Suitability of PSA (Primary Secondary Amines) and Z-Sep as clean-up sorbents in AOAC official method 2007.01 for analysis of trifloxystrobin and CGA 321113 residue in dragon fruit, star fruit and watermelon

N. Chai Keong, H. Siti Hajar and A.M. Khairatul 

Abstract

Two types of clean-up sorbents, namely PSA (Primary Secondary Amines) and Z-Sep were tested for reliability in AOAC official method 2007.01 for generating accurate results for analysis of trifloxystrobin and CGA 321113 (trifloxystrobin metabolite) in dragon fruit, star fruit and watermelon. A known amount of both analytes was fortified onto separate analytical portions of dragon fruit, star fruit and watermelon respectively, followed by an extraction clean-up procedure using either PSA or Z-Sep. The extracts were analysed by Liquid Chromatography Tandem Mass Spectrometry (LCMS-MS) analysis. Measured concentrations were compared with a theoretical fortified value in order to determine its recovery. Results indicated that both PSA and Z-Sep generated acceptable recovery of trifloxystrobin ranging from 76.8 – 107.7%. However, when PSA alone was used as the clean-up material, significant loss of CGA 321113 was deduced from low average recovery values in dragon fruit (47.1%), star fruit (57.4%) and watermelon (31.7%) for fortification level of 0.01 mg/kg. For higher fortification level of 0.1 mg/kg, lower average recovery values of CGA 321113 were reported in dragon fruit (23.9%), star fruit (15.4%) and watermelon (14.6%). In all the studied fruits, Z-Sep showed recoveries of CGA 321113 within the range of 80.4 – 124.2% at 0.01 and 0.1 mg/kg fortification levels indicating no significant loss during the clean-up procedure. Based on two types of residue definitions (MRL compliance and dietary risk assessment), it can be concluded that for analysis of CGA 321113, Z-Sep should be used as the clean-up sorbent in the clean-up procedure.

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