The aim of the study was to develop a method for quantification of cow’s whey and whole milk powder in goat or sheep milk products including infant formula. A ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) method was established for simultaneous quantification of four caseins and two major whey proteins by detecting their signature peptides, which were able to act as markers for differentiating goat or sheep from cow whey and whole milk powder in infant formulas. The signature peptides were screened based on the computational prediction by Biolynx software, and confirmed by database searching after analysis of liquid chromatography-quadrupole-time-of-flight tandem mass spectrometry (LC-Q-TOF-MS). The isotopic-labeled signature peptide was used as internal standard to compensate the matrix effect. The limits of quantification were 0.01–0.05 g/100 g for target proteins. The observed recovery rates ranged from 82.3 to 116.6 % and the reproducibility was excellent (RSD <12 %) at different spiking levels. The RSDs of intra- and inter-day precision were 2.8–6.2 and 3.3–9.8 %, respectively. The multiple reaction monitoring method was successfully applied to milk powder with different composition, showing high specificity and accuracy in detection of species involved. The calculating formula was designed to assess the composition of adulteration in the actual detection of infant formulas. These results highlight applicability of this method for the detection of infant formulas with complicated matrix.

•An new UPLC–MS/MS method for quantification of human milk α-Lac & β-CN was developed.•The winged IS could release isotope-labeled signature peptide after tryptic digestion.•The winged IS can sufficiently track the enzymatic digestion.•The method provided a new reference strategy for analysis of other human milk proteins.In recent years, there is an increasing need to measure the concentration of individual proteins in human milk, instead of total human milk proteins. Due to lack of human milk protein standards, there are only few quantification methods established. The objective of the present work was to develop a simple and rapid quantification method for simultaneous determination of α-lactalbumin and β-casein in human milk using signature peptides according to a modified quantitative proteomics strategy. The internal standards containing the signature peptide sequences were synthesized with isotope-labeled amino acids. The purity of synthesized peptides as standards was determined by amino acid analysis method and area normalization method. The contents of α-lactalbumin and β-casein in human milk were measured according to the equimolar relationship between the two proteins and their corresponding signature peptides. The method validation results showed a satisfied linearity (R2 > 0.99) and recoveries (97.2–102.5% for α-lactalbumin and 99.5–100.3% for β-casein). The limit of quantification for α-lactalbumin and β-casein was 8.0 mg/100 g and 1.2 mg/100 g, respectively. CVs for α-lactalbumin and β-casein in human milk were 5.2% and 3.0%. The contents of α-lactalbumin and β-casein in 147 human milk samples were successfully determined by the established method and their contents were 205.5–578.2 mg/100 g and 116.4–467.4 mg/100 g at different lactation stages. The developed method allows simultaneously determination of α-lactalbumin and β-casein in human milk. The quantitative strategy based on signature peptide should be applicable to other endogenous proteins in breast milk and other body fluids.

An ultrasound-assisted magnetic solid-phase extraction procedure with the [C7MIM][PF6] ionic liquid-coated Fe3O4-grafted graphene nanocomposite as the magnetic adsorbent has been developed for the determination of five nitrobenzene compounds (NBs) in environmental water samples, in combination with high performance liquid chromatography-photodiode array detector (HPLC-PDA). Several significant factors that affect the extraction efficiency, such as the types of magnetic nanoparticle and ionic liquid, the volume of ionic liquid and the amount of magnetic nanoparticles, extraction time, ionic strength, and solution pH, were investigated. With the assistance of ultrasound, adsorbing nitrobenzene compounds by ionic liquid and self-aggregating ionic liquid onto the surface of the Fe3O4-grafted graphene proceeded synchronously, which made the extraction achieved the maximum within 20 min using only 144 μL [C7MIM][PF6] and 3 mg Fe3O4-grafted graphene. Under the optimized conditions, satisfactory linearities were obtained for all NBs with correlation coefficients larger than 0.9990. The mean recoveries at two spiked levels ranged from 80.35 to 102.77%. Attributed to the convenient magnetic separation, the Fe3O4-grafted graphene could be recycled many times. The proposed method was demonstrated to be feasible, simple, solvent-saving and easy to operate for the trace analysis of NBs in environmental water samples.

DBU-promoted cyclization of ortho-(3-hydroxy-1-alkynyl)benzamide is presented, providing an efficientmethod for the synthesis of trans-3,4-dihydroisoquinolin-1(2H)-ones and (E)-4-(1-alkenyl)isoquinolin-1(2H)-ones under mild conditions.

A mild, simple process for the effective deoximation of a wide range of ketoximes and aldoximes has been developed, which utilizes available NaNO2 as the catalyst and molecular oxygen as the green oxidant. Notably Amberlyst-15, which acts as the initiator of NaNO2, can be reused without regeneration. This environmentally benign protocol could provide a valuable synthetic method for practical applications.