Determination of herbicides in water samples by spectroscopic techniques

Abstract

Atrazine and paraquat are widely used to control weeds in the agricultural areas. The residue of herbicides can harm the environment and living things. In this research, nanoporous carbon derived from melamine based polybenzoxazine or NPC-PBZ-m was used as an adsorbent for atrazine and paraquat analysis. NPC-PBZ-m was synthesized by sol-gel and pyrolysis processes. The characteristics of sorbent were investigated by FTIR, BET, XPS, and FE-SEM. For atrazine determination, NPC-PBZ-m pre-concentration column combined with a colorimetric detection based on a Konig’s reaction and HPLC-UV at 222 nm were developed. The parameters affecting the adsorption performance were optimized. The reusability of the NPC-PBZ-m column was over 8 cycles. For colorimetric analysis, the orange-red polymethine compound was developed by using 6 (%w/v) of p-Anisidine. The HPLC-UV and colorimetric analysis showed a good linearity in the ranges of 5–30 µg/L and 10–30 µg/L with correlation coefficients of 0.9988 and 0.9979, respectively. The method detection limit (MDL) and method quantitation limit (MQL) of HPLC-UV analysis method were 1.05 µg/L and 3.45 µg/L while UV-Vis analysis method were 2.26 µg/L and 7.46 µg/L, respectively. The recoveries from spiked samples for HPLC analysis was in the range of 98–105% while colorimetric analysis was in the range of 100–107%. Moreover, NPC-PBZ-m combined with colorimetric analysis using glucose reagent showed a good performance for paraquat determination. The NPC-PBZ-m was activated with 0.1 M KOH before use. The suitable ratio between weight of NPC-PBZ-m and the volume of 0.1 M KOH was 1:1 (% w/v). For the desorption step, 2 mL of the 70:30 (% v/v) of 1 M HCl:MeOH was used. The dynamic range was found to be from 0.05–1 µg/mL with correlation coefficient of 0.986.