ISSN:0144-557X    

DOI:10.1039/AP98926FX033

出版商:RSC    

年代:1989

数据来源: RSC

摘要:

ANPRDI 26(9) 305-328 (1 989) Proceedings of the Analytical Division of The Royal Society of Chemistry CONTENTS 305 Royal Society of Chemistry Awards 1988 306 Analytical Viewpoint 306 'Development of High Performance Pipette Fillers, Safe Practice in Handling Pipettes and Comparative Calibrations Between Transfer and Mechanical Pipettes' by Osamu Nara 31 1 SUMMARIES OF PAPERS 31 1 Signal Processing in Molecular Spectroscopy 31 1 'Fourier Transforms in Spectroscopy-a Chemometric Approach' by Richard G. Brereto n 313 Flow Analysis Methods 313 315 317 'Recent Advances i n Detection in Flow Injection Systems' by M. Valcarcel and M. D. Luque de Castro 'Ion Pairing Flow Injection Extraction' by M. Harriott and D. Thorburn Burns 'Flow Injection Analysis Using Antibodies and Other Receptor Proteins' by J. N. Miller 'Spectroscopy's Answer to the Nernst Equation' by Julian Tyson 'Flow Injection Analysers for Clinical Use' by B. F. Rocks 318 321 323 Equipment News 326 Ronald Belcher Memorial Award for 1990 326 Conferences and Meetings 327 Courses 328 - Analvtical , Division Diarv Typeset and printed by Black Bear Press Limited, Cambridge, England Analytical Proceedings September 1989

ISSN:0144-557X    

DOI:10.1039/AP98926BX035

出版商:RSC    

年代:1989

数据来源: RSC

摘要:

h Royal Society of Chemistry Awards 1988 At a ceremony held on June 7th, 1989, in Burlington House, the Royal Society of Chemistry Awards for Chromatography and Separation Chemistry (sponsored by Whatman) and for Industrial Analysis (sponsored by Tioxide International Ltd.) were awarded, respectively, to Professor A. F. Fell, of the University of Bradford, and Dr. T. B. Pierce, of UKAEA, Har- well. Our photograph shows (L-R) Dr. T. B. Pierce, Professor D. Thorburn Burns (President of the Analytical Division) , Professor J. M. Ward (President of the RSC) and Professor A. F. Fell. Analytical Applications of Spectroscopy Edited by C.S.Creaser, University of East Anglia and A.M.C. Davies, Institute of Food Research, Norwich This book provides a 'State-of-the-Art' review of the applications of the major spectroscopic techniques and will prove invaluable to researchers involved in this form of analysis.The book provides wide-ranging coverage of recent developments in analytical spectroscopy, and in particular the common themes of chromatography - spectroscopy combinations, Fourier transform methods and data handling techniques. Each section includes a review of key areas of current research, written by spectroscopists who have made major contributions in their respective disciplines, as well as short reports of new developments in these fields. These common themes have played an increasingly important part in recent advances in spectroscopic techniques and emphasise the multidisciplinary approach of present research. 502 pages ISBN 0 85186 383 3 Price E47.50 ($99.00) ROYAL SOCIETYOF CHEMISTRY Information Services To order or for further information, please write to: Royal Society of Chemistry, Distribution Centre, Blackhorse Road, Letchworth, Herts SG6 lHN, UK. or telephone (0462) 672555 quoting your credit card details. We now accept Access/Visa/MasterCard/EuroCard. RSC Members are entitled to a discount on most RSC publications and should write to: The Membership Manager, Royal Society of Chemistry, Thomas Graham House, Science Park, Milton Road, Cambridge CB4 4WF. U.K.

ISSN:0144-557X    

DOI:10.1039/AP9892600305

出版商:RSC    

年代:1989

数据来源: RSC

摘要:

306 ANALYTICAL PROCEEDINGS, SEPTEMBER 1989, VOL 26 Analytical Viewpoint ~~ The following is a member of a continuing series of articles providing either a personal view of part of one discipline in 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 a t Analytical Division Meetings. Persons wishing to 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 to discuss outline ideas with prospective authors. Development of High Performance Pipette Fillers, Safe Practice in Handling Pipettes and Comparative Calibrations Between Transfer Pipettes and Mechanical Pipettes Osamu Nara Second Department of Analytical Chemistry, Tohoku College of Pharmacy, 4-4- 1, Komatsushima, Sendai, Miyagi 983, Japan Mechanical action micro- and macropipettes for delivery of known volumes of solution in chemical analysis have become popular in recent years.In particular, the present deserved popularity of various chromatographic and atomic-absorption techniques has resulted in the widespread use of microlitre pipettes, with occasional misunderstanding of their proper usage or inherent accuracy and precision. Kratochvil and Motkosky' reported that analytical data obtained by using mechanical-action micropipettes may involve considerable bias unless each tip is individually calibrated by the operator.Emanuel2 also determined the precision of delivery of several of the commonly used micropipettes, and stated that the most expensive micrometer controlled syringe pipette gave the poorest precision at the 1-yl level while a simple capillary type gave the best results at the same volume, concluding that the sample delivery errors are often larger than 10-15%, although with care in usage and proper pipette selection the deviation can be kept below 1%. Conventional glass transfer or measuring pipettes are calibrated by the manufacturer and the capacity tolerances for these pipettes are those accepted by the authorities concerned, e . g . , NBS, JIS or DIN. This applies especially to the volumetric or transfer pipette that has been used to deliver accurately and reproducibly a particular volume of liquid.Competent analysts are well aware of the importance of calibrating the delivered volume of these pipettes, and detailed procedures for this can be found in several text-books on quantitative analysis. In order to attain the degree of precision required in many pharmaceutical assays involving volumetric measurements the appropriate apparatus must be chosen and used with excep- tional care. It has been my experience that the delivery inaccuracy and imprecision of several commonly used, mechanical-action, continuously adjustable, air displacement micro-and macro-pipettes are often a great source of error. It has been the author's recommendation that conventional volumetric pipettes, possessing the best accuracy and preci- sion, can be utilised more effectively, swiftly and safely.On the other hand, many pipette fillers3-24 have been proposed and marketed commercially. The desirability of using some such aid has been stressed from the viewpoint of safety.25 However, none of those devices for filling pipettes was found to be entirely satisfactory and more efficient than filling by mouth suction. Those fillers need the annoying operation of suction and/or the tedious adjustment of liquid level. In many instances the pipette is actually still filled by mouth suction. It is clear that the mouth suction of poisonous liquids, corrosive chemicals, hot solutions, volatile chemicals or odorous sample solutions is extremely dangerous. Further- more, the cancer death rate is significantly higher for chemists.26.27 During some chemical and bacteriological work it becomes necessary to handle dangerous liquids in pipettes quickly and accurately with one hand, as in a hood.From necessity, a few pipetting devices with high operation efficiency have previously been devised by the author.28.29 Furthermore, two types of simple pipette fillers with high operation efficiency have been developed. Experimental Several types of pipettes for macromeasurement were studied. They included: borosilicate glass transfer pipettes with various sizes, 1-100 ml (Sibata, Japan); continuously adjustable air-displacement macropipettes including 1 , 5 , and 10 ml of tip volume [Sibata, SM-1, -5 and -10, Japan (for these types three plastic tips for each volume were evaluated]; and a positive- displacement unit equipped with a 50-ml Combitip (Eppen- dorf, Multipipette 4780: for this type three plastic Combitips, brand new, were evaluated). For the volumetric or transfer pipettes the operating sequence was followed basically by the ordinary method as it appears in analytical text-books: the proposed suction devices were mainly used to pull the liquid into the stem above the calibration mark, and then the right index finger was placed over the top of the stem as the devices were removed.The meniscus was adjusted to the calibration mark by allowing the liquid to flow slowly until the meniscus reached the mark as usual. Any drop hanging to the tip was removed by touching the side of the container. The pipette was then moved slowly to position over or in the receiving container, and the liquid was allowed to drain freely until the last drop fell.After the last drop had fallen, two different draining methods used in the USA and Japan were compared. For the USA method the pipette was allowed to drain for a specified length of time, approximately 15 s, by counting to 15, and the tip was then touched to the side of the container to remove any partial drop which had formed. Thus, some liquid was left in the tip of theANALYTICAL PROCEEDINGS, SEPTEMBER 1989, VOL 26 307 pipette after delivery. For the Japanese method, the last portion formed in the tip was blown out by closing the upper end of the pipette with the right index finger, holding the bulb of the pipette with the left hand palm and touching the tip of the pipette on the side of the container; in the case of 1 ml transfer pipettes this blowing out method was not effective, and the proposed suction bulb pipette filler was used as a rubber bulb.For comparison of the operation efficiency of the pipette filling devices, the classic commercial safety pipette filler and the mouth suction type were employed in their respective ways. The operating procedure for the air displacement pipettes was followed in accordance with the manufacturer’s instruc- tions: the scale was set to the volume to be delivered by turning the volume setting knob. A clean tip was fitted closely on to the end of the pipette, the operating button was pressed to the first stop, and the pipette tip immersed approximately 3-4 mm into the liquid to be pipetted. The button was next allowed to return slowly to its original position. The tip was removed from the liquid by sliding it along the wall of the vessel, in order to get rid of droplets of liquid on the tip.With the pipette held vertically, the contents were immediately delivered into the receiving vessel by touching the tip to the inside wall and slowly pressing the button to the first stop. The button was held in this position for a few seconds to allow the inner wall of the tip to drain, and then pressed slowly to the second stop to eject the last portion of liquid. The pipette was removed from the wall with the button still depressed to avoid drawing liquid back again into the tip. For the positive displacement pipette, the operating pro- cedure was as follows. Set the volume selection dial to the appropriate position.Immerse the tip in the liquid. Fill the pipette by slowly sliding the filling lever upwards. Next, remove the tip from the liquid by sliding it along the wall of the vessel. Discard the first pipetting step for precise pipetting. Check that no droplets of liquid remain on the tip. Then, holding the tip so that it touches the inner side of the receiving vessel, deliver the contents by depressing the pipetting lever completely to the stop. Before use in this study, each glass pipette and plastic pipette tip was carefully cleaned by putting it in a newly prepared detergent overnight (or longer) and then thoroughly rinsing with a generous amount of tap water.The inner surfaces were not allowed to dry prior to use but were well rinsed with a re-distilled water to be measured. After rinsing, glass pipettes were uniformly wet and did not have any drops on their inside walls. In addition, a few glass pipettes, which were not put in detergent at first or were put in detergent overnight but were not very clean, and whose inside walls were not completely wet, were used for comparative calibration purposes as “unclean” pipettes. The accuracy and precision of each pipette were examined Triangular finger ring, stainless-steel wire, adjustable to finger sizes 2 rnm o.d.,2 rnrn long, Connection to water pump, 2 mm i.d. x 4 rnrn 0.d. silicone rubber tubing Silicone rubber tubing, 2 rnm 0.d. Fig. 1. index finger Construction of the pipette filling device attachable to the by weighing the water delivered and inferring the volume from its mass and density.The water was pipetted into 100-ml conical flasks. The containers were stoppered immediately after delivery of each portion. After the buoyancy correction for water weighed in air against steel weights using the equation M = Wair (1.0011), masses of water delivered were converted to volume by dividing by the density of water at the appropriate temperature. A substitution-type single-pan balance (Chyo, SD-200, Japan) was used for the weighings. Zero drift was maintained within kO.0001 g by turning on the light 30 min before use and leaving the light on throughout the repeated weighings. Results and Discussion Finger Attached Pipette Filler A simple pipette filler easily attachable to the index finger, which is a modification of Houghton’s pipette filler,lO that is, essentially, a means of using a suction pump at the finger tip, has successfully been developed. The new version, illustrated in Fig.1, consists of a thin, small, round rubber pad equipped with a projecting suction nozzle, in the centre of the base, which is connected to a source of vacuum by means of polyethylene tubes and a suitable length of capillary silicone rubber tubing, and a triangular wire ring whose base is immersed under the top of the pad. In use, the device is put on so that the pad is just under the first joint of the forefinger. The triangular finger ring can be bent to adapt to various sizes of finger. The water pump is turned on at a moderate rate and the finger is easily brought down on to the top of the pipette, the top of which is placed in the liquid, so that the projecting suction nozzle is put into the top hole of the pipette.As the pad is pressed down lightly, the liquid is automatically sucked up. The rate of filling can be conveniently adjusted by regulating the amount of vacuum and the pressure with which the pipette is held against the pad. It should be noted that an excessive vacuum causes the sucked liquid to bubble in the pipette. When a suitable amount of liquid has been sucked up, the finger is moved so that the top of the pipette is sealed with the finger tip. Adjustment to the calibration mark and free drainage are performed in the usual way. This is illustrated in Fig.2. W I I L ‘ M \-. (4 (6) Fig. 2. Operating procedure of the finger attached pipette filler: ( a ) , pulling the liquid into the pipette; ( b ) , adjusting the meniscus to the calibration mark Many of the above modified pipette fillers have been widely used both in our laboratories and in student’s experiments for some years and found never to be uncomfortable to the forefinger and also to be much easier to handle than the Houghton model using the triangular finger ring, the miniatur- ised rubber pad, the projecting suction nozzle and the capillary308 ANALYTICAL PROCEEDINGS, SEPTEMBER 1989, VOL 26 rubber tubing linking to the vacuum pump. It was especially easy to put the suction nozzle into the top hole of the pipette by using the nozzle as a guide and to move the finger after having finished the suction of liquid.Pipetting work by using this device was performed more effectively than with the mouth- suction method. As the base of the triangular ring is buried inside the rubber pad, the wire ring never comes off with excessive use of the device. The sizes of the pad and the suction nozzle are adaptable enough to make use of 1-200 ml pipettes possible. There is no necessity for the unnecessarily time consuming insertion of the pipette top into the filler, which requires both hands, and the pipette operation can be performed thoroughly with one hand; the other hand is free enough to handle each sample in a different pipette or to operate even in aseptic conditions. This device should be extremely useful in rinsing the pipette and drying its inside wall where different kinds of solutions are to be pipetted and also helpful in preventing the contamination of sample solutions which might be caused by the mouth suction method.Suction Bulb Pipette Filler Another simple pipette filler, which is essentially a suction bulb, easily adaptable to the top hole of any size of pipette, has been successfully developed. As is illustrated in Fig. 3, the unit consists of a conical shaped rubber pad equipped with a projecting suction nozzle, in the centre of the base, which is connected to the rubber suction bulb, and the air relief valve required to repeat the suction for a large-size pipette. Rubber suction bulb I I Air relief valve Conically shaped rubber pad with projecting suction nozzle, easily adaptable to the top holes of 1-200 ml pipettes Fig.3. Construction of the suction bulb pipette filler In use, the conical suction pad is held under the right index finger down into the top opening of a pipette immersed in the liquid so that the projecting suction nozzle is put into the top hole of the pipette. As the rubber bulb is compressed with the left hand and allowed to return, the sample solution is quickly sucked up into the pipette. For a large-size pipette, repeat the bulb squeeze operation. When the liquid has been sucked up above the calibration mark of the pipette, remove the filler with the left hand, close the top of the pipette with the right index finger and control the liquid level as usual. This is illustrated in Fig.4. Many of these pipette fillers have been used in our laboratories for several years and found to be absolutely effective in eliminating the need for mouth suction. By designing the conical pad and suction nozzle, paying attention to their sizes, it was especially easy to fit the suction pad into the top hole of any size (1-200 ml) of pipette with no leak of air, even if the cutting of the pipette top was rough, and to remove the filler after having finished the suction of liquid. This also helped to eliminate the unnecessarily time consuming pro- cedure of attachment of the pipette top to the filler which is required with a classic safety pipette filler. The air relief valve was equipped to facilitate suction in a large-size pipette. Therefore, the pipette operation with this device could be efficiently utilised with one hand except where both hands were momentarily occupied in squeezing the bulb and removing the device after the suction; the other hand was free to handle the sample solution container and the receiving vessel.Lifting and holding the pipette vertically, the adjustment to the mark with a skilful finger tip and the free drainage of liquid by opening the top hole of the pipette is most practical for the laboratory staff. Fig. 4. Operating procedure of the suction bulb pipette filler: ( a ) , adapting the conical suction pad into the top of the pipette and drawing up the liquid by squeezing the bulb; ( b ) , taking the filler away and controlling the liquid level with the index finger as usual This conventional displacement method of the pipette, just as in the calibration operation, is essential to keep the required high reliability of calibrated pipette measurement.Further, for the blow out delivery of 1-ml transfer pipettes, this device was efficiently utilised as a bulb by connecting the conical suction pad into the top of the pipette and squeezing the rubber bulb, closing the air relief valve with the palm of the left hand at the same time. Operation Efficiency With These Devices By using a 50-ml transfer pipette, pipetting operation efficiency in four methods was examined as shown in Table 1. There was a remarkable difference between the times for the entire pipetting operation in the four methods. The pipetting operations with these two developed devices were significantly faster than those completed by mouth suction and with the classic safety pipette filler.It was much too tiresome to pull 50-ml water samples repeatedly by mouth suction: after the twelve repetitions, the operator felt orally as well as physically exhausted. The pipetting operation with the classic safety pipette filler was the most troublesome, requiring three times more operation time than that utilising the developed devices. Simply comparing the mean values of the entire operation time required the following. During the fourteen repetitions, the more the pipetting was repeated, the severer the pain suffered in the thumb and index finger tips used for opening the ball valves to draw liquid and drain. On the other hand, with the proposed devices, liquid was easily and swiftly sucked up into the pipette without any special or troublesome operation except for putting the suction pad over the top hole of pipette and waiting (finger-attached pipette filler) or repeating the bulb squeezings (suction bulb pipette filler) until the com- pletion of liquid suction.In examining the ease of operation of the proposed pipette filling devices, they should prove to be easy, efficient, comfortable, sanitary and a safe alternative to the mouth suction method; the devices may then be recommended for the students and for laboratory staff who use the conventional volumetric pipettes daily in their careful and accurate and precise experiments. By developing these pipette fillers, the author has set up a safety rule which forbids the use of the mouth for pipetting under any condition of macromeasure- ment.ANALYTICAL PROCEEDINGS, SEPTEMBER 1989, VOL 26 ~ ~ ~ ~~~~ Table 1.Comparison of pipetting operation efficiency in four methods Time required for entire pipetting* operation with 50-ml transfer pipettch Classic safety pipette filler? 156 k 263: Mouth suction 72 t 89 Finger-attached pipette filler 51 t 37 56 k 11 Suction bulb pipette filler * Mean k 95% confidence limits. t Purchased from Lab Safety Supply Co.. No. 1442. $ This value. which has already been reported in a previous paper.29 5 Obtained from twelve repeated pipettings. 7 Obtained from ten repeated pipettings. was obtained from the fourteen repeated pipctting operations. Delivery Inaccuracy and Imprecision of Transfer Pipettes and Mechanical-action Pipettes Comparative calibration data on representative types of pipettes in common use are summarised in Tables 2 and 3.Table 2 shows the volumes delivered for 1-100 ml conventional transfer pipettes made of borosilicate glass to be more or less biased from their designated values. For 1-, 5-, 25- and 50-ml pipettes, considerable biases larger than the respective limits of errors accepted by the NBS or JIS were obtained. When using 1-, 5- and 25-ml pipettes, Japanese made and calibrated as the blown-out type by the manufacturer, drainage delivery gave minus biases greater than the MBS limits of errors. In the USA most pipettes are of drainage type, i . e . , they are calibrated to deliver a definite volume after a specified drainage time; thus, some liquid must be left in the tip of the pipette after delivery. On the contrary, most Japanese pipettes, which have an appearance similar to that of the American drainage-type pipettes, are calibrated so that the last portion must be blown out rather than left in the tip.All analysts should be aware that there is this difference between the two countries’ apparatus and the difference could be the cause of error. Especially with l-ml pipette C and 5-ml pipette A , before cleaning the pipettes in detergent many drops of water were found on inner surfaces after delivery, and the precision of their replicate measurements was poor. After overnight cleaning of the same pipettes in detergent, their delivery precision obviously changed satisfactorily.A similar undesir- able result was also obtained in using l-ml pipette B. It is clear that replicate delivery precision for 1-100 ml clean transfer pipettes is quite high. The author recommends that each pipette used be thoroughly cleaned so that the inner surface of the pipette is smoothly wet in order to obtain high precision of measurement, and then calibrated by the operator by weighing the water delivered, in all situations where an accuracy of 1% or better is necessary. From the results of four different suction methods using 50-ml pipettes A and B, it was concluded that no significant difference was noticeable; this implies that these suction devices do not affect the reliability of measurement. Burfield and Hefter33 demonstrated that volumetric glass- ware can be dried at much higher temperatures (320°C) with no significant volume changes.Therefore, after the calibration of volumetric pipettes performed by the operator, oven drying of such apparatus can be employed with little risk of volume changes during the heat - cool cycle. For example, rigorously dry volumetric apparatus is required for handling solutions of moisture-sensitive compounds and for physicochemical measurements in strictly anhydrous non-aqueous solvents. For most practical purposes, oven temperatures in the range 11C1.50 “C should provide efficient drying of glassware with no risk of noticeable volume changes providing that Pyrex or borosilicate glass is the material of construction. In Table 3, results for 1-10 ml mechanical-action pipettes are presented.When using l-ml air-displacement pipettes equipped with tip A or B, delivered volumes were more than 10% beyond the nominal value in spite of having set the volume scale precisely 1 ml in advance. After tip C was equipped and the volume pointer was moved once and then re-set at the same volume, the bias of the delivered volume changes prominently. Similar undesirable results were Table 2. Calibration data for conventional glass transfer pipettes Volume/ml Converted from weight of Precision, Bias, Limit of Designated water delivered* YO YO error, YO + 1 Pipette A 1.0019 f 0.0017$ k0.17 +O. 19 0.60 (1.00) B 0.9930 f 0.0056$,$ 0.56 -0.70 1.0070 k 0.0024$ 0.24 t-0.70 { 0.9860 f 0.012217,II 1.24 -1.40 5.0052 t 0.0007$ 0.01 +O. 10 0.20(0.40) ’lpette A { 4.9804 f 0.01167,II 0.23 -0.39 10 9.9925 k 0.0056$ 0.06 -0.08 0.20 (0.20) 24.9915 f 0.00603: 0.02 -0.03 0.12 (0.12) 49.9163 k O.OOOS,$,** 0.02 -0.17 0.10 (0.10) 24.9672 f 0.01111 0.04 -0.13 49.916, k 0.0108$,tt 0.02 -0.17 49.9188 t 0.0054$,3:3: 0.01 -0.16 49.9266 k 0.0257$,tt 0.05 -0.15 49.9203 k 0.013,$.$$ 0.03 -0.16 25 P i p c t t e ~ { 100.03, k 0.009$ 0.009 +0.03 0.08 (0.lo) 100.00~ -t 0.004q 0.004 +0.00, .1 100 pipette^ { * Mean confidence limits. f Values accepted by the National Bureau of Standards” and in parentheses by the Japanese Industrial Standard.” 2 Used as the blown-out type pipette, liquid was not left in the tip of the pipette after delivery. 9 With the pipette put in detergent overnight but not very clean. A few droplets of water were found on the inside wall of the pipette tip fl Used as the drainage-type pipette.some liquid was left in the tip after delivery. 11 With the pipette not cleaned in detergcnt. Many drops of water were found on inner surface of the pipette after delivery. ** With the classic safety pipette filler (Lab Safety Supply Co., No. 1442). t i By mouth suction. $3: With finger attached pipette filler. $9 With suction bulb pipette filler. after delivery.310 ANALYTICAL PROCEEDINGS, SEPTEMBER 1989, VOL 26 ~~~ Table 3. Calibration data for mechanical-action pipettes with plastic tips Volume/ml Converted from weight of water Precision, Bias, Setting delivered* % % Air-displacement pipettes- 1 Tip A 1.1072 k 0.00097 k0.08 + 10.72 B 1.1034 k 0.00207 0.18 +10.34 C 1.0059 k 0.00lOl 0.10 +0.59 5 Tip A 5.4299 k 0.01369 0.25 +8.60 B 5.4195 k 0.01029 0.19 +8.39 C 4.9761 k 0.0299$ 0.60 -0.48 10 Tip A 10.0950 -t 0.01441 0.14 +0.95 B 10.0439 k 0.01161 0.12 +0.44 C 9.9512 k 0.0341l 0.34 -0.49 Positive-displacement pipette- 5 Combitip A 5.0061 k0.0052 0.10 +0.12 B 5.0048 -t 0.0073 11 0.15 +0.10 C 5.0123 k 0.0035 1) 0.07 +0.25 * Mean +95% confidence limits.7 Two means differ significantly at the 99% level. $ Scale was moved and re-set to the same volume to be delivered. 9 Differ significantly at the 80% level. 1 Differ significantly at the 99.9% level. /I Differ significantly at the 95% level. obtained also in use of 5- and 10-ml air-displacement pipettes, in which the problems were believed to be the result of the mechanical imprecision in the volume setting system; this convinced the author that the delivery error associated with the readjustment of the pointer to a marked volume line could be a greater uncertainty of the stated nominal volume than expec- ted.Further, it should be noted that the delivered volumes for 1-, 5- and 10-ml air-displacement pipettes significantly changed by 0.4, 0.2 and 0.5%, respectively, from tip A to tip B against the fixed volume setting. It is concluded that for each tip, or at any volume setting, calibration is essential in order to perform accurate measurement; however, the calibration for each tip and at each volume setting would be troublesome and impractical. Considering the merit of the disposable tips and the variation of their delivery volumes, the air-displacement pipettes might be difficult to use for precise quantitative analysis owing to their expense.The delivery precision for the 1-ml air displacement pipette was satisfactory for the small delivery volume. This was believed to be the result of the inner surface effect of hydrophobicity of plastic tips. However, the delivery precision for 5- and 10-ml air-displacement pipettes was not very satisfactory, much worse than that for the clean-transfer pipettes of the same volumes, and also varied from tip to tip. When using brand new Combitips, positive-displacement pipettes were found to be easy and safe to operate, and were satisfactory with reference to their delivery precision and accuracy; however, it should be noted that there was a significant difference between the delivered volumes for Combitips B and C.Furthermore, it is uncertain how long a plastic Combitip, whose material might be affected by organic solvents, will keep its original precision and accuracy of delivery for replicate use, i . e . , pistoning. Eppendorfs operat- ing instructions say that an excessive number of air bubbles seen when filling the Combitip, dripping Combitip, or the like, is a result of a leaking Combitip and requires the replacement of the Combitip with a new one; careful analysts should be aware that the need exists to determine the delivery precision and accuracy of each Combitip before use. The author is greatly indebted to John C. Fisher at the Tohoku College of Pharmacy for his kindness in reviewing the English expressions in this manuscript.References 1. Kratochvil, B., and Motkosky, N., Anal. Chem., 1987,59,1064. 2. Emanuel, C. F., Anal. Chem., 1973, 45, 1568. 3. Douris, R., Perrenot, A., and Carlsson, B.. Bull Sci. Phar- 4. Backus, R. C., Anal. Chem., 1957, 29, 167. 5. Behrman, A. S. J., Znd. Eng. Chem., 1917, 9, 1047. 6. Singer, A. A., and Jacobs, M. B., Anal. Chem., 1948,20,496. 7. Fuscoe, F. J., Lab. Pract., 1976, 25, 85. 8. Linetskii, M. G., Russian Put., 1938, 53, 748. 9. Schneider, W. G., Znd. Eng. Chem., Anal. Ed., 1943, 15, 764. macol., 1927,34, 203. 10. Houghton, A. A., Chem. Znd. (London), 1944, 20, 193. 11. Sievers, D. C., Anal. Chem., 1947, 19, 144. 12. Brinton, D. B., Anal. Chem., 1948, 20, 186. 13. Dybkaer, R., Scand. J. Clin. Lab. Invest., 1957, 9, 201. 14. Mathis, W. T., US Pat., 1944, 2 358 936. 15. Kimura, S., Kagaku (Kyoto), 1960, 15, 327. 16. Mishima, K . , Kagaku To Kogyo (Tokyo), 1960, 13, 766. 17. Ceausescu, D., Rev. Chim. (Bucharest), 1964, 15, 699. 18. Dodd, G. A., and Cassen, T., J. Chem. Educ., 1974, 51, 467. 19. Racusen, D. J., Chem. Educ., 1975, 52, 386. 20. Schneider, O., Gliickauf, 1939, 75, 580. 21. McCrackan, R. F., andpassamaneck, E., J. Chem. Educ., 1928, 5, 343. 22. McCrackan, R. F., J. Chem. Educ., 1929, 6, 733. 23. Scheflan, L., J. Chem. Educ., 1929, 6, 114. 24. Rees, T., J. Chem. Educ., 1976, 53, 502. 25. Toone, G. C., Ferber, K. H., and Flett, L. H., Chem. Eng. News, 1946,24, 902. 26. Rawls, R. L., Chem. Eng. News, 1976, 54, 17. 27. Li, F. P., J. Nut. Cancer Znst., 1969, 43, 1159. 28. Nara, O., and Otomo, M., Kagaku To Kogyo (Tokyo), 1976, 29, 1012. 29. Nara, O., Bunseki Kagaku, 1980, 29, 720. 30. Guenther, W. B., “Quantitative Chemistry: Measurement and Equilibrium,” Addison-Wesley Publishing Company, London, 1968, pp. 5 , 6, 304, 305. 31. Hughes, J. C., “Testing of Glass Volumetric Apparatus,” NBS Circular 602, April 1, 1959, and COM-73-10504, National Technical Information Service, p. 8. 32. “Glass Volumenometer for Chemical Use,” JIS R350.5-1976, 33. Burfield, D. R., and Hefter, G., J. Chem. Educ., 1987,64,1054. p. 4.

ISSN:0144-557X    

DOI:10.1039/AP9892600306

出版商:RSC    

年代:1989

数据来源: RSC

摘要:

ANALYTICAL PROCEEDINGS, SEPTEMBER 1989, VOL 26 311 Signal Processing in Molecular Spectroscopy ~ ~~~~ The following is a summary of one of the papers presented at a Joint Meeting of the Analytical Division and the Molecular Spectroscopy and Chemometrics Groups held on December 1 st, 1988, in the Scientific Societies’ Lecture Theatre, London W.l. Fourier Transforms in Spectroscopy-a Chemometric Approach Richard G. Brereton School of Chemistry, University of Bristol, Canrock’s Close, Bristol BS8 1 TS Fourier transforms have been used in molecular spectroscopy for over 20 years. There are many texts and reviews14 describing the use and mathematics of Fourier transformation to which the interested reader is referred for technical details. The purpose of this article is to describe how the chemometric approach can aid the molecular spectroscopist.Most of the early Fourier transform spectroscopists were instrument builders. One of the earliest applications of Fourier transform techniques in spectroscopy was to nuclear magnetic resonance studiess; the main advantage of Fourier transform instrumentation is that useful data can be acquired much faster than by using conventional, continuous wave methods. However, most of the early Fourier transform spectroscopists took their ideas from engineers who had applied such methods in electrical circuitry for very many years. Early Fourier transform spectrometers did not come equipped with discs and sophisticated computers, so the transform of the time series had to be viewed and/or plotted on-line. This meant that there was only limited scope for the application of sophisticated methods of data processing.Analogously, much work had been performed on filtering visual and audio information in order to improve radio, television and other media. A signal had to be processed in real time, often using circuits rather than computers. Some early methods involved employing on-line filtering functions to improve sensitivity andor resolution, but apart from that the spectroscopist normally restricted his approach to direct visualisation of data. By contrast, statisticians have worked on methods for time series analysis for many years. Classical work by Box and co-workers637 forms the basis of modern approaches to time series analysis.8.9 Formally, statisticians refer to any sequential data set as a time series.A method such as spectral analysis can be defined as the Fourier transformation of correlograms. It is, therefore, strictly possible to take a spectrum of the long term intention of voters, of the retail price index, of the concentra- tion of compounds in a geological core, or indeed of an electrical circuit. In most of these cases data collection is expensive compared with analysis. A long term economic trend consisting of 100 measurements might involve many man-years work, in contrast to an NMR spectrum or a mass spectrum that might typically be recording in seconds. Therefore, statisticians found it worth developing sophisticated off-line computational approaches for the analysis of such data. These approaches involved examining the nature of the noise, the nature of sampling errors, using information on the nature of the signals and the questions to be asked from the data.Thus, there is a battery of techniques available, developed in other branches of science. Can the chemometrician use these methods to best advantage? The Role of Chemometrics Chemometrics in its broadest sense (the application of compu- tational and statistical methods to laboratory based experimen- tation) has special features that distinguish it from other statistical disciplines, and it is not possible to import methods developed in other areas of applied statistics directly and expect these to work for the chemist without some fine tuning. In chemistry experimentation is relatively cheap. For example, if the signal to noise ratio of a spectrum is low, it is possible to time average more spectra to improve the signal to noise ratio.Geological, economic, and in most instances biological, processes are often unique and it is often impossible or difficult to repeat such measurements. So, it might be worth investing several man-months exploring the trends in one data set alone. The chemist would probably repeat the experiment again, so analysis must be balanced against experimentation. However, nearly all modern spectrometers have extensive disc, and often tape, storage. On-line processing is fast. There is a trend towards readily programmable second processors and data transfer between different computers is fairly facile. Therefore, greater flexibility is possible and chemists are slowly exploiting chemometric approaches toward Fourier transform signal processing. Spectroscopic Problems and How They Can be Solved Many questions can be asked of spectroscopic data.Some of the questions asked and possible solutions are listed below. Is a peak present or not? This is essentially a problem of enhancing signal to noise ratios. Is there enough evidence for us to be confident that a given “blip” in a spectrum represents a real peak, or is it caused by noise? (i) Image processing and information theoretical methods, such as the maximum entropy method,10 are increasingly of interest. These methods are particularly suited to Fourier transform data. (ii) There is a large literature in the area of Fourier filters. By multiplying a time series by a function that suppresses the noise but retains the signal, intensities in the resultant transform are increased.Optimal filters depend, though, on the knowledge of noise and signal distributions and should be used with caution: the more that is known about the data the more optimal the filter, but if everything is known about the data there is no point in applying such filters. (iii) Time series (spectral) analysis.69 By using this approach it is possible to calculate confidence as to whether peaks are present or not. It is important to recognise that standard methods used by analytical chemists often assume an infinite312 ANALYTICAL PROCEEDINGS, SEPTEMBER 1989, VOL 26 number of samples and Gaussian noise and may not be applicable to all types of spectroscopy.( i v ) Smoothing functions. It is not necessary to work in the Fourier (time) domain; direct moving averages can be employed. These approaches, such as the Savitsky - Golay filter,l’ are normally best when there is limited knowledge about peak-shape and noise functions. If there is detailed peak shape knowledge (e.g., NMR) working in the time domain is preferred. How many peaks are present in a “hump”? This is a problem of resolution enhancement. Fourier trans- form methods complement multivariate approaches, such as factor analysis and multivariate calibration. ( i ) Fourier filters. These are similar in principle to filters used for sensitivity enhancement as described above. These filters can be best understood by the convolution theorem.12 In many sophisticated cases non-linear deconvolution can be employed.Most simple approaches to filtering involve using deconvolu- tion functions that, mathematically, can result in physically meaningless spectra, for example, negative peaks. Non-linear approaches allow constraints to the solution. They are often very computationally intensive. (ii) Derivatives. These can be applied directly to the spectrum. They require little knowledge of peak shapes and often strongly amplify noise. Often, though, they can be combined with smoothing functions. (iii) Constrained minimisation. This is also often referred to as curve fitting, and, sometimes, incorrectly, as deconvolution. The number of components can be estimated by using peak-shape models. Statistics such as x* or ANOVA are also used to estimate convergence of the model.What is the integral of a peak? This is probably one of the most frequently asked questions of spectroscopic data. Many factors need to be taken into account, such as ADC (analogue to digital conversion), sampling rates, base-line correction and so on, in order to estimate the error in integrals. There are no specific Fourier transform methods, except that it is essential to appreciate that methods used to enhance sensitivity or resolution can cause serious distortions to peak shapes and thus quantitative parameters. Many workers forget this and some tabulated integral data is probably more dependent on the method of data processing than the underlying chemical factors. Indeed, the potential to lose accurate integral information in Fourier transform spectroscopy is a major disadvantage of such techniques.All Fourier transform spectra have been “mas- saged” and often sampling is fairly sparse. Straightforward continuous wave spectra do not suffer from such disadvan- tages. Therefore, if the objective of a Fourier transform spectroscopic experiment is to calculate integral intensities some care must be taken as to the method of acquiring and processing data. Conclusion In conclusion, the chemometric approach has yet to be widely applied to Fourier transform molecular spectroscopy. With the advent of modern computing power and an awareness that chemometrics is not merely statistics in chemistry, these approaches could become powerful aids to the practising spectroscopist. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. References Griffiths, P. R., Editor, “Transform Techniques in Chem- istry,” Heyden, London, 1978. Marshall, A. G., Editor, “Fourier, Hadamard and Hilbert Transforms in Chemistry,” Plenum, New York, 1982. Remirez, R. W., “The FFT, Fundamentals and Concepts,” Prentice-Hall, Englewood Cliffs, NJ, USA, 1985. Brereton, R. G., Chemometr. Intelligent Lab. Syst., 1986, 1, 17. Ernst, R. R., Adv. Magn. Reson., 1966, 2, 1. Box, G. E. P., and Jenkins, G. M., “Time Series Analysis, Forecasting and Control ,” Holden-Day , San Francisco, USA, 1970. Jenkins, G. M., and Watts, D. G., “Spectral Analysis and Its Applications,” Holden-Day, San Francisco, USA, 1968. Chatfield, C., “The Analysis of Time Series: An Introduction,” Third Edition, Chapman and Hall, London, 1984. Brereton, R. G., Chemometr. Intelligent Lab. Syst., 1987, 2, 177. Skilling, S., Sibisi, S . , Brereton, R. G., Laue, E. D., and Staunton, J., Nature, 1984, 311, 466. Savitsky, A., and Golay, M. J. E., Anal. Chem., 1964, 36, 1627. Jansson, P. A., Editor, “Deconvolution with Applications to Spectroscopy,” Academic Press, New York. 1984.

ISSN:0144-557X    

DOI:10.1039/AP9892600311

出版商:RSC    

年代:1989

数据来源: RSC

摘要:

ANALYTICAL PROCEEDINGS. SEPTEMBER 1989. VOL 26 313 Flow Analysis Methods The following are summaries of four of the papers presented at a Meeting of the Analytical Division held on February 8th and 9th, 1989, in the Scientific Societies' Lecture Theatre, London W.1. Recent Advances in Detection in Flow Injection Systems M. Valcarcel and M.D. Luque de Castro Department of Analytical Chemistry, Faculty of Sciences, University of Cordoba, Cordoba, Spain In the last few years interesting and promising novelties have been introduced in flow injection analysis, FIA.1-3 These innovations can be categorised according to the four essential parts that make up a flow injection manifold: firstly, the propulsion system ( e . g . , use of computer controlled pumps); secondly, the sampling system ( e .g . , direct introduction of solid and heterogeneous samples and the adaptation of FIA to online process monitoring); thirdly, the transport-reaction system ( e . g . , new approaches to continuous separations and advances in solid-phase reactors); and fourthly, the detection system, the subject matter of this paper. Before describing these novelties, it is interesting to note that there are two approaches in the analytical literature to describing the role played by the detector in flow injection analysis (Fig. 1). FIA researchers used to consider the detector as a mere module of the unsegmented flow injection configura- tion. Other authors consider FIA to be no more than a means of introducing samples into analytical instruments. Which of the two views is the more accurate? In fact, both are appropriate to describe the facts, which are nevertheless distorted from the two points of view.FIA manifold I nst ru men ta I technique Fig. 1. FI A Different points of view of the role played by the detector in New Types of Detectors Most of the detectors used in FIA (over 70%) are optical, and about one third (29%) are electrochemical. The use of atomic detectors (both AAS and ICP) and the development of chemiluminescence methods are two areas of growing interest. In the last few years novel types of detectors (enthalpimetric, thermal lens, Fourier transform IR, mass spectrometric) have been used in FIA systems. In amost every case the advantages derived from introducing samples into these detectors by FIA are those typically offered by this technique.Repetitive Passage of the Reaction Plug Through the Detect or Flow injection analysis can be endowed with a highly dynamic nature by repeatedly passing the reacting plug through the flowcell of a non-destructive detector. There are two main technical approaches to performing this process. In the open - closed circuit approach4 a selecting valve allows the injected plug to be trapped within a closed circuit containing an additional pump and a flow-cell. The second possibility involves the iterative reversal of the flow direction, which can be accomplished by programming the functioning of the peristaltic pump with a home-made cycle programmer or a computer .5 One multi-peak recording per injected sample is obtained by both approaches.The profiles of the maxima and minima are typical kinetic curves describing both physical and chemical processes. Interesting analytical methodologies can be derived from these recordings. The most relevant are: calculation of reaction rate and thermodynamic constants; determination of stoicheiometry; development of reaction-rate methods (includ- ing differential kinetic determinations); calculation of viscosi- ties; and automatic amplification of the analyte concentration range. Placement of the Detector in the Injection Valve The detector is normally placed at the end of the FIA system, after the pump, the injection valve and the reaction coil. Some authors place a reference electrode in the loop of the injection valve for electrochemical detection (Fig.2). Recently, our research team6 proposed the use of a single detection point located in the centre of the loop of an ordinary injection valve, which inserted a fresh plug of organic phase into an aqueous sample stream synchronised with the iterative reversal of the flow direction, in order to develop continuous liquid - liquid extraction processes without the use of continuous separation devices ( e . g . , membrane, T-type, density type). This is one of the major sources of problems in the continuous manifolds developed so far. The detector monitors the gradual enrich- ment of the organic phase with the solute initially contained in the aqueous carrier and a multi-peak recording is obtained. The effective area of contact between phases is substantially increased thanks to the formation of an organic film wetting the PTFE walls of the loop.The appearance of parasitic signals3 14 ANALYTICAL PROCEEDINGS, SEPTEMBER 1989. VOL 26 Integrated Reactioaetention and Detection A recently developed approach to chemical (and biochemical) sensors not using conventional probes involves the immobilisa- tion on a support located in the flow-cell of an unsegmented- flow manifold of each of the ingredients of a chemical or biochemical reaction, namely: the analyte ( e . g . , amines, using CIS beads as support12); the reagent [ e . g . , 4-(2-pyridylazo)- resorcinol (PAN) immobilised on cation exchangers for determination of traces of copper131; the catalyst ( e . g . , alcohol dehydrogenase immobilised on CPG beads for determination of ethanollj); the reaction product ( e .g . , the iron - thiocyanate complex, using an ordinary anion-exchange resin as supportls). The immobilisation can be temporary (analyte or reaction product) or permanent (reagent or catalyst). The analytical reaction develops in different places, namely: on the support, when this retains the analyte or the reagent; in the solution held in the flow cell, when the catalyst is immobilised, and in the manifold coil, when the reaction product is the immobilised species. In these systems, reaction and/or retention are simultaneous with photometric or fluorimetric detection. In this way it is possible to develop new, promising analytical methodologies such as the following. Firstly, kinetic pre-concentration methods based on the measurement of the slope of the rising portion of the analytical signal, which allows the obtaining of good determination limits ( e .g . , 2 ng ml-1 of iron using thiocyanate as reagent) without the need to introduce the large sample volumes typically used in pre-concentration methods. Secondly, photometric and fluorimetric reaction-rate measure- ments using immobilised enzymes that avoid matrix effects, which is not feasible with conventional packed enzyme reactors. U U Fig. 2. Location of the detector in flow injection configurations resulting from changes in the refractive index or viscosity is avoided as the interfaces do not pass through the flow cell at any time. A methanol stream is required to wash the system between successively inserted samples.The envelope of the maxima and minima of the multi-peak recording obtained are kinetic curves describing the mass transfer across the interface and the diffusion within the organic phase, respectively. The new methodology was successfully applied to the determination of anionic surfactants in waters based on the formation of ion pairs with a bulky coloured organic cation (methylene blue), extraction into chloroform and photometric monitoring of the organic phase. The results found agreed well with those obtained by the manual extraction method using the same chemical system.6 The unusual placement of the detector in the injection loop permits the continuous monitoring of extraction processes from their early stages and allows one to establish differences in extraction rates between solutes, which is not feasible with other extraction devices.Thus, it is possible to establish kinetic differences between anion analytes (iodide, perchlorate, nit- rate, thiocyanate, picrate, tetraphenylborate, etc.) forming ion-pairs with the cationic ferroin chelate that are extractable into nitrobenzene. The rate of the extraction process is related to the analyte size (relative molecular mass). On the basis of these kinetic differences it is possible to determine binary mixtures of these anions by applying conventional differential reaction-rate approaches.’ Use of Fast Detectors The use of detectors capable of rapidly providing various types of data (absorbance, fluorescence, current intensity) at differ- ent instrumental parameter values (wavelength, applied poten- tial, etc.) endows FIA with a doubly dynamic character and affords three-dimensional information.One peak per moni- tored instrumental parameter can be obtained. A rapid data acquisition system ( e . g . , a computer) is mandatory in this context. Both optical (fast-scan monochromator, image detec- tors or Fourier transform alternatives) and electroanalytical (cyclic voltammetry and integrated multi-electrode array configurations) systems are used. There are two types of applications of FIA systems with fast detectors. On the one hand, it is possible to develop multiple determinations of several analytes in the same sample based on the different contribution of each to the signal at different instrumental parameters. Such is the case with the determina- tion of iron - copper8 and orrho-, rneta- and para-cresolg mixtures using a photometric diode array detector, and with the determination of a mixture of three phenol derivatives using FIA - cyclic voltammetry.10 Conversely, it is possible to amplify the conventional analyte range by several orders of magnitude by manipulating the data stored by a computer, which is of primary practical importance to routine control ( e .g , determination of nitrites8 and formaldehyde11 in waters). Conclusions The different approaches to detection in flow-injection systems described in this paper clearly show that it is possible to develop new analytical methodologies improving valuable analytical properties (Fig. 3) such as the following. Sensitivity Selectivity Ra pid i ty k t f systems reaction Detection Precision for the resolution of real problems Fig.3. detection in FIA Analytical features improved by using novel approaches to Selectivity. Multiple determinations using fast detectors or the elimination of matrix effects using integrated reaction - detection systems. sensitivity. Development of kinetic pre-concentration proce- dures with integrated reaction - detection configurations and automatic manipulation of the analyte concentration range to suit it to each sample by repeatedly passing the plug through a conventional detector or using fast detectors. Rapidity. Multiple determination with a single sample injection using a fast detector or pre-concentration with small sample volumes. Precision. Determination of low levels of analytes, the p.p.b.range, with RSDs not higher than 3 4 % by using integrated reaction - detection systems and automatic dilution proce- dures.ANALYTICAL PROCEEDINGS. SEPTEMBER 1989. VOL 26 Scope of application. Determination of kinetic and ther- modynamic constants, stoicheiometries and viscosities by using multi-peak recordings; differential kinetic determinations of anion mixtures based on liquid - liquid extraction without phase separation. Suitability for the resolution of real problems in different fields. Environmental control (multiple determination of phenols in waters), clinical chemistry (pre-concentration from small sample volumes) and food chemistry (direct photometric determination of iron in different types of wines, v i z ., rose, white and red), etc. References 1. 2. Lazaro. F.. Luque de Castro, M. D., and Valcarcel. M.. J. Pharm. Biomed. Anal.. 1988. 6. 585. Valcarcel. M.. and Luque de Castro. M. D.. “Flow Injection Analysis: Principles and Applications.” Ellis Horwood. Chichester, 1987. RfiiiZka, J., and Hansen. E. H.. “Flow Injection Analysis.” J . Wiley. New York. 1988. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 1s. 315 Rios. A.. Luque de Castro. M. D.. and Valcarcel. M., Anal. Chem.. 1985.57, 1803. Rios. A.. Luque de Castro. M. D., and Valchrcel. M., Anal. Chem., 1988, 60. 1540. Caiiete. F., Rfos. A.. Luque de Castro. M. D., and Valcarcel. M.. Anal. Chem.. 1988, 60. 2354. Cafiete. F.. Rfos. A.. Luque de Castro, M. D.. and Valcarcel, M.. Anal. Chim. Acta. in the press.Lazaro. F.. Rfos, A., Luque de Castro. M. D.. and Valcarcel. M., Anal. Chim. Acta, 1986. 179, 279. Bermudez, B.. Lhzaro. F.. Luque de Castro. M. D.. and Valcarcel, M., Analyst, 1987. 112, 535. Cafiete, F.. Rios. A.. Luque de Castro, M. D.. and Valchrcel, M.. Anal. Chim. Acta, 1988, 211, 287. Rfos. A., Lazaro. F.. Luque de Castro, M. D., and Valcarcel, M.. Anal. Chim. Acta, 1987, 199, 15. Fernandez-Band. B.. Lazaro. F., Luque de Castro, M. D.. and Valcarcel, M., unpublished results. Lazaro. F.. Luque de Castro, M. D.. and ValcArccl, M.. Anal. Chim. Acta. 1988. 214, 217. Linares. P.. Luque de Castro, M. D.. and Valcarcel, M., Anal. Chem., in the press. Lazaro, F.. Luque de Castro. M. D.. and Valcarcel, M.. Anal. Clrim. Acta. 1989, 219. 231. Ion Pairing Flow Injection Extraction M.Harriott and D. Thorburn Burns Department of Pure and Applied Chemistry, The Queen’s University of Belfast, Belfast BT9 5AG The theoretical basis of ion pairing solvent extraction has been reviewed earlier,lJ the process being considered to take place in two main stages: firstly, the simultaneous transfer of free anions and cations from an aqueous phase to an organic phase; and secondly, the formation of ion pairs in the organic phase. The cationic reagents involved are usually onium salts or basic dyes. In manual procedures a separating funnel is used for mixing and phase separation and the over-all procedure requires several minutes to perform. If a large number of samples have to be analysed the process then becomes too labour and time consuming, it also results in a large reagent consumption and a risk of cross-contamination of samples.Flow Injection Extractions To increase the speed of analysis, and to improve accuracy and signal sensitivity, various injection extraction systems have been designed. The system in Fig. 1 is simple to construct, inexpensive and has proved reliable over long periods of use. / 3 U Fig. 1. Schematic diagram of the flow-injection system as for the extraction of perchlorate: (I), carrier solution (buffer solution pH 6) at 0.95 ml min-l; (2), reagent solution (0.005% Brilliant Green at 0.85 ml min-l); (3), extraction solvent (benzene at 0.65 ml min-l): (4), sample injector (250 PI); (5), mixing point (“Hex”); (6), mixingcoil(20 cm, 0.5 mm id.); (7), segmenter (“Tee”); (8), extraction coil (200 cm, 0.5 mm i.d.); (9), phase separator; (lo), restrictor coil; (ll), aqueous waste; (12), spectrophotometer (640 nm); (13), recorder; (14), organic waste at 0.68 ml min-’ The essential components3-4 are as follows.1. A mixing chamber to converge and mix incoming streams. 2. A segmenter to produce identical alternative segments in the stream. 3. A phase separator to split the segmented stream into aqueous and organic phases. 4. A flow cell and detector to detect and measure the resultant analyte signals. The phase separator is the most critical component in the system5.6; the separator developed by Al-Wehaid,’ containing a 1-pm pore size PTFE nylon backed membrane (Zefluor, Gelman Sciences), was adopted in the present series of studies.Applications For each analyte the systems were optimised for the effects of variation of the volume of sample injected, the concentration and flow-rate of carrier reagents and the volume ratio of the organic phase to aqueous phase, and an interference study was carried out. Procedures have been developed for the following problems. Perchlorate in potassium chlorat8 Perchlorate (s2.5 pg ml- 1) was determined spectrophoto- metrically at 640 nm after the extraction into benzene of its ion associate with Brilliant Green.9.10 The detection limit was 36 ng ml-1, based on 250 p1 injections. The system was applied to the determination of perchlorate in potassium chlorate (impor- Table 1. Determination of perchlorate in potassium chlorate Perchlorate found, % m/m Sample Direct method Standard addition 8.78 k 0.30 x lO-d* 8.74 k 0.27 x 2.36 f 0.05 x 10-4 2.33 k 0.09 x 10-d AnalaR AnalaR (BDH) Laboratory grade (BDH) 0.222 k 0.006 0.235 f 0.011 (Hopkin and Williams) * Mean standard deviation for 5 replicates.316 ANALYTICAL PROCEEDINGS.SEPTEMBER 1989. VOL 26 tant in the manufacture of pyrotechnic compositions) after prior selective destruction of chlorate by evaporation with concentrated hydrochloric acid, the results being summarised in Table 1. Manganese in steels Permanganate was determined spectrophotometrically at 545 nm following extraction into chloroform of the ion associate, ethylenebis( triphenylphosphonium) permanganate. 10-12 The carrier stream was pH buffer containing 10% (mlm) am- monium fluoride and the reagent stream was 0.25% (mlV) ethylenebis(tripheny1phosphonium) bromide. The injection rate was 24 h-1.The calibration graph was linear up to 25 pg ml-1 and the detection limit was 0.58 pg ml-1 o f manganese(VII), based on 250-pI injections. The results when the system was applied to the determination of manganese in a range of steels are given in Table 2. Table 2. Determination of manganese in certified steels Manganese content. YO mlm Steel N o . Ce rt ificd* Foundt BCS 456 0.17 (0.17-0.18) 0.167 f 0.001 45711 0.30 (0.29-0.30) 0.296 f 0.001 43511 0.41 (0.40-0.42) 0.412 f 0.003 458 0.42 (0.424.43) 0.420 f 0.004 408 0.64 (0.634.65) 0.636 f 0.004 4601 1 0.67 (0.66-0.68) 0.672 f 0.010 2 1913 0.74 (0.73-0.75) 0.747 f 0.010 21412 1.61 (1 39-1.62) 1.612 f 0.009 * Certified range in parentheses.t Mean 95% confidence limits for 5 replicates. Cobalt in a range of tool steels13 Cobalt (0-10 pg) was determined spectrophotometrically at 625 nm after extraction into chloroform of the ion associate, ethylenebis( tripheny1phosphonium)tetrathiocyanatocobalt- ate(II).1“1s The carrier stream was 10% mlV ammonium fluoride as masking agent and the reagent stream contained 0.5% mlV ethylenebis(triphenyIphosphonium)bromide and 5% mlV ammonium thiocyanate. It was necessary to use a mixing chamber as segmenter to avoid problems from in-line precipitation. The sampling rate was 20 h-1. The calibration graph was linear up to 20 pg ml-1 and the detection limit was 0.23 pg ml-1 of cobalt, based on injection volumes of 500 pI. The system has been applied to the determination of cobalt in a range of tool steels; the results are given in Table 3.Table 3. Determination of cobalt in high speed tool stcels Cobalt content, YO mlm BCS 22012 0.32 ( 0.31-0.33) 0.330 f 0.007 48 1 0.21 ( 0.19-0.22) 0.219 f 0.002 482 0.24 ( 0.21-0.27) 0.254 f 0.006 483 1.94 ( 1.90-1.99) 1.944 f 0.010 484 10.20( 10.10-10.39) 10.25) f 0.10 485 5.06 ( 5.00-5.11) 5.07 f 0.02 Steel No. Certified* Found? * With certified range in parentheses. f Mean 95% confidence limits for 5 replicates. Bismuth in pharmaceutical form ulutions The method of determining bismuth was based on the reaction between bismuth and potassium iodide to form the yellow colour of tetraiodobismuthate(II1) complex.17 This method is subject to numerous interferences, many of which can be overcome by prior precipitation18 or ion pairing solvent extraction 19-33 of bismuth.Bismuth can be determined spectrophotometrically at 495 nm, after its extraction as tetramethylenebis( triphenylphos- phonium)tetraiodobismuthate( 111) into dichloromethane. The carrier stream contained 2 M sulphuric acid and the reagent stream contained 2% mlV potassium iodide and 0.4% mlV te t rame t hylene bis( triphenylp hosphonium) bromide. The sam- pling rate was 20 h- l. The calibration graph was linear up to 20 pg ml-1 of bismuth and the detection limit was 0.24 pg ml-1, based on injection volumes of 250 pl. The interferences of diverse ions (sodium, calcium and zinc) that are generally found in pharmaceutical formulations were less than 2% at concentration ratios of 100 : 1.The system has been applied to the determination of bismuth in pharmaceutical formulations, after digesting the samples with 10 ml of 72% perchloric acid and 10 ml of hydrogen peroxide. The results, Table 4, are in good agreement with those obtained by atomic absorption spectrometry. ~~ Table 4. Determination of bismuth in pharmaceutical formulations Bismuth foundlmg Bismuth Sample labellmg FIA* AASf Bismuth carbonate Bismuth carbonate Bismuth subgallate tablet (1 tablct) 10.65 10.43 k 0.21 11 .(lo ? 0.07 suspension (1 ml) 49.17 50.73 f 0.80 50.45 f 0.32 ointment ( 1 .(MI g) 19.83 19.72 f 0.22 19.46 2 0.13 * Mean standard deviation for 5 analyses. t 95% confidence limit for 10 rcplicates. Conclusions The automated ion pairing solvent extraction methods, based on the flow-injection principle, allow rapid and simple determi- nations of, for example, perchlorate, manganese, cobalt, and bismuth ions.These methods were also found to be more sensitive and stable than their conventional counterparts. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. References Fogg. A. G.. Burgess. C.. and Burns. D. T.. Talanru, 1971, 18. 1175. Burns, D. T.. Anal. Proc.. 1982. 6. 355. Valcarcel, M., and Luque de Castro, M. D., “Flow Injection Analysis: Principles and Applications,” Ellis Horwood. Chichester. 1987. RSiiCka. J . . and Hansen, E., “Flow Injcction Analysis.” Wiley. New York, 1981. Burguera. J . L.. and Burguera. M.. Anal. Clzem., 3982. 54. 1693. Fossey. L.. and Cantwell. F., Anal. Chem.. 1982, 54. 1693. Al-Wehaid.A.. PhD Thesis. University of Hull. 1987. Burns, D. T.. Chimpalee, N . , and Harriott. M., Anal. Chim. Acfa, 1989, 217, 183. Reusmann. G., Freseniuci Z. Anal. Clzem.. 1967. 226. 346. Fogg. A. G., Burgess. C.. and Burns. D. T., Anulysf, 1971.96. 854. Burns. D. T.. Chimpalee. N.. Harriott. M.. and McKillen. G. M.. Anul. Chim. Acfa. 1989. 217. 183. Burns, D. T.. and Chimpalee, D.. Anal. Chim. Acru. 1987. 199. 241. Burns. D. T.. Chimpalee, N., and Harriott, M.. 1989. Anul. Chim. Acra. in the press. Burns. D. T.. Hanprasopwattana. P., and Murphy. B. P.. Anal. Clrim. Acta. 1982, 134. 397. Burns. D. T.. and Kheawpintong. S.. Anal. Chim. Acm, 1984. 162. 437. Burns, D. T.. Chimpalec, N.. and Harriott. M.. 1989. Anal. C h n . Acra. in the press.ANALYTICAL PROCEEDINGS.SEPTEMBER 1980. VOL 26 317 17. 1X. Snell. F. D.. and Sncll. C. T.. "Colorimctric Methods of Stone. F. B.. J . Soc. Chem. I n t i . . 1x87. 6. 416. 21. 37 Analysis." Volumc 1 . "Inorganic." Chapman and Hall. --. Hasehe. K.. and Taga. M.. 7irlunfo. 19%. 29. 1135. London. 1936. Burns. D. T.. and Chimpalce. D.. Atitrl. ('him. Acw. I W X . 211. 305. 10. 30. 73. Burns. D. T., and Tungkananuruk. N.. And. c'hinz. Acfu. 1987. 197. 285. Karlbcrg. B.. and Thelander. S . . AnuI. C'hirn. Acfu. 1978. 78. I . Alegrct. S.. "Developments in Solvcnt E;xtraction," Horwood. Chichester. 10x8. Flow Injection Analysis Using Antibodies and Other Receptor Proteins J. N. Miller Department of Chemistry, Loughborough University of Technology, Loughborough, Leicestershire LE 1 I 3TU The extreme specificity offered to analytical scientists by biochemical reactions has long been recognised.and measure- ment techniques based o n enzyme - substrate or antigen - antibody interactions are widely used. Additional valuable reactions of this type include those between lectins and carbohydrates, avidin and biotin. and drugs or hormones and their natural receptors. The analytical method invariably involves the determination of the combination between the pair of binding molecules (L = ligand, B = binding site). the reaction normally being non-covalent and reversible: B + L = B L K A = [ BL]/[ H][ L] where K A (1 mole-') is the association constant and [BL], etc.. represent molar concentrations. In many cases, the receptor protein (P) contains n (> 1 ) binding sites (usually assumed to be independent and equivalent).so [B] = n[PJ. and it may be desired to determine n and K A as well as using the reaction in quantitative analysis. Two general approaches are available to follow these reactions. The more obvious uses a heterogeneous assay, in which the molecular complex formed, PL, is physically separated from the uncombined P and L molecules before determination. This method has two advantages: it is univer- sally applicable, and the separation step removes potentially interfering matrix components before the final measurement of [PL]. The drawbacks are that the separation step may complicate the methodology in practice, especially if automa- tion is desired. and that the separation may itself cause dissociation of the PL complex.By contrast, homogeneous assays utilise a change in the (usually spectroscopic) properties of either P or L which accompanies the formation o f PL. The extent of this change can be used as a direct measure o f PI, formation: no separation step is needed, and there is no danger of the P - L equilibrium being disturbed. However, a n easily measured change of property cannot always be identi- fied, and the non-reacting matrix components are still present at the measurement stage, possibly causing interferences. In practice both these approaches are widely used. Recent work has shown that flow injection analysis is capable of vcry advantageous use in each instance. The examples summarised in this paper use tluorescence detection: this method gives very low limits of detection, and fluorescence is sensitive to molecular environment effects.thus facilitating homogeneous assays. Homogeneous Assays One of the earliest applications of flow injection analysis. developed in the author's laboratory,' allowed the automation of a homogeneous fluorescence immunoassay for serum albumin based on the principle of non-radiative energy transfer. Fluorescein-labelled albumin. on binding to rhod- amine-labelled anti-albumin antibodies, suffered a reduction in the fluorescein emission because of energy transfer to neigh- bowing rhodamine groups in the albumin - antibody complex. This very short range effect was reversed in the presence of unlabelled (i.e.. sample) albumin. allowing the latter to be determined at nanomolar levels with good accuracy and precision.A stopped flow. merging zone FIA manifold was used. allowing sampling rates of about 1 0 h-1. More recently. homogeneous flow injection methods have been extended to the study of the protein binding of both acidic and basic drugs.24 Conventional FIA manifolds with or without merging zone techniques allow fluorescence probes to be used to monitor the binding of acidic drugs to albumin (both in pure solution and in dilute blood serum) and of basic drugs to orosomucoid (alpha- 1 acid glycoprotein). The latter studies used a fluorescent analogue of the drug propranolol (DAPN), whose dimethylaminonaphthalene sulphonyl ("dansyl") group acted as a fluorescence probe. The fluorescence intensity of this molecule is enhanced about eight-fold on binding to orosomucoid (excitation wavelength 340 nm; emission wavelengths 558 nm for free DAPN, 530 nm for protein-bound DAPN).The fluorescence enhancement effect is reversed by the presence of basic drugs which displace the DAPN from the protein's binding sites. Graphical analysis of the results at various protein to probe concentration ratios shows that there is one strong binding site per orosomucoid molecule. with K A = 2 x loh 1 mole-'. Such determinations of binding parameters effectively involve the titration of the protein with varying concentrations of the probe or drug molecules. Such titrations are elegantly handled by t h e use of tlow injection manifolds incorporating mixing chambers (0.26-7.0 ml volume)S." to provide concen- tration gradients. I n the case of the DAPN - orosomucoid interaction it was shown that a static fluorescence analysis evaluation of n and K A required several hours work and used about 30 ml of solutions of each material: a conventional single channel FIA system used about 0.3 ml of solution and took about 1 h.whereas a gradient FIA analysis took about 300 sand used 30 id of solution. This approach could clearly be used in other arcas. for example in the characterisation of monoclonal an tibodics. Heterogeneous Methods Many flow injection experiments incorporating solid-phase reactors have been described.' Packed-bed reactors have generally been used, but single head string reactors and open tube wall reactors have some advantages. Most reactors have operated on catalytic principles (especially with enzymes) or have uscd solid phases with high and not very specific binding capacities (e.g., ion exchangers).Work in the author's labora- tory has suggested two ways in which relatively low capacity and very specific reactors can be usefully applied to biochem- ical analyses. Many homogeneous assays involving fluor- escence detection in blood serum samples are hampered by the considerable "background" fluorescence of the serum itself.318 ANALYTICAL PROCEEDINGS. SEPTEMBER 1989. VOL 26 Detailed studies have shown8 that much of this fluorescence is protein linked, and can be removed by the use of solid-phase reactors containing specific protein absorbents. Particularly troublesome is the serum fluorescence band at about 520 nm due to albumin-bound bilirubin.This band coincides with the emission spectrum of fluorescein-labelled molecules, and affects the limits of detection of homogeneous methods based on such species. Albumin is efficiently removed from human serum by the dye Cibacron Blue immobilised on agarose beads, and small reactors containing this absorbent reduce by about 75% serum fluorescence at 520 nm. Each reactor has a short lifetime because of the high albumin content of serum, but the bound protein can readily be removed by a chaotropic solvent such as sodium thiocyanate and the reactor can be re-used after restoration of the original buffer carrier stream.6 The principle of a re-usable packed-bed reactor has been applied in a different form to the development of a hetero- geneous fluorescence immunoassay.Here the reactor contains agarose-bound protein A, which binds to antibody molecules at sites separate from those at which antigens combine, and so allows the antibody components of an immunoasssay mixture to be removed from unreacted antigen and sample matrix species. The work has utilised a reactor 10 mm long, 2.3 mm internal diameter (42-pI volume), containing swollen beads of protein A-agarose, 60-120 pm wet diameter, with an antibody binding capacity of about 2 mg. At a flow-rate of 1 ml min-l, through 0.8 mm i.d. tubing, the dispersion of the system was about 7.5. A Perkin-Elmer LS-2B fluorescence detector with a 7 PI flow cell was used with excitation and emission wavelengths of 471 and 520 nm, respectively. Immunoassay incubates were injected into this FIA system in a Tris-HCI buffer, 0.05 M, pH 7, and a manually operated switching valve was used to introduce 0.3 M potassium thiocyanate and thus remove bound antibody from the reactor after each sample injection.Trial injections of fluorescein-labelled goat anti- bodies yielded two fluorescent peaks ( i . e . , protein-A unbound and bound fractions, in that order) per sample. This result was expected since goat IgG2, but not goat IgG1, binds to protein A. However, twin peaks were also obtained when labelled rabbit antibodies were injected. As all these antibodies should, in theory, bind to protein A, this result indicated that either a short residence time in the reactor, or the blocking of protein A binding sites on the antibody by the fluorescent label groups, prevented complete binding.N.onetheless, unlabelled rabbit antibodies could be used in a heterogeneous assay for human albumin, with sample albumin and fluorescein labelled albu- min competing for the antibody binding sites. When the fluorescence intensity of the fraction not bound to the protein A reactor was determined, the expected increase of fluores- cence with sample albumin concentration was found (Fig. l ) , and the assay could readily be used to determine sub-micro- molar albumin concentrations. The protein A reactor could be used in this alternating fashion for hundreds of samples over several days. Each sample contained not more than 500 pg of antibody (i.e., 25% of the reactor capacity), so the reactor might lose a substantial fraction of its activity ( e . g ., by leakage T 1 1 1 1 T 0 2 4 6 8 10 Albumidpg ml-’ 130 120 =110 100 Fig. 1. Heterogeneous immunoassay of human serum albumin using protein A reactor with solvent alternation in a flow injection separation step. The fluorescence signal (arbitrary units) measures the fluorescein labelled albumin fraction not bound to the reactor or denaturation of the protein A) before adverse effects on the immunoassay are observed. Conclusions These summarised results indicate the potential of flow injection methods in a variety of homogeneous and hetero- geneous biochemical assays. The methods preserve the usual advantages of FIA, and allow approaches that would otherwise be difficult or impossible. Because high binding capacities are not required, single bead string reactors or open tube wall reactors could be used in the heterogeneous assays.References 1. 2. 3. 4. 5. 6. 7. 8. Lim. C. S., Miller, J. N., and Bridges, J. W.. Anal. Chim. Acta. 1980. 114, 183. Miller, J. N.. Anal. Proc.. 1981. 18, 227. Abdullahi, G. L.. Miller, J . N., Sturley, H. N.. and Bridges, J. W.. Anal. Chim. A m . 1983. 145, 109. Sturley, H. N., PhD Dissertation, Loughborough University, 1983. Abdullahi, G. L., and Miller, J. N., Analyst, 1985, 110, 1271. Miller. J. N.. Abdullahi, G. L.. Sturley, H. N., Gossain. V., and McCluskey. P. L., Anal. Chim. A m , 1986, 179, 81. Riiitka, J.. and Hansen. E. H.. “Flow Injection Analysis.” Wiley, New York. Second Edition. 1988. Gossain. V.. MSc Dissertation. Loughborough University, 1984.Spectroscopy‘s Answer to the Nernst Equation Julian Tyson Department of Chemistry, Loughborough University of Technology, Loughborough, Leicestershire LE 7 1 3TU The majority of flow injection methods use peak height as the quantitative parameter to be related directly to analyte concentration. For the vast majority of methods this peak height is the detector’s response to the product formed on-line between the injected determinand and the reagent in the carrier stream.ANALYTICAL PROCEEDINGS. SEPTEMBER 1Y89. VOL 26 319 Physical Dispersion in a Flow Injection System Both the value of the peak height and the shape of the product profile are due to a combination of physical and chemical factors. The injected determinand solution inter-disperses with the reagent carrier stream by a variety of hydrodynamic processes. For simple open tubular reactors the predominant mechanisms are those of convection due to laminar flow and diffusion.The extent to which the injected and carrier solutions have inter-dispersed can be quantified by the dispersion coefficient, D,. This is simply the ratio of the concentrations at time t = 0 to the concentration in an element of fluid at t > 0. The dispersion coefficient is thus a function of both time and location of the selected element of fluid. In practice, the most useful information is obtained by consider- ing the volume of solution viewed by the detector to be an “element” of fluid and to monitor D, as a function of time. As can be seen from Fig. 1, two values of D, can be associated with 1 \ ” / 0 b Time ”./-7 \ / * I \ i ------- Time Fig. 1. (a). Physical dispersion in a single-line manifold; r is the reagent profile (in flowing stream) and d is the reactant profile (injected). ( h ) . Physical dispersion plus chemical reaction; p is the product profile. The reagent is in excess across the entire profile any instant, that for the injected determinand species, Dg (D: = Cd,/Ci), and that for the carrier stream reagent species DL ( D i = Ck/Ci). At time t = tp, when the physically dispersed injected species maximum occurs, a value of D, is obtained which is often taken as characteristic of a particular manifold and operating conditions. The conventional notation for this value involves omitting the subscript “g” (indicatin any point on the concentration gradient), i .e . , Dd = Cd,/Cp and Dr = C;/CL. As the dispersion coefficient concept was first formu- lated for the injected species only, the symbol D is often used for the value of Cd,/Cz. In a single-line manifold, if it is assumed that in any volume element of fluid the determinand has been diluted by the reagent and vice versa, then the relationship between the two dispersion coefficients is B (mi) + (l/D,d) = 1 . . . . , Dispersion and Chemical Reaction The extent to which the product forms is governed by the reaction kinetics and the equilibrium constant. As can be seen from Fig. 1, the ratio of reagent to determinand varies with time and is a minimum at t = t,. Product peak height values may be lower than expected as the values for percentage formation of the product of a 1 : 1 reaction given in Table 1 show. The extent of reaction may be incomplete due also to an insufficient residence time.Changing the manifold and reac- tion conditions to improve either the thermodynamic or kinetic factors results in an increase in Dd and hence a possible loss of Table 1. Percentage formation of product C‘/Cd K = 100 K = 10 lo() 99.99 99.90 10 99.89 Y 8.90 1 90.49 72.98 sensitivity. The design and optimisation of a flow injection manifold are thus quite complex procedures if the best sensitivity is required. Limitation of Peak Height Measurements As the concentration of the determinand increases, eventually a value is reached for which the peak concentrations of determinand and reagent are equal, and beyond this the determinand concentration is in excess in the profile centre and a doublet peak is formed.At this stage an upper limit has been reached for the working range of the method. An upper limit may be reached before this stage if the detector has a limited dynamic range. This is often the case with molecular absorp- tion in solution, for which the deviation from linearity of the calibration function due to stray light may well set an upper limit to the working range before doublet peaks are observed. An analogous problem is encountered for systems in which there is no on-line chemical reaction but for which the detector has a limited dynamic range. The most widely encountered examples in flow injection methodology are systems using an atomic absorption detector.In conventional methods, the only way to deal with off-range samples would be to re-run the sample after a suitable dilution, for which a factor might only be arrived at by a process of trial and error. Peak Width Measurement The transient nature of the flow injection peak offers an alternative to off-line dilution, namely the use of peak width as a quantitative parameter. Quantification by peak width measurements was first demonstrated by Rfiiieka et al.2 for complexometric and acid - base reactions. In each case the concentration of a reactant was followed as a function of time. A theoretical treatment of the physically dispersed injected determinand peak width was given based on a peak shape consisting of an infinitely fast rise followed by an exponential decay.Pardue and Fields examined the full exponential peak shape3-4 and produced equations for the width of a reactant peak. By making a number of simplifying approximations they were able to produce an equation in agreement with that of Rfiiieka et af. Stewart and Rosenfelds used a version of this equation and demonstrated that an increased working range could be obtained for a number of detectors (atomic emission, molecular fluorescence, conductance, molecular absorption) by using a calibration function in which peak width was plotted as a function of the logarithm of the injected concentration of determinand. These early papers on quantification via peak width used a variety of terms for this method of analysis, including “titration,” “pseudotitration,” “variable-time kinetic method” and “scale expansion.” Some of the papers also contained errors in the mathematical derivations of the peak width equation.Quantitative Relationships The width of an exponential peak in the absence of chemical reaction is given by1 At, = (V/Q) In [(Cd,/Ci) - 11 - (V/Q) In (Dd - 1) . . (2) This is based on the single well-stirred mixing chamber approach of Pardue and Fields,3 where V is the volume of the chamber, Q the volumetric flow-rate and Azg the width at any320 concentration Ci. This exact equation shows that Atg is not a simple function of Inc: however, if it is assumed that (c",/G) >> I then equation 2 reduces to . . ( 3 ) I f the value of Atg, obtained when em is unity, is designated Afg = At: + (2.3V/Q) log C i .. . . (4) This equation has a form similar to that of the Nernst equation (and for V = 1 ml andQ = 2.35 ml min-1 has a slope of 59 s per decade). In order to assess whether the approximation required to produce equation 4 is valid, values of Atg were calculated from the exact form of the equation (equation 2 ) for the experimen- tal parameters used by Stewart and Rosenfeld,-5 namely Vi = 50 PI, V = 200 pl, Q = 50 p1 s-1, Ck = 1&1W pg 1 - 1 . A value of 2 pg 1-1 for Ci was chosen. A plot of Atg against log C i had a correlation coefficient of 0.9998. Atg = ( V / Q ) In C i - ( V / Q ) In (Dd - 1)Ci At:, then equation 3 may be expressed as ANALYTICAL PROCEEDINGS. SEPTEMBER 1989, VOL 26 Equation 5 can be obtained by substitution of the appro- priate values for D,, into equation 1.Substitution of C,, for C; in equation 2 and rearranging produces At,, = (V/Q) In (Cd,,) - (V/Q) In (D - 1)Cd,. . (6) As before, if At,, = At:, when em = 1, then equation 6 can At,, = At& + (2.3 V/Q) log C; . . . . ( 7 ) Equation 7 has a form similar to equation 4 and thus is also a flow injection analogue of the Nernst equation. The equation has been examined in detail and good agreement between calculated and measured values of Ateci obtained for a variety of operating parameters.8 The use of the doublet peak width method for extended calibration has been demonstrated for the Cu : EDTA reaction,I.X Fell : 1,lO-phenanthroliney and OH- : H+/bromothymol blue.8 It has been shown that a mixing chamber is not necessary, as the hydrodynamics in short lengths of tubing produce approxi- mately exponential and that it is possible to monitor a reactant or indicator profile and estimate the location of the equivalence points.Species which have been determined by this peak width method include strong and weak acids, ascorbic acid, calcium and aminopolycarboxylic acids,l' calcium and magnesium in water" and ionic surfactants. 13 I t should be noted that such methods are not necessarily performed in manifolds with high dispersion coefficients, as is sometimes stated in the literature. For example, in the doublet peak determination of Cu by titration with EDTA,' a manifold with a dispersion coefficient of 1 .(lo8 was employed. be re-written as Application of the Peak Width Method This equation has been used as the basis for the extended range calibration of atomic absorption spectrometers.It was assumed that the nebuliser and spray chamber provided an approxima- tion to well stirred tank behaviour and it was shown that calibrations up to 100 pg ml-1 of magnesium, chromium and nickel were p ~ s s i b l e . ~ . ~ Flow Injection Titrations This form of the equation could also be applied to the situation in which the product of an on-line reaction was monitored and the reagent was in excess across the entire dispersed profile (see Fig. 1). However, when the sample is in excess in the profile centre and doublet peaks are formed, as is shown in Fig. 2, the time interval between the peaks can be used without any approximations being necessary to give a linear relationship with log C'k.For a 1 : 1 reaction, the points of intersection of the physically dispersed reagent and determinand profiles represent a time at which the concentrations of the reactants are in the stoicheiometric ratio according to the equation for the reaction. For this reason, these points have been con- sidered as equivalence points in two continuous flow titrations, hence the terminology flow-injection "titration." This termi- nology has been criticised on the grounds that such conditions do not correspond to the IUPAC definition of a titration.3 / \ . \ ' \ I d i'\ j ' i d I \ '\ 1 \ +Ateq + Time - Fig. 2. ( u ) . Physical dispersion in a single-line manifold with the dctcrminand. d. in excess in the profile centre. The reagent. r , is in deficit in the profile centre.( h ) , Physical dispersion plus chemical reaction; p is the doublet peak product profile The concentration at the equivalence points, Ceq is given by c,, = Cd,,C',/(Ck + C:') . . . . . . ( 5 ) Conclusion Several groups of workers have demonstrated the validity of using flow injection peak width measurements as the quantita- tive basis of a method in which the time interval between two points of equal concentration is related to the logarithm of the injected solution concentration. This type of quantitative relationship allows the working range of the conventional peak-height method to be increased. There is no requirement for the detector response to be linearly related to concentration and this, perhaps, indicates that low-cost detector devices could be employed for this peak width method.For the doublet peak method the detector does not need to be free from drift as a sloping base line will not affect the indication of a peak in the product profile. The precision is unlikely to be as good as for a method in which the magnitude of the parameter measured is related directly to concentration. If the best precision is required, the peak width method could be used to provide a dilution factor for subsequent re-analysis by a more precise method. 1. 2. 3. 4. 5 . 6. 7. 8. 9. 10. 11. 12. 13. References Tyson. J. F.. And. Chim. Actu. 1986. 179. 131. Rfiiieka, J.. Hansen, E. H.. and Mosbaek, H.. Anul. Ciiim. Actu, 1977, 92. 235. Pardue. H. L.. and Fields. B.. Anal. Chim. Actu. 1981.124.39. Pardue. H. L.. and Fields.B.. Anul. C'liim. Actu. 1981.124.65. Stewart. K. K.. and Rosenfeld. A. G.. And. Chem., 1982. 54, 2368. Tyson. J . F.. Analyst. 1984. 109, 319. Rysouth. S. R.. andTyson. J . F.. And. Chim. A m . 1986.179. 481. Tyson. J . F.. Analyst. 1987. 112. 523. Tyson. J . F.. Anal. C'him. Actu. 1986. 180. 151. Ramsing, A. U.. RfiiiEka. J., and Hansen, E. H . , Anal. Chim. A m , 1981, 129, 1. Caiiete. F.. Rios, A.. Luque de Castro. M. D.. and Valcrircel. M.. Analyst. 1987. 112. 267. Koupparis. M. A.. Anagnostopoulou. P.. and Malmstadt. H. V . , Tuluntu. 1985. 32, 31 1. Ilowle. C. J.. Cooksey. B. G., Ottaway. J . M., and Campbell. W. C.. Analyst. 1988. 113. 117.ANALYTICAL PROCEEDINGS. SEPTEMBER 1989. VOL 26 Flow Injection Analysers for Clinical Use 32 1 B. F. Rocks Biochemistry Department, Royal Sussex County Hospital, Brighton BN2 5BE From a clinical chemist’s point of view the promise of rapid results, low sample and reagent consumption and simple reliable instrumentation is most appealing.It was these often cited virtues of flow injection analysis (FIA) that led bio- chemists from the Royal Sussex County Hospital in Brighton and biomedical engineers from Sussex University to investigate the potential of FIA for clinical use. Problems In practice, however, conventional FIA methods proved to have serious limitations. Contrary to reports in the literature the technique requires, at least by clinical chemistry standards, a very large volume of sample. Although the actual injected volume may be small, say 10 pl, typically about 500 p1 of sample would be needed to flush and fill the valve and connecting tubes.Most authors state only the volume o f injected sample and not the total volume of sample consumed. Another problem associated with the conventional injection technique is that valves wear relatively quickly and frequently develop leaks. This has not been reported by academic chemists, presumably because few of them have worked with undiluted plasma and they are unlikely to have subjected the valves to the heavy workload typical of a hospital laboratory. Many authors pre-dilute plasma before analysis by FIA, but clearly the aim should be to design analysers that are capable of accepting untreated blood plasma. Despite these limitations conventional FIA is useful for “one-off” testing or for single chemistry determinations on small batches of samples; in our laboratory we use FIA - AAS for the routine determination of zinc and copper.The technique is not, however, best suited to dealing with the bulk of clinical laboratory work, which requires the determination of between 5 and 20 different analytes on each specimen. A Different Approach In order to address the deficiencies of FIA the group in Brighton designed and built a type of flow injection analyser that dispensed with the use of an injection valve and instcad introduced the sample into the system by aspiration.’,’ This approach has been referred to as controlled dispersion flow analysis, CDFA. In its simplest form CDFA consists of a sample probe (attached to a small arm) that normally resides in a trough of carrier solution, usually de-mineralised water.The probe is connected to a peristaltic pump tube and the pump and sampler arm are driven by microcomputer controlled stepper motors. The other end of the pump tube is connected to a T-piece where the sample stream is merged with a reagent stream before travelling towards the detector. The number of pulses sent from the computer to the pump motor determines the volume of fluid pumped and the frequency of pulses defines the flow-rate. The relative volumes of sample and reagent can be varied by choosing pump tubes of different internal diameter. An analytical cycle involves the following keyboard con- trolled operations. Sampling phase. The probe (or probes) is moved from the carrier trough into the sample tube.The pump motor is activated, causing the peristaltic pump to rotate through a pre-determined angle, drawing a small volume (typically about 5 PI) of sample into the probe. The probe is then returned to the carrier solution. Transporting phase. The pump is re-started and the sample slug is swept through the system, dispersing as it travels, and merged with the reagent stream before entering the detector. By varying the sample volume (via the keyboard) and the manifold tube dimensions different degrees of dispersion can be generated to suit different analytical requirements. Rinsing phase. Once the measurement has been completed the pump speed is increased and the sample rapidly washed from the system. The analyser usually contains one sample at a time and rinsing is such that carry over is not detectable.Assays Rapid analytical reactions, such as those of chloride, calcium and albumin, are quantified by peak height measurements as the reaction zone passes through the detector. * , 3 - 5 Typically, the analytical readout is obtained about 12 s after sample introduction with a precision of about 1%. A complete analytical cycle takes 18 s. Most slower reactions, for example, glutamyl transferase, triglycerides and theophylline, can be determined kinetically by stopping the reaction slug in the flow cell for about 15 s and computing the rate of I n these instances measurements can be made with a precision of about 5%. Many immunoassays and a few enzyme assays, such as acid phosphatase, require longer reaction times and in a single tube system sample throughput would be very low.In order to facilitate long incubation times a system employing “holding coils” has been developed.h An automated distribution valve is used to direct sequential reaction slugs into one of a series of parallel coils, where they remain for a fixed period in order to allow measurable reaction products to accummulate before they are pumped to the detector. Multi-test Analysers We have planned a “multi-channel” analyser consisting of a series of dedicated test units placed adjacent to a sample conveyor system. A discretionary analyser expandable from 4 to 32 ”channels” with a throughput of 150 samples per hour is envisaged. This type of machine could function as the main workhouse of a large hospital laboratory.By employing a series of three-way solenoid valves to introduce different reagents into the flow system a single analytical unit can be used to carry o u t several different assays. Suitable electrically activated microvalves are available from the Lee Company. These valves are chemically inert and, because of their low voltage and low power requirements, can be controlled by a microprocessor. A single unit multi-test analyser of this design is small enough to sit on a desk top and should find a niche in the rapidly expanding near-patient testing market. Infectious Specimens Because of the absence of sample splashing and aerosols flow based analysers offer the operator a greater degree of safety compared with the more widely used discrete analyser systems. Hence, another exploitable area for flow injection is the testing of “high risk” samples. References 1 . Riley. C., Aslett. L. H.. Rocks. B. F.. Sherwood, R . A., McK. Watson, J . D.. and Morgon. J.. C’liri. C‘hern.. 1983. 29. 3.32. Riley. C., Rocks. B. F.. and Sherwood. R. A.. A n d . Chim. rlcru. 1986. 179. 69. 2.322 ANALYTICAL PROCEEDINGS. SEPTEMBER 1989. VOL 26 3. 4. Shcrwood, R . A . . Rocks. B. F . , and Riley, C.. Analyst. 1985, 110,493. 10, 847. Rocks. B. F.. Wartel. S. M . , Sherwood. R . A . . and Riley, C.. Anulysf, 19x5. 110. 669. 5 . Rocks. B. F.. Sherwood. R . A . . and Riley, C., Analyst. 1984. 6 . Rocks. B. F.. Sherwood, R. A , . Hosseinmardi. M. €1.. and Riley. C.. Anal. Chim. A m . 1986. 179, 225. An Introduction to Applications of Light Microscopy in Analysis By D. Simpson and W.G. Simpson, Analyskfor Industry, Thorpe-k-soken Light Microscopy is one of the oldest techniques at the disposal of the analyst and is unfortunately greatly undervalued and underused in the analytical laboratory. It is, in fact, a conventional economical technique which should not be overlooked and can be of great value in the analysis of foods, pharmaceuticals, metals, plastics, water, agrochemicals, textiles and much more. In this book the authors draw upon their considerable experience in industry and consulting practice, to provide examples of the many and varied uses of light microscopy in analysis. They describe in detail its capabilities and seek to encourage its wider use in actual practice, reminding analysts of its qualities and applications. They also advocate good practice in its use. Microscopists, analysts and students alike will gain much from the authors’ enthusiasm and as a result may assist in extending the utility of the instrument into the future. Price g29.50 ($63.00) ISBN 0 85186 987 4. Hardcover 215pp ROYAL Information Services To order or for further information, please write to the: Royal Society of Chemistry, Distribution Centre, Blackhorse Road, Letchworth, Herts SG6 IHN, UK OY telephone (0462) 672555 quoting your credit card details. We now accept Access/Visa /MastelCard /EuroCard. RSC Members are entitled to a discount on most RSC publications and should write to: Membership Manager, Royal Society of Chemistry, Science Park, Milton Road, Cambridge CB4 4WF, UK.

ISSN:0144-557X    

DOI:10.1039/AP9892600313

出版商:RSC    

年代:1989

数据来源: RSC

摘要:

ANALYTICAL PROCEEDINGS, SEPTEMBER 1989, VOL 26 323 Equipment News X-ray Analysis Systems The eXL X-ray microanalysis system incorporates a new computer-controlled pulse processor and makes use of the makers’ Pentafet charge restoration tech- niques. It offers powerful image acqui- sition and fast data processing routines. A comprehensive range of software for quantitative X-ray microanalysis, image analysis and processing and electron mi- croscope automation is available. The QX2000, a development of the AN10000, is an analytical workhorse for the routine laboratory. Brochures are available. Link Analytical Ltd., Halifax Road, High Wycombe, Buckinghamshire HP12 3SE. Software for Ultraviolet - Visible Spectroscopy MS-DOS software for the HP 8452A ultraviolet - visible spectrophotometer and the HP Vectra personal computer is announced.A combination of diode- array spectroscopy with applications soft- ware makes it possible to offer a single package for laboratories requiring straightforward, reliable, high productiv- ity, routine analyses and for laboratories involved in method development and research. It contains options for general scanning, quantification and kinetics applications. Hewlett-Packard, 3000 Hanover Street, Palo Alto, California 94304, USA. Ultraviolet and Visible Spectrophotometers The PUS625 spectrophotometers, avail- able in visible and ultraviolet - visible versions are easy to use, having just five push buttons. They are based on the established PU8620. Philips Analytical, York Street, Cambridge CB12PX. Spectrophotometer The CM-1000 is a compact and portable instrument.It consists of a measuring head connected to a control-analysis unit by a flexible cable. The head is fitted with the universally applicable geometry of d/O and a pulsed xenon (PXA type) light source. It offers the advantage that thermochromic effects are excluded. The control and analysis unit is a lap-top type computer with a large liquid crystal dis- play. The graphics can be produced in several different forms as well as a three- dimensional, three axes movable graphic display of the colour space. Minolta (UK) Ltd., 1-3 Tanners Drive, Blakelands North, Milton Keynes MK14 5BU. Benchtop Atomic Emission Detector for Gas Chromatography A totally automated benchtop atomic emission detector, the HP 5921A, features a microwave plasma source and a photodiode array for sensing spectral lines simultaneously across a wavelength Gas Chromatographs The Model 8600 and new versions of the Model 8700 are the latest additions to the 8000 Series of gas chromatographs. The Model 8600 is a single-channel instru- ment, available with either colour or monochrome VDU.Standard software includes data handling with re-integration and multi-level calibration. Real-time and post-run graphics allow comparison of chromatograms and there is full provision for PC communications. Fully automated sequencing is provided for routine appli- cations. The Model 8700 is the full dual channel of the Model 8600. Perkin-Elmer Ltd., Post Office Lane, Beaconsfield, Buckinghamshire HP9 1QA. Thermal Conductivity Detector The 10-955 micro thermal conductivity detector is offered as a stand-alone detec- tor, suitable for most manufacturers’ GCs or for the makers’ GM 200/300 series of detectors.The makers contend that ther- mal conductivity is a simpler method of detection than, say, FID, with no flame gases and often no make-up gas. It is non-destructive and can therefore be used in series with other detectors. Gow-Mac Instrument Co. Ltd., Gow- Mac House, 6 Livingstone Circus, Gill- ingham, Kent NE7 4HA. Hewlett- Packard HP 5921A atomic emission detector range. It can be used for element specific compound identification or in combina- tion with mass selective and infrared detectors. It can selectively detect any element (except helium) in compounds eluting from a GC column.Hewlett-Packard Ltd., Miller House, The Ring, Bracknell, Berkshire RG12 1XN. Capillary Column The makers guarantee that every new PTE-5 capillary column will meet the column performance specifications in US Environmental Protection Agency Methods 1625 and 8270 for analysing semi-volatile pollutant compounds. Supelco Inc., Supelco Park, Bellefonte, PA 16823-0048, USA.324 ANALYTICAL PROCEEDINGS, SEPTEMBER 1989, VOL 26 Liquid Chromatography System The LC Analyst system offers computer control for methods development and automated sample processing. It includes a quaternary LC pump, random-access autosampler and personal computer with LC Analyst software. Data can be taken from any detector. Perkin-Elmer Ltd., Post Office Lane, Beaconsfield, Buckinghamshire HP9 1QA.Universal Detector for Supercritical Fluid Chromatography The SFC-Mass detector greatly expands the range of compounds which can be studied by SFC. Detection levels of 25 ng are seen for traditionally difficult separa- tions such as steroids. Applied Chromatography Systems Ltd., The Arsenal, Heapy Street, Macclesfield, Cheshire S K l l 7JB. Alumina Unisphere-PBD alumina is available in both bulk and pre-packed columns. It is a general-purpose reverse-phase chromato- graphic support intended for HPLC appli- cations. Its polybutadiene coated alumina particle has superior flow characteristics and provides faster separations than sil- ica-based products. Developed by ALCOA Laboratories, Unisphere-PBD has uniform polymer coating, which offers good chemical stability, virtually eliminating non-specific adsorption due to free residual hydroxyls.Biotage Inc., Riverside Technology Center, 840 Memorial Drive, Cambridge, MA 02139, USA. pH Electrodes The Futura Plus range of electrodes feature the makers' pHresh Performance Pac, which eliminates pre-applica tion clean-up and conditioning of the glass bulb. The electrodes fit four application groups and include: general purpose/bio- logical sample glass and epoxy electrodes with calomel reference half-cells; high temperature glass and epoxy versions with silver - silver chloride reference half-cells; speciality electrodes featuring rugged bulbs, fast temperature response bulbs, flat bulbs and gel-filled reference half-cells; and electrode pairs with stan- dard or rugged bulb indicating electrodes and calomel or silver - silver chloride reference models in either quartz fibre or ceramic frit style.Beckman, Progress Road, Sands Indus- trial Estate, High Wycombe, Bucking- hamshire. Characterisation of Viscoelastic Fluids The Rotovisco RV20 viscometer program has been extended by the new measuring system CV20N especially designed for the analysis of elastic properties of low, mid- dle and high viscous substances. Haake, Dieselstrasse 4,7500 Karlsruhe 41, FRG. Refractometer The GPRll-37 has been developed for use in areas where equipment is likely to get wet frequently, for example, during general cleaning. The refractive index range is 1.32 to 1.70, and samples can be read at any temperature from 10 to 70 "C. The sample temperature is displayed automatically with each reading. Read- ings are made to an accuracy of 0.0001 refractive index (0.1% BRIX). Index Instruments Ltd., Bury Road Industrial Estate, Ramsey, Huntingdon, Cambridgeshire PE17 1NA.Thermal Analysis System The PC Series thermal analysis system is designed for routine analytical and quality control applications. An IBM (R) PS-2 or EPSON (TM) PC controls the range of Perkin-Elmer industry standard thermal analysis modules: the DSC 7 differential scanning calorimeter, the TGA 7 thermo- gravimetric analyser, the TMA 7 thcrmo- mechanical analyser and the DTA 1700 differential thermal analyser. Data can be imported into a wide range of third party packages, such as Lotus 1-2-3 (R), or analysed using the makers' specialised software programs.A complete range of MS-DOS compatible software is available to control and analyse data from all of these instruments. Perkin-Elmer Ltd., Post Office Lane, Beaconsfield, Buckinghamshire HP9 1QA. Through-pore C haracterisation Using the liquid displacement poros- imetry technique pioneered in the mak- ers' Porometer, and with further enhance- ments added to expand the instrument's capabilities, the Porometer I1 allows users to select pore size distribution, pressure hold test or permeability measurements. If all three tests are required the results are held in memory for reviewing. Integ- rity of filters and cartridges can quickly be established at user programmable pres- sures and test times, and sample per- meability can also be measured at any user selectable pressure.Other improve- ments include a user definable bubble- point test, an autoprint function and theoretical pore number distribution. Coulter Electronics Ltd., Northwell Drive, Luton, Bedfordshire LU3 3RH. Compressed Air Systems The Model 2000 air system is a laboratory air compressor which can quietly deliver moisture-free, particle-free air. The systems are maintenance free, requiring a change of filters only every 2000 working hours. Jun-Air (UK) Ltd., Bridge Street, Lin- wood, Paisley, Renfrewshire PA3 3DG. Flow Calibrator The Gilian Gilibrator-2 is an accurate flow calibration system for sample pumps. It has been designed to offer calibration with an accuracy of k 1% in a flow-rate of from 1 ml to 30 1 min-1 for any inert gas at around ambient pressure.Eden Scientific, 1 Beechrow, Ham Common, Richmond, Surrey TWlO 5HE. Water Recirculator The Kryo-Thermat refrigerated water cir- culator works at temperatures between -15 and -40 "C and is designed to remove heat from high quality measuring and analysis systems, such as electron microscopes, lasers, spectrometers, etc. It can also be used for cooling rotational evaporators, electrophoresis systems and reaction vessels as well as for temperature control of tools for plastics manufactur- ing. Six types are available with strong circulating pumps and cooling capacities from 350 to 5500 W. Haake, Dieselstrasse 4, 7500 Karlsruhe 41, FRG. Surface Analysis The Nanosurf 488 adapts existing 2-D systems for 3-D analysis. By using stan- dard displacement sensors, either dia- mond tipped or laser, this 3-D profil- ometer can create a 3-D representation of the surface topography on a computer monitor.Statistical analysis functionsANALYTICAL PROCEEDINGS, SEPTEMBER 1989, VOL 26 325 include Abbot distribution curves, height histograms, surface area measurement and high and low pass numerical filtering. Nanosurf 488 allows for rapid measure- ment and dynamic adjustment of measurement parameters, such as sam- pling steps and the number of points measured. SAS Technologies, Technoparc, Rue Du Cristal, F-45072 Orlkans Ckdex, France. Electron Microscope The JEM 1200 EX11 has been developed specifically to support fundamental biotechnology research and environmen- tal studies involving particle micro-analy- sis. It employs a three-stage, six-lens image forming system.An objective mini- lens for low magnifications permits high- contrast, yet high-resolution, images to be obtained even at such low magnifications as those of the light microscope. At a magnification of 5 0 ~ a visual field of 2 mm diameter can be observed without image distortion. Features include focus zoom, which allows magnification changes without focus changes. Jeol (UK) Ltd., Jeol House, Grove Park, Colindale, London NW9 OJN. Microbiological Safety Cabinets Envair (UK) Ltd. have been awarded a Home Office contract to supply three large Class I microbiological safety cab- inets for forensic use at the Central Research and Support Establishment at Aldermaston. Envair manufacture a com- plete range of microbiological safety cabinets conforming to all classes of BS 5726, as well as several types of special- ised safety cabinets and isolators to protect operators from harmful drugs and materials.Envair (UK) Ltd., York Avenue, Haslingden, Rossendale , Lancashire BB4 4HX. Spectroscopic Ellipsometer A new instrument, called MOSS, for measuring film thicknesses in the optical and semiconductor industries is capable of measuring the thickness of both single layers and multiple layers of materials deposited on a variety of substrates. It is able to measure optical parameters at any wavelength between 300 nrn and the near infrared, or throughout the infrared when used in conjunction with an FT inter- ferometer. Spectrolab Ltd., P.O. Box 25, New- bury, Berkshire. Dissolution Testing System A dissolution testing system has been designed specifically to help users to comply with Good Laboratory Practice.It fully automates the rate determination at which active ingredients in solid-dosage pharmaceutical products are released. The system operates via an HP Vectra PC. The new ultraviolet - visible software uses the Microsoft Windows operating environment. A full-colour, graphical user interface provides easy to follow routines for data acquisition, evaluation and report generation. Hewle tt-Pac kard, 3000 Hanover Street, Palo Alto, California 94304, USA. Floating Microtube Rack The Nalgene Floating Microtube Rack holds sixteen filled 1.5 rnl microcentrifuge tubes or 1.2 and 2.0 ml Nalgene Cryovials in a 4 x 4 array. It allows convenient incubation at elevated or reduced temper- atures in water- or ice-baths.It is espe- cially useful in cloning, microbiology and immunology laboratories. Nalge Co., Box 20365, Rochester, New York 14602-0365, USA. Test for Coliform Bacteria A new, rapid and simple method of monitoring bacterial contamination in drinking water has been introduced. Called Palintest Colilert, the test will simultaneously detect, measure and iden- tify the presence of coliform bacteria, and specifically E. Coli, in under 24 h. Each test takes just 2 min to set up. Wilkinson and Simpson Ltd., Palintest House, Kingsway, Team Valley Estate, Gateshead, Tyne and Wear N E l l ONS. Workstations for Molecular Modelling Based on Digital Equipment Corpora- tion’s VAXstation 3100, the new P-GRAF 2 workstations run the makers’ CHEM-X software and are available in a variety of configurations.Chemical Design Ltd., Unit 12, 7 West Way, Oxford OX2 OJB. Power Supply for Lasers Introduced for the makers’ Type LGK 8100 C 0 2 waveguide laser, the LGN 8002 300 W compact power supply measures only 224 x 362 x 115 mm and is, therefore, small enough to be built into laser equipment. Siemens Ltd., Siemens House, Wind- mill Road, Sunbury on Thames, Middlesex TW16 7HS. Literature The 1989 Chromatography Supplies Cat- alogue, Catalog 27, contains well over 300 pages and covers products for GC, HPLC, SPE, capillary, sample prepara- tion, chemical standards and industrial hygiene. It includes the new Petrocol2887 capillary columns for SIMDIS analyses. Supelco Inc., Supelco Park, Bellefonte, PA 16823, USA.A brochure describes the Surveyor range of fixed gas detection systems and features their combustible, toxic and oxy- gen detectors and controllers, which are BASEEFA approved intrinsically safe. Servomex (UK) Ltd., Crowborough, Sussex TN6 3DU. The theory behind the Coulter Multisizer particle size analyser is explained in a new brochure, which also explains the variety of applications, from pharmaceutical to food industry, for which the Multisizer can be used. Coulter Electronics Ltd., Northwell Drive, Luton, Bedfordshire LU3 3RH. A brochure describes the Narishige mi- cromanipulators available for the Nikon microscope range. They come in many variations and combinations of up to four channels for precise injection, aspiration and incision in cell tissues.Nikon UK Ltd., Instruments Division, Haybrook, Halesfield 9, Telford, Shrop- shire TF7 4EW. A new edition of the Research Organics Inc. biochemicals catalogue is available. It lists over 1500 other products in ten sections: ACS Reagents, Molecular Bio- chemicals, Brain Research Biochemicals, Buffers, Enzyme Test Reagents, Pep- tides, Plant Growth Regulators, Fluores- cent Label Standards, Tetrazolium Salts and Vitamin-Free Casein. Ubichem Ltd., Mayflower Close, Chandler’s Ford Industrial Estate, East- leigh, Hampshire SO5 3AR. A compact disc, The Pesticides Disc, on CD-ROM (compact disc - read only memory) gives instant access to informa- tion on (1) fungicides, bactericides and viricides, (2) herbicides and algicides, (3) insecticides, acaricides and nematicides and (4) plant growth regulators, rodent- icides and molluscicides. Marketing Department, Pergamon Compact Solution, Irwin House, 118 Southwark Street, London SE1 OSW. Volume 10, Number 3, of Philips’ Ana- lytical Bulletin contains articles on cus- tomer support, the determination of a h - minium by graphite furnace atomic absorption spectrometry, the PW1480 sequential X-ray spectrometer and new software, the screening of drugs of abuse, ultraviolet spectrum library, automation in the analysis of solid samples such as steel, an RF generator for the PU7450 ICP spectrometer, an advance in capillary columns, peak characterisation, a new split - splitless injector and extending the PU8700 ultraviolet - visible spectrometer. Philips Scientific, Analytical Division, York Street, Cambridge CB1 2PX.

ISSN:0144-557X    

DOI:10.1039/AP9892600323

出版商:RSC    

年代:1989

数据来源: RSC

摘要:

326 ANALYTICAL PROCEEDINGS, SEPTEMBER 1989, VOL 26 Conferences and Meetings Third International Meeting on Chemical Sensors October 1-5, 1989, Toronto, Canada This meeting has now been cancelled. Environmental Regulation in the European Community October 19-20, 1989, London This meeting, which is to be organised by Legal Studies and Services Ltd, in associa- tion with The United Kingdom Environ- mental Law Association, will be held in the Mayfair Inter-Continental Hotel, London W.l. The speakers will include Malcolm Grant, Eberhard Bohne, Mario Chiti, Richard Burnett-Hall, Harvey Yakowitz, Andrew Bryce, Malcolm For- ster, Mary Sancy, Owen Lomas, George Close, John Bates, Nigel Haig, Richard Macrory, Eckard Rehbinder, Alan Boyle, Andrew Waite, Pascale Kro- marek, Rita Raum-Deyrkve, Vasili Cos- topoulos and Stanley Clinton-Davis.For further information contact Elaine Hendry, Legal Studies and Services Ltd., Bath House, 56 Holborn Viaduct, Lon- don EClA 2EX. Instrumentation Exhibitions 1990 The exhibitions for 1990 will be as follows: “Instrumentation South East” at the Stevenage Leisure Centre on January 25 and 26; “Instrumentation Wales and South West” at the Newport Leisure Centre on February 28 and March 1; “Instrumentation North East” at Gates- head on March 28 and 29; “Instrumenta- tion North West” at Haydock Park on June 20 and 21. For further information contact Norma Thewlis, Trident International Exhibi- tions Ltd., Plymouth Road, Tavistock, Sulphur Dioxide Control Symposium May 8-11, 1990, New Orleans, Loui- siana, USA This symposium will be sponsored by the US Environmental Protection Energy and the Electric Power Research Institute and held in the Sheraton New Orleans Hotel. The intention is to provide for the exchange of information on flue gas desul- phurisation for utility and industrial boil- ers.Wet and dry scrubbers, new and emerging processes and international developments in clean coal - acid rain technologies will be the major topics. The Symposium Co-ordinator is Sharon Luongo, Electric Power Research Institute, 3412 Hillview Avenue, P.O. Box 10412, Palo Alto, CA 94303, USA. Interphex USA ’90 May 9-11, 1990, New York, NY, USA Interphex USA, a major development, processing and packaging exposition serv- ing the pharmaceutical, biopharmaceut- ical and cosmetics manufacturing indus- tries, has announced that its 1990 meeting is scheduled for May 9-11 at New York’s Jacob Javits Convention Center.The 1990 exposition and conference marks Interphex USA’s 10th anniversary meet- ing. For the fourth year, Interphex USA ’90 will feature the Biopharmaceutical Show- case. This “show within a show” is devoted to the special services and requirements of biopharmaceutical pro- ducts, the fastest growing segment of the pharmaceutical industry. A new Process Automation Center, featuring computer integrated manu- facturing (CIM) systems for automated manufacturing and processing of pharma- ceuticals and cosmetics, is a special show- case of Interphex USA ’90. Exhibitors Exposition Group, P.O. Box 5060, Des Plaines, IL 60017-5060, USA, for further information. RoSPA International Safety and Health Exhibition and Congress May 22-24, 1990, Birmingham This meeting will take place at the National Exhibition Centre.It is the largest annual event of its kind in Europe and covers all aspects of safety and health in the chemical and plastics industry. For further congress information con- tact Glenis Kendal, RoSPA (Tel: 021- 200-2461). XI CANAS July 29-August 4, 1990, MOSCOW, USSR This conference, which will be held at the Cosmos Hotel, will include oral presenta- tions on the following subjects: Atomic Emission Spectrometry; Atomic Absorp- tion Spectrometry; Atomic Fluorescence Spectroscopy; Lasers in Analytical Atomic Spectroscopy; X-ray Spectro- scopy. It is hoped that there will also be an exhibition of publications.Abstracts of potential papers should be sent to the address given below by December 1, 1989. For information write to Dr. E. M. Sedykh, Vernadsky Institute of Geo- chemistry and Analytical chemistry of the USSR Academy of Sciences, 117975 GSP-1, Kosygin Str., 19, Moscow V-334, USSR. 36th Canadian Spectroscopy Conference August 1-3,1990, St. Catharines, Ontario, Canada This conference will be held at Brock University. Contributions from all areas of atomic and molecular spectroscopy are Devon PL19 8AU. should contact Lee Langhorst , Cahners invited. The following sessions are-beingANALYTICAL PROCEEDINGS, SEPTEMBER 1989, VOL 26 327 organized: Analytical Atomic Spectro- scopy; Inductively Coupled Plasma Mass Spectroscopy; Applications of Fourier Transform Infrared Spectroscopy; Liquid Chromatography - Mass Spectroscopy- Advances; Spectroscopic Methods in Archaeometry; Applied Nuclear Mag- netic Resonance; Industrial Applications of Spectroscopy; Environmental Applica- tions of Spectroscopy; Advances in Mass Spectrometry; New Techniques for Ultra- trace Determinations.Authors should submit approximately 250-word abstracts, in duplicate, before March 1, 1990. In case of multiple authorship, underline the name of the speaker. Abstracts and pro- gramme enquiries to: Ian D. Brindle, Chemistry Department, Brock Univer- sity, St. Catharines, Ontario, Canada L2S 3A1. First Changchun International Sympo- sium on Analytical Chemistry August 7-1 1, 1990, Changchun, P. R. China The First Changchun International Symposium on Analytical Chemistry will provide a major forum for academic exchange on analytical chemistry.Key developments in the field will be high- lighted by ten world renowned invited plenary speakers; these will be supported by contributed presentations from dele- gates in daily sessions devoted to such broad topics as atomic spectroscopy, automatic analysis, bioanalytical chem- istry, chemometrics, chromatography, clinical chemistry and drug analysis, electroanalytical chemistry, environ- mental analysis, food analysis, magnetic resonance spectroscopy, mass spectro- scopy, molecular spectrometry, surface analysis, teaching and education in analy- tical chemistry, trace analysis, X-ray spec- trometry, etc. There will be an exhibition of modern analytical instrumentation.A full social programme is also arranged to complement the symposium agenda. The symposium is sponsored by the State Education Commission of China, the Chinese Academy of Sciences and the Chinese Chemical Society and organised by Jilin University and Changchun Insti- tute of Applied Chemistry of the Chinese Academy of Sciences. For further infor- mation and registration forms please con- tact: Professor Qinhan Jin, Department of Chemistry, Jilin University, Chang- chun, Jilin 130021, P.R. China. Biotech UK September 24-27’ 1991, Leeds Biotech UK will be held at the University of Leeds. BCCB, the organising body, is a coordinating organisation which seeks to advance and encourage the biotechnology interests of all the leading scientific and technical societies and institutions in Bri- tain.Biotech UK is being planned to provide BCCB members with their own setting for free discussion and for the high-level exchange of up-to-the-minute information and opinion, at a cost which will be compatible with their resources. This pattern of meetings is one which BCCB’s different member organisations have traditionally afforded for their own members, but which for biotechnology must reach across their traditional subdi- visions of science and technology. In an associated exhibition, the trade stands will give UK companies an important opportunity to offer equipment and ser- vices, and also to recruit staff with the required skills, in this key economic sector. Central organisational facilities for Biotech UK are being provided by the Society of Chemical Industry from their Belgrave Square Conference Office.For further particulars contact: Biotech UK Information, c/o J. D. Bu’Lock, The University, Manchester M13 9PL. Festoff Colloquium Wetzlar October 8-10, 1990, Jiilich, FRG The subject of the Fourth International Colloquium will be Solid Sampling with Optical Atomic Spectroscopy. The main topics discussed will be: Theory and Instrumentation; Methodology and Procedures; Biological and Medical Applications; Food Applications; En- vironmental Applications; Product and Quality Control; and Production and Use of Certified Reference Materials. For further information write to Festoff Colloquium Wetzlar, Kernforschungsan- lage Julich GmbH, Julich, FRG. XXVII Colloquium Spectroscopicum Internationale June 9-14, 1991, Bergen, Norway The next in this series of conferences will take place in the Grieg Hall, Bergen. Papers are invited dealing with the basic theory and instrumentation of atomic spectroscopy (emission, absorbance or fluorescence), molecular spectroscopy (ultraviolet, visible and infrared), X-ray spectroscopy, gamma spectroscopy, mass spectrometry (inorganic and organic), electron spectroscopy, Raman spectro- scopy, Mossbauer spectroscopy, nuclear magnetic resonance spectrometry, methods of surface analysis and depth profiling and photoacoustic spectroscopy. Applications papers are sought on metals and alloys, geological materials, indus- trial products, biological samples and food and agricultural products. The invited speakers will be M. de Bruin, H. Falk, M. Grasserbauer, H. Haraguchi, W. W. Harrison, B. Huang, S. A. Johans- son, T. Kantor, P. Larkins, B. V. L’vov, J. W. Mclaren, J.-M. Mermet, N. M. M. Nibbering, M. Omenetto, J. C. Riviere, B. Schrader and M. Stoeppler. For further information contact XXVII CSI, HSD Congress-Conference, P.O. Box 1721 Nordnes, N-5024 Bergen, Nor- way.

ISSN:0144-557X    

DOI:10.1039/AP989260326b

出版商:RSC    

年代:1989

数据来源: RSC

摘要:

ANALYTICAL PROCEEDINGS, SEPTEMBER 1989, VOL 26 327 Courses Coal Utilisation October 44,1989, Zeist, The Netherlands The course is aimed at engineers and scientists who face problems related to industrial applications of coal, in parti- cular, combustion and gasification. Modem innovative techniques will be highlighted starting from a firm scientific basis, and attention will be paid to envi- ronmental impact. No specific knowledge of coal and coal processes will be required. Further information on this course can be obtained from The Conference Section, The Institution of Chemical Engineers, 165-171 Railway Terrace, Rugby CV213HQ. Training in Rubber and Plastics 1989, Shrewsbury Following the successful launch into for- malised training courses this year, RAPRA Technology is to run two further courses on Plastics Materials and Pro- ducts late in the year, and will also introduce a Rubber Materials and Pro- ducts course.The 2-day courses, which will be held at RAPRA’s Shawbury head- quarters, are aimed at product design engineers with little or no knowledge of plastics or rubber materials. The course tutors themselves are constantly involved in problem solving consultancy involving these materials and are therefore able to pass on their knowledge gained through first-hand experience. The Plastics Materials and Products Courses cover: Plastics Materials; Materials Selection; Design for Perfor- mance; Failure Diagnosis; Processing and Process Selection; Design for Injection [continued inside back cover] Moulding.ANALYTICAL PROCEEDINGS. SEPTEMBER 1989, VOL 26 ...111 Courses, continued The Rubber Materials and Products Courses cover: Introduction to Rubber Technology; Guide to Materials Selec- tion; Compounding and Vulcanisation; Processing; Design for Performance; Fai- lure Diagnosis; Testing and Specifica- tions. The course dates are Plastics, October 10-11, 1989, and November 14-15, 1989; Rubber, November 21-22. 1989, and December 5-6, 1989. Course fees arc f3.50 (+ VAT in the UK) per attendee for the 2-day course. The fee covers lecture notes, lunches and coffees. For more information on these courses and on other customised on-site training available from RAPRA, contact Christine Green, Training Co-ordinator, RAPRA Technology Ltd., Shawbury, Shrewsbury, Shropshire SY4 4NR. Postgraduate Course in Cosmetic Science Ncniember 5-10, 1989, Bournemouth This course, which will be organised by the Society of Cosmetic Scientists, will be held at the Heathlands Hotel, Grove Road, Bournemouth.It will include 14 lectures and 12 seminar sessions. For details contact The General Secretary, The Society of Cosmetic Scientists, Delaport House, 57 Guildford Street, Luton, Bedfordshire LU1 2NL. ICP Spectrochemical Analysis: Water and Environmental Materials November 21-24, 1989, Sheffield A laboratory based course on this subject will be held in Sheffield City Polytechnic; the fee will be fS85.00. Further details are available from the Short Course Support Unit, Sheffield City Polytechnic, 43 Broomgrove Road, Shef- field SIO 2NA. Atomic Absorption Spectrometry December 11-IS, 1989, Loughborough The fee for this course, which will take place in the Chemistry Department of the University of Technology, is f530 includ- ing residence and all meals or f450 for non-residents (although a reduction of f30 is made for payment with the booking form). For further details contact Mrs. J . E. Stirling, Department of Chemistry, Loughborough University of Technology, Loughborough, Leicestershire LE 1 1 3TU.

ISSN:0144-557X    

DOI:10.1039/AP9892600327

出版商:RSC    

年代:1989

数据来源: RSC

摘要:

328 ANALYTICAL PROCEEDINGS, SEPTEMBER 1989, VOL 26 Analytical Division Diary SEPTEMBER Tuesday to Thursday, 26th to 28th: Loughborough Analytical Division. RSC Autumn Meeting. Sample Preparation and Presentation. Tuesday 26th-Session 1 : Environmental “Sample Preparation for Environmental Chemistry,” by M. “Digestion of Heterogeneous Matrices to Produce a Sample for “Problems Associated with the Extraction of an Organic Analyte “Letting the Punishment Fit the Crime,” by T. E. Edmonds. Wednesday 27th-Session 2: Atomic Spectroscopy “Sample Preparation for Atomic Spectroscopy ,” by M. Thompson. “New Approaches to Sample PreparatiodPresentation in ICP “Understanding the Importance of Contamination in Atomic “An Appraisal of Direct Introduction of Solids into ICP Sources ,” Wednesday 27th-Session 3: Radiochemistry “Liquid Scintillation Counting,” by P.Warwick. “a-Counting,” by A. Lalley. “y-Counting,” by G. Sutton. “Activation Analysis,” by D. Green. Thursday 28th-Session 4: Chromatography “On-Line Sample Preparation for Enhanced Sensitivity and Sensi- “Supercritical Fluid Extraction of Herbal Medicines,” by R. M. “Combustion in Ion Chromatography,” by J. P. Senior. “Speciation Studies of Metals in Foodstuffs,” by R. Massey. University of Technology, Loughborough. Registration is necessary. Contact: Dr. J. F. Gibson, Royal Society of Chemistry, Burlington House, Piccadilly, London W1V OBN. (Tel. Cresser. Multi-component Metals Analysis,” by M. Kibblewhite. from an Inorganic Matrix,” speaker to be announced. Spectrometry,” by C. W.McLeod. Spectroscopy.” by C. W. Fuller. by C. Pickford. tivity in HPLC,” by U. Brinkman. Smith. 01 -437-8656). Friday, 29th: Uxbridge Micro & Chemical Methods Group. Elemental Analysis User Forum. Meeting to include: What’s New in Elemental Analysis?; Determi- Brunel University, Uxbridge. Contact: Mr. P. R. W. Baker, 55 Braemar Gardens, West nation of Phosphorus; Determination of Fluorine. Wickham, Kent BR4 OJN. (Tel. 01-777-1225). OCTOBER Wednesday, llth, 9.30 a.m.: Liverpool North West Region. Chemical Analysis in Oceanography. “Analysis of Organic Pollutants in Estuarine and Marine Systems,” “Analysis for Gaseous Sulphur and Halogen Compounds in Sea ‘‘Analytical Methods Used in Hydrocarbon Monitoring in the North “Coupled Analytical Techniques.” by S. Hill.“Analysis for Alkyl Tin Compounds,” by M. Waldock. “CSV Analysis of Ultra-trace Levels of Metals in Sea Water.” by Derby and Rathburn Hall, Greenbank Road, The Univer- by M. Preston. Water,” by P. S. Liss. Sea, by R. Law. C. M. G. van den Berg. sity, Liverpool. Registration is necessary. Cost to non-members of the RSC f45, members of the RSC &35 and full-time students and retired members f10. Contact: Dr. P. J. Whittle, 6 Marian Drive, Rainhill, Prescott, Merseyside L35 ONB. [Tel: 0925-828744 (Busi- ness) and 051-430-6490 (Home)]. Tuesday, 17th, 10.30 a.m.: Welwyn Micro & Chemical Methods Group. Trace Analysis in Biological and Environmental Matrices. “Trace Analysis: Problems and Solutions,” by A. Townshend. “Total Reflection X-ray Fluorescence Spectrometry: A New Analy- tical Tool for Multi-elemental Trace Analysis,” by S .J. Haswell and S. Mukhtar. “Potentiometric Anion Sensing; Prospects and Limitations for Trace Analysis,” by J . D. R. Thomas. “Trace Organics from Biological Sources,” by N. J. Haskins. “Trace Analysis of Organic Compounds in Aquatic Sediments,” by “Trace Metal Speciation in Environmental Samples,” by L. C. Smith Kline and French Research Ltd., The Frythe, Registration is necessary. Cost f 5 to RSC members and f30 Contact: Mr. P. R. W. Baker, 55 Braemar Gardens, West G. Eglinton. Ebdon, S. J. Hill and S. Branch. Welwyn, Hertfordshire. to non-members. Wickham, Kent BR4 OJN. (Tel: 01-777-1225). Thursday, 19th: London Joint Pharmaceutical Analysis Group. Short Papers in Pharmaceutical Analysis.Royal Pharmaceutical Society of GB, 1 Lambeth High Registration is necessary. Contact: Royal Pharmaceutical Society of GB, 1 Lambeth Street, London SE1 6NJ. High Street, London SE1 6NJ. (Tel. 01-735-9141). Thursday, 19th, 5 p.m.: Plymouth Western Region, jointly with the Peninsula Section of the Speaker: D. Littlejohn. General Purpose Teaching Block, Polytechnic South West, Plymouth. Contact: Mr. F. W. Sweeting, Wessex Water Authority, Regional Scientific Centre, Mead Lane, Saltford, Bristol BS18 3ER. (Tel. 0225-873692, Ex. 124). RSC. Tuesday, 24th, 10 a.m.: London Analytical Division, organised by the Biological Methods Alternative-site Diagnostic Testing. “Initiatives and Developments in Site-diagnostic Testing,” by B. “Home or Surgery-based Cancer Diagnostics,” by M.J. Hill. “Biosensors,” by L. Russell. “Evolution of Home Diagnostics from Laboratory to Market Place,” by S. Arlington. Group. Morris. [continued inside back cover]... ANALYTICAL PROCEEDINGS. SEPTEMBER 1989, VOL 26 111 Analytical Division Diary, continued October, continued "Species Origin of Imported Meat," by R. Patterson. "Rapid Diagnostic Tests Employing Latex Particles," by J . Carney. "Zn-vi\w Bioluminescence Using the Lux-Gene System," by A. Smith. "Enhanced Lumincscent Immunoassays for Environmental Moni- toring." by W. Aherme. "Immunoassay of Amino- and Nitro-aromatics (ForensidMoD Applications)." by N. Stewart. Scientific Societies' Lecture Theatre, 23 Savile Row (entrance in New Burlington Place), London W1. Registration is necessary. Costs are $20 to members of the RSC, &35 to non-members and $10 to student and retired members. Cuntact: Miss P. E. Hutchinson, Analytical Division, Royal Society of Chemistry, Burlington House, Piccadilly, Lon- don WlV OBN. (Tel. 01-437-8656). Tuesday, 24th, 11 a.m.: Bristol Western Region, jointly with the South West Region of the Chemicals for the Electronics Industry. The University, Bristol. Registration is necessary. Cost f30 to RSC members and f50 to non-members. Contuct: Dr. Susan Pringle, Department of Extra Mural Studies, University of Bristol, Wills Memorial Building, Queens Road, Bristol BS8 1HR. (Tel. 0272-303611). lndustrial Division.

ISSN:0144-557X    

DOI:10.1039/AP9892600328

出版商:RSC    

年代:1989

数据来源: RSC