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Quantitative analysis by Fourier transform infrared spectroscopy
X
trends in analyt:~calchemistry, vol. 5,too. 4, r~986
and tradition. However if one takes into account the progress that has been made during the last ten years, the prospects for improvements are encouraging.
References 1 T. Braun and E. Bujdos6, Talanta, 30 (1983) 161. 2 H. Kellner and H. Malissa, Fresenius' Z. Anal. Chem., 319 (1984) 1. 3 E. Pungor, Fresenius' Z. Anal. Chem., 317 (1984) 841.
observer
4 T.L. Isenhour, Anal. Chem., 55 (1983) 824 A. Dr. Panayotis A. Siskos received his chemistry diploma from the University of ThessaIoniki and his Ph.D. in analytical chemistry from the University of Athens in 1973. After a period of three years as research associate in the U.S.A., he rejoined the University of Athens, where he teaches analytical chemistry, environmental chemistry and clinical chemistry. His" current research interests are kinetic methods of analysis, enzymatic methods
Dr. Miltiades Karayannis received his diploma of chemistry from the University of Thessaloniki (Greece) and his Ph.D. in Chemistry from the University of Bonn (W. Germany). He is full professor and director of the Laboratory of Analytical Chemistry at the University of loannina and teaches analytical chemistry and chemical instrumentation. His current research interests are kinetic methods of analysis using photometric and electrochemical methods.
topics of interest in the current literature
Quantitative analysis by Fourier transform infrared spectroscopy Infrared (IR) spectroscopy is a commonly used technique in analytical chemistry for identification and structure elucidation. Until recently, it had relatively few applications as a quantitative tool. Common data handling techniques such as multi-component analysis, least-squares fitting and cross-correlation were used 1. Currently, however, there is an increasing interest in quantitative applications. The development of Fourier transform infrared (FTIR) spectroscopy has greatly improved the photometric accuracy 2. Consequently, specific IR techniques that were formerly used as qualitative tools have now become available for quantitative analysis: especially attenuated total reflection (ATR) spectroscopy and photoacoustic (PA) spectroscopy. An extensive study by M/iller et al. 3 formed the theoretical basis of the quantitative applications of FTIR-ATR spectroscopy. The technique has some properties that can be matched by few other methods. It is suitable for samples that can be brought into contact with the internal reflection element (IRE). IR light is passed through this IRE crystal and is reflected at the boundary layer between sample and crystal. To some extent the light penetrates into the sample, which absorbs in its characteristic IR-bands 4. The method can 0165-9936/86/$02.00.
of analysis and environmental analysis.
be applied to surface characterization of polymer films and thin coating layers, and the study of surface adsorption by proteins. Transparency of the sample is not required. Surface characterization is important if the composition of the surface layer is different from that in the bulk of the sample. Because of the poor reproducibility this method needs careful experimentation. An example is the determination of poly(dimethylsiloxane) in the surface layer of Cardiothane 515, which is a commercially available nonthrombogenic material. The specific function of its non-thrombogenicity is closely related to an optimal content of poly(dimethylsiloxane) that comes in contact with the blood 6. A complication arises when the thickness of the surface layer is less than the penetration depth of the IR light. This has been observed in the quantitative analysis of surface-adsorbed proteins 7. A bulk contribution factor has been used to correct for IR-band contributions from proteins which are not adsorbed onto the surface of the IRE crystal. Another sophisticated technique for quantitative analysis is photoacoustic spectroscopy (FTIR-PAS). Here, chopped monochromatic IR light is passed through the window of a tightly closed cell containing the sample. The radiant energy ab-
sorbed by the sample is converted to heat by radiationless decay pathways. This heat flows to the surrounding gas and generates a pressure pulse which is detected with a microphone 8, Sample preparation is relatively simple and PA spectra can easily be obtained. However, it is important to control particle size accurately. This method is gradually superseding diffuse reflectance (DRIFT) spectroscopy, which has formerly had wide usage as a method for quantitative analysis of solid samples 9. Since 1978 FTIR-PA spectroscopy has been applied to the quantitative analysis of a variety of samples. An interesting application is the analysis of materials separated on thin-layer chromatography (TLC) plates 1°. The development of an open-ended PAS cell provided non-destructive analysis 11. As opposed to other analytical methods where the sample must be removed from the TLC plate by scraping or delution, there is no loss of sample here. Another application is the quantitative determination of catalytic surface adsorption sites 12. PA spectroscopy makes it possible to calculate the active site percentage of a catalyst, e.g. the adsorption of CO(g) at a Ni/SO 2 catalyst 13. Finally, a useful application is the determination of the composition of binary mixtures ~4 and copotymeric systems 9, for instance the analysis of polyester-cotton mixtures 15. FRANK LIJTEN, JO KLAESSENS and G E R R I T KATEMAN (~ Elsevier SciencePublishersB.V.
X[
trends in analyticalchemistry, vol. 5, no. 4, 1986
References 1 L. L. Tyson, Y. Ling and C. K. Mann, Appl. Spectrosc., 38 (1984) 663. 2 J. Knecht, Int. Lab., May (1984) 34. 3 G. MUller, K. Abraham and M. Schaldach, Appl. Opt., 20 (1981) 1182. 4 N. J. Harrick, Internal Reflection Spectroscopy, Wiley, New York, 1967. 5 R. Iwamoto and K. Ohta, Appl. Spectrosc., 38 (1984) 359. 6 E. Nyilas and R. S. Ward, J. Biomed. Mater. Res. Symp., 8 (1977) 69. 7 D. J. Fink and R. M. Grendeau, Anal. Biochem., 139 (1984) 140. 8 L. C. Aamodt, J. C. Murphy and J. G. Parker, J. Appl. Phys., 48 (1977) 927. 9 G. F. Kirkbright and K. R. Menon, Anal. Chim. Acta, 136 (1982) 373.
10 S. L. Castleden, C. M. Elliott, G. F. Kirkbright and D. E. M. Spillane, Anal. Chem., 51 (1979) 2152. 11 V. A. Fishman and A. J. Bard, Anal. Chem., 53 (1981) 102. 12 L. B. Lloyd, R. B. Yeates and E. M. Eyring, Anal. Chem., 54 (1982) 549. 13 J. A. Gardella, D. Jiang and E. M. Eyring, Appl. Spectrosc., 37 (1983) 131. 14 M. G. Rockley, D. M. Davis and H. H. Richardson, Appl. Spectrosc., 35 (1981) 185. 15 C. M. Ashworth, G. F. Kirkbright and D. E. M. Spillane, Analyst (London), 108 (1983) 1481.
cesses both in gas and liquid chromatography received considerable attention with about 25 papers presented. In contrast, optimization of experimental conditions were considered only in a few papers, which is surprising in view of the general trends in this field. Application of chromatographic techniques to physicochemical measurements was illustrated in 10 papers.
Frank Lijten, Jo Klaessens and Gerrit Kateman are at the Laboratorium voor Analytische Chemie, Toernooiveld, 6525 ED Nijmegen, The Netherlands.
Development and improvement of detectors both in GC and LC, as well as special, mainly multidimensional chromatographic systems were discussed in about 9 papers. Microcolumn chromatography received attention in some papers for separation of biological materials. A new derivatization agent and some improved derivatization procedures were also discussed. Computer-assisted chromatography was the main topic in about 8 papers ranging from data processing to computer simulation and pattern recognition. Overpressurized thin-layer chromatographic technique was demonstrated in some papers, including a general optimization procedure. Capillary gas chromatography received attention in a large number of papers dealing with wide bore columns, immobilized thich film columns, multi-dimensional arrangements and preparation, and characterization and comparison of fusedsilica and glass capillary columns. Over 40 papers were presented on the development, modification and special application of new packing materials including modified silicas, porous polymers containing various functional groups, modified zeolites, carbon-based or carbon-modified non-polar adsorbents, liquid crystals, and cyclodextrins. The various aspects of ion-exchange chromatography received attention in about 20 papers. In addition to the application of ion exchange resins for separation of biological materials and various metals, fibrous ion exchangers, and ion ex-
meeting reports Fifth Danube Symposium on Chromatography A report on the Fifth Danube Symposium on Chromatography, held in Yalta, U.S.S.R., 11-16 November 1985. The series of Danube Symposia on Chromatography has been started in 1976 in Szeged, Hungary and is being organized since 1979 every second year in a socialist country as a counterpart of the bi-ennial International Symposia sponsored by the western Chromatographic Groups and Socities. The main idea of the Danube Symposia is to promote an exchange of ideas and better understanding among scientists of western and socialist countries who have limited opportunity to meet each other. The Fifth Danube Symposium on Chromatography was organized by The Scientific Council on Chromatography, Academy of Sciences of the U.S.S.R. The Symposium was attended by 580 delegates from 21 countries, including ca. 300 participants from the U.S.S.R. The scientific programme comprised 14 plenary lectures, 70 oral lectures and about 280 poster presentations dealing with all aspects
of chromatography and related techniques. The plenary lectures gave an overview of the state-of-art and future developments of chromatographic techniques of current interest, including topics such as quantification of the information of chromatographic retention data, chromadistillation, computer-aided rapidscanning UV-VIS detection, electrophoretic separation of living cells, microcolumn separation methods, molecular structure and solute-solvent interactions, multicomponent chromatography, overpressurized thin-layer chromatography, microcolumn chromatography of polymers and proteins, evaluation of overlapping peaks, enantiomeric analysis on chiral phases, computer chromatography, trace analysis, and application of high-performance liquid chromatography (HPLC) in biology and medicine. The oral and poster presentations were structured around nearly 30 topics. Unfortunately, the number of oral papers necessitated three parallel sessions compelling delegates to be selective in their choice. Theoretical aspects of retention mechanism and mass transfer pro-
Development of new techniques and equipment
trends in analyt:~calchemistry, vol. 5,too. 4, r~986
and tradition. However if one takes into account the progress that has been made during the last ten years, the prospects for improvements are encouraging.
References 1 T. Braun and E. Bujdos6, Talanta, 30 (1983) 161. 2 H. Kellner and H. Malissa, Fresenius' Z. Anal. Chem., 319 (1984) 1. 3 E. Pungor, Fresenius' Z. Anal. Chem., 317 (1984) 841.
observer
4 T.L. Isenhour, Anal. Chem., 55 (1983) 824 A. Dr. Panayotis A. Siskos received his chemistry diploma from the University of ThessaIoniki and his Ph.D. in analytical chemistry from the University of Athens in 1973. After a period of three years as research associate in the U.S.A., he rejoined the University of Athens, where he teaches analytical chemistry, environmental chemistry and clinical chemistry. His" current research interests are kinetic methods of analysis, enzymatic methods
Dr. Miltiades Karayannis received his diploma of chemistry from the University of Thessaloniki (Greece) and his Ph.D. in Chemistry from the University of Bonn (W. Germany). He is full professor and director of the Laboratory of Analytical Chemistry at the University of loannina and teaches analytical chemistry and chemical instrumentation. His current research interests are kinetic methods of analysis using photometric and electrochemical methods.
topics of interest in the current literature
Quantitative analysis by Fourier transform infrared spectroscopy Infrared (IR) spectroscopy is a commonly used technique in analytical chemistry for identification and structure elucidation. Until recently, it had relatively few applications as a quantitative tool. Common data handling techniques such as multi-component analysis, least-squares fitting and cross-correlation were used 1. Currently, however, there is an increasing interest in quantitative applications. The development of Fourier transform infrared (FTIR) spectroscopy has greatly improved the photometric accuracy 2. Consequently, specific IR techniques that were formerly used as qualitative tools have now become available for quantitative analysis: especially attenuated total reflection (ATR) spectroscopy and photoacoustic (PA) spectroscopy. An extensive study by M/iller et al. 3 formed the theoretical basis of the quantitative applications of FTIR-ATR spectroscopy. The technique has some properties that can be matched by few other methods. It is suitable for samples that can be brought into contact with the internal reflection element (IRE). IR light is passed through this IRE crystal and is reflected at the boundary layer between sample and crystal. To some extent the light penetrates into the sample, which absorbs in its characteristic IR-bands 4. The method can 0165-9936/86/$02.00.
of analysis and environmental analysis.
be applied to surface characterization of polymer films and thin coating layers, and the study of surface adsorption by proteins. Transparency of the sample is not required. Surface characterization is important if the composition of the surface layer is different from that in the bulk of the sample. Because of the poor reproducibility this method needs careful experimentation. An example is the determination of poly(dimethylsiloxane) in the surface layer of Cardiothane 515, which is a commercially available nonthrombogenic material. The specific function of its non-thrombogenicity is closely related to an optimal content of poly(dimethylsiloxane) that comes in contact with the blood 6. A complication arises when the thickness of the surface layer is less than the penetration depth of the IR light. This has been observed in the quantitative analysis of surface-adsorbed proteins 7. A bulk contribution factor has been used to correct for IR-band contributions from proteins which are not adsorbed onto the surface of the IRE crystal. Another sophisticated technique for quantitative analysis is photoacoustic spectroscopy (FTIR-PAS). Here, chopped monochromatic IR light is passed through the window of a tightly closed cell containing the sample. The radiant energy ab-
sorbed by the sample is converted to heat by radiationless decay pathways. This heat flows to the surrounding gas and generates a pressure pulse which is detected with a microphone 8, Sample preparation is relatively simple and PA spectra can easily be obtained. However, it is important to control particle size accurately. This method is gradually superseding diffuse reflectance (DRIFT) spectroscopy, which has formerly had wide usage as a method for quantitative analysis of solid samples 9. Since 1978 FTIR-PA spectroscopy has been applied to the quantitative analysis of a variety of samples. An interesting application is the analysis of materials separated on thin-layer chromatography (TLC) plates 1°. The development of an open-ended PAS cell provided non-destructive analysis 11. As opposed to other analytical methods where the sample must be removed from the TLC plate by scraping or delution, there is no loss of sample here. Another application is the quantitative determination of catalytic surface adsorption sites 12. PA spectroscopy makes it possible to calculate the active site percentage of a catalyst, e.g. the adsorption of CO(g) at a Ni/SO 2 catalyst 13. Finally, a useful application is the determination of the composition of binary mixtures ~4 and copotymeric systems 9, for instance the analysis of polyester-cotton mixtures 15. FRANK LIJTEN, JO KLAESSENS and G E R R I T KATEMAN (~ Elsevier SciencePublishersB.V.
X[
trends in analyticalchemistry, vol. 5, no. 4, 1986
References 1 L. L. Tyson, Y. Ling and C. K. Mann, Appl. Spectrosc., 38 (1984) 663. 2 J. Knecht, Int. Lab., May (1984) 34. 3 G. MUller, K. Abraham and M. Schaldach, Appl. Opt., 20 (1981) 1182. 4 N. J. Harrick, Internal Reflection Spectroscopy, Wiley, New York, 1967. 5 R. Iwamoto and K. Ohta, Appl. Spectrosc., 38 (1984) 359. 6 E. Nyilas and R. S. Ward, J. Biomed. Mater. Res. Symp., 8 (1977) 69. 7 D. J. Fink and R. M. Grendeau, Anal. Biochem., 139 (1984) 140. 8 L. C. Aamodt, J. C. Murphy and J. G. Parker, J. Appl. Phys., 48 (1977) 927. 9 G. F. Kirkbright and K. R. Menon, Anal. Chim. Acta, 136 (1982) 373.
10 S. L. Castleden, C. M. Elliott, G. F. Kirkbright and D. E. M. Spillane, Anal. Chem., 51 (1979) 2152. 11 V. A. Fishman and A. J. Bard, Anal. Chem., 53 (1981) 102. 12 L. B. Lloyd, R. B. Yeates and E. M. Eyring, Anal. Chem., 54 (1982) 549. 13 J. A. Gardella, D. Jiang and E. M. Eyring, Appl. Spectrosc., 37 (1983) 131. 14 M. G. Rockley, D. M. Davis and H. H. Richardson, Appl. Spectrosc., 35 (1981) 185. 15 C. M. Ashworth, G. F. Kirkbright and D. E. M. Spillane, Analyst (London), 108 (1983) 1481.
cesses both in gas and liquid chromatography received considerable attention with about 25 papers presented. In contrast, optimization of experimental conditions were considered only in a few papers, which is surprising in view of the general trends in this field. Application of chromatographic techniques to physicochemical measurements was illustrated in 10 papers.
Frank Lijten, Jo Klaessens and Gerrit Kateman are at the Laboratorium voor Analytische Chemie, Toernooiveld, 6525 ED Nijmegen, The Netherlands.
Development and improvement of detectors both in GC and LC, as well as special, mainly multidimensional chromatographic systems were discussed in about 9 papers. Microcolumn chromatography received attention in some papers for separation of biological materials. A new derivatization agent and some improved derivatization procedures were also discussed. Computer-assisted chromatography was the main topic in about 8 papers ranging from data processing to computer simulation and pattern recognition. Overpressurized thin-layer chromatographic technique was demonstrated in some papers, including a general optimization procedure. Capillary gas chromatography received attention in a large number of papers dealing with wide bore columns, immobilized thich film columns, multi-dimensional arrangements and preparation, and characterization and comparison of fusedsilica and glass capillary columns. Over 40 papers were presented on the development, modification and special application of new packing materials including modified silicas, porous polymers containing various functional groups, modified zeolites, carbon-based or carbon-modified non-polar adsorbents, liquid crystals, and cyclodextrins. The various aspects of ion-exchange chromatography received attention in about 20 papers. In addition to the application of ion exchange resins for separation of biological materials and various metals, fibrous ion exchangers, and ion ex-
meeting reports Fifth Danube Symposium on Chromatography A report on the Fifth Danube Symposium on Chromatography, held in Yalta, U.S.S.R., 11-16 November 1985. The series of Danube Symposia on Chromatography has been started in 1976 in Szeged, Hungary and is being organized since 1979 every second year in a socialist country as a counterpart of the bi-ennial International Symposia sponsored by the western Chromatographic Groups and Socities. The main idea of the Danube Symposia is to promote an exchange of ideas and better understanding among scientists of western and socialist countries who have limited opportunity to meet each other. The Fifth Danube Symposium on Chromatography was organized by The Scientific Council on Chromatography, Academy of Sciences of the U.S.S.R. The Symposium was attended by 580 delegates from 21 countries, including ca. 300 participants from the U.S.S.R. The scientific programme comprised 14 plenary lectures, 70 oral lectures and about 280 poster presentations dealing with all aspects
of chromatography and related techniques. The plenary lectures gave an overview of the state-of-art and future developments of chromatographic techniques of current interest, including topics such as quantification of the information of chromatographic retention data, chromadistillation, computer-aided rapidscanning UV-VIS detection, electrophoretic separation of living cells, microcolumn separation methods, molecular structure and solute-solvent interactions, multicomponent chromatography, overpressurized thin-layer chromatography, microcolumn chromatography of polymers and proteins, evaluation of overlapping peaks, enantiomeric analysis on chiral phases, computer chromatography, trace analysis, and application of high-performance liquid chromatography (HPLC) in biology and medicine. The oral and poster presentations were structured around nearly 30 topics. Unfortunately, the number of oral papers necessitated three parallel sessions compelling delegates to be selective in their choice. Theoretical aspects of retention mechanism and mass transfer pro-
Development of new techniques and equipment