Improving the organic solvents purity for microextraction preconcentration of impurities

Abstract

The purity of different industrially produced extractants, such as hexane, n-octane, carbon tetrachloride, and ethanol, was studied using gas chromatography-mass spectrometry and gas chromatography. It was shown that the most characteristic impurities in these extractants were volatile organochlorine compounds ( LHS ) and hard volatile esters of o-phthalic acid ( o -phthalates ). The impurity content of these substances in extractants could reach tens of mg/l. Based on the calculation of the distribution coefficients of impurities in the “liquid-vapor” system, the methods of Rayleigh distillation and rectification were proposed for removing the impurities from the extractants. Gas chromatographic mass spectrometric and gas chromatographic analysis of purified extractants showed that the effective removal of impurities of o-phthalic acid esters was possible using the Rayleigh distillation during the distillation of extractants at an evaporation rate of no more than 6·10 –4 ml·cm –2 ·s –1 . This allowed obtaining a volume of extractant enough to carry out 50-55 microextractions in 5 minutes. The effective removal of volatile LHS was achieved by a multi-stage distillation method - rectification. The concentration of impurities of the investigated substances in the purified extractants did not exceed 10 –3 –10 –5 mg/l. The liquid-phase microextraction preconcentration with the use of purified extractants decreased the detection limits of LHS and o-phthalates in the water to 2∙10 -7 -1∙10 -5 and 4·10 -6 ‒1·10 -5 mg/l, respectively. Keywords: microextraction preconcentration, rectification, Rayleigh distillation, detection limits, extractant, gas chromatography, gas chromatography mass spectrometry (Russian) DOI: http://dx.doi.org/10.15826/analitika.2019.23.1.008 V.A. Krylov 1 , P.V. Mosygin 1 , L.V. Smirnova 1 , S.A. Bulanova 1 , I.A. Zhituhina 1 , G.V. Pushkarev 2 1 N.I. Lobachevsky Nizhny Novgorod State University, Russian Federation, 603950, Nizhny Novgorod, Gagarin pr., 23 2 Joint –Stock Company «Scientific - Production Enterprise «Salyut», Russian Federation, 603950, Nizhny Novgorod, Larina Str., 7