[Influence of organic modifier on the retention behaviour in soil leaching column chromatography]

The relationship between capacity factors (k') of 55 nonionic compounds and broad methanol volume percentage (psi) of methanol-water eluent in soil leaching column chromatography (SLCC) was systematically investigated. The compounds consist of 11 chlorobenzenes, 14 alkylbenzenes, 22 polyphenyls and polycyclic aromatic hydrocarbons, and 8 pesticides. Reference soil was dry-packed into a stainless steel chromatographic column (10 mm i.d. x 100 mm) by a homemade pressurizing device, and isocratic methanolwater mixture with psi from 0.0 to 0.80 eluated through the column at a flow-rate of 1 mL.min-1. The column was thermostated at (25.0 +/- 0.1) degree C, and chromatographic peak was monitored by an online ultraviolet detector. The results show that both equations, log k' = log k'w + a psi + b psi 2(1) and log k' = log k'w - S psi (2), well fit the retention values. Equation (2) can be used practically due to few experimental data needed and simpler in formula. Explanation is also given for the existence of the carbon (or chlorine) number rule for two classes of homologous series (i.e. methylbenzenes, n-alkylbenzenes) and weak-polar chlorobenzenes in the SLCC process. The slope and intercept of the rule are also well correlated, and both decreases linearly with increasing eluent psi value.