An ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method for the simultaneous quantitative determination of fumonisin B1 (FB1), fumonisin B2 (FB2) and fumonisin B3 (FB3) residues in milk powder and milk has been established. The samples were extracted with methanol-acetic acid (98:2, V/V), diluted, cleaned up by immunoaffinity chromatography (IAC), and blown to dryness under nitrogen. The residue was re-dissolved and detected using an electrospray ionization source (EIS) in the positive ion mode with multiple reaction monitoring (MRM) and quantitative analysis was performed by the isotope-labeled internal standard method. The limit of quantification was 10 μg/kg for FB1, FB2 and FB3 in milk powder and milk. The recoveries at spiked concentration levels of 10–400 μg/kg were 92.8%–107.5%, with relative standard deviations (RSD) of 2.0%–4.3%. The matrix effects were 96.25%–122.84%. This method was characterized by short analysis time and was suitable for the determination of fumonisin residues in different dairy products.

The objective of this study was to establish a method for detecting the residue of dicamba in cow milk by high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). The sample was extracted with 0.5% formic acid in acetonitrile, and the extract was purified by sodium chloride salting out, and separated on an Acquity UPLC BEH C18 column (100 mm × 2.1 mm, 1.7 μm) by gradient elution using a mobile phase composed of acetonitrile and 0.01% formic acid aqueous solution. Identification and quantification were achieved using an electrospray ionization source in the negative ion mode with multiple reaction monitoring (MRM). Under optimized pretreatment and instrumental conditions, good linearity was observed in the concentration range of 5.0–250.0 μg/L with correlation coefficient (r) more than 0.999. The limit of detection (LOD) and limit of quantification (LOQ) of the proposed method were 5 and 10 μg/kg, respectively. The recoveries of dicamba at spiked concentration levels of 10, 20 and 200 μg/kg were 104.3%, 101.5% and 96.2% with relative standard deviations (n = 6) of 3.0%, 2.0% and 1.5%, respectively. This method is simple, accurate, repeatable, and suitable for the rapid detection of dicamba in milk.

A high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) method was established for the determination of nonylphenol in milk powder. Samples were extracted with acetonitrile and cleaned up with a solid phase extraction column. The analytes were separated on a Waters ACQUITY UPLC BEH C18 column (2.1 mm × 50 mm, 1.7 μm), detected by electrospray ionization in the multiple reaction monitoring (MRM) mode, and quantified by an external standard method. The results showed that good linearity was observed in the concentration range of 1–200 ng/mL (R2 > 0.99). The limit of detection（LOD, RS/N = 3）was 2 μg/kg and the limit of quantitation (LOQ, RS/N = 10）was 5 μg/kg. The recoveries at different spiked levels were between 81.10% and 107.39% with relative standard deviation (RSD) ranging from 1.97% to 9.73%. This method has the advantages of accurate results, small background interference, simple operation, good stability and short pretreatment time, and is useful for the detection of nonylphenol in milk powder.

A new method for detecting five aflatoxin residues in raw milk was presented using micellar electrokinetic capillary chromatography with a diode array detector (MECC-DAD). The specificity of MECC-DAD was evaluated in comparison with that of high-performance liquid chromatography with a fluorescence detector (HPLC-FLD). In the MECC-DAD method, samples were cleaned up by immunoaffinity column chromatography before separation on an uncoated fused-silica capillary column using 7.5 mmol/L borate buffer with 30 mmol/L sodium dodecyl sulfonate (pH 8.5) and 5% acetonitrile and the detection wavelength was set at 214 nm. In the HPLC-FLD method, samples were separated on a C18 column (150 mm × 4.6 mm, 5 μm) by gradient elution using a mobile phase consisting of acetonitrile and water after being cleaned up by immunoaffinity column chromatography. The analytes were detected by a fluorescence detector at 360 nm excitation wavelength and 440 nm emission wavelength. Results showed that MECC-DAD gave smoother and sharper peaks that were more symmetrical without tailing. The limits of detection of MECC-DAD and HPLC-FLD were 0.182–1.669 and 0.014–0.058 μg/L, both meeting the requirements for the determination of aflatoxin residues in raw milk. The precision of HPLC-FLD was somewhat higher than that of MECC-DAD. The recoveries of MECC-DAD and HPLC-FLD were 80.3%–137.0% and 79.6%–134.0%, respectively. When the two methods were applied to the same commercial milk samples, the P value for the deviation between the quantitative results obtained was 0.900, greater than 0.05, indicating no significant difference. In conclusion, MECC-DAD was simple, efficient and inexpensive, making it more suitable for the simultaneous determination of five aflatoxins in milk than HPLC-FLD.