A simple and fast method for chlorsulfuron and metsulfuron methyl determination in water samples using multiwalled carbon nanotubes (MWCNTs) and capillary electrophoresis

A new method to determine metsulfuron methyl (MSM) and chlorsulfuron (CS) in different water samples was developed. It consists in a solid phase extraction (SPE) procedure using multiwalled carbon nanotubes (MWCNTs) as sorbent material in combination with capillary zone electrophoretic determination. To carry out the pre-concentration step, a simple flow injection system was developed and optimized. Thus, 250 μL of aqueous solution containing methanol 50% (v/v) and acetonitrile 2% (v/v) as eluent, 10 mL of sample and a flow rate of 1.15 mL min−1 were selected. The CE variables also were optimized. A rapid determination and good resolution of two herbicides were obtained within 9 min using a simple electrophoretic buffer (50 mmol L−1 sodium tetraborate with 3% of methanol, pH = 9.0). Under the optimum conditions, the calibration curves were linear between 0.5 and 6 μg L−1 for MSM and CS with R2 = 0.995 and 0.997, respectively. The repeatability of the proposed method, expressed as relative standard deviation (RSD), varied between 4.1% and 5.4% (n = 10) and the detection limits for MSM and CS were 0.40 and 0.36 μg L−1, respectively. Good results were achieved when the proposed method was applied to spiked real water samples. The recoveries percentages of the two analytes were over the range 86–108%.