New method for determination of ochratoxin A in beer using zinc acetate and solid-phase extraction silica cartridges

A new method for the determination of ochratoxin A (OTA) in beer has been developed. The new method has been compared with a reference method currently accepted as AOAC official first action. The limits of detection and quantification of the proposed method were 0.0008 and 0.0025 ng/ml, respectively, while they were 0.0025 and 0.0075 ng/ml, respectively, in the AOAC method used as reference. The recovery levels in the 0.025-0.40 ng OTA/ml spiking range for the proposed and the reference methods were 80.6-87.6% and 78.2-83.8%, respectively. The relative standard deviations of recoveries were 2.6-7.5% for the proposed method and 0.7-6.1% for the reference method. Passing and Bablok regression analysis of recovery data obtained by the proposed method versus data obtained by the reference method on an OTA-spiked beer sample showed good correlation (r2 = 0.9993), while the slope and intercept were 1.049 and -0.0013, respectively. The advantage of the proposed method is the low cost of the materials used in sample preparation because expensive immunoaffinity columns are not needed to clean-up samples while it maintains or even increases the good performance of the reference method. The proposed method was applied to 69 beer samples from different geographic origins (national and imported) but purchased in the Spanish market. They were found to be contaminated with OTA in the range from 0.008 to 0.498 ng/ml (average: 0.070 ng/ml). Five samples surpassed the limit recommended by the European Union (0.2 ng OTA/g).