An inductively coupled plasma-tandem mass spectrometry (ICP-MS/MS) method was established for the analysis of 26 inorganic elements in dairy products. Under MS/MS conditions, the 26 elements were detected in the no gas, collision gas (He) or reaction gas (H2, O2, NH3/He) mode and the optimal mode was selected for each of the elements. The results showed that calibration curve with good linearity was obtained for each element in the appropriate detection mode with a correlation coefficient greater than 0.999 0. The detection limits of the 26 inorganic elements ranged from 0.000 033 61 to 0.043 71 mg/kg. The spiked recoveries were between 95.50% and 104.21%, with a relative standard deviation (RSD) ≤ 3.94% (n = 11). The contents of Na, Mg, K, Ca, P, Fe and Zn were higher and the contents of the heavy metal elements Cr, As, Cd and Pb were lower in six kinds of dairy products, all of which were lower than the national standard limits. The method was characterized by simple pretreatment, high sensitivity, low limit of detection and high accuracy and could be used for the detection of inorganic elements in dairy products.

An analytical method was established for the determination of the residues of 11 sulfonamides and five quinolones in infant formula milk powder using ultra-performance liquid chromatography tandem triple quadrupole mass spectrometry (UPLC-MS/MS). Acidified acetonitrile was used for sample extraction and the extract was purified and concentrated by solid phase extraction (SPE) using a PRiME hydrophilic lipophilic balance (HLB) column, then separated on an XBridge BEH C18 column, detected in the positive ion mode using an electrospray ionization source, and quantified by the calibration curve method with matrix matching. The calibration curves of all analytes showed a good linear relationship in the concentration range of 2–100 ng/mL with correlation coefficients greater than 0.995 0. The limit of detection (LOD) and the limit of quantification (LOQ) were 0.1-0.2 and 0.3-0.5 μg/kg, respectively. Recoveries for spiked samples were between 84.8% and 108.0%, with relative standard deviations (RSDs) between 0.36% and 5.41%. The proposed method is simple, efficient, reliable and sensitive.

An ultra-high performance liquid chromatography tandem triple quadrupole mass spectrometry (UPLC-MS/MS) method was established for the determination of six quaternary ammonium disinfectant residues in milk-containing food for special medical purposes. The sample was extracted with 80% acetonitrile in water and the extract was separated on a RRHD Eclipse Plus C18 column, detected in the positive ion mode using an electrospray ionization source with multiple reaction monitoring (MRM), and quantified by matrix-matched standard calibration. The calibration curves for the six quaternary ammonium disinfectants was linear in the concentration range of 0.1–5.0 ng/mL with correlation coefficient higher than 0.996 0. The limit of detection (LOD) was 0.5 μg/kg and the limit of quantification (LOQ) was 1 μg/kg. The recoveries were 72.8%-102.3% for spiked solid matrix samples, and 71.8%–100.8% for spiked liquid matrix samples with relative standard deviations (RSDs) in the range of 0.25%–3.88% and 0.19%–2.51%, respectively. The proposed method is simple, efficient, rapid, sensitive, and suitable for the qualitative and quantitative analysis of quaternary ammonium disinfectant residues in food for special medical purposes.

In this study, the applicability of hydride generation atomic fluorescence spectrometry (HG-AFS) and inductively coupled plasma mass spectrometry (ICP-MS), methods I and III specified in the national standard GB 5009.93—2017, respectively to detect selenium in infant formula for special medical purposes was researched. Seven laboratories separately determined the selenium content in six samples of 3 types of infant formula for special medical purposes and infant formula quality control samples, and measured the recoveries. The results showed both methods were suitable for the determination of selenium in infant formula, while the applicability for various types of infant formula foods for special medical purposes needs to be further studied.

In this paper, Cr (Ⅲ) and Cr (Ⅵ) in milk were determined by high performance liquid chromatography coupled with inductively coupled plasma mass spectrometry (HPLC-ICP-MS). A PRP-X100 cation exchange column was used. The influence of mobile phase concentration, pH value and flow rate on the degree of separation and retention time was investigated. The mobile phase selected was NH4NO3solution (0.10 mol/L, pH 7) at a flow rate of 1.0 mL/min. Under the optimized conditions, the mass spectrometric and ion interferences were eliminated by using the natural abundance ratio of 52Cr to 53Cr as reference value, and the retention time of Cr (Ⅲ) and Cr (Ⅵ) were determined to be 2.227 and 1.856 min, respectively. Good linearity was observed for Cr (Ⅲ) and Cr (Ⅵ) with correlation coefficients of 0.999 5 and 0.999 7, respectively. The detection limits were 0.015 and 0.016 μg/L, respectively. The overall recoveries for the two valence states were in range of 71.52% to 90.27%. This method proved to be useful for simultaneous analysis of different Cr valence states in milk and dairy products.

Inductively coupled plasma mass spectrometry (ICP-MS) and inductively coupled plasma atomic emission spectrometry (ICP-AES) were compared for determining the contents of metal elements in infant formula milk powder. The limits of detection (LOD) and quantitation (LOQ) of ICP-MS were established using Sc, Rh and Bi as internal standards. Relative standard deviations (RSDs) for 26 analytes were less than 5.0%, and recoveries from spiked samples were 82.80%-110.80%. Eight metal elements could be simultaneously determined by ICP-AES, whose LOD and LOQ were slightly higher than those of ICP-MS. Furthermore, ICP-AES exhibited a good linearity and spiked recoveries in the range of 91.64%-112.73%. In the end, we concluded that both ICP-MS and ICP-AES had a high precision and a good linearity, but ICP-MS allowed the determination of a wider range of metal elements with lower LOD and LOQ.