Method validation for the determination of ochratoxin A in green and soluble coffee by immunoaffinity column cleanup and liquid chromatography

Abstract

A method was validated for the determination of ochratoxin A (OTA) in soluble and green coffee. Performance parameters evaluated included selectivity, accuracy, intermediate precision, linearity, limit of detection, limit of quantitation, and ruggedness. The method was found to be selective for OTA in both matrices tested. Recovery rates from soluble coffee samples ranged from 73.5 to 91.2%, and from green coffee samples from 68.7 to 84.5%. The intermediate precision (RSDr) was between 9.1 and 9.4% for soluble coffee and between 14.3 and 15.5% for green coffee analysis. The linearity of the standard calibration curve (r(2)) was <0.999 for OTA levels of 1.0-20.0 μg/kg in coffee samples. The limit of detection was determined to be 0.01 ng of OTA on column, while the limit of quantitation was found to be 0.03 ng on column. The limit of quantitation is equivalent to 0.6 μg/kg in soluble coffee samples and 0.3 μg/kg in green coffee samples. The results of the ruggedness trial showed two factors are critical for soluble coffee analysis: the extraction method, and the flow rate of the mobile phase. For green coffee analysis two critical factors detected were the extraction method and the storage temperature of the immunoaffinity column.Five samples of soluble coffee and 42 of green coffee were analysed using the validated method. All soluble coffee samples contained OTA at levels that ranged from 8.4 to 13.9 μg/kg. Six of the 42 green coffee samples analysed (14.3%) contained OTA at levels ranging from 0.9 to 19.4 μg/kg. The validated method can be used to monitor OTA levels in Colombian coffee for export or for local consumption.

Development and validation of a method for detection and quantification of ochratoxin A in green coffee using liquid chromatography coupled to mass spectrometry

“…The Limit of detection (LOD) of OTA was 1.2 ng.g -1 . The LOQ value was higher than that determined using other methods in the literature (VENTURA et al, 2003;DIAZ et al, 2004). The LOD value was lower than that reported by other authors using HPLC-FLD methods (FURLANI;SOARES, 1999;LEONI et al, 2001).…”

Aspergillus and Ochratoxin A in Latin America

“…In another study, green and processed coffee samples from Colombia were evaluated and OTA contamination were not detected in any sample analyzed (<1 ng/g) (Magnoli et al 2008). In contrast, Diaz et al (2004) found that green and processed coffee samples from Colombia were highly contaminated. The levels detected range from 0.90 to 19.40 ng/g and from 8.40 to 13.90 ng/g for green and processed coffee, respectively.…”

Development and validation of a method for the analysis of Ochratoxin A in roasted coffee by liquid chromatography/electrospray-mass spectrometry in Tandem (LC/ESI-MS/MS)

“…An acceptable fit from the matrix-matched calibration curve showed a random pattern of residues in the working range (Figure 3), indicating a system free of bias confirming the method's linearity. 33 The value of Cochran's test was 0.58 (C calc ), lower than the value of 0.68 (C tab ) for the 5 levels of matrix-matches calibration curve with three replicates, proving the homoscedasticity. Figure 4 shows a chromatogram of spiked roasted coffee in 3.0 ng g -1 and an example for blank roasted coffee.…”

“…Coelution problem of interfering compounds and retention time shifts could lead to erroneous positive or negative results can be overcome by structural elucidation provided by coupling of LC and mass spectrometry (MS). 33 In general, and no matters the applied detection technique, there is a need for a careful sample clean up. The extract is usually purified by solid-phase extraction, or by using immunoaffinity absorbent materials, or by a combination of both.…”