Ultra‐trace level determination of diquat and paraquat residues in surface and drinking water using ion‐pair liquid chromatography with tandem mass spectrometry: A comparison of direct injection and solid‐phase extraction methods

• Published in: Journal of separation science Vol. 37; no. 20; pp. 2900 - 2910
• Main Authors: Oh, Jin‐Aa, Lee, Jun‐Bae, Lee, Soo‐Hyung, Shin, Ho‐Sang
• Format: Journal Article
• Language: English
• Published: Weinheim Wiley-VCH 01.10.2014; Blackwell Publishing Ltd; Wiley; Wiley Subscription Services, Inc
• Subjects: Analysis methods; Analytical chemistry; Applied sciences; Balancing; Chemistry; Chromatographic methods and physical methods associated with chromatography; Chromatography; detection limit; Diquat; Direct injection method; Drinking water; Drinking water and swimming-pool water. Desalination; Environmental water; Exact sciences and technology; Extraction; herbicide residues; Liquid chromatography; Liquid chromatography with tandem mass spectrometry; Mass spectrometry; Monitoring; Natural water pollution; Other chromatographic methods; Paraquat; Pollution; solid phase extraction; Surface water; tandem mass spectrometry; Water pollution; Water treatment and pollution; Drinking water; Solid phase extraction; Tandem mass spectrometry; Chemical analysis; Organic cation; Direct injection method; Systemic; Mobile phase; Ion interaction chromatography; Liquid chromatography with tandem mass spectrometry; Electrospray; Chemical enrichment; Freshwater environment; Pyridinium compounds; Sample preparation; Stream; Quantitative analysis; Direct injection; Trace analysis; Coupled method; Pesticides; Ion pair; Herbicide; Reversed phase chromatography; Environmental water; Surface water; Water quality; Paraquat; Diquat; Water pollution; River water; Comparative study
• ISSN: 1615-9306; 1615-9314
• DOI: 10.1002/jssc.201400551

Direct injection and solid‐phase extraction methods for the determination of diquat and paraquat in surface and drinking water were developed using liquid chromatography with tandem mass spectrometry. The signal intensities of analytes based on six ion‐pairing reagents were compared with each other, and 12.5 mM nonafluoropentanoic acid was selected as the best suited amongst them. A clean‐up method was developed using Oasis hydrophilic–lipophilic balance; this was compared to the direct injection method, with respect to limits of detection, interference, precision, and accuracy. Limits of quantification of diquat and paraquat were 0.03 and 0.01 μg/L using the direct injection method, and 0.002 and 0.001 μg/L using the hydrophilic–lipophilic balance method. When the hydrophilic–lipophilic balance method was used to analyze target compounds in 114 surface water and 30 drinking water samples, paraquat and diquat were detected within a concentration range of 0.001–0.12 and 0.002–0.038 μg/L in surface water, respectively. When the direct injection method was used to analyze target compounds in the same samples, the detected concentrations of paraquat and diquat were within 25% in samples being >0.015 μg/L using the hydrophilic–lipophilic balance method. The liquid chromatography with tandem mass spectrometry method using direct injection can thus be used for routine monitoring of paraquat and diquat in surface and drinking water.