Analysis of the petroleum components benzene, toluene, ethyl benzene and the xylenes in water by commercially available solid-phase microextraction and carbon-layer open tubular capillary column gas chromatography

In-tube solid phase micro-extraction–gas chromatography of volatile compounds in aqueous solution

“…At equilibrium (i.e., at 100% breakthrough) C s = 16.2 mg per 2750 nL = 5801 mg L 21 and C m is the concentration of the original toluene standard, i.e., C m = 20 mg L 21 . Thus, log K = 2.47, which is in good agreement with the K value determined by equation (2), log K ow and log K determined from SPME (Table 2) 8,[11][12][13][14][15][16] reported for the same temperature. Recovery of the sorbed toluene by back extraction should yield 81 mg L 21 of toluene (16.2 mg per 100 mL of hexane, diluted 1 : 1 with IS solution).…”

“…Equilibrium extraction conditions are established between the aqueous and stationary phase, so concentration and recovered solute should be linearly correlated. 11,16 According to chromatographic theory, the partition ratio, k, is [equation ( 3…”

Solid phase microextraction coupled to gas chromatography- mass spectrometry for the determination of the adsorption coefficients of triazines in soil

“…Initial experiments to optimise the chromatographic and detection conditions were carried out by direct injection of 1 ml of the standard mixture in acetonitrile. The oven temperature programme was: initial temperature 90 °C (held for 4 min), increased to 220 °C at 5 °C min 21 and then from 220 to 280 °C at 20 °C min 21 (final temperature held for 10 min). A column head pressure of 15 lb in 22 and an injector temperature of 250 °C were used.…”

“…where C soil is the concentration (mg kg 21 ) of the adsorbed chemical, C water is the concentration (mg n l 2n ) in the soil solution and n is a dimensionless exponent depending on the nature of the adsorbed chemical and the characteristics of the soil substrate. Typical values 9 of n for triazines in different soils are 1.00 ± 0.14 but at low pesticide concentrations the Freundlich adsorption isotherm described by eqn.…”

“…(2) can be considered linear (n = 1) and the K oc , calculated with eqn. (1) can be conveniently expressed in l kg 21 units. The most commonly used method for K oc evaluation is the so-called batch equilibrium method, in which a given amount of soil sample is equilibrated with a known volume of an aqueous solution containing a known amount of the investigated chemical(s).…”