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In recent years, goat milk powder and camel milk powder have gained popularity among consumers. Due to their potential low allergenicity, these milk powders have become a substitute for breast milk, especially for infants, and for people with lactose intolerance. In this paper, a method was developed for the simultaneous determination of 18 amino acids (AAs), histidine (His), serine (Ser), arginine (Arg), glycine (Gly), aspartic acid (Asp) combined with asparagine (Asn), glutamic (Glu), glutamine (Gln), threonine (Thr), alanine (Ala), proline (Pro), lysine (Lys), tyrosine (Tyr), methionine (Met), valine (Val), isoleucine (Iso), leucine (Leu), and dimer of cysteine (Cys) combined with cysteine (L-Cys-Cys), phenylalanine (Phe), taurine (Tau) in milk, goat milk, and camel milk power. The aim of the research was to compare the three kinds of milk powder from the perspective of the constituent amino acids. Therefore, the amino acid compositions and contents were compared. Thus, 2.0 g of the sample was accurately weighed, added to 16 mL H2O, and mixed thoroughly. Then, 200 mg of the sample was weighed in a glass tube with a stream of nitrogen to displace oxygen. The samples were hydrolyzed in HCl for 24 h at 110 ℃. Then, the amino acids were pre-column derivatized by 6-aminoquinoline-n-hydroxysuccinimide carbamate (AQC). In precolumn derivatization combined with reverse-phase chromatography, both 2,4-dinitrofluorobenzene (DNFB) and phenylisothiocyanate (PITC) can react with primary amines and secondary amines. However, the derivatization time is approximately 1 h. In contrast, the derivatization time of AQC was greatly shortened. Derivatization led to the conversion of free amino acids into highly stable derivatives, which were separated by ultra performance liquid chromatography (UPLC) with UV detection at 260 nm and quantified by the external standard method. The samples were separated on a BEH C18 column (150 mm×2.1 mm, 1.7 μm) at a flow rate of 0.4 mL/min. The calibration curves showed good linearity, with correlation coefficients greater than 0.999. The limits of detection (LODs) and limits of quantification (LOQs) of the 18 amino acids were 1.3-2.5 (mg/100 g) and 3.9-7.5 (mg/100 g), respectively. Quality control samples of SRM 1849a were used as the reference material. The results were in accordance with the content range. The RSDs ranged from 2.04% to 3.65%. Furthermore, the developed method was successfully applied to determine the types and concentrations of amino acids in 11 samples purchased from local markets in Shanghai and online shops. Abundant amino acids were detected in the three types of milk powder. While all the milk powder samples contained 18 types of amino acids, Tau was not detected in some of the goat and camel milk powder samples. Total essential amino acids (TEAA) in total amino acids (TAA) of milk powder was the highest of all. The TEAA values of TAA in the goat and camel milk powders were similar. The developed method requires only 22 min for the separation of 18 amino acids. This method is suitable for the large-scale analysis of milk powder samples, and it demonstrates high sensitivity and accuracy for the determination and confirmation of the 18 amino acids in different types of milk powders.

An ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method was established for the quantitative detection of bovine lactoferrin in dairy products. The samples were treated by degreasing and tryptic hydrolysis. Proteins of bovine lactoferrin and peptides were identified using ultra performance liquid chromatography-quadrupole/electrostatic orbitrap-high resolution mass spectrometry (UPLC-Q/Exactive-HRMS) and analyzed by Protein Pilot software. Eight species-specific marker peptides of bovine lactoferrin were identified by comparison of the basic local alignment search tool (BLAST) with the Uniprot database. Three markers with high response strength and stability were chosen for further quantitative research by UPLC-triple quadrupole mass spectrometry (QqQ-MS). The method showed a good linear relationship within its own range. The limits of detection and limits of quantification were 0.023-0.041 and 0.077-0.137 mg/kg, respectively. The observed recoveries were in the range of 93.8%-103.9%. The intra-day and inter-day RSDs were lower than 8.8% and 9.5%, respectively. This method presents various advantages such as strong anti-interference, high sensitivity and reproducibility, and it is suitable for the quantitative analysis of bovine lactoferrin in dairy products.

A method was developed for the simultaneous determination of 16 mycotoxins in drug and food homologous products by ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) combined with accelerated solvent extraction (ASE) and QuEChERS. The target mycotoxins in drug and food homologous products were extracted by ASE. After concentration, the extracts were purified by QuEChERS. Then, the target compounds were analyzed by UPLC-MS/MS in both positive and negative electrospray ionization and MRM modes. Aflatoxin B1 and fumonisin B1 were quantified by the internal standard method, and the remaining mycotoxins were quantified by the matrix-matched external standard method. The proposed method showed a good linear relationship, with correlation coefficients greater than 0.99. The limits of detection (LODs) and limits of quantification (LOQs) of the 16 mycotoxins ranged from 0.008 μg/kg to 0.3 μg/kg and from 0.03 μg/kg to 1.0 μg/kg, respectively. The blank samples were spiked at three levels, and the recoveries ranged from 70.8% to 118%, with the RSDs being 2.5% to 10.2%. The developed method was successfully applied to mycotoxin analysis in 30 scutellaria, puerarin and sea buckthorn samples bought from local markets. Different levels of mycotoxins were detected in some of the products. The proposed method is simple, rapid and sensitive, and it can be applied to the simultaneous determination of multi-mycotoxins in drug and food homologous products.

A liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was established for the determination of 50 non-food additives in health food. The samples were extracted with methanol and purified using the QuEChERS method. The separation was performed on an Agilent Phoroshell SB C18 column (150 mm×3.0 mm, 2.7 μm) with a mobile phase of 0.1% (v/v) formic acid aqueous solution and acetonitrile. The determination was performed by MS/MS in positive or negative electrospray ionization and multiple reaction monitoring mode. The results demonstrated that all 50 compounds could be well separated with a good linear relationship (r2>0.99). The limits of detection (LODs, S/N ≥ 3) and limits of quantification (LOQs, S/N ≥ 10) were in the range of 0.010-1 mg/kg and 0.020-2 mg/kg, respectively. The matrix effects in five kinds of typical health foods (oral liquid, tablets, ointments, pills, and capsules) were evaluated and reduced by means of matrix matching. At the spiked levels of 1 LOQ, 2 LOQ, and 10 LOQ, the recoveries of all drugs varied from 63.1% to 115.7% with relative standard deviations (RSDs) of no more than 8.9% (n=6). The method is simple, sensitive, practical, and suitable for monitoring 50 non-edible additives in health food.

A method was developed for the simultaneous determination of six strobilurin fungicide (E-metominostrobin, azoxystrobin, kresoxim-methyl, picoxystrobin, pyraclostrobin and trifloxystrobin) residues in orange, banana, apple and pineapple samples by ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The fragmentation routes of all the compounds were explained by the aid of a fragment predicting software ACD Lab/MS Fragmenter. The samples were extracted by acetonitrile, then cleaned up by amino solid phase extraction cartridges (SupelClean LC-NH2). The extracts were separated on a ACQUITY UPLC BEH C18 column (50 mm×2.1 mm, 1.7 μm) with gradient elution. Acetonitrile containing 0.1% (v/v) formic acid and 10 mmol/L ammonium acetate containing 0.1% (v/v) formic acid were used as mobile phases. The samples were detected by electrospray ionization (ESI)-MS/MS in positive ion and multiple reaction monitoring (MRM) mode, quantified by external standard method. Good linearities were obtained in the range of 5-100 μg/L (for pyraclostrobin, 1-20 μg/L) with correlation coefficients (r2) greater than 0.999. The recoveries ranged from 60.4% to 120% with the relative standard deviations between 2.15% and 15.1% (n=6). The developed method can meet the inspection of the six strobilurin residues in the orange, banana, apple and pineapple samples.

A gas chromatography-tandem mass spectrometry (GC-MS/MS) method with subcritical water extraction was developed for the determination of 21 organochlorine and pyrethroid pesticides in black tea. Under the extraction pressure of 5 MPa, the target compounds were extracted with subcritical water at the temperature of 150 degrees C for 15 min, transferred into acetone-n-hexane (1:1, v/v), and cleaned-up by an ENVI-Carb solid phase extraction (SPE) column. The GC separation was performed on a DB-5 capillary column. The pesticides were determined by MS/MS in multiple reaction monitoring (MRM) mode and quantified by matrix-matched internal standard method. The calibration curves showed good linearities in the range of 5.0-320.0 microg/L with the correlation coefficients greater than 0.99. The limit of quantification (S/N10) was 50 ng/g, and the limit of detection (S/N3) was 10 ng/g. The recoveries of pesticides spiked in the tea at three levels of 50, 100 and 200 ng/g were ranged from 70. 18% to 119.98% with the relative standard deviations (RSDs) of 5.01%-11.76%. The sensitivity, accuracy and precision of the method meet the technical standard of the pesticide determination. The method can be applied to the determination of organochlorine and pyrethroid pesticides in black tea.

A method based on solid phase extraction-liquid chromatography-tandem mass spectrometry (LC-MS/MS) for the simultaneous determination of melamine and cyanuric acid in foodstuffs is presented. The melamine and cyanuric acid residues were extracted by acetonitrile and water, degreased by hexane, and the extract was cleaned-up by a mixed-mode solid phase-extraction column (MCT) of hydrophilic functional silica gel sorbent and cation exchange resin. The LC separation was performed on a hydrophilic interaction chromatograph, the melamine and cyanuric acid were determined by MS/MS in positive-negative switched electrospray ionization mode, multiple reaction monitoring (MRM) mode, and quantified by isotope internal standard method. The melamine and cyanuric acid were linear in the range of 10-2 500 microg/L with the correlation coefficients (r) higher than 0.99, and the limits of quantification were 25 microg/kg and 50 microg/kg, respectively. The recoveries of melamine and cyanuric acid spiked in animal-derived foods, plant-derived foods, milk and milk products were in the range of 70.0%-129.6% and 70.0%-128.6%, respectively, with the relative standard deviations (RSD) of 1.4%-23.3% and 2.8%-18.7%, respectively. The method can meet the requirement for the determination of melamine and cyanuric acid in foodstuffs simultaneously.

A liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed for the determination of commonly abused dyes in candy, sirup, liquid milk and fruit juice. The test sample was dissolved and diluted with water, then cleaned up by polyamide solid phase extraction. The LC separation was performed on an Agilent XDB-C18 column with 20 mmol/L ammonium acetate solution and acetonitrile as the mobile phase in a gradient elution mode. The dyes were determined by MS/MS in negative electrospray ionization mode, and quantified by matrix-matched external standard method. The calibration curves showed good linearity in the range of 0.5 - 50 mg/L with the correlation coefficients (r) greater than 0.99. The limits of quantitation (S/N10) were 0.5 mg/kg, and the limits of detection (S/N3) were 0.1 mg/kg. The recoveries of dyes in food samples at the three spiked levels of 0.5, 5 and 50 mg/kg were in the range of 62.6% - 115.3% with the relative standard deviations (RSDs) of 2.6% - 26.3%. The method can meet the requirements for the determination of the dyes in food samples for import and export inspection.

A method of liquid chromatography-tandem mass spectrometry (LC-MS/MS) was established for the determination of pyriproxyfen residue in vegetables and fruits. The pyriproxyfen residue in the sample was extracted by acidified acetonitrile with the presence of sodium acetate buffer, and cleaned up by PSA (primary secondary amine) sorbent, and the separation was performed by ultrafast liquid chromatography (UFLC) on a CAPCELL PAK C18 column (50 mm x 2.0 mm, 3 microm) and the gradient elution of acetonitrile (containing 0.1% formic acid) and 2 mmol/L ammonium acetate solution (containing 0.1% formic acid) at a flow rate of 0.3 mL/min. The calibration curve was linear between the peak area and the con centration of 2.5 - 50 microg/L with the correlation coefficient more than 0.9999. The limit of quantification of pyriproxyfen was 5 microg/kg. The average recoveries spiked at three concentrations of 5, 50 and 100 microg/kg ranged 84.7% -91.5%. The relative standard deviations (n = 10) were all less than 10%. The method is selective without interference and suitable for the determination of pyriproxyfen residue in vegetables and fruits.

Endosulfan is one of the organochliorine pesticides and contains two stereoisomers, alpha-endosulfan and beta-endosulfan. Endosulfan sulfate is the oxide of endosulfan with toxicity comparable to endosulfan. The method was developed for the analysis of alpha-endosulfan, beta-endosulfan and endosulfan sulfate in fishery foods. Since the maximal residue level is set at about 4 - 6 microg/kg in many countries, the acceptable method must be sensitive and accurate. The conditions were systematically optimized and external standard method was used for the quantification. The sample was extracted by acetone and hexane (1 : 1, v/v), removed fat by transfering to acetonitrile and cold, and cleaned up with an Envi-Carb column and an LC-Alumina-N column, and analyzed by gas chromatography-mass spectrometry negative ion chemical ionization with selective ion mode. The selective ions of endosulfans and endosulfan sulfate were m/z 406, 408, 404, 372 and m/z 386, 388, 384, 422, respectively. The lowest quantitative limited level of every compound was 0. 5 microg/kg, and the recoveries were 83% - 105%, and the relative standard deviations were less than 13%. The method is efficient, accurate and sensitive to meet the requirements for determining endosulfans in fishery foods.

A method for the determination of glyphosate (PMG) and aminomethylphosphonic acid (AMPA) residues in plant products, such as rice, wheat, vegetables, fruits and tea, pig and chicken muscles, aquatic products, chestnut, honey, etc., was developed using high performance liquid chromatography coupled to tandem mass spectrometry (HPLC-MS/MS). In this method, PMG and AMPA were extracted with water from samples, defatted using an extraction step with dichloromethane, and purified using a cation-exchange (CAX) solid phase extraction cartridge. Then, these were derived using fluorenylmethylchloroformate (FMOC-Cl) in borate buffer for subsequent HPLC-MS/MS analysis. Isotope-labeled PMG 1, 2(13)- C(15) N was used as the internal standard for the quantitative analysis of two residues. For all samples, the recoveries ranged from 80.0% to 104% and the relative standard deviations (RSDs) ranged from 6.7% to 18.2%. The limit of quantification (LOQ) was determined to be 0.05 mg/kg with a linear range of 0.20-10 microg/L. It is demonstrated that this method is reliable and sensitive for the analysis of PMG and APMA with low concentrations in foods.

Isopropylthioxanthone (ITX) has been widely used as the photoinitiator in printing ink of packaging materials in modern food packaging industry. A method regarding the identification and qualification of ITX residue in milk migrated from food contact packaging materials was developed. The procedure was based on the gas chromatography-mass spectrometry (GC-MS) for screening and gas chromatography-tandem mass spectrometry (GC-MS/MS) for confirmation after a solid phase extraction (SPE) step using Florisil column with anthracene D10 (AD10) as the internal standard. Data was acquired in selective ion monitoring (SIM) mode with the following ions: m/z 184, m/z 224, m/z 239, m/z 254 for ITX and m/z 80, m/z 94, m/z 188, m/z 160 for AD10 in screening method of GC-MS. The m/z 254 was selected as the parent ion and m/z 239 as the daughter ion in the conformation method of GC-MS/MS. Data acquired employed the transition of m/z 254, m/z 239 for ITX and m/z 188, m/z 160 for AD10. The method gave limits of quantification (LOQ) of 7.0 microg/L (GC-MS) and 5.0 microg/L (GC-MS/MS) respectively as well as recoveries ranged from 74.9% to 89.6%. The analysis of real samples found two positives out of 11 different milk stuffs available using this method.