Tutorial review on validation of liquid chromatography–mass spectrometry methods: Part II

This is the part II of a tutorial review intending to give an overview of the state of the art of method validation in liquid chromatography mass spectrometry (LC–MS) and discuss specific issues that arise with MS (and MS–MS) detection in LC (as opposed to the “conventional” detectors). The Part II starts with briefly introducing the main quantitation methods and then addresses the performance related to quantification: linearity of signal, sensitivity, precision, trueness, accuracy, stability and measurement uncertainty. The last section is devoted to practical considerations in validation. With every performance characteristic its essence and terminology are addressed, the current status of treating it is reviewed and recommendations are given, how to handle it, specifically in the case of LC–MS methods.     

煤及焦炭标准样品国内外发展概况

阐述了煤及焦炭标准样品的发展概况,通过对国内外煤及焦炭标准样品的种类、技术性能指标等方面进行比较,指出了煤及焦炭标准样品的变化动态与发展趋势。     

高效除草剂快杀稗标准物质的制备及表征

从快杀稗工业品出发 ,经活性炭纯化、硅胶柱层析分离制得快杀稗标准物质 ,并进行熔点、高效液相色谱、紫外光谱、元素分析、红外光谱、质谱、核磁共振等方法的表征 ,以高效液相色谱法测得该标准品纯度在99%以上     

硫化锌中硫酸根含量标准物质的研制

介绍了红外光学材料用ZnS粉体标准物质的研制工作。以ZnS粉体为基体材料,通过提纯方法进行ZnS粉体中硫酸根含量标准物质的制备。经过均匀性检验、稳定性考察后,采用离子色谱法进行定值。制备的标准物质硫酸根含量在0.1%~0.5%范围呈3个梯度分布,相对扩展不确定度U不大于2%(k=2)。     

ICP–AES法测定铬镍不锈钢中锰、铬、镍、硅、磷、铜、钼的含量

建立电感耦合等离子体原子发射光谱(ICP–AES)法测定铬镍不锈钢中锰、铬、镍、硅、磷、铜、钼7种元素含量的方法。试样用盐酸与硝酸混合酸溶液溶解,采用溶解国家标准样品的方法制备校准曲线溶液,确定了元素最佳分析谱线。各元素的含量在其测试范围内与原子发射强度呈良好的线性关系,线性相关系数不小于0.999,7种元素的检出限在0.000 3%~0.003 0%之间。该方法应用于铬镍不锈钢标准样品的测定,测定值与认定值相符,测定值的相对标准偏差在0.12%~1.15%之间(n=8)。应用于铬镍不锈钢样品测定时,加标回收率在90%~110%之间。该方法操作简便、迅速,可满足日常铬镍不锈钢中多元素含量的检测需要。     

In situ sulfur isotopes (δS and δS) analyses in sulfides and elemental sulfur using high sensitivity cones combined with the addition of nitrogen by laser ablation MC-ICP-MS

The sulfur isotope is an important geochemical tracer in diverse fields of geosciences. In this study, the effects of three different cone combinations with the addition of N₂ on the performance of in situ S isotope analyses were investigated in detail. The signal intensities of S isotopes were improved by a factor of 2.3 and 3.6 using the X skimmer cone combined with the standard sample cone or the Jet sample cone, respectively, compared with the standard arrangement (H skimmer cone combined with the standard sample cone). This signal enhancement is important for the improvement of the precision and accuracy of in situ S isotope analysis at high spatial resolution. Different cone combinations have a significant effect on the mass bias and mass bias stability for S isotopes. Poor precisions of S isotope ratios were obtained using the Jet and X cones combination at their corresponding optimum makeup gas flow when using Ar plasma only. The addition of 4–8 ml min⁻¹ nitrogen to the central gas flow in laser ablation MC-ICP-MS was found to significantly enlarge the mass bias stability zone at their corresponding optimum makeup gas flow in these three different cone combinations. The polyatomic interferences of OO, SH, OOH were also significantly reduced, and the interference free plateaus of sulfur isotopes became broader and flatter in the nitrogen mode (N₂ = 4 ml min⁻¹). However, the signal intensity of S was not increased by the addition of nitrogen in this study. The laser fluence and ablation mode had significant effects on sulfur isotope fractionation during the analysis of sulfides and elemental sulfur by laser ablation MC-ICP-MS. The matrix effect among different sulfides and elemental sulfur was observed, but could be significantly reduced by line scan ablation in preference to single spot ablation under the optimized fluence. It is recommended that the d₉₀ values of the particles in pressed powder pellets for accurate and precise S isotope analysis should be less than 10 μm. Under the selected optimized analytical conditions, excellent agreements between the determined values and the reference values were achieved for the IAEA-S series standard reference materials and a set of six well-characterized, isotopic homogeneous sulfide standards (PPP-1, MoS₂, MASS-1, P-GBW07267, P-GBW07268, P-GBW07270), validating the capability of the developed method for providing high-quality in situ S isotope data in sulfides and elemental sulfur.     

Evaluation of a proficiency test on cadmium and lead in herbal material using assigned reference values

This paper presents an international proficiency testing program (APLAC T065) on two trace elements, cadmium and lead, in an herbal sample, Herba Desmodii Styracifolii. The program was registered with a total of 109 laboratories from 42 countries. The assigned reference values of the analytes for performance assessment were provided by the organizers using an accurate gravimetric isotope dilution inductively coupled plasma-mass spectrometry technique. z-Score was used as the numerical indicator to interpret participants' competence. The between-laboratory variations for cadmium and lead were respectively 18.7% and 19.8% and the consensus values were found to be consistent with the assigned reference values. Twenty-two participants gave at least one unsatisfactory z-score, but the performance of the majority of participants on the analysis of cadmium and lead in herbal matrix was generally good when compared with the assigned reference values.     

Pressurised liquid extraction and quantification of fat-oil in bread and derivatives products

A pressurised liquid extraction (PLE) method for extraction and quantification of total fat and oil in bread and derivatives products has been proposed. Parameters implied in the extraction process; such us temperature, static time, number of extraction cycles, purge time and flush volume; have been optimised using a formal methodology based on statistical experimental design in order to obtain the best results. Moreover, this method has been validated using homemade bread elaborated in the laboratory which contained 9.64 g of olive oil in 100 g dry weight. The production and use of an “ad hoc” in-house reference material is just one of the most relevant aspects of this study. The uncertainty estimation has been carried out taking into account all the uncertainty components of the process and it was stated as 4.2%. Finally, the proposed method has been applied to six different Spanish bread derivatives products with different olive oil contents (5-20%) to determine the fat content.     

诱惑红溶液标准物质的研制及不确定度评定

建立了食用合成色素诱惑红溶液标准物质的制备和定值方法,研制了100mg/L的诱惑红溶液标准物质。采用制备液相色谱对筛选的市售原料纯化,得到纯度大于99%的诱惑红纯品;通过核磁共振(1HNMR谱)和液相色谱-质谱(HPLC-LTQ/MS)准确定性分析后,利用高效液相色谱法(HPLC)对诱惑红纯物质进行纯度定值。以0.1mol/L乙酸铵和甲醇为流动相进行等度洗脱,采用IntersilODS-C18(250mm×4.6mm,5μm)进行分离,检测波长240nm。为保证纯度测量的准确性,采用多家联合定值对诱惑红的纯度进行定值,诱惑红纯物质的定值纯度为99.61%(λ=240nm)。诱惑红溶液标准物质经重量-容量法配制后,进行均匀性和稳定性实验,浓度赋值后进行不确定度评定,诱惑红溶液的量值为100mg/L,扩展相对不确定度为1.0%(k=2)。该溶液标准物质已批准为国家级标准物质,可为相关部门提供检测标准。     

ICP－MS用于Eu_2O_3标准物质中铝和锌的定值分析

报道了用电感耦合等离子体质谱法测定氧比铕标准物质中Ａｌ_２Ｏ_３和ＺｎＯ的方法。考察了谱干扰和基体影响，采用Ｒｈ为内标较好地补偿了基体铕的影响。方法简便、快速，定值准确、可靠。