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 To evaluate the precision and accuracy level of four Dimai DM79x blood cell analyzers in the most suitable working state of our department's daily indoor quality control by comparing the indoor quality control data, so as to improve the accuracy and consistency of test results. Methods In February 2023 (28 days), the indoor quality control data of four laboratory instruments using original low, medium and high fixed value quality control products and daily testing of a random outpatient fresh patient sample were collected. The items included: White blood cells (WBC), red blood cells (RBC), hemoglobin (HGB), hematocrit (HCT), platelets (PLT), mean red blood cell volume (MCV), mean red blood cell hemoglobin volume (MCH), mean red blood cell hemoglobin concentration (MCHC) calculated mean (X), standard deviation (S) and coefficient of variation (CV), Coefficient of variation index (CVI) and standard deviation index (SDI) were used as precision and accuracy evaluation indexes respectively. Result The statistical analysis showed that the blood cell analysis of the DM79x instrument included 8 parameters, including WBC, RBC, HGB, PLT, HCT, MCV, MCH and MCHC. The coefficient of variation index of CVI of each instrument was different, and the indoor quality control result of SDI was <2.0. The measured values of CVI and SDI of fresh sample comparison data are all within the required range. Conclusion Four Dimai DM79x automatic blood cell analyzers in our department have good precision and high accuracy by comparing the indoor quality control data between laboratories. The performance of the instrument can meet the work needs of clinical laboratories. Moreover, the accuracy and consistency of the results in different instruments can be ensured by comparing the fresh samples of patients.

Compared with most of the current published instruments and equipment management risk research literature, generally only pay attention to the risk identification of individual links, and there are problems such as incomplete risk identification and analysis, which will affect the effectiveness of instrument and equipment risk management. In order to guide the inspection body and laboratory to carry out the risk management of instruments and equipment more reasonably, risk identification is carried out from the aspects of the whole life cycle and safety of instruments and equipment, and the identified risks are analyzed and evaluated, and risk disposal suggestions are put forward according to the evaluation results. Encourage inspection body and laboratory to always meet the requirements of management system and compliance operation in terms of instrument and equipment risk management.

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.

In this paper, the equipment management, personnel training and quality control of the laboratory are comprehensively assessed by adopting quality control methods such as checklist evaluation and traceability management. Taking a food testing laboratory as an example, it quantitatively analyzes its quality management and gives the evaluation and improvement suggestions on equipment management, personnel training and quality control of the laboratory. Meanwhile, in the process of establishing a traceable management system, the management of quality control should also be strengthened to improve the accuracy and reliability of testing. Through the improvement and refinement of the laboratory, it can not only enhance the overall quality level of the testing laboratory, but also contribute to the maintenance of social public safety and health.

The permanganate index is a titration analysis based on redox reactions used to characterize the degree of organic and inorganic reducing substances in water. The explores the reaction mechanism of the acidic potassium permanganate method and elucidates the possible sources of error in the detection of permanganate index, in order to improve the accuracy of water quality testing. In summary, the accuracy of the permanganate index can be affected by various factors, including titration errors, oxidation reaction errors, and other sources of error. The effective solutions and precautions for experimental operations based on an analysis of these sources of error.

The gas chromatograph uses gas as the mobile phase, and the sample to be measured is brought into the column by the carrier gas after gasification in the gasification chamber, and the components are separated in the column and detected by the detector. The baseline is the comprehensive performance of the performance of the gas chromatograph in operation, and the failure of each part of the instrument, the change of operating conditions and external conditions and other factors will be reflected on the baseline, so the cause and location of the fault can be judged according to the baseline.

Objective To understand the water quality of a remote rural well in a northern city, and to provide rationalized recommendations for the targeted development of a water quality improvement program. Methods The water quality of 32 self-provided wells in the area was sampled during the abundant and dry water periods each year from 2021 to 2023, tested and evaluated in accordance with the Sanitary Standard for Drinking Water (GB/T 5750-2006) and the Hygiene Standards (GB 5749-2006) for testing and evaluation use SPSS 26.0. Results Show that the 192 water samples tested, 144 are qualified, the pass rate is 75.00%. Dry water period pass rate is 84.38%. Abundant water period pass rate is 65.63%. Conclusion The water quality pass rate of a remote rural well in a northern city is lower than the pass rate in the dry season, and the water quality needs to be improved to ensure the safety of drinking water and the health of rural residents.

To avoid major differences in the testing process, help customers correctly understand and use reports, and effectively control risks, according to the relevant requirements of Laboratory Accreditation and Inspection Body and Laboratory Mandatory Approval, combined with practical experience, this paper puts forward 10 aspects that should be agreed in the inspection and testing entrustment agreement, analyzes more than 10 items that should be declared in the inspection and testing report, summarizes the key issues that should be paid attention to, and provides general requirements for the industry to refer to, which has a great practical guiding significance for the standardization of inspection and testing activities.