摘要:

Proceedingsof the Analytical Division ofThe Chemical Society241241241246255257258258259260262CONTENTSEditoria I : Proceedings-Feat uresSummaries of Papersand Finance" D at a Ac q u i s i t i o n and Processing ""Pollution and Water Chemistry""Educational Technology in theService of Analytical Chemistry"AD Distinguished Service AwardPublic Analysts' FeesConferences and MeetingsPublications ReceivedChemical Society LibraryAnalytical Division DiaryVolume 12 No 9 Pages 241 -262 September 197PADSDZ 12(9)241-262(1975)ISSN 0306-1 396ISBN 0 85990 704 xObtainable from The Publications Sales Officer,The Chemical Society, Blackhorse Road, Letchworth, Herts., SG6 1 HNMembers of the Chemical Society are entitled to buy one copy fortheir own personal use at the special price of f14.50 (U.S.$36.50).provided they order direct and enclose remittance.ISeptember 1975PROCEEDINGSANALYTICAL DIVISION OF THE CHEMICAL SOCIETYOF THEOfficers of the Analytical Divisionof the Chemical SocietyPresidentG . W. C. MilnerHon. SecretaryP. G. W. CobbSecretaryMiss P. E. HutchinsonHon. Treasurer Hon. Assistant SecretariesJ. K. Foreman D. I. Coomber, O.B.E.; D. W. WilsonEditor, ProceedingsP. C. WestonProceedings is published by The Chemical Society.Editorial: The Director of Publications, The Chemical Society, Burlington House, London, W1 V OBN.Telephone 01 -734 9864. Telex 268001.Subscriptions (non-members) : The Chemical Society, Publications Sales Office, Blackhorse Road, Letch-worth, Herts., SG6 1 HN.Non-members can only be supplied with Proceedings as part of a combined subscription with The Analystand Analytical Abstracts.@ The Chemical Society 1975Official,Standardised andRecommendedMethods of AnalysisSECOND EDITION (1 973)Compiled and Edited for4THE ANALYTICAL METHODS COMMlmEEofbvThe Society for Analytical ChemistryPo. xxiv + 897N. W. Hanson, BSc, PhD, FRIC f17.00; U.S. $42.5

ISSN:0306-1396    

DOI:10.1039/AD97512FX031

出版商:RSC    

年代:1975

数据来源: RSC

摘要:

September, 1975 ANALYTICAL DIVISION DIARY 261Analytical Division Diary, continuedOctober, continuedThursday, 16th, 2 p.m.: LondonBiological Methods Group on “Oncofoetal“Concept of Oncofoetal Antigens,” by M. R.“Assay of Oncofoetal Antigens,” by D. J. R.Antigens.”Price.Lawrence.“Oncofoetal Antigens and Human Neo-“Concept of Tumour-specific Antigens,’ ’ by“Principles of Immuno-therapy,” by P. T.Pharmaceutical Society of Great Britain, 17plasia,” by P. W. Dykes.M. Moore.McElwayn.Bloomsbury Square, London, W.C. 1.Tuesday, 21st, 6 p.m.: NottinghamMidZands Region on “The Analytical Chem-istry of Glass: Its Detection, Identifica-tion and Uses.”“The Quantitative Analysis of Glass Availablein Milligram, Gram and Bulk QuantitiesUsing X-ray Fluorescence,” by D.G.Ashley.“Forensic Examination of Glass,” by R. K.Bramley.The Boots Co. Ltd., Pennyfoot Street,Nottingham.Wednesday, 22nd, 11 a.m. : ColchesterEast Anglia Region, jointly with the EasternRegion of the Industrial Division, on“Applications of Analytical Techniques toIndustrial Effluents.”“Organic Carbon and Oxygen DemandAnalyses and their Relationships in Efflu-ents,” by G. F. Lowden.“The Continuous Monitoring of EffluentsUsing Ion-selective Electrodes,” by M. E.Hofton.“Automated Analysis of Effluents; the Prosand Cons,” by F. J. Whitby.“Studies of Oils and Polycyclic AromaticHydrocarbons (PAH) in Sewage-relatedSystems,” by D. Meek.University of Essex, Wivenhoe Park, Col-ches terAnalytical Division DiarySEPTEMBERMonday and Tuesday, 22nd and 23rd:LondonA tomic Spectroscopy, Microchemical Methodsand Radiochemical Methods Gqoups on“Analysis in Archaeology, Art and Anti-quities .’ ’Monday, 22nd-“Analysis and Archaeology,” by J.Musty.“Thermoluminescence Dating,” by M. J .Aitken.Friday, 3rd, 2 p.m.: ChorleyNorth West Region, jointly with the Associ-ation of Public Analysts, on “Analyticaland Microbiological Aspects of FoodstuffControl.”“Frozen Food,” by R. B. Sparnon.“Non-frozen and Chilled Foods,” by B.“Chemical and Microbiological Tests onJarvis.Foodstuffs,” by J. Markland.Heskin Hall, Chorley, Lancs.“Mossbauer Spectroscopy in Archaeology,”Tuesday, 23vd-“X-rays and Antiquities,” by H. Barker.“Electron Microprobe Analysis,” by R.E. M.“Activation Analysis and Archaeometry,” by“Potential Analysis of Museum Objects byConducted tours of the British Museum followed by-by N. J. Seeley. Tuesday, 7th, 6.30 p.m. : BirminghamMidlands Region : Silver Medal Lectures (forLecture Theatre 101, Haworth Building, Thetitles see above).Hedges University, Birmingham.G. R. Gilmore.ESCA,” by M. Thompson. East A nglia Region : Annual General Meeting,Research Laboratories or selected galleries “Applications of Mass Spectrometry toof the British Museum. Research in Food and Agriculture,” byBloomsbury, London W.C. 1.Wednesday, 8 t h 3 p.m.: NorwichThe Lecture Theatre, The British Museum, R. Self.Food Research Institute, Norwich.Monday to Thursday, 22nd to 25th: ReadingCS Autumn Meeting.Thursday, 25th : Sym-posium organised by the AD, in con-junction with the Education Division, on“Trends in Education in Analytical Chem-istry. ’ ’For details of the meeting, see August issue,p. 236.OCTOBERWednesday, lst, 2.30 p.m.: LondonAnalytical Division : Silver Medal Lectures.“Atom Formation and Interferences in Flameand Carbon Furnace Atomic Spectro-metry,” by J. M. Ottaway.“Analytical Applications of Some UnusualMolecules, ’ ’ by A. Townshend .Scientific Societies Lecture Theatre, 23 SavileRow, London, W. 1.Thursday, 2nd, 4.30 p.m.: EdinburghScottish Region : Silver Medal Lectures (forDepartment of Chemistry, King’s Buildings,titles see above).The University, Edinburgh.Wednesday, 8th, 2.30 p.m. : LondonAutomatic Methods Group on “Sampling-Problems and Solutions.”Speakers to include: F. R. B. Fearn, J . R. P.Clarke and W. Page.Chelsea College of Science and Technology,University of London, Manresa Road,London, S.W.3.Thursday, 9th, 5.30 p.m.: CardiffWestern Region.“Tricks of the Trade,” by R. A. Chalmers.University of Wales Institute of Scienceand Technology, Cardiff.Friday, loth, 7 p.m.: DurhamNorth East Region : Social evening.Dinner, followed by a talk by F. Atkinson.Royal County Hotel, Durham City.[continued inside back coverPrinted by Heffers Printers Ltd Cambridge Englan

ISSN:0306-1396    

DOI:10.1039/AD97512BX033

出版商:RSC    

年代:1975

数据来源: RSC

摘要:

Vol. 12 No. 9 September 1975 Data Acquisition and Processing The following are summaries of two of the papers presented at an Ordinary Meeting of the AD held on April 14th and 15th and reported in the May issue of Proceedings (p. 136). Automated Reaction Rate Measurements Alan Townshend Chemistry Department. University of Birmingham, P.O. Box 363, Birmingham, B16 2TT Reactants and catalysts can often be determined by their effect on the rate of a reaction.W Such methods are not popular, however, because of an ill-founded suspicion that measurements on non-equilibrium systems are imprecise and, more reasonably, that it is more difficult and time consuming to extract analytical data from kinetic measurements than those obtained from static systems.These disadvantages are eliminated by using completely automated systems.241242 DATA ACQUISITION AND PROCESSING PYOC. AnaZyt. Div. Chem. SOC. High-precision monitoring devices (usually spectrophotometers) allow small changes in signal to be measured, so that the measurement time can be very brief. Dedicated computational and instrumental control facilities give completely automatic analysis, including the treatment of rate data to give concentration information.Because of the non-linear nature of most kinetic response curves, i.e., the rate of change of signal decreases continuously as the reaction proceeds, rates are usually measured by: (a) the instantaneous rate of change of signal with time (AS/At) ; (b) the change in signal, AS, within a $xed time interval; or (c) the time, At, required to traverse a$xed proportional change in signal.The signal is usually the voltage output of a spectrophotometer. In a first-order reaction, AS/At and AS are proportional to concentration, but At is inversely proportional to concentra- tion. For enzyme-catalysed reactions in the presence of large concentrations of substrate, the reaction becomes zero order and the response curve becomes linear.Hence only the gradient of this straight line has to be measured in order to ascertain the rate. Automatic monitoring devices based on the above procedures can be devised for making instantaneous measurements of the necessary time or output signals. Such devices give im- precise and inaccurate data because of noise; premature triggering of measuring circuits by signal “spikes” is particularly troublesome.Integration of the signal over a period of time appreciably greater than the period of the noise largely avoids such effects. Integrated measurements are simply achieved for linear (zero-order) response curves, and are accomplished by many commercial “kinetics” analysis systems. For non-linear response curves, data aquisition and treatment are more complicated; they differ in concept for each of the above measurement procedure^,^^^ and, in general, dedicated equipment for this purpose is not commercially available.For fixed time measurements, two segments of the response curve separated by a fixed time interval, At, are each integrated for time ti (ref. 5 ) . The rate is proportional to AI( Att, + t,2)-1, where AI is the difference between the two integrated signals.As At and ti are constant, the rate is proportional to AI. If At is reduced to zero, an essentially instantaneous slope measure- ment is achieved, the rate being proportional to AItiU2. With the use of such an analowe system (5-s integration periods and pre-measurement delay 30 s) 5-15 p.p.m. of phosphate were determined by the rate of molybdophosphate reduction and 5-20 p.p.m.of glucose were determined enzymatically, with a precision of 0.2 p.p.m. Ingle and Crouch6 developed a digital system based on the same measurement principle in which the output signal voltage is converted into a frequency. The number of counts accumulated in a given time interval is subtracted from that accumulated in a later, identical, time interval and the difference is proportional to the rate.For counting periods of 0.2-20 s, a precision of 0-3 per cent. was achieved. A noise level of 60Hz (sine wave) with an amplitude five times that of the measured voltage change had a minimal effect on accuracy and precision. Flow systems, such as the Technicon AutoAnalyzer, are by definition fixed time systems, but they are not discussed here.Fixed proportional change measurements require a clock, and computational facilities for calculating t-l. The earliest automated device for such measurements’ was electromechanical. When the output signal reached a predetermined value, a synchronous motor was switched on and turned the shaft of a variable potentiometer, the output from which was fed to an inverter.When the signal reached a second pre-determined value, the motor was switched off, so that the final output from the inverter was proportional to t-l. Addition of a variable resistance and appropriate software gave a print-out in concentration. With such a system, osmium (1-10 p.p.b.) was determined by its catalysis of the arsenic(II1) - cerium(1V) reaction, in 15-150 s, with a precision of 0.07 p.p.b., using a stabilised spectrophotometer.Several electronic computing systems have been described for converting t into t-1 with much greater response speeds than the electromechanical device. They involve the following conversion sequences : ,-+ d(1og V ) = V-l cc t-l (ref. 8) t --f voltage (V) 3 log V -+ - log V -+ exp(- log V ) K t-1 (ref.9) 1 frequency -+ period cc t-1 (ref. 10) An all-digital system has recently been described,ll based on a crystal clock, which gives as It has a limiting response time of 10 ps. an ultimate output a frequency proportional to t-l.September, 1975 DATA ACQUISITION AND PROCESSING 243 Noise and spike effects are eliminated because the measuring circuit is open only when the out- put signal is within a pre-determined range.Thus, a spike activates or inactivates the device for a negligible time, and random noise is effectively averaged out. Measurement times for determinations of alkaline phosphatase in sera averaged about 3 min; the shortest time interval required was 0.5 s and the coefficient of variation was less than & 1 per cent.Such automated rate measurements can be very fast, and throughput of samples will be restricted by sample handling and mixing in such instances. Faster sample handling can be achieved by centrifugal spectrophotometers and, probably more effectively, by stopped-flow measurements combined with a rapid sample injection system. The stopped-flow system achieves extremely rapid mixing of solutions, thus reducing the delay before which measure- ments can be carried out, and allowing much more rapid reactions to be monitored.Javier et aE.12 described a completely automated system in which samples are injected, mixing is complete in 2 ms and measurements based on fixed proportional change are completed in < 0.7 s. Reproducibility was < & 1 per cent., and the rate of sample throughput very high (about one per second).As faster reactions can be used, phosphate can be determined by the rate of formation of 12- molybdophosphoric acid. Interferences from silicate and arsenate are avoided in this determination, because they form heteropoly acids much more slowly, and so react to only a negligible extent in the brief measuring period.The solution is then ejected, and the next determination initiated. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. References Mark, H. B., and Rechnitz, G. A., “Kinetics in Analytical Chemistry,” Interscience, New York, 1968. Yatsimirskii, K. B., “Kinetic Methods of Analysis,” Pergamon Press, Oxford, 1966. Pardue, H. L., in Reilley, C. N., and McLafferty, F. W., Editors, “Advances in Analytical Chemistry Malmstadt, H.V., Delaney, C. J., and Cordos, E. A., Analyt. Chem., 1972, 44 (Oct.), 79A. Cordos, E. M., Crouch, S. R., and Malmstadt, H. V., Analyt. Chem., 1968, 40, 1812. Ingle, J . D., and Crouch, S. R., Analyt. Chem., 1970, 42, 1055. Pardue, H. L., Frings, C. S., and Delaney, C. J., Analyt. Chem., 1965, 37, 1426. Stehl, R. H., Margerum, D. W., and Latterell, J .J . , Analyt. Chem., 1967, 39, 1346. James, G. E., and Pardue, H. L., Analyt. Chem., 1968, 40, 796. Crouch, S. R., Analyt. Chem., 1969, 41, 880. Parker, R. A., Pardue, H. L., and Willis, B. G., Analyt. Chem., 1970, 42, 56. Javier, A. C., Crouch, S. R., and Malmstadt, H. V., Analyt. Chem., 1969, 41, 239. and Instrumentation,” Interscience, New York, 1969, Volume 7, p.144. Applications of I3C and IH Nuclear Magnetic Resonance and Infrared Spectroscopy in Structural and Quantitative Analysis 1. K. O’Neill Laboratory of the Government Chemist, Cornwall House, Stamford Street, London, SE 1 9NQ Of the various techniques available to the chemist for structural identifications or specific assays, nuclear magnetic resonance (NMR) and infrared (IR) spectroscopy are particularly important.These non-destructive techniques are complementary, because with IR one observes stretching and bending within molecules while with 13C NMR and lH NMR one observes nuclei in the molecular skeleton and at its periphery. High resolving powers are found, particularly with IR and 13CNMR, and thus these techniques meet the analyst’s requirement for high informing power1 in handling a wide variety of unfamiliar situations.This Laboratory must cover the whole range of chemical endeavour and these methods have proved to be widely applicable. Data acquisition and processing methods enhance the effectiveness, and four separate areas of current interest are briefly discussed. 13C NMR Spectroscopy Although lH NMR spectrometers were developed nearly two decades ago, 13C NMR spectros- copy became significant only with the introduction of pulse Fourier transform techniques2 and of inexpensive computers.In the last 5 years, this spectroscopic method has grown dramatic- ally as a consequence both of direct skeletal observation3 and the much greater resolving244 DATA ACQUISITION AND PROCESSING PYOC. Analyt.Div. Chem. SOC. power that is achievable compared with lH NMR spectroscopy. The role of the computer has changed from an accessory to a fundamental spectroscopic component that controls the experi- ment, acquires data and provides real-time processing and display. Full details are to be found elsewhere*; briefly, the sample is subjected to a short intense radiofrequency pulse and the decay of the induced magnetisation is detected and then Fourier transformed to yield the frequency spectrum.For 13C NMR spectroscopy, the required sensitivity is achieved by co- addition and apodisation of many such decays and also by simultaneous irradiation of the hydrogen nuclei.5 The latter process destroys the 13C - lH spin - spin coupling and the result- ing 13C NMR spectrum consists of one sharp line for each chemically distinct carbon atom in the molecule.The number of hydrogen atoms directly attached to each carbon is found by re-introducing 13C - lH coupling through time6 or frequency7 modification of the 1H irradiation channel. Further structural information is provided by determination of the 13C nuclear relaxation times for each carbon atom, this time being strongly dependent upon the relative mobility of segments of the molecule.Thus the chemist obtains extensive information through examination of these parameters and all this is now largely achieved through software control of pulsing and data acquisition. Several commercially available instruments now allow the chemist to control readily such equipment through real-time manipulations with oscilloscope displays and also to use smoothing, integration and data reduction routines with the spectra.1% NMR chemical shifts are affected relatively little by sampling conditions but greatly by skeletal changes, Spectra obtained in the lH decoupled mode have line widths of less than 0.04 p.p.m. in a total13C spectral width of more than 200 p.p.m., thereby giving excellent resolv- ing power such that even steroids usually have every carbon atom resolved and assignable.9 For these reasons, the data should be eminently suitable for file searching, but 13CNMR spectroscopy is still relatively new and there is no large collection generally available for this purpose.Successful file searching has been reported,1° but of greater significance are reports of correlation of chemical shift with molecular structure in a variety of chemical classes.11 Sasaki et aZ.12 and Carhart and Djerassi13 have reported successful structure building programmes that start with the molecular formula and generate possible structures, using the 13C NMR data with predictive rules so as to produce ordered lists. Clearly, the use of partial structures found with other techniques such as lH NMR and IR spectroscopy reduces the number of possible structures generated and thereby expedites this process.A partial system has been developed14 for use in a 13C NMR computer with light-pen control and shows considerable promise for the determination of organic structures. lH NMR Quantitative Analysis Several advantages are found in using lH NMR spectroscopy for quantitative organic analysis and an accessory has been devised here for direct data acquisition and processing.15 1H NMR spectroscopy16 is inherently quantitative as the energy absorbed by hydrogen nuclei is independent of the chemical environment and so the technique has been used to proportion the components of mixtures for some years.17 Recently, the method has been used18 for many pharmaceutical assays by adding known amounts of internal standards, which can be any pure substance that absorbs in a convenient region of the spectrum.Specificity and ease of sarnp- ling19 make the technique sufficiently attractive for repetitive analyses of pharmaceutical single doses that automation has become desirable.A device has been designed to take the NMR signal directly from the spectrometer in pre-specified zones during repetitive sweeps and to combine it with the information of masses and equivalent weights in order to calculate sample purity. The device incorporates a digital integrator found to be more accurate than the capacitative integrators usually built into NMR spectrometers.It also does not detract from the flexibility of the NMR quantitation method so that one can efficiently assay unfamiliar samples without the need for pure specimens. IR Spectroscopy Although NMR spectroscopy is very important for determining fine details of organic structure, IR spectroscopy offers the most general first approach to unknown substances as it readily yields spectral information of some significance from any solid, liquid or gas and is not element-selective, Consequently, there are vast collections of IR spectra Commercially avail-Se$tember, 1975 DATA ACQUISITION AND PROCESSING 245 able €or file-searching routines and we use both a hard-copy collection of 80 000 and a computer- stored collection of 120 000 spectra.We find the latter to be far more successful than manual searching in matching with spectra already in file and also to give useful indications for sub- stances for which no spectrum is filed.Although most IR absorptions of a large molecule are not assignable20 to specific absorption modes, the skeletal absorption fingerprint can be rela- tively unaffected by the exact nature of substituent groups and so the several related sub- stances often present can emerge high on the ordered list.IR spectra can be digitally repre- sented variously from the minimal form of, say, the six strongest absorption positions all the way to a process of peak stripping andsubsequent classification of absorption position, intensity and half-width.21 The commercial system used here has been developed from Erley’s work28 and classifies major and minor peak positions, and also no-peak areas and some chemical data: the search product is a scored list of the 20 best hits.Success is very dependent on the purity of the unknown material and on accuracy of both data input and the file data, and the very large size of the data file increases the chance of other substances scoring higher than the correct match.Thus the final manual check with a hard copy is still essential. Conclusion Manipulation of data has taken organic structure determination much farther than would otherwise have been possible and thereby eased the task of the analyst who needs as much meaningful information as can be provided. While the techniques of data acquisition and processing are valuable with IR searching and 1H quantitation, they are essential with l*C NMR spectroscopy.Extensive hardware and software development has brought l3C NMR spectroscopy into the annoury of the analyst. I acknowledge the assistance of JEOL(UK) and G. Heyden in the preparation of this material and the Government Chemist for authorisation of its release. 1. 2. 3. 4. 5. 6. 7. 8.9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. References Kaiser, H., Analyt. Chem., 1970, 42, 24A. Ernst, R. R., and Anderson, W. A., Rev. Scient. Instrum., 1966, 37, 93. Levy, G. C., and Nelson, G. L., “Carbon-13 Nuclear Magnetic Resonance for Organic Chemists,” Wiley-Interscience, New York, 1972. Farrar, T. C., and Becker, E. D., “Pulse and Fourier Transform NMR,” Academic Press, New York, 1971.Randall, E. M., Chemy Britain, 1971, 371. Feeney, J., Shaw, D., and Pauwels, P. J. S., Chem. Commun., 1970, 564. Levy, G. C., and Nelson, G. L., “Carbon-13 Nuclear Magnetic Resonance for Organic Chemists,” Freeman, R., and Hill, H. D. W., Chem. Phys. Lett., 1970, 53, 4103. Johnson, L. F., and Ja?,kowski. W. C., “Carbon-13 NMR Spectra; A Collection of Assigned, Coded Jezl, B. A., and Dalrymple, D. L., Analyt. Chem., 1975, 47, 203. Martin, G. J., Martin, M. L., and Odiot, S., Org. Mag. Res., 1975, 7, 2. Sasaki, S.. Ochiai, S., Hirota, Y., and Kudo, Y., Japan Analyst, 1972, 21, 916. Carhart, R. E., and Djerassi, C., J . Chem. Soc. Perkin 11, 1973, 1753. Sasaki. S., JEOL News, 1973, lla, 6. U.K. Pat. Appl., 1975, 4740/5. Emsley, J. W., Feeney, J., and Sutcliffe, L. H., “High Resolution Nuclear Magnetic Resonance Kasler, F., “Quantitative Analysis by NMR Spectroscopy,” Academic Press, London, 1973. Kram, T. C., and Turezan, J. W., FDA By-Lines, 1971, 2, 105. O‘Neill, I. K., Pringuer, M. A., and Prosser, H. J., J . Plzarm. Pharmac., 1975, 27, 222. Bellamy, L. J., “Advances in Infra-red Group Frequencies,” Methuen, London, 1968, Preface. Jones, R. N., Pure Apfil. Chem., 1969, 18, 303. Erley, D. S., Analyt. Chem., 1968,40,894. Wiley-Interscience, New York, 1972, p. 9. and Indexed Spectra, Wiley-Interscience, New York, 1972. Spectroscopy,” Pergamon Press, Oxford, 1965.

ISSN:0306-1396    

DOI:10.1039/AD975120241b

出版商:RSC    

年代:1975

数据来源: RSC

摘要:

246 POLLUTION AND WATER CHEMISTRY PYOC. Analyt. Div. Chem. SOC. Pollution and Water Chemistry The following are summaries of five of the papers presented at the Joint Meeting of the Scottish and North East Regions with the Society for Water Treatment and Examination held on February 19th, 1975 and reported in the March issue of Proceedings (p. 74). The Determination of Aluminium in Water by the Method Involving Quinolin-8-01 J.M. Carter The optimum operation of an alum flocculation water-treatment process requires a reliable and reasonably accurate knowledge of the total aluminium content of the water, (a), after sedi- mentation and (b), after filtration. The only methods that are simple and sensitive enough for routine use are colorimetric methods. The fact that most of these methods are unreliable is illustrated by an investigation carried out by the Water Research Ass0ciation.l If a method for the determination of alumiriium is to be suitable for treatment control, the following requiremats should be satisfied: analysis time < 30 rnin; linear calibration; calibration independent of reagent batch; large dynamic range ; detection limit at least 0.01 mg 1-1 of aluminium, without prior concentration (i.e., the blank value should be as low as possible); the method should be robust, i.e., exact adjustment of pH or exact colour development conditions should not be necessary; there should be negligible interference from any other substances commonly found in treated water; and the method should be easy to automate.Most of the methods at present in use in the water industry depend on the formation of a “lake.”5 “Lakes” have long been admitted to be undesirable as (a), they do not obey Beer’s law except over small dynamic ranges and (b), consistent “lake” formation requires very care- fully controlled conditions.A colorimetric method not involving “lake” formation is the quinolin-8-01 method.This method has not found any appreciable application in the water- supply industry despite its successful application in many other fields.6-* A method has now been developed for the determination of aluminium in water, using quinolin-8-01, which satis- fies all the criteria listed above. Interference from iron, manganese and copper is prevented by the use of 1,lO-phenanthroline.Yorkshire Water Authority, Olympia House, Geldered Lane, Geldered Road, Leeds Method To a suitable volume of sample add 5.0 ml of 1 N hydrochloric acid and allow to stand for 5 min. Add 1.0 ml of hydroxylammonium chloride (10 per cent.) - 1,lO-phenanthroline (0.1 per cent.) solution and 2.5 ml of sodium acetate solution (25 per cent.) Mix the reagents well. Check that the pH of the solution is in the range 4-5 with a Universal pH paper.If the pH is low add more sodium acetate solution (10 per cent.) in order to bring it to 4-5. Add 2-0 ml of a 2 per cent. alcoholic solution of quinolin-8-01 and mix well. Extract the solution with 10 ml of chloroform. Allow the phases to separate and run the chloroform through a Whatman No. 1 filter-paper into a 25-ml calibrated flask.Re-extract the aqueous phase with further 5-ml portions of chloroform until a colourless extract is obtained. Combine all the extracts in the 25-ml flask. Dilute the contents of the 25-ml flask to volume with chloroform and mix well. Measure the absorbance of the solutions against water at a wavelength of 390nm. The amount of aluminium in the sample is found from a calibration graph prepared by treating standard aluminium solution exactly as described above.Normally only one 5-ml extraction is necessary. NOTE- (2 per cent. m/V) should be added to the sample. If fluoride or complexing phosphates are thought to be present, 1.0 ml of beryllium sulphate solution Recovery of Aluminium from Natural Waters A fact that emerges from the Water Research Centre report on methods for the determina-September, 1975 POLLUTION AND WATER CHEMISTRY 247 tion of aluminium is that recoveries of aluminium, by almost all methods, were worst when standard aluminium solution is added to tap water rather than distilled water.The pro- posed method has been tested by adding various amounts of aluminium to four different waters. The results of this experiment show that for a wide range of natural waters added aluminium can be recovered with 100 per cent.efficiency, within experimental error. Sample Pre-treatment The method must be capable of determining the aluminium content of water that has been subjected to alum flocculation, both before and after filtration. Thus, it is necessary to determine both dissolved aluminium and suspended aluminium hydroxide.The following forms of sample pre-treatment were tried: (A) , hydrochloric acid (5.0 ml) was added and the solution allowed to stand for 5 min; (B), as (A) but with boiling for 15 min; (C), as (B), using 20 ml of hydrochloric acid; and (D), a wet-destruction technique using 5 ml of sulphuric acid solution (1 + 4) and a few drops of hydrogen peroxide (50 per cent.) Some results obtained by using these techniques for samples of alum-coagulated water, before and after filtration, show that all the pre-treatments used appear to give the same recovery for the samples concerned. Assuming the wet-destruction method to give 100 per cent.recovery, then any of the other pre-treatments also gives complete recovery of aluminium.For this reason and the fact that it is the simplest, pre-treatment (A) is recommended. The other methods all give higher blanks than (A). The standard deviation for the test appears to increase with the degree of treatment. Comparison with Other Methods In the past the quinolin-8-01 method has been rejected for the following reasons: (a), it is insensitive; (b) , solvent-extraction methods are complex and time consuming; and (c) , chloro- form is a volatile solvent, the use of which will give rise to poor reproducibility.If we now examine the criteria given above we can see how they are satisfied by the proposed method and other well known methods for aluminium. The above stated disadvantages of the quinolin-8-01 procedure will also be discussed.It is possible to carry out a sample and blank determination in 15 min. Virtually all other methods for aluminium have a colour development time of at least 10 or 15 min. Thus, far from being time consuming the quinolin-8-01 method is probably the fastest available method. The calibra- tion graph is linear over the range 0-100 pg of aluminium, is highly reproducible and does not vary with reagent batch.Most other methods are very poor on these three criteria. Without any prior sample concentration it is possible to detect 0.001 mg 1-1 of aluminium. This very low limit is due to the concentrating effect of the solvent extraction rather than to the sensitivity of the colour itself. However, it demonstrates that for the determination of aluminium in water the method is the most sensitive available. Robustness of the method.Most methods require very exact pH adjustment^^^^ and often the calibration varies with the alkalinity of the ample.^ The proposed method requires only that the pH be in the range 6 5 . All methods familiar to the author suffer from interference due to fluoride, hexametaphosphate and Calgon. These materials must be removed by the time-consuming procedures already mentioned.The quinolin-8-01 method is the only one in which such inter- ference can be prevented by use of a complexing agent. (Beryllium ion interferes to a greater or lesser extent with the other methods.) This is the only sphere in which the proposed method compares un- favourably with other methods, as it is a solvent-extraction procedure.Such procedures are always more difficult to automate, on instruments such as the AutoAnalyzer, than aqueous methods. However, the procedure has been run successfully on the AutoAnalyzer using the solvent-displacement method of Carter.4 Owing to the ease with which the complex is extracted into chloroform it was found unnecessary to use a vibrating extraction coil.More recent work has shown that the use of Acidflex for the chloroform pumping tube simplifies the method and makes it relatively easy to automate. Analysis time. Calibration. In this respect the proposed method is far superior to the others. Detection limit. Levels of alkalinity found in natural waters have no effect. Interferences. Ease of automation.248 POLLUTION AND WATER CHEMISTRY Proc.AnaZyt. Div. Chem. SOC. References 1. Cheeseman, R. V., and Wilson, A. L., “Inter-Laboratory Testing of AnalyticalMethods-2. Iron and 2. Corbett, J. A., and Guerin, B. D., Analyst, 1966, 91, 490. 3. Knight, A. G., Pvoc. Soc. Wat. Treat. Exam., 1960, 9, 72. 4. Carter, J. M., and Nickless, G., Analyst, 1970, 95. 148. 6. Sandell, E. B., “Colorimetric Determination of Traces of Metals,” Third Edition, Interscience 6.Frink, C. R., and Peaslee, D. E., Analyst, 1968, 93, 469. 7. Middleton, K. R., Analyst, 1964, 89, 421. 8. Dagnall, R. M., West, T. S., and Young, P., Analyst, 1965, 90, 13. Aluminium,” Water Research Association Report TP73. Publishers, New York and London, 1959, p. 116. lon-exchange Systems and Their Analytical Control D. Kitchen ICI Agricultural Division, Billingham, Cleveland Steam is raised in boilers for a variety of purposes ranging from space heating and chemical processing to power generation by turbines.The required quality of the steam and the effici- ent operation of the boilers necessitates careful specification and control of the quality of the boiler feed-water. Table I lists some of the solutes found in raw water supplies that can adversely affect steam- raising operatons, together with their potential effects.TABLE I SOME SOLUTES FOUND IN RAW WATER SUPPLIES AND THE PROBLEMS CREATED Solute Potential problem Hardness salts Alkalinity Silica Dissolved gases Dissolved solids Formation of scales in heat-exchange equipment. Decomposition of hydrogen carbonates can give carbon dioxide in steam, Can volatilise in steam and re-deposit on turbine blades.Carbon dioxide and oxygen participate in corrosion processes. Can cause foaming and scaling in boilers, or be a source of corrosion. resulting in corrosion of condensate lines. In producing boiler feed-water the inorganic solutes in water supplies are usually removed, or reduced in concentration, by ion-exchange processes. Three main types of ion-exchange process are in common use, namely softening, dealkalisation and demineralisation, and their principal effects are shown in Table 11.TABLE I1 ION-EXCHANGE PROCESSES- Treatment Raw water Softening Dealkalisation - degassing - softening Demineralisation without mixed-bed Demineralisation with mixed-bed polishing unit polishing unit Total alkalinity, p.p.m. of CaCO, 100 100 10 1 (0.02 -WATER QUALITY ACHIEVED Equivalent Total mineral hardness, Sodium, acidity, p.p.m.of p.p.m. of p.p.m. of CaCO, CaCOs CaCO, 150 30 80 1 180 80 1 90 80 (0.1 <1 <1 (0.1 (0.02 <0.02 Silica, p.p.m. of SiO, 5 5 5 < 0.1 < 0.02 Softening Process This is the simplest form of ion-exchange process and is illustrated in Fig.1. The process uses a sulphonic acid resin in the sodium form. When the ion-exchange resin is exhausted there is a breakthough of calcium or magnesium ions in the product water. TheSeptember, 1975 POLLUTION AND WATER CHEMISTRY 249 resin bed is then broken up and cleaned by back-washing, before regenerating it with brine. This converts the resin back into the sodium form and, after rinsing, the unit is returned to service.Raw NaCl Raw water Waste injection water Treated Raw Effluent Effluent and water water to drain excess brine to drain NORMAL BACK- REGENER- RINSE FLOW WASH ATION Base exchange: strongly acidic resin in Na'form Softening cycle: 2NaR + Ca(HC03)z - CaR2 + 2NaHC03 (1) 2N3R + CaS04 - CaR2 + Na2S04 (2) Regeneration cycle: CaR2 + 2NaCI - 2NaR +CaC12 Fig.1. Softening. (3) The duration of the exhaustion cycle is determined by the hardness of the product water. This is conventionally measured by titration with EDTA. Such complexation reactions have been developed as the basis of on-line monitoring systems, as exemplified by the Testo- mat type of instrument. In this type of monitor an aliquot of the softened water is auto- matically mixed, at fixed time intervals, with an indicator solution.The indicator solutions are formulated to change colour at specified hardness concentrations, If the hardness con- centration of the water is less than that prescribed for a particular indicator, then the solution is green, and when the concentration is above that level it turns red. Such indicator solutions may contain a low concentration of magnesium with a stoicheio- metric equivalent of EDTA and some Solochrome Black screened with methyl orange.A calculated excess of EDTA is then added in order to complex a pre-set amount of hardness. When the hardness in the sample exceeds the excess of EDTA in the indicator, the calcium ions displace magnesium ions from their EDTA complex.The released magnesium then re- acts with the Solochrome Black system to produce the colour change. Dealkalisation Process Although softening processes will remove hardness salts from water, any dissolved hydrogen carbonate will be unaffected. Hydrogen carbonate ions may subsequently decompose in boilers to form potentially corrosive carbon dioxide and are, therefore, undesirable. An ion- exchange dealkalisation process, which will remove hydrogen carbonate, is available.This treatment process is usually designed as a dealkalisation unit and a degassing tower upstream of a softening unit (Fig. 2). This resin removes calcium and magnesium ions equivalent to the hydrogen carbonate in the water and replaces them with hydrogen ions. The carbon dioxide thus produced is removed in the degassing tower.The over-all process produces a softened water with a reduction in the dis- solved solids corresponding to the removal of carbon dioxide present as temporary hardness. The operation of the dealkalisation unit can usually be controlled by monitoring the pH of the product water. During the early part of the exhaustion cycle the pH of the product water is well below 4.5, but as the hydrogen carbonate starts to break through the pH rises.At some pre-determined pH value, based on alkalinity requirements, the run is terminated and the resin regenerated. Dealkalisation processes use a carboxylic acid resin in the hydrogen form.250 POLLUTION AND WATER CHEMISTRY Proc. Analyt. Div. Claem. Soc. Demineralisation Process Demineralisation processes, in their simplest design, use sequentially a sulphonic acid resin in the hydrogen form and a strong base resin in the hydroxide form (Fig.3). The cation- exchange unit exchanges any cations, other than hydrogen, for hydrogen and thus converts the anions into their equivalent free acids. Carbon dioxide is removed in the degassing tower and the mineral acids are removed in the anion-exchange unit.Raw water De-gassi ng tower Weakly Storage Strongly Treated acidic resin sump acidic resin water (H’ form) (Na’ form) Raw De-gassing water toyer I Strongly Storage Strongly Treated acidic resin sumD basic resin water (1) Carboxylic acid cation-exchange resin in H+ form: (H’ form) (OH- form) 2RH + Ca(HC03)Z -. RZCa + 2H2C03 ( 1) Cation-exchange resin in H+ form: RH + NaCl- RNa + HCI (Permanent hardness unaffected by this resin) (2) Anion-exchange resin in OH- form: (2) Sulphonic acid cation-exchange resin in Na’ form: ROH + HCI --+ RCI + H20 2RNa + CaS04 + R2Ca + Na~S04 (Removal of permanent Fig.3. Demineralisation. hardness) Fig. 2. Dealkalisation. This process can be controlled in an empirical manner by monitoring the conductivity of the product water.Conductivity measurements will not, however, detect silica in the product water, and as a non-specific measurement it is of limited usefulness. As sodium is likely to be the first of the cationic species to break through the cation-exchange resin, its concentration in the water is used to control the operation of this unit. The anion- exchange unit is usually controlled by monitoring the silica content of the product water.Sodium ion concentration is usually monitored with a sodium responsive (pNa) electrode. Sodium electrodes will respond to hydrogen ions and the pH of the sample is adjusted to a value in excess of 10 before measurement. pH adjustment is carried out with ammoniated air, but for low sodium concentrations it may be necessary to use triethanolamine for pH adjustment as the required amount of ammonia may exert a significant interference.Commercial continuous sodium monitors measure down to approximately 0.001 p.p.m. of sodium. The electrode output is displayed on a millivoltmeter and/or relayed to a remote recorder or alarm. “Silicometers,” for the control of the anion-exchange units, based on the colour measurement of the blue, reduced molybdosilicate complex, can be obtained commercially or constructed from AutoAnalyzer-type modules.Ammonium molybdate solution, sulphuric acid and a reducing solution (l-amino-2-naphthol-4-sulphonic acid) are added to the sample and the blue colour developed. In the EIL, Model 58F, silica analyser, for example, the total analysis cycle takes 12 min and consists of two sequences. The first sequence measures a “blank” obtained by adding the ammonium molybdate, sulphuric acid and reducing solution to the mixing vessel and then diluting them with the sample.This measures the silica in the re- agents. The second sequence mixes the reactants in the accustomed order of sample, am- monium molybdate, sulphuric acid and reducing agent in order to measure the silica content of sample plus reagents.Measurements down to approximately 0.001 p.p.m. of silica can be made with this type of system. Conclusion Modern ion-exchange plants are expensive installations producing water to close specifica-September, 1975 POLLUTION AND WATER CHEMISTRY 25 1 tions. The use of sensitive, on-line methods of analysis and control is imperative.The choice of analytical parameters is dictated by the type of process and the end use of the water. Interferences in the Electroanalytical Determination of Copper and Lead in Water and Waste Water D. Barnes,* B. G. Cooksey,t B. Metterst and C. Metters" University of Strathclyde, Cathedral Street, Glasgow, G1 1 X L Heavy metals can exist in aqueous solutions in a variety of forms: soluble, precipitated, com- plexed and adsorbed on to solid materials.The form of the metals in the solution influences the toxicity of the metals, the effect of any treatment process upon the removal of the metal and the determination of the metal concentration. Electroanalytical techniques are particularly useful as they are sensitive, non-destructive methods that are capable of giving data about the form of the species in the solution.Anodic stripping voltammetry has been used to determine free and complexed amounts of toxic metals in natural waters and effl~ents,l-~ although there is often little experimental justification that complexation is occurring in real sample^.^ The interactions between the metals and complex- forming ligand~,l-~ suspended solids5s6 and precipitate-forming anions have been reported but the relative contribution of these processes is less certain.Samples of final effluent from an activated-sludge sewage works and of water from Loch Lomond were analysed by d.c. polarography, anodic stripping voltammetry, particle size analysis and atomic-absorption spectrometry.Full experimental details can be found else- where.' s 8 Analysis by d.c. polarography of solutions prepared by standard addition of lead to sewage- works effluents at concentrations in the range 10-5-10-4 M (1-20 p.p.m.) showed that all of the lead did not stay in a free soluble form at pH 7. At concentrations less than 1 x M, less than 10 per cent. of the added lead was detectable as freely dissolved in the solution; similar results were observed for copper.In more acidic solutions, straight-line calibration graphs were obtained. Complex formation can be discounted as very stable comple~es*~~ would be necessary (log,, K > 50), which have not been reported. However, heavy metals form precipitates with common anions, notably carbonates and phosphate.Solutions that contained greater than 1.0 p.p.m. of lead and 10 p.p.m. of phosphate were observed to contain significant numbers of particles of diameter 0-4-0.7 x 10-6 m. Calibration graphs for lead in pure solutions of phos- phate and carbonate confirmed that these anions can cause interference in the determination of copper and lead (Fig. 1). At lower concentrations of lead, which were studied by means of anodic stripping voltam- metry, curved calibration graphs were also obtained for neutral solutions of Loch Lomond water.Again, on raising the acidity, linear calibration graphs through the origin were obtained. Complex formation is again unlikely and precipitation can be eliminated as the solubility product of the compounds are not exceeded at the relevant concentrations.1° Several solutions of trace amounts of metal, which contained a variety of solids, were analysed at pH 4 and pH 7 after each solution had been centrifuged (Table I).The results indicate that these types of material are capable of adsorbing lead and that the effect is pH dependent. Calibration graphs for centrifuged samples, which were shown to contain fewer particles than uncentrifuged samples, were more linear (Fig.2). The combined particle size analysis, centrifugation and suspended solids addition experi- ments indicate that the adsorption of low concentrations of metal (p.p.b.) on to suspended solids can occur and that it produces a significant effect upon the determination of metals in waters. At higher concentrations (p.p.m.) the adsorption sites on the solid materials are saturated, and the effect is unlikely to be as significant.These results indicate that the chemical form and therefore the free soluble-ion concentration of metals in natural and waste waters is not a function of a single variable but iS controlled by * Department of Civil Engineering. t Department of Pure and Applied Chemistry.252 POLLUTION AND WATER CHEMISTRY Proc.AnaZyt. Div. Chem. SOC. TABLE I ADSORPTION OF LEAD (0.08 P.P.M.) ON TO SUSPENDED SOLIDS Amount of lead remaining in solution after centrifuging, p.p.mA Solid added PH 7 PH 4 Sand Silica gel Alumina Bentonite 0.016 0.070 0.007 0.065 0.015 0-078 0.020 0*09* * Original solid probably contained trace amounts of lead. the following factors: pH, the concentration of the metal, the amount of organic material and of suspended solids, and also the anion concentration and type.Precipitation is likely in samples that contain significant concentrations of anions that are capable of forming insoluble precipitates, e.g., sewage works final effluents from the breakdown of detergents. While adsorption of very small amounts of metal on to suspended materials caused the most signific- ant interference in the determination of metals in Loch Lomond water, pH adjustment eliminates these interferences but masks information about the state of the metals in the solution.0 4 8 12 16 20 Lead concentration/M X lo5 Fig. 1. Calibration graphs for lead in phosphate and carbonate solutions by d.c.polarography. Solutions : A, 5 p.p.m. carbonate, buffered at pH 7.0; B, 3p.p.m. phosphate, buffered a t pH 7.0; and C, with or without phosphate and carbonate, buffered a t pH 5.0. I 0 4 8 12 16 20 Lead concentration/M X 1 O7 Fig. 2. Effect of centrifuging Loch Lomond water prior to standard addition of lead by anodic stripping voltammetry. Solutions: A, Loch Lomond water, pH 7.0; B.Loch Lomond water, pH 7.0, centrifuged prior to addition of lead; and C, distilled water, pH 7.0. or Loch Lomond water, pH 4.0. While it is possible to check the origin of many types of interference, it is unclear whether conclusions based upon particular samples can be generally applicable. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. References Matson, W. R., and Barsdate, R. J ., “Proceedings on Radioecological Concentration Processes,” Matton, W.R., Allen, H. E. and Rekahen, P., Am. Chem. SOC. Div. Wat. Air Waste Chem. Gen. Pap., Lewin, V. H., and Rowell, M. J., Efl. Wat. Treat. I., 1973, 13, 273. Chau, Y. K., and Lum Shue Chan, K., Waf. Res., 1974, 8, 383. Gardiner, J., Waf. Res., 1974, 8, 23. Rao Gadde, R., and Laitinen, M. A., Environ. Lett., 1973, 4, 223. Metters, B., “Application of Anodic Stripping Voltammetry to the Determination of Lead,” Ph.D.Barnes, D., Cooksey. B. G., Metters, B., and Metters, C., Proc. SOC. Wut. Treat. Exam., in the press. Heyrovskg, J ., and Kbta, J ., “Principles of Polarography,” Czechoslovak Academy of Sciences, Ringbom, A., “Complexation in Analytical Chemistry,” Interscience Publishers, New York, 1963.Stockholm, 1966, p. 711. 1969, p. 164. Thesis, University of Strathclyde, 1974. Prague, 1965.September, 1975 POLLUTION AND WATER CHEMISTRY 253 Gel Filtration as a Method for Studying the Brown Organic Acids in Raw Water Supplied to Arnfield Treatment Plant M. G. Snow North West Water Authority, Eastern Division, Denton Laboratory, Manchester Road, Denton, M34 3Q J One of the waters utilised by the Manchester Water Supply Unit is from a peaty moorland area.The water is coloured from contact with the peat and contains iron and manganese in excess of the recommended levels for potable waters. This water is treated by coagulation with chlorinated copperas followed by sedimentation, pH correction and rapid gravity filtra- tion. At certain times, treatment difficulties were experienced when the treated water was clear and colourless but still contained excessive amounts of iron.The “solubilisation” of iron by the organic acids in water is well known, and a possible explanation of the problem was the presence of these acids in the raw water and that part of them was not being removed by treat- ment. These remaining acids did not impart a large amount of colour to the treated water but could hold iron in solution.The method of study comprised initial concentration of the coloured organic acids by anion exchange on a column of the macroporous resin De-Acidite K. After concentration, the acids were fractionated by gel filtration on a column of Sephadex G-25. The elution volume of a substance fractionated by this method is dependent on its molecular size, but there are occasions when this is not the only effect as interaction of certain solutes with the gel matrix has been observed.There are two main categories of interaction that effect the coloured organic acids in water. Firstly, there are a small number of residual carboxylic acid groups present on the gel matrix and in an eluting solution of low ionic strength the gel will exhibit ion-exchange properties and the coloured organic acids are eluted earlier than would be expected from molecular size considerations.The second effect is the reversible adsorption of aromatic and heterocyclic (w-electron rich) compounds to the gel matrix, which causes them to be eluted later than expected. The exclusion effect can be eliminated by the addition of a small amount of electrolyte to the eluting solution but this also has the effect of increasing the ad- sorption of the coloured organic acids to the gel matrix, that is, adsorption increases with in- creasing ionic strength, eluting solution or sample.Unfortunately, it is not possible to elimin- ate both effects simultaneously. In addition, the pH of the sample or eluting solution in- fluences the fractionation.In alkaline medium, adsorption is decreased owing to an increase in exclusion of the more highly ionised acids by the residual carboxyl groups on the gel matrix and in acidic solution adsorption is increased owing to decreased exclusion. The fractionation of the coloured organic acids on Sephadex is therefore very dependent upon the elution condi- tions, in particular the pH and ionic strength of the sample and/or eluting solution.In this series of experiments, the pH and ionic strength of the concentrate samples were made con- stant and distilled water was used as the eluting solution. In this way, using constant elution conditions, elution patterns for different samples are comparable.The elution patterns obtained over a 17-month period showed that there are five main identifiable fractions, one of which is reversibly adsorbed on the gel matrix and another is totally excluded from the gel. The make-up of the fractions of the coloured organic acids in the water under consideration is very complex and although predominantly the same fractions are observed in all samples, their proportions differ from sample to sample.Attempts were made to correlate the elution patterns obtained with season, rainfall and raw water quality, in particular the colour of the raw water, but no such correlations were observed. Correlations of this type oversimplify the picture as the period of time over which the samples were taken is short and a longer period of study is required, but eventual correlation with a combination of factors might be anticipated.The stability of the coloured acids is also of interest. On storage at 5 O C , a progressive change in the make-up of the organic acids was observed. There was loss of organic material associated with precipitation in the concentrate but overall there was an alteration in the pro- portion of the fractions, the excluded fraction becoming more predominant at the expense of the middle fractions and the adsorbed fraction remaining more or less constant.In addition, there was a loss of iron on storage, again associated with the formation of a precipitate in the In addition, two samples have extra peaks.254 POLLUTION AND WATER CHEMISTRY Proc. AnaZyt. Div.Chem. SOC. concentrate, and after storage for 5 months no iron was associated with the middle fractions as observed immediately after concentration, all of the remaining iron being associated with the excluded fraction. Only with one sample was over-all removal observed and on all other occasions there was preferential removal of fractions, three samples showing preferential removal of the excluded fraction.Comparison of the irm content of the raw water and that of the concentrate showed that the iron recovery was less than 10 per cent. on concentration. The resulting low iron con- centrations in the eluate from the column mean that conclusions from iron experiments are only tentative. It would seem, however, that iron is not necessarily associated with any one fraction but the whole range, and for a given sample iron is associated with some fractions in preference to others.In addition, iron peaks do not necessarily coincide with organic peaks, indicating hidden organic fractions. Gel filtration on Sephadex can be used to characterise the brown organic acids in water and to study the effects of treatment and association with iron. Fractionation, however, does not necessarily occur according to molecular size and relative molecular masses cannot be assigned to fractions.On five occasions, the effect of treatment on the organic acids was determined. Total Oxygen Demand B. D. Ravenscroft Northumbrian Water Authority, Eldon House, Regent Centre, Gosfoorth, Newcastle upon Tyne, NE3 3PX The deficiencies and delays inherent in the classical oxygen demand measurements on waste waters (biochemical oxygen demand, BOD ; chemical oxygen demand, COD ; permanganate value, PV) have been responsible for the development of instrumental methods for the rapid (2-5 min) determination of non-specific organic, water-borne pollutants.Total carbon - total organic carbon (TC - TOC) and total oxygen demand (TOD) techniques are the outcome of this effort.The basic principle of TOD instrumentation is that an aliquot of sample is burned with the aid of a catalyst at high temperature (900 "C) in a stream of carrier gas (nitrogen) containing a small and constant proportion of oxygen. The residual oxygen, after this combustion process, is monitored, the depletion in the oxygen level in the carrier gas being related to the TOD of the sample.The detection system for the residual oxygen is different on the only two labora- tory instruments available in the UK today: the Philips PW9625 employs a solid electrolyte [zirconium(IV) oxide] detection system whereas the Ionic 225 analyser employs a platinum - lead fuel cell. The performance characteristics of the latter instrument are such that precision is much better in the middle and upper working ranges (0400 or 500 mg 1-1 and 0-1000 mg 1-1 TOD) than in the lowest range (0-50 or 100 mg 1-1 TOD). It has been demonstrated that the instrument will accept samples that contain high levels of dissolved solids and also suspended solids, provided that in the latter case the samples are pre-treated so as to reduce the size of the solids to less than 200 pm.The chemistry of TOD determinations is that at 900 "C organically bound carbon, nitrogen and hydrogen are oxidised to carbon dioxide, nitric oxide and water, respectively, representing greater oxidation efficiency than that achieved in the COD test. Ammoniacal nitrogen is similarly oxidised (cf., COD) and thus free and saline ammonia present in samples contribute to the observed TOD value; each milligram of ammonia per litre should inflate the TOD value by 2.35 mg 1-1 of oxygen.This relationship has been shown to hold by the addition of known amounts of ammonia to standard TOD solutions. Measured TOD values represent the excess oxygen demand above that satisfied by the oxygen that will be dissolved in the sample under normal conditions.Hence dissolved oxygen is an interferent in TOD determinations and must either be measured and corrected for, or eliminated prior to presentation of the sample. Nitrate has been shown to break down under TOD conditions to give off oxygen; each milligram of nitrate per litre should depress the observed TOD value by 0.4 mg 1-1 of oxygen.September, 1975 EDUCATIONAL TECHNOLOGY AND ANALYTICAL CHEMISTRY 255 Additions of nitrate to standard TOD solutions show that this relationship is closely approxi- mated.Possible interferences from other anions (Cl-, C032-, PO,3-, SO,2-) are negligible. Heavy-metal ions have been known to cause catalyst poisoning. Correlations between TOD and COD have been shown to be dependent upon the composition of the waste water being examined.For those wastes that are essentially carbonaceous in nature, the ratio TOD : COD-1. Mixed wastes that contain nitrogenous materials and/or ammonia (e.g., sewage) frequently show TOD : COD ratios above unity, whereas those which contain high levels of nitrate tend to show T0D:COD ratios below unity. Correlations between TOD (or COD) and BOD are similarly dependent upon composition, and also on the degree of biological treatment that the waste water has received. TOD : BOD and COD : BOD ratios have been shown to increase as a result of biological treatment. General TOD to BOD correlations cannot be expected to be precise. Results on 161 samples of 50 sewage effluents taken over a period of 6 months showed that 90 per cent. lie between TOD : BOD ratios of 1 and 5. Applications of TOD TOD measurements have been made in the range 0-25 mg 1-1 on “clean” river waters by taking stringent precautions to exclude dissolved oxygen as far as possible, TOD values of about 5mg1-1 being reliably measured. Operation in lower ranges is precluded by the capabilities of current instrumentation, and interference by trace amounts of dissolved oxygen. Measurements at the level below 1 mg 1-1 is an area where TOC is far more applicable than TOD. By slight modification of the operating conditions of the Ionic 225 instrument, it has been shown to be possible to carry out continuous determinations on sea water samples for periods of up to 7 days. Industrial applications have included on-line operation in industrial sewers in order to protect biological treatment processes from dangerous high-level “spills” ; detection of losses from production units in which expensive products are made; and industrial final effluent monitoring, particularly in relation to those efluents that exhibit toxic or bacteriostatic properties in the BOD test. Other laboratory applications include the determination of BOD dilutions from TOD measurements, and as an alternative to COD for trade-effluent control purposes.

ISSN:0306-1396    

DOI:10.1039/AD9751200246

出版商:RSC    

年代:1975

数据来源: RSC

摘要:

September, 1975 EDUCATIONAL TECHNOLOGY AND ANALYTICAL CHEMISTRY 255 Educational Technology in the Service of Analytical Chemistry The following is a summary of one of the papers presented at a Joint Meeting of the Education and Training Group with the Educational Techniques Subject Group of the CS Education Division held on March 19th and reported in the April issue of Proceedings (p. 108). The Use of Television and Film in Teaching Analytical Chemistry W.J. Williams School of Chemistry, University of Bath, Bath, BA2 7A Y Of the many educational aids available, little if anything has been reported on the use of tele- vision in teaching analytical chemistry. The present account sumarises our experience of this technique at Bath over the past 7 or 8 years. Rather than use “live” television, we have preferred to use it in the form of videotapes, which consist of magnetic tapes on which a composite video and audio signal is recorded.It can be erased and the tape re-used if necessary. In the first instance, the technique was used for the simple reason that it was already avail- able at the University, as was film. Subsequent experience has indicated that videotape has several advantages over alternative aids and these advantages are discussed below.Our256 EDUCATIONAL TECHNOLOGY AND ANALYTICAL CHEMISTRY PYOC. Analyt. Div. Chem. SOC. application of the technique was directed to a problem not unfamiliar to those in educational establishments, government laboratories and industry concerned with teaching sound analyti- cal technique at the post A-level stage.There is little doubt that schools give scant attention to this aspect, preferring to emphasise the explanation of chemical reactions in terms of theor- etical concepts. One would not dispute the importance of this approach, but on the other hand chemistry, in common with the physical and biological sciences, is essentially an empirical subject with a strong dependence on sound experimental work.Such work, if it is to be signi- ficant, must be conceived and executed in such a way that unambiguous conclusions can be drawn from its results. In relation to teaching analytical chemistry, imparting good tech- nique involves covering a wide range of operations and situations, all of which affect the over-all result.It should be emphasised that our use of videotape is essentially as an aid to and not as a substitute for personal teaching. Tapes on preparing a standard solution, titrimetric analysis, etc., are shown early in the first-year practical course, after which they are available in the library for viewing on videotape recorders, which form part of the standard library facilities. Technique The videotape is made by using a TV camera and videotape recorder in much the same way that a tape recorder produces an audio record.The tape itself, in the form of a video cart- ridge, consists of an enclosed reel. Tape threading is automatic when the cartridge is placed in the appropriate machine, the tape being wound on to another spool in the body of the recorder. The absence of a loose end is a particular advantage. In general, two or more cameras would be used with editing being carried out electronically by switching from one to the other.Editing is never made by physically cutting the tape as in film. Captions are introduced in the same way. The programmes already made are relatively short, each lasting from 10 to 15 min. Advantages Apart from the general benefits derived from using visual aids, for example economy in time, ability to repeat and ability to show close-up in detail, we find that videotape has the following particular advantages : (a) The equipment is relatively simple to operate and requires no assistance.(b) The monitor has sufficient illumination not to require darkening the room or laboratory. (Note: the monitor displays the picture from the TV camera or video-recorder. It is not identical with a TV receiver in that it cannot pick up broadcast channels, but both functions can be combined in a monitor - receiver.) (c) No clear run of space is required in front of the screen as in film.In our work, the technique is used in a large rectangular laboratory. Two monitors arranged mutually at right-angles enable the programme to be seen in most parts of the laboratory.(d) In preparing a videotape programme, several versions can be made and the best retained. Unwanted material is easily erased and the tape re-used. Disadvantages Although the advantages far outweigh any disadvantages, one should be aware of the latter : (a) Videotapes are not interchangeable on all videotape recorders.We use 1-in I.V.C. standard tape for master copies. These are dubbed on to &-in tape for use on Hitachi Shibaden recorders. They are incompatible with most Sony recorders and several others. Problems arise when tapes are sent to establishments that use a different system. (b) The whole programme must be recorded in one uninterrupted sequence. It is not possible, as in film, to join up a number of small sequences by physically sticking them together.(c) Video recording is less mobile than film and tends to be carried out in a studio. This is often inconvenient. (a) Although videotapes can present information quickly, a large investment in time is required in their preparation. A 15-min tape requires about 3 days of time, involvingSeptember, 1975 DISTINGUISHED SERVICE AWARD 257 thinking out the sequence, preparing the script and :captions, trying out the practical work and preliminary trial runs.The Script The script itself contains not only the spoken words but also the complete sequence of camera work, captions, close-ups, etc. It is an essential item if five or six people are to know their own part in the complete sequence, which might be complex in parts.A related point is the pro- fessional contribution that the programme producer can make. Perhaps scientists have in the past been too content to use do-it-yourself methods rather than seek the advice necessary to produce a more professional product. Students now see high levels of professionalism on tele- vision.In our experience, the Educational Services Unit at the University is extremely helpful in this respect, and one result is that the analytical chemistry series is introduced to the stirring sounds of Beethoven's Sonatina in C major. Should we be content to fall well below this level? One has to confess that it is all the better for this. costs It has been pointed out that facilities were available before the analytical series was con- templated.Current prices of the essential items of equipment (1974) would be camera E200, videotape recorder L400, monitor El00 and videotapes E10-15 per hour of play. In addition, portable lighting is generally required. Scope The present discussion has been restricted to one aspect of teaching analytical chemistry, namely practical technique. Without doubt there is considerable scope for applying it to other topics within the discipline. As an indication of what can be done, one can cite use of the technique in other areas. In the School of Engineering at Bath, complete packaged problems are available on videotape. These include a statement of the problem, critical discussion on how it may be tackled, location of relevant literature and other advice such as data handling. It may be that a similar approach could well be applied to teaching analytical chemistry at all levels, including MSc taught courses.

ISSN:0306-1396    

DOI:10.1039/AD9751200255

出版商:RSC    

年代:1975

数据来源: RSC

摘要:

September, 1975 DISTINGUISHED SERVICE AWARD 257 Analytical Division Distinguished Service Award The Council of the Analytical Division has shall be made in writing, with supporting decided to institute a Distinguished Service evidence, to the President of the Award, the rules for which are as follows- Analytical Division. 1. The aim of the Award is to recognise exceptional service over a period of years to the Analytical Division of the Chemical Society (including that to the Society for Analytical Chemistry).2. The Award shall normally be in the form of an illuminated address, which may be accompanied by such additional recogni- tion as Council of the Division shall agree. 3. Nominations for the Award will be invited annually from members of Council of the Division, and may be received from any member of the Division.They 4. Nominations shall be considered by the Honours Committee of the Analytical Division, which shall recommend to Council of the Division (a), to whom an award should be made, (b), the nature of the award, or (c), that no award should be made. 5. The Award shall be made by the Council of the Analytical Division, which must approve any alteration of these Rules. Nominations for the Award should be sent to the President of the Analytical Division before September 30th, 1975.

ISSN:0306-1396    

DOI:10.1039/AD9751200257

出版商:RSC    

年代:1975

数据来源: RSC

摘要:

258 CONFERENCES AND MEETINGS PYOC. AnaZyt. Div. Chem. Soc. Self-employed Public Analysts: Increased Fees The Price Commission, under paragraph 44 of the Price Code, have consulted the National Joint Council for Local Authorities’ Pro- fessional, Technical and Clerical Services about increases in allowable costs for certain services supplied by part-time Public Analysts employed by local authorities.Having taken into account information supplied by the Council, the Com- mission have calculated average allowable cost increases for these services. The average allowable cost increases deter- mined by the Commission during the period July lst, 1974, to July Ist, 1975, are as follows: Per testlf; r 7 A B C D A Increase in: Allowable labour costs (after productivity deduction under para.34 of the Code) Materials, components, consumables, as defined in para. 28 (b) (ii) of the Code Fuel and power Rent and rates Bought-in services Total allowable costs Total costs at July lst, 1974 Total costs at July lst, 1975 0.379 0.139 0.037 0.048 0.005 0.662 2.780 3.495 0-840 0.307 0.081 0-107 0.010 1-465 6.159 7.742 1.258 0.462 0.104 0.161 0.015 2.180 9.186 11.543 1.496 0.548 0.124 0.192 0.018 2.591 10.913 13.715 A : Milk, without preliminary testing. B : Milk, with preliminary testing; other food and drugs.C : Fertilisers and feedingstuffs-samples under the Fertilisers and Feedingstuffs Act, 1926. D : Pesticide residues in feedingstuffs-local government scheme. The increased prices which the Price Com- mission regard as justified with effect from July lst, 1975, on the basis of these average allowable cost increases, are as follows (previous fees in parentheses) : A : Milk samples, without preliminary testing . . i4-59 (i3.77) B: Milk samples, with preliminary testing ; other food and drugs LlO-22 (L8-39) C : Fertilisers and feeding- D : Testing for pesticide stuffs samples L15-21 (L12.49) residues in feeding- stuffs LlS.09 (i14.86)

ISSN:0306-1396    

DOI:10.1039/AD975120258a

出版商:RSC    

年代:1975

数据来源: RSC

摘要:

September, 1975 PUBLICATIONS RECEIVED 259 Publications Received Technique of Electroorganic Synthesis. Edited by Norman L. Weinberg. Techniques of Chemistry. Volume V , Part II. Pp. xiv + 1070. New York, London, Sydney and Toronto: John Wiley & Sons. 1975. Price k22. Analysis of Water. J. Rodier. Pp. xviii + 926. New York, Sydney, London, Tokyo, Mexico City and Toronto: John Wiley & Sons.1975. Price f133.260 CHEMICAL SOCIETY LIBRARY Proc. Analyt. Div. Chem. SOC. British Pharmacopoeia 1973. Addendum 1975. Pp. xx + 42 + Appendices A1 to A20. London : Her Majesty’s Stationery Office. 1975. Price k5. Systematic Physical Chemistry. L. C. Roselaar. Pp. xii + 251. London: John Murray. 1975. Price k2.95. Colloque International sur l’halyse par Activation de Tr&s Faibles Quantitds d’Elements.Au C.E.N. Saclay, France, 24th Octobre, 1972. Reprinted from the Journal of Radioanalytical Chemistry. Pp. xii + 854. Budapest: Akadbmiai Kiad6. 1972. Price 436.10. Manuel Pratique de Chromatographie en Phase Liquide. R. Rosset, M. Caude and A. Jardy. Pp. xiv + 280. Orsay: Varian S.A. 1975. Price F85.60. European Spectroscopy News. Executive Editor P.M. Williams. Volume 1, No. 1, July, 1975. Pp. 32. London: Heyden & Son Limited. 1975. Free of charge to all practising spectroscopists in Europe. A New Journal. Calculation of Physical Properties of Petroleum Products from Gas Chromato- graphic Analyses. A Symposium sponsored by ASTM Committee D-2 on Petroleum Products and Lubricants. Dallas, Texas, December 6, 1973.ASTM Special Technical Publication 577. Pp. viii + 107. Philadelphia: American Society for Testing and Materials. 1975. Price $10.75. Stripping Voltammetry in Chemical Analy- sis. Kh. 2. Brainina. Translated from Russian by P. Shelnitz. Pp. xii + 222. New York and Toronto: John Wiley & Sons; Jerusalem and London : Israel Program for Scientific Trans- lations. 1974. Price 49.35.The Analysis of Detergents and Detergent Products. G. F. Longman. Pp. xviii + 626. London, New York, Sydney and Toronto: John Wiley & Sons. 1975. Price 411.50. Optical Methods of Radio-Frequency Spec- troscopy. Ion I. Agarbiceanu and Ion M. Popescu. Trans- lated from Romanian by Mircea Cristu. Pp. 310. London: Adam Hilger Ltd. 1975. Price L15. Liquid Column Chromatography.A Survey of Modern Techniques and Applications. Edited by 2. Deyl, K. Macek and J. JanAk. Journal of Chromatography Library, Volume 3. Pp. xxii + 1175. Amsterdam, Oxford and New York : Elsevier Scientific Publishing Company. 1975. Price Dfl290; $120.95. Materials in Chemical Perspective. K. L. Watson. Pp. viii + 123. London: Stanley Thornes (Publishers) Ltd. 1975. Price L1.96 (softback) ; A4.40 (hardback). An Introduction to Thermogravimetry. Second Edition. C. J. Keattch and D. Dollimore. Pp. xii + 164. London, New York and Rheine: Heyden & Son. 1975. Price 44; $10; DM27-50. Fundamentals of Inorganic Chemistry. A Programmed Introduction. Edited by B. J. Aylett and D. E. Billing. Pp. xii + 96. London, New York and Rheine: Heyden & Son. 1975. Price L.2; $5; DM12.

ISSN:0306-1396    

DOI:10.1039/AD9751200259

出版商:RSC    

年代:1975

数据来源: RSC

摘要:

260 CHEMICAL SOCIETY LIBRARY Proc. Analyt. Div. Chem. SOC. Chemical Society Library The following publications of analytical interest have been added to the Library since the last list appeared in Proceedings (1975, 12, 238). Elucidation of Organic Structures by Physical and Chemical Methods. Part 1. Second Edition. Edited by K. W. Bentley and G. W. Kirby. Wiley-Interscience. 1972. Handbook of Reactive Chemical Hazards : an Indexed Guide to Published Data.L. Bretherick. Butterworths. 1975. Methods of Chemical Analysis of Iron and Steel. British Steel Corporation. 1974. Handbook of Process Stream Analysis. K. J . Clevett. Ellis Horwood. 1973. A Safety Handbook for Science Teachers. K. Everett and E. W. Jenkins. Murray. 1973. Analytical Profiles of Drug Substances.Volume 4. Edited by K. Florey. Academic Press, 1975. Automatic Chemical Analysis. J . K. Foreman and P. B. Stockwell. Ellis Honvood. 1975.September, 1975 ANALYTICAL DIVISION DIARY 261 Essential Aspects of Mass Spectrometry. A. Frigerio. Distributed by Halsted Press. 1974. Gas Chromatography of Coating Materials. J. K. Haken. Dekker. 1974. The Interpretation of Infrared Spectra: a Programmed Introduction.R. R. Hill and D. A. E. Rendell. Heyden. 1975. Recent Analytical Developments in the Petroleum Industry. Proceedings of the Institute of Petroleum Symposium held at the Zoological Society of London. Edited by D. R. Hodges. Applied Science for the Institute of Petroleum. 1974. An Introduction to Thermogravimetry. Second Edition. C. J. Keattch and D.Dollimore. Heyden. 1975. Topics in Carbon-13 NMR Spectroscopy. Volume 1. Edited by G. C. Levy. Wiley. 1974. Separation Methods in Chemical Analysis. J. M. Miller. Wiley-Interscience. 1975. Electroanalytical Chemistry. Edited by H. W. Nurnberg. Wiley. 1974. Handbook of Moisture Determination and Control. Principles, Techniques, Applica- tions. Volumes 1, 2 and 3. A. Pande. Dekker. 1974. Dangerous Properties of Industrial Materials. Fourth Edition. N. I. Sax. Van Nostrand Reinhold. 1975. Wilson and Wilson’s Comprehensive Ana- lytical Chemistry. Volume 4. Edited by G. Svehla. Elsevier. 1975. Atomic Fluorescence Spectroscopy. Trans- lated from Czechoslovakian. V. Sychra, V. Svoboda and I. Rubeska. Van Nostrand Reinhold. 1975. The Identification of Functional Groups in Organophosphorus Compounds. L. C. Thomas. Academic Press. 1974.

ISSN:0306-1396    

DOI:10.1039/AD9751200260

出版商:RSC    

年代:1975

数据来源: RSC