Features of trialkyl thiophosphates characterization by the retention indices in HPLC combined with the mass spectrometric data

Abstract

HPLC-MS characterization of 12 homologues of trialkyl thiophosphate series was conducted including the determination of their retention indices ( RI ) and the registration of the mass spectra with the electro­spray ionization in the positive mode. The correlation of RI(HPLC) and RI(GC) values for trialkyl phos­phates was confirmed. It was revealed that the dependence of RI(HPLC) vs . molecular masses of ho­mo­logues with the high precision could be approximated by the linear regression RI = aM + b . The ano­malies of this dependence were caused by the features of two analytical methods: the branches of the carbon skeleton of analytes’ molecules strongly influence the GC retention parameters, while in HPLC such influence was much less. The possibilities of the application of so-called homologous increments of retention indi­ces, i RI = RI - x DRI(CH 2 ), where х = int( M /14), “int” is the integer part of the quotient from the division of the molecular mass number by 14, that is equivalent to M = 14 x + y , у М – the number of homologous group of analyte, y М º M (mod14), DRI(CH 2 ) – the retention index increment of homologous difference СН 2 (in GC it is equal to 100) were considered. It was demonstra­ted that in HPLC this increment may not be equal to 100; for instance, for trialkyl thiophosphates the more informative value was DRI(CH 2 ) = 74. The application of the i RI concept seems to be most useful for revealing the compounds which mass spectra are like those of the target analytes. In the case of trialkyl thiophosphates these are the products of their partial hydrolysis – dialkyl thiophosphates (RO) 2 PS-OH. These acidic esters could not be analyzed using the GC techniques due to the presence of active hydrogen atoms in their molecules. Keywords : Trialkyl thiophosphates, high performance liquid chromatography, mass spect­ro­metry, electrospray ionization, retention indices, homologous increments of retention indices, revealing dialkyl thiophosphates in reaction mixtures. DOI: http://dx.doi.org/10.15826/analitika.2019.23.3.012 (Russian) 1 Igor G. Zenkevich, 1 Tatiana I. Pushkareva, 2 Georgy V. Karakashev 1 St. Petersburg State University, Universitetskii prosp., 26, St. Petersburg, 198504, Russian Federation 2 Research Institute of hygiene, occupational pathology, and human ecology, Federal Medico-Biological Agency, p/o Kuzmolovsky, Vsevolozhsky District, Leningrad reg., 18866, Russian Federation