An isotope internal standard coupled with high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) method was established for the simultaneous determination of four bisphenols (bisphenols A, B, F and S) in infant foods. Samples were extracted with a mixture of ethyl acetate and cyclohexane and detected by HPLC-MS/MS in the multi-reaction monitoring mode. Under the optimized conditions, the four bisphenols showed good linearity in the range of 5.0–200.0 μg/L with R2 larger than 0.9970. The detection limit of the method was 1.5 μg/kg. The mean recoveries of negative samples spiked at three concentration levels (5.0, 10.0 and 50.0 μg/L) were in the range of 84.0％–106.5％with relative standard deviations (RSDs, n = 6) ranging from 1.6％ to 6.4％. The proposed method had the advantages of high sensitivity, good purification efficiency and quantitative accuracy and it was suitable for the detection of bisphenols in infant foods.

An isotope internal standard coupled with gas chromatography-mass spectrometry (GC-MS) method was established for the simultaneous determination of four chloropropanol esters (3-chloro-1,2-propanediol, 2-chloro-1,3-propanediol, 1,3-dichloro-2-propanediol and 2,3-dichloro-2-propanol ester) in infant formula milk powder. Samples were dissolved and extracted withn-hexane, and then the extract was hydrolyzed by sodium methoxide in methanol, purified on a Florisil solid phase extraction column, derivatized with heptafluorobutyryl imidazole, detected by GC-MS in the single ion monitoring mode, and quantified by the internal standard method. Under the optimized conditions, all four chloropropanol esters showed good linearity in the range of 0.05–1.00 mg/L withR2 larger than 0.997. The detection limit of the method was 0.015 mg/kg. The mean recoveries at three spiked concentration levels (0.05, 0.10 and 0.50 mg/kg) were in the range of 85.9%–102.1% with relative standard deviations (RSDs,n = 6) ranging from 2.4% to 5.6%. The proposed method showed the advantages of high sensitivity, good clean-up efficiency and high accuracy, and it was suitable for the detection of chloropropanol esters in infant formula milk powder.

A method for the simultaneous determination of Pb, Cr and Hg in milk was developed by microwave digestion combined with inductively coupled plasma mass spectrometry (ICP-MS). The sample preparation procedure, the ICP-MS parameters, the internal standard and the monitor isotope were optimized. The results showed that the digestion temperature was 180 ℃. A mixed solution of 10 μg/L 72Ge and 209Bi was selected as the internal standard to eliminate the matrix effect, and 200 μg/L Au was added to the solution to eliminate the memory effect of Hg. 208Pb, 52Cr and 202Hg were monitored with ICP-MS to determine Pb, Cr and Hg, respectively. Under the optimal conditions, detection limits of 5.0 (Pb), 1.0 (Cr) and 0.5 (Hg) μg/kg were obtained. The contents of Pb, Cr and Hg in 40 batches of commercial milk were low. The detection values were smaller than 0.011 mg/kg for Pb and smaller than 0.031 mg/kg for Cr. Only 1 sample was found to contain Hg, and the detection value was 0.008 mg/kg.

A method for the simultaneous determination of twelve elements (K, Ca, Na, Mg, Cu, Fe, Mn, Zn, Al, Pb, Cr and Cd) in milk powder for infants and young children by inductively coupled plasma atomic emission spectrometry (ICPAES) was established. Instrumental parameters were optimized. Standard curves for these twelve elements were obtained with correlation coefficients greater than 0.9995. The detection limits of the ICP-AES method for these elements were in the range of 0.02 to 5 mg/kg, and the spiked recoveries were 87.5%–106.3% with RSD lower than 5% (n = 6). This method was rapid and accurate and could be used for quality control and safety evaluation of milk powder.