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Rapid And Sensitive Determination Of Chlordiazepoxide And Paraquat In Drinking Water By UPLC/MS(MS)
- Oct 30, 2018 -

Excerpt from Water Corporation

Brief Introduction

Quaternary ammonium salt herbicides paraquat and diazone are widely used worldwide to control leaves and weeds. In the United States, paraquat was used up to 4 million pounds in 2002, and dioxone was used up to 20,000 pounds. Because of the potential toxicity of these compounds to wildlife and humans, regulators have imposed strict monitoring of groundwater and surface water samples to ensure that the levels of such substances remain meet safety standards. Regulatory limits range from 100 ng/L(Europe) to 20 g/L(us). 

This application summary introduces an optimized method for the determination of paraquat and chlordiazepoxide in drinking water. This method first USES Oasis WCX small column to conduct SPE purification of the sample, and then carries out rapid, sensitive UPLC/MS (MS) analysis.

Oasis WCX is a kind of adsorbent with mixed mode of weak-positive anion exchange and reverse phase, which can effectively separate paraquat and diazole from aqueous samples. In a previous article, we have explored the method 2 of using Oasis WCX for solid phase extraction of quaternary ammonium salt before HPLC/MS determination. The new UPLC method introduced in this paper only needs half the analysis time of HPLC method. In addition, we have improved the SPE method. The previous scheme used trifluoroacetic acid, a perfluorinated compound that is toxic and a persistent organic pollutant, while the new SPE scheme used formic acid as an acidic modifier of SPE eluent.

Advantages of Application 

The weak cation exchange - inverting hybrid adsorbent used by Oasis WCX SPE column is an ideal candidate for retaining quaternary ammonium compounds such as diazole and paraquat.

In combination with ACQUITY BEH HILIC chromatographic column, UPLC/MS(MS) analysis was performed, which was not only fast and sensitive, but also free of ion pair reagents which were not conducive to obtaining a good mass spectrum response.

The LOQ of this method is 40 ng/L(PPT).


Oasis WCX SPE is an effective SPE product that can separate paraquat from diazole in water samples. SPE scheme of paraquat/diazole can effectively enrich and purify paraquat/diazole in various drinking water samples.

UPLC/MS(MS) method is fast, sensitive and does not require ion-pair reagents. Methods the recovery rate was above 80%, and the ion inhibition effect of all water samples measured in this study was below 30%.