Openlab cdc 2013

The system consisted of an Agilent 1100 Series high-performance liquid chromatograph coupled to a micro vacuum degasser and a fluorescence detector (HPLC-FLD) (Agilent Technologies, Barcelona, Spain) with excitation and emission wavelength of 365 and 435 nm, respectively. Separation was carried out on a column Ace 5 C18, 250 × 4.6 mm, 5 µm particle size (Análisis Vínicos, Ciudad-Real, Spain). A manual injector system equipped with a 100 µL injector loop and a 250 µL syringe was used. The isocratic mobile phase for aflatoxins was methanol/acetonitrile/water (40:10:50, v/v/v), pumped with a flow rate of 1.0 mL/min. The retention times (min) for the analyzed aflatoxins were 9.95 for AFG2, 11.00 for AFG1, 13.51 for AFB2, and 15.09 for AFB1 (Supplementary Material Figure S1). The fluorescence intensity of AFB1 and AFG1 was improved with postcolumn photochemical derivatization using a photochemical reactor for enhanced detection (PHRED) (LCTech UVE, Dorfen, Germany) set at 254 nm. The identification and quantification of aflatoxins in the culture broth samples were performed using the software package OpenLAB CDC 2013 (Agilent Technologies, Barcelona, Spain).

The identification and quantification of aflatoxins in the samples were performed using the software package OpenLAB CDC 2013 (Agilent Technologies, Barcelona, Spain). A sample was determined as positive when the result was above the limit of detection. A value of zero was assigned to the samples that presented aflatoxin concentration values lower than the LOD (limit of detection). For those samples that presented concentration values between LOD and LOQ, their numerical value was used.
Descriptive and comparative statistical analysis of the results were carried out using the IBM SPSS Statistics Base program, version 22 (Armonk, NY, USA). The data on aflatoxin B1 in feed and aflatoxin M1 in milk were not normally distributed after checking by Shapiro–Wilk test. Therefore, non-parametric tests were used for comparative statistics between factors. Firstly, Mann–Whitney U test was used so as to know if there were significant effects of feeding systems (unifeed vs. compound feed), season (spring vs. winter), and year (2015 vs. 2016) on aflatoxin levels in both feed and milk samples as well as in transfer ratios. Differences between the four sampling provinces in which the dairy farms were located were determined by Kruskal-Wallis test. All tests were carried out at a significance level of 0.05.