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Objectives:To establish a candidate reference measurement procedure based on isotope dilution liquid chromatography-tandem mass spectrometry (ID-LC-MS/MS) for cyclosporin A, tacrolimus, sirolimus, and everolimus measurements in human whole blood.Methods:The isotope labeled cyclosporine A, tacrolimus, sirolimus, and everolimus were selected as the internal standards. Samples were accurately weighed while protein precipitation and solid phase extraction were selected for the sample preparation. The standard curve method was applied for quantification. The ultra-high liquid chromatography coupled with triple quadrupole mass spectrometer was used for analysis. The specificity, matrix effect, detection limit, quantification limit, precision, accuracy, and uncertainty of the method were evaluated.Results:The method showed good selectivity and specificity. No apparent interferences or matrix effects were found in the target analyte measurements. The detection limits and quantification limits of cyclosporin A, tacrolimus, sirolimus and everolimus met clinical requirements. Intra-batch coefficients of variation ( CV) were from 1.4% to 1.8% for CSA, from 1.7% to 2.8% for TAC, from 1.3% to 3.7% for SRL and from 2.3% to 3.2% for EVR, and total CVs were from 1.8% to 2.9% for CSA, from 1.7% to 3.8% for TAC, from 2.6% to 4.7% for SRL and from 3.5% to 4.6% for EVR. The relative recoveries were from 97.9% to 100.3% for CSA, from 98.4% to 103.1% for TAC, from 99.4% to 102.0% for SRL and from 98.3% to 99.4% for EVR, and the relative expanded uncertainties at four concentrations were from 4.2% to 4.4% for CSA, from 1.5% to 2.4% for TAC, from 4.4% to 4.9% for SRL and from 2.2% to 2.7% for EVR. Conclusion:A candidate reference measurement procedure for the cyclosporine A, tacrolimus, sirolimus, and everolimus in human whole blood was established by ID-LC-MS/MS.
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Objective:To establish the allowable total error (TEa) of the national external quality assessment (EQA) program in line with the current quality level of serum folate measurement in China.Methods:The data of serum total folate test in the clinical laboratory of a hospital in Beijing in 2016 were collected, and the Stata SE 15 software was used for Monte Carlo simulation to obtain the false-negative rate under different bias and inaccuracy conditions. The Origin Pro 9.1 software was used to make the contour figure. The TEa of serum total folate test is derived based on the acceptable false-negative rate. National EQA data of serum total folate in 2020 were collected to calculate the pass rate of participating laboratories and the laboratory pass rate of quality control products at each level under the five TEa derived from the analysis performance on clinical outcomes, biological variation, and the evaluation criterion of national EQA.Results:Based on the influence of analytical performance on clinical outcomes, the TEa was 10%. Under this TEa, the pass rate of the first EQA program of serum total folate in 2020 was more than 80%, and the pass rate of the second time was 73.1%. Under the minimum (46.57%) and appropriate level of TEa (15.52%) derived from biological variation and national EQA evaluation criterion, the pass rate of serum total folate in the two EQA programs in 2020 exceeded 85%.Conclusion:The analytical performance of serum total folate in China cannot meet the requirements of TEa derived based on the effect of analytical performance on clinical outcomes. An appropriate level of TEa derived based on biological variation (15.52%) is suggested as the recommended criterion for the TEa of serum total folate test.
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Accurate determination of drug concentration in blood samples is a necessary prerequisite for therapeutic drug monitoring (TDM) and the implementation of precise drug treatment, and it is also one of the important tasks of clinical laboratories.TDM plays an important role in clinical treatment in immunosuppressants (cyclosporine A, tacrolimus), psychotropic drugs (valproic acid, carbamazepine) and other drugs that require monitoring of drug concentration. There are many types of methods used for TDM for the detection of drug concentration in blood samples. At present, only a few immuno-assay methods were approved for marketing with detection systems and kits, most methods used for TDM are high performance liquid chromatography or liquid chromatography-tandem mass spectrometry which belong to laboratory developed tests (LDTs). Detection of TDM samples has many problems, such as incomparable testing results and large bias between different testing systems, including the biasbetween both different methods and different laboratories using the same method. There are several reasons:(1) the traceability chain has not been established, (2) the methods have not yet been standardized, (3) the coverage of the EQA plan is insufficient, (4) the awareness of TDM laboratories to participate in the EQA plan is insufficient, (5) TDM standardization is still in its infancy. These problems restrict the clinical application of TDM and the development of related research work. In order to solve these problems, it is necessary to: (1) Establish a reference system to realize the traceability of the test results; (2) While gradually increasing the TDM EQA plan items, the Trueness evaluation plan should be carried out as soon as possible; (3) Standardized TDM sample testing Technology; (4) Strengthen laboratory management and establish a complete quality management system.
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Background@#Using commutable external quality assessment (EQA) materials is important for monitoring successful harmonization efforts. We assessed the commutability of four human serum pool (HSP) preparations to identify candidate EQA materials for alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activity measurement. @*Methods@#One set each of 85 clinical samples (CSs) was collected for ALT and AST activity measurement. The 15 candidate EQA materials included four types of HSP preparations (A to D): materials A, C, and D contained human original recombinant (HOR) aminotransferases; materials B was mixed leftover samples. The CSs and 15 candidate EQA materials were analyzed using seven routine assays, and the ln-transformed results were analyzed in 21 assay pairs. Commutability was assessed using Deming regression, with a 95% prediction interval (CLSI approach) and the difference in bias with an error component model (International Federation of Clinical Chemistry and Laboratory Medicine [IFCC] approach). @*Results@#For ALT, all materials were commutable for 14–21 assay pairs according to the CLSI and IFCC approaches. For AST, B01-03 showed commutability for 14-21 assay pairs, and C01-03 and D01-03 showed commutability for no less than 10 assay pairs according to the two approaches. A01-06 were commutable for 9-16 assay pairs according to the CLSI approach, but for 6-9 assay pairs according to the IFCC approach. @*Conclusions@#Mixed leftover samples showed desirable commutability characteristics as candidate EQA materials for routine aminotransferase activity measurements. Human serum bases supplemented with HOR were commutable for most routine ALT activity measurements.
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Objective@#The research was to investigate the intermediary effect of school adjustment between famale college students’ life meaning and mobile phone addiction and to provide reference for mobile phone addiction prevention.@*Methods@#Totally 1 355 female college students in Jinan City were investigated with Life Meaning Scale, School Adjustment Scale and Mobile Phone Addiction Scale.@*Results@#Score of freshmen’ mobile phone addiction (34.02±7.87) was significantly lower than that of sophomores’ and junior’(36.67±8.03, 37.19±10.40)(F=4.58, P<0.05). Female college students’ life meaning and school adjustment were negatively correlated with mobile phone addiction(r=-0.50, -0.58, P<0.01). Female college students’ life meaning was positively correlated with school adjustment(r=0.51, P<0.01). Having a sense of life meaning and seeking a sense of life meaning could jointly explain 24% of the variation in mobile phone addiction. School adjustment played a complete mediating role between life meaning and mobile phone addiction in female college students.@*Conclusion@#Female college students’ life meaning can affect mobile phone addiction through school adjustment.
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Objective@#The aim of this study is to evaluate the commutability of 16 processed materials for 17-hydroxyprogesterone by using 2 commutability assessment approaches.@*Methods@#52 serum specimens were collected in Clinical Laboratory Department of Beijing Hospital from February 2018 to June 2019. According to the report of the Clinical and Laboratory Standards Institute (EP14-A3) document and the recommendations of the International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) working group on commutabilityassessment, serum 17-hydroxyprogesterone isotope diluent chromatogram tandem mass spectrometry (ID-LC/MS/MS) was used for comparison. Three clinical routine analysis systems (1 radioimmunoassay, 2 LC/MS analysis methods) were used to determine the concentration of 17-hydroxyprogesterone in 52 human serum samples and 16 processed materialsfor commutabilityassessment.@*Results@#Combined with the results of the two commutability assessment, all accuracy verification materials and national steroid hormone standards showed good commutability in the LC/MS analysis system, and 6/9 EQA materials showed commutability in the three routine analysis systems.All materials showed good commutability in the LC/MS analysis system of bias difference method.@*Conclusions@#The two kinds of commutability assessment results are different. Bias difference method has more clinical value, but it has certain application limitations. The use of fresh frozen human serum as a quality assessment materialfor serum 17-hydroxyprogesterone is meets the commutability requirement.
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Objective:To establish an accurate quantitative method for the determination of serum glycated albumin (GA) based on isotope dilution liquid chromatography tandem mass spectrometry (ID-LC/MS/MS).Methods:This study optimized the ID-LC/MS method recommended by the Japan Society of Clinical Chemistry (JSCC). Albumin (Alb) was purified by anion exchange chromatography. The standard solution of purified sample, lysine (Lys) and deoxyfructosyl lysine (DOF-Lys) and their mixed internal standard were weighed accurately by weight method. The Alb was hydrolyzed to amino acid, and Lys and DOF-Lys were detected to determine GA. The method was evaluated and compared with the routine method.Results:The purity of Alb was 100%. The R 2 ranges of Lys and DOF-Lys linear standard curves were 0.997 8-0.999 9 and 0.999 4-1.000 0. The results of three-day precision evaluation of low, medium and high concentrations of serum were 0.69%-1.97%, 1.13%-2.33% and 1.37%-2.54% in intra, inter and total Coefficient of variation ( CV). In the accuracy evaluation, the deviations between the results of three concentration standards and the certified value were -2.56%, -1.87% and-2.94%. The matrix effects of Lys and DOF-Lys were 89.92% and 109.98%, and the carryover rates were -1.13% and -3.27% respectively. The detection limit and quantitative limit of Lys were 0.075 nmol/g and 0.248 nmol/g, and the DOF-Lys were 0.007 nmol/g and 0.024 nmol/g. The relative expanded uncertainty was 1.60%-2.03%. The fitting regression curve R 2 with the routine method was 0.970 7. Conclusions:A method was established for the detection of serum GA. The method evaluation was accurate and reliable. It was expected to be a candidate reference method for the detection of serum GA.
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Objective:To establish a candidate reference method for simultaneous determination of whole blood iron and copper based on ICP-MS technology.Methods:Cobalt (Co) was chosen as the internal standard, and was added gravimetrically into the standard solution and the whole blood sample. The whole blood sample was digested by electric heating plate and diluted. The isotopic ratios of 57Fe/ 59Co and 63Cu/ 59Co were measured by ICP-MS in the isotopic analysis mode. The precision, standard recovery and accuracy of the method were verified by measuring EQA materials and certified standard materials, and the performance of the method was further evaluated by method comparison. Results:The detection limit of iron is 0.136 mg/kg and the limit of quantification was 0.454 mg/kg in this method. The detection limit of copper in whole blood was 0.008 mg/kg and the limit of quantification was 0.027 mg/kg. The standard curve of copper ranges from 0.83-3.33 mg/kg, iron ranges from 167-667 mg/kg. The calibration curve of iron and copper was good linearity ( R 2>0.999 90). The precision of the method did well. The total CV range was 0.42%-0.68% for iron and 0.14%-0.94% for copper. The spike recoveries were all around 100%, the range of iron: 99.69%-100.07%; copper: 99.26%-100.51%. The correlation between this method and the existing clinical mass spectrometry methods was good. Conclusions:A candidate reference ICP-MS method for simultaneous determination of whole blood Fe and Cu was established. This is a simple and rapid method with good precision and spike recovery compared to the traditional one.
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Objective:The aim of this study is to evaluate the commutability of 16 processed materials for 17-hydroxyprogesterone by using 2 commutability assessment approaches.Methods:52 serum specimens were collected in Clinical Laboratory Department of Beijing Hospital from February 2018 to June 2019. According to the report of the Clinical and Laboratory Standards Institute (EP14-A3) document and the recommendations of the International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) working group on commutabilityassessment, serum 17-hydroxyprogesterone isotope diluent chromatogram tandem mass spectrometry (ID-LC/MS/MS) was used for comparison. Three clinical routine analysis systems (1 radioimmunoassay, 2 LC/MS analysis methods) were used to determine the concentration of 17-hydroxyprogesterone in 52 human serum samples and 16 processed materialsfor commutabilityassessment.Results:Combined with the results of the two commutability assessment, all accuracy verification materials and national steroid hormone standards showed good commutability in the LC/MS analysis system, and 6/9 EQA materials showed commutability in the three routine analysis systems.All materials showed good commutability in the LC/MS analysis system of bias difference method.Conclusions:The two kinds of commutability assessment results are different. Bias difference method has more clinical value, but it has certain application limitations. The use of fresh frozen human serum as a quality assessment materialfor serum 17-hydroxyprogesterone is meets the commutability requirement.
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Chronic kidney disease caused by diabetes and hypertension has become a global public health problem. Urinary albumin is one of the key indicators for the diagnosis and grading of chronic kidney disease, and it has been widely used in practice. Accurate and comparable results of urinary albumin detection served as an important basis for clinical application. This paper discussed the status of urinary albumin detection and the progress of standardization, in order to help the laboratory correctly interpret the test results and promote the quality of diagnostic products.
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Objective Accurate measurement of aldosterone is critical in the diagnosis of primary aldosteronism. We compared the harmonization of three assays including isotope dilution liquid chromatography-tandem mass spectrometry (ID-LC-MS/MS) and two chemiluminescence immunoassays (CLIAs:system A and system B) for the aldosterone measurement. Methods A total of 45 plasma samples, 4 quality control materials, 5 lyophilized bovine serums, and 3 fresh frozen human serum pools were measured by three assays respectively. Based on CLSI EP15-A3 rule, the precision was assessed by coefficient of variance. Deming regression and Bland&Altman plots was performed for method comparison, and correlation coefficient was calculated for concordance (CCC). Results All three methods met the performance criteria based on desirable biological variation for precision (<7.35％). System A showed a relevantly good correlation and comparability with ID-LC/MS/MS (R2=0.985, CCC=0.967), while System B showed relevantly bad correlations and comparability with both System A (R2=0.538, CCC=0.605) and ID-LC/MS/MS (R2=0.547, CCC=0.528).. However, the average relevant bias of two CLIAs exceeded the bias requirement derived from biological variation (18.60％). Conclusion Significant differences were found in the measurement of plasma aldosterone using ID-LC-MS/MS and two CLIAs, which urges the establishment of traceability hierarchy and improvement of reagents' specificity for standardization of aldosterone measurement in clinical settings.
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Objective To evaluate the comparability and consistency of two kinds of triglycerides reference methods, one of which is the isotope dilution liquid chromatography-mass spectrometry (LC/MS) in the Cholesterol Reference Method Laboratory Network (CRMLN), the other isthehigh-performance liquid chromatography (HPLC) method for triglyceride detection in China. Methods 52 fresh frozen sera with triglycerides levels among 0.45-4.52 mmol/L were determined by LC/MS and HPLC. After evaluation the precision and accuracy of the two methods,a series of analyses were conducted including plotting to scatter plots and deviation graphs, testing outliers, selecting the best fitting regression models and calculating the regression equations and parameters, and so on. The expected deviation at the level of medical decision of triglycerides and the 95％confidence range were statistically analyzed.Results For HPLC method, the CV of instrument measurement was 0.29％(0％-1.16％), the total CV of samples measurement was 0.54％(0.04％-1.28％), and the average bias of the reference materials was 0.22％(-0.43％-0.68％). ForLC/MSmethod,the CV of instrument measurement was 0.55％(0％-1.68％),the total CV of samples measurement was 0.79％(0％-1.93％), and the average bias of the NIST reference materials was 0.09％(-0.73％-1.29％). No outlier was found from the scatter plots and the statistical analysis and the linear regression was fitted to analyze the results of the two methods. The linear regression parameters of two methods for 52 fresh frozen human sera were as follows:the slope was 0.9988,the standard error of slope was 0.0035, the intercept was 0.0037mmol/L, the standard error of intercept was 0.0030 mmol/L, the standard error of Y-estimate was 0.0236 mmol/L,and the correlation coefficient was 0.9997. Compared with the LC/MS method,the absolute deviation of fresh sera by HPLC method was-0.001 mmol/L (-0.070-0.056 mmol/L), with a relative deviation of 0.13％ (-2.01-2.83％). T-test showed no statistically significant difference between the two methods. The expected deviations at the triglycerides medicine decision level were within the 95％confidence range,and the expected deviations were far less than the allowable error. Conclusions The HPLC method of triglyceridesdetetion has good consistency and comparability with LC/MS method as one of the reference methods of CRMLN. Because of the advantages of HPLC method such as low cost, simplicity,less technical need,and better precision,HPLC method is expected to play an important role in the process of standardization and traceability of serum triglycerides.
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Objective To perform a methodological evaluation study of 4 HPLC based systems and a capillary electrophoresis based system , with the International Federation of Clinical Chemistry and Laboratory Medicine ( IFCC) glycated hemoglobin reference method as a comparative method .Methods 40 hemolysis samples of variety concentrations were prepared .The samples were measured by IFCC reference method and 5 glycated hemoglobin testing systems , respectively and trueness verification was performed according to the Clinical &Laboratory Standards Institute (CLSI) guideline EP9-A3.Whole blood samples were used to test the systems'precision, linearity and analytical interferences .Results The average CV of IFCC reference method results of 40 hemolysis samples was 1.4％( range from 0.2％to 2.5％).No outlier was found in the results of the 5 testing system.The slopes ranged from 0.9902 to 1.0267, and intercepts from -0.1526 mmol/mol to +0.1512 mmol/mol, squared correlation coefficient from 0.9962-0.9971, biases at two medical decision level were less than 0.3％HbA1c.Within-laboratory precisions were less than 2％ (NGSP unit).Bias between all test results and predicted results were less than 5％.High concentration of glucose showed certain interference to glycated Hemoglobin tests but had little influence in clinical practice.Conclusions The results of the 5 testing system are comparable to the IFCC reference method , the results of precision and linearity evaluation meet the requirements of related guidelines .
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The national external quality assessment (EQA)programs for hemoglobin A1c (HbA1c) measurements in China have been carried out for about 20 years, and the performances of HbA 1c testing in the participating laboratories has been significantly improved .The entire reference system for HbA 1c has been established in China.The first stage in the infrastructure and platform setup for the standardization is substantially completed.In the next step, the focuses of our work will transfer to fully application of the standardization of HbA 1c measurements in China although still many challenges .
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Objective To evaluate the commutability of 22 processed materials for serum alanine aminotransferase measurements which were performed in 11 routine assays without and 2 assays with pyridoxal-5′-phosphate.Methods 100 serum specimens were collected in Beijing Hospital,Zhao Yang Hospital and Tong Ren Hospital from May,2017 to August,2017.50 individual specimens together with fresh frozen human serum pools(HSPs), external quality assessment(EQA)materials, commercial calibrators and controls were measured by 11 routine assays without pyridoxal-5′-phosphate.Measurement results of the 50 individual samples were pairwise analyzed by Deming regression for slopes and intercepts, and 95%prediction interval(PI)were calculated to evaluate the commutability of processed materials.Another 50 individual specimens and 22 above-mentioned materials were analyzed by 2 assays with pyridoxal-5′-phosphate as the evaluated methods and internationally recognized reference method as the comparative method.The ordinary linear regression(OLR)and 95% PI were used to identify the commutability of 22 materials.Results The Deming slopes ranged from 0.879 to 1.064 and intercepts from -1.96 to 3.30;the OLR slopes were 0.905 and 0.955 while intercepts were -6.71 and 9.53.The HSPs were commutable for 51/57 and 56/57 assay pairs.The EQA materials, commercial calibrators and controls showed noncommutability from 8/57 to 47/57,38/57 and pairs after that, and from 13/57 to 43/57 assay pairs, respectively.Conclusion The lyophilized materials including EQA materials, commercial calibrators and controls demonstrated poor commutability in different degrees.
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Objective To understand the current status of the measurement quality of serum Cystatin C (CysC) in China.Methods The external quality assessment (EQA) data in 2017 were collected from the network platform of National Center for Clinical Laboratories.The EQA data were classified into 8 groups according to different types of diagnostic reagents,each of which was employed by at least 18 users.The robust mean value and robust coefficients of variation (CV) were calculated according to ISO 13528 document in each group.The robust mean value was set as the target value.The total error derived from biological variation was used as the fine (3.8％),moderate (7.6％) and weak (11.4％) criteria in evaluating the pass rates,respectively.The reagents which were employed by more than 50 users were classified into subgroups named as " reagent-analyzer" group according to the used analyzer.The median values and differentials between maximum and minimum value were calculated for each reagent-analyzer subgroup.Results A total number of 710 laboratories submitted their results of CysC measurement during 2017.The fine,moderate and weak pass rates according to the setting criteria were 25.9％ (184/710),55.5 ％ (394/710) and 75.2％ (534/710),respectively.The variations of CysC measurement results of among different reagent-analyzer groups ranged from 1.62％ to 12.27％.Conclusion The quality of CysC measurement of should be improved with nationwide attention.
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Objective To evaluate the consistency and comparability of two kinds of cholesterol reference methods listed in the Joint Committee for Traceability in Laboratory Medicine(JCTLM).Methods 52 fresh frozen sera with cholesterol concentrations among 3 -10 mmol/L were tested by isotope dilution liquid chromatography tandem mass spectrometry (ID-LC/MS/MS)and high performance liquid chromatography(HPLC).The precision and accuracy of the two methods were calculated,and then a series of analysis were conducted including plotting scatter plots and deviation graphs,testing outliers,selecting the best fitting regression models and calculating the regression equations and parameters,and so on.The results of the two methods were statistically analyzed to estimate the expected deviation at the level of medical decision of cholesterol and the 95% confidence range.Results For HPLC method,the CV of instrument measurement was 0.22%(0 -0.49%),the total CV of samples measurement was 0.36%(0.02% -0.83%),and the average bias of the reference materials was 0.37%(-1.31%-0.14%).For ID-LC/MS/MS method,the CV of instrument measurement was 0.50%(0 -1.51%),the total CV of samples measurement was 0.55%(0.03%-1.17%),and the average bias of the reference materials was 0.24%(-0.53%-0.14%).No outliers were found from the scatter plots and the statistical analysis and the linear regression were fitted to analyze the results of the two methods.The linear regression parameters of two methods for 52 fresh frozen human sera were as follows:the slope was 0.989 5,the standard error of slope was 0.003 4,the intercept was 0.063 4 mmol/L,the standard error of intercept was 0.019 9 mmol/L,the standard error of Y-estimate was 0.034 8 mmol/L,and the correlation coefficient was 0.999 7.Compared with the ID-LC/MS/MS method,the absolute deviation of fresh sera by HPLC method was 0.000 mmol/L (-0.083-0.076 mmol/L),with a relative deviation of 0.07%(-1.22-1.24%).T-test results showed no statistically significant difference between the two methods.The expected deviations at the cholesterol medicine decision level were within the range 95% confidence range,and the expected deviations were far less than the allowable error.Conclusions The HPLC method of cholesterol has good consistency and comparability with ID/MS method using the primary measurement principle.Because of more advantages of HPLC method such as less cost,more simple,requirement,and better precision,HPLC method is expected to play an important role in the process of standardization and traceability of serum cholesterol.
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Objective Preparation of aqueous reference materials for cholesterol and glycerol.Methods Study on reference materials.The certified reference materials GBW09203b and GBW09149 were weighed accurately and dissolved into 20% of methyl cyclodextrin aqueous solution to prepare six kinds of candidate reference materials of cholesterol and glycerol according to the concentration.The materials were tested for homogeneity and stability using routine methods.The reference methods of isotope dilution liquid chromatography tandem mass spectrometry (ID-LC/MS/MS) were used to determine the concentration of cholesterol and glycerol to evaluate the accuracy of the certified values.Meanwhile, the blank verification test was carried out.The expanded uncertainty was the combination of standard uncertainty of measurement, unhomogeneity and instability.Results It showed that the six candidate reference materials were homogeneous and stable for at least 1 year at-70 ℃ and-20 ℃.The certified values (reference value ± expanded uncertainty,mmol/L) were as follows,for cholesterol:0.65±0.01,1.31 ±0.01,2.57±0.02,5.21±0.06,7.71±0.08,10.24±0.06;for glycerol:0.29±0.01,0.58±0.01,1.22±0.02,2.24±0.02,3.46±0.04,4.52 ±0.04.The results of reference methods were consistent with the certified values.Blank validation tests showed that the concentration of the analytes would not be affected by the reagent and the blank matrix.Conclusions Certified reference materials for cholesterol and glycerol in aqueous solution have been prepared successfully.These materials are homogeneous and stable, and the certified values are reliable.Therefore the materials have been approved to be the Certificate Reference Materials of GBW 09823, GBW 09824, GBW 09825, GBW09826, GBW09827 and GBW 09828.
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Objective To develop a gel permeation chromatography method for determination of content and molecular weight ( Mw ) of Mussel Polysaccharide.Methods Using GPC method, the sample was separated with TSK-gel GMPWXL(7.8 mm ×300 mm) chromatography column which was set at 35℃.The mobile phase was 0.05 mol/mL NaNO3(including 0.05%Na2N3) and the flow rate was 0.6 mL/min.The detector was RID-20AT. Results The average molecular weight of the polysaccharide of Mytilus coruscus was 1 261 411 and the average content was 88.6%by using of the calibration curves of dextrans.The average molecular weight of the polysaccharide of Mytilus edulis was 1 244 062 and the average content was 87.4%. Conclusion The method established in this paper is simple and rapid, accurate and reproducible, which can be used for the quality control of Mussel Polysaccharide.
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Objective To prepare the serum reference materials for total thyroxine .Methods Individual blood samples were collected from 13 healthy donors (7 males and 6 females) aged from 20 to 50 years old, and the sera were separated and mixed into 4 serum pools according to the concentration of thyroxine.The materials were tested for homogeneity and stability using routine methods .The method of isotope dilution liquid chromatography tandem mass spectrometry ( ID-LC/MS/MS) was used to determine the concentration of thyroxine .The candidate reference materials were also measured by four conventional methods to analyze the commutability of the materials .Results It showed that the four candidate reference materials were homogeneous and commutable in four conventional methods and they were tested to be stable for at least 1 year at -70 ℃using the isochronous stability study .The certified values ( reference value ± expanded uncertainty ,nmol/L) were:75.9 ±1.8,105.3 ±2.2,114.7 ±2.1 and 187.4 ±2.9.Conclusions Certified reference materials for serum thyroxine have been prepared .These materials have been approved to be the Certificate Reference Materials of GBW 09127,GBW 09128,GBW 09129 and GBW 09130.