Watersheds and Rivers Testing

Chen, M. S. et al. Microchemical Journal 208 (2025): 112546.

A novel, sensitive multi-residue method has been developed to monitor the presence of eight neonicotinoid insecticides and one major degradation product in river water and sediment samples. The method, employing a modified QuEChERS protocol, utilizes a reduced volume of acetonitrile containing 1% acetic acid for extraction and replaces the traditional cleanup step with concentration. This approach allows for lower quantitation limits, with water samples analyzed using LC-MS-MS, employing stable isotope internal standards (except for flonicamid, thiacloprid, and 6-CNA).

The method was validated for both water and sediment samples, with water sample limits of quantitation (LOQ) ranging from 10-40 ng/L and sediment sample LOQs from 125-250 ng/kg. The linear range for water samples was 10 to 1600 ng/L, and for sediment, it was 125 ng/kg to 40000 ng/kg, with accuracy and precision within 15%. Field analyses of 32 water and 32 sediment samples from agricultural regions in Taiwan revealed residues of imidacloprid (IMD) and 6-chloronicotinic acid (6-CNA) in water, and acetamiprid (ACE), IMD, and nitenpyram (NIT) in sediment samples. The developed method offers an efficient and reliable tool for monitoring neonicotinoid contamination in aquatic environments, with significant implications for environmental and public health monitoring.

Haq, Hameed Ul, et al. Water Resources and Industry 29 (2023): 100210.

A green and efficient natural deep eutectic solvent (NADES)-based ultrasound-assisted liquid-liquid micro-extraction (UA-LLME) method was developed for the extraction and determination of methyl violet dye in contaminated river water samples. Choline chloride–decanoic acid, a NADES, was employed as the extraction solvent, offering an eco-friendly alternative to conventional solvents. Key analytical parameters, including pH, deep eutectic solvent volume/phase ratio, tetrahydrofuran volume, sonication time, and temperature, were optimized to maximize extraction efficiency.

The method demonstrated excellent performance with a limit of detection (LOD) of 2.20 μg/L and a limit of quantification (LOQ) of 7.34 μg/L. The relative standard deviation (RSD) ranged from 2.35% to 3.21%, and linearity was established over a concentration range of 10–400 μg/L, with an enrichment factor of 20. For the optimized conditions, a 20 mL sample was extracted using 1.5 mL of NADES, 0.6 mL of tetrahydrofuran, with a pH of 6, and a sonication time of 2 minutes.

This optimized method was successfully applied to real river water samples, confirming its potential for routine environmental monitoring of methyl violet dye contamination, providing a reliable and sustainable approach for environmental analysis.

Fu, Yandi, et al. Microchemical Journal 175 (2022): 107100.

The detection of cathinones, a group of new psychoactive substances (NPSs), in environmental samples has become crucial for assessing community consumption and understanding their environmental impact. Since cathinones are often marketed as racemates but undergo stereoselective metabolism, monitoring their enantiomeric composition can provide more accurate estimates of drug consumption and aid in identifying synthetic pathways.

This study developed a highly selective method for enantiomeric determination of five cathinones in river water, using molecularly imprinted polymers (MIPs) synthesized with (1R,2S)-(–)-ephedrine or (1S,2S)-(+)-pseudoephedrine as templates, methacrylic acid as a functional monomer, and ethylene glycol dimethacrylate as a cross-linker. Solid-phase extraction (SPE) using the best-performing MIP sorbent was coupled with liquid chromatography-high-resolution mass spectrometry (LC-HRMS) for sensitive analysis.

The method was optimized for sample loading volume, pH, washing, and elution solutions, achieving recoveries between 67.6% and 83.2%, with matrix effects ranging from −5.5% to 1.8%. Detection limits were between 0.3 and 0.8 ng/L, with quantification limits ranging from 1.0 to 2.0 ng/L. Application to river water samples revealed the presence of methedrone and butylone at low concentrations. This method demonstrates the potential of MIPs for enantioselective analysis of environmental residues of cathinones.