1983 Volume 32 Issue 12 Pages 723-729
A method for the determination of trace amount of LAS (linear-alkylbenzenesulfonate) in environmental waters is described, in which LAS is converted to its sulfonyl-fluoride (LAS-F) and measured by gas chromatograph equipped with electron capture detector (ECD-GC). LAS was extracted into chloroform as the ion-pair with methylene blue and the extract was evaporated to dryness. One gram of phosphorus pentachloride and 2ml of hexane were added to the residue and hexane was allowed to reflux on an oil bath at (120130)°C for effecting the sulfonylchlorination. Then, sulfonyl-chloride of LAS (LAS-Cl) was extracted with hexane, and the extract was applied to a Silicagel column. After 100ml of hexane was poured to the column, LAS-Cl was eluted by 100ml of hexane: benzene (94:6) from the column, and the eluate was evaporated to dryness. To the residue were added 0.5 g of potassium fluoride and 2ml of hexane, and hexane was allowed to reflux in an oil bath at (120130)°C for effecting the fluoro-substitution. LAS-F was extracted with hexane and measured by ECD-GC using 2% OV-17 on Gas-Chrom Q as the GC column packing. The proposed method is superior to the method measuring LAS as LAS-Cl in the following point: 1) Neither thermal decomposition nor column adsorption were observed for LAS-F, 2) improved reproducibility was obtained, and 3) the former is 50 times of sensitivity of the latter. Recovery of LAS in river water was 89% of averaged recovery (coefficient of variation: 3.3%). LAS could be detected in all of 22 samples of river water. A correlation among the analytical results of these river waters by the proposed method (GC value) and methylene blue method (MB value) was showed by the equation of
GC value=0.730×MB value -0.015 (correlation coefficient 0.963).
