or to make contributions to the preparation of the guidance, please contact either of the joint Chairpersons of the working group: Dr.Surrinder Johal, Laboratory of the Government Chemist, Queens Road, Teddington, Middlesex TW11 OLY (Tel: 081-943-7436); Dr. Jane Beaumont, NAMAS Executive, NPL, Teddington, Middlesex TWll OLW (Tel: 081-943- 7055). Report of Meeting Micro and Chemical Methods Group The forty-ninth Annual General Meeting of the Group was held at 6.15 p.m. on Wednesday, November 25, 1992, in Koom X129 in the St. Philips Building, at the London School of Economics and Political Science, Sheffield Street, Lon- don, WC2. The Chair was taken by the retiring Chairman of the Group, Dr. Maurice Russell. The following office bearers were elected for the forthcoming year: Chairman-Mr. B. T. Saunderson. Vice-Chairman-Dr. M. A. Russell. Honorary Secretary -MS. L. Dixon, Car- naud Metalbox Technology plc, Downs- view Road, Wantage, Oxfordshire OX12 9BP. Honorary Treasurer-Mr. M. R. Cottrell. Honorary Assistant Secre- tary-Mr. A. Fassam. Members of Com- mittee-Mr. P. R. W. Baker, Mrs. D. Butterworth (co-opted), Mr. B. Oliver and Mr. G. Powell (co-opted). Mr. H. Shalgosky and Professor D. Wilson were re-appointed as Honorary Auditors.

ISSN:0144-557X    

DOI:10.1039/AP9933000353

出版商:RSC    

年代:1993

数据来源: RSC

摘要:

ANALYTICAL PROCEEDINGS. SEPTEMBER 1993, VOL 30 355 Analytical Viewpoint The following is a member of a continuing series of articles providing either a personal view of part of one discipline i n analytical chemistry (its present state, where it may be leading, etc.), or a philosophical look at a topic of relevance to chemists in general or analytical chemists in particular. These contributions need not have been the subject of papers at Analytical Division Meetings. Persons wishing t o provide an article for publication in this series are invited to contact the editor of Analytical Proceedings, who will be pleased to receive manuscripts or t o discuss outline ideas with prospective authors. Determination of Organosulfur Compounds and Amino Acid-Mustard Conjugates by Liquid Chromatography with Amperometric Detection A.J. Clark Chemical and Biological Defence Establishment, Porton Down, Salisbury, Wiltshire SP4 OJQ The analysis of organosulfur compounds using electrochemical (EC) detection has, in the past, largely been restricted to measurements made in the reductive mode at the dropping mercury electrode. With the exception of thiols, relatively few reports relate to electrochemical oxidations at solid electrodes and those that do suggest difficulties which would lead to poor quantification and irreproducibility . Thus, Nicholson’ has demonstrated a 2-electron anodic oxidation of dialkyl sulfides at the platinum electrode, corresponding to the formation of the sulfoxide, but has found evidence for poisoning of the electrode surface and for irreversibility of the system.Of the sulfides and thiols examined by Cottrell and Mann,2 all show irreversible oxidation at the platinum electrode. Kissinge? has also reported that thiols are difficult to oxidize at graphite electrodes in the absence of mercury as a catalyst, whilst at platinum and other solid electrodes oxidations lead to disul- fides, but at much higher positive potentials than are required at the dropping mercury electrode, and they are totally irreversible. Cox and Przyjazny4 have attempted to use amperometric detection for the quantitative determination of organosulfur compounds following separation by liquid chromatography (LC). Whilst this work includes a comprehensive study of aryl and alkyl thiols, sulfides, disulfides and sulfones, only thiols could be detected over the +0.6 V to - 1.0 V range applied to the carbon paste working electrode.The aim of the present work is to extend LC techniques to other electroactive sulfur-containing species by optimizing the chromatographic and electrochemical conditions. A particular attraction of LC is its ability to separate those compounds which are thermally labile or of low volatility. A further application considered here is in the separation and identifica- tion of amino acid conjugates formed with bis(2-chloroethyl) sulfide (Mustard gas). These conjugates have been identified by other workers”‘ as possible in-vivo products of Mustard gas poisoning. They are high melting-point solids which are insoluble in organic solvents and therefore not amenable to direct analysis by gas chromatography.It is hoped that the development of a simple LC-EC technique might provide a means to distinguish between conjugates and naturally occur- ring sulfur-containing amino acids which could be of benefit to medical treatment regimes. The possibility of analysing for various organosulfur compounds by LC-EC has therefore been explored using synthetic mixtures, the results of which are described below. Experimental Initial voltammetric studies were undertaken in static solution using a Metrohm E506 Polarecord equipped with a Metrohm 648 voltammetry stand and Metrohm E608 controller. The electrochemical cell consisted of a saturated Ag-AgC1 elec- trode with a platinum auxiliary electrode and a glassy carbon working electrode.Anodic scans were performed in a back- ground electrolyte of 10% v/v acetonitrile-water containing 0.008 mol I-’ H3P04. Liquid chromatography was performed using a Waters 6000A HPLC pump. The separating columns were 125 X 5 mm i.d. and the support media included Hypersil ODs, Phenyl Hypersil (both as ready-packed columns from Highcrom Ltd.) and Techsil (HPLC Technology Ltd.). Samples were intro- duced onto the column via a Rheodyne 7125 valve fitted with a 10 PI sampling loop. The amperometric detection system for liquid chromatography was a Metrohm VA-641 controller and Metrohm 656 cell of wall-jet design. The latter was fitted with a glassy carbon auxiliary electrode, Ag-AgCI-KCl (sat .) refer- ence electrode and either a glassy carbon (Metrohm) or epoxy- carbon working electrode.’ A column heater (Jones Chroma- tography) was used to control column temperature and the flow through detector cell was thermostated from a circulated water supply to within LO.1 “C to avoid baseline drift.Column and detector were thus maintained at the same constant temperature. Acetonitrile and methanol (HPLC far-UV grades from Fisons plc) were used as mobile phases. Water was of de- ionizedh-everse-osmosis purity and all inorganic compounds were of analytical-reagent grade (BDH Chemicals). Amino acids were obtained from Aldrich Chemical Company Ltd. The organosulfur compounds and amino acid conjugates (listed below) were synthesized on-site. Samples for LC-EC analysis were dissolved in mobile phase, with sufficient dilute hydro- chloric acid being added, in the case of the conjugates, to assist with dissolution.Sulfur Compounds Class: common name, IUPAC nomenclature, [CAS Registry No]. Alkyl sulfides: thiodiglycol, 2,2’-thiobis(ethanol), [ 111-48- 81; thiodiglycol dimer, 3,9-dithia-6-oxaundecane-l,ll-diol, 17426-02-01 ; 174-dithiane, [505-29-31; 1 ,4-thioxane7 [ 15980- 15- 11.356 1 4 0 , I ANALYTICAL PROCEEDINGS, SEPTEMBER 1993, VOL 30 0 1 1.1 1.2 1.3 1.4 1.5 Applied potentialN Fig. 1 thiodiglycol; 0, mustard sulfoxide Hydrodynamic voltammograms. 0, Thiodiglycol dimer; A. Alkyl disulJide: dithiodiglycollic acid, 2,2'-dithiobis(acetic acid), [505-73-71. Alkyl sulfoxides: mustard sulfoxide, 1 ,l'-sulfinylbis(2- chloroethane), [5819-08-91; thiodiglycol sulfoxide, 2,2'-sul- finylbis(ethanol), [3085-45-81.AEkyl sulfones: mustard sulfone, 1 , l '-sulfonylbis(2-chloro- ethane), [471-03-41; thiodiglycol sulfone, 2,2'-sulfonylbis- (ethanol), 12580-77-01. Thiol: thioglycollic acid, mercaptoacetic acid, [68-11-11. Sulfur amino acids: cysteine, [52-90-41; reduced glutathione, [70-18-81; methionine, [63-68-31. Amino acid-mustard conjugates: bis(cysteinylethy1) sulfide, S[CHZCH2SCH2CH(NH2)CHCOOH]*; bis(cysteinylethy1) sulfone, 02S[CH2CH2SCH2CH(NH2)CHCOOH]2. Fig. 2 LC-EC chromatogram for a mixture of organosulfur com- pounds. Column, 12.5 cm x 5 mm i.d. Tcchsil; mobile phase, 10% MeCN + 90% 0.008 moll-' H,PO,; flow rate, 1.0 ml min-'; applied potential, 1.45 V. Peaks are: 1, thiodiglycol sulfoxide; 2, thiodiglycol; 3, thioglycollic acid; 4, dithioglycollic acid; 5 , 1 ,bthioxane; 6 , mustard sulfoxide; 7, thiodiglycol dimer; 8, 1,4-dithiane Table 1 Identity of peaks in Fig.2 Peak Retention No. Sulfur compound time/min Thiodiglycol sulfoxide Thiodigl ycol Thioglycollic acid Dithioglycollic acid 1,4-Thioxane Mustard sulfoxide Thiodiglycol dimer p-Dithiane 1.4 1.9 2.4 4.6 6.5 7.5 8.4 22.2 Amount injected/ ng 442 14 5 12 24 1387 41 27 Detection limit injected) 30 1 0.5 2 2 100 4 5 (ng Results and Discussion Differential-pulse voltammetric scans at a glassy carbon electrode in static solution produced broad, poorly-defined peaks with low sensitivity. Response to sulfide and thiol groups occurred at high oxidation potentials close to the anodic limit of the electrolyte (+ 1.5 V), while no response was recorded for sulfoxide.It was also established that there was insufficient resolution to enable the direct analysis of mixtures to be undertaken in this way. The response was greatly improved by using a flow-through amperometric detector. This supported the known advantages of using dynamic conditions of measurement, i.e., enhanced sensitivity due to mass transport; self-cleaning effects of the wall-jet configuration; and good signal-to-noise from simpler electronics. These factors were important to successful LC-EC analysis. Fig. 1 illustrates hydrodynamic voltammograms obtained in a mobile phase of 10% v/v acetonitrile-90% 0.008 mol I-' H3P04, employing a Techsil column and a flow rate of 1 ml min-'. The detector response is seen to increase with increase in the applied potential (at the expense of some increase in noise and background current). Selectivity over and above the chromatographic differentiation could be achieved by adjusting the applied potential.Thus, in the mixture of 3 compounds shown in Fig. 1, only thiodiglycol dimer was detected below a potential of + 1.1 V. Mustard sulfoxide was found to respond close to the potential limit for the mobile phase, accounting for the absence of a peak in the static voltammetric scans. Sulfoxide was successfully determined by setting the fixed potential of the EC detector at +1.45 V and through careful control of the ionic strength of the mobile phase to limit background current. Sulfones could not be detected as they were not susceptible to further electrochemi- cal oxidation. More classes of organosulfur compound were detected than had been obtained by previous workers4 who had been limited by background current to a narrower voltage range.This had prevented the detection of compounds such as sulfides and disulfides. Chromatographic conditions were optimized to obtain good separation of mixtures. Acetonitrile-water was favoured over methanol-water as the mobile phase because of its lower polarity, which resulted in shorter separation times. Sensitivity was also higher in acetonitrile-water because of a lower background current, and corresponded to 1-2 ng injected for thiodiglycol. The pH of the mobile phase was held between 2 and 3 to ensure the ionic suppression of thioglycollic acid (pK, 3.7), thus enabling.its separation from the solvent front.The addition of buffers and salts, when compared with simple acid addition, gave poorer separations because of the higher ionic strength. It also resulted in increased background current, reducing sensitivity and limiting the potential range at higher voltages. The effect on retention time and order of elution of varying the acetonitrile-water composition was investigated. Phenyl Hypersil was favoured for analysis of more strongly retained compounds such as 1,4-thioxane and p-dithiane because of shorter elution times. Better peak resolution was, however, obtained with Hypersil ODS and more especially with Techsil (Fig. 2). For less complex mixtures it was possible to adjust mobile phase composition either to reduce the retention time or to change the order of elution, thereby reducing peak spreading and improving the detection limit.The epoxy-based carbon electrode was found to stabilize more rapidly than the glassy-carbon electrode and exhibited less drift, making it the working electrode of choice. No poisoning problems were encountered with either electrode; the wall-jet design provided efficient product removal and a surface cleaning effect from the flowing mobile phase. The method was evaluated for field collected samples suspected of mustard agent contamination (Table 2). The useANALYTICAL PROCEEDINGS, SEPTEMBER 1993, VOL 30 1 1 357 Table 2 Analysis of samples suspected of mustard contamination Peak retention time/min (conditions as for Fig. 2) Swab (extract) from equipment Sand extract 1.9 1.9 - 5.3 - 8.4 1 I I---- Fig.3 LC-EC chromatogram of sulfur-containing amino acids and amino acid-mustard conjugates. Column conditions as for Fig. 2 except applied potential 1.36 V. Peaks are: 1, cysteine; 2, bis- (cysteinylethyl) sulfone; 3, reduced glutathione; 4, methionine; 5, bis(cysteinylethy1) sulfide of aqueous eluent precluded direct determination of mustard because of rapid hydrolysis, but a peak corresponding to thiodiglycol, the major hydrolysis product, was readily detect- able. Two additional peaks were recorded for the sand extract; one corresponded to thiodiglycol dimer, whilst the other (5.3 min) remained unidentified. Thiodiglycol dimer is the hydrolysis product of another chemical warfare agent, formula (CICH2CH2SCH2CH2)20, the presence of which in the original sample, along with that of mustard, was confirmed by GC-MS analysis.The separation of sulfur-containing amino acids and amino acid-mustard conjugates is illustrated in Fig. 3 (see also Table 3). The same chromatographic conditions were applied as in Fig. 2, except a potential of +1.36 V was applied instead of +1.45 V. The conjugates of mustard with cysteine and glutathione have been reported as major metabolites of mustard systemic p o i ~ o n i n g . ~ . ~ They are solids of high melting- point (240-25O0C), which are not directly amenable to gas chromatography (see introduction). Preliminary results using a Table 3 Identity of peaks in Fig. 3 Peak No. Sulfur compound 1 Cysteine 2 Bis(cysteinylethy1) sulfone 3 Reduced glutathione 4 Methionine 5 Bis(cysteinylethy1) sulfide Amount Retention injected/ ng time/min 1.6 10 1.7 34 1.9 16 2.5 34 3.1 42 mixture of prepared sample standards indicate that analysis can be successfully performed which might well be applicable to the treatment of poisoning, although interference effects and detection limits remain to be evaluated for real specimens of blood and urine.Published work on the analysis of glutathione in blood by LC-EC suggests the type of sample preparation procedure which might be employed.8 Conclusions In this investigation it has been shown that thiols, alkyl sulfides, alkyl disulfides and alkyl sulfoxides can be detected by electrochemical oxidation in a flow-through wall-jet cell. It has been possible to use this as a method of analysing for individual components in mixtures of these compounds following their separation on a reversed-phase HPLC column.The ability to work at high positive potentials has revealed a response to classes of sulfur compound hitherto undetected by LC-EC. This makes the method competitive with other analytical techniques such as HPLC-UV, combined with the advantages of a lower detection limit and the wide linear dynamic range expected from an electrochemical technique. The ability to separate compounds which exhibit low thermal stability and high melting-point is exemplified by the successful separation of amino acid-mustard conjugates. From this it is concluded that it should be feasible to determine mustard metabolites in body fluids following appropriate sample preparation. It is further suggested that the proposed method might find application in the diagnosis and treatment of patients ,suffering from the effects of Mustard gas poisoning. The author is grateful to Dr. A. Fogg of Loughborough University of Technology for providing the epoxy-carbon working electrode. References Nicholson, M. M., J. Am. Chem. SOC., 1954, 76, 2539. Cottrell, P. T., and Mann, C. K., J. Electrochem. Soc., 1969, 116, 1499. Kissinger, P. T., Anal. Chem., 1977, 49,447A. Cox, J. A., and Przyjazny, A . , Anal. Lett., 1977, 10, 869. Roberts, J. J., and Warwick, G. P., Biochem. Pharmacol., 1963, 12, 1329. Davison, C., Rozman, R. S., and Smith, P. K., Biochem. Pharmacol., 1961, 7, 65. Henriques, H. P., and Fogg, A. G., Analyst, 1984, 109, 1195. Rabenstein, D. L., and Saetre, R . , Clin. Chem., 1978,24, 1140.

ISSN:0144-557X    

DOI:10.1039/AP9933000355

出版商:RSC    

年代:1993

数据来源: RSC

摘要:

358 ANALYTICAL PROCEEDINGS, SEPTEMBER 1993, VOL 30 Analytical Problems with Food The following is a summary of one of the papers presented at a Meeting of the Analytical Division held on November 16,1992, in the Scientific Societies' Lecture Theatre, London W1. Total and Bioavailable Aluminium in Foods and Beverages H. Trevor Delves, Christine E. Sieniawaska and Bharat Suchak Supra-regional Assay Services Unit for Trace Elements, University of Clinical Biochemistry, Southampton General Hospital, Southampton SO9 4XY Concern over the possible link between environmental ex- posure to aluminium and Alzheimers disease' has focused attention on the variable levels of aluminium in foods and has questioned whether higher levels pose any possible risk to health. Recent studies2 have shown that in the United Kingdom the concentration of aluminium in foods ranges from less than 1 pg kg-' to greater than 1 g kg-I.This six-order of magnitude variation in aluminium in readily available foods has three origins: ( I ) the natural aluminium content of foods; (2) contamination of foods during processing, storage or cooking; (3) the use of permitted aluminium additives to foods. The extent to which the resultant aluminium in consumed foods or beverages is absorbed across the intestinal wall and reaches the body's circulatory system, i.e. , the bioavailability of alumi- nium, depends upon concomitant species which may complex with and affect the transport of aluminium. This paper deals with the variability of aluminium in our food and drink and with simple tests to allow some assessment of the bioavail- ability of aluminium.Aluminium in UK Foods and Beverages The very wide range of aluminium concentrations found in commonly available UK foods and beverages is shown as a cumulative frequency distribution in Fig. 1. The 598 samples comprised 55 different types of food or beverages; 25 samples of duplicate diets and 100 samples from the 'UK Total Diet Study' organized by the Ministry of Agriculture, Fisheries and Food (MAFF). The concentration of aluminium in the 598 samples ranged from less than 1 pg kg-' to greater than 1.4 g kg-'. Generally low concentrations (0.02-0.36 mg kg-l) were found in eggs, carrots, potatoes, carcass meats and fresh fish. Higher values, up to 8 mg kg-', were seen in cereals. Only 10% of samples had concentrations in excess of 25 mg kg-l.The very high natural aluminium content of tea was confirmed (420-620 mg kg-I). The highest values, up to 1.47 g kg-' were seen in flour mixes with permitted aluminium additives. The samples were analysed in triplicate for aluminium using electrothermal atomization and atomic absorption spec- trometry following various sample preparations which, depending upon the matrix, included one or more of the following: simple dilution with a chemical modifier; ashing with nitric and sufuric acids; solvent extraction. Analytical accuracy was ensured by carrying out for each type of sample: internal quality control; recovery tests; and concurrent analysis of reference materials selected from: National Institute of Standards and Technology (NIST) total diet, bovine liver, orchard leaves, non-fat milk powder, rice flour, wheat flour.In addition, most samples, 570 (%yo), were analysed using the method of standard additions and by using matrix matched calibrating standards. The results of these comparisons are shown in Fig. 2. The proximity of the data points to the line with unit slope indicates good analytical agreement over a wide concentration range for all samples. Average Daily Intake of Aluminium from Diets From the data in Fig. 1 and especially the total and duplicate diet analyses, the mean daily intake of aluminium for adults is -3 -1 1 3 Loglo (aluminium content/mg kg-1) Aluminium in foods and beverages: 598 samples of 97 types of Fig. 1 foodddrinks -3A I I I J -3 - 1 1 3 Log,, (Al/mg kg-l) calibration Fig.2 Repeated determination of aluminium: 570 samples of foodsldrinksANALYTICAL PROCEEDINGS, SEPTEMBER 1993, VOL 30 359 Table 1 Some fooddbeverages naturally high in aluminium. Tinned baked beans in tomato sauce contained only 0.41 t 0.02 mg kg-* ( n = 3 ) . Aluminium contendmg kg- ' Soya bean, raw 11.6 t 1.9 (3) Soya bean, washed 4.8 k 0.3 (2) Textured savoury Soy-mince 25.0 k 1.6 ( 3 ) Tea (leaf) soluble Al 533 (7.1)* Tea (bag) soluble 90 (1.2)* Sample Mean k SD ( n ) Unflavoured Soy-mince 57.0 t 0.4 (3) * Figures in parentheses are equivalent mg I - ' of infusion. estimated to be about 2-5 mg. However, individual intakes will vary significantly depending upon preferences for certain types of food/drink. Examples of foods with naturally high concent- rations of aluminium (Table 1) show clearly that the above mean daily intake could easily be exceeded by consuming just 100 g of soya mince followed by two cups of tea.Foods prepared from ingredients with permitted aluminium addi- tives, e.g., acid aluminium phosphate leavening agents and aluminosilicate anti-caking agents, provide even higher intakes. Gross con tamination of foodsbeverages during processing, storage or cooking is easily demonstrated. For example 100 g of rhubarb cooked in an aluminium saucepan can leach 8.5 mg of aluminium. Much lower levels of contamination which may be of greater importance to total dietary intake of aluminium are seen in some infant feeds. Human breast milk contains only 3- 10 pg I-' of aluminium but storage in glass bottles can easily double this value because of aluminium leached from the container.Some milk powders provide some 100-200 pg d-', i.e., up to 10 times that provided from breast milk. Infants being fed soya milk products can have even higher intakes of aluminium, more than 1000 pg d-'. Children on weaning diets will also have a variable intake of aluminium depending upon the purchased product. The data in Table 2 show that the products from 'Manufacturer C' provide more than 10 times the aluminium of the products of the other manufacturers. It is possible that roller drying rather than spray drying has caused the increased aluminium concentrations. It is apparent from the above discussions that daily dietary intakes of aluminium vary over a wide concentration range.For babies the intakes could easily range from <10 to >lo00 pg d- '; for adults the range could be <lo00 to > 10 000 pg d-'. In extreme cases when consumed foods such as cakes, flans, etc., are prepared from ingredients containing permitted aluminium additives, i. e., acid aluminium phosphate leavening agents and aluminosilicate anti-caking agents, the daily intake could exceed 100000 pg. These widely varying total daily intakes give n o guide to the amount of aluminium taken up during digestion and that subsequently absorbed into the body's circulation. Table 2 Aluminium in infant foods Aluminium content/mg kg-' Manufacturer Breakfasts Dinners Desserts A NA* 0.5 k 0.08 (3) 1.1 k 0.14 (3) 1.8 k 0.03 (3) 1.3 t 0.07 (3) 0.2 t 0.01 ( 3 ) B 1.8 t 0.12 (2) C 15.0 2 0.8 (2) 9.7 t 0 (2) 1.5 * 0.01 (2) NA NA 14.5 k 0.9 ( 3 ) 14.4 k 0 (2) NA 18.0 f 0.1 ( 3 ) * NA = Not available.Table 3 beverages Protocol for studying bioavailability of aluminium in foods or Day Time Action 1 20.00 Commence fast 2 - Record time first urine 08.50 Blood Urine 09.00 Drink/eat SO0 ml/g food 09.30 Blood 10.00 Blood Urine 10.30 Blood Urine 11 .OO Blood Urine 12.00 Blood Urine 12.05 Coffee and cakes Bioavailability of Aluminium from Foods and Beverages Koch et u Z . ~ measured the urinary excretion of aluminium by healthy adults who drank either tea, coffee or water; 300 ml four times per day with meals. The concentrations of alumi- nium in urine ranged from 60 to 100 pg I-' when drinking tea and from 25 to 40 pg I-' when drinking either coffee or water.Although these values are higher than one finds in the UK (less than 10 pg I-' urine) they show clearly that some of the high aluminium present in tea is absorbed into the circulation. An elegant study by Slanina et u Z . ~ showed that citric acid, taken as 200 ml of lemon juice twice daily, increased significantly the concentrations of aluminium in whole blood of a group of healthy adults consuming normal diet. When the volunteers consumed 232 mg of AI(OH)3 twice daily in addition to their normal diets a small increase in blood aluminium was noted but this was significantly enhanced when the lemon juice was also taken. These two studies show that the bioavailability of aluminium varies with the type of foodbeverage and with the presence of species such as citrate which can complex with aluminium and facilitate its membrane translocation.Sieniawska' has been studying the relative bioavailability of aluminium from commonly purchased UK fooddbeverages for healthy adults by measuring the temporal changes in alumi- nium concentrations in blood plasma and in urine following measured oral intakes. The protocol is outlined in Table 3. The *0° I h 8o t I I I I 1 I I 30 60 90 120 150 180 Time after intake/min Fig. 3 Temporal changes in plasma aluminium following oral intake of 500 g foodjdrink. A, soya milk (435 pg Al); B , tea and orange juice (365 pg Al); C, tea (580 pg Al); D, cows' milk ( 5 pg Al); E, water (1 pg Al)ANALYTICAL PROCEEDINGS, SEPTEMBER 1993, VOL 30 The increase in urinary aluminium excretion following consumption of 500 ml of tea (Fig.4) was further enhanced by drinking orange juice (250 ml) followed by tea (250 ml) even though the aluminium intake was reduced from 580 to 365 pg. These observations confirm the increased absorption of aluminium in the presence of citrate. It should be noted that, as for the changes in plasma aluminium, the levels of aluminium in urine of all subjects had returned to the basal values by 3 h after ingestion. Despite the differences in individual responses these studies allow some assessment of the bioavailability of aluminium and are currently being applied to a wide range of UK foods and beverages. 360 7 000 800 I s .- 5 600 - .- - $ m a -5 400 C a 0, m .- 6 200 100 0 60 120 180 Time after intake/min Fig.4 of 500 g food/drink. A, B, C, D, E as in Fig. 3 Temporal changes in urinary aluminium following oral intake results of some studies are given for: fruit juices, milks and tea, with and without orange juice (Figs. 3 and 4). Because of the differences in individual plasma or urine aluminium levels the data are shown as mean percentage changes in aluminium concentrations for the subjects as a function of time. However, none of the individual plasma aluminium levels exceeded 10 pg I-' and none of the urine samples contained more than 20 pg I-' of aluminium. There were significant increases in plasma aluminium levels at between 30 and 90 min after drinking soya milk, tea and tea plus orange juice (Fig. 3). The very high peak in plasma aluminium 60 min after drinking soya milk but not cows' milk has clear implications for increased aluminium uptake and intake by children drinking soya milk products.It should be noted that the very small decrease in plasma aluminium after drinking mineral water with only <3 pg I-' aluminium (Fig. 3) probably reflects an in vivo dilution of blood plasma. Further- more, for all subjects the plasma aluminium levels had decreased back to the baseline value by 3 h after ingestion of the food/drink. Conclusion It has been shown that a wide range of aluminium concen- trations are present in commonly available UK foods and beverages. The relative bioavailability of aluminium from these foods varies widely as do the uptakes by individual adults. Both parameters require further study to assess the significance for health of the levels of aluminium in foods. One common feature of the bioavailability response curves is that in all cases where there had been an increase in either plasma or urine aluminium concentrations, there followed a decrease to the basal value by 3 h after ingestion. Although this rapid clearance is to be expected for healthy adults with normal renal function it is reassuring to observe it. These studies formed part of research projects funded by the Ministry of Agriculture, Fisheries and Food. References Martyn. C. N., Barker, D. J. P., Osmond, C., Harris, E. C., Edwardson, J. A., and Lacey, R. F., Lancet, 1989, i, 59. Delves, H. T., Suchak, B., and Fellows, C. S., in Aluminium in Food and the Environment, eds. Massey, R. C., and Taylor, D., Royal Society of Chemistry, London, 1989, pp. 52-67. Koch, K. R, Bruno Pouget, M. A., de Villiers, S., and Monteagudo, F., Nature (London), 1988, 333, 122. Slanina, P., Frech, W., Ekstrom, L. G., Loof, L., Slorach, S., and Cedergreen, A., Clin. Chem., Winston-Salem NC, 1986,32, 539. Sieniawska, C., M.Phil. Thesis, University of Southampton, 1993.

ISSN:0144-557X    

DOI:10.1039/AP9933000358

出版商:RSC    

年代:1993

数据来源: RSC

摘要:

ANALYTICAL PROCEEDINGS, SEPTEMBER 1993, VOL 30 361 Short Papers in Pharmaceutical Analysis The following are summaries of eight of the papers presented at a Meeting of the Joint Pharmaceutical Analysis Group held on October 15th, 1992, in the Royal Pharmaceutical Society, London SEI. Analytical Rationalization Chris J. Goodwin Smith Kline Beecham Pharmaceuticals, Clarendon Road, Worthing, West Sussex BN 14 8QH From the time a new pharmaceutical product is discovered, its journey through to the market place can be as long as 15 years. During this time the drug substance will pass through many stages of development including laboratory and semi-scale synthesis, pilot plant scale-up, efficacy and toxicology testing, clinical trials and finally full-scale production. During this time, knowledge of the chemical process will grow considerably.Opportunities to change the route of manufacture may well give rise to novel potential impurities. The analytical systems applied during this time will also evolve. These often become more complex until a step change occurs to rationalize them. This may take place when a product is relocated to another site and re-registration becomes necessary. During scale-up and process optimization a very large number of samples are analysed. The immediate reward for simplification of the analytical regime is considerable. In financial terms there will be benefits for many years at the production site; and the improved analytical lead times aid plant and development process control and project progress, speeds up the development progress, and reduces the time taken for the product to reach the market place.The analytical rationalization process can be demonstrated using as examples the analytical system for a new antiviral drug called penciclovir. Penciclovir is the purine derivative of I used for the treatment of various herpes virus infections including Varicella Zoster, commonly known as shingles. It acts on the process of DNA replication in virally infected cells only. Penciclovir 0 A, B and C which would be very time consuming and, with the large number of samples generated during process optimiz- ation, impractical. For example, to run a full impurity profile of 15 batches, 3 days labour and instrument usage would be required. It should be remembered at this point that the existing method evolved with the process and that all the potential impurities were not known in the early stages of development.It would be impossible to develop a method at the start to separate all the impurities eventually known in the fully developed process. A gradient HPLC method has been successfully developed which achieves baseline resolution of 16 potential impurities in a single run of 60 rnin with a 10 min equilibration time (Fig. 1) LOH 9-(4-Hydroxy-3-hydroxymethylbutyl)guanine (BRL 39123) I When the development of this product was expanded, the established existing methodology for product impurity profil- ing which had been developed along with the process, consisted of three isocratic high-performance liquid chromatography (HPLC) methods.Each sample would be analysed on systems :-- BRL 42817 F? \ 5 % t- / BRL 46970 1 BRL 391231 $ p F BRL 42377 =. 0 - BRL 48440 BRL 4601 3 2 5. EL BRL 451 39 %. BRL 39913 BRL 46969 BRL 46771 BRL 46979 Fig. 1 Chromatogram of a BRL 39123 batch spiked with potential impurities at levels of 0.1%. The following HPLC conditions were used: Column: SPHERISORB ODS 2 (250 x 4.6 mm i.d.); eluents: A, 0.1 mol dmP3 sodium dihydrogenorthophosphate pH 3.7; B, 79% 0.1 mol dm-3 sodium dihydrogenorthophosphate pH 3.7,21% HPLC grade acetonitrile; wavelength 254 nm; flow 2 cm3 min-'. Gradient: 0-5 min, 100% A (isocratic); 5-35 rnin to 65% A and 35% B (linear); 35-50 rnin to 100% B (linear); 50-60 rnin to 100% B (isocratic); 60-65 mins to 100% A (linear); 65-70 min remaining at 100% (equilibration period)362 ANALYTICAL PROCEEDINGS, SEPTEMBER 1993, VOL 30 The method was developed using linear gradients to allow easy transfer between sites and types of equipment.The potential impurities involved in the critical separation are shown in Fig. 2. There were two areas of critical separation. The first critical separation was achieved using: (a), careful control of eluent pH (at 3.7 to ensure the isomer BRL 46970 eluted before penciclavir I); (b), the introduction of a 5 rnin run at the start with no organic modifier; and also (c) by the use of acetonitrile and 0.1 mol dmP3 sodium dihydrogenorthophos- phate, which sharpened the peaks in comparison with the existing method that used a 0.05 mol dm-3 phosphate-meth- anol eluent. The second critical separation between BRL 39206, BRL 42222, BRL 56225 and BRL 56293 was achieved only with very 0 0 BRL 391 23 careful control of the acetonitrile content; hence the gradient is very gentle from 5 to 35 min (065% eluent B).The gradient HPLC impurity method has been successfully used in a routine environment for 18 months. It has proved very rugged and has resulted in a 75% labour saving for the analysis of penciclovir. There are other examples of analytical rationalization in the penciclovir project. A fast liquid chromatography (LC) method was developed for one of the process intermediates where baseline resolution was achieved from the potential impurities and process reagents in a single run time of 8 min. The conditions used were as follows. Column: Jones 3 prn CI8 (50 x 4.6 mm i.d.1 + 10 mm guard column; eluent: 67% 0.05 mol dm-3 sodium dihydrogenorthophosphate; 33% HPLC BRL 42377 HO HO OH BRL 39206 b HO OH BRL 46970 OH 0 BRL 42222 I HO h CI BRL 56225 BRL 56293 Fig.2 Potential impurities involved in critical separationsANALYTICAL PROCEEDINGS, SEPTEMBER 1993, VOL 30 grade acetonitrile; flow: 2.0 cm3 min-l; wavelength: 257 mm; typical main peak retention time 6.0 min. This method has proved to be very rugged in routine use and replaced a gas chromatography (GC) method with a 29 min run time (including reconditioning). A modified version is also used for impurity profiling. A further example of analytical rationalization was the replacement of a normal-phase HPLC method with a more rugged reversed-phase system.The side chain intermediate was 363 baseline-resolved from its isomer. The reversed-phase method was found to be more reproducible and easier to operate. In companies where a significant number of samples are being assessed analytical rationalization is very beneficial. When the production of a new product is scaled up and the testing becomes more routine, new more streamlined analyti- cal techniques are very often required to meet different demands, not only of analytical lead times but also the type of environment in which the analysis is carried out. Quantitative Determination of Sumatriptan by Capillary Electrophoresis K. D. Altria and S. D. Filbey Pharmaceutical Analysis, Glaxo Group Research, Park Road, Ware, Hertfordshire SG 12 ODP The determination of drug content in formulated pharmaceut- ical products is performed predominantly by high-performance liquid chromatography (HPLC) as this can offer a fast and automated determination.Capillary electrophoresis (CE) is a complementary technique that can achieve equally rapid, high- resolution separation. CE has been investigated for a number of applications within pharmaceutical analysis. 1-3 However, there has been little emphasis on demonstrating that these methods are capable of routinely determining the drug content of formulated pharmaceutical products. CE has been employed for the quantitative determination of sumatriptan [3- (2-dimethylaminoethyl)-5-( methylaminosulfonylmethyl)in- dole] levels in subcutaneous injection solutions. Sumatriptan is marketed for the treatment of migraine.Results generated by both CE and HPLC for four batches of sumatriptan injection solutions compared well. The CE method gave good per- formance in terms of selectivity, precision, linearity and repeatability of both injection and analysis. Theory In capillary zone electrophoresis separations are achieved by the application of high voltages; ionic species migrate electro- phoretically in an applied electric field. Ions are separated according to their mobility in field solution, mobility being dependent upon the charge-to-size ratio of the ion. Separation of species with ionizable groups can be optimized largely by varying pH. Experimental Chemicals were obtained from Aldrich Ltd. (Gillingham, Dorset, UK), and water was obtained from a Millipore Q system (Watford, Hertfordshire, UK).The quantitative work was performed on a Waters Quantum 4000 CE instrument (Watford, Hertfordshire, UK) which was connected to a Hewlett-Packard data collection system (Bracknell, Berkshire, UK). Comparative separations were achieved on a P/ACE 2000 CE instrument (Beckman, Palo Alto, CA, USA). The fused silica capillaries used in this study were purchased from both Waters and Beckman. An internal standard was employed since this had been shown to improve the repeatability of injection in CE.4 A precursor to ranitidine5 was selected (chemical structures are given in Fig. 1) as this was known to migrate before any sumatriptan related compounds. Sample and standard solu- tions were prepared to give a final aqueous concentration of 0.5 mg cm-3 of both internal standard and sumatriptan.Results CE was used to quantify levels of sumatriptan in injection solutions, the samples selected for this purpose contained sumatriptan formulated at 12 mg cm-3 in isotonic saline solution. Currently HPLC methods are employed for the determination. Method Development Practical guidelines to the method development options for CE of pharmaceuticals have recently been published by McLaugh- lin et al. For this particular separation a low pH (pH 2.3) was selected to ensure protonation of both the analyte and related impurities. The CE separation of a synthetic test mixture of sumatrip- tan, a dimeric related impurity, and the internal standards is shown in Fig. 2. Precision of Injection Relative standard deviations (RSDs) of less than 2% can be routinely obtained for peak areas on commercial instruments.By employing an internal standard, variability can be reduced still further with typical RSDs of below 1% being ~ b t a i n e d . ~ Replicate electropherograms for sample solutions are shown in Fig. 3; these separations indicate the consistent impurity profiles obtained throughout these studies. Both a calibration and sample solution were injected 5 times and acceptable precison for peak area and peak area ratios was obtained (Table 1). Migration time variation using the CE method, measured in H Internal standard ‘0’ Fig. 1 Chemical structures of sumatriptan and internal standard364 ANALYTICAL PROCEEDINGS, SEPTEMBER 1993, VOL 30 t 17.00 I* 13.00 1 2.00 4.00 6.00 8.00 Retention ti rn e/rn i n Fig.2 CE separation of internal standard (A), sumatriptan related dimeric impurity (B) and sumatriptan (C). Separation conditions: 20.0 s hydrodynamic sampling, +20 kV, 214 nm, 75 ym X 60 cm fused silica capillary, sodium dihydrogenorthophosphate (25 mmol dm-3, pH 2.3 with concentrated phosphoric acid) 18.40 - 18.20 - 18.00 17.80 - - 17.40 17.20 ' 17.001 I I , 1 18.40 18.20 18.00 17.80 17.60 17.40 17.20 17.00 1 I , , 3.00 5.00 7.00 9.00 Retention ti me/rn i nutes Fig. 3 see caption to Fig. 2 CE separation of sample solutions. For separation conditions Table 1 Precision of injection peak area (number of injections = 5) RSD(%) Standard Sample solution solution Sumatriptan 0.7 0.7 IS 0.5 0.1 Peak area ratio 0.5 0.8 terms of migration time and relative migration time, was typically less than 1% RSD.Sensitivity A limit of detection of 0.1% m/m of the sumatriptan loading (0.5 mg cmP3) was obtained (signal-to-noise ratio greater than 3). A similar detection limit of 0.1% aredarea for salicylamide impurities by CE has been reported.' This limit of detection of equivalent to 500 ppb sumatriptan in solution. Linearity The linearity of detector response between 0 and 150% of the sample concentration (0.5 mg cm-3 sumatriptan) was estab- lished. The data showed good linearity for both sumatriptan peak area and peak area ratio (correlation coefficients 0.9992 and 0.9993, respectively). Repeatability of Analysis The day-to-day variability of analysis for sumatriptan content was established by conducting two separate sets of analyses on two separate occasions.Similar results for each sample set were obtained on each occasion and these were in agreement with those achieved by HPLC (Table 2). Each analysis set comprised testing of on-going stability batches which had been stored at various conditions of heat and humidity. Table 2 Repeatability of results day-to-day Analysis set 1 - Sumatriptan content/mg cmP3 CE results HPLC Sample batch 1 Day 1 Day2 Mean Condition 1 11.9 11.9 11.9 11.8 Condition 2 11.8 11.6 11.7 11.7 Condition 3 11.7 11.7 11.7 11.7 Analysis set 2- Sumatriptan content/mg cmp3 CE results HPLC Sample batch 2 Day 1 Day 2 Mean Condition 1 11.9 11.6 11.8 11.6 Condition 2 11.7 11.6 11.7 11.7 Table 3 Sumatriptan content by CE and HPLC Sumatriptan content/mg cm-3 Sample Condition 1 (aliquot 1) Condition 1 (aliquot 2) Condition 2 (aliquot 1) Condition 2 (aliquot 2) Condition 1 (aliquot 1) Condition 1 (aliquot 2) Condition 2 (aliquot 1) Condition 2 (aliquot 2) Condition 1 (aliquot 1) Condition 1 (aliquot 2) Condition 2 (aliquot 1) Condition 2 (aliquot 2) Batch 2- Batch 3- Batch 4 - CE HPLC 11.5 11.6 11.6 11.6 11.6 11.7 11.6 11.7 11.7 11.8 11.8 11.8 11.6 11.7 11.6 11.7 11.7 11.8 11.8 11.8 11.7 11.7 11.6 11.7ANALYTICAL PROCEEDINGS, SEPTEMBER 1993, VOL 30 365 Repeatability of Separation In order to assess the ruggedness of the method the separation was performed on an alternative CE instrument (Beckman P/ACE 2000) using a capillary from a different supplier. The separation achieved showed an indentical migration order to that achieved on the earlier instrument and capillary.Cross-correlation Between Sumatriptan Content Results by CE and HPLC Currently HPLC is employed for the determination of sumatriptan contents7 Sumatriptan content was determined by CE for three stability batches of sumatriptan injections (12 mg ~ m - ~ ) using external standardization. The comparison of the results obtained by CE and HPLC is shown in Table 3. Two aliquots were taken from each sample, and each aliquot was analysed in duplicate. The results are the mean of the two injections of each aliquot, good correlation was obtained. Conclusions A CE method has been employed for the determination of sumatriptan. The method gave good performance in terms of selectivity, precision, linearity and repeatability.The good cross-correlation of CE and HPLC results suggests that CE could be employed for this and other quantitative analysis. References 1 Swartz, M. E., J. Liq. Chromatogr., 1991, 14, 923. 2 Altria, K. D., and Smith, N. W., J. Chromatogr., 1991,538,506. 3 Ackermans, M. T., Beckers, J. L., Everaerts, F. M., and Seelen, I. G. J. A., J. Chromatogr., 1992, 590, 341. 4 Dose, E. V., and Guiochon, G. A., Anal. Chern., 1991,63,1154. 5 Dawson, J . , Richards, D. A., Stable, R., Dixon, G. T., and Cockel. R., J. Clin. Hosp. Pharm., 1983, 8, 1. 6 McLaughlin, G. M., Nolan, J. A., Lindahl, J. L., Morrison, J. A., and Bronzert, T. J., J. Liq. Chromatogr., 1992, 15. 961. 7 Oxford, J., and Lant, M. S.. J. Chromatogr., 1989, 496, 137. Enantiomeric Separation of Ciprofibrate and Analogues Using a Cellulose-based Chiral Stationary Phase A.Scott, P. R. Vojvodic and N. H. Anderson Sterling Winthrop Pharmaceuticals Research Division, Willowbum Avenue, Alnwick, Northumberland NE66 2JH B. J. Clark Pharmaceutical Chemistry, School of Pharmacy, University of Bradford, Bradford, West Yorkshire BD7 IDP It is known that individual enantiomers of chiral drugs can possess different potencies because of differences in pharmaco- dynamics, pharmacokinetic behaviour or metabolism. For new drug entities, unless the use of a racemate can be justified, major regulatory authorities require the development of a single enantiomer. The development of chiral stationary phases (CSPs) for gas-liquid chromatography (GLC) and high- performance liquid chromatography (HPLC) has greatly facilitated the determination of the enantiomeric purity of drugs.Ciprofibrate {2-[4-(2,2-dichlorocyclopropyl)phenoxy]-2- methylpropanoic acid} (Fig. l), is a hypolipidaemic agent, currently marketed as a racemic mixture. For analytical purposes an enantioselective HPLC method was required.' A review of the literature on chiral separations revealed that cellulose triacetate had been successfully used to separate enantiomers which did not have a hydrogen bonding capability close to the chiral centre and therefore this phase was selected as a starting point for this programme.2 It was also proposed to gain an improved understanding of the chiral recognition sites of microcrystalline cellulose triacetate, by extending the examination to a number of the analogues of ciprofibrate.Experimental Apparatus Chromatographic experiments were carried out using an HP 1090 Series 11 LC system and workstation (Hewlett-Packard, 0 Fort Collins, CO, USA). The column used was a Chiralcel CA- 1 (Daicel Corporation, Japan), 250 x 4.6 mm i.d. Conditions Column: Mobile phase: Temperature : Flow rate: Injection volume: Ultraviolet (UV) detection: Chiralcel CA-1, 250 X 4.6 mm i.d. 90 + 10 v/v ethanol-water. The mobile phase was filtered and de- gassed prior to use. 25 "C 0.5 cm3 min-' 10 mm3 of 1 mg cm-3 solution h 236 nm Results and Discussion Microcrystalline cellulose triacetate is prepared by the hetero- geneous acetylation of microcrystalline cellulose. As a CSP, it can have a broad applicability, it is compatible with reversed- phase solvents and it is capable of accepting a high analyte loading, which is useful in preparative and semi-preparative work.The mobile phase and temperature parameters which were initially used were based on those found to give the successful separation of ciprofibrate methyl ester (b, Fig. 2). The chromatographic conditions used were 90 + 10 v/v ethanol- water at 0.5 cm3 min-', 25 "C, UV detection (A 236 nm) with a 10 mm3 injection volume. Ciprofibrate was derivatized to the methyl ester prior to chromatography, owing to the poor retention on the cellulose triacetate column of the parent compound. This is due to the presence of the carboxylic acid group so analogues having this function were also derivatized to the methyl ester. Analogues which Result from Variations in the C yclopropane Ring When both the chlorine atoms of ciprofibrate are replaced by either fluorine or bromine, baseline resolution of the enantio- Fig.1 Structure of ciprofibrate366 0 ANALYTICAL PROCEEDINGS, SEPTEMBER 1993, VOL 30 torsion angle between the phenyl ring and cyclopropane ring for the ethyl compound h. a R’ = Br, R2 = H, R3 = Me, R4 = H b R’ = CI, R2 = H, R3 = Me, R4 = H c R’ = F, R2 = H, R3 = Me, R4 = H d R’ = Me, R2 = H, R3 = Et, R4 = H e R’ = CI, R2 = Me, R3 = Me, R4 = H f R’ = F, R2 = Me, R3 = Me, R4 = H g R’ = Br, R2 = Me, R3 = Me, R4 = H h R’ = CI, R2 = Et, R3 = Me, R4 = H i R’ = CI, R2 = H, R3 = Et, R4 = H j R’ = CI, R2 = H, R3 = Et, R4 = CI k R’ = F, R2 = H, R3 = Me, R4 = CI P I p R 5 = H q R5 = OMe r R5 = OCOMe s R5 = NH2 Fig.2 Structures of ciprofibrate analogues Table 1 Resolution and selectivity values Sample a b d e f g h i k P Q r C .i S Retention time/ min PeakA Peak B 13.51 17.20 12.07 20.15 11.58 14.78 6.89 9.56 10.37 9.58 10.70 8.68 10.17 11.17 13.42 12.01 12.34 15.16 14.00 17.29 17.99 20.68 23.80 Rs 0.66 1.62 0.87 0.33 0.29 0.70 0.80 0.56 (r(A,B) k’(A) 1.39 2.38 2.00 2.02 1.43 1.89 0.72 1.14 1.39 1.39 1.68 1.17 1.16 1.54 2.35 2.02 1.33 2.09 1.33 2.50 3.50 1.19 4.17 k‘@) 3.30 4.04 2.70 1.59 1.79 2.79 3.32 4.95 mers was still achieved (Table 1). However, the dichloro analogue gave the best resolution. As regards retention, this increased according to Br>Cl>F (a, b, and c, Fig. 2). In the case of the ethyl ester analogue, d, in which methyl groups replace the chlorine atoms, poor resolution and retention were obtained.This is considered to be due to an electronic and/or lipophilicity effect as the chlorine atom and methyl group are similar in size. However, when there is substitution of a methyl group for the hydrogen atom at the chiral centre, resolution of the dichloro analogue e was achieved but this was not the case with the fluoro and bromo analogues f and g, and this result was unexpected. Extension of this to an ethyl (h), rather than a methyl (e) group at the chiral centre, resulted in loss of resolution which is possibly due to the steric hindrance of the large sized ethyl group. This may result from the greater Comparison of Methyl and Ethyl Esters of Ciprofibrate Both the methyl and ethyl esters of ciprofibrate (b and i) were resolved on microcrystalline cellulose triacetate, with the methyl ester being more strongly retained.This retention pattern is the opposite of that noted on a reversed-phase column and may be due to the possible polar character of the stationary phase. In addition, it was noted that compound j, a ring substituted ethyl ester, was not resolved. Phenyl Ring Substitution of Ciprofibrate Where the ciprofibrate phenyl ring is modified, such as with 3- chloro ring substitution k, enantiomeric resolution was not obtained although the analogues were retained on the column. Since the aromatic moiety is adjacent to the chiral centre, it would be expected to play a role in chiral recognition. The lack of resolution may be due to the steric and electronegative properties of the 3-chloro substituent.Synthetic Precursors of Ciprofibrate Compound p is a relatively small, lipophilic molecule, and was well retained and well resolved. Compound q was also resolved, but compound r, an ester, was not; interestingly it was more strongly retained than the former analogues. It is possible that a dipolar interaction between the ester linkage and the cellulosic stationary phase prevents resolution of r. With the 1-amino precursor s , retention was greater than any other analogue tested and in addition it was partially resolved. This may be a result of a dipolar attraction between the negative nitrogen and the ester linkage of the stationary phase. This evidence of differences in behaviour between the acetate and the amino compounds indicates that a spatial relationship between the dipole of the group at the 1-position of the phenyl ring and the rest of the molecule can affect resolution of the enantiomers.Conclusions The results illustrate that resolution on microcrystalline cellulose triacetate can be achieved with a range of modified structures from the base of the ciprofibrate model when carried out under constant chromatographic conditions. However, it is clear that certain chemical structure rules, for recognition, operate. It is suspected that no simple recognition process is occurring at a single site; rather that a number of differing chiral recognition sites are present on the microcrystalline cellulose triacetate, as has been previously reported by R i ~ z i ~ - ~ and Francotte .6,7 In order to give additonal corroboration of the analyte/stationary phase interactions, a further investi- gation is being completed to establish the dependence of retention and resolution of the enantiomers through the composition of the mobile phase.References 1 Anderson, N. H., Johnston, D., and Vojvodic, P. R., J. Pharm. Biomed. Anal., 1992, 10, 501. 2 Wainer, I. W., A Practical Guide to the Selection and Use of HPLC Chiral Stationary Phases, J. T. Baker Chemical Co., Phillipsburg, NJ, USA, 1988. 3 Rizzi, A. M., J. Chromatogr., 1989. 478, 71. 4 Rizzi, A. M., J. Chromatogr., 1989, 478, 87. 5 Rizzi, A. M., J. Chromatogr., 1989, 478, 101. 6 Francotte, E., Wolf, R. M.., Lohmann, D., and Mueler, R., J . Chromatogr., 1985, 347, 25.7 Francotte, E., and Wolf, R. M., Chirality, 1990, 2, 16.ANALYTICAL PROCEEDINGS, SEPTEMBER 1993, VOL 30 Inorganic Salts as Modifiers in the High-performance Liquid Chromatography Mobile Phase Used to Chromatograph Atenolol 367 Alison E. Bretnall and Thomas Cowen Bristol-Mvers Sauibb Pharmaceutical Research Institute, International Development Laboratories, Reeds Lane, Moreton, herseyside L46 70W Ionic counterions are used extensively in reversed-phase high- performance liquid chromatography (HPLC) to effect a chromatographic separation. They are often used to obtain a required specificity or to improve the efficiency of a particular separation. Some of the counterions most widely used to effect an ion-pair complex are the alkylsulfonic acids, e.g., heptansul- fonic acid.In our experience, there are several disadvantages to using such ion-pair reagents, for instance long equilibration times, permanent modification of the chromatographic column and problems associated with mobile phase recycling. Also the chromatography can be poor with tailing peaks. These disadvantages may be overcome by using inorganic salts as modifiers in the mobile phase. An example of this is a recently developed procedure for the analysis of atenolol { (4-(2-hydroxy-3-isopropylaminopro- poxy)phenyl]acetamide} (Fig. 1), a synthetic beta-selective adrenoreceptor blocking agent, which is a relatively polar hydrophilic compound with basic character. Many of the published analytical methods'-' for atenolol utilize ion-pair reagents or alkylammonium salts.In our experience, however, the chromatography with these methods is generally poor, with tailing peaks and short column life. In our laboratory atenolol has been chromatographed using a reversed-phase p-Bondapak phenyl column with a mobile phase containing potassium chloride as an inorganic modifier. This paper reviews the method, the effects of alternative columns and of varying the composition of the mobile phase. Atenolol Assay Method Chromatographic Parameters A 300 x 3.9 mm i.d. stainless steel column packed with p- Bondapak phenyl (Waters Associates, Millipore, Peter- borough) was used at 30 "C with a mobile phase containing methanol-1% ( d v ) aqueous potasssium chloride (1 + 3 v/v). The flow rate was 1.0 cm3 min-' and the detection by ultraviolet (UV) absorption at a wavelength of 240 nm.Chromatography A solution of atenolol at a concentration of 1 mg cmP3 was prepared in methanol-water (1 + 1 v/v) and 20 mm3 were injected onto the HPLC system. Under these chromatographic conditions the atenolol eluted at 5.2 min as a sharp peak with a N I H Me Fig. 1 Structure of atenolol tailing factor of 1.6. The method was successfully validated for precision, accuracy, specificity and linearity of response. Atenolol possesses a number of known impurities and degradants which are possibly present in the bulk drug material and may therefore be found in the finished product. Of these six known compounds can be resolved from atenolol under the conditions of the assay (Table 1). The specificity of this method was only validated using 1% ( d v ) aqueous potassium chloride in the mobile phase.Variations in Mobile Phase Composition and Column As inorganic salts have been used previously for methods in our laboratories, an investigation into the effects of varying the mobile phase composition and the reversed-phase HPLC column was undertaken. Variation of the Concentration of Potassium Chloride in the Mobile Phase A range of mobile phases containing 0.01, 0.1,0.5, 1.0,2.0 and 4.0% ( d v ) aqueous potassium chloride-methanol(1 + 3 v/v) were prepared and with the chromatographic parameters described previously, used to chromatograph the atenolol solution (Fig. 2). The retention time of the atenolol peak was consistent at 5.5 min for 0.5-4.0% (m/v) aqueous potassium chloride; however, the tailing factor decreased from 2.1 to 1.2, respectively.For the lower concentrations of 0.1 and 0.01% ( d v ) aqueous potassium chloride, the retention time increased from 7 to 15 min and the peak tailing increased. (Tailing factor greater than 3.0 for both concentrations.) Effect of the Cationic Chloride Salt in the Aqueous Component of the Mobile Phase A range of mobile phases were prepared containing 1% ( d v ) aqueous chloride salt-methanol (1 + 3 v/v), where the cation was zinc, potassium, rubidium, sodium, magnesium or calcium. Atenolol was chromatographed using the above range of mobile phases (Fig. 3) and the conditions described in the chromatographic parameters. The retention time of the atenolol peak was consistent at 5.5 min whereas the tailing factor varied.The mobile phases containing zinc, potassium and rubidium all gave peaks with tailing factors of less than 2.0. Those containing sodium, magnesium and calcium gave peaks with tailing factors greater than 2.0. Table 1 Retention times of atenolol and six known impurities Retention time/min Atenolol 5.2 (4-Hydroxypheny1)acetamide 4.6 Bis-[3-(4'-carbamoylmet hylphenoxy)-2-hydroxy- prop yllisoprop ylamine 16.0 Fumaric acid 2.7 4-(2-Hydroxy-3-isopropylaminopropoxy)- phenylacectic acid 6.1 4-( 2-Hydroxy-3-ch1oropropoxy)phenylace tamide 13.2 [4-(2,3-Epoxypropoxy)phenyl]acetamide 10.8368 ANALYTICAL PROCEEDINGS, SEPTEMBER 1993, VOL 30 300 > E % 200 2! 8 100 0" 1 0 P +- al +- 0 I I 1 I I I I I I 1 1 1 2 4 6 8 10 12 14 16 18 20 22 24 E I ut i on ti m elm in Fig.2 Chromatogram of atenolol (1 mg cmP3) using mobile phase containing A , 4.0; B, 2.0; C, 1.0; D, 0.5; E, 0.1; and F, 0.01% m/v aqueous potassium chloride-methanol (1 + 3 v/v) 800 700 $ 600 500 2 400 300 1 Q fn L 0 +- 0" 200 100 0 1 2 3 4 5 6 7 8 9 Elution time/min Fig. 3 Chromatogram of atenolol (1 mg ~ r n - ~ ) using mobile phase containing 1% m/v aqueous chloride salt-methanol (1 + 3 v/v) where the chloride salt was: A, ZnC1,; B, KCI; C, RbCl; D, NaCl; E, MgCl,; and F, CaCI2 There was also an increase in the intensity of the UV response for the atenolol with zinc and calcium. However, the use of calcium is not recommended as a rapid deterioration of the chromatographic performance was observed. Effect of the Anionic Potassium Salt in the Aqueous Component of the Mobile Phase A range of mobile phases were prepared containing 1% ( d v ) concentration aqueous potassium bromide, potassium phos- phate and potassium sulfate solution, respectively, in methanol (1 + 3 v/v).Each was used to chromatograph the atenolol solution (1 mg cmW3) using the chromatographic parameters described previously. The retention time for the atenolol peak was between 4.2 and 5.2 min and the tailing factor was 1.5. Effect of the Organic Modifier A mobile phase containing 1% ( d v ) aqueous potassium chloride-acetonitrile (1 + 3 v/v) was used to chromatograph the atenolol solution (1 mg ~ m - ~ ) . On comparison with the mobile phase containing methanol, a significant loss in chroma- tography was observed. The retention time was reduced to 3.5 min and the peak showed fronting and tailing.Alternative HPLC Columns A mobile phase was prepared containing 1% ( d v ) aqueous potassium chloride-methanol (1 + 3 v/v) and three columns Table 2 Retention times and peak shapes of atenolol on alternative HPLC columns Retention Column t ime/mi n Peak shape p-Bondapak CIS 4.5 Sharp peak, tailing factor 1.7 300 x 3.9 mm i.d. (Waters) Hypersil BDS CI8 5 pm 150 x 4.6 mm i.d. (Shandon) 8 x 100mm (Waters) 2.5 Sharp peak but with significant tailing Silica radial pack 10 pm 10.5 Significant fronting and tailingANALYTICAL PROCEEDINGS, SEPTEMBER 1993, VOL 30 369 were used to chromatograph the atenolol solution (Table 2, Fig. 4). A p-Bondapak CIS column gave comparable chroma- tography to that obtained with the p-Bondapak phenyl used previously, whereas a Hypersil base-deactivated silica column which is claimed to be specially designed for the chroma- tography of basic compounds, elutes a peak with significant '0° 1 b 300 n loo 0 k 2 1 2 3 4 B L I I 1 I I 1 I I 1 1 5 6 7 8 9 10 11 12 13 14 15 E I utio n ti m e/m i n Fig.4 Chromatogram of atenolol (1 mg using columns, A, Hypersil BDS CI8; B, pBondapak CIS; and C, Silica radial pak with mobile phase containing 1% m/v aqueous potassium chloride- methanol (1 + 3 v/v) tailing. (It should be noted that without the inorganic modifier the atenolol showed gross peak distortion.) Chromatography was also performed on a silica packed column and gave significantly greater retention of atenolol with increased tailing. Conclusions Atenolol has been chromatographed successfully using a reversed-phase HPLC system utilizing potassium chloride as inorganic modifier, and fully validated as a stability indicating assay.Satisfactory chromatography has also been obtained €or atenolol using various inorganic salts as mobile phase modifiers which may be applicable to other basic compounds. The enhanced UV response for atenolol when chromato- graphed using zinc and calcium ions was considered of interest and will be investigated in the future. References Owino, E., Clark, B. J., and Fell, A. F., J . Chromatogr. Sci., 1991, 29, 4.50. Yee, Y., Rubin, R., and Blaschke, T. F., J . Chrornatogr., 1979, 171, 3.57. Miller, R. B.. J. Pharm. Biomed. Anal., 1991, 9, 849. Pawlak, Z., and Clark, B. J., J .Pharm. Biomed. Anal., 1992,10, 329. British Pharmacopoeia 1988, HM Stationery Office, London, 1988, vol. 1, p. 49 and vol. 2, p. 903. Determination of Dextromethorphan and its Metabolites in Human Urine Using Solid-phase Extraction and Reversed-phase High-performance Liquid Chromatography Rachel Howling SmithKline Beecham Consumer Brands, St. Georges Avenue, Weybridge, Surrey KT13 ODE George Hutchinson Anachem, Charles Street, Luton, Bedfordshire LU2 OEB Dextromethorphan (Dm) is an antitussive widely used in the over-the-counter (OTC) cough-cold market. In humans it is metabolized to dextrorphan (Dt), 3-hydroxymorphinan (3- OH) and 3-methoxymorphinan (3-Me0). All three of these metabolites form conjugates with glucuronic acid at the 3- hydroxy group position.This metabolism is under genetic control, co-segregating with the debrisoquine polymorphism.' Three different metabolizers can be identified, Group 1 (extensive metabolizers), Group 2 and Group 3 (poor metab- olizers).* Poor metabolizers have a Dt/Dm ratio below 1 in their urine collected for 8 h after an oral dose of Dm and make up 5-10% of the Caucasian population, whereas the group 2 metabolizers have a Dt/Dm ratio between 1 and 10, and the extensive metabolizers have a ratio above ten. Various analytical methods are available to determine Dm in human urine, including: thin-layer chromatography (TLC);3 gas chromatography (GC);2 high-performance liquid chroma- tography (HPLC) with ultraviolet (UV) d e t e ~ t i o n ; ~ and HPLC with fluorescence d e t e ~ t i o n .~ All these methods are either only comparative in the case of TLC or require time consuming sample preparation. There are also two methods published which use solid-phase extraction but one requires the extract from the cartrid e to be dried down, thus reducing the ease of automation: and the other only supports phenotype determinati~n.~ Experimental One hundred cubic millimetres of urine are pipetted into a 4 cm3 glass sample tube, to which 100 mm3 of a 55 pg cm-3 codeine solution (IS) and 1 cm3 of 2 mg cm-3 P-glucuronidase in 0.5 mol dm-3 sodium acetate (pH 5 ) solution are added. The mixture is incubated at 37 "C overni ht. cartridges are preconditioned with 1000 mm3 of acetonitrile and 1000 mm3 of water, followed by 50 mm3 of air. The 1200 mm3 of incubated urine sample and buffer are added followed by 1000 mm3 of air.The cartridge is then washed using 1000 mm3 of water and 1000 mm3 of acetonitrile, again both followed by 1000 mm3 air. The Dm and its metabolites are eluted with 1000 mm3 of 60% acetonitrile-40% 0.02 mol dm-3 NaH2P04 pH 3.6 and 1000 mm3 air into 3.5 cm3 polyethylene collection tubes. After mixing by bubbling through air, 5 mm3 of the eluted solution are injected on to the HPLC. All the above procedure is carried out by the ASPEC without any operator intervention. Chromatographic separation is achieved isocratically, on a 15 cm x 2.2 mm i.d. Spherisorb 5 pm CN analytical column fitted with a 5SCN guard column using a 45% acetonitrile-55% 0.01 mol dm-3 NaH2P04, containing 75 mm3 of orthophos- phoric acid per dm3, the mobile phase being run at Using a Gilson ASPEC 100 mg, 1 cm B Phenyl Bond Elute370 il ANALYTICAL PROCEEDINGS, SEPTEMBER 1993, VOL 30 1 OO( > E $ .0 al a 0 D I 10 Time/min 600 > E % . 0 Q) a a , ( b ) A I 1 0 10 Ti me/m i n Fig. 1 Typical chromatograms for ( a ) spiked and ( b ) blank human urine extracts. A, Codeine; B, 3-OH; C, Dt; D, 3-Me0; E, Dm 0.25 cm3 min-'. Fluorescence detection is used with an excitation wavelength of 230 nm and and emission wavelength of 312 nm. This gives the following retention times: 5.0 min codeine, 6.5 min 3-OH, 7.0 rnin Dt, 8.0 rnin 3-Meo and 9.0 min for Dm. Typical chromatograms for blank and spiked human urine extracts are as shown in Fig. 1. Calibration is camed out using six spiked urine samples and a curve obtained using unweighted linear regression.Results For the purpose of validation, 1000 mm3 of 0.5 mol dm-3 sodium acetate buffer, containing 2 mg cm-3 P-glucuronidase, are added to all samples (to simulate the in-use conditions). If the 100 mm3 of codeine, IS, is not used then it is replaced with distilled water. The limit of quantification is taken as 0.5 pg cmV3 for all four species and this is the lowest level which gave suitable accuracy and precision results. Extraction recoveries are 100% for all four species in the range 0.5-10.0 pg ~ m - ~ . Calibration graphs show correlation coefficient values, Y, >0.99 for Dt, 3-Me0 and 3-OH and >0.98 for Dm for the range of 0.5-10 pg cmV3. Within batch precision gave relative standard deviations (RSDs) of <lo% for spiked samples using five different concentrations for all four species with 50% being below 5% and below 3% for samples obtained from volunteers dosed with Dm.Urine samples obtained from volunteers dosed with Dm stored at -20 "C for four weeks showed no signs of degradation. Conclusions This paper describes an accurate, precise and robust assay for the determination of Dm and its metabolites in human urine which is suitable for use in clinical studies and for the determination of p450 phenotype status. References 1 Schmid, B., Bircher, J., Preisig, R., and Kupfer, A., Clin. Pharmacol. Ther., 1985,38, 618. 2 Pfaff, G., Breigel, P., and Lamprecht, I., Znt. J. Pharm., 1983, 14, 173. 3 Guttendorf, R. J., Britto, M., Blouin, R. A., Foster, T.S., John, W., Pittman, K. A., and Wedlund, P. J., Br. J. Clin. Pharmacol., 1990, 29, 373. 4 Hilderbrand, M., Seifert, W., and Reichenberger, A., Eur. J. Clin. Pharmacol., 1989,36, 315. 5 Chen, Z. R., Somagyi, A. A., and Bochner, R., Ther. Drug. Monit., 1990, 12, 97. 6 Wenk, M., Todesco, L., Keller, B., and Follath, F., J. Pharm. Biomed. Anal., 1991, 9, 342. 7 Jacqz-Aigrain, E., Menard, Y., Popan, M., and Mathieu, H., J. Chromatogr., 1989, 495, 361.ANALYTICAL PROCEEDINGS, SEPTEMBER 1993, VOL 30 0 1 - 2 - 3 - C .- E F 5 \ - E" 10 15 20 371 CS = 0.5 Solvent front =C -cs = 0.1 ': - - R Development of a Method for the Detection of Angiotensin Converting Enzyme Inhibitors Using Electron Capture-Gas Chromatography Detection K. M. Sereda, T. C. Hardman, M. R. Dilloway and A.F. Lant Department of Clinical Pharrnacolog y and Therapeutics, Chelsea and Westminster Hospital, London SWIO 9NH Angiotensin converting enzyme (ACE) inhibitors are used in the treatment of essential hypertension and heart failure. The majority of the therapeutic compounds in this group are prodrugs, requiring activation after oral administration to exert their effect. The ACE inhibitors investigated included the active drug captopril, the prodrugs benazepril, ramipril, enalapril and perindopril, as well as the primary active metabolites of these prodrugs benazeprilat , ramiprilat , enala- prilat and perindoprilat . De-esterification of the prodrugs results in the dicarboxylic acid metabolites which, in common with the other members of the class, are extremely water soluble.ACE inhibitors were designed to mimic natural peptides and as such they are effective in relatively small doses (1-10 mg); as a result, analytical methods currently employed to detect individual compounds are varied and complex ranging from radioimmunoassay ' to gas chromatography-mass spec- trometry (GC-MS).2 It has been shown that good gas chromatographic (GC) properties can be conferred upon members of this class of dru s by derivatizing with pentafluorobenzyl bromide ( P F B - B I - ) . ~ ~ The pentafluorobenzyl group is an excellent electrophore and results in a high electron-capture detector (ECD) response to these compounds. However, the use of PFB-Br as a deriva- tizing agent is hampered by the need to add an excess of PFB- Br. The excess of reagent tends to overload the EC detector if it is not removed from the sample prior to its injection onto the column.Different methods of removing the excess of PFB-Br after derivatization which have been suggested include evapo- ration, extraction into an aqueous phase, separation on a silica gel column, coupling the excess of reagent to an aminophenol to give a product that can be extracted with water or by solvent venting systems attached to the GC.s This paper describes the determination of ACE inhibitors and their active metabolites by derivatization with PFB-Br and electron-capture detection, employing a temperature- controlled evaporation procedure to remove the excess of derivatizing agent. Experimental The ACE inhibitor ramiprilat was used as an internal standard for the calibration of the response of the system to the other compounds, the drug perindopril being used when the system's response to ramiprilat was investigated.Pure stock standard solutions of the internal standard, drugs and metabolites were made up to a concentration of 1 mg cm-3 in methanol and stored below 4 "C. The derivatization procedure included the addition of potassium acetate (10 mg), acetone (3 cm3), internal standard (ramiprilat, 100 pg, 100 mm3) and an aliquot (1-100 mm3) of the stock solution of the ACE inhibitor, or metabolite, being investigated to a 10 cm3 vial. PFB-Br (100 mm3) was then added, the vial capped and the mixture vortexed at 70 "C for 2 h. After derivatization the sample was left to cool. An aliquot (250 mm3 of the cooled solution was evaporated to dryness in a 0.5 cm vial at 100 "C for 15 min.Following evaporation, the Sam le was taken up in acetone (250 mm3) and injected (0.5 mm ) onto the gas chromato raph. A Varian 3400 GC equipped with a nickel (6 Ni) radioactive ECD unit and coiled glass tube column (30 m x 0.252 mm i.d.) packed with a methylsilicone liquid phase was used in the experiment. The column, injector and detector port tempera- tures were set to 295,300 and 310 "C, respectively. The carrier gas, helium, pressure was 25 psi and the argon-methane flow was set to 30 cm3 min-'. 2 s B Results and Discussion Standard curves were obtained for all nine componds investi- gated with the correlation coefficient (Y) being obtained for each. All the nine compounds investigated had different retention times, achieving good separation between each peak,372 ANALYTICAL PROCEEDINGS, SEPTEMBER 1993, VOL 30 Table 1 Retention times (RT), relative standard deviations (RSD) and limits of detection (LOD) of the ACE inhibitors and active metabolites investigated LOD (pg on- Drug RT/min RSD (%) column) Captopril Perindopril Enalapril Perindoprilat Ramipril Enalaprilat Benazepril Ramiprilat Benazeprilat 3.69 4.69 7.15 8.54 10.33 12.59 13.96 18.78 25.80 4.80 2.93 3.79 5.55 2.00 2.81 6.81 4.08 2.18 1.35 0.87 1.03 1.55 0.56 0.83 1.89 0.79 0.59 hence, if necessary, permitting the simultaneous measurement of all the ACE inhibitors investigated here. An example of a typical chromatogram is shown in Fig.1. The standard curves were all based on 60 readings and the r values obtained were always greater than 0.998.The retention times (RT) of the ACE inhibitors investigated, together with their relative standard deviations (RSD) and limits of detection (LOD), are given in Table 1. The relative standard deviations indicated the precision of the injections and the limits of detection were a measure of the smallest amount of drug which can be detected using this method. The work presented here tested whether electron capture-gas chromatography (EC-GC) could be used as an analytical tool for the detection of ACE inhibitors. For EC-GC to be used in the analysis of this group of chemicals, two problems had to be overcome. Firstly, as mono- and di- acid moieties these compounds had to be converted into a form that could be volatilized in the gas chromatograph, and secondly, the molecule had to be altered in order to make it detectable by electron capture, since ACE inhibitors possess little electron capture ability.Pentafluorobenzyl bromide (PFB-Br) was chosen as the molecule to be attached to the parent compound to enable volatilization and detection as it was known to be a successful derivatizing agent of carboxylic acid groups and had been previously used in the analysis of c a p t ~ p r i l . ~ Potassium acetate used as the catalyst has been reported to impose a selectivity upon the PFB-Br for the alkylation of carboxylic acid groups only. Ramiprilat was chosen as the internal standard, as it stood alone on the chromatograph with no interfering peaks within 5 min either side.In the present study, evaporation of the derivatized samples at 100 "C for 15 min proved to be an effective way of eliminating, through volatilization, the excess of PFB-Br reagent and its derivatives of low molecular mass. This procedure resulted in a clearer chromatogram with fully resolved peaks at earlier times in the elution, with the added benefit that the detector, through not being overloaded, easily remained within its linear range. This modification solved many problems such as detector desensitization and hence the procedure gave reliable and reproducible results. Using ramiprilat as the internal standard and the clean up procedure described above, the assay was applied to all the drugs. The results presented in this paper showed that for each of the compounds, the routine analysis gave linear standard curves over the range 0.31-15.75 ng of drug going on the column.Work to establish day-to-day variation showed the deriva- tized ACE inhibitors investigated to be stable for at least 1 month under normal laboratory conditions. This was achieved by reinjecting a solution daily over the period of study and comparing the relative heights. This work has shown that a traditional method of detection such as electron capture remains a useful tool in pharma- ceutical research despite the increasing use of more expensive and elaborate techniques such as GC-MS. References 1 Biollaz, J., Schelling, J . L., Jacot Des Combes, B . , Brunner, D . B . , Desponds, G., Brunner, H. R . , Ulm, E. H., Hichens, M., and Gomez, H. J., Br.J. Clin. Pharmacol., 1982, 14, 363. 2 Kaiser, G., Ackermann, R., Dieterle, W., and Dubois, J . , J. Chromatogr., Biomed. Appl. 1987, 419, 123. 3 Ito, T., Matsuki, Y., Kurihara, H . , and Nambara, T., J . Chromatogr., 1987, 417, 79. 4 Dilloway, M. R . , and Hardman, T. C., Proceedings of the Fourth Annual Conference on Ace Inhibitors, London, 1991. 5 Gyllenhaal, O., Brotell, H . , and Sandgren, B., J. Chromatogr. 1976, 122, 471. Determination of Total and Ionic Chloride and Bromide in a Cross- linked Quaternary Ammonium-substituted Polymethacrylate by Ion Chromatography Ian D. Smith, Paul D. Blackler and David G. Waters Analytical Sciences Department, Smith Kline Beecham Pharmaceuticals, Old Powder Mills, Leigh, Kent TNII 9AN A quaternized polymethacrylate resin, SK&F97426-A, is undergoing development as a potential bile acid sequestrant. Bile acid sequestrants are commonly ion-exchange resins that bind bile acids in the gut and cause them to be excreted in the faeces.They are used to treat hypercholesterolaemia where dietary control of lipids has proved inadequate. This paper discusses methods employed for the determi- nation of ionic and total halides in SK&F97426-A. Chloride and bromide levels were determined as a means of measuring batch-to-batch variation in the final product. Ionic bromide is toxic and has to be controlled to low levels. The specification for SK&F97426-A requires a maximum of 0.2% m/m bromide in approximately 10% m/m chloride. The halides were originally determined potentiometrically , ionic halides after displacement by nitrate and total halides after oxygen flask combustion. Potentiometry had a limit of detection of approximately 0.5% m/m for bromide in SK&F97426-A.Once the lower specification was set, a more sensitive method had to be found and ion chromatography was adopted. The concentration of nitrate used as the displacer was too high to allow a satisfactory separation of the nitrate and bromide peaks. Nitrate was replaced with sulfate, which is wellANALYTICAL PROCEEDINGS, SEPTEMBER 1993, VOL 30 373 50 > E . fn 0 a fn 2 L c 0 al c 2 I 1; 0 0.8 1.6 2.4 3.2 4.0 4.8 5.6 6.4 7.2 8.0 a Retention t i m e h i n Fig. 1 Chromatogram of bromide standard solution showing bromide peak and sulfate from carry-over separated from both the analytes of interest and quantitatively displaced both anions from the polymeric matrix. Experimental Instrumental The ion chromatograph was a Dionex Model 2010i with an anion micromembrane suppressor and a conductivity detector.A Dionex 25 cm IonPac AS4A analytical column with a 5 cm IonPac AG4A guard column were used at ambient tempera- ture. Sample injection was performed with a Perkin-Elmer ISS-100 autosampler with a 20 mm3 stainless steel injection loop, operated in filled-loop mode. The mobile phase was 0.75 mmol dm-3 sodium hydrogencarbonate and 2.2 mmol dm-3 sodium carbonate at a flow rate of 2.0 cm3 min-l. The suppressor regenerant solution was 25 mmol dm-3 sulfuric acid at a flow rate of 5 cm3 min-l. A Waters 860 ‘ExpertEase’ chromatography data system was used.High intensity light sources housed in an enclosed safety cabinet were used to initiate the combustion in the flask. The combustion chamber, flasks and sample holders were prepared by an in-house technical service department. Sample Preparation As SK&F97426-A is hygroscopic, samples were dried under vacuum at 60 “C overnight before analysis and sample weigh- ings performed as rapidly as possible to reduce the risk of the sample adsorbing moisture. To avoid contamination during sample preparation, all apparatus was repeatedly rinsed with high-performance liquid chromatography (HPLC) grade water before use. Disposable latex gloves were worn for all sample handling and preparation and all reagents used were of the highest purity.Ionic chloride und bromide The exchange of sulfate for the analyte ions was performed in plastic beakers as beads of the sample tended to adhere to glass. A small amount of acetone was added as a wetting agent to disperse the polymer. Approximately 400 mg of SK&F97426-A were stirred with 100 cm3 of 20% m/v sodium sulfate solution for an hour. The slurry was filtered, the filter cake washed and the filtrate and washings pooled and made up to 250 cm3 with HPLC-grade water. Separate dilutions were prepared for ionic bromide (1 + 19) and ionic chloride (1 + 249), which were analysed against 0.5 pg cm-3 bromide and 1.5 pg cmW3 chloride standard solutions, respectively. Total chloride and bromide Combustion flasks containing 50 cm3 of 10 mmol dm-3 sodium hydroxide solution were purged with oxygen.Approximately 50 mg of SK&F97426-A were weighed into gelatine capsules, which were wrapped in a filter paper thimble and placed in a platinum mesh sample holder. After combustion, the flask was shaken vigorously by hand for 5 min to dissolve the combustion products. The contents and washings of the flask were made up to 250 cm3 with HPLC-grade water. This solution was filtered to 0.45 pm and analysed directly for total bromide against a 0.5 pg cm-3 standard solution and diluted 1 + 19 to determine total chloride against a 1.5 pg cm-3 standard solution. Chromatography The bromide peak eluted earlier in samples for ionic halides than in the standards. This was ascribed to a displacement effect of sulfate moving through the column.Chloride eluted at approximately 1.4 min, bromide at approximately 2.2 min and sulfate at approximately 4.9 min. Fig. 1 shows a chromatogram of a bromide standard solution and Fig. 2 of an ionic chloride sample solution. There is some carry-over of sulfate visible in Fig. 1, thought to be due to the use of a stainless steel injector loop. Method Validation Linearity of response Linearity of response was tested for both analytes over relatively narrow concentration ranges, 0.5-3 pg cm-3 for chloride (approximately 5-28% m/m) and 0.1-1.5 pg cm-3 for bromide (approximately 0.02-0.36% d m ) . Satisfactory linearity for each of the analytes was demonstrated over the concentration range examined (220.998). Negligible inter- cepts suggested that single-point standards would not cause significant errors in calculated concentrations. Precision of replicate injections Ten injections were made of standard solutions of each analyte and the precision was measured by the YO relative standard deviation (%RSD) for the peak areas. It was found to be 1.0% for chloride and 5.1% for bromide. Precision of replicate preparations Replicate injections were made of each of several separately- prepared sample solutions. The results were subjected to one- way analysis of variance (ANOVA). Acceptable precision for374 ANALYTICAL PROCEEDINGS, SEPTEMBER 1993, VOL 30 180 0 I I I I 1 I I I I 1 0.8 1.6 2.4 3.2 4.0 4.8 5.6 6.4 7.2 8.0 Retention ti me/m i n Fig. 2 Chromatogram of ionic chloride sample solutions showing chloride and sulfate peaks replicate sample preparations was found for both total and ionic chloride and bromide. Standard and sample stability Standard solutions were stored in stoppered, clear glass calibrated flasks at room temperature and analysed against freshly-prepared standard solutions. Complete stability over 7 d was demonstrated. Sample solutions could be left in contact with the polymer overnight and sample solutions could be analysed up to a day after separation from the polymer without significant effects on the results. Ruggedness Assay results at flow rates of 1.8 and 2.2 cm3 min-' were compared with those at 2.0 cm3 min-l. Assays with mobile phases of 90 and 110% of the nominal concentrations of carbonate and hydrogencarbonate were compared with the nominal concentrations. The method was shown to be robust with respect to the mobile phase flow rate and composition over the ranges examined. Limits of detection The limit of detection was defined as the concentration that would give a peak height equal to three times the baseline noise. For chloride it was found to be 0.125% m/m and for bromide 0.008% m/m. Accuracy To test the methods, SK&F97426-A was analysed for total chloride and bromide by neutron activation analysis. This indicated that our methods were of acceptable accuracy. Conclusions Methods for the determination of ionic and total halides in SK&F97426-A and validation work undertaken with these methods were discussed. These standard methods have been in regular use for some time in our laboratory.

ISSN:0144-557X    

DOI:10.1039/AP9933000361

出版商:RSC    

年代:1993

数据来源: RSC

摘要:

374 ANALYTICAL PROCEEDINGS, SEPTEMBER 1993, VOL 30 Use of Radiolabelled Drug Substance to Investigate Mass Balance During Validation of a High-performance Liquid Chromatography Method for Impurities A. A. Priestner Analytical Sciences, Glaxo Group Research, Park Road, Ware, Hertfordshire SG I2 ODP Radiochemical detection is a sensitive technique which can be employed for a number of applications within the area of pharmaceutical analysis. It is an especially useful tool for determining the mass balance during the development and validation of analytical methods.'.' This paper describes how radiochemical detection has been employed to investigate quantitatively and qualitatively the accuracy of an ultraviolet (UV)-based high-performance liquid chromatography (HPLC) method. A novel approach was taken whereby mass balance, validation and structural elucida- tion of light degradation products by liquid chromatography- mass spectrometry (LC-MS) were investigated simultaneously.Mass balance is achieved when all sample components are accurately quantified, i.e., the percentage main component, when added to the total percentage of all other impurities, equals 100%. Mass balance can be investigated by artificial degradation of drug substances or solutions followed by analysis using a number of different separation techniques [e.g., HPLC, thin-ANALYTICAL PROCEEDINGS, SEPTEMBER 1993, VOL 30 375 layer chromatography (TLC) , capillary electrophoresis (CE)] or a number of different detection techniques [e.g. UV, infrared (IR) fluorescence, radiochemical].The correlation of drug-related impurity levels across the different separation and detection techniques can partially validate a method. Radiochemical detection was chosen as an alternative to UV detection for the assessment of mass balance of an HPLC method for impurities for several reasons. Radiochemical detection permits sensitive detection of the drug-related impurities on-line with HPLC. It also allows labelling of the degradation products, usually without altering the degradation mechanisms, thus enabling the detection of impurities which may otherwise not be detected by UV absorption. Radio- chemical detectors have many of the advantages of UV detectors, but do not have the disadvantage of a variable response to different impurities, providing the radiolabel is retained within the molecule.Thus, it is possible to assess the mass balance of a sample for a particular method both quantitatively and qualitatively. The labelling of the impurities also aids the identification of drug-related impurities by LC-MS. For example, preparation of stressed solutions in a ratio of 3 : 1 I2C : I4C material, by weight, permits the identification of the degradation impurities by their characteristic mass spectrum doublets. Fig. 1 shows the configuration of a typical radio-HPLC. The flow-through cell contained a solid scintillator, calcium fluoride. The scintillator traps the energy of the radioactive particles and converts that energy to light scintillations. The number of scintillations measured as counts per minute (CPM) is proportional to the number of radioactive disintegrations per minute (DPM) in a ratio dependent on the efficiency of the detector: CPM - % detector DPM efficiency loox-- In general, as the residence time within the flow cell is increased, sensitivity is increased, but the resolution of the system is reduced.Therefore, in practice a compromise must be made between cell volume and flow rate in order to achieve adequate sensitivity without loss of resolution of the system.' Equipment A SOL2 light cabinet with sunlight filter (UVB plus UVA plus visible light 280-800 nm) was used for light degradation of drug solutions (UVA Light Technology Ltd, UK). The radio-HPLC consisted of an LDC pump, ABI 1OOOS UV detector, Raytest Ramona-5 radioactivity detector with calcium fluoride scintil- lator cell (0.4 cm3 volume) and a Gilson 231 autosampler.Controller Fig. 1. A typical radio-HPLC configuration A Beckman LS 6OOOSC liquid scintillation counter was used for the quantitative determination of mass balance. HPLC columns assessed included: Spherisorb phenyl(5 pm) 100 X 4.6 mm i.d. (Capital); Spherisorb nitrile (5 pm) 100 X 4.6 mm i.d. (Phase Separations). Experimental There were three main objectives: (1) to investigate the mass balance of an HPLC method used for the determination of drug-related impurity levels in drug substance. This method employed UV detection and a phenyl HPLC column; (2) to validate the above method; (3) to identify the principal photolytic product in light-stressed solutions of the drug. The work comprised of the following: (1) the development of an LC-MS compatible HPLC method; (2) preliminary investi- gations to ensure that the equipment and materials were suitable for their intended use; (3) preparation of control and light-stressed radiolabelled solutions of the drug; (4) the qualitative and quantitative assessment of mass balance, including the recovery of radiolabelled material from nitrile and phenyl columns, using the control stressed solutions; ( 5 ) the identification of the principal photolytic product by Fig.2 shows the chromatogram obtained from analysis of a solution of the drug which had been subjected to 5 h in the SOL2 light cabinet. The principal photolytic product is clearly visible at a retention time of 5 min, whilst the main component elutes at 6 min.The method undergoing validation employed triethylamaine phosphate buffer which is not volatile and therefore is incompatible with thermospray LC-MS. However, since identification of the principal photolysis impurity by LC- MS was required a different HPLC method was developed using ammonium acetate buffer. This was optimized for the resolution of the principal photolysis impurity from the main component peak (compound A in Fig. 3). The column was also changed from phenyl to nitrile stationary phase to improve the resolution of the peaks. A number of preliminary investigations were necessary to ensure that the equipment and materials were suitable for their intended purpose. These included: (1) the assessment of purity of the radiolabelled material; (2) the determination of the linear range of both the UV and radiochemical detectors; (3) the determination of efficiency of the on-line radiochemical detector.The efficiency of the solid scintillator cell was found to be 88% which was considered to be adequate for the qualitative determination of mass balance, but was too low for the quantitative assessment, so liquid scintillation counting was used for this aspect of the investigation. LC-MS. z ; 0 1 1' t.' 18.00 a m 16.00 1 I 1 0.00 5.00 10.00 15.00 Retention time/min HPLC chromatogram of the UV impurity profile of com- Fig. 2. pound A solution after 5 h light degradation376 ANALYTICAL PROCEEDINGS7 SEPTEMBER 1993, VOL 30 14.00 12.00 1 0, 10.00 0, U .- 2 8.00 - 1 a 6.00 4.00 U I I I 0.00 5.00 10.00 15.00 Retention ti m e/m i n Fig.3. Chromatography obtained for compound A photolysis impurities using an LC-MS compatible method. HPLC conditions S3CN 10 cm column, 95% 0.025 mol dm-3 ammonium acetate, pH 4.3, 5% acetonitrile Liquid scintillation counting (LSC) was used to determine the percentage recovery of radiolabelled material from the analytical column: Recovery (%) = x 100 dpm recovered from column" dpm recovered when no column present* This approach to the determination of recovery corrects for all other losses of material which are not related to the presence of an HPLC column. The effects of three variables on column recovery were investigated: age of analytical column; type of analytical column; extent of sample degradation. Results and Discussion The impurity profile of a light-stressed radiolabelled solution by UV detection is shown in Fig.4, and the impurity profile of the same solution by radiochemical detection is shown in Fig. 5. Fewer impurities were detected by radiochemical detection than by UV owing to band broadening caused by the larger volume flow cell required to achieve adequate sensitivity. Despite this loss of resolution, it was possible to conclude that no major new impurity was detected by radiochemical means that was not already visible by UV detection. Table 1 shows the level of impurities in stressed and unstressed solutions determined by their UV and radiochemi- cal responses. On comparison of the impurity levels, significant differences were observed between the two sets of data.Higher impurity levels were detected by radiochemical means than by UV absorbance, especially in the light-stressed solutions. For example, in light-stressed solutions the principal impurity by UV detection was 11.7%, but by radiochemical detection was 21.7%. This is due to the fact that the drug-related impurities possess different UV responses whereas the radiochemical response is directly proportional to molar concentration of radiolabelled material. The results demonstrate that despite * Corrected for blank dpm. 14.00 m 12.00 2 x 10.00 .z - 8.00 a 6.00 1 0, U F 4.00 1 I 0.00 2.00 4.00 6.00 8.00 10.00 Retention time/min Fig. 4. Chromatogram of the UV profile of the light-stressed radiolabelled drug solution 250.00 200.00 a X 150.00 I1 0) U 4 4 .- 100.00 E a 50.00 0.00 5.00 10.00 15.00 Retention timelmin Fig.5 . stressed radiolabelled drug solution Chromatogram of the radiochemical profile of the light- the UV and radiochemical profiles being qualitatively similar, there is a significant difference in the quantification of these profiles. Therefore, UV detection, without response factor correction, will give results which underestimate the impurity levels of a sample. 'The recovery results are shown in Table 2. No significant difference was observed, within the limits of experimental error, in recovery from old and new phenyl columns. Therefore, it was demonstrated that the column performs in the same way after 12 months of routine use as it did when it was new. The nitrile column demonstrated similar recoveries to phenyl columns.This has signficance in the cross-validation of results obtained by the two different HPLC methods. However, there was a significant difference in the recovery of light-stressed and unstressed material, from both nitrile and phenyl columns. An amount @-lo%) of the radiolabelled material was not recovered within the 20 min run time for light- stressed solutions of the drug. This is most likely due to the formation of less polar photolysis impurities which are retained by the column. When column recoveries are less than %YO, the Table 1 Impurity levels of light-stressed and unstressed radiolabelled drug solutions by UV and radiochemical detection Impurity levels (% by area normalization) UV detection at 225 nm Radiochemical detection Principal Total Total no.of Principal Total Total no. of Sample impurity RRT impurities impurities impurity RRT impurities impurities Control 0.7 0.71 2.0 7 2.7 0.70 3.5 3 Light-stressed 11.7 0.81 15.3 8 21.7 0.83 34.8 3ANALYTICAL PROCEEDINGS, SEPTEMBER 1993, VOL 30 377 primary reason, assuming no problems with injection, is adsorption of drug to the column.' Thus, it was demonstrated that age and type of column did not have an adverse effect on recovery, but that the extent of sample degradation did have a significant effect on column recovery. The fraction of mobile phase containing the principal photolysis impurity was col- lected and then analysed by LC-MS. The data obtained indicated the molecular weight of the impurity, as 32 atomic mass units higher than the parent drug, suggesting the presence of two additional oxygen atoms.Further fragmentation data Table 2 The recovery of light-stressed and unstressed radiolabelled drug solutions using various HPLC columns HPLC column Compound A stationary sample solution phase Recovery (%) Light-stressed Old phenyl 90 Unstressed New phenyl 101 Light-stressed New phenyl 92 Light-stressed Nitrile 92 Unstressed Nitrile 106 indicated that the principal photolysis impurity was a dihy- droxy derivative of the parent drug. Conclusions The mass balance of the phenyl column-based HPLC method with UV detection was found to be unsatisfactory for low levels of impurities, but could be improved by use of UV response factors. It was also demonstrated, by comparison with radio- chemical detection, that the method shows poor mass balance when applied to heavily degraded samples. The principal photolysis impurity was tentatively identified by mass spectral data to be a dihydroxy derivative of the parent drug. In conclusion, it was demonstrated that radio-HPLC and liquid scintillation counting are powerful techniques for the investigation of mass balance and validation of HPLC methods. References 1 Quint, J., and Newton, J. F., in HPLC in the Pharmaceutical Industry, eds. Frong, G. W., and Lam, S. K.. Marcel Dekker, New York, 1991, pp. 101-122. Veltkamp, A. C., J. Chromatogr., 1990, 531, 101. 2

ISSN:0144-557X    

DOI:10.1039/AP9933000374

出版商:RSC    

年代:1993

数据来源: RSC

摘要:

378 ANALYTICAL PROCEEDINGS, SEPTEMBER 1993, VOL 30 EQUIPMENT NEWS Flame Analysis of Aqueous Samples Shimadzu have introduced a micro-volume flame analysis system with their AA-6501 Series atomic absorption spectrophotometers, which typically use a 60 pl sample volume. The technique can be fully automated with the use of the ASC6000 semi-intelligent preparation station. Standard curves can be produced from a single stock standard, essen- tial matrix modifiers added automatically and analysis performed on up to 60 samples. V. A. Howe and Co. Ltd., Beaumont Close, Banbury, Oxfordshire OX1 6 7RG. Isotope Ratios in Water Samples Studies on l60/l8O ratios in water samples are an important tool in tracking biological and metabolic pathways of common atmos- pheric and water-borne pollutants.Using the Optima-Isoprep 18 mass spectrometry based analyzer researchers from the Laboratoire de Biogkochemique Isotopique in Paris can now study isotope ratios from water samples as small as 50 pl, while retaining excellent re- producibili ty. VG Isotech, Aston Way, Middlewich, Cheshire CW 10 OHS. Chromatography Autosampler As a stand-alone unit, the GINA 50 autosam- pler from Gynkotek offers unequalled price- performance qualities, with variable volume, zero-loss injection and sequential standard analysis. In combination with Gynkosoft sys- tem control and data capture software it of- fers not only random access programmability but even advanced inter-vial dosing routines for a multitude of applications. A brochure is available. Severn Analytical, 10 Waterloo Street West, Macclesfield, Cheshire SK11 6PJ.Gas Chromatograph The HP 5890 Series I1 Plus, with up to six channels of electronic pressure control, pro- vides precise digital control of all GC gases, both inlet and detector. When combined with an HP autosampler and ChemStation it offers totally automated gas chromatography. Hewlett-Packard S.A., 150 route du Nant- d'Avril, CH-1217 Meyrin 2, Switzerland. Cartridge Columns for HPLC The newly designed HPLC Cartridge Col- umn System offers the same high efficiency and leak-proof integrity as do conventional HPLC columns. The system, comprising polymer-to-steel connections, reusable end- fittings, an integrated guard system, and re- placeable frit assemblies, provides all the benefits associated with cartridge systems in addition to offering opportunities for long- term process improvements in HPLC column manufacturing.The system is offered in most SUPELCOSIL phases of 150 mm or 250 mm column lengths, 4.6 mm column i.d. Supelco Inc., Supelco Park, Bellefonte, PA 16823, USA. Preparative HPLC Columns A new range of preparative HPLC columns incorporates the popular void sealing mecha- nism featured in the Partisphere system. The void sealing mechanism allows the inlet frit to be maintained in close contact with the top of the column bed and helps to overcome the problem caused by voids forming at the top of the column as a result of prolonged use of aqueous-based mobile phases. Available in three standard diameters-4.6, 9.5 and 25 mm ID-the WVS range is available pre- packed with a choice of high-performance 5 pm spherical and 10 pm irregular silica me- dia.Whatman Scientific Ltd., Whatman House, St. Leonard's Road, 20/20 Maidstone, Kent ME 16 OLS. Diode-array Detector for Chromatog- Optional diode-array detection capability is announced for the HP supercritical fluid chromatograph. Offering advanced automat- ion and spectral evaluation techniques, the new detector allows UV-visible spectral measurements to be taken continuously across a broad spectral range, providing a third dimension of spectral data that enables analysts to make judgments with greater con- fidence than is possible with single-wave- length data. Hewlett-Packard S.A., 150 route du Nant- d' Avril, CH- 12 17 Meyrin 2, Switzerland. raphy LC to IC Conversion The Metrohm IC690 conductivity detector is based on the electronic suppression principle and has been designed to ensure that the elec- tronic and thermal interferences of the meas- uring signal are virtually eliminated.Measuring cell and pre-amplifier are incorpo- rated in a thermostatted, thermally insulated heating block. The measuring cell tempera- ture is controlled to an accuracy of & 0.01 "C. The volume of the measuring cell is less than 1.5 p 1. The IC690 is available as an add-on to existing LC systems. V. A. Howe and Co. Ltd., Beaumont Close, Banbury, Oxfordshire OX 16 7RG. Software for Air Monitoring Method- SupelAir provides a unique, quick and simple way of finding the appropriate methodology for industrial hygiene needs. US NIOSH and OSHA air monitoring methods are referenced with essential information including sam- pling flow rates, sampling volumes, time ology weighted averages, short-term exposure lim- its, recommended sampler or collector, rec- ommended analytical technique, and product citations.SupelAir contains three indexes: an alphabetical listing of compound names, a numerical listing of NIOSH/OSHA methods, and a Chemical Abstracts Service registry cross reference. The program runs on an IBM compatible personal computer under either DOS or Microsoft Windows. Supelchem UK, Shire Hill, Saffron Wal- den. Essex CB l l 3AZ. Portable Humidity Monitor CERMET-P provides a measurement range of -80 to +20 "C dewpoint and the ability to perform analyses down to 0.1 ppm (V) at me- dia pressures as high as 300 bar gauge.The sampling system is designed to present for analysis by Michell's Ceramic Moisture Sen- sor a wholly gaseous phase sample at a fixed, known high pressure at which it can be en- sured that freeze-up problems occurring at re- duced pressure are avoided. Michell Instruments Ltd., Nuffield Close, Cambridge CB4 1 SS. Water Analysis Technique A new technique has been developed involv- ing a direct, solvent-free extraction of organic compounds from aqueous samples. Solid Phase MicroExtraction (SPME) uses coated fused silica fibres as micro solid phase ex- tractors. The organic analytes are adsorbed direct onto the coated fibre which is then in- serted into the GC injection port for thermal desorption. SPME is quantitative--15 ppt de- tection limits can be attained for most volatile compounds-and is rapid, with only 2-15 min for analytes to reach equilibrium in theANALYTICAL PROCEEDINGS, SEPTEMBER 1993, VOL 30 100 pm stationary phase coating. den, Essex CB l l 3AZ.Supelchem UK, Shire Hill, Saffron Wal- Liquid Manipulation Equipment The Hamilton OEM Microlab system is a se- ries of six units which perform various tasks from pipetting to valve operation, all control- led from a PC. The volume range is from below I pl to above 50 ml, and up to 14 units can be controlled from one PC. Accurate vol- umes can be aspirated/dispensed or pumped to and from vessels. Any liquid can be used from caustic to viscose glues, as the liquid lines are all PTFE coated. V. A. Howe and Co. Ltd., Beaumont Close, Banbury, Oxfordshire OX16 7RG.Titrators Three new models replace the earlier DL70: the DL77, which allows genuine multitasking as well as parallel titrations with a second titration stand; the DL70 ES, which is a mul- tipurpose titrator offering numerous analyti- cal possibilities; and the DL67, which is eminently suitable for routine tasks. The out- standing features include operation in dialog via a multiline display with graphics capabil- ity and in five languages. All three can be be equipped with an extensive range of accesso- ries. Mettler-Toledo AG, CH-8606 Greifensee, Switzerland. Pocket Thermometer The Thermapen gives a clear digital reading of temperatures from -50 to +300 "C. Two different Thermapen thermometers are avail- able: the Thermapen 1, which accurately reg- isters temperatures in the range -49.9 to +199.9 "C, and the Thermapen 5 between -50 and +300 "C.All the thermometers are calibrated against Laboratory Standards traceable via NAMAS Certification to British National Standards. Electronic Temperature Instruments Ltd., Southdownview Road, Broadwater Trading Estate, Worthing, West Sussex BN 14 8NL. Hand-Held Relative Humidity and Temperature Meter The MC-P Portable uses the makers' Mini- Cap 2 RH sensor, which provides excellent linearity, fast response and long-term stability over the RH range of 5 to 95%. Standard features include a large LCD which simulta- neously displays RH and temperature, auto- matic calibration, user-programmable high/low RH and temperature alarms, indi- vidual analogue outputs for RH and tempera- ture, serial output via an RS232 converter and an automatic shut-off.Panametrics Ltd., Unit Two, Villiers Court, 40 Upper Mulgrave Road, Cheam, Surrey SM2 7AJ. Radioactive Waste Management Following the introduction of the LS 6500 liquid scintillation counter, the makers have launched a radioactive waste management option. The Radioactive Waste Manager automatically records the activity (DPM, Becquerels or Curies) in samples as they are counted in the instrument. A printed report of the activity in a particular waste container is available from the system at any time. The report identifies the isotopes, corrects for half life if the waste is stored and can individually track the waste streams of different users. Beckman Instruments (UK) Ltd., Progress Road, Sands Industrial Estate, High Wy- combe, Buckinghamshire HP12 4JL. Surface Structure Database The Surface Structure Database, NIST Stand- ard Reference Database 42, is available for personal computers.It is the only complete critical compilation of reliable information on surface crystallographic structures available. Nearly 600 structures are included, covering a wide variety of materials of scientific and technological importance, including catalysts. US Department of Commerce, National Institute of Standards and Technology, Gaith- ersburg, MD 20899, USA. Balances The EK and EW Series balances are sturdily built for heavy duty industrial use, yet are accurate enough for many laboratory applica- tions. An EW model is an excellent choice for everyday weighing in g and/or ounces; the multipurpose EK offers extra functions, greater accuracy and six options of weighing unit.There are four capacities of EW bal- ance: 60 x 0.002 g, 300 x 0.01, 600 x 0.2 g, and 3000 x 1 g. EW balances are available in two versions: the EW-A for AC operation and the EW-B powered by a rechargeable battery pack. The EK balances will weigh in a choice of g, ounces (avoir and troy), pounds, penny- weights or grains. There are three models of- fering capacities of 120 x 0.01 g, 1200 x 0.1 g, and 12 000 x 1 g. A & D Instruments Ltd., Abingdon Sci- ence Park, Abingdon, Oxford OX14 3YS. Oscillating Tissue Slicer An updated version of the EMS oscillating tissue slicer allows the operator the choice of activating the blade oscillation either through a toggle switch on the front panel for con- tinuous motion or with a foot pedal. Mount- ing of the specimen can be done direct on the bi-level pivotal pedestal, complete with a pivot pin which offers the provision to change the angle of the specimen relative to the blade oscillation-orientation of the speci- men.Science Services (UK) Ltd., Greenwood House, 4/7 Salisbury Court, London EC4 8BT. Laboratory Microwave Oven The EMS 820 laboratory microwave oven of- fers a number of features including an effect 379 control allowing change of effect even in the middle of a run, push-button setting of the timing mechanism, a continuous run control button for longer procedures over 99 min 99 s, a mixing arrangement for up to 5 different containers at once, a stainless-steel compart- ment, and an adjustable temperature probe.A brochure is available. Science Services (UK) Ltd., Greenwood House, 4/7 Salisbury Court, London EC4 8BT. Centrifuges Among the Howe-Sigma centrifuge range are five models that cover both high and low speed ranges, i.e., two machines in one pack- age, able to meet the requirements for several applications for pelleting cells, nuclei, mem- branous organelles, membrane fractions, ri- bosomes, polysomes and macromolecules on sample volumes up to 500 ml. The range cul- minates in the benchtop 3K30, which pro- duces 64 000 x g. V. A. Howe and Co. Ltd., Beaumont Close, Banbury, Oxfordshire OX16 7RG. Chamber Furnace The E-Con 10/8 compact 2.5 kW bench-top furnace offers a maximum service tempera- ture of 1000 "C from a chamber of 8 1 work- ing capacity.Of modular construction, the chamber contains refractory tiles in the roof and hearth for high resistance to physical damage, and its side walls incorporate em- bedded spiral heating elements which can be replaced simply by disconnecting the electri- cal termination at the rear and removing the side wall. Maintenance costs and down time are therefore low. Pyro Them Furnaces, Unit Three, Hal- cyon House, 20 Goward Street, Market Har- borough, Leicestershire LE16 9AF. n b e Furnaces The P-Tube-12 Series of tube furnaces offers heated lengths from 150 to 750 mm at maxi- mum operational temperatures of 1200 "C with tube internal diameters from 25 to 150 mm. Options for special applications include multizoned heating.Pyro Therm Furnaces, Unit Three, Hal- cyon House, 20 Goward Street, Market Har- borough, Leicestershire LE 16 9AF. Bench Store The environmentally friendly SCH-2 Cryo- Store eliminates the need for dry ice. It offers two perspex-covered chambers, 9 x 14 x 4 cm, each able to accommodate a microtitre rack of tubes. One chamber is maintained at least 50 "C below ambient temperature; the other is at ambient. Stuart Scientific Co. Ltd., Holmethorpe Avenue, Redhill, Surrey RHl 2NB. Microscope Camera The MC 80 microscope camera system for 35 mm photography has been extended with the380 ANALYTICAL PROCEEDINGS, SEPTEMBER 1993, VOL 30 Zeiss MC 80 microscope camera system introduction of a 4 x 5 format universal back. New Polaroid, Linhof and roll film backs can be fitted and full control of exposure main- tained through the camera control panel.The flexibility of the system allows automatic, manual and timed exposures as well as +2 to -2 stop adjustment. Carl Zeiss (Oberkochen) Ltd., P.O. Box 78, Woodfield Road, Welwyn Garden City, Hertfordshire AL7 1 LU. Inverted Microscopes A wide range of condensers and other fea- tures enables the new Diaphot 300 and 200 to be used for both conventional and advanced applications, from basic microscopy to UV fluorescence, in-vim fertilization, laser scan- ning confocal microscopy, micromanipula- tion and high resolution microscopy. Enhanced imaging results from a new optical design combined with the makers’ advanced lens technology. Nikon UK Ltd., Instruments Division, Haybrook, Halesfield 9, Telford, Shropshire TF7 4EW.Digital Recorder The DX-2000E DAT image recorder pro- vides ideal, high capacity digital storage for documents and high quality colour images ranging from microscopy to most video im- age storage applications. It is capable of stor- ing up to 1 1 37 colour images, 1804 monochrome images or 830 RGB images on a single rape. It provides a resolution of up to 500 lines in RGB and, because of the digital concept, is able to output crisp and clear, rock-steady images onto a display monitor. Mitsubishi Electric UK Ltd., Security De- partment, Professional Electronics Division, Travellers Lane, Hatfield, Hertfordshire ALlO 8XB. LITERATURE A brochure describes the CTA-2000 atomic absorption spectrophotometer. ChemTech Analytical Ltd., 4 Railton Road, Wolseley Business Park, Kempston, Bedford MK42 7PN.A 64-page brochure details supplies, accesso- ries, software and search libraries for users of Perkin-Elmer infrared spectrometers and as- sociated computers. Perkin-Elmer Ltd., Post Office Lane, Bea- consfield, Buckinghamshire HP9 I QA. A selection of literature gives details of the VG PlasmaTrace, which combines the advan- tages of the inductively coupled plasma source with the resolving power of a double focusing high resolution mass spectrometer. FI Elemental, Winsford, Cheshire. Bruker Report 139/93 provides information on NMR, FT-IR, EPR, MS and HPLC. It in- cludes an index of brochures and application notes. Bruker Spectrospin Ltd., Banner Lane, Coventry CV4 9GH. the chiral columns of the Techocel range is available.HPLC Technology Ltd., Wellington House, Waterloo Street West, Macclesfield, Cheshire SKI 1 6PJ. Tech Novations has been redesigned. The May-June 1993 issue introduces many new products including solid phase microextrac- tion syringes, solid phase extraction tubes, environmental standards and preparative HPLC columns. Supelco Inc., Supelco Park, Bellefonte, PA 16823-0048, USA. The 28-page Reporter (Vol. XI, No. 5), fea- tures new DEX cyclodextrin capillary col- umns for analysis of optical isomers, as well as several other topics. Supelco UK Ltd., Shire Hill, Saffron Wal- den, Essex CB l l 3AZ. The 24-page Reporter (Vol. XII, No. 2) fea- tures new solid phase microextraction (SPME) for eliminating most of the draw- backs to preparation of water samples. Among the other topics is a new a-DEX GC column that offers unique selectivity for en- antiomers and positional isomers of aromatic hydrocarbons. Supelco Inc., Supelco Park, Bellefonte, PA 16823-0048, USA. Focus-On (Vol. IV, No. 2) looks at a number of recent developments and several new/en- hanced products, all within the field of sepa- ration. Beckman Instruments (UK) Ltd., Progress Road, Sands Industrial Estate, High Wy- combe, Buckinghamshire HPl2 4JL. Two new Thermal Analysis Newsletters are available: ‘PETAN-40 is an Application Ex- ample of the Dynamic Mechanical Analysis of a Polypropylene Fibre’ and ‘PETAN-41 describes the use of Automatic Thermal Lag Compensation Software for DSC’. Perkin-Elmer Ltd., Post Office Lane, Bea- consfield, Buckinghamshire HP9 1QA. The Summer 1993 issue of Transtech Times with an overview on the Paramid Parallel Su- percomputers includes information on newly released products based around the Inmos Transputer, Texas C40 and Intel i860 proces- sors, many of which complement parallel products already in the field. Transtech Parallel Systems Ltd., Units 17-19, Manor Court Yard, Hughenden Ave- nue, High Wycombe, Buckinghamshire HP12 5RE. Aldrichimica Acta, Vol. 26, No. 1, includes papers on Electrochemistry in Organic Syn- thesis and The Ireland-Claisen Rearrange- ment. Aldrich Chemical Co. Inc., P.O. Box 355, A list of chiral separation applications using Milwaukee, WI 53201, USA.

ISSN:0144-557X    

DOI:10.1039/AP9933000378

出版商:RSC    

年代:1993

数据来源: RSC

摘要:

ANALYTICAL PROCEEDINGS, SEPTEMBER 1993, VOL 30 Conferences and Meetings Laboratory Exhibition and Conference October- 5-7,1993, London The latest in this series of exhibitions will be held in Earls Court 2 There will be over 300 stand holders representing the products of more than 500 companies. Associated with the exhibition there will be three seminars, organized by Bevan Gilpin Communications Ltd. and held in the Earls Court Park Inn Ho- tel. On October 5 , thc subject will be 'Good Practice With Analytical Data', presented by Peter Daisley; on October 6 'Analytical Quality Assurance' will be covered by Dr. Ernie Newman and Mr. Dennis Bucknell; fi- nally, on October 7 the seminar will be enti- tled 'Risk Management of Analytical Procedures' and led by Drs. Roger Slade and David Kennedy.For further information on the seminars contact Bevan Gilpin Communications Ltd., Unit 9 Hackney Business Centre, 277 Mare Street, London ES IEB, and on the exhibition contact Reed Exhibitions, 90 Calverley Road, Tunbridge Wells, Kent TN I I UN. Magnetic Sensors: Materials and Technol- ogy October 6, 1993, Hayes The UK Magnetics Club will be holding a one-day seminar at Thorn EM1 Central Re- search Laboratories, Hayes, Middlesex. Re- cent developments in magnetic materials research, especially in thin film, rnultilayer and magnetoelastic systems, has prompted fresh interest in the development of sensors and transducers that rely on a magnetic ele- ment. Many technologies that have relied on piezoresistive effects may benefit from a move to advanced materials.The science base has reached a sufficiently advanced stage that it is timely to bring together mem- bers of the academic and industrial communi- ties. For further information and a copy of the seminar programme contact Margaret Swad- ling, 'The Magnetics Club, Wantage Business Park, Wantage, Oxfordshire OX 12 9BJ. Monitor '93: Air Emissions Monitoring Conference and Exhibition October 21-22, 1993, Manchester The conference will be held in the Weston Lecture Theatre of the Manchester Confer- ence Centre. Over two days the Monitor '93 conference will cover the use of both new and existing monitoring techniques, provide guidance on the regulations and their applica- tion, and highlight practical examples of how authorizations are being achieved. An oppor- tunity will be provided by the discussion ses- sions and informal contacts for delegates from both industry and regulatory authorities to exchange views and experiences on the implementation of EPA.Running alongside the conference, the Monitor '93 exhibition will feature the latest developments in equip- ment and technology in the area of industrial air emissions monitoring. For further information about Monitor '93 contact the organizers: Spring lnnovations Limited, 216 Moss Lane, Bramhall, Stock- port SK7 IBD. Electrophoresis '93 Novemhiv- 7-10, 1993, Charleston, SC, USA Electrophoresis '93, an annual symposium sponsored by the Electrophoresis Society, will be held at the Wild Dunes Resort and Conference Center in Charleston, South Carolina, USA. It will include lecture and poster presentations, stimulating discussion sesions, workshops, new products and an in- strumentation exhibit, student awards, a best poster competition and social events.Poster abstracts are under consideration. For information contact Mrs. Janet Cunnngham, Electrophoresis Society, P.O. Box 179, Walkersville, MD 21793, USA. HPCE '94: Sixth Symposium on High Per- formance Capillary Electrophoresis Junuar.! 31-Fehui-ary 3, 1994, Suri Diego, Califi,miu, USA The sixth lnternational Symposium on High Performance Capillary Electrophoresis will be held in San Diego, California. The techni- cal programme will include invited and con- tributed papers and will feature the foremost investigators in the rapidly expanding field of capillary electrophoresis.There will be par- allel sessions of oral presentations on appli- cations of HPCE to provide focused, user-orientated programming. Posters will again play a major role in the scientific pro- gram. An exhibition of commercial HPCE systems and components is also planned. Lecture and poster topics will also include the following: Zone Electrophoresis; Isoelectric Focusing; Micellar Separations; 381 CE/Mass Spectrometry; Control of Electroos- rnosk; Analytical and Micropreparative Ap- plications; Pharmaceuticals, Carbohydrates, SrnalI Molecules and Ions, Gel Columns, Iso- tachophoresis, Detector Design, Chiral Sepa- rations, Column Coatings, Peptides and Proteins, Oilgonucleotides, Sub-Cellular Structures and Whole Cells. The San Diego Princess Resort on Mis- sion Bay will be the site of the Symposium.To obtain an abstract form and/or to be placed on the mailing list for the Preliminary Program and Registration booklet, please contact the Symposium Manager, Shirley Schlessingcr, 400 East Randolph Street, Suite 1 0 IS, Chicago, Illinois 6060 1, USA. SAC '95: The Eleventh SAC' Conference on Analytical Chemistry July 9-15. 1995, Hull The Analytical Division of the Royal Society of Chemistry is to hold SAC 95, an Interna- tional Symposium on Analytical Chemistry, at the University of Hull. This is the elcventh in the series of triennial symposia originally started by the Society for Analytical Chemis- try (hence SAC). The Analytical Division holds annually a Research and Developmcnt Topics Meeting for postgraduate research workers and younger workers in industry and the public services.In 1995 this meeting will be held at the University of Hull, as the first part of SAC 95, on Monday, July 10, and on the morning of Tuesday, July 11. The meet- ing normally contains 12-16 oral presenta- tions and about 100 poster presentations, and is a popular medium for encouraging younger workers to present their results to a wider audience. The targeted areas of the scientific progranime of SAC 9s will include: chiral recognition; analytical biotechnology; sensors; chemometrics; Process analysis; quality; work-place monitoring; legislativc requirements; sampling and sample prepara- tion; microwave heating; developments in atomic and molecular spectrometry. including ICP-MS and X-ray techniques; capillary electrophoresis; environmental monitoring; field analysis; imaging techniques: hyphen- ated techniques; sensory analysis; structure analysis; and microspectroscopy. For further information contact The Sec- retary, Analytical Division, The Royal Soci- ety of Chemistry, Piccadilly, London, W 1 V OBN.

ISSN:0144-557X    

DOI:10.1039/AP9933000381

出版商:RSC    

年代:1993

数据来源: RSC

摘要:

382 ANALYTICAL PROCEEDINGS, SEPTEMBER 1993, VOL 30 Courses Ensuring the Quality of Environmental Testing The following sessions are included in the October I2-I4, I993, Teddington programme: Defining the Terms (Ernie New- October 8,1993, Chester The Laboratory of the Government Chemist will be promoting the benefits of third party accreditation systems at a seminar for envi- ronmental testing laboratories and specifiers of laboratory services. Environmental testing laboratories must be able to have complete confidence in their results. Assessment by an independent set of criteria and subsequent ac- credi tation can give laboratories increased confidence in their results. Accreditation aids the users of laboratory services in choosing the most suitable laboratory for their analy- ses.This seminar is designed to bring out the man, Consultant o n Quality Systems); Ob- taining Analytical Accredi tat ion-A Practical Approach (Mark Kibblewhite, Wallace Evans Laboratories); Accreditation for Soils Testing (Tony Ellis, Clayton Environmental Consult- ants); Accreditation in the Air Environment (Mike Woodfield, Warren Spring Labora- tory); Accreditation in Support of Integrated Pollution Control (Stuart Newstead, New Majesty's Inspectorate of Pollution); and Specifying Services (Therese Vogt, Aspin- wall and Co). For a booking form and further details please contact: Linda Catterson, LGC, Queens Road, Teddington, Middlesex TW 1 1 This course will be held at the Forte Crest Hotel, Heathrow, and the Laboratory of the Government Chemist. The course will cover: Quality Assurance planning and manage- ment; Application of statistics to the quality assurance programme including the use of control charts; The importance of correct sampling procedures; NAMAS accreditation; GLP compliance programme; The application of LIMS to quality assurance; and Profi- ciency testing.Throughout the course there will be ample opportunity for discussion. Each participant will be supplied with a com- prehensive set of lecture notes. features of quality systems and accredited OLY. Enquiries should be directed to William services in order to stress the advantages to McNally, Laboratory of the Government laboratory users in the UK and the rest of Quality Assurance for Analytical Labora- Chemist, Queens Road, Teddington, Middle- Europe. tories sex TWll OLY.An Introduction to the Management of Laboratory Data: A Tutorial Approach Using Borland's Paradox0 Relational Database By C.N. Hegarty Dublin Corporation This important new book introduces chemists, laboratory supervisors and laboratory managers to the use of a relational database for the management of analytical data and gives detailed step-by-step instructions to lead the reader through the process of designing a simple functional Laboratory Information Management System (LIMS). No previous knowledge of a programming language is assumed, or is necessary, to make use of the invaluable information and guidance provided. The pragmatic tutorial approach adopted in the text leads to an intuitive understanding of the nature of relational databases, and the structure of Borland's Paradox relational database in particular.The full range of advanced features in Paradox are covered in the text, and each is used in at least one module of the LIMS. The text goes beyond the interactive use of the menu driven Paradox database, which is covered in many texts on the use of this programming language, and makes extensive use of the Paradox Application Language, PAL, to prepare code for the modules in the LIMS. A chapter is devoted to the use of the Paradox Data Entry Toolkit, which is an advanced feature of Paradox that is not covered in detail in other computer texts. This facility allows extensive control of the process of data entry into a relational database, where the Paradox Data Entry Toolkit acts as an on-line supervisor for the data entry sessions.This book will be of particular value to the functional analytical laboratory which does not have the support of a computer department or where funds are not available to invest in a commercial PC-based package. It leaves the reader in a position to modify the modules created in this text or to design and code new modules to meet the specific needs of his own laboratory. A free 3 1/2" disk is included with the book and gives an extensive demonstration of the database features. Hardcover xii + 588 pages ISBN 0 85186 219 5 (1992) Price S85.00 ROYAL To Order, Please write to: Royal Society of Chemistry, Turpin Distribution Services Ltd. Blackhorse Road, Letchworth, Herts SG6 1 HN, UK. or telephone (0462) 672555 quoting your credit card details. We accept Access/Visa/MasterCard/Eurocard.Turpin Distribution Services Limited is wholly owned by the Royal Society of Chemistry. For information on other books and journals, please write to: RSC Members ordering for their own personal use should obtain members prices and order from: The Membership Affairs Department at the Cambridge address above. Royal Society of Chemistry, Sales and Promotion Dept., Thomas Graham House, Science Park, Milton Road, Cambridge C64 4WF, UK. Information ServicesEIGHT PEAK INDEX OF MASS SPECTRA 4th Edition 1 The essential tool for I 1 mass spectrornetrists 1 NOW AVAILABLE - the new 4th Edition of the highly regarded Eight Peak Index of Mass Spectra. This quality compilation is recognised by many mass spectrometrists as the most useful index of mass spectra in print today. /E EIGHTPEAKINDEX EMPOWERS YOU TO: * identify unknowns rapidly and easily * locate spectra of compounds quickly by formula or molecular weight * match spectra simply through direct peak intensity comparison * find spectra relevant to your area of interest - a wide variety of * access the data at any time with no machine-time restrictions * use the data with confidence - extensive checks on all records have compound types are included been performed ROYAL SOCIETY OF CHEMISTRY I n for ma t ion Services Probably the best printed index of mass spectra in the world! For more information about the NEW edition, simply contact us at the address below for a copy of our detailed leaflet: Sales and Promotion Department Royal Society of Chemistry Thomas Graham House Science Park, Milton Road Cambridge CB4 4WF, United Kingdom Tel: +44 (0) 223 420066. Fax: +44 (0) 223 423623. Telex: 818293 ROYAL

ISSN:0144-557X    

DOI:10.1039/AP9933000382

出版商:RSC    

年代:1993

数据来源: RSC