基于化学分析实验室标准物质管理分析

作为化学试验的重要环节,分析实验室在制药、能源开发、化工等行业上的作用不容小觑。由于其在平衡滴定、测量校准、控制质量等领域有着不可替代的作用,笔者基于此,以分析实验室对标准物质的管理规范为依托,就如何管理标准物质的基本要求做出判定,从而对实验室标准化管理提供了理论借鉴。     

分析影响白酒总酯检测准确度的因素

通过酚酞的加入量、氢氧化钠标准滴定溶液的加入量、皂化时间、滴定速度等多项试验,从而控制了总酯检测结果的准确性。     

标准滴定溶液浓度平均值不确定度的评定

目的对实验室自配氢氧化钠标准滴定溶液浓度平均值进行不确定度评定，建立不确定度评定程序和方法。方法依据GB／T601--2002《化学试剂标准滴定溶液的制备》建立数学模型，合成不确定度。结果找出了影响氢氧化钠标准滴定溶液浓度平均值的主要因素，归纳并提出了不确定度分量的主要来源，建立了用工作基准试剂标定标准滴定溶液浓度的不确定度评定程序和方法。结论评定程序和方法符合规范要求，适用于日常同类型实验不确定度评定。     

粮食脂肪酸值测定影响因素分析及优化

影响粮食脂肪酸值测定结果的因素很多,本文通过对前人少有研究的振荡器振幅、实验用水、指示剂、标准滴定溶液四个方面进行研究,探讨粮食脂肪酸值测定的优化方法。研究结果表明,振荡器振幅对测定结果存在显著影响,用三级水、百里香酚蓝指示剂、水溶剂氢氧化钾标准滴定溶液代替现行方法中的不含CO2的蒸馏水、酚酞指示剂、95%乙醇溶剂氢氧化钾标准滴定溶液对测定结果不存在显著影响。经优化后的方法简化了实验用水的制备,提高了测定效率;滴定终点的颜色变化易于观察,解决了“终点判定难”的问题;手工滴定法适用范围更广,不仅适用于普通粮食的脂肪酸值测定,还适用于其他“有色”粮食等特种粮食的脂肪酸值测定;水溶剂氢氧化钾标准滴定溶液的长期稳定性、短期稳定性都优于乙醇溶剂氢氧化钾标准滴定溶液,减少了因标准滴定溶液带来的误差。优化后的方法易于掌握,具有推广价值。     

食用酒精中醛的测定A.1碘量法不确定评定

食用酒精中醛的测定依据GB 31640-2016《食品安全国家标准食用酒精》附录A食用酒精中醛的测定A.1碘量法。对整个测量过程的不确定度来源进行分析评定,影响样品醛测量结果的不确定度来源主要碘标准滴定溶液、滴定酒精消耗碘标准滴定溶液体积V_1、滴定空白消耗碘标准滴定溶液体积V_2、吸取待测酒精溶液等引入的不确定度,对不确定度分量进行了详细的评定,得到了各分量不确定度和合成不确定度,最终得出更加客观的结果。     

谈影响白酒总酯检测准确度的因素

总酯是白酒质量检测中的一项重要指标。白酒总酯的测定有多种方法,在化验中,由于操作规范标准不统一,往往会造成检验结果的差异,通过NaOH标准溶液的配制,溶液的加入量、皂化时间、滴定速度等操作的统一,从而很好的控制总酯检测结果的准确性。     

工业用合成盐酸中总酸度测定结果的不确定度评定

建立测定工业用合成盐酸中总酸度不确定度的评定方法。主要参考GB/T 320—2006《工业用合成盐酸》和JJF1059.1—2012《测量不确定度评定与表示》,建立测定工业用合成盐酸中总酸度不确定度的数学模型,并对不确定度的各种来源进行分析和评定。通过分析可知,工业用合成盐酸中总酸度的不确定度来源主要有5个方面：重复性实验、标准滴定溶液体积、标准滴定溶液浓度、氯化氢摩尔质量、样品质量。最终得出此次总酸度测定结果为（35.44±0.04）%,k=2。不确定度贡献率最大的是标准滴定溶液浓度,达到49.50%;其次为标准滴定溶液体积和重复性实验,分别为33.66%和11.88%。     

硫酸标准滴定溶液浓度平均值不确定度的评定

化学试剂标准滴定溶液的配制和标定是粮食质量检验中最基本的操作之一,标准滴定溶液浓度的准确与否直接关系到检验结果的精准性。为保证检验结果的准确性,依据GB/T601—2002《化学试剂标准滴定溶液的制备》附录B《标准滴定溶液浓度平均值不确定度的计算》及《化学分析中不确定度的评估指南》,结合实际工作经验,对硫酸标准溶液0.1 mol/L的不确定度进行评定。     

滴定法测定橄榄油中酸值不确定度的评估

为了评估橄榄油酸值测定过程中的不确定度,对试验过程中的A类不确定度、NaOH标准滴定溶液、滴定体积、样品质量4个方面的相对标准不确定度进行分析计算.研究表明:在橄榄油酸值测定过程中,A类不确定度在不同的试验中所占有的比重不同.其中标准氢氧化钾溶液标定时,A类不确定度可忽略;而在酸值测定时,A类不确定度却占主要比重,同时滴定管的优劣对总的不确定度影响最大.     

EDTA标准滴定溶液不确定度评定

对0.1mol/LEDTA标准滴定溶液的标定过程引起的不确定度进行了评定,分析了EDTA标准溶液标定的不确定度主要来源。结果表明不确定度主要来源于消耗EDTA标准滴定溶液的体积产生的不确定度,其次是基准氧化锌纯度引起的质量分数的数值产生的相对标准不确定度。当配制0.1 mol/L EDTA时,由不确定度分量评定得到其扩展不确定度为0.005%。     

Reliable identification of grapevine rootstock varieties using RAPD PCR on woody samples

Since grapevine ( Vitis spp .) rootstock material is being traded increasingly as disbudded woody material a lack of distinctive morphological features on such material necessitates an alternative and reliable means of identification. Methods described here were developed for rapid and efficient extraction of DNA from woody samples rich in phenolic compounds and polysaccharides, and for subsequent identification of varieties by RAPD PCR. Using these methods, and with the application of only one selected RAPD primer, we were able to differentiate sixteen rootstock varieties, including the seven varieties most commonly used in Germany. Problems commonly encountered with reproducibility of RAPD patterns were avoided by choosing primers with a dinucleotide sequence and a high G/C content that allowed a rather high annealing temperature of 45°C. Methods described here should also be useful for other horticultural crops, especially those with woody tissues rich in phenolic compounds and polysaccharides.     

An internet compendium of analytical methods and spectroscopic information for monomers and additives used in food packaging plastics

An internet website (http://cpf.jrc.it/smt/) has been produced as a means of dissemination of methods of analysis and supporting spectroscopic information on monomers and additives used for food contact materials (principally packaging). The site which is aimed primarily at assisting food control laboratories in the European Union contains analytical information on monomers, starting substances and additives used in the manufacture of plastics materials. A searchable index is provided giving PM and CAS numbers for each of 255 substances. For each substance a data sheet gives regulatory information, chemical structures, physico-chemical information and background information on the use of the substance in particular plastics, and the food packaging applications. For monomers and starting substances (155 compounds) the infra-red and mass spectra are provided, and for additives (100 compounds); additionally proton NMR are available for about 50% of the entries. Where analytical methods have been developed for determining these substances as residual amounts in plastics or as trace amounts in food simulants these methods are also on the website. All information is provided in portable document file (PDF) format which means that high quality copies can be readily printed, using freely available Adobe Acrobat Reader software. The website will in future be maintained and up-dated by the European Commission's Joint Research Centre (JRC) as new substances are authorized for use by the European Commission (DG-ENTR formerly DGIII). Where analytical laboratories (food control or other) require reference substances these can be obtained free-ofcharge from a reference collection housed at the JRC and maintained in conjunction with this website compendium.     

Chlorohydrins of bisphenol A diglycidyl ether (BADGE) and of bisphenol F diglycidyl ether (BFDGE) in canned foods and ready-to-drink coffees from the Japanese market

BADGE.2HCl and BFDGE.2HCl were determined in 28 samples of ready-to-drink canned coffee and 18 samples of canned vegetables (10 corn, 5 tomatoes and 3 others), all from the Japanese market. HPLC was used as the principal analytical method and GCMS for confirmation of relevant LC fractions. BADGE.2HCl was found to be present in one canned coffee and five samples of corn, BFDGE.2HCl in four samples of canned tomatoes and in one canned corn. No sample was found which exceeded the 1mg/kg limit of the EU for the BADGE chlorohydrins. However the highest concentration was found for the sum of BFDGE.2HCl and BFDGE.HCl.H₂O at a level of 1.5mg/kg. A Beilstein test confirmed that all cans containing foods contaminated with BADGE.2HCl or BFDGE.2HCl had at lest one part coated with a PVC organosol.     

European priorities for research to support legislation in the area of food contact materials and articles

A strong science base is required to underpin the planning and decision-making process involved in determining future European community legislation on materials and articles in contact with food. Significant progress has been made in the past 5 years in European funded work in this area, with many developments contributing to a much better understanding of the migration process, and better and simpler approaches to food control. In this paper this progress is reviewed against previously identified work-areas (identified in 1994) and conclusions are reached about future requirements for R&D to support legislation on food contact materials and articles over the next 5 or so years.     

Aroma characterization of various apricot varieties using headspace–solid phase microextraction combined with gas chromatography–mass spectrometry and gas chromatography–olfactometry

The characterization of the aromatic profile of several apricot cultivars with molecular tracers in order to obtain objective data concerning the aromatic quality of this fruit was undertaken using headspace–solid phase microextraction (HS–SPME). Six apricot cultivars were selected according to their organoleptic characteristics: Iranien, Orangered, Goldrich, Hargrand, Rouge du Roussillon and A4025. The aromatic intensity of these varieties measured by HS–SPME–Olfactometry were defined and classified according to the presence and the intensity of grassy, fruity and apricot like notes. In the six varieties, 23 common volatile compounds were identified by HS–SPME–GC–MS. Finally, 10 compounds, ethyl acetate, hexyl acetate, limonene, β-cyclocitral, γ-decalactone, 6-methyl-5-hepten-2-one, linalool, β-ionone, menthone and (E)-hexen-2-al were recognized by HS–SPME–GC–O as responsible of the aromatic notes involved in apricot aroma and considered as molecular tracers of apricot aromatic quality which could be utilized to discriminate apricot varieties.     

Tests of potential functional barriers for laminated multilayer food packages. Part I: Low molecular weight permeants

The advent of the functional barrier concept in food packaging has brought with it a requirement for fast tests of permeation through potential barrier materials. In such tests it would be convenient for both foodstuffs and materials below the functional barrier (sub-barrier materials) to be represented by standard simulants. By means of inverse gas chromatography, liquid paraffin spiked with appropriate permeants was considered as a potential simulant of sub-barrier materials based on polypropylene (PP) or similar polyolefins. Experiments were performed to characterize the kinetics of the permeation of low molecular weight model permeants (octene, toluene and isopropanol) from liquid paraffin, through a surrogate potential functional barrier (25 μm-thick oriented PP) into the food simulants olive oil and 3% (w/v) acetic acid. These permeation results were interpreted in terms of three permeation kinetic models regarding the solubility of a particular model permeant in the post-barrier medium (i.e. the food simulant). The results obtained justify the development and evaluation of liquid sub-barrier simulants that would allow flexible yet rigorous testing of new laminated multilayer packaging materials.     

Textural Properties of Cold-set Gels Induced from Heat-denatured Whey Protein Isolates

A 9% whey protein (WP) isolate solution at pH 7.0 was heat-denatured at 80°C for 30 min. Size-exclusion HPLC showed that native WP formed soluble aggregates after heat-treatment. Additions of CaCl2 (10–40 mM), NaCl (50–400 mM) or glucono-delta-lactone (GDL, 0.4–2.0%, w/v) or hydrolysis by a protease from Bacillus licheniformis caused gelation of the denatured solution at 45°C. Textural parameters, hardness, adhesiveness, and cohesiveness of the gels so formed changed markedly with concentration of added salts or pH by added GDL. Maximum gel hardness occurred at 200 mM NaCl or pH 4.7. Increasing CaCl2 concentration continuously increased gel hardness. Generally, GDL-induced gels were harder than salt-induced gels, and much harder than the protease-induced gel.     

Influence des ions sur le pouvoir hydratant de l'ure e: e tude sur peau de porc ex vivo

This study deals with the influence of ions (NaCl and MgSO4) in a W/O emulsion containing 10% urea. Moisturization kinetics are assessed by corneometry on pig skin ex vivo. The formula's influence on urea penetration is measured by infrared spectrometry with an ATR device and the stripping method. Corneometry and spectroscopy were chosen to record simultaneously the hydratation levels and urea localization into superficial cell layers. Urea crystallization after evaporation of emulsions and aqueous solutions is described. Results show that urea does not hydrate nor penetrate when applied to the skin through an aqueous gel. In a W/O emulsion, sodium chloride increases the ability of urea to moisturize without improving penetration. In vitro urea crystallization is disturbed by sodium chloride or magnesium sulphate for solutions and emulsions. This stabilization by ions is correlated with good moisturization values. The stabilization of urea in the solute state provided by ions increases its water epidermal binding capacity without enhancing penetration.     

Analysis on Economic Indicators from 62 Enterprises in Printing Machinery Industry in Q1 2014

Operation of printing machine industry was still unsatisfactory in the first quarter of 2014.Analysis on operation of printing machine industry.a.Market demand was not strong;sales of product undulated and declined.According to the statistics,the total industrial output value fell by 19.28% in the first quarter of 2014 than the average quarter value in 2013; industrial added value decreased by 4.16%; sales revenue dropped by 22.83%. h. Business operation of enterprises was in poor condition. c. R＆D of new products is an important transformation guarantee for enterprises. d. To take self explore new ways upgrading advantages,and explore new ways.