摘要:

of the Society for Analytical Chemistry CONTENTS Reports of Meetings . . . . 103 Thermal Analysis Group . . 104 “New light Sources in Spectro- “Thin-layer Chromatography ” I I3 Papers accepted for The Analyst I16 scopy” . . . . . . . . I05 Membership changes . . .. 117 Publications Received . . . . 118 Notices . . . . inside Back cover Proc. SOC. Anal. Chem. Vol. 2 No. 7 Pages 103-118 Forthcoming Meeting Bock cover July 1965 Vol. 2 No. 7 July 1965 PROCEEDINGS THE SOCIETY FOR ANALYTICAL CHEMISTRY OF President of the Society A. A. Smales O.B.E. Hon. Secretgry of the Society S. A. Price Hon. Treasurer of the Society D. T. Lewis C.B. Hon. Assistant Secretaries of the Society B. S. Cooper; D. W. Wilson Secretary Miss P. E. Hutchinson 14 BELGRAVE SQUARE LONDON S.W.i Telephone BELgravia 3258 Editor 1.B. A t t r i l l Proceedings i s published by The Society for Analytical Chemistry and distributed to members and all subscribers to The Analyst without charge Single copies may be obtained direct from the Secretary The Society for Analytical Chemistry at the above address (NOT through Trade Agents) price 2s. 6d. post free. Remittances payable to “Society for Analytical Chemistry” MUST accompany orders Methods for the Analysis of y Detergent (NSD) Products by G. F. LONGMAN B.Sc. F.R.I.C. & J. HILTON B.Sc. A.R.I.C. (Unilever Research Laboratory Port Sunlight) Society for Analytical Chemistry Monograph No. I -+- This Monograph describes in detail the methods of analysis developed in Unilever’s Laboratories for the identification and assay of components of NSD Products. -+- Available ONLY from The Editor “The Analyst,” 14 Belgrave Square London S.W. I (Not through Trade Agents) Price 15s. o r U.S. $2.08 Post free l A remittance made out to “Society for Analytical Chemistry” should accompany every order. I Members of the Society may purchase copies at the special price of Ss. post free.

ISSN:0037-9697    

DOI:10.1039/SA96502FX023

出版商:RSC    

年代:1965

数据来源: RSC

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THE SOCIETY FOR ANALYTICAL CHEMISTRY Notices ROYAL INSTITUTE OF CHEMISTRY SUMMER SCHOOL IN SPECTROSCOPY 1966 THE 1966 Summer School will be held in the School of Pharmacy Brunswick Square London W.C.l and at the adjacent Royal Free Hospital Medical School from September 4th to loth 1966 and will consist of comprehensive courses on Organic Spectroscopy (organised by Dr. D. W. Mathieson Reader in Pharmaceutical Chemistry School of Pharmacy London) and Inorganic Spectroscopy (organised by Professor D. J . Millen University College London). THE 1 7 ~ ~ PITTSBURGH CONFERENCE PITTSBURGH PENNSYLVANIA FEBRUARY 21ST TO 25TH 1966 THE 17th Pittsburgh Conference on Analytical Chemistry and Applied Spectroscopy Inc. will be held a t the Penn-Sheraton Hotel in Pittsburgh Pennsylvania U.S.A. from February 21st to 25th 1966.Approximately 250 papers on all aspects of analytical chemistry and spectroscopy will be presented. Symposia proposed for this Conference are- 1. 2 . 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. Combined Gas Chromatographic - Mass Spectrometric Techniques. Fast Reaction Kinetics. Electron Spin Resonance. Electron Microprobe. Process Control X-Kay Spectrometry. Atomic Absorption. Coblentz Society Symposium. Gas Chromatography Utilizing P yrol y t ic Techniques. NMR Spectra of Polymeric Materials. Nuclear Magnetic Double Resonance. Analytical Instrumentation in the Space Programme. New Instrumentation Techniques. Original papers on all phases of analytical chemistry and spectroscopy are invited. A brief abstract (150 words) of each paper will be printed in the programme. Three copies of this abstract with a letter listing the names of the authors the laboratory in which the work was done and the current addresses of the authors should be addressed to Dr.Richard E. Hein Programme Chairman The 17th Pittsburgh Conference Inc. Mellon Institute 4400 Fifth ,4venue Pittsbrugh Pennsylvania 15213 U.S.A. The final date for receipt of abstracts is October lst 1965. INTERNATIONAL UNION OF PURE AND APPLIED CHEMISTRY IUPAC WHAT IT IS-WHAT IT DOES-HOW IT WORKS-HOW IT IS FINANCED THIS pamphlet describes the aims and organisation of IUPAC the means wheregy the aims are fulfilled and the finances of IUPAC. Also included are a list of “members” of IUPAC (the National Adhering Organisations) and an organisation chart. BRITISH STANDARDS INSTITUTION DRAFT SPECIFICATIONS A FEW copies of the following draft specifications issued for comment only are available to members of the Society and can be obtained from the Secretary The Society for Analytical Chemistry 14 Gelgrave Square London S.W.1.Draft Specification prepared by Sub-Committee SFE/17/7-Physical Methods of Gas Part I-Infra-red and Analysis. Ult r a-violet Met hods. D 65/5832-Draft R.S. Physical Methods of Gas Analysis. THE SOCIETY FOR ANALYTICAL CHEMISTRY Draft Specification prepared by Technical Committee PLC/17-Testing of Plastics. D 65/5926-Draft B.S. Method of Test for Resin Content of Glass-reinforced Laminates Method 107K (Addendum to B.S. 2782). Draft Specification prepared by ISE/18-Sampling and Analysis of Iron and Steel. D 85/6657-Draft B.S. Methods for the Analysis of Iron and Steel.Part . . . . Magnesium in Cast Iron. THE SOCIETY OF COSMETIC CHEMISTS OF GREAT BRITAIN SYMPOSIIJM ON “PHYSICAL aIETHODS,” xOS’EMBER 1 6 ~ ~ AXD 1 7 ~ ~ 1965 A SYBIPOSIUM on “Physical Methods,” organised by the Society of Cosmetic Chemists of Great Britain will be held at the Grand Hotel Bristol on November 16th and l’ith 1965. The scientific programme will include eleven lectures by authors from Great Britain and Germany as follows- “Spectrophotometric methods for the rapid ex-aluation of the inactivation of anti-microbial agents,” (School of Pharmacy Bvistol Collegf of Science aitd “Thin-layer chromatographic techniques in residue analysis,” by J . Thomson -4.H.-W.C. ;1.R.I.C. “Particle size analysis using Coulter counters,” by R. W. Lines B.Sc. (Coulteu Electronics Ltd.Sf. “lnfrared spectroscopy of aqueous detergent solutions,” by h1. -1. Puttnam B.Sc. Ph.D. A.R.I.C. “Spectral slit width and other sources of error in ultraviolet spectrophotometry,” by A. R. Rogers “Rheological studies of new cream bases with the Brookfield spnchroletric viscometer,” by Professor “The analysis of aerosol propellants,” by R. J . Brook L.R.I.C. and B. D. Joyner .I.R.I.C. (Iwpeviul by 31. Brown M.Sc. Ph.D. M.P.S. M.I.Bio1. Technology). Ph.D. Albans). (Colgate-Palmolive Ltd. Salfovd). B.Pharm. B.Sc. Ph.I). F.R.I.C. F.P.S. F. Xeuwald Dr.rer.techn. Snzeltizzg Covpovation Avonwzouth). (Labovatovy of the Govewtnzent Chemist Loitdon). (School 0-f Phavmacy Bvightovz College of Teclznology). (Iitstitute of Phnvmaceutical Chemistry C‘nivevsity of Hamburg). “Fluorescent antibody studies in dermatology,” by N.R. Rowell M.B. M.R.C.P. (Geneva1 Tiz$wi?avy at Leeds). “Preparative gas chromatography,” by G. R. Fitch XSc. A.R.I.C. (Depavtwzent of Chenzistvy aizd “Techniques for assessing the rheological properties of toiletry and cosmetic products,” by P. Sherman “The relation between structure and properties in plastics used in packaging,” by A. Sharples B.Sc. The Symposium periods will be devoted to discussion of these papers which will be circulated beforehand to registered participants. There will also be a display o€ apparatus and ecpip- ment at the School of Pharmacy Bristol College of Science and Technology. The registration fee will be 6 guineas (3 guineas to members of societies affiliated to the International Federation of Societies of Cosmetic Chemists). Registration forms together with full details can be obtained from the General Secretary Mrs. D. Rlott 18 Warner Close Harlington Middlesex. Biology Bristol College of Scirizce and Techizology). M.Sc. F.R.I.C. (Uizilevev Reseavch Labovatovy Welwym). Ph.D. (Avthuv D. Little Reseavch Imtitute Incevesk). Forthcoming Meeting July IVednesday 28th SPECIAL TECHNIQUES GROUP joivztly with the Polarographic Society. 1,oiVI)oK “The Application of the ‘Load-line’ Method t o the Interpretation of the Effect of Rejistance in Electrochemical Systems” by K. G. Powell B.Sc. and G. F. Reynolds N.Sc, Ph.D. F.R.I.C. R1.R.S.H. “Some Considerations in the Construction of a Cathode-ray Polarograph,” by J . 157. Howden H.Sc. Meeting Room of the Chemical Society Burlington House Piccadilly London 5T.1 7 p.m.

ISSN:0037-9697    

DOI:10.1039/SA96502BX025

出版商:RSC    

年代:1965

数据来源: RSC

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July 1965 Vol. 2. No. 7 Reports of Meetings NORTH OF ENGLAND SECTION THE twenty-eighth Summer Meeting of the Section was held at the Prince of Wales Hotel Scarborough from Friday May 28th to Monday May 31st 1965. The Chairman of the Section Mr. J. F. Clark MSc. A.R.C.S. D.I.C. F.R.I.C. F.R.S.H. presided over an Ordinary Meeting at 10.30 a.m. on Saturday May 29th a t which A. S. Beidas B.Sc. F.R.I.C. gave a lecture on “The Examination of Cosmetics.” This was followed by a demonstration on Cosmetics by courtesy of Boots Pure Drug Co. Ltd. MICROCHEMICAL METHODS GROUP THE fiftieth London Discussion Meeting of the Group was held at 6.30 p.m. on Wednesday May 26th 1965 at “The Feathers,” Tudor Street London E.C.4. The Chair was taken by the Chairman of the Croup Mr. R. Goulden F.R.I.C. The meeting took the form of a Review Meeting for topics discussed during the 1964-65 session.BIOLOGICAL METHODS GROUP THE Summer Meeting of the Group was held on Thursday June loth 1965 when by kind permission of the Directors a visit was paid to the Laboratories of Smith & Nephew Research Ltd. Harlow Essex. In the morning the Chair was taken by the Chairman of the Group Dr. M. W. Parkes B.Sc. and the following papers were presented and discussed “Network Analysis Applied to Pharmaceutical Research,” by D. J. Drain ; “Sterilisation of Medical Products,” by K. Tattersall. During the afternoon a tour of the laboratories was made. 103 104 REPORTS OF MEETIXGS [Proc. Soc. Anal. Chem. THERMAL ANALYSIS GROUP THE Inaugural Meeting of the Group was held at 6.30 p.m. on Friday May 28th 1965 in the Neeting Room of the Chemical Society Burlington House London W.l.The meeting was opened by Mr. A. G. Jones B.Sc. F.R.I.C. Vice-president of the Society. The following were confirmed as Officers and Committee Members for the forthcoming year Chairman Dr. R. C. Mackenzie. Vice-Chairman-Dr. J. P. Redfern. Honorary Secretary-Mr. C. J. Keattch John Laing Research & Development Ltd. Manor Way Boreham Wood Herts. Honorary Treasztrer-Dr. A. A. Hodgson. Members of Coinwaittee-Dr. D. Dollimore Mr. J. A. Forrester Dr. W. hlanz Mr. E. P. J. Schilling Pvlr. D. A. Smith and Mr. F. W. Wilburn. Mr. W. Boardman and Dr. T. L. Parkinson were appointed as Honorary Auditors. The Chair was taken by the Chairman of the Group Dr. R. C. Mackenzie F.R.I.C. F.G.S. F.R.S.E. The following papers were presented and discussed “Differential Thermal Analysis and Thermogravimetric Analysis Studies at Salford on Metal Oxy-salts Coals and Polymers,” by D. Dollimore Ph.D. F.R.I.C. J.P.; “Thermal Stability Studies on Polymers,” by W. W. Wright Ph.D. A.R.I.C.; “Thermal Analysis Studies of Phenolic Resin Systems,” by B. L. Treherne B.Sc. ; “Thermal Analysis in the Investigation of Naturally Occurring Inorganic and Organic hlaterials,” by R. D. Mitchell BSc. A.R.I.C.

ISSN:0037-9697    

DOI:10.1039/SA965020103b

出版商:RSC    

年代:1965

数据来源: RSC

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104 REPORTS OF MEETINGS [Proc. SOC. Anal. Chem. Analytical Methods Committee DETERMINATION OF BUTTERFAT IN MILK THE Analytical Methods Committee has been requested to consider a possible approach to the British Standards Institution to suggest an amendment to B.S. 696 (Gerber Method for the Determination of Fat in Milk and Milk Products) allowing the use of Macdonald’s reagent (F. J. Macdonald Analyst 1959 84 287 and 747) as an alternative to sulphuric acid. The Committee has been informed that evidence exists suggesting that use of Macdonald’s reagent in this test is permissible and that results obtained when it is used are in close agreement with those obtained by the method as laid down in B.S. 696. To assist the Committee in deciding whether or not it can comply with the request the views of analysts with experience of the use of both Macdonald’s reagent and sulphuric acid in the Gerber test would be welcome. Communications should be sent to- The Secretary Analytical Methods Committee The Society for Analytical Chemistry 14 Belgrave Square London S.W.l.

ISSN:0037-9697    

DOI:10.1039/SA965020104b

出版商:RSC    

年代:1965

数据来源: RSC

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NEW LIGHT SOURCES I N SPECTROSCOPY 105 New Light Sources in Spectroscopy The following are summaries of the papers presented at the Joint Meeting of the Society organised by the Special Techniques Group and the Spectroscopy Group of the Institute of Physics and the Physical Society held on February 3rd 1965 and reported in the February issue of the Proceedings (p. 17). Analytical Applications of a Hollow-cathode Source BY G. P. MITCHELL AND C. I. HARRIS (Centval Matevials Labovatovy The Mullavd Radio Valve Company Mitchavn Junction Suvvey) MR. MITCHELL said that the hollow-cathode discharge had recently been brought to the notice of analytical chemists firstly through its use as a source in atomic-absorption analysis and secondly as an analytical tool in its own right in which use the authors were primarily interested.The first reported use of the hollow-cathode discharge as a source for investigating spectra had been just before the first World War yet it was not until 1934 that any attempt had been made to use the source as an analytical tool. In 1947 J. R. McNally G. R. Harrison and E. Kowe ( J . O$t. SOC. Amer. 1947 37 93) had published one of the first comprehensive studies of the hollow cathode as a quantitative spectrochemical technique. The papers to date had been mainly concerned with the analysis of refractory materials and the determination of the halogens. The speaker said that he and his co-author had endeavoured to extend the tech- nique to the analysis of solutions and materials of interest to the electronics industry e.g. copper nickel and cadmium sulphide.The work to date had been concerned with the analysis of materials in four broadly based groups- (a) Matrices that were difficult to vaporize by using existing arc techniques e.g. refractory materials. (b) Materials of intermediate volatility. (c) Matrices with a high volatilisation rate. (d) Solutions. The choice of refractory materials fell upon titania and zirconium for which existing chemical methods were either too insensitive or long and tedious. Iron and manganese had been analysed quantitatively and platinum lead potassium and calcium had been detected qualitatively at levels of 10 p.p.m. Copper and nickel had been investigated as being repre- sentative of materials of medium volatility. By using the hollow-cathode technique it was possible to determine elements such as zinc tellurium magnesium and beryllium at the part per million level.Results obtained for different types of nickel sample indicated that the physical state of the sample has less influence on the analytical results than with the con- ventional d.c. arc. Cadmium sulphide had been chosen to represent the extremely volatile materials. It had soon been apparent that owing to the large amounts of cadmium and sulphur vapours liberated the excitation of impurities was impossible ; a similar result had been found in attempts to analyse germania. In order to overcome these difficulties a solution technique had been developed in which a specially designed electrode was used. The elements determined by this technique were tin zinc silver gallium indium copper iron magnesium and lead.By using the solution technique developed for the analysis of cadmium sulphide some 20 elements had been determined in solution and satisfactory graphs obtained over a range of 0.3 to 30 pg. The work was intended to investigate possibilities rather than produce finalised tech- niques and it was the speaker said evident from their results that the hollow cathode had possibilities that were complementary to existing analytical sources. The speaker said that on the credit side it was especially useful for refractory analysis solution analysis and the analysis of some metals. In the field of gases halogens and metalloids their own experience was limited but others working in this field had obtained promising results. In all these instances the source had a higher sensitivity and stability than existing commonly used techniques and could be used not only in emission but also in absorption spectroscopy.106 NEW LIGHT SOURCES IN SPECTROSCOPY [Proc. SOC. Anal. Chew. On the part in the less volatile debit side it seemed that since volatility of the sample played such an important running of the hollow-cathode source analysis of volatile matrices for traces of elements could be difficult. DISCUSSION MR. RAMSDEN asked if the authors had seen the spectrum background on the plate after 5 to 10 minutes’ exposure or had it been still rather invisible; which tellurium line had been used and how far down. He also asked the purpose of exposures for 2 to 3 minutes at several different current levels. Would the speaker confirm the millimicro- gram amounts found; was this in a 100-g sample i.e.1 part in 100 million. Mr. Mitchell replied that in general the background was light even after 5 minutes’ exposure. The purpose of several exposures at different current levels was to obtain the most favourable conditions for the excitation of elements grouped according to their volatility in the hollow cathode. In the analysis of copper for tellurium two tellurium lines had been used 2383-2 and 23857 A. The amounts quotcd in milljrnicrogranis in the paper were absolute amounts present in the hollow cathode. DR. A. C. G. MENZIES commenting on the speaker’s answer to Mr. Ramsden said that it seemed that the limit of detection had not nearly been reached The definition of “limit of detection” involved the standard deviation of the blackening of the plate in the neighbourhood of the line and until the exposure was long enough to give some background one could not apply the definition and the limiting concentration measured by this technique might be much smaller than the speaker had stated.Mr. Mitchell agreed with Dr. Menzies and said that the authors had not attempted to determine the limit of detection in this form and said that it was not suggested that the figures quoted in their own work were in fact limits of detection. MK. R. J. W. POWELL noted that some of the results the authors had obtained with the hollow-cathode source included some for the determination of elements less volatile than the matrix material e.g. tin in cadmium sulphide. He wished to know how the authors overcame the selective distillation that occurred with the source in such instances.He also asked if the authors had found any differences in sensitivity for the same element in different matrixes. In reply Mr. Mitchell said that there was considerable difficulty in determining elements such as tin in cadmium sulphide powder but many of the difficulties could be overcome by using the solution technique as suggested in the paper. In most instances the sensitivity obtainable would depend on thc element sought and the volatility of the matrix. Spectroscopic Applications of Lasers BY T. P. HUGHES (National Physical Labovatovy Teddington Middlesex) MR. HUGHES in his talk covered the use of lasers (a) for analytical sampling and excitation and (b) as sources for Raman spectroscopy. The first included the ruby and neodymium-glass lasers which produced short pulses of very high peak power that with Q-switching techniques could be many megawatts.The second included helium - neon and ionised-argon lasers which provided continuous light at the rela- tively low power of up to a few watts. A 1-MW laser beam focused to a spot of 10Op diameter gave a local power density exceeding 10lo watts per sq. cm. In this beam the surface of any material target would be vaporized in less than a microsecond. With a few joules of laser energy available in a pulse the amount of material removed would be only a few micrograms. Some of this would be heated to a temperature of many thousands of degrees and the spectra of the neutral atom and of several stages of ionization were excited in a small plume of vapour near the target surface (E. Archbold D.W. Harper and T. P. Hughes Brit. J . Appl. Phys. 1964 15 1321). He considered two main groups of lasers. July 19651 NEW LIGHT SOURCES I N SPECTROSCOPY 107 Non-Q-switched lasers had also been used but the excitation was not as strong and several elements had not been detected in one set of experiments (J. Debras-Gukdon and N. Liodec Compt. Rend. 1963,257 3336; Chem. Abstr. 1964,60 7600d). The sample was small and precisely located and any material could be sampled without preparation in less than a microsecond. It could be done in air and at a distance since there was no contact with the sample. The method worked well even on insulating inclusions in metal and the vaporization was not selective Spectrograms taken by Mr. E. Archbold of the National Physical Labora- tory were shown in which some of these advantages were demonstrated.Samples included a rapidly moving object a valve component sealed inside an evacuated glass envelope a transparent liquid surface and various optical glasses. Qualitative analysis was possible for each sample. The sample though small was larger than that used by the electron-microprobe analyser. Lasers were rather expensive perhaps about F2000 for this application and the spectrum obtained was not very satisfactory for quantitative analysis (E. F. Runge R. W. Minck and F. R. Bryan Spectrochim. Acta 1964 20 773). In an endeavour to overcome this last difficulty F. Brech of the Jarrell Ash Company had used the laser only to vaporize the sample and had passed a conventional discharge through the vapour between two nearby electrodes.This technique had been used successfully for qualitative analysis particularly for geological (J. A. Maxwell Chemistry in Canada April 1963 p. 10) and biological studies and gave a much better spectrum than the unaided laser beam but further developments were needed for quantitative work. Even if the laser pulse was strictly reproducible the surface character of the sample affected the result at present. R. E. Honig and J. R. Woolston (A$$& Phys. Letters 1963 2 138) had used a laser for vaporizing samples and had analysed the vapours with a mass spectrometer. Under optimum conditions they had detected impurities at the level by using sample volumes 150 ,u in diameter and 125 p deep. The laser could thus provide reliable qualitative analyses under rather unorthodox conditions.Its special abilities might be particularly useful not only to geologists and biologists but also to forensic scientists archaeologists curators of museums etc. For Raman spectroscopy a monochromatic source was needed with the minimum of background continuum. Since the intensity of a Raman line increased as the fourth power of the excitation frequency short wavelengths were desirable. However as many materials absorbed strongly in the ultraviolet and glass optics were generally used it was best to work at wavelengths longer than about 4000A. The neodymium-glass laser emitted a broad spectrum at 1.06 ,u and therefore was unlikely to be useful. The ruby laser had a narrow line breadth but its output was at 6943 A. €3. P. Stoicheff (“Proceedings of the Xth Collo- quium Spectroscopicum Internationale,” Spartan Books Washington 1963 p.399) had estimated that 50 typical ruby-laser flashes would give results roughly equivalent to those obtained by a 1-second exposure with a Toronto-type mercury lamp; also laser flashes were rather expensive. However the laser beam was very directional and multiple passes through the sample might help considerably. If a single laser pulse was sufficient the exposure would be very short which might be useful but otherwise the laser pulses would have to be spread out often many seconds apart. In this instance the important criterion was the mean output power and here the second category of lasers gas lasers was helpful. A continuously operating helium - neon gas laser would give a very monochromatic output of up to about 100 mW at 6328 A.A 3-joule ruby-laser pulse every 30 seconds gave the same mean power so the two were roughly equivalent. But the helium - neon laser had the advantages of a slightly shorter wavelength and greater directionality and was more nearly monochromatic so unless very short exposure times were needed it was preferable to the ruby laser. It had already been incorporated in one commercial Raman spectrograph. A recent development of considerable interest was the ionised-argon laser which emitted various wavelengths mainly in the blue and green regions with a total continuous output of several watts. The dominant line at high powers was at 5145 A which was expected to be very useful for Raman work. As a sampling technique the method had many advantages. There were however the speaker said some disadvantages.This too seemed a promising approach. 108 NEW LIGHT SOURCES IN SPECTROSCOPY [Proc. SOC. Anal. Chem. DISCUSSION MR. G. P. MITCHELL wanted to know the possibilities of using a lascr as a source for mass-spectrometric purposes in view of the rapid evaporation achieved by its action to which Mr. Hughes replied that Honig and Woolston (idem) had shown this idea worked and he thought it should be developed further. MR. E. J. MILLETT asked if the crater size was correspondingly reduced by focusing the laser beam with a lens of much shorter focal length thereby reducing the image to a spot of much less than 100 p in diameter or if the crater-size limit was set by thermal conduction. Mr. Hughes said the crater size could be reduced by using a lens of much shorter focal length but that pulse shape and energy were also important.Cavities as small as lp in diameter could be produced in thin films but would not provide enough material for analysis. DR. C. A. PARKER asked if the higher harmonic of the intense laser emission in the green region would provide a valuable excitation source in fluorescence spectroscopy and also asked if Mr. Hughes could say what proportion of the higher harmonic (-250 nm) was li@ly to be obtained from the green laser. The speaker replied that the harmonic at 2572 A would be very weak-at a guess of the order of microwatts. One difficulty was that several of the more efficient non-linear optical materials absorbed strongly at this wavelength. DR. A. C. TURNER asked if there was any fundamental reason why lasers could not be used to excite inorganic ions in flames to emit at a different wavelength in a manner similar to conventional Raman spectra.This would be a feasible way of getting round the limitation of scattered light in the atomic-fluorescence method. In reply Mr. Hughes said that there seemed to be no reason but the efficiency of conversion was likely to be rather low. MR. R. G. COOMBES asked if the speaker had had any experience with the helium - neon laser that operated at 3-39 p and if so what beam power was possible and with what laser gas-tube life. Mr. Hughes said that he had not used the helium - neon laser with this transition but that it was not likely to be useful either for sampling or for Raman studies. There should be no difference in the tube life to that of the helium - neon laser operated at 6328 A or 1 .5 ~ ~ which could exceed 1000 hours. Although. it had a very high gain it saturated rather easily. Spectroscopic Sources with Microwave Excitation BY E. B. M. STEERS (Depwtment of Physics The Novthevn Polytechnic Holloway Lo.tzdon N. 7 ) DR. STEERS said that a discharge might be excited in a tube containing gas at low pressure by a high-frequency electric field produced by electrodes outside the tube. Frequently oscillators in the range 10 to 200 Mc/s had been used. Meggers had shown that for a Hg 198 lamp the higher frequency gave greater intensity with longer tube life. Frequencies in the microwave region proved still more efficient especially for small tubes; in one of the few quantitative measurements reported A. T. Forrester R. A. Gudmensen and P.0. Johnson (-1. Opt. SOC. Amer. 1956 46 339) compared intensities per unit area per unit solid angle for a mercury lamp excited at 70 Mc/s and showed that the latter could give ten times the intensity for one-tenth the power. Continuous-wave magnetrons capable of supplying 200 watts at 2450 Mc/s formed a convenient power supply and had been used extensively to excite small discharge tubes to give an intense steady source. The discharge tube might be held above a stub radiator (C. H. Corliss W. R. Bozman and F. 0. Westfall Ibid. 1953,43 398 and F. S. Tompkins and M. Fred Ibid. 1957 49 1089) placed in a resonant cavity (L. Bovey and H. Wise Atomic Energy Research Establishment Refiort R2976 U.K. Atomic Energy Authority 1959) or form part of the inner conductor of a coaxial line (Forrester et al.idem). The stub radiator was an inefficient method since most of the power was radiated. For the other types of exciter some tuning device was necessary for if the load was incorrectly matched the power would be partially reflected and might damage the magnetron. For a July 19651 NEW LIGHT SOURCES IN SPECTROSCOPY 109 typical magnetron of this type the maximum permissible voltage to standing wave ratio was 2; when the tube was running brightly the ratio obtained was usually below 2 but when the tube was being lit much higher values occurred. The risk of damage to the magnetron might be reduced by using a cable with a slight loss but some form of isolator would be preferable. For gases and the more volatile elements a quartz discharge tube about 10 cm long and 1 cm diameter containing the element might be used with possibly an inert gas to start discharge.Such tubes had worked successfully for gaseous elements and for magnesium calcium zinc gallium cadmium indium antimony bismuth mercury thallium lead and barium (M. Zelikoff P. H. Wyckoff L. M. Aschenbrand and R. S. Loomis J . Opt. SOC. Amer. 1952 42 818). In some instances auxiliary heating might be necessary and in others tube life was limited by reactions with the tube wall although this could be reduced by a suitable liner. For less volatile elements a volatile compound usually a halide was used; in this way spectra of aluminium iron nickel copper cerium praseodymium neodymium samarium europium gadolinium terbium dysprosium holmium erbium lanthanum thorium protactinium uranium neptunium plutonium americium and curium had been excited by various workers.For the less volatile halides tube temperatures of 800" to 900" C were required. With the stub radiator extra heating was needed but small tubes (say 3-cm long 6-mm diameter) in a cavity usually attained a suitable temperature without additional heating. A uniform temperature was necessary or the halide sublimed into the cooler portion of the tube and the intensity dropped. The spectrum emitted by a tube containing an inert gas e.g. neon and metallic halide varied with the power and temperature. When the discharge was first initiated with a Tesla coil the spectrum of the inert gas was observed then the molecular and atomic spectra of the halogen and finally the spectra of the metal. At lower temperatures and pressures the spark spectrum predominated and at higher temperatures the arc spectrum was the more intense although the extent of this charge varied with the element concerned.At this stage the spectra of the inert gas and the halogen were usually completely suppressed. The spectral lines emitted were much narrower than those from an arc owing to the lower temperatures and pressures although the intensities were comparable. The line width depended to some extent on the intensity and for cooled mercury tubes interference fringes had been obtained with a path difference of more than 15 cm. Once the "warming-up'" period had passed the discharge would run steadily for periods of some hours. The tubes could be used repeatedly although there was a tendency for iodine to accumulate in tubes containing an iodide and it might be necessary to cool the tube in liquid air before relighting.In view of the high temperatures attained when the tube is running very careful de- gassing of the tube was necessary during its preparation; it was convenient to adopt a pro- cedure similar to that used by Tomkins and Fred (idem) in which the material to be excited was contained in a specimen tube and sublimed ~ F Z vacuo into the discharge tube after this has been de-gassed. The iodide was usually the most convenient halide to use; if this was readily available in a pure form it might be sealed into the specimen tube direct. Many iodides were deli- quescent and hydrolysed and in these instances it was advisable to prepare the iodide in the specimen tube in vacm. A direct reaction between the metal in a powdered form and iodine was sometimes possible; alternatively the oxide might be heated for some hours with alu- minium iodide (prepared by direct reaction) and any remaining aluminium iodide sublimed off at about 300" C before the specimen tube was moved to the discharge tube.Successful tubes had been made containing as little as 0.1 pg of halide (Tompkins and Fred idem) although larger amounts up to a few milligrams usually gave a more satisfactory tube. Microwave excitation was most useful when an intense steady source was required for a long period when only small amounts of material were available or when the substance was toxic or radioactive. The time taken to prepare satisfactory tubes would constitute a serious drawback to their use for spectrochemical analysis although a shortened procedure might be used if a long tube life was not required.Differences in the physical and chemical nature of the sample and differences in sublimation temperatures could seriously alter the composition of a mixture during tube preparation. One possible use that did not suffer from this drawback would be for the determination of the relative abundances of the isotopes of a given element. 110 NEW LIGHT SOURCES IN SPECTROSCOPY [PT~c. SOC. AP~~E. Chew. I~ISCUSSION MR. A. C. TURNER asked if the tubes could be used as sources for analytical purposes by dispensing with the de-gassing step and fitting demountable tubes containing anlytical samples to a flow-through gas system. In reply Dr. Steers said that this might be possible for materials that were readily excited at low temperature although the material might be rapidly and preferentially lost to the discharge.The discharge would tend to spread along the tube and it would not be possible to excite less volatile materials. MR. A. C. MASON asked for an estimate of the time required to prepare sources suitable for isotope analysis and also if fluorides were as suitable for excitation as other halides. Dr. Steers said that for a relatively short tube life a preparation time of perhaps 2 hours would be sufficient if volatile compounds were available. Preparation of an iodide from an oxide might take considerably longer. He had avoided fluorides owing to the handling difficulties involved but they would presumably behave in a similar fashion. In reply to DK. C. A. PARKER who asked if it was possible to excite dilute vapours or gases in an inert gas stream at atmospheric pressure Dr.Steers said that with a 200-watt magnetron the maximum pressure for a discharge in an inert gas was about 50 torr so that this would not be possible. MR. J. A. MOORE wished to know if Dr. Steers had noticed any differences in the rate of metal “clean-up” or wall darkening between pure metal or metal iodide sources when similar vapour prcssures were compared. For metals whose iodides were more volatile than the pure element did sources in which the iodides were used blacken or lose line- emission intensity more readily than those in which the pure metal was used or was the reverse true ? Did the same answer apply to metals whose iodides were less volatile than the elements e.g.alkali metals ? Did increasing the frequency of the energiser lead to greater constriction of the discharge at the same wattage and if so was this the reason for higher brightness at higher frequencies and what was the effect of constriction on metal “clean-up” and wall- darkening properties ? In his reply Dr. Steers said that he had no experience himself with tubes containing a metal but it had been shown that the amount of wall darkening was very much less at these frequencies than at say 20 Mc/s. There were few if any instances in which both metal and halide could be used. In many examples the short life of the tube was due to chemical reaction of either the metal or halide with the walls of the tube; this could be reduced by using a suitable liner. Apart from this a common cause of tube deterioration was the devitrication of the outside wall of the tube.The use of a high frequency permitted the concentration of power into a small volume thus making a small tube advantageous. I t was difficult if not impossible to couple power effectively into a small tube at lower frequencies. Usually the microwave- excited discharge filled the tube but at higher pressures a constriction sometimes occurred. In this instance there was little change of total intensity although the intensity per unit area was greater. MR. G. P. MITCHELL asked what degree of self-absorption was evidenced in the resonance lines and also what sort of long-term stability and life might one expect with such intense sources in comparison with commercially available atomic-absorption lamps.Dr. Steers replied that self-reversal had been observed in resonance lines at very high intensities but was not present at lower powers. E. F. Worden R. G. Gutmacher and J. G. Conway (Applied Optics 1963 2 707) had shown that self-reversal did not occur and self-absorption was minimised with small amounts of sample e.g. 100 pg. The life depended on careful tube preparation but total running time should be well in excess of 100 hours. One thorium tube had been used fairly continuously for 200 hours about 5 years ago and was still working successfully after a gread deal of more intermittent use. The total intensity depended on magnetron power ; the stability of the relative intensities depended on the element. Thus for thorium little change in relative intensities occurred with temperature and very few differences could be obscrved between spectra taken under various conditions.July 19651 NEW LIGHT SOURCES IN SPECTROSCOPY The High-frequency Torch Some Facts Figures and Thoughts BY S. GREENFIELD I. LL. W. JONES C. T. BERRY AND LYNN G. BUNCH (Reseadz Depavttvtzent Albvight G. Wilson (Mfg) Lid. P.O. Box No. 3 Oldbwy Bivmingham) 111 MR. BERRY described a high-frequency plasma torch similar in design to one previously described (Analyst 1964 89 713) but operated with the tail flame vertically upwards. Results were given of the effect of gas flow-rates power input and viewing position in the tail flame on calcium emission at 4226.7 A. Increasing the flow-rate of the gas through the injector caused the emission to rise to a maximum and then fall owing in the initial stages to too little sample reaching the plasma and in the final stages to the sample passing too quickly through the plasma.Increasing the flow-rate of the coolant gave a drop in emission to a steady value as the plasma cooled with insufficient cooling the cell became too hot. A high coolant flow-rate in the plateau region had therefore been preferred. Increasing the gas flow-rate to the plasma initially provided more fuel for the plasma; when the gas flow-rate was in excess the plasma was cooled. This gave rise to an emission intensity that rose to a maximum and then fell. Power increase gave increased emission. As the viewpoint was moved up the tail flame the emission decreased. Other results were given that showed the effect upon emission intensity of changing the injector and plasma gases.It decreased in order argon > nitrogen > air > oxygen when these gases were used in the injector. The injector gas used was therefore always argon although a use for oxygen was seen in that it removed carbon band systems when organic solvents were aspirated. The plasma had been operated with argon helium a 20 per cent. oxygen - 80 per cent. argon mixture and a 20 per cent. nitrogen - 80 per cent. argon mixture. The power available from the generator limited the percentage of diatomic gas that could be mixed with argon. The emission intensity was found to decrease in the order nitrogen - argon > oxygen - argon > helium > argon; the nitrogen - argon plasma gas was now most often used. A plate and diagrams showing the greatly enhanced emission intensity obtained when a nitrogen - argon plasma was used rather than argon alone were shown.It had been concluded that even better results would be obtained if notrogen alone was used as a plasma gas. Some results that had been obtained by using the torch as a source for the Unicam Mark I SP900 flame photometer and the Hilger & Watts large-quartz spectrograph were presented (see Table I). TABLE I RESULTS OBTAINED WITH THE PLASMA TORCH AS A SOURCE This implied the use of bigger generators than the one in present use. Concentration of element found p.p.m. by using- [ Element Aluminium Barium . . Bismuth . . Calcium . . C'olialt . . Copper . . Iron . I Mercury . . Magnesium Manganese Lxacl . . S trontium Tin .. Vanadium Zinc .. ~ a v e l e n g t ~ i A .. . . 3961.5 .. . . 4554.0 ... . 4722.5 . . . . 4226.7 . . . . 3453.5 .. . . 3247.5 .. . . 3719.9 . . . . 2536-5 . . . . 2852.1 .. . . 4030.7 .. . . 4057.8 . . . . 4077.7 .. . . 3415-8 .. . . 3185.3 * . . . 3345-0 air - acetylene flame with Unicam SP900 Mark I spectrophotometer" 100 > 1000 0.02 0.5 0.04 0-5 1000 1 2 4 50 10s > 1000 I high-f requency plasma with Unicarn SP900 Mark I spectrophotometer" 0-5 10 20 0.005 0.2 0.01 0.05 0.5 0.03 0.05 0.8 4 0.1 4 - Hilger & Watts large-quartz spectrograph+ 2 1 0.5 5 1 10 2 1 1 10 I - 5 I - * Flame-photometric figures give 1 per cent. of the minimum concentration found sufficient to give ?Spectrographic figures give the concentration that gives a line density of 2a x background density with $Measured a t a wavelength of 2833.1 A. 3 Measured a t a wavelength of 4379.2k full-scale deflection.an exposure of 3 minutes through a 0.02 mm slit on llford special rapid plates. 112 NEW LIGHT SOURCES IN SPECTROSCOPY [Proc. SOC. Anal. Chem. Mr. Berry pointed out that he and his co-authors were loth to call the figures detection limits since the limit was set by the detection system and not the source. For the flame- photometric figures they would expect better results with the newer Unicam Mark I1 instru- ment and with the spectrograph a slide was shown demonstrating that the low background emission from the plasma torch made exposures of 30 minutes or more feasible. The example of magnesium was cited for which a figure of 2 p.p.m. was obtained after 3 minutes’ exposure (the ratio of line density to background density was 3 to 1); after an exposure of 30 minutes this ratio had increased to 40 to 1.A selection of high-speed cinefilms was shown that demon- strated the 100 c/s growth and decay cycle that the plasma followed when the radio-frequency supply was pulsed at twice the 50 c/s mains frequency. It was explained that this pulsing originated from the full-wave rectifier in the generator circuit and was not apparent if the output from this rectifier was fully smoothed by using a filter circuit. A small filter flame photometer in which transistorised detection and amplification stages were used was des- cribed that made use of the pulsation of the plasma instead of a “chopper” to allow an a.c. amplification stage to be incorporated. It was suggested that such instruments could be made small enough to group around the tail flame and if advantage was taken of the release from inter-element effects the high temperature of the plasma brought it might be possible to carry out simultaneous determinations of several elements without prior separation.A further use of the pulsed plasma was suggested in selection of the source temperature. A stroboscope whose speed was maintained so that the transit of the stroboscope slit was always in phase with one particular stage of the growth and decay cycle would be used. Alteration of the phasing would allow other stages to be selected. Since each stage of growth and decay cycle represented a particular plasma temperature this would give a means of selecting the source temperature. Slides showing the apparatus in operation and a prototype of the type of stroboscope it was intended to use were shown.DISCUSSION MR. G. L. MASON remarked that he could not agree with the authors’ theory explain- ing the wedge-shaped silica line. Were this the case he would have expected other lines to be wedge shaped and he thought that the phenomena was due to the silica in the envelope being excited. He also asked if the authors had had any experience of the effect of varying grain size (in powders) on emission and also if they expected any third-element (or inter-element) effects to arise in the excitation of major constituents. Mr. Berry said that if there were any excitation of silica from the cell they would have expected to have found silica lines in the background and this was not so. There were other wedge-shaped lines on the plates as the slides had shown.These they were sure were due to the manner in which the exposures were taken with the image of the tail flame focused on the spectrograph slit and thus any variation in emission intensity along the length of the tail flame was reproduced on the plate. Furthermore when the optical arrangement was such that the image of the tail flame was focused upon the collimating lens no such wedge-shaped lines occurred. As yet little work had been done with powders ; what little experience the authors did have showed that with the present type of injector the sample would be injected better if the particles were between 100 and 250 mesh; but they could not say what effect if any particle size had upon emission. He added that at the moment they were working on another type of powder-feed mechanism in which particle size was not so critical.The depressive effect of aluminium and phosphate upon the calcium emission had been removed and they would expect that similar effects removable by a high flame temperature would not occur with the plasma torch. They would not like to say that no inter-element effects would occur. MR. R. J. THOMPSON asked the speaker to comment on the steadiness of emission from the tail-flame with a constant rate of input of any ion. The speaker replied that use of the Unicam SP900 flame photometer with the plasma torch as a source had shown the emission to be as steady as one would expect from a Aarne. In a series of about fifteen repeated scans of the calcium line at 4226.7 A over a period of 1 hour the peak height had varied &2 per cent.from the mean. These were readings of emission at one July 19651 TH IK-LAYER CHROMATOGRAPHY particular instant of time; with an instrument capable of intergrating over a period of time they would expect even better reproduction. In reply to I)R. A. C. TURNER who asked what the girth of the tail-flame was and if it could be reduced if necessary by using a higher radiofrequency the speaker said that it was from 0.5 to 1 cm depending on the type of injector used. It would be possible to reduce plasma size with a higher frequency but the size of the tail flame was to a large extent controlled by injector size and atomizer gas pressure. MR. E. H. S . VAN SOMEREN (Chaivman) asked the speaker whether the burner was operated under a suction device and if not whether changes of pressure in the room altered the luminosity or stability of the tail-flame. Mr. Berry replied that the torch was not operated under a suction device Mr. Berry said and if the door of the torch housing was open draughts did cause some turbulence in the tail flame but with the door closed it was stable. One might assume that if alterations in room pressure did alter the luminosity or stability the effect would be no more than in a normal flame. 113

ISSN:0037-9697    

DOI:10.1039/SA9650200105

出版商:RSC    

年代:1965

数据来源: RSC

摘要:

July 19651 TH IK-LAYER CHROMATOGRAPHY 113 Thin-layer Chromatography The following are summaxies of papers presented at the Joint 1-day Symposium of the Western Section and the Thin-layer Chromatography Group of the Society and the Welsh College of Advanced Technology held on February 19th 1965 and reported in the April 1965 issue of Proceedings (p. 42). Principles of Thin-film Chromatography BY E. V. TRUTER (Departvnem! of Textile Chemistry Ufiiversity of Leeds Leeds 2) DR. TRUTER said that although the quality of resolution in thin-film chromatography depended on many factors the most important single item was the method of development of the chromatogram. The requirements for elegant resolutions were discussed and illustrated by examples chosen from the fields of adsorption and partition chromatography continuous multiple-stage concentration-gradient and two-dimensional development.Some of the subsidiary factors including the method for spotting the sample and the degree of saturation of the atmosphere in the tank were also considered. Quantitative Aspects of Thin-layer Chromatography BY LINDSAY J. MORRIS (Unilever Research Lahovatory Sharnbvook Bedford) DR. MORRIS said that the simplicity and versatility of thin-layer chromatography as a separatory and micropreparative technique were by now almost universally appreciated. Quantitative analysis by tliin-layer chromatography however had not yet been widely adopted although there was generally a choice of several possible procedures for quantitatively determining any given class of compounds. Quantitative thin-layer chromatographic procedures might be divided into two distinct categories ; firstly determination of the separated components on the layer and secondly determination after removal from the plate.Within each category there were several procedures available for chemical and radiochemical quantitative determinations. Analysis of separated components on thin layers was most commonly performed by some measurement of the area or density of the spots. Several possible variants of this type of procedure were determination of minimum spot visibility measurement of the size or area of the spots on the chromatoplate or on photostats or photographs of it measurement of density and area of the spot by photodensitometry of plates or photographs in transmitted or reflected light and direct fluorimetry of spots on the plate.All of these procedures required 114 THIN-LAYER CHROMATOGRAPHY [Proc. SOC. Anal. Chem. comparison with known amounts of model mixtures that for reasonable accuracy must be chromatographically examined alongside the sample mixtures on the same plate. Radio- chemical analysis could be effected by radiometry of the intact layer with a proportional gas-flow counter or indirectly by photodensitometry of autoradiographs. This was important for organic chemical and biochemical work with radioactively labelled compounds but might also be used in suitable instances for normal chemical analysis in conjunction with radio- derivative techniques. Analysis of separated components after removal from the plate was generally carried out on the materials eluted from the scraped-off adsorbent.Gravimetric determination might be sufficient in a very few instances but compounds were normally determined by ultraviolet infrared visible or fluorescence spectrophotometry or if no chromophoric groups were present by colorimetry after reaction with a suitable chromogenic reagent. Colorimetry might sometimes be effected in the presence of the adsorbent. Other possibilities for analysis included bioassay of suitable biologically active materials and determination by gas - liquid chromatography relative to added known amounts of internal standards. Radioactively labelled compounds might be determined after elution from the adsorbent by end-window or scintillation counting or without prior elution from the adsorbent by suspension scintilation counting.All these various methods of quantitative analysis were described and their advantages disadvantages and limitations were considered. Thin-layer Electrophoresis BY W. J. CRIDDLE (Deflavtuuzent of Chevnistvy Welsh College of A doaizced Technology Cathays Pavk Cavdiff) DR. CRIDDLE said that just as thin-layer chromatography had many advantages over the corresponding paper methods so the use of thin-layer chromatographic materials for electro- phoresis had similar advantages in particular enhanced resolution and faster separation. To obtain satisfactory electropherograms of all types of compounds normally separable by electrophoresis it was necessary to observe a particular experimental technique. Firstly the plates after preparation in the normal way had to be soaked with electrolyte by means of a wick applied from one end only.Introduction of the electrolyte from both ends simultaneously usually produced a less satisfactory plate. Spraying had been shown to be completely unsatisfactory if reproducibility of ion mobility was required Saturation of the plate was finally completed by adding the second wick a maximum uptake of electrolyte of about 180 per cent. being obtained in about 1 hour. A serious problem of thin-layer electrophoresis concerned the drying of plates after electrophoresis. If compounds with high water solubility had been separated haphazard zone migration occurred on drying at elevated temperatures and it was therefore necessary to freeze-dry the plates before the detection reagent was applied. Such migrations had been observed for dyestuffs even on alumina a system with which adsorption effects were consider- able.The effects of heating during electrophoresis might be miriimised by controlling the applied potential such that a wattage not exceeding 0.021 watts per sq. cm was used for periods of up to 15 minutes and half this value for longer periods. This ensured that capillary rise could efficiently replace electrolyte lost by evaporation. If high applied potentials were used an external cooling device was essential. In this instance it was suggested that the thin-layer plate be covered with a further plate to prevent condensation developing on the cold thin layer this cover-plate being about 1 to 2 mm above the thin-layer surface. Preparative Layer Chromatography BY H. HALPAAP (E. Mevck A.G. Davmstadt West Gevmany) DR.HALPAAP said that the isolation of pure compounds from a mixture on a preparative scale depended on two facts complete separation of the different components and their exact location. The localisation of the different components could be simplified bv developing the July 19651 THIN-LAYER CHROMATOGRAPHY 115 method on a thin adsorbent layer preparative separations required larger amounts of com- pounds thicker layers and larger surfaces. When plates of 1-metre length were used in a special rack each containing five of them a 5-metre length of layer 20 cm high corresponding to an adsorbent surface of 1 sq. metre was available for each operation. In preparative layer chromatography the favourable separating power was based on the method of multiple development. Whereas in continuous chromatography the substances tended to diffuse considerably into the adsorbent the contraction of bands desirable in preparative layer chromatography was achieved by multiple development.Thus the adsorbing power of the adsorbent was optimally used. For precise separations Dr. Halpaap exclusively used highly active gypsum-free adsorbents with addition of a stabiliser in layers of 2 mm thickness. The adsorbents had to show effective binding power and be su-fficiently adhesive to the plate and the adjacent zones had to remain intact when the substance bands were scraped off. In contrast to the analytical method the separated substances in preparative layer chromatography could not be detected by reactions causing chemical changes. He therefore added an inorganic fluorescence indicator to the absorbent with whose aid adsorbing and non- absorbing substances could be recognised in short- and long-wave ultraviolet light by quench- ing or enhancement of the fluorescence.Since the substances moved exactly parallel to the starting line only infrequently localisation of the substances required guide lines to be drawn in preparative layer chromatography. Slides were shown of the equipment the speaker used and details about the practical procedure were given. With the aid of ultraviolet-adsorption spectra separations especially of natural substances were shown in various developmental stages. The efficiency of the method was demonstrated by fairly difficult separations of substances that belonged mainly to the fields of steroids and alkaloids. These separations were achieved by adsorption and partition chromatography.Preparative layer chromatography was more effective than column chromatography which required more material and time. The separation of substances whose structures were similar and which only slightly differed on the analytical thin-layer plate after one single development could be performed with the aid of preparative layer chromatography. This method could be used for separating substances of almost all types of compounds. The advantage of the procedure consisted in its convenient handling and saving of material and time as well as the possibility of obtaining very pure substances. Biological clinical and chemical experiments often yielded metabolites and reaction products in minimum amounts only and such compounds could be isolated in high purity by preparative layer chromato- For rough separations the speaker used layers of 10 mm thickness.graphy. R Values in Thin-layer Chromatography BY E. J. SHELLARD (Chelsea College of Scieace and Technology Manvesa Road London S. W.3) DR. SHELLAKD said that in any chromatographic system under given conditions the ratio of the rate of movement of a solute to that of the mobile phase in that part of the system beyond the point reached by the solute was a constant known as the R value. Where the rate of movement of the solute depended almost exclusively on the distribution coefficient a of the solute between the stationery phase and the mobile phase as in such partition chromato- graphic techniques as paper chromatography it could be shown with some approximation that- 1 - R R This had led to the use of RF values in paper chromatography RF values being defined as the ratio of the distance moved by the solute to the distance travelled by the solvent front during the same time the distance travelled by the spot being measured from its centre though there is some difference of opinion about the correctness of this procedure Provided that the conditions for each chromatographic run are more or less the same (and E.C. Rate- Smith Biochem. SOC. Symposium No. 3 1950 p. 62 had indicated what these conditions were) most substances could be given preliminary identification by their R values and this had led to the publication of tables of RF values for such purposes. a =I- 116 PAPERS ACCEPTED FOR PUBLICATION [Proc. soc. Anal. Chew. Since the technique of thin-layer chromatography was similar to that of paper chromato- graphy in many respects it had become the practice to quote RF values for substances ex- amined by this method.However in many instances the physicochemical principles involved were not the same. If alumina or silica gel was the material used for spreading the layer the separation of the solutes depended largely on- (;) the adsorptive capacity of the alumina or silica gel for the different solutes (ii) the adsorptive capacity of the alumina or silica gel for the solvent(s) and (iii) the solubility of the solutes in the solvent(s) that is to say it was based on adsorption chromatography There appeared to be several practical factors that influenced the adsorption of solutes and solvents by a particular adsorbent thus affecting the RF values of the solutes.Though some of these might be regarded as quite insignificant when considered alone in combination with each other they could have a marked effect. M. Rrenner A. Niederwieser G. Pataki and A. R. Fahmy (Experientia 1962 18 101) considered the practical factors to be- (a) quality of the adsorbent (6) (c) thickness of the layer (d) (e) temperature (f) (g) (h) ( j ) degree of activity of the prepared layer quality and nature of the solvent(s) degree of saturation of the chamber running distance and the distance between the starting-point and the solvent- immersion line the actual technique used (ascending descending horizontal) and the amount of solute i.e. the load. Experience in the speaker’s laboratories confirmed Brenner’s observations and also lead him to a further factor- ( k ) the nature of the solutes (in admixture). Whereas with paper chromatography it was not difficult to run many chromatograms under almost identical conditions with thin-layer chromatography it was more difficult to do so so that the RF values obtained were less reliable for purposes of preliminary identification.

ISSN:0037-9697    

DOI:10.1039/SA9650200113

出版商:RSC    

年代:1965

数据来源: RSC

摘要:

116 PAPERS ACCEPTED FOR PUBLICATION [PrOC. S O C . Anal. Chem. Papers Accepted for Publication in The Analyst THE following papers have been accepted for publication in The AnaZyst and are expected to appear in the near future. “The Determination of Small Amounts of Mercury in Organic Matter,” Report prepared by the Metallic Impurities in Organic Matter Sub-committee of the Analytical Methods Committee. “The Determination of Methanol by Oxidation to Formaldehyde and Polarographic Reduction,” by Mojmir Ranny. “The Polarographic Determination of Methyl Esters,’’ by Mojmir Ranny. “Spectrophotometric Determination of Alkylating Agents with 4-Picoline and o-Dinitro- benzene,” by Daniel F. Bender Eugene Sawicki and Ronald M. Wilson Jun. “An Absorptiometer for the Sugar Industry,’’ by S. Hill and J.T. Rundell. “An Automated Micro-determination of Blood Glucose with the AutoAnalyzer,” by “A Rapid Method for Quantitative Separation of Vitamin D from Vitamin A,” by “A Simple and Rapid Method for the Determination of Carbon in Iron and Steel,” by “Method for the Micro- and Semi-micro Determination of Thiamine in Pharmaceutical D. D. Faulkner. IC. K. Barua and M. V. K. Rao. R F. Jones P. Gale P. Hopkins and L. N. Powell. Preparations,” by F. Said M. M. Amer K. N. Girgis and 2. A. George. July 19651 CHANGES I N THE REGISTER OF MEMBERS 117 “The Micro-determination of Glutathione and Cysteine in the Presence of Each Other,” “The Control of Particle Characteristics in Precipitation and the Inter-relationship of “Determination of Cyclamates in Soft Drinks,” by D. I. Rees. “The Determination of Activation Products in Irradiated Steels by Anion-exchange “Hydroxylysine as a Growth Stimulant in Microbiological Assays for Lysine,” by “The Determination of Moisture in Plain Cakes by a Microwave Attenuation Technique,” “The Determination of Trace Amounts of Lead in Stainless and Other Steels,” by “A Comparison of the Fibrous-residue Determinations by the Official (A.O.A.C.) Method “Spectrophotometric Determination of Carbaryl in Insecticide Formulations,” by by M. Wroliski. Size-analysis Techniques,” by R. M. Morris. Separation and y-Ray Spectrometry,” by D. A. Hilton and D. Reed. A. W. Hartley L. D. Ward and K. J. Carpenter. by A. D. Ince and A. Turner. R. C. Rooney. and the Dimethylsulphoxide Method,” by H. Zentner. S. H. Yuen.

ISSN:0037-9697    

DOI:10.1039/SA9650200116

出版商:RSC    

年代:1965

数据来源: RSC

摘要:

July 19651 CHANGES I N THE REGISTER OF MEMBERS 117 Changes in the Register of Members NEW MEMBERS ORDINARY MEMBERS Ronald Edward Stuart Andrews B.Sc. (Lond.) A.R.I.C. ; Beryl Aspinwall B.Sc. (Lond.) A.R.I.C. ; Michael John Dinnis Brand K.Sc. (Rris.) ; Ronald Aubrey Chalmers ; John David Cheshire B.Sc. (Lond.) F.R.I.C. ; Andrew Kenneth Coulter A.R.I.C. ; Joseph William Alex- ander Edwards; Mohamed Tawfik Abd El-Aziz El-Ghamry B.Sc. (Cairo) ; George Clifford Goode B.Sc. A.R.I.C. ; Abdul Ghani Hamza B.Sc. (King Saud University) ; Brian George Hoyle L.R.I.C. ; John Harold Hunt B.Sc. Ph.D. (Lond.) ; Gianni Linoli Ph.Dr. ; William Horace Noakes ; Keith Henry Charles Pratley ; Thomas Holden Shuttleworth B.Sc. Ph.D. (Bris.); Derek Anthony Smith M.Sc. (Lond.) F.R.I.C. A.I.R.I. A.N.C.R.T.; Hugh Albert Sandry Stephens B.Sc. (Rhodes) ; Michael John Tarbox A.R.I.C. Dip.Tech. D.L.C. (Lough- borough) ; John Edward Tyler A.C.T. (Birm.) A.R.I.C. ; Terence Arthur Turner B.Sc. ; Rex Watkinson B.Sc. (Liv.) ; Frederick Walter Wilburn B.Sc. (Liv.). JUNIOR MEMBERS Brian James Arthur; Douglas Royle A.I.M.L.T. ; Malcolm Arthur Cox; Anthony Edwards; Michael John Edwards ; William George Harris ; Robert George Hawkins ; Alan Joseph Heeley ; Michael Alun Jenkins ; Stephen Riley Mathews ; Nicholas Ivor Stoyle ; Christine Theobald; Alan Bernard Vickers. DEATH Alec Munro Cameron. WE record with regret the death of

ISSN:0037-9697    

DOI:10.1039/SA9650200117

出版商:RSC    

年代:1965

数据来源: RSC

摘要:

118 PUBLICATIONS RECEIVED [Proc. SOC. Anal. Chew$. Publications Received The publications listed below have been received by the Editor of The Analyst in which journal Book Reviews will continue to appear. VISCOSITY OF ELECTROLYTES AND RELATED PROPERTIES. By R. H. STOKES D.Sc. F.A.A. and Oxford London Edinburgh New York Paris and Frank- Volume 3 of Topic 16 “Transport Properties of Electvolytes,” of The International Encyclopedia of Physical Chemistry and Chemical Physics. PROGRESS IN CHEMICAL TOXICOLOGY. Volume 2. Edited by ABRAHAM STOLMAN. Pp. x + 416 New York and London Academic Press. 1965. Price 100s. HUMIDITY AND MOISTURE MDASUREMENT AND CONTROL IN SCIENCE AND INDUSTRY. Editor-in- Chief ARNOLD WEXLER. Volume Two. APPLICATIONS. Editor ELIAS J . AMDUR. Pp. xvi + 634. New York Reinhold Publishing Corporation; London Chapman & Hall Ltd.1965. Price $27.50. Based on papers presented at the 1963 International Symposium o n Humidity and Moisture Washington D.C. R. MILLS Ph.D. furt Pergamon Press. 1965. Price 50s. Pp. x + 151. METHODS OF DETERMINING Eh AND pH I N SEDIMENTARY ROCKS. By GENNADII ANATOL’EVICH SOLOMIN. New York Consultants Bureau. 1965. Price $10.00. Pp. x + 259. New York Plenum Press. 1964. Price $15.00. Authorized Translation from the Russian by PAUL PORTER SUTTON. Pp. 56. INFRARED BAND HANDBOOK SUPPLEMENTS 1 & 2. Edited by HERMAN A. SZYMANSKI. COLLABORATIVE TESTS. Pp. 58. London The Pharmaceutical Press. 1965. Price 12s. 6d. Report of a Symposium held at the School of Pharmacy Brighton College of Technology May 30th 1964. DIE KOMPLEXOMETRISCHE TITRATION.Fifth Edition. By DR. GEROLD SCHWARZENBACH and DR. HERMANN FLASCHKA. Pp. xvi + 339. Stuttgart Ferdinand Enke Verlag. 1965. Price (cloth) DM 53; (paper) DM 48. SCHWEIZERISCHES LEBENSMITTELBUCH. Fifth Edition. By the SCHWEIZERISCHEN LEBENSMITTEL- BUCHKOMMISSION and the EIDGEN~SSICHEN GESUNDHEITSAMT. Volume 1. Pp. xx + 857. Bern Eidg. Drucksachen- und Materialzentrale. 1964. Price Sw.Fr. 75. BRITISH STANDARDS YEARBOOK 1965. Pp. iv + 796. London British Standards Institution. 1965. Price 15s. FORMULA INDEX TO NMR LITERATURE DATA. Volume 1 REFERENCES PRIOR TO 1961. Edited by M. GERTRUDE HOWELL ANDREW S. KENDE and JOHN S. WEBB. Pp. xiv + 206. New York Plenum Press. 1965. Price $17.50. INTERPRETATION OF NMR SPECTRA AN EMPIRICAL APPROACH. By ROY H. BIBLE JuN. Ph.D. Pp. x + 150 + folder.New York Plenum Press. 1965. Price $12.50. MATHEMATICAL ANALYSIS OF OBSERVATIONS. By B. M. SHCHIGOLEV. Pp. xvi + 350. London Iliffe Books Ltd. New York American Elsevier Publishing Company Inc. 1965. Price 63s. ; $10.00. OPEN TUBULAR COLUMNS IN GAS CHROMATOGRAPHY. By L. S. ETTRE. Pp. xx + 164. New York Plenum Press. 1965. Price $4.95. PROGRESS IN THE CHEMISTRY OF FATS AND OTHER LIPIDS. Volume 8. Part 1. PHOSPHOLIPIDS AND BIOMEMBRANES. Pp. vi + 127. Oxford London Edinburgh New York Paris and Frankfurt Pergamon Press. 1965. Price 50s. Pp. x + 190. Oxford London Edinburgh New York Paris and Frankfurt Pergamon Press. 1965. Price 15s. By HENRY A. BENT. Pp. xii + 429. New York Oxford University Press. 1965. Price $6.00. By L. L. M. VAN DEENAN. Edited by R. T. Holman. SOME ELECTRICAL AND OPTICAL ASPECTS OF MOLECULAR BEHAVIOUR. By MANSEL DAVIES. THE SECOND LAW AN INTRODUCTION TO CLASSICAL AND STATISTICAL THERMODYNAMICS.

ISSN:0037-9697    

DOI:10.1039/SA9650200118

出版商:RSC    

年代:1965

数据来源: RSC