Development and evaluation of a dispersive liquid-liquid microextraction based test method for quantitation of total anionic surfactants: advantages against reference methods

A small-scale, simple, and rapid dispersive liquid-liquid microextraction (DLLME) procedure in combination with fiber optic-linear array detection spectrophotometry (FO-LADS) with charge-coupled device (CCD) detector has been developed, with benefits from the use of a micro-cell. The official reference methods (ASTM D2330 - 02, ISO 7875-1), which require tedious procedures, were replaced with a modified method. The new method provides a major reduction in sample size, elimination of the use of expensive glassware, and a decrease in the quantity of chloroform used, as well as increased sensitivity. Our method requires only one twentieth of the sample (5.0 mL), and less than one three-hundredth of microextraction solvent (chloroform = 138 mu L). It provides a faster analysis time than official analytical methods (less than one minute). The calibration curve was linear in the range of 6 -80 mu g g L-1 of sodium dodecyl sulfate (SDS) with a correlation coefficient (r) of better than 0.99 and the LOD was 2 mu g L-1. The repeatability of the proposed method (n=7) was found to be 4.5% and 3.6% for the concentrations of 0.03 and 0.07 mg L-1, respectively. The enrichment factor was found to be 75 for SDS.