Determination of N-methylcarbamate insecticides in water samples using dispersive liquid-liquid microextraction and HPLC with the aid of experimental design and desirability function

A rapid and simple method for the extraction and preconcentration of N-methylcarbamates (NMCs) (carbofuran, carbaryl and promecarb) in water samples using dispersive liquid-liquid microextraction (DLLME) using chemometrics was developed. Influence variables such as volume of extracting (CHCl3) and dispersing solvents (ACN), pH and ionic strength, extraction time and centrifugation time and speed were screened in a 2(7-4) Plackett-Burman design was investigated. The significant variables were optimized by using a central composite design (CCD) combined with desirability function (DF). At optimum conditions values of variables set as 126 mu L chloroform, 1.5 mL acetonitrile, 1 min extraction time, 10 min centrifugation at 4000 rpm min(-1), natural pH, 4.7% (w/v) NaCl, the separation was reached in less than 14 min using a C-18 column and an isocratic binary mobile phase (acetonitrile: water (50:50, v/v)) with flow rate of 1.0 mL min(-1). At optimum conditions method has linear response over 0.001-10 mu g mL(-1) with detection limit between 0.0001 and 0.0005 mu g m L-1 with relative standard deviations (RSDs) in the range 2.18-5.06% (n = 6). (C) 2011 Elsevier B.V. All rights reserved.