摘要:

Proceedingsof the Analytical Division ofThe Chemical SocietyCONTENTS325 Summaries of Papers325 'Some New Approaches to Spectro-chemical Analysis'326 'Research and Development Topicsin Analytical Chemistry'342 'Detection Limits and Trace Analysis'344 'Single-particle Characteristics'348 Correspondence349349 Fourth SAC Conference349 Course349 Publications Received350 Analytical Division DiaryNominations for the AD CouncilVolume 13 No 1 1 Pages 325-350 November 197PADSDZ 13(11)325-350(1976)ISSN 0306-1 396November 1976PROCEEDINGSOF THEANALYTICAL DIVISION OF THE CHEMICAL SOCIETYOfficers of the Analytical Divisionof the Chemical SocietyPresidentD. W. WilsonHon. SecretaryP. G. W. CobbSecretaryMiss P. E. HutchinsonHon. Treasurer Hon.Assistant SecretariesJ. K. Foreman D. I. Coomber, O.B.E.; D. C. M. Squirrel1Editor, 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.0 The Chemical Society 1976Annual Reports on AnalyticalAtomic SpectroscopyVOLUME 5,1975This comprehensive and critical report of developments in analytical atomicspectroscopy has been compiled from over 1550 reports received fromworld-wide correspondents who are internationally recognised authorities inthe field and who constitute the Editorial Board. In addition to surveyingdevelopments throughout the world published in national or internationaljournals, a particular aim has been to include less widely accessible reportsfrom local, national and international symposia and conferences concernedwith atomic spectroscopy.Paperbound 276pp 8$”x6” f15 (CS Members f9)(Still available: Vols. 2-4 covering 1972 to 1974)Obtainable from : The Publications Sales Officer, The ChemicalSociety, Blackhorse Road, Letchworth, Herts., SG6 1 H

ISSN:0306-1396    

DOI:10.1039/AD97613FX038

出版商:RSC    

年代:1976

数据来源: RSC

摘要:

Analytical Division DiaryNOVEMBERTuesday, 23rd, 6.15 p.m. : NottinghamMidlands Region : Annual General Meeting,followed by a Joint Meeting with theBiological Methods Group.“Alternatives to liadioimmunoassay,” byJ . Bridges.Lecture Theatre, The Boots Co. Ltd., Penny-foot Street, Nottingham.Thursday, 25th, 2.15 p.m.: CambridgeEast Anglia Region : Annual General Meeting,followed by a meeting on “Analysis forPlant Breeding.”“Quality Components of Some AgriculturalCrops,” by E. T. Whitmore.“Analytical Techniques in Wheat Assess-ment,” by Miss E. M. Nicholas.“Quality Assessment in Sugar Beet,” byW. Woodwark.Research and Technology Centre, SpillersLtd., Station Road, Cambridge.Tuesday, 30th, 2.15 p.m.: LondonA tomic Spectroscopy and Pavticle Size AnalysisGroups : Annual General Meetings, followedby a Joint Meeting on “Sampling.”“The Sampling of Heterogeneous BulkSolids,” by R.Smith.“Powder Sampling in the Laboratory,” byM. W. G. Burt.“Sampling, Grinding and Particle Size Effectsin Analysis,” by A. E. Smith.“Atmospheric Sampling in the Urban En-vironment,” by D. J. Ball.Lecture Theatre, Geological Society, Burling-ton House, Piccadilly, London, W. 1.Tuesday, 30th, 10.30 a.m. : GrangemouthChvomatography and Electvophovesis Gvoup :Annual General Meeting and Joint Meetingwith the Scottish Region and the Chroma-tography Discussion Group on “Gas Chroma-tography in the Oil Industry.”“Measuring Men’s Exposure to PetroleumVapours During Processing and Trans-portation,]’ by D.T. Coker.“The Use of Molecular Sieves for Analysis ofPetroleum, I’ by N. G. McTaggart .“Quantitative Analysis of Petroleum Pro-ducts by Gas Chromatography,” by A. G.Butlin.“A Baseline Study of Hydrocarbons in SeaWater,” by P. John.“Some Aspects of Gas Chromatography inPetroleum Prospecting,” by A. G. Douglas.BP Refinery, Grangemouth.DECEMBERWednesday, lst, 10.30 a.m. : LondonSpecial Techniques Gvoup : Annual GeneralMeeting and meeting on “Different Sourcesfor Mass Spectrometry.”Introductory Lecture by M. Barber,“Ion Microprobe Sources,” by P. Turner.“Field Desorption Sources,” by D. Millington.“Spark Sources,” by Dr. Mapper.“Plasma Source Mass Analysers,” by J. S.Lecture Theatre A, Imperial College, SouthHobbs.Kensington, London, S.W.7.Thursday, 2nd, 2 p.m.: LondonEducation and Tvaining Group : AnnualGeneral Meeting and Workshop on “Experi-ments in Analytical Chemistry.]’Polytechnic of North London, Lecture Room11/3, Tower Block, Holloway, London, N.7.Tuesday, 7th, 6.30 p.m.: EasthamNovth West Region, jointly with the Carlett“The Analysis of Food Flavours,” by M.Carlett Park College of Technology, Eastham,Park Chemical Society.Howlett .Wirral.Wednesday, 8th, 10.30 a.m.: LondonA fialytical Division, organisecl by the Auto-matic Methods and ElectroanalyticalGroups, on “The Use of Enzymes inAnalytical Chemistry. I ’ The meeting willalso include the Annual Gcneral Meetings ofboth Groups.“Enzyme Immunoassay,” by Professor S. A.Barker.“Enzyme Electrodes,” by Professor G. G.Guilbault .“Immobilised Enzymes,” by W. E. Hornby.“Microcalorimetric Measurements,” by A. E.Beezer.“Some Aspects on the Utilisation of a Peni-cillin Sensitive Enzyme Electrode inFermentation Control,” by S. 0. Enfors.Lecture Theatre A, Chemistry Department,Imperial College, South Kensington,London, S. W. 7.Wednesday, loth, 7 p.m.: CardiffWestevn Region, jointly with the South EastWales Section of CS and the UWISTStudent Chemical Society.“Science and Crime,” by R. L. Williams.Department of Chemistry, UWIST, Cardiff.Printed by Heffers Printers Ltd Cambridge Englan

ISSN:0306-1396    

DOI:10.1039/AD97613BX040

出版商:RSC    

年代:1976

数据来源: RSC

摘要:

Vol. 13 No. 11 Proceedings November 1976 of the Analytical Division of the Chemical Society Some New Approaches to Spectrochemical Analysis The following is a summary of the paper presented by Dr. Alan Walsh at a special meeting of the Scottish Region held on June 18th, 1976. The meeting was followed by a luncheon given by the Region in honour of the visit by Dr. Walsli. A General-purpose Atomic Spectrometer for the Analysis of Solutions and Solids by Absorption, Fluorescence or Emission Spectroscopy A.Walsh Division of Chemical Physics, C S I R O , P.O. Box 160, Clayton, Victovia, Austvalia 3168 For nearly a century following the classic work of Kirchhoff and Bunsen, spectrochemical methods of elemental analysis were almost exclusively concerned with atomic-emission spectra.During the past 20 years, however, atomic-absorption methods of analysis have found wide acceptance. Such methods have two main limitations: firstly, as the normal method of atomisation is by means of a flame, the method is not directly applicable to the analysis of solids ; secondly, the method has not proved applicable to the simultaneous determination of several elements.Flame fluorescence methods have some advantages as far as multi- element analysis is concerned but have as yet found little application. Recent work at the CSIRO Division of Chemical Physics in Melbourne has shown that a wide range of metallurgical analyses can be carried out by using atomic-absorption or atomic- fluorescence measurements. In both methods the sample for analysis is made the cathode of a low-pressure discharge in a rare gas, and an atomic vapour of the sample is produced by cathodic sputtering.The successful operation of such methods depends critically on the manner in which the rare gas flows over the metal surface. This operation can now be achieved by use of simple apparatus that is capable of press-button operation. Alloys of iron, aluminium, copper and zinc have been analysed and the following elements determined: antimony, beryllium, cadmium, chromium, copper, iron, magnesium, manganese, molybdenum, nickel, lead, silver, silicon, titanium, vanadium and zinc.The precision is in the range 51 to 53y0 and detection limits are in the range 0.000 3-0.04%. The type of sputtering cell developed for this work has also permitted other applications. For example, it can readily be adapted to provide a wide range of de-mountable atomic- spectral lamps suitable for use in atomic-absorption spectroscopy. It has also proved possible to make de-mountable high-intensity lamps that can be used as light sources, not only in atomic-absorption and atomic-fluorescence spectroscopy, but also in emission spectroscopy.These sputtering chambers can also be used as de-mountable resonance spectrometers, in which the fluorescence from the atomic vapour of a given element serves as a means of isolating resonance lines in the spectrum of that element. Such resonance spectrometers can be used as monochromators in atomic-absorption and atomic-emission spectroscopy. Reson- ance spectrometers based on sputtered atomic vapours are more widely applicable than any other type of resonance spectrometer and it is expected that the de-mountable version will, in most instances, have a higher performance than the sealed-off variety used previously.It has recently been pointed out that it is also possible to use a flame, and in particular a separated flame, as a resonance spectrometer.Although it is of lower performance than 325326 RESEARCH AND DEVELOPMENT TOPICS Proc. AnaZyt. Div. Chem. SOC. sputtering-type resonance spectrometers, the flame has an outstanding advantage in the remarkable ease with which it can be changed from the detection of one element to another. It is necessary only to spray the appropriate solution into the flame and it therefore offers a simple method of automatic sequential analysis. It now appears possible, by appropriate combinations of atomic-spectral lamps, sputtering chambers and flames, to develop a non-dispersive atomic spectrometer that is applicable to the analysis of solutions and solids by atomic-absorption, atomic-fluorescence or atomic-emission measurements.

ISSN:0306-1396    

DOI:10.1039/AD9761300325

出版商:RSC    

年代:1976

数据来源: RSC

摘要:

326 RESEARCH AND DEVELOPMENT TOPICS Proc. AnaZyt. Div. Chem. SOC. Research and Development Topics in Analytical Chemistry The following are summaries of seven of the papers presented at the Research and Develop- ment Topics in Analytical Chemistry meeting of the Analytical Division held on May 4th and 5th, 1976, at the University of Exeter. Some Studies in Optoacoustic Spectroscopy A. A. King, M.J. Adams, B. C. Beadle and G. F. Kirkbright Depavtvnent of Chevnistvy, Ivnpevial College, Louzdon, S W7 2A Y In optoacoustic spectroscopy modulated radiation from a continuum source is employed to illuminate small solid and semi-solid samples contained in a constant-volume cell in air.1,2 The energy absorbed by the sample subsequently appears as heat, which produces a periodic increase in pressure in the cell that follows the modulation frequency of the incident radiation.At a suitable modulation frequency an acoustic signal is thus produced, the amplitude of which can be measured by a simple microphone transducer. The electronic absorption spectra of small solid samples can then be obtained at high sensitivity by observation of the opto- acoustic signal at different wavelengths selected from the continuum source.Suitable single-beam instrumentation for optoacoustic spectroscopy of small solid samples has been describedin earlier reports from this l a b ~ r a t o r y . ~ , ~ With the single-beam apparatus, spectra uncorrected for the variation in output power of the 1-kW xenon-arc source are obtained. A prototype, double-beam optoacoustic spectrometer that permits corrected spectra to be obtained has now been developed. In this instrument, shown diagrammatically in Fig.1, the beam of radiation from the xenon-arc source is passed to an f/4 plane-grating monochromator (Metrospec, V. A. Howe Ltd., London) and divided, after dispersion, to pass Monochromator Source Chopper I = Recorder Fig. I. Doublc-beam spectrometer for optoacoustic spectroscopy with solid samples.November, 1976 RESEARCH AND DEVELOPMENT TOPICS 327 to two identical exit slits.The sample cell is located immediately behind one of the exit slits and a reference cell is placed behind the other. The reference cell contains a carbon- black sample, the optoacoustic signal of which is sensed by a similar microphone to that used in the sample cell.The suitability of carbon-black as a reference absorber has been noted elsewhere1 in a study in which its optoacoustic spectrum in the ultraviolet - visible region was shown to be identical with the source power spectrum, which had been determined radiometric- ally. The signals from the sample and reference cells are taken to two lock-in amplifiers (Model 186 and 124A, PAR Corp., Princeton, N J, USA) and the output from each amplifier is led to a simple ratiometer unit.The variation of the ratiometer output with wavelength then corresponds to the optoacoustic spectrum for the sample, which has been corrected for the variation in source power with wavelength. Two different gratings can be used in the monochromator in order to obtain spectra in the ultraviolet -visible region (50 x 50 mm, 1200 lines mm-l, blazed at 300 nm) and the near-infrared region between 1 and 3 pm (50 x 50 mm, 600 lines mm-l, blazed at 2 pm). Applications The application of optoacoustic spectroscopy in the ultraviolet - visible region to some inorganic materials and samples of clinical and agricultural importance has recently been de~cribed.l-~ Where comparisons are possible, the spectra obtained are similar to the electro- nic light-absorption spectra obtained in solution and complementary to the reflectance spectra obtained for these samples.The advantages of the use of optoacoustic spectroscopy rather than conventional techniques of light-absorption and reflectance spectroscopy include the requirement of only small solid or semi-solid samples and freedom from problems for samples that are highly opaque or that scatter radiation strongly.However, a fundamental difference between optoacoustic spectroscopy and conventional light absorption and reflectance spectro- scopy for solid samples is the dependence of the optoacoustic signal amplitude and phase angle (relative to the modulation waveform) upon the thermal diffusivity of the material under examination.This phenomenon may be particularly valuable for the examination of non- homogeneous samples, which exhibit domains or layers of material of differing thermal diffusivity. This effect has been demonstrated in recent studies in our laboratory in the examination of the optoacoustic spectra of spinach-leaf samples.The optoacoustic spectrum of the chlorophyll in the substrate chloroplast layer is presented out of phase relative to the incident radiation owing to the presence of a waxy surface cuticle layer. The low thermal diffusivity of this layer results in a time delay between the liberation of the thermal energy in the substrate layer after light absorption and its appearance at the surface of the sample to stimulate an intermittent pressure rise in the gas in the cell.By suitable choice of the phase- angle at which the optoacoustic spectrum of a complex heterogeneous system is observed, therefore, it is in principle possible to obtain spectra from different components and to obtain data relating to the thermal diffusivity of surface layers.Recent studies in our laboratory5 have made use of a simple, non-dispersive optoacoustic spectroscopy system in which only white light from a continuum source is employed to irradiate the sample; phase analysis of the resulting optoacoustic signal has been shown to provide a technique for determination of the thermal diffusivity of transparent materials. For a simple system in which an optically transparent layer, the thermal diffusivity of which is to be determined, is backed by a radiation-absorbing la,yer that produces an optoacoustic signal it may be shown, from the Fourier thermal-conduction equation, that .... * - (1) & = - x ~ ’ .. 5 L:I * . where At is the time lag in the “temperature” wave (i.e., the optoacoustic signal) as it passes from its origin in the thin radiation-absorbing backing layer through the transparent layer, x is the thickness of the transparent layer, P is the period of the modulation cycle and a is the thermal diffusivity (ratio of thermal conductivity to heat capacity) of the material of the transparent layer.Equation (1) predicts a linear relationship between the time lag, At, of the optoacoustic signal and PI.The slope of the graph of At versus P’ is then - (l/mt)‘, so that if the thickness of the layer is known its thermal diffusivity can be determined. This method has x 2328 RESEARCH AND DEVELOPMENT TOPICS Proc. AnaZyt. Div. Chem. SOC. recently been used in our laboratory with a model system consisting of a thin glass layer backed by an absorbing black enamel and shown to provide values for the thermal diffusivity of the glass that are in good agreement with values obtained by use of other techniques.As part of an extensive study of the analytical usefulness of optoacoustic spectroscopy for solid samples we have recently begun work in the near-infrared region between 1 and 3 pm. This region promises to provide valuable optoacoustic information for a variety of sample types, including proteins, polymers and samples of geochemical interest.An example of this latter type of sample is given in Fig. 2, which shows the near-infrared spectrumof a montmorillonite. This clay-like series of minerals occurs in soils, clays and metamorphic rocks and their class- ification and identification is of considerable interest. The spectrum is dominated by the strong molecular-absorption bands at 1.4 and 1.9 pm, corresponding to bound water; the wavelength and intensity of these bands varies with the nature and origin of the sample.I 1 I I 1 .o 1.5 2.0 Wavelength/pm Fig. 2. Near-infrared optoacoustic spectrum of a montmorillo- nite. References 1. 2 . 3. 4. 5. Adams, M. J., King, A. A., and Kirkbright, G.F., Analyst, 1976, 101, 73. Rosencwaig, A., Analyt. Chew., 1975, 47, 592. Adams, M. J., Beadle, B. C., King, A. A., and Kirkbright, G. F., Analyst, 1976, 101, 553. King, A. A., and Kirkbright, G. F., Lab. Pvact., 1976, in the press. Adams, M. J., and Kirkbright, G. F., S$ectvosc. Lett., 1976, in the press. Cation Adducts of Non-ionic Surfactants as Ion-selective Electrode Sensors A.M. Y. Jaber, G. J. Moodyand J. D. R. Thomas Chemistry Department, Uflivevsity of Wales Institute of Science a i d Technology, Cavdifl, CF1 3N U Tetraphenylborate (TPB) salts of appropriate metal-ion complexes of nonylphenoxypoly- (ethy1eneoxy)ethanol (NP) [C9H19C6H40(CH2CH20),_,CH,CH,0H] dissolved in suitable nitroaromatic solvents have recently been used as sensing systems in ion-selective electrodes.Thus, the TPB salt of a barium - NP complex prepared from the comniercial NP material Igepal CO-880 (available in the USA) or Antarox CO-880 (available in the United Kingdom), with 30 ethylene oxide units (EOU) per molecule yields effective liquid-membrane barium ion- selective electrodes with P-nitroethylben~ene~-~ and o-nitrodiphenyl ether3 solvent mediators. Long-life poly(viny1 chloride) matrix membrane electrodes require the more viscous and high- boiling o-nitrodiphenyl ether rnediat~r.~ Also, the TPB salt of the strontium - Igepal CO-880 complex has been used with P-nitroethylbenzene in a liquid-membrane electrode for ~trontium.~November, 1976 RESEARCH AND DEVELOPMENT TOPICS 329 Stoicheiometry Polyethylene glycols with the general formula HOCH,(CH,OCH,),CH,OH are related to the NPs and can be similarly converted to the cationic form by the addition of salts, such as barium ~hloride.~ The TPB precipitates have a possible role as cation-selective electrode sensors, according to the metal cation in the adduct.The NP adducts with 10-40 EOUs form pre- cipitates6 with 12 EOU per Ba2+ ion and 2 molecules of TPB- (12EOU. Ba.2TPB). However, the polyethylene glycols of relative molecular mass 600-4 000 form precipitates' with just 10.4 -& 0.2 EOU per Ba2+ ion (10.4EOU.Ba.2TPB) and the present work with Carbowax polyethylene glycol 1540 (actual relative molecular mass 1 520, corresponding to 34EOU) confirmed this stoicheiometry. Similar precipitates can be prepared from the NP derivatives for calcium and strontium, but not for magnesium, while beryllium and ions of the higher alkali metals give TPB precipitates with the cation itself rather than with the adducts.Polypropylene glycols (HOCH,[CH(CH,)OCH,], CH(CH,)OH) form precipitates with 12 propyleneoxideunits (POU) per Ba2+ ion (or Ca2+) and 2 moleculesof TPB- (12POU.Ba.2TPB). The polyethylene glycol and NP derivatives serve as neutral carriers for barium.l Ion-selective Electrode Characteristics Several of the Antarox NP materials gave TPB precipitates with their barium adducts and possessed good barium ion-selective electrode properties when used in solutions (about 0.05 g of precipitate dissolved in about 0.4 g of solvent mediator) with the appropriate nitroaromatic solvent mediator.Within the range studied, the length of the ethylene oxide chain appeared to be of little consequence and electrodes of similar performance were obtained for three differ- ent Antarox NPs, namely CO-850 (20 EOU), CO-880 (30 EOU) and CO-890 (40 EOU). In addition to the normal ion-activity sensing functions, the various barium ion-selective electrodes can be conveniently used in potentiometric titrations, including sulphate versus barium perchlorate in ethanol - water mixtures containing up to 35% of ethanol.However, there is one refinement that considerably improves response time and freedom from drift, namely, the addition of a small amount of the appropriate Antarox NP (about 5% of the adduct - TPB mass) to the sensor prior to assembly of the ion-selective electrode membrane.Functional electrodes made from sensors based on other metal-ion adducts depend on the absence of barium and certain other interfering ions from the solutions. As with the Antarox NP materials, the precipitate with TPB of the barium-ion adduct of Carbowax polyethylene glycol 1540 gives functional barium liquid-membrane ion-selective electrodes with o-nitrodiphenyl ether, but the solubility of the adduct in p-nitroethylbenzene is too low for satisfactory electrode response.Precipitates of the barium and calcium adducts of polypropylene glycol with TPB give erratic ion-selective electrode behaviour when used as sensors with o-nitrodiphenyl ether as solvent mediator. However, while Antarox CO-880.Ba.2TPB is insoluble in dioctylphenyl phosphonate, the solvent will dissolve the TPB precipitates of the polypropylene glycol adducts, which, when used in poly(viny1 chloride) matrix membranes, give good electrode response for barium and calcium, but the high interference from alkali and alkaline earth metal ions may turn out to yield electrodes that are selective to magnesium in preference to calcium. Bulk Extraction Constants Although the above adducts have only recently attracted the attention of electrochemists, their stoicheiometry has been under scrutiny for several year^,^-^ while the non-ionic surfactants themselves are of considerable analytical and general scientific interest.There are, therefore, several reasons for assessing their stabilities in solution. Towards this end, the picrate solvent- extraction methods developed for investigating alkali metal cation complexing by macrocylic polyethers* and macrotetrolide actin antibiotics9~10 have been adapted for measuring bulk extraction constants, Ki, of the complexes between the NP Antarox CO-880 and alkali and alkaline earth metal cations M2+.K1 is the equilibrium constant for the reaction n -Mz+(aq.) +- Antarox CO-880* + %Picrate- (aq.) + (M,lZ Antarox C0-880)z+* + nPicrate-, molecule adduct molecule 2330 RESEARCH AND DEVELOPMENT TOPICS Proc.AnaZyt. Div. Chem. SOC. where the asterisk (*) denotes amounts characteristic of an organic solvent phase (methylene chloride). Some Ki values determined in this work indicate that potassium, rubidium and caesium form very strong, extractable adduct complexes, while, except for beryllium, barium forms by far the strongest extractable complex among the alkaline earth cations (Table I).TABLE I BULK EXTRACTION CONSTANTS, Ki, FOK ALKALI METAL AND ALKALINE EARTH METAL CATIONS BETWEEN WATER AND METHYLENE CHLORIDE Concentrations taken: [Mz+] =I 5.0 x mol dm-3 in water. [Pjcric acid] = 9.22 x mol dm-3 in water.[Antarox CO-8801 = 6.0 x mol dm-3 in methylene chloride. Mz+ Li+ Na+ K+ Rb+ Cs+ Be2+ Mg2+ Ca2+ Sr2+ Ba2+ Ki 1.1 x 18.3 3.9 x 106 1.4 x lo6 3.9 x 106 4.8 x lo2 1.6 x 7.8 x 2.1 x 4.8 A more detailed paper will be published elsewhere. The University of Wales is thanked for a Research Studentship (to A.M.Y. J.). 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. References Levins, R. J., Analyt. Chem., 1971, 43, 1045.Levins, R. J., Analyt. Chem., 1972, 44, 1544. Jaber, A. M. Y., Moody, G. J., and Thomas, J. D. R., Analyst, 1976, 101, 179. Bauman, E. W., Analyt. Chem., 1975, 47, 959. Neu, R., Arzneimittel-Fovsch., 1959, 9, 589. Uno, T., and Miyajima, K., Chem. Pharm. Bull. (Tokyo), 1963, 11, 75. Levins, R. J,, and Ikeda, R. M., Analyt. Chem., 1965, 37, 671. Pedersen, C. J., Fedn Proc.Fedn Am. Socs Exp. Biol., 1968, 27, 1289. Eisenman, G., Ciani, S. M., and Szabo, G., Fed% Proc. Fedn Am. Socs Ex$. Biol., 1968, 27,1289. Eisenman, G., Ciani, S. M., and Szabo, G., J . Membrane Biol., 1969, 1, 294. Microprocessors in Analytical Chemistry P. David Department of Chemistry, University College of Swansea, Singleton Park, Swansea, SA2 8PP By using modern electronic components, in particular microprocessors, it is possible to build a microcomputer that is physically small, yet sufficiently powerful to both control analytical instruments and to process data in order to produce the required results.Such a micro- computer has been used to develop an automatic titrator for the sequential titration of a mixture of adipic and boric acids against sodium hydroxide solution.The computer controls the titration and determines the equivalence volumes by locating the maxima in the differen- tial curve, ApH/AV against V . The computer-controlled titrator was compared with a conventional automatic titrator, which titrates to pre-set potentials, and was found to give equally accurate and repeatable results. The mean equivalence volumes and corresponding standard deviations, obtained by both systems, are shown in Table I.These equivalence volumes are printed on a tpletype. The computer-controlled system, however, has several advantages. 1. Addition of mannitol for the boric acid determination is unnecessary. 2. Titrations can be performed in less than half the time required for titration to pre-set 3. Concentrations of the component acids and instructions for the plant operator can be 4.Calibration of the pH meter and pre-selection of end-points are both unnecessary. 5. It should be possible to connect the electrodes directlyto an Analogue to Digital convertor, 6. The instrument should be capable of dealing with other logarithmic titrations. By end-points, with the same accuracy.printed out. thus making the pH meter redundant. modifying the program, it should also be capable of dealing with linear titrations.Nouembev, 1976 RESEARCH AND DEVELOPMENT TOPICS 331 TABLE I COMPARISON OF THE COMPUTER-CONTROLLED SYSTEM WITH THE CONVENTIONAL TITRATOR AUTOMATIC Computer Conventional controlled titrator Adipic acid Mean equivalence volume/cm3 4.863 4.84 (theoretical Standard deviation*/cm3 0.005 5 0.006 7 = 4.878 cm3) equivalence volume Error, yo -0.31 -0.78 Boric acid Mean equivalence volume/cm3 8.761 8.80 (theoretical Stan:lsrd deviation*'/cm3 0.018 8 0.007 0 = 8.738 cm3) equivalence volume Error, yo +0.26 +0.71 * Based on results of ten titrations.The instrument is thus of general applicability; its cost, excluding the teletype, is much the same as the conventional automatic titrator, it gives equally repeatable results, and it is far more convenient to operate.Details of the various stages of development of the system and an examination of various experimental factors that might affect the value of the equivalence volumes can be found in reference 1. Reference 1 . Betteridge, D., Dagless, E. L., David, P., Deans, D.R., Penketh, G. E., and Shawcross, P., Analyst, 1976, 101, 409. lnterferometric Atomic Line Profile Measurements of Electrodeless Discharge Lamp Sources S. L. Castleden and G. F. Kirkbright Depavtuned of Claeunistvy, Intperial College, London, SLV7 2.A Y The application of electrodelm disclizrge lamps (EDL) as line sources for atomic-absorption and -fluorescence spectrometry is well known.The relatively high intensity of these sources compared with hollow-cathode lamps is especially important in atomic-fluorescence spectro- metry, where the fluorescence signal strength depends upon the incident intensity available from the source. For h e x - calibration graphs in atomic-absorption spectrometry it is particularly important that the profile of the line from the source should be much narrower than the profile of the absorption coefficient in the atom cell.Despite considerable work reported in the literature on EDL sources in recent years, it is still difficult to draw firm conclusions concerning their optimum preparative parameters and operating c0nditions.l Previous evaluations of EDL performance have been made by study- ing either the integrated output intensity at a particular analytical line or by measuring the output indirectly by observation of the fluorescence signal stimulated by the source from a flame containing atoms of the element of interest.In our studies we have used a high- resolution, piezoelectric-scanning, Fabry - Perot interferometer2p3 to investigate the fine structure of the lead 405.78-nm line emitted by a microwave-excited EDL source.In the conventional mode of operation the EDL is supplied with microwave radiation, which must both provide the energy to excite the discharge and also provide a sufficiently high temperature to produce the necessary vapour pressure of the metal in the lamp. By thermo- statically controlling the EDL it is possible to regulate the vapour pressure within the envelope separately.* We have used a Broida-type $-wave resonant cavity, supplied at 2 450 MHz by332 RESEARCH AND DEVELOPMENT TOPICS Proc.Analyt. Din. Chem. SOC. a 200-W Microtron 200 generator via a reflected power meter. Hot air for thermostatic control of the EDL source was supplied by a heater coil adjacent to the resonant cavity.Without using the interferometer, a scan of the integrated lead 405.78 nm line intensity at different positions across the diameter of the EDL was made. This scan showed a maximum of intensity just inside the wall of the EDL and a minimum, of about one-third of the maximum value, in the centre of the tube. This experimental observation does not conform to the dis- tribution expected on the assumption that a homogeneous microwave discharge exists within the envelope.A homogeneous discharge in a cylindrical tube would be expected to yield a maximum of intensity in the middle as a result of the optical depth being greater than at the edges. As a minimum of intensity was observed in the middle of the discharge it seemed pro- bable that a skin discharge effect was present in the particular EDL employed in this instance, i.e., more emitting atoms were present at the edge than in the centre of the source.In order to obtain more data concerning the nature of the discharge within the EDL, measurements were made of the degree of self-absorption at different positions across the discharge within the envelope. These measurements were carried out by examining the hyperfine structure of the lead 405.78-nm line. When the lead 405.78-nm line is viewed with high resolution, the splitting caused by isotopic shift and nuclear-spin effects can be seen.Isotopic shift results from variations in nuclear mass and/or volume between different isotopes. Consequently, natural lead emits individual lines for each of the isotopes 204Pb, 206Pb, 207Pb and 208Pb.Nuclear spin causes further splitting of lines emitted by isotopes that do not possess an even number of protons and neutrons. In the instance of lead this situation only applies to 207Pb and results in three lines, designated 207Pb strong, 207Pb medium and 207Pb weak, the theoretical intensity ratio of which, in the absence of self-absorption, can be calculated as 9 : 5 : 1, respectively.As the lines that are strongest in emission are also the strongest in absorption, the theoretical intensity ratio will decrease as the degree of self-absorption increases. The intensity ratio of the 207Pb strong: 207Pb medium lines at 405.78 nm was measured in order to establish the variation in the degree of self-absorption across the EDL discharge.Fig. l ( a ) shows this variation for an EDL operated at 400 "C using 30 W of absorbed power. The intensity ratio reaches a minimum at about 0.5 mm inside the wall of the EDL (B,D) indicating a maximum of self-absorption, and increases gradually towards a maximum in the centre of the source (C). Between the mini- mum and the edge, the ratio increases rapidly and approaches the theoretical value. If the absorbed power is increased or decreased a curve of similar shape, but displaced below or above, respectively, that trace shown in Fig.l ( a ) is obtained. As expected, the over-all self-absorp- tion increases as the absorbed power increases. The same effect is observed with increasing operating temperature ; an increase in temperature results in greater self-absorption.An EDL was prepared from the pure 207Pb isotope. T heoret ica I val u e E 4 3 2 1 0 1 2 3 4 Relative position of electrodeless discharge lamp/mm Scanning -- Fig. 1 (a). lamp source. to the skin discharge effect observed experimentally. Distribution of the intensity ratio Zo7Pb strong : 207Pb medium across an electrodeless discharge ( b ) , Model approximating Operating temperature, 400 "C; absorbed microwave power, 30 W.Novembev, 1976 RESEARCH AND DEVELOPMENT TOPICS 333 We have constructed a very simple geometric model, which gives a first-order approximation to the shape of the experimentally observed distribution. If the internal radius of the EDL is Y and the displacement of the viewing position from the central optical axis through the EDL is x, we can define a distance t from the inside surface of the EDL as marking the inner boundary of a hypothetical skin.The optical depth through the skin, viewed at position x, is equal to L, where L = (9 - x2)$ - [(r - t ) 2 - X2]* Fig. l ( b ) shows L plotted as a function of x, for t = v/lO. It can be seen that this distribution is close to the shape of the distribution observed experimentally.However, the model is not exact, particularly in the central region of the source, where its shape is flatter than that observed experimentally. This difference suggests that there are further parameters, as yet undetermined, which need to be taken into account in order to explain fully the distribution observed experimentally. By measuring the positions of the maxima in Fig.1 ( a ) from the edge, the inner edge of the skin in the discharge is apparently about 0.5 mm from the inner surface of the tube. However, it is not clear whether this distance, which is equal to the parameter t in the model, represents the true thickness of the skin; the skin might not extend to the surface of the tube. These results do not preclude the existence of emitting atoms in the centre of the tube, but the emission from a layer around the edge of the source is more intense than in the rest of the lamp and this layer appears to have a predominant effect on the degree of self-absorption in the radiation from the EDL.These studies are being continued with the measurement of actual atomic line widths of the emission from single-isotope lead EDL sources and of the Doppler temperature at different positions within these sources.Towards the edge of the source the model fits the experimental results more closely. References 1. 2 . 3. 4. Haarsma, J . P. S., de Jong, G. J., and Agterdenbos, J., Spectvochim. Acta, 1974, 29B, 1. Kirkbright, G. F., and Sargent, M., Spectvochim. Acta, 1970, 25B, 577.Kirkbright, G. F., and Troccoli, 0. E., Spectvochim. Acta, 1973, 28B, 33. Browner, R. F., and Winefordner, J . D., Spectvochim. Acta, 1973, 28B, 263. Problems in the Environmental Analysis of Phthalate Esters R. D. J. Webster and G. Nickless Department of Inorganic Chemistry, The University of Bristol, Cantock's Close, BYistol, BS8 I T S Phthalate esters are used widely in industry, mainly as plasticisers in flexible poly(viny1 chloride) (PVC).ly2 Recently, there has been concern over their toxicology and fate in the en~ironment"~ and a need therefore exists for a dependable method of analysis for trace amounts of these potential environmental pollutants.The presence of phthalate esters in an environmental sample can be due to one or more of the following : (i) phthalates occurring naturally in the environment ; (ii) phthalates introduced into the environment by man prior to sampling, i.e., environmental pollution; and (iii) phthalates introduced after sampling, i.e., laboratory contamination. It has often proved difficult to ascertain the true reason for the presence of phthalates in an environmental sample.In several reports6-8 of the environmental occurrence of phthalate esters, laboratory contamination has not been given adequate consideration.In many methods, procedural blanks have shown higher levels of phthalate than those generally found in the environment. Hence the development of a reliable method has been hindered by the ubiquity of phthalate esters within the laboratory materials. The general scheme employed in the analysis of a sediment or water sample involves extraction into an organic solvent, clean-up by alumina column chromatography, fraction- ation by Florisil column chromatography or silica gel G thin-layer chromatography and334 RESEARCH AND DEVELOPMENT TOPICS Proc.AnaZyt. Div. Cheun. SOC. finally, quantification by gas - liquid chromatography with electron-capture detection.Confirmation is achieved by injection into two columns, by spectrophotofluorescence or by hydrolysis to phthalic acid followed by derivatisation to form the methyl ester or N-(2- chloroethyl) phthalimide . Using this procedure, the sample will come into contact with a variety of laboratory reagents and equipment, all of which pose a potential threat of contamination to the pro- cedure.In order to locate the sources of contamination, laboratory reagents and equipment used in the analysis were Soxhlet extracted with benzene and analysed for their phthalate content. The suggested cleansing methods are pre- sented in Table 11. The results are presented in Table I. TABLE I PHTHALATE ESTERS IN LABORATORY REAGENTS AND EQUIPMENT Ester*/ng g-l r Florisil Alumina Silica gel G Extraction thimble Amberlite XAD-4 Polyurethane foam Aluminium foil Glass-wool Air Florisil cap Pipette filler DEHP BBP 35.6 2.4 7.0 415 15.6 55.5 77.3 840 700 000 N.D.107 774 P P - - - - - - - - DCHP DBP DIBP __ 21.7 76.7 - 79.2 - 3 125 22 300 1620 590 N.D. N.D. N.D. - 69.5 20.1 185 285 - P - - - - - - - - - - DNP N.D. N.D. N.D. N.D. N.D. N.1).N.D. N.D. - - P *DEHP = di-2-ethylhexyl phthalate ; BBP = butylbenzyl phthalate ; DCHP == dicyclohexyl phthalate ; DBP = dibutyl phthalate; DIBP =: diisobutyl phthalate; DNP =: dinonyl phthalate. N.D. = not deter- mined; P = present. TABLE I1 CLEANSING METHODS Reagent Cleansing method Reagent Cleansing method Florisil Muffle (450 "C) XAD resin Solvent extraction Alumina Muffle (600 "C) Polyurethane foam Solvent extraction Silica gel G Pre-elution with polar solvent Extraction thimble Solvent extraction Aluminium foil Muffle (375 "C) Glassware Muffle (375 "C) after washing Glass-wool Muffle (375 "C) Solvents Distillation in an efficient still Muffling is used whenever possible as it is an easy and efficient method, but the temperature of muffling is very important with chromatographic reagents because it affects their surface properties and therefore should be strictly controlled.For those reagents which decompose at elevated temperatures, Soxhlet extraction with a polar solvent has to be the method of choice. XAD resins, polyurethane foams and extraction thimbles are organic materials and it is very difficult to remove all traces of organic contaminants even with prolonged periods of Soxhlet extraction. Amberlite XAD-4 is not heavily contaminated and is therefore safe to use. However, the use of extraction thimbles and polyurethane foam (of the type tested) should be avoided if possible as it leads to higher procedural blanks.Washing glassware in detergent does not guarantee the removal of all organic matter and when low blanks are required muffling is recommended.By using the above precautions, procedural blanks can be lowered to the levels presented in Table 111. Compared with organochlorine pesticides and PCBs, phthalate esters have a low electron- capture response and therefore an efficient technique is required to separate them from co- extracted highly electron-capturing species. However, the wide range of polarities that phthalates also exhibit renders chromatographic separation as a group rather difficult.TheNovember, 1976 RESEARCH AND DEVELOPMENT TOPICS TABLE I11 335 PROCEDURAL BLANKS FOR THE ANALYSIS OF A 50-g SEDIMENT SAMPLE Phthalate ester Level/ng Di-2-ethylhexyl Butylbenz yl Dicyclohexyl Dibutyl Diisobutyl 40 23 87 20 50 method adopted has been to collect the phthalates in a number of fractions, thus minimising the number of co-extracted compounds in each fraction.The sediment (or water) extract is applied to a 2 cm i.d. column of deactivated alumina (20 g) and eluted with 40 ml of hexane (fraction I), 100 ml of 6% diethyl ether in hexane (fraction II), 100 ml of 15% diethyl ether in hexane (fraction 111), 100 ml of 25% diethyl ether in hexane (fraction IV) and 100 ml of 50% diethyl ether in hexane (fraction V).Most phthalate esters are eluted in fraction 111, the more polar oxygenated phthalates in fraction IV and dimethoxyethyl phthalate in fraction V. Further fractionation of fraction I11 is effected by thin-layer chromatography on silica gel G with 10% ethyl acetate in hexane as the developing solvent.The phthalate esters have RF values between 0.18 and 0.60 and several fractions can be scraped off and recovered from the plate, The range of volatilities of phthalate esters has rendered isothermal gas chromatography difficult and quantification of both high- and low-boiling esters requires injection at two temperatures. The columns that have been used are listed in Table IV together with their optimum operating temperatures and the relative retention times of several phthalate esters.Using the above methods, sediments from the River Mersey and the Mersey Estuary were found to contain dinonyl phthalate, di-2-ethylhexyl phthalate, dibutyl phthalate and di- isobutyl phthalate at levels between 48 and ll 400 ng g-1. TABLE IV GAS CHROMATOGRAPHY OF PHTHALATE ESTERS Columns: glass, 6 f t x & in i.d.Carrier gas flow-rate: 40 ml min-l. Detector: 63Ni electron-capture de- tector, tD = 300 "C, purge gas flow-rate 40 ml min-l. Retention time (relative to DEHP) * r - 1 Column temperature/"C DBP DAP DMEP DNP DCHP 1.5% OV-17/1.95% QF-1 on Gas-Chrom Q 215 0.19 0.25 0.30 1.38 1.24 3% DEGS on Gas-Chrom Q 180 0.25 0.29 1.29 1.30 2.19 3% Poly-I 110 on Gas-Chrom Q 205 0.16 0.22 0.25 1.44 1.29 DBP = dibutylphthalate; DAP = diamyl phthalate; DNP = dinonyl phthalate; DCHP = dicyclohexyl phthalate ; DEHP = di-2-ethylhexyl phthalate; DMEP = dimethoxyethyl phthalate.1. 2. 3. 4. 5. 6. 7. 8. References Chem. Engng News, 1972, 50(38), 14. Graham, P. R., Envir. Hlth Perspect., 1973, 3, 3. Singh, A. R., Lawrence, W.H., and Autian, J., J . Phavm. Sci., 1972, 61, 51. Mayer, F. L., Jr., Stalling, D. L., and Johnson, J. L., Nature, Lond., 1972, 238, 411. Metcalf, R. L., Booth, G. M., Schuth, C. K., Hansen, D. J., and Lu, P., Envir. Hlth Perspect., 1973, Khan, S. U., and Schnitzer, M., Soil Sci., 1971, 112, 231. Stedman, R. L., and Dymicky, M., Tob. Sci., 1959, 3, 57. Perkins, E. G., J .Am. Oil Chem. SOC., 1967, 44, 197. 4, 27.336 RESEARCH AND DEVELOPMENT TOPICS Proc. Analyt. Div. Chew. SOC. Polarographic Studies of Some Foreign Organic Compounds in the Aqueous Environment J. P. Hart, W. Franklin Smyth Department of Chemistry, Chelsea College, Manresa Road, Lovzdon, S W3 6LX and B. J. Birch Unilever Rcsearch, Port Sunlight, Cheshive In recent years, sensitive polarographic methods have been increasingly used for the assay of a variety of organic species in the aqueous environment.In this paper, we present a short historical survey on the application of these methods to trace organic analysis of the environ- ment, and then show how the technique has been applied to selected compounds. Emphasis has been placed on two specific areas: (a) derivatisation reactions via nitration of aromatic nuclei, with special reference to alkylbenzene sulphonates and alkane sulphonates, and (b) the application of polarography to the study of the absorption and metabolism of a series of selected aromatic nitro and azo compounds.Historical Survey Some are the natural breakdown products of aquatic plants and animals, but a vast number enter lakes, rivers and seas through industrial sources such as paint and soap manufacturing in- dustries, oil refineries and breweries1 With the levels of concern sometimes being as low as micrograms per litre,1-3 very sensitive methods of analysis are required.Of the analytical techniques used, the more common ones are gas chr~matography,~ mass ~pectroscopy,~ nuclear magnetic resonance spectroscopy,6 spectrofluorimetry7 and electrochemical methods.8 Polarography and its offshoots, such as stripping voltammetry, are the most widely used voltammetric methods at finite current.Polarography, in particular, has been applied at sub-parts per million levels to the assay of a variety of foreign compounds. Formaldehyde and acetaldehyde have been determined in treated waste water,g and styrene and methyl methacrylate in waste water.1° The triazine herbicides ametryne, atrazine and terbutryne have been determined in pond and canal water,ll whereas nitrilotriacetic acid,12 a constituent of many laundry detergents, has been assayed in sewage and surface waters.The anionic surfactants sodium dodecyl sulphate and sodium dodecylbenzenesulphonate have also been determined polarographically in surface water.13 Solvent-extraction methods are often employed prior to polarographic analysis of the organic pollutant.Benzene was found to be a suitable solvent for the separation of hexachlo- robutadiene,14 styrene and methyl methacrylate from waste water.1° The triazine herbicides were found to be amenable to solvent extraction with dichloromethane,ll while the herbicide NN-diet hyl-2,6-dinitro-4-t rifluoromet hylaniline was found to separate into hexane .15 In some instances, extraction has not been found necessary before polarographic determination.This is exemplified by the determination of the explosive 2,4-dinitrotoluene directly in well water. Sea water, containing the plasticiser dibutyl sebacate, was also analysed polaro- graphically without preliminary extraction.16 A summary of polarographic data for the above compounds is given in Table I.The origins of organic species in the aqueous environment are many and varied. Polarography of Alkylbenzenesulphonates (ABSs) and Alkanesulphonates (ASS) After Nitration The aim of this work was to develop a method that would permit the low-level determination and differentiation of alkylbenzenesulphonates and alkanesulphonates.These compounds do not possess a polarographically active group, although indirect methods have been devised for their determination.9~10 However, these methods do not differentiate between different types of ABS or AS. One of the most suitable derivatisation procedures is nitration of aromatic nuclei to give species that give well defined polarographic wave^^^,^* corresponding to reduction of theNovember, 1976 RESEARCH AND DEVELOPMENT TOPICS TABLE I SUMMARY OF POLAROGRAPHIC DATA FOR SOME FOREIGN ORGANIC SUBSTANCES FOUND I N THE AQUEOUS ENVIRONMENT 337 Substance Formaldehyde Acetaldehyde Reduction Limit of Supporting electrolyte potential/V detection/mg 1-1 LiOH solution - 1.50 4.00 - 1.90 4.00 Hexachlorobutadiene 0.2 M (Et),NI - 80% Me,CO -0.98 0.20 Atrazine Ametryne Terbutryne 50% MeOH - 0.01 N H,SO, - 1.05 0.10 - 1.45 0.10 - 1.45 0.10 NN-Diethyl-2,6-dinitro-4- (Et),NOH - MeOH - H,O -0.85 0.01 trifluoromethylaniline Methyl methacrylate Styrene 0.025 N (Et),NI - C6H6 - 1.70 0.15 - DMF - HZO - 1.90 0.19 2,4-Dinitrotoluene Well water -0.55 0.50 1,2-Propylene glycol dinitrate Sea water Dibutyl sebacate -0.45 1.27 - 1.30 7.76 Nitrilotriacetic acid Cd(OAC), - NHdC1- NH, -0.80 1 .oo Sodium dodecyl sulphate 0.1 M KC1 - Sodium dodecylbenzenesulphonate ,1.30 1.00 NO, group.Preliminary experiments were carried out to determine whether electroactive ABS and AS species could be produced using this reaction. Table I1 shows the types of surfactants selected for derivatisation. The first four compounds in the table are straight- chain ABSs, the next five are branched-chain ABSs and the last three are alkanesulphonates with a phenyl substituent.TABLE I1 STRUCTURAL CLASSIFICATION OF ABS AND PHENYL-CONTAINING AS COMPOUNDS SUBJECTED TO NITRATION No. I I r 111 I V V VI Compound Sodium 4-decyl- benzenesulphonate Sodium 4-tridecyl- benzenesulphonate Sodium 4-pentadecyl- benzenesulphonate Sodium toluene-4- sulphonate Sodium 4-(l-methyl)- tridecylbenzene- sulphonate Sodium 4-(l-ethyl)- heptylbenzene- sulphonate x u 2 No. Compound X Y 2 SO,- H C,H1, VII Sodium 4-(l-propyl)- SO,- C,H, C,H,, nonylbenzenesul- phonate SO,- H C,,HZS VIII Sodium 4-(l-penty1)- SO,- C5Hll COH13 heptylbenzene- sulphonate SO,- H C1,H,, IX Sodium 4-(l-hexyl)- SO,- C6H,, C,H,, heptylbenzenesul- phonate tetradecanesul- phonate tetradecane- sulphonate pentadecane- sulphonate SO,- H H X Sodium 2-phenyl- H C,,H,, CH2S0,- SO,- CH, C12H2, XI Sodium 7-phenyl- H C,H1, C,Hl,SO,- SO,- C,H, C6H,, XI1 Sodium 3-phenyl- H C12HZ5 C,H,SO,-338 RESEARCH AND DEVELOPMENT TOPICS Proc.Analyt.Diu. Chewz. SOC. Vigorous nitration conditions were first tried, using a mixture of 37.5% fuming nitric acid in concentrated sulphuric acid. Several milligrams of the substance were heated for 30 min on a steam-bath with this nitrating mixture. After dilution with distilled water, diff- erential pulse polarograms were recorded in Britton - Robinson buffer of pH 12.0, a pH that gave the best defined and largest peaks.A PAR 174A polarograph was used, incorporating a three-electrode system (saturated calomel reference, platinum counter and dropping mer- cury electrodes). The differential pulse polarograms of the two classes of ABS mentioned showed two peaks consistent with the formation of a dinitro derivative with the groups almost certainly in the 2,6-positions.The straight-chain ABSs gave a reduction potential in the region -0.520 to -0.530 V and another in the region -0.690 to -0.720 V, whereas the first reduction potential for the branched chain ABSs was -0.540 to -0.560 V and the second occurred at -0.760 V. Only one peak, occurring at -0.56 to -0.57 V, could be observed for alkanesulphonates containing a phenyl ring. Having shown that the surfactants could be nitrated on the macro- scale, nitration was next tried on microgram amounts of the compounds.Again, two re- duction peaks were observed on the differential pulse polarograms, corresponding to dini- t rat ion. A clean-up procedure was introduced to separate the nitro derivative from the nitration mixture, involving solvent extraction with butan-2-one.This procedure had the effect of reducing background interference, but resulted in a low percentage extraction of the derivative in trace determinations. Fuming nitric acid, which could easily be evaporated off following nitration, was then evaluated as an alternative nitrating agent. Microgram amounts of representative sul- phonates were nitrated with fuming nitric acid (0.1 ml) for specific periods of time (15-60 min) and at different temperatures (30-100 "C).Excess of nitric acid was blown off with nitrogen and the residue made up in 5 ml of Britton - Robinson buffer of pH 12.0. The largest and best defined differential pulse peaks were obtained after a period of 15 min at 30 "C. All of the sulphonates nitrated under these conditions showed only one peak, suggest- ing mononitration.The reduction potential of the straight-chain ABSs was found to occur in the region -0.660 to -0.670 V, branched-chain sulphonates -0.720 to -0.740 V and phenyl-containing ASS -0.730 to -0.740 V. A mixture of the nitro derivatives of a straight- chain ABS (sodium 4-pentadecylbenzenesulphonate) and a branched-chain ABS [sodium 4-( 1- hexyl) heptylbenzenesulphonate] was polarographed.A complete resolution was not attained, although two definite peaks could be distinguished. As alkanesulphonates with a phenyl ring gave reduction peaks at the same value as branched-chain ABSs, differentiation between the two was not possible. It should be mentioned here that sulphonates without a phenyl ring do not give nitro derivatives.Calibration graphs were constructed for the compounds mentioned previously and linearity found in the region 5-50 pg. The coefficient of variation at the lower end was 8.25% and at the upper end 7.90%. From these studies, the applications on the macro-scale were considered to be the differen- tiation of alkylbenzenesulphonates (branched- and straight-chain) and alkanesulphonates with a phenyl ring from alkanesulphonates without a phenyl ring following vigorous nitration with fuming nitric acid - concentrated sulphuric acid a t 100 "C for 30 min.This could be applied to formulation analysis. Assay of micro-amounts of phenyl-containing sulphonates using fuming nitric acid at 30 "C for 15 min has application in the identification and deter- mination of some sulphonates in effluents, etc.Work is being carried on with this in mind. Polarographic Study of the Absorption and Metabolism of Azo and Aromatic Nitro Compounds by Daphnia Many toxic organic substances enter the aqueous environment through effluent discharges from factories, domestic supplies and land run-0ffs.l Aquatic invertebrates and other marine animals can absorb, and possibly metabolise, these compounds, with the result that they can build up large concentrations in their bodies and maybe even convert non-toxic into toxic substances. Metabolites may be retained in the animal or passed back into the aqueous system.There is also the possibility that predators feeding on the animals will build up much larger concentrations of the organic substances.If these predators are fish, then harmful effects on man can occur.November, 1976 RESEARCH AND DEVELOPMENT TOPICS 339 With this in mind, a study of the absorption of selected organic compounds by daphnia was carried out in the laboratory. Daphnia, as examples of invertebrates, have been used by the French authorities as a means of measuring toxicitylg and by other workers for studying the absorption and metabolism of organic compounds.20 Two sets of experiments were carried out: ( a ) to compare the effects of azo compounds and aromatic nitro compounds on daphnia with respect to toxicity, absorption and metabolism, and (b) to study in greater depth a structurally related group of azo compounds.(a) The compounds chosen for this comparison were the azo compounds methyl red and methyl orange, and the aromatic nitro compounds 4-nitrophenol and 4-nitroaniline. Solutions of these four compounds were made up from stock solutions in methanol to give a concen- tration in aquarium water of Equal numbers of daphnia were placed in each solution and differential pulse polarograms were recorded for each solution over a period of several days.Controls with and without daphnia were set up under identical conditions. The relative rates of absorption were found from graphs of peak current veysus time and toxic effects evaluated from observations of the number of dead daphnia. Attempts were made to locate metabolites within the daphnia by extracting dead daphnia with methanol, evaporating the methanol to dryness and re-dissolving the residue in aquarium water. The results showed that methyl orange exhibited the greatest absorption rate, methyl red and 4-nitroaniline were absorbed at a comparable rate and 4-nitrophenol was least absorbed.The toxicity of the azo compounds was found to be greater than that of the aromatic nitro compounds, although this result could be related to the extent of absorption.Extraction with methanol and polarography of the residue in aquarium water showed only a small percentage recovery of the parent compounds. The polarograms did not show any new peaks during the course of the experiments, nor was a new peak from the extraction observed. The small percentage recovery of the parent compounds from daphnia could be due to in- efficient extraction, or if metabolism had taken place a polarographically inactive species could have been formed.( b ) In this study, Orange RN (a food dye), Sudan I (a dye listed to have mild carcinogenic effects), and a series of textile dyes were studied. Stock solutions were made up in distilled water and diluted to M in aquarium water. The procedure was the same as for (a) except that no extractions were carried out.It was found that over a period of several days, peak currents for control and test solutions were not significantly different, this behaviour being exhibited by Orange RN, Sudan I, Direct Red 80, Acid Red 73, Direct Blue 84 and Direct Orange 34. Studies showed that the red textile dyes were comparable to Orange RN and Sudan I in toxicity, but the blue and orange dyes were less toxic.From the results, it appears that small amounts of methanol, present from dilution of the stock solution, enhance the absorption rate by daphnia, as in ( b ) methanol was absent. This effect may be due to expansion of pores in the membrane, allowing greater diffusion of solu- tion into the daphnia. Thus, the effect of methanol would be to increase the absorption rate and possibly toxicity.The presence of metabolites was not detected polarographically ; either it did not occur or it may have been due to the formation of polarographically inactive species or inefficient extraction procedures. It was concluded that in the understanding of the effect of organic compounds on aquatic life, the over-all conditions in which the species live have to be considered.While it is possible to gain information on toxicity, absorption and metabolism from simple experiments, care should be taken in interpretation because, in the real situation, other factors such as age, environmental conditioning and population would probably influence results. M. M with aquarium water, or made up directly to 1. 2. 3. 4. 5.References Sproul, 0. J ., “Origin of Organic Chemical Pollutants in Water Supplies,” Doctoral Dissertation, Washing University, St. Louis, Mo., 1961. Henderson, C., Pickering, Q. H., and Tarzwell, C. H., “The Toxicity of Organic Phosphorus and Chlorinated Hydrocarbon Insecticides to Fish,” Transactions of Second Seminar on Biological Problems in Water Pollution, R. A. Taft Sanitary Engineering Center, Tech.Rep. No. W60-3:76, 1960. Rosen, A. A., Peter, J. B., and Middleton, F. M., J . Wat. PoZlut. Contvol Fed., 1962, 34, 1 and 7. Cukor, P., and Madlin, H., J . Wat. PoZZut. ControZ Fed., 1973, 4, 1557. Roboz, J., J . Wat. Pollut. Contvol Fed., 1973, 4, 1617.340 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. RESEARCH AND DEVELOPMENT TOPICS PYOC.Analyt. Div. CJzem. SOC. Keith, L. H., Garrison, A. W., Walker, M. M., Alford, A. L., and Thruston, A. D., Jr., Am. Chern. Sunahara, H., Ishihara, Y., Ishizuka, T., Nakashima, K., and Tanaka, K., Chern. Econ. Engng Rev., Maienthal, E., and Taylor, J. K., Wat. Pollut. Handb., 1973, 4, 1751. Kuchomova, N. A., Trudy Vses. Nauchno-issled. Inst. Pererab. Ispol 'zov Topl., 1963, 12, 237.Mechkova, 0. V., and Dmitrieva, V. N., Zav. Lab., 1974, 40, 28. McKone, C. E., Byast, T. H., and Hance, R. J., Analyst, 1972, 97, 653. Wemet, J., and Wahl, K., Z. Analyt. Chem., 1970, 251, 373. Shinozuka, N., Suzuki, H., and Hayano, S., Japan Analyst, 1972, 21, 517. Solonar, A. S., and Bael, N. G., Gig. Sanit., 1967, 32, 66. Filimonova, M. M., Gorbunova, V. E., and Filimonov, B.H., Z h . Analit. Khim., 1975, 30, 358. Whitnack, G. C., Analyt. Chem., 1975, 47, 618. Audouard, Y., Suzanne, A., Vittori, O., and Porthault, M., Bull. SOC. Chirn. Fr. I , 1975, (1-2), 130. Adamovsky, M., Vod. Hospod., 1966, 16, 102. Tournier, R., Trait. Surface, 1974, 15, 129. Smyth, W. F., and Hassanzadeh, M., 2. Analyt. Chem., 1976, 280, 299. Soc., Div. Water, A i r , Waste Chern., Gen.Pap., 3-6, 1969. 1970, 2, 34. Some Analytical Problems Concerning Trace-metal Analysis in Human Placentae A. K. Khera and D. G. Wibberley Department of Pharmacy, University of Aston in Birmingham, Birmingham, B4 7 ET There are few reports on trace-metal analysis of human placentae. analytical problems concerning placental lead are described. placental cadmium is also reported.In the present paper, Some preliminary work on Lead in Human Placentae Lead is known to cross the placental barrier.1-3 It is also known to cause various kinds of congenital anomalies in there are reports to suggest that it may cause sterility, abortion and congenital malformations in human beingsg-l1 but these reports are not sub- stantiated by lead analysis. However, the reported values of lead in normal human placentae are approximately 0.5-1.0 pg g-l on a fresh mass basis.12-14 In most of the work that has been reported determinations were made by using dry-ashing techniques, the samples being dried overnight, followed by ashing at 550 "C for 16 h, dissolving the ash with various acids and finally determining the metal contents by flame atomic-absorp- tion spectroscopy.In a separate study we found that dry ashing at such high temperatures caused an excessive loss of lead, in agreement with the radiochemical studies for lead in blood and other biological r n a t e r i a l ~ . ~ ~ , ~ ~ In our studies, there were considerable losses of placental lead when the ashing temperature and duration were 500 "C and 22 h. There were complete losses of lead when the samples were ashed at 550 and 600 "C for 20 and 22 h, respectively.It was also observed that excessive blood adhering to the placenta was also a cause of variations in results obtained. In all subsequent work excessive blood was therefore removed with cotton sponges. By use of this technique, oven-dried placentae produced a constant composition (16-18%, wz/m).Further work was then attempted with wet-acid digestions. With these procedures complete recovery was not always possible. On considering these problems, it was decided to investigate the use of Soluene-350, a quaternary ammonium hydroxide tissue solubiliser specifically formulated with toluene. This product is manufactured by Packard Instrument Company Ltd.l7 Soluene-100 has been used18 for the determination of zinc, copper, iron and manganese in animal tissues by flame atomic- absorption spectroscopy.Determinations of cadmium, nickel and zinc in rat lungs by flame atomic-absorption spectroscopy and using an unspecified quaternary ammonium hydroxide have also been reported.lg Excessive blood was removed by means of cotton sponges, the samples were homogenised in a tissue homogeniser for approximately 5 min, without addition of water, and preserved by storing at -20 "C.The preserved samples were thawed and weighed out in 500-mg portions into glass test-tubes. Placenta samples in Soluene were prepared in the following manner.Novembev, 1976 RESEARCH AND DEVELOPMENT TOPICS 341 Portions (5 ml) of Soluene were added to each tube and the samples warmed in a water-bath for approximately 4 h.The blank and standard samples were also prepared in Soluene and toluene. The samples thus prepared were analysed directly on a Perkin-Elmer Model 360 atomic- absorption spectrophotometer fitted with a deuterium background corrector and an HGA 74 graphite furnace. The experimental conditions used have been reported.20 The analytical results obtained for lead levels in normal human placentae are given in Table I.The solubilised samples were then diluted to 10 ml with toluene. TABLE I LEAD IN NORMAL HUMAN PLACENTAE PI acenta Lead/ pg 8-l (fresh mass) 5 0.57 6 0.48 7 0.37 8 0.37 9 0.59 10 0.36 11 0.15 12 1.40 13 0.89 14 0.17 25 0.63 26 0.62 27 0.82 28 1.32 29 0.44 Arithmetic mean, 0.63 Range, 0.15-1.40 Standard deviation, 0.36 Placenta samples in Soluene were sent to other laboratories for confirmation of the results.The Soluene method for placental analysis appears to have the following advantages. (i) The method is rapid. sample loss or contamination. (ii) There is no loss of lead at room temperature over at least a 3-month storage period. The technique was not successful when oven-dried or ashed placental samples were used. The results obtained were in close agreement with the results shown here. Few stages of sampling are involved and there is less chance of Cadmium in Human Placentae For similar reasons to those described for the determination of lead, dry ashing and wet-acid digestions were not suitable for the determination of cadmium. Preliminary work indicated the presence of cadmium as a contaminant in Soluene, but its absence in aqueous tetramethyl ammonium hydroxide. The results for placental cadmium obtained by using aqueous tetra- methyl ammonium hydroxide, 0.02 pg 8-l of cadmium (fresh mass), are close to the reported cadmium levels in normal human placentae. Further work on the details of the determination of cadmium is continuing at the present time. The present work was carried out under contract No. 8304 of the E. C. Environmental Research Programme. The authors acknowledge financial support. 1. 2. 3. 4. 5. 6. 7. 8. References Raumann, A., Amh. Gynaek., 1933, 153, 584. Oliver, S. T., B y . Med. J . , 1911, 1, 1096. Yamaguchi, S., Fukuoka Tgaku Zassi, 1955, 46, 348. Butt, E. M., Pearson, H. E., and Simonsen, D. E., PYOC. SOC. Ex+. Biol. Med., 1952, 79, 247. Catizone, O., and Grav, P., J . Ex+. Zool., 1941, 87, 71. Ferm, V. H., and Carpenter, S. J., Exp. Mol. Pathol., 1967, 7, 35. Hammett, F. S., and Wallace, V. L., J . Ex+. Med., 1928, 48, 659. Karnofsky, D. A., and Ridgway, L. P., J . Pharmac. Ex+. They., 1952, 104, 176.342 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. DETECTION LIMITS AND TRACE ANALYSIS Proc. Analyt. Div. Chewz. SOC. Koinuma, B., Jap. J . Hyg. Infect. Dis., 1926, 21, 56. Potter, E. L., “Pathology o€ the Fetus and the Newborn,” The Yearbook Publishers, Chicago, 1957. Willis, R. A., “Pathology of Tumours,” Butterworths, London, 1948. Baglan, R. J., Brill, A. B., Schulert, A., Wilson, D., Larson, K., Dyer, N., Mansour, M., Schaffner, W., Colucci, A. V., Hammer, D. I., Williams, M. E., Hinners, T. A., Pinkerton, C., Kent, J. L., and Love, Horiuchi, K., Horiguchi, S., and Suekane, M., Osaka Cy. Med. J., 1959, 5, 41. Gorsuch, T. T., Analyst, 1959, 84, 135. Pijk, J ., Hoste, J., and Gillis, J ,, “International Symposium on Microchemistry, Birmingham, 1958,” Soluene-350 Technical Bulletin, Packard Instrument Company Ltd., Caversham, Berks, 1974. Jackson, A. J., Michael, L. M., and Schumacher, H. J., Analyt. Chem., 1972, 44, 1064. Keplan, P. D., Blackstone, M., and Richdale, N., Archs Envir. Hlth, 1973, 27, 387. Barlow, P. J., and Khera, A. K., Atom. Absorption Newsl., 1975, 14, 149. Hoffman, L., and Davies, J., Enviv. Res., 1974, 8, 64. G. J., Archs. En&. Hlth, 1973, 27, 151. Pergamon Press, Oxford, 1960.

ISSN:0306-1396    

DOI:10.1039/AD9761300326

出版商:RSC    

年代:1976

数据来源: RSC

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342 DETECTION LIMITS AND TRACE ANALYSIS Proc. Analyt. Div. Chewz. SOC. Detection Limits and Trace Analysis The following are summaries of three of the papers presented at a Joint Meeting of the Atomic Spectroscopy Group with the Modern Methods of Analysis Group of the Sheffield Metallurgical and Engineering Society and the Spectroscopy Group of the Institute of Physics held on April 22nd and 23rd, 1976.Monitoring Residual Elements in Steels by Atomic-absorption Spectroscopy M. S. Taylor Firth Brown Ltd., Atlas Wovks, P.O. Box 114, Shefield, S4 7US The stature and significance of “residual elements” present in steels and related alloys con- tinue to grow with increasing knowledge of their individual and collective effects upon the ultimate performance of metallurgical products under commercial conditions.Where materials have to operate satisfactorily in high-duty applications, be it either in a hostile environment, or under extremes of temperature and stress, there are valid metallurgical reasons for controlling both the nature and concentration of certain elements within very close tolerances. It is in this area that atomic-absorption spectroscopy has proved to be particularly valuable.In our laboratories, this technique is used extensively for both routine and research purposes to monitor a range of elements at residual concentrations, which are not otherwise readily evaluated by the more conventional quality control processes. These elements include calcium, magnesium, zinc, lead, bismuth, silver and antimony.In addition to these elements, but for rather different reasons, nickel has now also become of interest. Optimum instrumental parameters used to determine all of these elements are given in Table I. TABLE I OPTIMUM INSTRUMENTAL PARAMETERS Element Parameter Wavelength/nm Slit width/pm Lamp currentlmh Observation height/mm Fuel Support gas Ag Bi Ca Mg Ni Pb Sb 328.1 223.1 422.7 285.2 352.5 217.0 217.6 50 100 100 50 50 200 100 4 8 7 5 5 5 8 5 7 5 5 4 7 10 CZHZ CZH, CzH2 CZH, CzH2 CZH, CzH2 Air Air NZO Air Air Air Air 7 Zn 213.8 100 6 7 Natural gas Air Calcium, Magnesium, Zinc and Nickel These elements are determined by using a sample solution loading of 1% m/V.Calcium and magnesium are determined together in 5% V/V hydrochloric acid containing 0.2% m/V ofNovember, 1976 DETECTION LIMITS AND TRACE ANALYSIS 343 EDTA, disodium salt, as a spectroscopic buffer.With calcium, this component acts as an ionisation buffer in the nitrous oxide - acetylene flame. Zinc is determined in 5% V/V nitric acid and, with the exception of a small matrix effect in the presence of iron, appears to be free from inter-element effects. With nickel, increasing interest in the control of environmental pollution could, in the near future, result in a severe restriction or indeed a total ban upon the use and discharge of cyanide wastes into drainage systems, in much the same way as currently exists in other Common Market countries. This situation would, of course, preclude the use of the British Standard procedure involving cyanometric titration.Atomic-absorption spectroscopy offers an alternative method that is both simple and rapid and produces results of a high calibre. Lead, Bismuth, Silver and Antimony If we consider the location of these elements in the Periodic Table in relation to their co-ordinating affinities with other ligand atoms, they are all closely grouped, showing moderate to strong Class B acceptor character.This character predicts the formation of well defined anionic iodo species, which can be extracted from various acidic media into non-polar solvents as ion-association pairs. Elements in the first, and to a lesser extent second and third, Transition Series, which to- gether comprise the major matrix components of most steels and high-duty alloys, all show a predominantly Class A acceptor character.This feature imparts an invaluable degree of selectivity into the metal - iodide system as a whole and, with the exception of iron, which has to be reduced to the divalent state, no inter- ference occurs from alloying concentrations of manganese, chromium, nickel, cobalt, titanium, aluminium, molybdenum, vanadium, tungsten or niobium. Conditions for solvent extraction are given in Table 11.These elements are determined following solvent extraction. Element TABLE 11 SOLUTION CONDITIONS FOR SOLVENT EXTRACTION Solvent phase : isobutyl methyl ketone. Hydrochloric Potassium Ascorbic acid/M iodideliu acid/M Antimony Silver 0.6 0.75 0.1 2.3 0.75 0.2 1.2 0.75 0.2 Under the conditions in Table I1 with the volume of the aqueous phase controlled at 27.5 nil and that of the solvent phase at 5.0 ml, we obtain an increase in signal response approximating to 30 times that obtained for a 1% m/V solution of steel, with an extraction efficiency in excess of 95%. The analytical precisions attainable by these extraction procedures are considered to be good, being of the order of 0.1 p.p.m.for lead and bismuth in the range 0.2-50 p.p.m., 0.05 p.p.ni.for silver contents between 0.1 and 2.0 p.p.m. and approxiniately 1.0 p.p.m. for antimony in the range 2.0-100 p.p.rn. Analysis of Hazardous Industrial Atmospheres H. M. Jackson Health and Safety Executive, Occupational Hygiene Labovatovy, 403-405 Edgwave Road, London, N . W.2 Nowadays, the commonest means of absorption of hazardous material into the body at work- places is by inhalation, and the Occupational Hygiene Laboratory is called upon to assist HM Factory Inspectors in the determination of such material in industrial atmospheres.Levels of airborne contaminants that are considered acceptable are published as threshold limit values (TLVs) and form the standard against which conditions are assessed. About 30 metals (and their compounds) have assigned TLVs; as well as the more renowned toxic metals such as lead, arsenic, mercury and cadmium, they include several (e.g., manganese, vanadium and zinc)344 SINGLE-PARTICLE CHARACTERISTICS R o c .Analyt. Div. Chew. SOC. considered to be undesirable in the form of fume such as may occur, often in combination, in foundaries or during welding.The air in workplaces is sampled by pumping through a mem- brane filter, the pump and filter holder being attached to the operator’s clothing. Limitations of the air volume sampled mean that the amount of material collected may vary from below 1 pg to about 1 mg. In most instances, the material collected may be taken into a small volume of solution and analysed by atomic-absorption spectroscopy ; there is normally sufficient analyte for aspiration into a flame to be used.Atomic-absorption spectroscopy is one of the techniques used in a mobile laboratory, to provide on-the-spot results. In other instances, where problems of sensitivity and solubility arise, d.c. arc emission spectrography has been used ; in particular, a technique has been devised for beryllium, whose low TLV calls for analysis down to the nanogram level.As the sample is in the form of a thin, flat deposit, it is also in an ideal state for X-ray fluorescence trace analysis; the advantage here is that no prior sample treatment is needed, and it remains available for repeated or alternative analysis. Using a wavelength-dispersive spectrometer, detection limits of 1 pg or lower are possible for most hazardous metals.A problem lies in the preparation of suitable standards for calibration; the most successful method found to date is to transfer aliquots of a suitable freshly prepared suspension of a metal compound. Using such standards, results from X-ray fluorescence correlate well with those from atomic-absorption spectroscopy in the range from the detection limit up to several hundred micrograms. Legal Requirements for Analysis of the Environment D.G. Swinburn Steel Castings Reseavch and Tvade Associatiovz, 5 East Bank Road, Shefield, S2 3PT A picture was presented of the way that legislation will influence the requirements for analyti- cal work in various fields, both now and particularly in the future. The influence on the UK of the EEC and the American Occupational Safety and Health Administration was discussed and the way in which they are related to this country was considered. The Health and Safety at Work Act 1974 was presented, showing the administrative set-up, and how the Health and Safety Executive is responsible for the enforcement of whatever regulations come from the EEC. I t was pointed out that the most dangerous route by which toxic substances enter the body is by inhalation, and two examples were given to illustrate the problem and the related legislation. Both examples dealt with threshold limit values and their interpretation , one an old problem, that of airborne silica dust, and the other a newer problem, that of vinyl chloride. The Control of Pollution Act 1974 was also mentioned.

ISSN:0306-1396    

DOI:10.1039/AD9761300342

出版商:RSC    

年代:1976

数据来源: RSC

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344 SINGLE-PARTICLE CHARACTERISTICS R o c . Analyt. Div. Chew. SOC. Single-particle Characteristics The following is a summary of one of the papers presented at a Meeting of the Particle Size Analysis Group held on April lst, 1976. Single-particle Characterisation by Optical Microscopy and Associated Tech n iq ues John Mccormack, J. E. C. Harris and H. J. Scullion Materials Quality Assurance Directorate, Ministry of Defence, Puviton, Somerset, T A 7 SAD In ascertaining pertinent properties of single particles, we consider two extreme positions : (a) where the characteristic in which one is interested is displayed throughout the whole particulate population; and (b) where one is essentially interested in only a few, probably atypical, particles, e.g., abrasive particles in lubricant graphite.In situation (a), one may perhaps deduce the relevant characteristic of the single particle from the bulk property. In situation (b), one may have to isolate the particle(s) one is inter- Crown Copyright.November, 1976 SINGLE-PARTICLE CHARACTERISTICS 345 ested in and perhaps this may be done simply by picking them out under the microscope, i.e., by “pasteurisation,”l so called because of the separation of tartaric acid crystals via recogni- tion of the hemihedral facets.The possible characteristics of interest may seem innumerable : size, shape, aggregation, agglomeration,2 inclusion^,^ hydrati~n,~ roughness, surface texture or ~ o a t i n g , ~ brittleness, sharpness6 and whether the particles are of a metastable, pyrophoric, p~lymorphic,~ etc., nature; the list is endless.Initial Microscopy Considering situation (a), to obtain some ideaof shapeonecanstart by examining the particu- late matter under a zoom microscope and conveniently quantifying the shape (and size), at least in a two-dimensional sense, by using say the Timbrel1 Shearicon (with which various amounts of image shear can be automatically pre-set) in conjunction with the microscope.At the other extreme of (b), the unique atypical particle can be placed at the centre of the glass sphere on a universal stages where it can be orientated in all directions for both orthoscopic and conoscopic observation and measurement. Correlation Returning to situation (a), except for the degenerate case of monodisperse spheroids one expects different types of size or surface measurements to yield different data and the interrelation of these data can often be interpreted in terms of shape.For example, at the simplest level, data from sieving through circular holes and through slots will give different results for flaky particles and similar results for “equant” granules. At a more soPhisticated level.one can relate sDecific surface area f K ) bv Knudsen flow permeametryg to’ the gas adsorption specific surfaci area (G) by a parametkr 8 = (G - K)/K (see Table I). TABLE I SPECIFIC SURFACE AREAS (mm2 mm-3) OF SIX SAMPLES (A-F) OF IRON POWDERS Measurement A B C D E F G 1760 5300 1900 5500 5800 18700 K 1690 5400 1700 3700 2400 3800 e 0.0 0.0 0.1 0.5 1.4 3.9 On the G data alone one might have classed B and D together and regarded these as distinct from A.Yet A and B are spherical particles differing only in size, whereas D is a sponge-like particle. Increasing values of 8 indicate increasing assessible internal surface, a diagnosis which was in accordance with technological behaviour, and was confirmed by electron micros- copy. Perhaps in appropriate circumstances one might even use a parameter 4 = (K - V ) / V , where V is the viscous permeametric specific surface area, to diagnose surface roughness.Hence one deduces individual particle character from bulk behaviour. “Pasteurisation”1 In situation (b), we can conduct our “pasteurisation” based on shape, habit, colour, nature of fracture, etc. We can use reflected or transmitted illumination or perhaps phase contrast.The last technique transforms a change in the phase of light vibration to the more optically distinguishable amplitude change and can be of value for very thin particles, e g . , tiny asbestos fibres, but its main use is in biology, where use of a wide range of refractive index “oils” may not be appropriate. However, we propose to ignore biologically organised particles such as spores and pollens, and to consider transparent particles of crystals, glasses, resins, plastics, etc., and to ask how we can pick out the atypical without reference to external morphology. If the particles are anisotropic, i.e., if the refractive index (R) pertinent to any light ray passing through the particle is dependent on both direction of the ray and its direction of vibration, then the relevant techniques of classical petrology* are available.If the particles are isotropic (perhaps glass or plastics), i.e., have only one R, one can use the technique of focal plane screening (“dispersion staining”), which utilises the fact that mounted in liquid of “matching” R, the R really only matches a t one wavelength (say the sodium D line).Then, if346 SINGLE-PARTICLE CHARACTERISTICS Proc. Analyt. Div. Cheun. Soc. one blocks say the centre of the back focal plane of the microscope, the particles are illuminated by light from extremes of the spectrum and under such conditions very minor optical differences become apparent.* This technique can be of distinct value in forensic work on, say, glass fragments. Cargille oils are available for this work and we have also used blends of poly- chlorinated biphenyls5 (toxic hazard)1° and, for photomicrography, trans-cinnamaldehyde - bromobenzene mixtures.Density Density is not only an important parameter in particle sizingll but one finds in general that some of the most useful separation techniques are based on density differences.Thus, for the final separation of a few atypical particles a micro-density separation column12 can be useful. The column density (D) varies from that of the “heavy” component (Dh) (say bromoform, 2 892 kg m-3, or diiodomethane, 3 330 kg m-3) to that of a light paraffin (Dz). These values permit a good range of density (AD = Dh - Q) and of refractive index (AR). The con- tents of the column can be issued dropwise, as from a burette tip, and the density of the par- ticle (D,) is the same as that of the drop of fluid accompanying it.The refractive index of the latter is measured, and D, is given by the equation where d is the difference between the mean density of the two components and the density of the mixture that has the mean refractive index. Thus density often facilitates the isolation of foreign particles, helps in their identification, and can afford a product more suitable for examination by X-ray diffraction.Also, many particle characteristics correlate with density : hydration, solvation, polymorphic nature, inclusions and even hardness. For example, from Table I1 we note that in a survey of over 300 minerals there are few light hard particles.TABLE I1 INCIDENCE OF MINERALS IN DIFFERENT HARDNESS/DENSITY CLASSES Hardness (Moh scale) T-----A--- 7 Density/kg m-3 1 2 3 4 5 > 5 1000-2 000 3 1 1 1 1 2 000-4 000 1 22 33 25 25 82 >4 000 4 14 31 11 17 34 Aggregation Speaking of particle “clumping” is rendered difficult because the British Standard13 defini- tions of aggregate and agglomerate seem to contradict those of other worlier~.~J~ The phenomenon can be investigated by subjecting a sample of the powder to treatment relevant to its subsequent technological use.The treatment could be ultrasonics or spatulation, and then “before” and “after” samples would be compared, e.g., by Coulter counting.2 Microscopical examination between crossed polars is useful for clumped crystalline particles.A common extinction direction throughout a cluster is indicative of moderately strong ad- hesion and effectively the agglomerate has become a single crystal. Differing extinction directions in a cluster indicate, in general, less stable association. Inclusions3J5 Early in the development of a crystal, face centres may grow faster than face edges, but above a critical size the rates may be reversed.Cavities then appear at face centres and may heal over eventually to yield inclusions. The microscopist may be faced with inclusions of gas or liquid or both. In bulk they can be examined mounted in a suitable liquid (to match t’rclr mean R16J7) between glass plates and against a dark background. The opacity is, rt’kris paribus, greater for gas than liquid inclusions, and greater still for two-phase inrhs’ons. Similarly, the number rather than the total volume of inclusions is more significant in donating opacity.Another technique is to introduce the crystals into a virtually sat nrated soiution, then to raise the temperature and observe the behaviour. Eventually, inc’usims that contain gas yield bubbles that rise to the surface.Under the transmitted-light ni:(--os:ope (for a givenNovember, 1976 SINGLE-PARTICLE CHARACTERISTICS 347 depth of interface), the most distinct or darkest boundaries are found between a gas and a condensed phase and this effect may help one to decide on the nature of an inclusion. When the inclusions contain mother liquor, the particles may in the long term clump owing to seep- age, and in essence it may be that the product cannot be effectively dried if one is considering an industrial rather than a galactic time scale.In this connection we have encountered a paradoxical phenomenon when the drier of two particulate inputs to a mild comminution process produced the wetter of the two outputs. Investigation disclosed two types of inclusion in the particulate.The former were small peripheral inclusions, which dried only with diffi- culty and which occurred predominantly in the drier input. The wetter input, which would not dry (pre-comminution) until the temperature of a polymorphic change (>200 “C) was reached, consisted of crystals with large centrally located inclusions. In the comminution process, these large inclusions lay along the preferential routes of fracture and hence lost their water more readily.The loss of water from the inclusions at the polymorphic change can be observed by mount- ing the crystals in a viscous fluid such as polyisobutene, raising the temperature on a microscope hot-stage and observing the resultant stream of bubbles passing through the mountant. Similar procedures are, of course, appropriate for identifying solvates or hydrates.Identification Separated atypical particles can be non-destructively identified by various techniques. Dispersion staining is, despite the simplistic previous mention, not limited1* to isotropic matter and X-ray diffraction is most valuable. If a reference compound is lacking, the PDC and plotter will draw the X-ray powder pattern from the literature data and compare it with the pattern obtained on the particle. Alternatively, we can use polarisation microscopys and, even if we do not have the technique and know-how of the petrologist, we can in certain areas design tests based on “go - no-go” tests, provided the question we want answered is “is it X or Y?” rather than “what is it?” Transparent glasses or cubic crystals can be matched in refractive index by a viscous mountant and it should also be noted that they are then rtot visible between crossed nicols.With crystals of other systems, if the refractive indices are such that w - E -+ 0 or y - a +- 0, then we have a low birefringence or pseudo-cubic material. The crystals can be matched virtually in R but aye visible between crossed nicols. Cubic or pseudo-cubic materials would occur with equidimensional, ball-like or tetrahedral molecules, e.g., adamantane, pentaery- thritol tetranitrate or hexamine in the organic field and certain crystals where tetrahedral anions of the XU, type (BF,, ClO,, etc.) dominate, e.g., K2S04 or where the molecules [e.g., the rod-like CO,, or planar NO, in Ba(NO,),] are arranged in compensation symmetrically with respect to the trigonal axes of a cube.As the thermal motion of atoms increases, there is also a trend towards isometric symmetry. For example, above 185 “C pentaerythritol becomes cubic and invisible between crossed nicols ann on lowering the temperature becomes visible again, and hence the solid - solid phase change can be used instead of a melting-point for identification. Similarly, above 125 “C ammonium nitrate is cubic.With a little more sophistication, one can design “go - no-go” tests for uniaxial crystals and pseudo-uniaxial crystals with a m p refractive indices (positive birefringence) and y .w p (negative birefringence). The former would include parallel rod molecules (e.g., alkanes) or plate molecules parallel only to a direction.The latter would include parallel plate anions, (e.g., NO, in NaNO,) or rod anions lying non-parallel but in parallel planes (e.g., KN,). In conclusion, it is worth mentioning that the most useful sources of background information both on techniques and on individual particles are the books by McCrone and Dellyl and Hartshorne and Stuart.8 References 1.2. 3. 4. 5. McCrone, W. C., and Delly, J. G., “The Particle Atlas,” Second Edition, Ann Arbor Science Publishers Palik, E. S., Powder Technol., 1976, 13, 9. Batten, J., J . Appl. Chew. Biotechnol., 1971, 21, 163. Kuhnert-Brandstatter, M., and Grimas, H., Mikvochiun. Acta, 1968, 115. McCormack, J., Harris, J. E. C., and Scullion, H. J., Powder Techwol., 1973, 7, 281.Ann Arbor, 1973.348 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. CORRESPONDENCE Proc. Ana1y.t. Div. Chem. SOC. Scullion, H. J., Harris, J . E. C., and McCormack, J., in Burt, M. W. G., Editov, “Proceedings of Collo- quium on Applications of Particle Size Analysis to Environmental Pollution,” Society for Analytical Chemistry, London, 1974, p. 30. Clements, J . A., PYOG. Analyt. Div. Chem. Soc., 1976, 13, 21. Hartshorne, N. H., and Stuart, A., “Crystals and the Polarising Microscope,” Fourth Edition, Edward Orr, C., Jr., Analyt. Chem., 1967, 39, 834. Envivon. Sci. Technol., 1976, 10, 122. Burt, M. W. G., Fewtrell, C. A., and Wharton, R. A., Powdev Technol., 1973, 8, 223. McCrone, W. C., and Hudson, W., J . Fovens. Sci., 1969, 14, 370. British Standard BS 2955: 1958. Irani, R. R., and Callis, C. F., “Particle Size : Measurement Interpretation and Application,” John Wiley, New York, 1963. Deicha, G., “Lacunes des Cristeaux et leurs Inclusions Fluides,” Masson, Paris, 1955. McCormack, J., RIcCormack, J., and Scullion, H. J., C.I. Technical Paper No. 348, Materials Quality Assurance Directorate, Ministry of Defence, 1963. Powers, H. E., Sugar Technol. Rev., 1969170, 1, 739. McCrone, W. C., Micvoscope, 1975, 23, 213. Arnold, London, 1970.

ISSN:0306-1396    

DOI:10.1039/AD9761300344

出版商:RSC    

年代:1976

数据来源: RSC

摘要:

348 CORRESPONDENCE Proc. Ana1y.t. Div. Chem. SOC. Correspondence Correspondence is accepted on all matters of interest to analytical chemists. Letters should be addressed to the Editor, Proceedings of the Analytical Division, The Chemical Society, Burlington House, London, W1 V OBN. Review of “Spectrophotometric Determination of Elements” Sir, Having been extensively involved in the preparation of the English translation of Marczenko’s book “Spectrophotometric Deter- mination of Elements,” we were rather dismayed by Dr.W. T. Elwell’s review of it in the Septem- ber issue of The Analyst (1976, 101, 759). We were also rather puzzled. He seems to feel that the book should be extensively pruned, but complains because cer- tain topics are not dealt with at length (though he omits to state that they are sufficiently well documented for the reader to obtain ample further information from the literature).He thinks “much of the information is likely to be generally well known . . . and easily available already,” but that “about one third of the references are likely to be in a language other than English,” and he is “not sure that those which are in English are the best available.” Presumably he is reviewing the book as an expert in the field, and if he isn’t sure even about the literature in English it seems to us unlikely that the information will be well known to the general reader, and perhaps Dr.Elwell ought to be grateful for having the world literature not only surveyed but also collated, especially that from the East.Incidentally, if he had inspected the references thoroughly he would have found that the publisher’s blurb is wrong and that the references go up to 1975, not 1973. He might also have mentioned that apart from review papers there has not been a systematic compila- tion on the topic since 1958, and that this book fills the gap, most of the references being post- 1958. Further, the procedures recommended have almost all been tested in the author’s laboratory and found to work.We would not normally object to a certain amount of adverse comment by a reviewer where the criticism seemed justified, but in this case the review seems to consist mainly of un- favourable comment with little attempt to inform the reader of the useful features of the book, and to us this seems a disservice to the reader, the author, the publisher, and to the reviewer himself.Yours faithfully, R. A. Chalmers C. G. Ramsay Depavtment of Chemistvy, Univevsity of A bevdeeaz, Meston Walk, Old Abevdeeu~, AB9 2UENovembev, 1976 NOMINATIONS FOR THE AD COUNCIL Nominations for the AD Council Mcmbers of the CS Analytical Division are re- minded that nominations for Council should be received by the Honorary Secretary of the AD, Chemical Society, Uurlington House, London, W 1V ORN, not later than November 30th, 1976. There arc six vacancies to be filled a t the Annual General Meeting to be hcld on March 17th, 1977. Nominations should be signed by ten other members of the Division and be accompanied by a declaration signed by thc nominee that he is willing to serve if elected. 349

ISSN:0306-1396    

DOI:10.1039/AD9761300348

出版商:RSC    

年代:1976

数据来源: RSC

摘要:

Novembev, 1976 NOMINATIONS FOR THE AD COUNCIL 349 Publications Received High- Speed Liquid Chromatography. Peter M. Rajcsanyi and Elisabeth Rajcsanyi. Chromatogvaphic Science Sevies, Volume 6. Pp. x + 203. New York and Basle: Marcel Ilckker, Inc. 1975. Price SwFr56. New Developments in Separation Methods. Edited by Eli Grushka. Pp. x + 246. New York and Basle: Marcel Dekker, Inc. 1976. Price SwFr85.Modern Fluorescence Spectroscopy. Vol- ume 2. Edited by E. L. Wehry. Modevn Analytical Chevl.2istvy. Pp. xx + 459. New York and London : Plenum Prcss. 1976. Price $35.40. Chemical Derivatization in Liquid Chrom- ato gr aphy . J . F. Lawrence and K. W. Frei. Jouvmal of Chvomatogva9hy Libvavy, Volume 7. Pp. viii + 213. Amsterdam, Oxford and Xcw York: Elsevier Scientific Publishing Company.1976. Price Dfl90; $34.75. Instrumental Liquid Chromatography. A Practical Manual on High-performance Liquid Chromatographic Methods. N. A. Parris. Jouvnal of Chvomatogvnphy Libvavy, Volume 5. Pp. x + 329. Amsterdam, Oxford and New York: Elscvier Scientific Publishing Company. 1976. Price Dfl100; $38.50. Selected Annual Reviews of the Analytical Sciences. Volume 4. Edited by I,. S. Bark. Pp. vi f- 73. London: Tlic Chemical Society. 1976. Price L9.50. Membrane Separation Processes. Edited by Patrick Meares. Pp. x + 600. Amsterdam, Oxford and New York: Elsevier Scientific Publishing Company. 1976. Price Dfl25O; $96.25. Examination and Analysis of Starch and Starch Products. Edited by J . A. Radley. Pp. viii + 220. London : Applied Science Publishers Ltd., 1976. Price Ll5.

ISSN:0306-1396    

DOI:10.1039/AD976130349c

出版商:RSC    

年代:1976

数据来源: RSC