Development and validation of an analytical method for the analysis of Sterigmatocystin in roasted coffee beans and black pepper using liquid chromatography-tandem mass spectrometry

Sterigmatocystin (STC) is a toxic and potentially carcinogenic fungal toxin found in a variety of food commodities. This study describes the development of an analytical method to determine STC in roasted coffee beans and black pepper using ultra performance liquid chromatography (UPLC) coupled with triple quadrupole tandem mass spectrometry (MS/MS). ¹³C₁₈-STC was used as internal standard. STC was extracted with a mixture of acetonitrile/water, diluted with a buffer, followed by purification with a solid-phase extraction and an immunoaffinity column prior to the UPLC-MS/MS analysis. Two multiple reaction monitoring (MRM) transitions were employed, one for quantification and one for confirmation of STC. The UPLC-MS/MS analytical method was validated with respect to selectivity, linearity, sensitivity, accuracy, precision, recovery, and stability. Calibration curves were linear over a concentration range 25-2,500 pg mL^-1 with correlation coefficients (r) > 0.998. The method limit of quantification for STC in roasted coffee beans and black pepper was 0.10 μg kg^-1. The accuracy and precision of the analytical method were acceptable within 15% at all quality control levels. This method was suitable to determine STC levels because of its selectivity, precision, and accuracy. The method was successfully applied to roasted coffee beans and black pepper samples.