乙酸乙酯标准物质的制备

为解决卷烟包装纸残留挥发性有机化合物分析中缺少乙酸乙酯标准物质问题,利用高纯乙酸乙酯试剂为原料,严格控制配制和封装过程,研制出乙酸乙酯溶液标准物质,并对其进行了均匀性检验和稳定性考察。7家实验室对该标准物质进行了合作定值,结果为1.02 mg/mL,扩展不确定度为0.03 mg/mL,符合国家二级标准物质技术要求。     

芹菜中7种农药及其代谢物基体标准物质的制备

目的 制备芹菜中7种农药及其代谢物基体标准物质。方法 将空白芹菜样品粉碎、冷冻干燥制成干粉后,与农药标准溶液混匀,搅拌挥发干后制得基体标准物质,经均匀性和稳定性检测,由8家实验室联合定值,并进行不确定度评估。结果 基体标准物质中7种农药及其代谢物的特性值为0.497～0.502 mg/kg,扩展不确定度为0.0079～0.0123 mg/kg,均匀性良好,可稳定保存至少12周。结论 通过该方法制备的基体标准物质均匀性和稳定性良好,定值结果可靠,可用于检测过程的质量控制、检测方法开发、实验室能力验证等领域。     

一种含毒死蜱的黄瓜冻干粉基质标准物质的研制

目的建立了一种以黄瓜为基质的毒死蜱标准物质的制作方法。方法黄瓜样品经研磨、加标、冷冻干燥、磨粉、混匀、真空包装后,用GB 23200.113-2018检验样品的均匀性、稳定性,并联合多家实验室对黄瓜冻干粉中毒死蜱基质样品定值,同时分析样品的不确定度。结果F-检验法和t-检验法表明在95%置信区间内,样品均匀性、短期稳定性和长期稳定性均达到标准物质要求。采用格拉布斯和柯克伦检验对定值结果进行异常值检验,并对结果进行不确定度评估,样品定值为1.78 mg/kg,不确定度为0.12 mg/kg。结论该样品具有良好的均匀性、稳定性,可作为蔬菜中毒死蜱含量检测使用的标准物质。     

三乙酸甘油酯中丙酮溶液标准物质

以高纯度丙酮和三乙酸甘油酯试剂为原料,通过严格控制配制和封装过程,研制了丙酮溶液标准物质,并对该标准物质进行了均匀性检验和稳定性考察。结果表明:7家实验室对该标准物质的合作定值结果为0.95 mg/mL;在95%的置信概率下,取包含因子k=2,则扩展不确定度为0.03 mg/mL。该标准物质符合国家二级标准物质的技术要求,满足卷烟用纸中挥发性有机化合物残留量的测定。     

乳粉中三聚氰胺标准物质的制备

目的制备乳粉中的三聚氰胺标准物质。方法将三聚氰胺标准溶液与乳粉复溶液通过均质、冷冻干燥、粉碎、过筛、混合等步骤制得标准物质,经均匀性与稳定性研究,由8家实验室进行协同定值,并进行不确定度评估。结果制得的标准物质的特性值为(5.19±0.37) mg/kg,均匀性良好,稳定性大于12个月。结论通过该方法制得的标准物质,均匀性与稳定性良好。可用于检测方法的开发、检测过程的质量控制、实验室能力验证、实验室间比对等领域。     

冻干羊奶中伊维菌素基体标准物质的研制

为了研制冻干羊奶中伊维菌素基体标准物质,向泌乳羊皮下注射伊维菌素,目标羊奶经混合、分装、预冻干、冻干等步骤,制得一批冻干羊奶中伊维菌素自然基体标准物质。所得样品经均匀性和稳定性检验后,由8家实验室协同定值,并评估其不确定度。结果表明,该标准物质均匀性和稳定性良好,其特性值和不确定度(以羊奶计)为(15.3±1.0)μg/kg,k=2。使用该方法制备的标准物质符合标准规定,满足生鲜羊乳中伊维菌素检测过程中质量控制和方法验证的需求。     

鱼肉粉中二噁英及二噁英类多氯联苯成分分析标准物质的研制

目的 研制鱼肉粉基体中二噁英及二噁英类多氯联苯成分分析标准物质。方法 以草鱼为原料,采用污染物含量较高的飞灰样品配合饲料喂养,经去骨去皮,匀浆干燥、研磨筛分等过程后制得候选标准物质,经均匀性和稳定性评价,由8家实验室定值,分析评估其不确定度。结果 经检验基体标准物质均匀性良好,能长期稳定保存至少12个月,PCDD/Fs的特性值为0.017～1.4 pg/g,扩展不确定度为0.02～0.6 pg/g;DL-PCBs的特性值为0.54～16 pg/g,扩展不确定度为0.28～6 pg/g。此标准物质已通过标准物质评审,编号为GBW(E)100741。结论 该标准物质均匀性及稳定性良好,定值准确,可用于食品、环境等领域二噁英及二噁英类多氯联苯的量值溯源、分析检测、质量控制、实验室能力验证、分析仪器校准、分析方法的准确性评估和验证等。     

香蕉汁中苯甲酸、柠檬黄和日落黄标准物质的研制

目的 建立香蕉汁中苯甲酸、柠檬黄和日落黄标准物质的研制与定制方法。方法 采用单因素方差分析均匀性, 线性回归趋势分析稳定性, 多家实验室合作定制, 并计算其不确定度。结果 标准值及扩展不确定度(k=2): 苯甲酸(209.96±7.52) mg/kg; 柠檬黄(302.18±4.98) mg/kg; 日落黄(41.52±0.66) mg/kg。结论 研制的标准物质均匀性和稳定性较好, 可用于食品安全监测及相关饮料的质量控制。     

奶粉中维生素B2标准物质的研制

筛选一款奶粉,均匀化后分装。进行均匀性检验、稳定性考察、定值分析和不确定评价,对标准物质进行了高效液相色谱法定值分析和不确定度评价。标准物质定值结果为15.7±2.4 mg/kg。建立的标准物质,对于奶粉中维生素B2分析的质量控制、方法验证和实验室分析能力考核具有重要意义。     

水中总有机碳溶液标准物质的研制

目的研制一种适用于相关检测仪器校准及分析方法评价的国家有证标准物质。方法经过标准物质原材料的选择、特性量值的测量方法、标准物质的制备方法、均匀性检验、12个月稳定性考察以及定值测量,并对样品的均匀性、测量的分散性及其他因素引入的不确定度分量分析和确定后,计算得到水中总有机碳标准物质测量过程不确定度的合成结果。结果水中总有机碳溶液标准物质的均匀性良好,稳定性优异,标准值定值结果为1000mg/L,相对扩展不确定度为2%。该标准物质已获批国家二级标准物质,编号为:GBW(E)082426。结论该标准物质性能良好,可满足食品、药品、日化、环境保护及化工产品研究和检测的需要,可用于相关仪器(总有机碳分析仪)的校准、分析方法评价,为统一相关量值发挥应有的作用。     

Accurate determination of lead in Chinese herbs using isotope dilution inductively coupled plasma mass spectrometry (ID-ICP-MS)

A method for the determination of Pb in Chinese herbs based on “approximate matching” isotope dilution inductively coupled plasma mass spectrometry was developed. The method was validated using NIST SRM 1547 (Peach Leaves). Satisfactory analytical figures of merit were achieved, including good sample recovery (∼99%) and low relative expanded uncertainty (less than ±2%). The validated method was applied to the analysis of a herbal sample for the international comparison CCQM-P97. Measurement uncertainty was evaluated according to three approaches, namely Kragten’s spreadsheet approach, GUM Workbench and Monte Carlo method (MCM). A practical way was established for the evaluation of measurement uncertainty based on the propagation of distributions using MCM. The validated method was also employed for the provision of SI-traceable mass fraction of Pb in an in-house herbal reference material and the assignment of a reference value to a proficiency testing programme.     

Ochratoxin A case study: Establish metrological traceability of mycotoxin measurements using certified reference materials

For the US Food and Drug Administration's (FDA) mycotoxin program, the desired application of certified reference materials (CRMs) is primarily for validating methods for the determination of mycotoxins in foods and establishing metrological traceability of measurement results generated by such validated methods. The latter has been an important but insufficiently addressed challenge due to the lack of appropriate protocols and CRMs. Taking advantage of two recently available mycotoxin CRMs, OTAN-1 and Standard Reference Material (SRM) 1565, a protocol was developed for systematically examining uncertainty and establishing metrological traceability of measurement results of ochratoxin A (OTA) in corn through a series of calibration operations using the two CRMs. Instrument and method calibrations were performed using OTAN-1 and SRM 1565. The OTA value and its standard and expanded (k = 2, approximately 95% confidence) uncertainties were estimated from the calibration data and documented. These results demonstrate that the major contributing source of uncertainty is the sample matrix, highlighting the important role of the certified matrix reference material in method calibration. The value of OTA (38.5 ± 7.2 µg/g; 95% confidence interval) in the incurred sample was metrologically traceable to the International System of Units through two CRMs using the multi-laboratory validated liquid chromatography–mass spectrometry FDA compendial method. In addition, an alternative estimation of uncertainty was conducted using a one-point calibration, resulting in comparable uncertainty.     

角鲨烯国家标准样品的研制

为研制角鲨烯国家标准样品。以角鲨烯粗品为原料,制备高纯角鲨烯,采用红外光谱、高分辨质谱和核磁共振谱进行结构确证。样品分装成150 瓶后,采用气相色谱-氢火焰离子化检测器法进行均匀性、稳定性检验和定值分析。从样品中随机抽取15 瓶进行均匀性检验,经F检验表明在95%置信区间范围内样品均匀性良好;稳定性考察按照－18 ℃长期实验稳定性（24 个月）进行,结果表明在考察期间内样品稳定性良好;标准样品经国内8 家具有分析资质的实验室进行协同定值,并评定了定值结果的不确定度,角鲨烯标准样品定值结果为99.57%,相对扩展不确定度为0.30%（k=1.96）。该标准样品达到国家标准样品的技术要求,可用于有关角鲨烯的方法校正和质量控制。     

双氰胺纯度标准物质的研制

目的建立双氰胺的纯度定值方法来研制双氰胺纯度标准物质(certified reference material,CRM),并考察其均匀性、稳定性和不确定度。方法采用基于高效液相色谱(high performance liquid chromatography,HPLC)的质量平衡法和差示扫描量热法(differential scanning calorimetry,DSC)2种方法对双氰胺的纯度进行定值。水分、无机杂质和挥发性溶剂分别采用卡尔费休滴定法(Karl Fischer,KF)、电感耦合等离子体质谱法(inductively coupled plasma mass spectrometry,ICP-MS)和顶空气相色谱-质谱法(headspace gas chromatography mass spectrometry,HSGC-MS)测量。根据《标准物质定值的通用原则及统计学原理》(JJF 1343-2012)的要求,采用高效液相色谱法进行均匀性和稳定性的检验。不确定度评定综合考虑均匀性、稳定性、定值过程引入的不确定度。结果均匀性和稳定性检测结果表明:均匀性良好,在规定的保存条件下可以稳定保存36个月以上。研制的双氰胺标准物质的纯度为99.8%,扩展不确定度0.3%(k=2)。结论本研究研制双氰胺标准物质的量值具有溯源性和准确性。     

Single laboratory method performance evaluation for the analysis of total food folate by trienzyme extraction and microplate assay

ABSTRACT:  Single laboratory method performance parameters, including the calibration curve, accuracy, recovery, precision, limit of detection (LOD), and limit of quantification (LOQ), were evaluated for the analysis of total food folate by the trienzyme extraction and microplate assay with Lactobacillus casei subsp. rhamnosus . Standard Reference Material (SRM) 1546 (meat homogenate), SRM 2383 (baby food composite), SRM 1846 (infant formula), Certified Reference Material (CRM) 121 (wholemeal flour), and CRM 485 (mixed vegetables), representing a broad selection of food matrices, were used to evaluate the performance of the method. A generated 4-parameter logistic equation of the calibration curve was y = (0.0705 − 1.0396)/(1 + ( x /0.0165) ^1.3072) + 1.0396 ( P < 0.0001). The test of parallelism demonstrated that matrix components in the food extracts did not affect the accuracy. Measured values of the SRMs and CRMs were within their certified or reference values. Recoveries for all reference materials met the requirements of the AOAC guidelines for single laboratory validation. Precision measured as repeatability, including simultaneous and consecutive replicates for each SRM and CRM, met the Horwitz criterion. LOD and LOQ values were 0.3 and 0.6 μg/100 g, respectively. The results showed that trienzyme digestion using α-amylase, Pronase^R, and conjugase from chicken pancreas coupled with a 96-well microplate assay provided a highly accurate, reproducible, and sensitive method for the determination of folate in a variety of foods.     

Carbon speciation of diesel exhaust and urban particulate matter NIST standard reference materials with C(1s) NEXAFS spectroscopy

The U.S. National Institute of Standards and Technology (NIST) provides a number of particulate matter (PM) standard reference materials (SRM) for use in environmental and toxicological methodology and research. We present here the first analysis with respect to the molecular structure of the carbon in three such NIST SRM samples, i.e., diesel engine exhaust soot from heavy duty equipment engines (SRM 1650), diesel soot from a forklift engine (SRM 2975), and urban PM collected in St. Louis, MO (SRM 1648), with near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. The NEXAFS spectra of the two diesel soot samples appear quite similar, while they differ significantly from the urban PM spectrum, in agreement with X-ray diffraction data published recently. Such comparison is made in terms of aromatic and aliphatic carbon species, as well as by a general comparison with graphitic materials. Both diesel soot SRM samples contain basic graphitic structures, but the presence of exciton resonance and extended X-ray absorption fine structure oscillations in SRM 1650 and the lack therof in SRM 2975 suggest that SRM 1650 is the more graphitic material.The presence of polycyclic aromatic hydrocarbons, which have a characteristic NEXAFS resonance at the same position as graphite, can obscure the graphitic character of soot, unless an extraction of the organic matter is made. Our NEXAFS data do not suggest that the urban PM sample SRM 1648 contains a substantial amount of graphite-like material.     

基于最小二乘法的靛蓝上染率计算

利用烧碱、保险粉、N-甲基吡咯烷酮制备NMP溶剂溶解靛蓝。以100%纯靛蓝颗粒作为基准物,通过分光光度计法,在最大吸收波长下测试低质量浓度靛蓝溶液的吸光度。用最小二乘法处理测试数据并制作校验曲线,最终确定靛蓝溶解液的质量浓度因子。此方法先溶解经纱靛蓝,再测试溶解液的吸光度,经验证可计算出不同深度经纱靛蓝的上染率。     

Rapid multi-element analysis of Chinese vinegar by sector field inductively coupled plasma mass spectrometry

An analytical method for simultaneous determination of 20 trace elements in vinegar including Na, Mg, K, Ca, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Sr, Mo, Cd, Sn, Sb, Ba and Pb by sector field inductively coupled plasma mass spectrometry (SF-ICP-MS) with microwave digestion has been established. Sample first underwent microwave digestion with HNO₃ + H₂O₂ followed by dilution with ultrapure water, and then, the as-obtained solution was analyzed directly by SF-ICP-MS. The matrix effects were studied in details and corrected by Sc, In and Re as the internal standard elements. Data accuracy was improved by measuring in medium-resolution mode and high-resolution mode. The applicability of the proposed method has also been validated by the analysis of reference material (NIST SRM 1643e). These results showed that the detection limit of this method is in the range of 0.002–0.34 μg/L with good precision (RSD < 3 %).     

Analysis of "total toxaphene" and selected single congeners in biota by ion trap HRGC-EI-MS/MS using congener-optimized parent ion dissociations

A method for the quantification of selected toxaphene congeners as well as "total toxaphene" was developed based on electron ionization (EI) tandem (MS/MS) ion trap mass spectrometry (MS) and a combination of fragment ion dissociations. Congeners were separated by high-resolution gas chromatography. Compared to conventional EI low-resolution MS, a 5-20-fold gain in sensitivity could be obtained for octa- or nonachlorinated compounds such as toxaphene #26 and #62 (according to Parlar nomenclature), allowing for their detection in the low picogram range in biota. In addition, response factors for important congeners such as #26, #32, #40/41, #42, #44, #50, and #62 deviated not more than a factor of 2, which is much less as compared to negative ion chemical ionization. This reduces the risk for systematic errors when determining total toxaphene on the basis of a limited number of reference compounds or the technical mixture. Furthermore, chlordanes and polychlorinated biphenyls did not interfere when applying the proposed MS/MS technique. The applicability of the method was tested by determining both total toxaphene and levels of selected congeners in six Arctic wildlife samples collected from Nunavut, Canada, as well as by repetitive analyses of the SRM 1588 certified reference material.     

Naturally-occurring folates in foods: Method development and analysis using liquid chromatography–tandem mass spectrometry (LC–MS/MS)

An accurate method for detecting and quantifying both synthetic (folic acid) and naturally-occurring folates in foods is described. A system capable of analysing the five most commonly occurring folates (pteroylglutamic acid, 5-methyltetrahydrofolate, tetrahydrofolate, 10-formylfolate and 5-formyltetrahydrofolate) in 20 min using liquid chromatography–tandem mass spectrometry (LC–MS/MS) was developed. Quantification of folates was performed using ¹³C labelled internal standards. This paper outlines the development of a comparatively fast LC–MS/MS method, method validation using commercially available folate standards and establishment of the method’s suitability for quantification using selected reaction monitoring (SRM) mass spectrometry. The application of the system was verified by analysing several certified reference materials and comparing results with certified values as determined by microbiological assay. LC–MS/MS promises to be an ideal tool for the quantitative analysis of folates in food.