气相滴定在臭氧计量标准溯源中的应用

利用臭氧和一氧化氮发生快速反应生成二氧化氮的原理,设计气相滴定反应系统,通过对参加反应的一氧化氮标准气体浓度变化的准确测定,计算出组分臭氧混合气体的浓度。利用设计的气相滴定系统（GPT）,对基于紫外分光原理的臭氧测量标准装置SRP41产生的空气中臭氧标准气体进行了比对及相互验证。比对结果表明：二者偏差不大于2．6％,均在分析不确定度范围内等效。这为臭氧测量计量溯源问题提供了解决方案。     

1H-NMR Profiling Shows as Specific Constituents Strongly Affect the International EVOO Blends Characteristics: The Case of the Italian Oil

Considering the growing number of extra virgin olive oil (EVOO) producers in the world, knowing the influence of olive oils with different geographical origins on the characteristics of the final blend becomes an interesting goal. The present work is focused on commercial organic EVOO blends obtained by mixing multiple oils from different geographical origins. These blends have been studied by ¹H-NMR spectroscopy supported by multivariate statistical analysis. Specific characteristics of commercial organic EVOO blends originated by mixing oils from Italy, Tunisia, Portugal, Spain, and Greece were found to be associated with the increasing content of the Italian component. A linear progression of the metabolic profile defined characteristics for the analysed samples—up to a plateau level—was found in relation to the content of the main constituent of the Italian oil, the monocultivar Coratina. The Italian constituent percentage appears to be correlated with the fatty acids (oleic) and the polyphenols (tyrosol, hydroxytyrosol, and derivatives) content as major and minor components respectively. These results, which highlight important economic aspects, also show the utility of ¹H-NMR associated with chemometric analysis as a powerful tool in this field. Mixing oils of different national origins, to obtain blends with specific characteristics, could be profitably controlled by this methodology.     

Inorganic Elements in Mytilus galloprovincialis Shells: Geographic Traceability by Multivariate Analysis of ICP-MS Data

The international seafood trade is based on food safety, quality, sustainability, and traceability. Mussels are bio-accumulative sessile organisms that need regular control to guarantee their safe consumption. However, no well-established and validated methods exist to trace mussel origin, even if several attempts have been made over the years. Recently, an inorganic multi-elemental fingerprint coupled to multivariate statistics has increasingly been applied in food quality control. The mussel shell can be an excellent reservoir of foreign inorganic chemical species, allowing recording long-term environmental changes. The present work investigates the multi-elemental composition of mussel shells, including Al, Cu, Cr, Zn, Mn, Cd, Co, U, Ba, Ni, Pb, Mg, Sr, and Ca, determined by inductively-coupled plasma mass-spectrometry in Mytilus galloprovincialis collected along the Central Adriatic Coast (Marche Region, Italy) at 25 different sampling sites (18 farms and 7 natural banks) located in seven areas. The experimental data, coupled with chemometric approaches (principal components analysis and linear discriminant analysis), were used to create a statistical model able to discriminate samples as a function of their production site. The LDA model is suitable for achieving a correct assignment of >90% of individuals sampled to their respective harvesting locations and for being applied to counteract fraud.     

化学计量研究进展

叙述了化学计量的特点、作用和重要性及其研究内容,探讨了标准物质量值传递系统及实现标准物质量值溯源性的途径,阐述了建立化学测量溯源性的重要性、困难性、复杂性及基本设想和途径,并对化学计量中物质的量“摩尔”进行了简要论述。     

Elemental Chemometrics as Tools to Depict Stalked Barnacle (Pollicipes pollicipes) Harvest Locations and Food Safety

The stalked barnacle Pollicipes pollicipes is an abundant species on the very exposed rocky shore habitats of the Spanish and Portuguese coasts, constituting also an important economical resource, as a seafood item with high commercial value. Twenty-four elements were measured by untargeted total reflection X-ray fluorescence spectroscopy (TXRF) in the edible peduncle of stalked barnacles sampled in six sites along the Portuguese western coast, comprising a total of 90 individuals. The elemental profile of 90 individuals originated from several geographical sites (N = 15 per site), were analysed using several chemometric multivariate approaches (variable in importance partial least square discriminant analysis (VIP-PLS-DA), stepwise linear discriminant analysis (S-LDA), linear discriminant analysis (LDA), random forests (RF) and canonical analysis of principal components (CAP)), to evaluate the ability of each approach to trace the geographical origin of the animals collected. As a suspension feeder, this species introduces a high degree of background noise, leading to a comparatively lower classification of the chemometric approaches based on the complete elemental profile of the peduncle (canonical analysis of principal components and linear discriminant analysis). The application of variable selection approaches such as the VIP-PLS-DA and S-LDA significantly increased the classification accuracy (77.8% and 84.4%, respectively) of the samples according to their harvesting area, while reducing the number of elements needed for this classification, and thus the background noise. Moreover, the selected elements are similar to those selected by other random and non-random approaches, reinforcing the reliability of this selection. This untargeted analytical procedure also allowed to depict the degree of risk, in terms of human consumption of these animals, highlighting the geographical areas where these delicacies presented lower values for critical elements compared to the standard thresholds for human consumption.     

Nanometer Calibration Particles: What is Available and What is Needed?

Information on available polystyrene calibration spheres is presented regarding the particle diameter, uncertainty in the size, and the width of the size distribution for particles in a size range between 20 and 100nm. The use of differential mobility analysis for measuring the single primary calibration standard in this size range, 100nm NIST Standard Reference Material®1963, is described along with the key factors in the uncertainty assessment. The issues of differences between international standards and traceability to the NIST Standard are presented. The lack of suitable polystyrene spheres in the 20–40nm size range will be discussed in terms of measurement uncertainty and width of the size distributions. Results on characterizing a new class of molecular particles known as dendrimers will be described and the possibilities of using these as size calibration standards for the size range from 3 to 15nm will be discussed.     

A system of metrological assurance of measurement quality for the determination of chemical composition of light alloys and superalloys

 The paper covers the main principles of setting up and the function of the Russian system of metrological assurance of analytical measurements for the production of light alloys and superalloys. Received: 20 October 1998 / Accepted: 9 November 1998     

Estimation of metrological characteristics of the element analyzer EuroVector EA-3000 and its potential in the single-reactor CHNS mode

The bulk of the analytical data of a long period was used for estimation of RSD values of the CHNS analysis results obtained by EuroVector EA-3000 in the single-reactor mode. It is shown that the accident error level is conducted with the sample preparation procedure as well as with the properties of the certain analyzed samples. It is established that the experimental obtained CHNS analysis error levels significantly differ from those given in the technical specifications. In case of analysis of sample with the unknown composition the accidental errors of determination of each element are comparable with the standard sample ones.     

Review: Authentication and traceability of foods from animal origin by polymerase chain reaction-based capillary electrophoresis

This work presents an overview of the applicability of PCR-based capillary electrophoresis (CE) in food authentication and traceability of foods from animal origin. Analytical approaches for authenticating and tracing meat and meat products and fish and seafood products are discussed. Particular emphasis will be given to the usefulness of genotyping in food tracing by using CE-based genetic analyzers.     

化学计量中的质量保证

从化学计量的特点出发,根据测量保证原理的基本要求,简述了化学计量中保证量值准确可靠的几个重要环节的过程控制。