Development of Analytical Chemistry in the Latter Half of the 20th Century (Scientometric Analysis)

Based on publications in Analytical Chemistry and Zhurnal Analiticheskoi Khimii and abstracts of Pittsburgh conferences, changes in analytical chemistry in the latter half of the 20th century are followed. It is noted that interest in the development of separation techniques and the analysis of environmental and biological samples has considerably increased. A direct scientometric analysis of the contents of publications is used in these scientometric studies.     

Computer modeling of radical copolymerization under unusual conditions

Although recent years have witnessed an impressive confluence of experiments and kinetic and statistical theories, presently there is no comprehensive understanding of the interrelation between chemical sequences in synthetic copolymers and the conditions of synthesis. For this problem, numerical simulations in conjunction with simple models provide a rather detailed answer. A survey is given of the simulation methods as applied to the design of nontrivial chemical sequences in copolymers obtained via heterogeneous radical polymerization. This review is focused on a recently developed approach, called conformation‐dependent sequence design, which takes into account a strong coupling between the conformation and primary structure of copolymers during their synthesis. We consider some applications of this technique, including the following problems and systems: (1) the design of sequences with long‐range correlations via solution radical copolymerization with simultaneous globule formation, (2) radical copolymerization near a chemically homogeneous surface leading to a copolymer with a gradient primary structure, and (3) template copolymerization near chemically patterned surfaces. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5339–5353, 2004     

Thin-layer chromatography with high-boiling mobile phase. part 2: Effect of temperature on retention characteristics in TLC with high-boiling mobile phases

A study has been undertaken on the effect of temperature on retention characteristics in thin-layer chromatography (TLC) with low-volatility mobile phases (MP). It is shown that temperature variations in TLC in melts bring about variations in both the relative retention values and, in some cases, in the order of migration of the chromatographic zones across the layer. The variation in the capacity factor k' with temperature agrees well with Martin's equation. To explain the temperature dependence of R_f one must, in general, take into account the variations with temperature in both the partition coefficient and the phase ratio. To describe the variation in R_f with temperature in TLC with low-volatile MP one can use an approximate equation in which In R_f is a linear function of 1/T. The experiments indicate that temperature is a major factor in TLC in melts.     

Dependence of the width of the chromatographic zone on retention time in capillary gas chromatography

The dependence of the width of the chromatographic zone on retention time for capillary columns was studied theoretically and experimentally. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 320–322, February, 1997.     

A variant of circular thin-layer chromatography with a forced flow of the mobile phase produced by an electroosmotic pump

A new variant of circular thin-layer chromatography (TLC) with a closed sorption layer in which a forced flow of the mobile phase was produced and controlled by an external electroosmotic pump placed at the center of a TLC plate was suggested. It was shown experimentally that the method operated properly and could be used in planar chromatography.     

Use of equations for the description of experimental dependence of the height equivalent to a theoretical plate on carrier gas velocity in capillary gas-liquid chromatography

Optimal equation for fitting the experimental data on the height equivalent to a theoretical plate (HETP) versus carrier gas velocity in GLC was determined. The data obtained by authors and the literary data by other investigators were used for the comparative study of Van Deemter, Golay and the little known Golay-Guiochon equations. The Golay-Guiochon equation takes into account instrumental contribution and other sources of additional band broadening. Correlation coefficient R and Pirson's criterion chi2 were used as a criterion of the data correspondence to the equations. The Golay-Guiochon equation is the best for fitting of the experimental data in 71% considered examples, 19% experimental data may be fitted very precisely by the Van Deemter equation, the Golay equation is preferable for 7% experimental data only. Three percent experimental data may be fitted with the same precision by the Golay and the Van Deemter equations. The results obtained are of theoretical and practical interest. The Golay-Guiochon equation must be used more widely in analytical practice and physicochemical measurements.     

Investigation of the role of adsorption at the stationary phase interface in capillary columns prepared with cross-linked phases

Summary On the basis of the adsorption-absorption additivity theory the influence of adsorption on the retention of polar samples has been quantitatively studied using fused-silica capillary columns coated with nonpolar cross-linked and non-cross-linked liquid stationary phases. It is shown that cross-linking of a nonpolar stationary phase increases the contribution of adsorption to the retention of polar compoments. As a result the retention of polar compounds increases on crosslinked stationary phases as compared with the initial (non cross-linked) phase. “The material of this paper was presented at the 15th International Symposium on Chromatography, Nürnberg, October, 1984”     

Steam chromatography with water—salt and water—acid inorganic phases

Th peculiarities of steam chromatography with water-salt and water-acid stationary liquid phases have been studied. The effects of the nature of the salt, its concentration in the stationary liquid phase, and the temperature of the column on retention values have been studied using C₁-C₈ primary nonbranched alcohols as an example. The advantages and disadvantages of steam chromatography with aqueous electrolyte phases arid challenges for the development of' this method are discussedTranslated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1733–1739, July, 1996.     

Investigation of the role of the carrier gas in capillary gas-solid chromatography

Nonideal interactions of the sorbate and the carrier gas and adsorption of the sorbate on the adsorbent surface in capillary gas-solid chromatography were studied. Chromatographic retention was found to be largely determined by adsorption processes. With respect to the retention coefficients (capacity factors) of a sorbate (k) with different carrier gases (P₁ and P₂), the correlation relationshipk(P₂) =A·k(P₁) +B (A, B are parameters of the equation) is closely obeyed. The advantages of carbon dioxide as the carrier gas were analyzed; the use of carbon dioxide allows the efficiency of the column to be enhanced.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 627–633, March, 1996.