Objective To establish a rapid method for the determination of neutral degreaser concentration by quantitative acid addition and nonlinear fitting, and to solve the problem of titration method and weighing method lack of accuracy and detection efficiency. Methods Prepare the working curve solutions of different concentrations by using the degreaser original solution, and measure the $\mathrm{{pH}}$ value after adding a quantitative amount of acid.The relationship function between the $\mathrm{{pH}}$ value and the concentration of degreaser is obtained by non-linear fitting, and then the concentration in the production sites degreasing solution is calculated by the function.Explore the amount of acid added, curve fitting method, and fitting order, and determine the optimal experimental conditions. Results The method was applied to the rapid determination of neutral degreaser concentration, with a relative standard deviation (RSD) of 0.85% to 1.17% and a recovery rate between 98.52% to 103.34%. Conclusion The new method proposed in this study is accurate, reliable, simple and rapid.And overcomes the shortcomings of traditional titration and gravimetric methods, it can effectively guide the application of neutral degreaser and improve the surface quality of metal materials.

Objective To establish a method for the determination of six phthalates [diisobutyl phthalate (DIBP), di-n-butyl phthalate (DBP), di(2-butoxy)ethyl phthalate (DBEP), dicyclohexyl phthalate (DCHP), di(2-ethyl)hexyl phthalate (DEHP) and diisononyl phthalate (DINP)] in semi-solid food by gas chromatography-mass spectrometry (GC-MS/MS). Methods The optimization of chromatography and mass spectrometry conditions, the comparison of pretreatment extraction methods, and the selection of purification columns were carried out. The samples were extracted with an organic solvent, and the supernatant was purified by a solid phase extraction column made of ethylenediamine-N-propylsilane/silica gel (PSA/Silica) composite packing glass, and separated by a capillary column TG-5MS (${{30}\mathrm{\;m}}\times {0.25}\mathrm{\;{mm}}\times {0.25}\mathrm{\;{\mu m}}$). The optimal conditions were selected by mass spectrometry full scan (SCAN) mode, and then by feature selective ion monitoring scan mode (SIM) detection, the retention time and qualitative ion fragment abundance ratio were qualitatively analyzed, and the external standard method was used for quantitative analysis. Results The separation was completed within 26.5 min. Linear range: DINP had a good linear relationship in the concentration range of${0.2}\sim {5.0}\mathrm{{\mu g}}/\mathrm{{mL}}$, with$\mathrm{r}> {0.9995}$, and the other five species had a good linear relationship in the range of ${0.02}\sim {0.50\mu}\mathrm{g}/\mathrm{{mL}}$, with$>\mathrm{r}{0.9995}$。The limit of quantification was${9.0}\mathrm{{mg}}/\mathrm{{kg}}$, DINP was ${0.3}\mathrm{{mg}}/\mathrm{{kg}}$, and the others were ${0.5}\mathrm{{mg}}/\mathrm{{kg}}$, and the three-level standard solution was added to the two dipping materials and bottom materials, respectively: DINP was 20,40 and ${60}\mathrm{{mg}}/\mathrm{{kg}}$, and the others were 4,6 and 8 $\mathrm{{mg}}/\mathrm{{kg}}$, and the recovery rates were 89.1%~101%. The RSD % was less than 3.8%. Conclusion This method has simple pretreatment, good selectivity, sensitivity and accuracy, and can be widely used for the determination of plasticizers in semisolid composite seasonings.

Objective The color analysis equipment "plasma colorimeter" developed by customization was used to analyze the color of plasma prepared by whole blood composition, summarize the color parameter range of normal, reddish and chyle plasma, and explore the feasibility of formulating quantitative standards for plasma appearance. Methods The collected 2U whole blood was randomly selected, the same amount of normal, reddish and chyle plasma was separated and prepared, the proportion of parameters of red, green and blue in the appearance of plasma was collected by plasma colorimeter, the laws of each parameter were summarized by statistical methods, and the differences between the three plasma parameters were compared. Results Between normal plasma and reddish plasma, the proportion of parameter red was significant different (P>0.05), while those of parameter green and parameter blue were not significant different (P<0.05); Between normal plasma and chyle plasma, the difference of proportion of parameter green was significant (P>0.05), those of parameter red and blue are not significant (P<0.05). Between normal plasma and reddish plasma, the proportions of red, green and blue in reddish plasma and chyle plasma were all significantly different (P<0.05) Conclusions The quantitative values of color in plasma appearance can be obtained by using plasma colorimeter, and these values can provide a basis for digital and accurate judgment of plasma appearance, further to effectively improving the efficiency of blood station work.

With the increasingly serious environmental pollution, food may be affected by various new pollutants, such as microplastics and heavy metals. Therefore, it is necessary to continuously study the detection methods of new pollutants to ensure the overall safety of food. This article makes a deep thinking and innovative discussion on food testing work under the background of food safety.

Objective To study the determination of total phosphorus in carbon compound lithium iron phosphate by direct carbon removal gravimetric method. Methods After the sample was decomposed by perchloric acid and the carbon in the sample was removed at the same time, the yellow quinoline phosphomolybdate was precipitated by the reaction of orthophosphoric acid with the precipitant quinomolymonone in the acidic medium. The phosphorus content could be obtained by filtration, washing, drying and weighing. Results The carbon removal by perchloric acid was complete and clear, and the steps of filter and carbon removal were reduced. The precision and accuracy tests of the method were carried out by optimizing the conditions. The relative standard deviation (RSD) of the method was less than 0.2%, and the recovery rate of standard addition was 98.4% ~ 101.1%. The biggest advantage of this method is that carbon is directly removed in the digestion process, eliminating the influence of carbon encapsulation on phosphorus determination, no need to filter carbon removal, shorten the operation process, short analysis time, high content of phosphorus is determined by classical gravimetric method, which has high precision and accuracy, and can provide rapid and accurate results for production. Conclusion This method is suitable for the rapid and accurate determination of total phosphorus in carbon complex lithium iron phosphate.

Objective To evaluate the uncertainty in determination of olive oil total migration by gas chromatography spectrometry, determine the factors affecting the accuracy of the results and provide a basis for accurate control of the olive oil total migration. Methods Gas chromatography spectrometry was used to determine the olive oil total migration, and a mathematical model was established. According to relevant rules and standards for uncertainty evaluation, the uncertainty was evaluated including repeatability, sample quality and adsorbed olive oil quality, instrument calibration, standard curve fitting, soaking area, etc. Results When The total migration of olive oil in the sample is ${4.0}\mathrm{{mg}}/{\mathrm{{dm}}}^{2}$, the expanded uncertainty was ${1.3}\mathrm{{mg}}/{\mathrm{{dm}}}^{2}\left({P={95}\%, k = 2}\right)$ . Conclusion The uncertainty of olive oil total migration mainly comes from repeatability, standard solution preparation and standard curve fitting.

Objective In the present paper, the influences of matrix effect (ME) to the quantification of imidacloprid, thiamethoxam and clothianidin in ginger and banana were evaluated, and especially, the influencing factors and compensating means of matrix effect in LC-MS/MS analysis were proposed. Methods In this research, the matrix effects of three neonicotinoid insecticides in ginger and banana were evaluated by LC-MS/MS analysis after QuEChERS pretreatment. Both matrix-matched calibration curves and solvent calibration curves were established for the assessment of matrix effect. Results The linear regression coefficients of the matrix-matched calibration curves were all above 0.999 and the precision of the measured sample results was better than that of the solvent standard. The recoveries and relative standard deviations of all compounds at matrix-matched calibration curves were 86.7%~103.0% and 2.1%~8.3%, respectively. Conclusion Matrix effects can compromise the precision and accuracy of the analysis results. These results also indicated that matrix effects were mainly affected by matrix concentration, the types and samples of matrices and the overall chemical structure of the pesticide. The linear regression coefficients and precision as well as accuracy were more satisfactory for all the pesticides when matrix-matched standard was used, which reflected an excellent compensating means of matrix effect. This can improve the accuracy of quantitative results, which is feasible in routine testing, and is of great significance for ensuring the quality and safety of ginger and banana products.

Objective To evaluate the risk of pesticide residues in cucurbit vegetables in Guizhou Qiandongnan Prefecture. Methods LC-MS and GC-MS was used for determination of residues of the level of 50 pesticide residues in cucurbit vegetable samples collected randomly from Guizhou Qiandongnan Prefecture. Results It showed that Pesticide residues were detected in 15 samples of 100 cucurbit vegetables, 8 pesticides were detected, 20 times in total, The average value of food safety index in cucurbit vegetables related to pesticide residues did not exceed the national maximum residue limit in Guizhou Qiandongnan Prefecture. Conclusion Our findings suggest that the potential hazard level of pesticide residues in cucurbit vegetables in Guizhou Qiandongnan Prefecture is acceotable.

Objective This study aims to accurately quantify two key components in Baijiu (Chinese liquor) production and quality control: acetic acid and hexanoic acid. Methods A direct injection-gas chromatography (GC) technique was used for the rapid and precise simultaneous determination of acetic acid and hexanoic acid in Baijiu. Results Using this method, the detection limit for acetic acid reached 0.012 g/L and for hexanoic acid, 0.0050 g/L. All correlation coefficients exceeded 0.999. The relative standard deviations (RSD) were 0.32% for acetic acid and 0.33% for hexanoic acid, with spiked recovery rates of 96.15% for acetic acid and 96.69% for hexanoic acid, respectively. Conclusion The new detection method proposed in this study not only overcomes the limitations of traditional detection methods and gas chromatography in many aspects but also demonstrates high efficiency, sensitivity, and excellent selectivity. This method has significant practical implications for improving the production process of Baijiu, ensuring the consistency of product flavor, and safety.

Objective To evaluate the uncertainty evaluation for the determination of imidacloprid in Caidian lotus root by ultra performance liquid chromatography-tandem quadrupole mass spectrometry. Methods According to GB/T 20769 - 2008 Determination of 450 pesticides and related chemicals residues in fruits and vegetables-Liquid chromatography-tandem mass spectrometry, the content of imidacloprid in Caidian lotus root was determined and the mathematical model was built. According to the provisions of JJF 1135-2005 Evaluation of measurement uncertainty in chemical analysis and JJF 10591-2012 Technical specification for evaluation and representation of measurement uncertainty, the uncertainty was quantified by scientific analysis, and the extended uncertainty of imidacloprid content in Caidian lotus root　was finally calculated. Results When the residue imidacloprid in Caidian　lotus root was ${0.322}\mathrm{{mg}}/\mathrm{{kg}}$ , the　relative standard synthetic uncertainty was 0.08689 and the expanded　uncertainty was ${0.0560}\mathrm{{mg}}/\mathrm{{kg}}$ . The　determination results were　 $\left({{0.322}\pm {0.0560}}\right)\mathrm{{mg}}/\mathrm{{kg}},P ={95}\%, k = 2$ . Conclusion The main sources of uncertainty in　the determination of imidacloprid in Caidian lotus root by ultra　performance liquid chromatography-tandem quadrupole mass spectrometry　are the preparation of standard solution, sample pretreatment and　measurement process of the measuring instrument.