I. A. Revel’skii

Determination of organic compounds in human hair

Data reported in the literature on methods for the determination of organic compounds of different classes in human hair are systematized. Special attention is given to methods for the extraction and preconcentration of organic compounds from hair. A comparative analysis of existing methods is performed.

A new approach to determining derivatization degree and its use for the investigation of silylation of methyltestosterone in nano-/microgram amounts

AbstractsA new approach to establishing the yield of derivatization reactions of difficult-to-derivatize steroids is proposed on the basis of the comparison of the areas of chromatographic peaks between the native form of the analyte and its derivative. The influence of material to be derivatized, i.e., methyltestosterone, in an amount of 5 and 500 ng, and the time of reaction, 5–120 min, on the degree of conversion is studied. Methyltestosterone is derivatized at 80°C in a mixture of pyridine and N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA) with 1% trimethylchlorosilane. Prior to the injection of samples into the gas chromatograph, pyridine and BSTFA are replaced with an inert organic solvent, methyl tert-butyl ether. The degree of methyltestosterone derivatization is shown statistically independent of the amount of the steroid processed. The performance of the reaction for 1 h at 80°C ensures reaction yield of around 90%.

Gas chromatography of organic mixtures using an atomic emission detector

Specific features of the combination of gas chromatography with atomic emission detection and the prospects for the determination of components of organic mixtures are considered. Attention is mainly focused on the application of a commercial system developed in 1990 by the Hewlett-Packard Company. The scope and limitations of the method are scrutinized; methods for improving the reliability of the results of analyses are discussed.

Supercritical fluid extraction coupled with chromatography-mass spectrometry: Hair analysis. Chromatography-mass spectrometry data processing using the CODA mathematical algorithm

The composition of medium-volatility organic compounds extracted from human hair using supercritical fluid extraction (SFE) was determined. The entire extract was trapped from a gas flow in a sorption device at the extractor outlet and thermally desorbed into a gas chromatography-mass spectrometry (GC-MS) instrument. The extracted compounds were identified either by the direct processing of GC-MS data or using the CODA mathematical algorithm. The combination of solventless SFE with the transfer of the entire extract into a GC-MS instrument with the direct analysis of GC-MS data allowed us to determine organic compounds at a level of 3.9 pg/mg hair. The CODA mathematical algorithm for the processing of GC-MS data allowed us to determine compounds at a level of 1.7 pg/mg hair; in the majority of publications, this determination limit was achieved either by selective ion detection or using a GC-MS-MS technique.

Determination of the main component in high-purity organic substances: Current status and prospects

The current status of the determination of the purity of high-purity organic substances using direct and indirect chromatographic methods is discussed. It is shown that the results of the chromatographic determination of the main component in high-purity organic materials are generally ambiguous and unreliable. The possibility of determining the purity of organic compounds using an elemental analyzer of C, H, and N without involving standard samples of analytes is examined; the advantages and drawbacks of this approach are discussed. It is demonstrated experimentally by the example of several nitrogenated compounds that the main component can be determined with an error no worse than 0.6 rel. %, whereas the error of element (nitrogen) determination in the molecule does not exceed the permissible error of elemental analysis.

A new method for the simultaneous and highly sensitive determination of the total content of F-, Cl-, Br-, and S-organic compounds in products of oil refining

A new method for the simultaneous determination of the total content of fluorine-, chlorine-, and sulfur-containing organic compounds in products of oil refining is proposed. The method is based on the high-temperature oxidation of a sample in a flow of oxygen, the absorption of conversion products, and the analysis of the total absorbate in isocratic conditions by the ion chromatography method for the content of anions that correspond to the analytes. The detection limit for the total content of Cl-, Br-, and S-organic compounds in a sample of 1 μl is 10−5%; for F-containing compounds, it is 10−6%. The results of the analysis of samples of aviation kerosene and gasoline for the total content of F-, Cl-, Br-, and S-organic compounds are presented.

Identification of unknown compounds using data bases and computer simulation of mass spectra

The possibility of identification based on the comparison of experimental electron-ionization mass spectrum of an unknown (in our case, model) compound with the mass spectra of the candidate compounds generated by the Mass Frontier software has been demonstrated by the example of three model compounds. The structural isomers of the identified substances found in the ChemExper database have been used as the candidate compounds. The candidate substances have been ranged by the degree of similarity between their simulated mass spectra and the experimental mass spectrum of the unknown compound. The mass spectra have been compared on the basis of the algorithm used in the NIST MS Search standard search system. In all three cases, the sought-after structure has been indicated as the most probable one of all the candidate structures.

Application of principal component analysis to the extraction of pure mass spectra in chemical analysis by gas chromatography/mass spectrometry

In this work, we investigated the possibility of the purification of mass spectra of coeluted substances containing at least one characteristic value of m/z using principal component analysis. Simulated and real gas chromatographic/mass spectrometric data were analyzed. For the simulated data, the resolution of the chromatographic peaks varied from 0.075 to 0.75, and the ratio of component concentrations ranged from 0.01 to 100. Noise-free simulated data and simulated data with randomly distributed noise were considered. It was shown that the method gave satisfactory results even when the chromatographic resolution (Rs) was less than 0.05.

A new approach to comparison of original pharmaceuticals and generics based on comparison of multidimensional impurity profiles using supercritical fluid extraction, liquid extraction, and GC-MS

This paper reports on our effort to study the possibility of comparing the original pharmaceuticals and their analogs (generics) based on comparisons of the multidimensional profiles of impurities isolated from samples by supercritical fluid extraction and liquid extraction and recorded by gas chromato-mass spectrometry (GC-MS) with electron ionization (EI) and atmospheric pressure photochemical ionization (APPhCI). Using the suggested approach makes it possible to increase the number of recorded impurities, to show that the pharmaceutical samples are authentic, and to compare the original pharmaceuticals and generics according to their quality.

Comparison of electron ionization mass spectra of some organic compounds (MW < 200 Da) recorded on mass spectrometers of various types

Low-resolution electron ionization mass spectra recorded on various types of mass spectrometers (time-of-flight, quadrupole, and three-dimensional ion trap) were compared. A model mixture of 10 organic compounds (MW < 200 Da) was analyzed by gas chromatography-mass spectrometry. Pure mass spectra of analytes were extracted using the AMDIS software. The best repeatability was achieved for the time-of-flight mass spectrometer. The mass spectra recorded by a quadrupole and a time-of-flight mass spectrometer were quite similar. In the case of these instruments, library search using a commercial mass spectral data base (NIST’05) gave satisfactory result for each analyte (rank 1 or 2 in the “hit list”; Match > 900). In some cases, the mass spectra of model compounds recorded by the ion trap mass spectrometer differed in intensity of certain mass spectral peaks (but not in the set of peaks) from the mass spectra presented in the library and from the experimental mass spectra recorded by the time-of-flight and quadrupole instruments.