Determination of alkylphenols and their ethoxylates in liquid pesticide formulations by high-performance liquid chromatography

A simple method for simultaneous determination of alkylphenols (APs) and alkylphenol ethoxylates (APEOs) in six kinds of liquid pesticide formulations was developed using high-performance liquid chromatography with fluorescence detection (HPLC-FLD). Six kinds of liquid pesticide formulation samples (emulsifiable concentrate, aqueous solutions, emulsion in water, suspension concentrate, soluble concentrate, and microemulsion) were ultrasonically extracted with methanol. The extract was diluted with methanol and centrifuged. The supernatant was filtered through a polypropylene (PP) filter and then separated on an Agilent Poroshell C18 (4.6 mm×100 mm, 2.7 μm) chromatographic column using an isocratic elution program of V (methanol):V (acetonitrile):V (water)=75.5:6.5:18.0. Qualitative analysis was performed by HPLC-FLD, and the external standard method was used to quantify the concentrations of target analytes. The results showed that good linearity between the peak areas of APs and APEOs and their mass concentrations (R2>0.999 8) was obtained in the range of 0.05-10 and 0.1-20 mg/L. At three or four spiked levels (APs:0.5, 2, 5 mg/g; APEOs:1, 5, 25, 50 mg/g), the mean recoveries ranged from 73% to 110%, with relative standard deviations (RSD, n=5) of 0.6%-14.9% in those six kinds of liquid pesticide formulations. The limits of quantitation (LOQ) varied from 0.5 mg/g to 1 mg/g. This new method is convenient, rapid, accurate and suitable for the simultaneous determination of APs and APEOs in those six kinds of liquid pesticide formulations.