An improved method for analyzing chlormequat and mepiquat in source waters by solid-phase extraction and liquid chromatography–mass spectrometry

A liquid chromatography–mass spectrometry (LC–MS) method for the identification and quantification of chlormequat (CQ) and mepiquat (MQ) in source waters with high sensitivity and specificity was established using WCX cartridges (150 mg/6 mL) for pre-concentration of the samples and using the CAPCELL PAK CR 1:4 (2.0 mm × 150 mm 5 μm, SCX:C18 = 1:4) column containing strong cationic exchange resins and C18 for separation. The method could solve the problem for pre-concentrating ionic compounds from water samples and avoid the MS instrument fouling problem accompanied with the use of ion-pair reagents. After the optimization of analytical conditions, quantification was achieved in the positive electrospray ionization mode using selected ion monitoring. The samples were analyzed with multi-channel mode with quantification performed at 30 V cone voltage to ascertain the sensitivity and qualitative analysis performed at 60 V cone voltage simultaneously. The method detection limits (MDLs) of CQ and MQ in source water were determined to be 14 and 22 ng L−1. Finally, the method was used to quantify CQ and MQ in several source waters, which gave a level ranging from below the quantitation limit to 28 ng L−1.