An Improved POD Model for Fast Semi-Quantitative Analysis of Carbendazim in Fruit by Surface Enhanced Raman Spectroscopy.

The current detection method of carbendazim suffers from the disadvantages of complicated preprocessing and long cycle time. In order to solve the problem of rapid quantitative screening of finite contaminants, this article proposed a qualitative method based on characteristic peaks and a semi-quantitative method based on threshold to detect carbendazim in apple, and finally the method is evaluated by a validation system based on binary output. The results showed that the detection limit for carbendazim was 0.5 mg/kg, and the detection probability was 100% when the concentration was no less than 1 mg/kg. The semi-quantitative analysis method had a false positive rate of 0% and 5% at 0.5 mg/kg and 2.5 mg/kg, respectively. The results of method evaluation showed that when the added concentration was greater than 2.5 mg/kg, the qualitative detection method was consistent with the reference method. When the concentration was no less than 5 mg/kg, the semi-quantitative method is consistent between different labs. The semi-quantitative method proposed in this study can achieve the screening of finite contaminants in blind samples and simplify the test validation process through the detection probability model, which can meet the needs of rapid on-site detection and has a good application prospect.

Synthesis of deuterium-labeled 2-quinoxalinecarboxylic acid and 3-methylquinoxaline-2-carboxylic acid from deuterium aniline.

An efficient and simple synthetic route of deuterium-labeled 2-quinoxalinecarboxylic acid-d4 (QCA-d4 ) and 3-methylquinoxaline-2-carboxylic acid-d4 (MQCA-d4 ) is presented with 99.9% and 99.6% isotopic enrichment using aniline-d5 as labeled starting material. Their chemical structures were confirmed by 1 H NMR, and their isotopic abundance was determined by mass spectrometry analysis.

A Novel Zebrafish (Danio rerio) Assay for Assessing Musk Ambrette-Induced Toxicity.

Musk ambrette (4-tert-butyl-3-methoxy-2,6-dinitrotoluene) is a nitro musk, a cheap substitute for natural musk and a potential environmental pollutant based on its persistence, accumulation in human organisms. We investigated the acute toxicity of musk ambrette using wild-type AB and transgenic Tg(fli1a:EGFP)y1 zebrafish. Different concentrations were delivered to zebrafish by direct soaking from 6 to 72 h post-fertilization (hpf). The LC50 of musk ambrette was 76.4 µg mL-1. As musk ambrette concentration increased, zebrafish embryos showed developmental delays (50 µg mL-1, 22 hpf), pericardial edema (5 µg mL-1, 48 hpf), circulatory disturbances, curved body axis (1 µg mL-1, 72 hpf) and death (100 µg mL-1, 22 hpf). Target organ toxicity was evaluated by a zebrafish angiogenesis model. Musk ambrette induced cardiovascular morphological changes, vessel permeability variation, angiogenic changes and cardiotoxicity (10 µg mL-1, 48 hpf). The disappearance of caudal vein plexus confirmed the vascular development toxicity. Musk ambrette negatively affects early life-stage survival and demonstrates various toxicities in zebrafish.

Determination of a metabolite of nifursol in foodstuffs of animal origin by liquid-liquid extraction and liquid chromatography with tandem mass spectrometry.

An analytical method has been developed for the detection of a metabolite of nifursol, 3,5-dinitrosalicylic acid hydrazide, in foodstuffs of animal origin (chicken liver, pork liver, lobster, shrimp, eel, sausage, and honey). The method combines liquid chromatography and tandem mass spectrometry with liquid-liquid extraction. Samples were hydrolyzed with hydrochloric acid and derivatized with 2-nitrobenzaldehyde at 37°C for 16 h. The solutions of derivatives were adjusted to pH 7.0-7.5, and the metabolite was extracted with ethyl acetate. 3,5-Dinitrosalicylic acid hydrazide determination was performed in the negative electrospray ionization method. Both isotope-labeled internal standard and matrix-matched calibration solutions were used to correct the matrix effects. Limits of quantification were 0.5 µg/kg for all samples. The average recoveries, measured at three concentration levels (0.5, 2.0, and 10 µg/kg) were in the range of 75.8-108.4% with relative standard deviations below 9.8%. The developed method exhibits a high sensitivity and selectivity for the routine determination and confirmation of the presence of a metabolite of nifursol in foodstuffs of animal origin.

Rapid Detection of Nonprotein Nitrogen Adulterants in Milk Powder Using Point-Scan Raman Hyperspectral Imaging Technology.

To develop a rapid detection method for nonprotein nitrogen adulterants, this experiment sets up a set of point-scan Raman hyperspectral imaging systems to qualitatively distinguish and quantitatively and positionally analyze samples spiked with a single nonprotein nitrogen adulterant and samples spiked with a mixture of nine nonprotein nitrogen adulterants at different concentrations (5 × 10-3 to 2.000%, w/w). The results showed that for samples spiked with single nonprotein nitrogen adulterants, the number of pixels corresponding to the adulterant in the region of interest increased linearly with an increase in the analyte concentration, the average coefficient of determination (R 2) was above 0.99, the minimum detection concentration of nonprotein nitrogen adulterants reached 0.010%, and the relative standard deviation (RSD) of the predicted concentration was less than 6%. For the sample spiked with a mixture of nine nonprotein nitrogen adulterants, the standard curve could be used to accurately predict the additive concentration when the additive concentration was greater than 1.200%. The detection method established in this study has good accuracy, high sensitivity, and strong stability. It provides a method for technical implementation of real-time and rapid detection of adulterants in milk powder at the port site and has good application and promotion prospects.

[Determination of 18 amino acids in three different kinds of milk powder by ultra performance liquid chromatography coupled with pre-column derivatization].

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.

Multivariate analysis for organic milk authentication.

To differentiate organic milk (OM) from conventional milk (CM), an orthogonal projection to latent structure-discriminant analysis (OPLS-DA) model was constructed using δ13C, δ15N, δ18O, 51 elements and 35 fatty acids (FAs) as the variables. So far, most reported studies barely use three or more types of variables, but more variables could avoid one-sidedness and get stabler models. Our multivariate model combines geographical and nutritional parameters and displays better explanatory and predictive abilities (R2X = 0.647, R2Y = 0.962 and Q2 = 0.821) than models based on fewer variables for differentiating OM and CM. In particular, δ15N, Se, δ13C, Eu, K and α-Linolenic acid (ALA) are found to be critical parameters for the discrimination of OM. These results show that the multivariate model based on stable isotopes, elements and FAs can be used to identify OM, and can potentially expand the global databases for quality and authenticity of milk.

Correction: Determining the geographical origin of milk by multivariate analysis based on stable isotope ratios, elements and fatty acids.

Correction for 'Determining the geographical origin of milk by multivariate analysis based on stable isotope ratios, elements and fatty acids' by Siyan Xu et al., Anal. Methods, 2021, DOI: .

Determining the geographical origin of milk by multivariate analysis based on stable isotope ratios, elements and fatty acids.

To construct a reliable discrimination model for determining milk geographical origin, stable isotope ratios including δ13C, δ15N and δ18O, 51 elements and 35 fatty acids (FAs) in milk samples from Australia, New Zealand and Austria were detected and analyzed. It is found that all of the stable isotope ratios in the milk samples of Australia are the highest, followed by those of the samples from New Zealand and Austria. In addition, 14 elements and 8 FAs show different contents in the samples of different countries at the significance level of P < 0.05. Based on these results, a multivariate model with good robustness and predictive ability for authenticating milk origin (R2X = 0.693, Q2 = 0.854) was successfully constructed. Element contents and stable isotope ratios are more reliable variables for milk origin discrimination and Rb, δ18O, Tl, Ba, Mo, Sr, δ15N, Cs, As, Eu, C20:4n6, Sc, C13:0, K, Ca and C16:1n7 are the critical markers in the multivariate model for verifying milk origin.

[Determination of bovine lactoferrin in milk and dairy products by ultra performance liquid chromatography-tandem mass spectrometry].

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.

[Determination of 11 synthetic musks in imported seafood by solid phase extraction and gas chromatography-mass spectrometry].

A method has been developed for the simultaneous determination of 11 synthetic musks (cashmeran, celestolide, phantolide, musk ambrette, traseolide, galaxolide, musk xylene, tonalide, musk moskene, musk tibetene, and musk ketone) in imported seafood. The method combines solid phase extraction and gas chromatography-mass spectrometry. Samples were extracted by n-hexane and purified using a Florisil column. Internal standards were used to correct for matrix effects. The calibration curves showed good linearity with correlation coefficients greater than 0.99. The limits of detection (S/N>3) ranged from 0.35 to 2.08 µg/kg, and the limits of quantification (S/N>10) were between 1.18 and 5.00 µg/kg. The average recoveries measured at three spiked levels (10, 20, and 30 µg/kg) were in the range 83.1%-117%, with relative standard deviations ranging from 5.1% to 8.5%. Further, the concentrations of 11 synthetic musks in 30 imported seafood in Shanghai were investigated. Galaxolide was detected in 93.3% of samples analysed, in concentration as high as 3.82 µg/kg. Musk ambrette and musk moskene were found in concentrations as high as 15.4 µg/kg and 10.5 µg/kg, respectively. The established method demonstrates high sensitivity and selectivity for the determination and confirmation of 11 synthetic musks in imported seafood.

[Identification of meat marker peptides and detection of adulteration by liquid chromatography-tandem mass spectrometry].

A liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) method was established for the identification of meat marker peptides and quantitative detection of common exogenous meat in mutton adulteration. Samples were prepared by protein extraction, trypsin hydrolysis, and solid phase extraction. Proteins and peptides were identified using ultra-performance liquid chromatography-quadrupole/electrostatic orbitrap-high resolution mass spectrometry (UPLC-Q/Exactive-HRMS) combined with Proteinpilot software. Twenty species-specificity marker peptides in mutton, duck, pork, and chicken were identified by comparison of the basic local alignment search tool (BLAST) with the Uniprot database. Verification and multiple reaction monitoring (MRM) of these marker peptides were performed quantitatively using a UPLC-triple-quadrupole mass spectrometry (QqQ-MS) system. Duck, pork, and chicken were added to mutton at mass percentages of 1%, 5%, 10%, 20%, and 50%. The limit of detection for the adulterants was 0.25% for duck, 0.17% for pork, and 0.10% for chicken.