Aflatoxin mix

Citrinin (solution in acetonitrile 100 μg mL⁻¹), ochratoxin A (solution in acetonitrile 100 μg mL⁻¹) and aflatoxin mix containing AFB1 and AFB2 (2 μg mL⁻¹ in acetonitrile), AFG1 and AFG2 (0.5 μg mL⁻¹ in acetonitrile) were obtained from Romer Labs (Tulln, Austria). Monacolin K (25 mg), monacolin K acid (5 mg) and simvastatin (10 mg) were purchased from Vinci Biochem S.R.L. (Florence, Italy).
HPLC-grade ethanol, and acetonitrile were purchased from Sigma-Aldrich (Taufkirchen, Germany); bidistilled water was obtained using Milli-Q System (Millipore, Bedford, MA, USA). MS-grade formic acid from Fisher Chemical (Thermo Fisher Scientific Inc., San Jose, CA, USA) was also used.

HPLC analysis was carried out based on AOAC Official Method 2005.08 (AOAC,2006) with Photochemical Reactor for Enhanced Detection (PHRED) for post-column derivatisation. A Cecil-Adept Binary Pump HPLC (Cambridge, UK) was joined with Shimadzu 10AxL fluorescence detector (Shimadzu Corporation, Tokyo, Japan) (Ex: 360 nm, Em: 440 nm) with Sunfire^® C18 Column (150 × 4.60 mm, 5 um). The mobile phase used was methanol: water (40:60, v/v) at a flow rate of 1 mL/min with column temperature maintained at 40 °C. LCTech UVE (Dorfen, Germany) was used for post-colum photochemical derivatisation. The aflatoxin mix (G₁, G₂, B₁, B₂) standards (ng/g) of 5.02 ng/µL in acetonitrile from Romer Labs^® was used for matrix-based calibration. Aflatoxins in the samples were detected by using the retentions of the standard solution run and quantification was conducted using the calibration of curves of each respective toxin. Quality assurance for established by checking for precision and trueness by spiking blank samples with aflatoxins standard (Table 3). Blank samples were run periodically confined to the absence of aflatoxins. The coefficient of variation obtained for replicates was less than 15%.