Response surface methodology for optimization of cyanamide analysis by in situ derivatization and dispersive liquid–liquid microextraction

Abstract

Cyanamide is widely used for agricultural purposes; therefore, its residues can be found in water. A new method was developed for its quantification using in situ derivatization with 2,6-dimethyl-4-quinolinecarboxylic acid N-hydroxysuccinimide ester followed by dispersive liquid-liquid microextraction (DLLME) and high-performance liquid chromatography/fluorescence analysis. Multivariate chemometric techniques were successfully used to obtain the optimum conditions for direct derivatization and DLLME extraction. Derivatization parameters and DLLME extraction conditions were optimized by a two-step design, 2 k factorial design for screening, and central composite design for optimization. Best derivatization conditions were addition of 600 μL of derivatizing reagent, a temperature of 4 ºC, and pH 8.5, whereas for optimum extraction 800 μL of solvent, 30% NaCl conc. w/v, and pH 3.8 were chosen. The analytical performance of the method for routine analysis was evaluated. Excellent linearity was achieved from 10 to 200 μg L À1 with a correlation factor of 0.9996. Precision ranged from 3.5% to 5.5% for intraday assays and 8.5% to 8.6% for interday assays. The mean recoveries performed on water from different origins (ground, river, sea, tap, and mineral) at three levels of concentration (20, 75, and 200 μg L À1 ) ranged from 90.2% to 110.2%.Abbreviations: DMQC-OSu, 2,6-dimethyl-4-quinolinecarboxylic acid Nhydroxysuccinimide; DLLME, dispersive liquid-liquid microextraction; CCD, central composite design; IS, internal standard.