汽车内饰材料燃烧特性的测量不确定度评定

依据GB 8410-2006测量汽车内饰材料的水平燃烧特性,对整个测试过程中的不确定来源进行分析,并对不确定度各个分量进行评定、合成,最后得出影响水平燃烧特性的主要因素是测试过程的重复性。     

密度瓶法测定糯米酒中酒精度的不确定度评定

目的评定密度瓶法测定糯米酒中酒精度的不确定度。方法分析测定过程中不确定度的来源;通过统计方法从测量重复性、温度计读数偏移、密度瓶校准、容量瓶的容量允差和天平校准等方面计算各分量的标准不确定度;最后计算合成不确定度和扩展不确定度。结果当糯米酒的酒精度为13.65%vol时,扩展不确定度U=0.11%vol (k=2)。结论密度瓶法测定糯米酒中酒精度过程中,密度瓶校准的不确定度分量所带来的影响最大,是该方法不确定度的主要来源;其次是是测量重复性;读数偏移、容量允差、天平称量的误差等对其测定不确定度的影响较小。     

档案字迹材料中光泽的不确定度分析与评定

现介绍了目前档案字迹材料中耐久性能的评价方法,以GB/T 13217.2-2009《液体油墨光泽检验方法》规定的方法为依据,进行光泽测试,为档案字迹材料提供一种新的评价方法。通过建立光泽的数学模型,对不确定度的来源进行了分析和评定。结果显示,重复性测量引入的不确定度贡献较大,仪器示值误差引入的不确定度贡献较小。     

旋光法测定木薯中淀粉含量不确定度评定

对采用旋光法测定木薯中的淀粉含量的不确定度进行评定。建立测量模型,分析确定木薯中淀粉含量的不确定度来源,并对测量过程中的不确定度分量进行逐层分析与合成,当木薯的淀粉含量为50.20 g/100 g时,得到其合成标准不确定度和扩展不确定度分别为0.16、0.32 g/100 g。结果表明,木薯总旋光度重复测定对不确定度贡献最大,总旋光度测定过程产生的不确定度也不容忽视,试样称量对总不确定度的贡献最小。实验结果可为采用该方法测定木薯中淀粉含量的质量控制提供理论依据。     

GFAAS法测定谷物中镉的不确定度评定

依据不确定度评定原理,分析石墨炉原子吸收法测定谷物中镉含量的测定步骤,确定其不确定度的不同来源,建立不确定度评定数学模型,对不确定度分量进行合成和扩展,最终给出不确定度评定报告。结果表明,石墨炉原子吸收法测定谷物中镉含量为(0.11±0.014)mg/kg,K为2。测量重复性和溶液测定引入的不确定度较大,样品定容和样品称量引入的不确定度较小。     

HPLC法测定饮料中日落黄含量的不确定度评定

对HPLC测定饮料中的日落黄含量测定结果进行不确定度分析,通过对各影响因素的不确定度评定,标准曲线拟合对饮料中合成着色剂的测量结果不确定度的影响最大,其次是样品处理回收率和实验重复性引入的不确定度对实验结果也有较大的影响。结果表明,饮料中日落黄的含量为(81.61±2.80)mg/kg,k=2。     

原子吸收法测定泡菜中铅含量的不确定度评定

目的采用原子吸收法对泡菜中铅含量进行测定不确定度评定。方法对泡菜中铅含量测定过程中各影响因素,包括称量、标准溶液配制、微波消解过程、仪器、标准曲线拟合等进行分析评定。结果该方法检测泡菜中铅的合成不确定度为3.02%,扩展不确定度为6.04%。本实验测定的泡菜中铅含量结果为(2.46±0.15)mg/kg(P=95%,k=2)。结论本实验的不确定度主要由微波消解过程、标准曲线拟合和仪器允差引入。     

HPLC法测定食品接触材料中BPA迁移量的不确定度评定

参考GB/T 23296.16-2009《食品接触材料高分子材料食品模拟物中2,2-二(4-羟基苯基)丙烷(双酚A)的测定高效液相色谱法》测定食品接触材料(金属空罐)的双酚A迁移量。通过分析测定过程中的各种不确定度来源,计算各不确定度分量,得出金属空罐的双酚A迁移量为0.005 53 mg/dm~2,扩展不确定度为0.000 38 mg/dm~2。比较各不确定度分量大小可知,高效液相色谱法测定食品接触金属空罐双酚A迁移量的不确定度主要来自双酚A标品的纯度和标准曲线的拟合。     

GC-MS内标法测定鞋类材料中邻苯二甲酸酯的不确定度评定

采用正己烷/丙酮作为溶剂,邻苯二甲酸二环己酯为内标物,使用气相色谱-质谱联用法(GC-MS)测定鞋类材料中6种邻苯二甲酸酯的含量.根据JJF 1059.1-2012《测量不确定度评定与表示》,建立了不确定度评价的数学模型,通过不确定度各分量的分析与评价,合成相对标准不确定度,其中标准曲线和标准物质是对测量不确定度的最主...     

原子吸收光谱法的不确定度评定

原子吸收光谱法广泛应用于食品中的微量元素和重金属的检测,检测结果的准确性与可信程度取决于不确定度的大小。根据原子吸收光谱分析的原理及实验过程,归纳原子吸收光谱法不确定度评定的步骤和方法。     

HS-GC/MS method development and exposure assessment of volatile organic compounds from food packaging into food simulants

ABSTRACT

A simultaneous headspace-gas chromatography/mass spectrometry (HS-GC/MS) method was developed and validated to determine the migration of 12 volatile organic compounds (methanol, acetone, methylethylketone, ethylacetate, isopropylalcohol, benzene, toluene, ethylbenzene, xylene, cumene, propylbenzene, and styrene) from food contact materials into food simulants (water, 4% acetic acid, 50% ethanol, and n-heptane). The limits of detection and quantification were 0.007–0.201 mg L^?1 and 0.023–0.668 mg L^?1, respectively. The method was applied to 205 samples of paper/paperboard, polyethylene, polypropylene, polystyrene, and polyethylene terephthalate. The estimated daily intake (EDI) was calculated using the migration results. Exposure assessments were carried out to compare the EDI to the tolerable daily intake (TDI); the results indicated that the EDI of styrene represented only a small percentage (8.0%) of the TDI. This analytical method will be a useful tool to examine levels of various volatile compounds migrating from food packaging to food simulants using HS-GC/MS method.     

汽车内饰纺织品中甲醛含量的测试方法探讨

简述四种国内外有关汽车内饰纺织品甲醛含量的检测方法,并进行比较,研究影响甲醛测定结果的诸因素,说明检测中应注意的问题。     

Milk volatile organic compounds and fatty acid profile in cows fed timothy as hay,pasture, or silage

Nutrient composition and organoleptic properties of milk can be influenced by cow diets. The objective of this study was to evaluate the forage type effects on volatile organic compounds, fatty acid (FA) profile, and organoleptic properties of milk. Timothy grass was fed as hay, pasture, or silage during a period of 27 d to a group of 21 cows in a complete block design based on days in milk. Each cow also received 7.2 kg/d of a concentrate mix to meet their nutrient requirements. Forage dry matter intake averaged 13.9 kg/d and was not different among treatments. Milk yield was higher for cows fed pasture, intermediate for cows fed silage, and lowest for cows fed hay. However, milk fat content was higher for cows fed hay and silage, compared with cows fed pasture. As a result, fat-corrected milk and fat yield were not different among treatments. Increasing the supply of dietary cis-9,cis-12 18:2 (linoleic acid) and cis-9,cis-12,cis-15 18:3 (α-linolenic acid) when feeding pasture enhanced the concentration of these 2 essential FA in milk fat compared with feeding hay or silage. Moreover, the ratio of 16:0 (palmitic acid) to cis-9 18:1 (oleic acid), which is closely related to the melting properties of milk fat, was lower in milk from cows on pasture than in milk from cows fed hay or silage. Cows fed hay produced milk with higher levels of several free FA and γ-lactones, but less pentanal and 1-pentanol. More dimethyl sulfone and toluene were found in milk of cows on pasture. Cows fed silage produced milk with higher levels of acetone, 2-butanone, and α-pinene. Results from a sensory evaluation showed that panelists could not detect a difference in flavor between milk from cows fed hay compared with silage. However, a significant number of assessors perceived a difference between milk from cows fed hay compared with milk from cows fed pasture. In a sensory ranking test, the percentage of assessors ranking for the intensity of total (raw milk, fresh milk, and farm milk), sweet (empyreumatic, vanilla, caramel, and sugar), and grassy (grass, leafy vegetable, and plant) flavors was higher for milk from cows fed pasture compared with hay and silage. Using timothy hay, pasture, or silage harvested at a similar stage of development, the current study shows that the taste of milk is affected by the forage type fed to cows. More research is, however, needed to establish a link between the sensory attributes of milk and the observed changes in volatile organic compounds and FA profile.     

Comparison of microbiota and volatile organic compounds in milk from different sheep breeds

In this study, we compared the microbiota and volatile organic compounds (VOC) present in the milk obtained from 3 different sheep breeds, namely Merino, Lacaune, and Assaf. Udder milk was collected from 21 animals, 7 from each breed. Bacterial microflora was determined metagenomically by extracting the DNA from the milk and analyzing the V3-V4 region of the 16S rRNA gene. Headspace solid-phase microextraction gas chromatography-mass spectrometry method was used to analyze VOC. The metagenomic analysis revealed (for Merino, Lacaune, and Assaf milk, respectively) Firmicutes (66.32, 69.36, and 57.08%), Actinobacteria (19.09, 7.67, and 19.40%), Proteobacteria (13.76, 21.06, and 22.19%), and Bacteroidetes (0.84, 1.91, and 1.33%) phyla in the milk samples. Lactobacillus was highly abundant in the milk of 3 breeds (29.64, 43.50, and 18.70%). The genera constituting more than 2% of all bacteria in all groups were Jeotgalicoccus (7.19, 5.34, and 10.77%), Enterococcus (5.18, 9.78, and 3.64%), and Corynebacterium (4.08, 3.00, and 13.44%). A total of 32 different VOC were identified by headspace solid-phase microextration analysis with 9, 30, and 24 different compounds from Merino, Lacaune, and Assaf breeds, respectively. Although ketone was the most abundant compound in Merino milk (71.84%), hydrocarbons were the most detected in Lacaune and Assaf milk (37.18% and 55.42%, respectively). A positive correlation was found between acetone, which was detected at the highest level in all groups, with Salinicoccus, Alloiococcus, Psychrobacter, and Dietzia. In addition, a negative correlation was found between the Lactobacillus genus, detected at the highest level in all groups, with methyl cyclopentane, 3-methylheptane, octane, decane, 3,3-dimethyloctane, and dodecane. Thus, differences were observed in the bacterial microflora and VOC in the sheep milk from different breeds under different feeding and breeding conditions.     

固相微萃取技术(SPME)分析羊奶中挥发性化合物

采用固相微萃取技术（SPME）提取羊奶中的挥发性化合物,经气相色谱质谱联用仪进行测定分析,实验结果表明,羊奶中挥发性化合物共检测到42种,主要成分为挥发性脂肪酸,酯类、醇和酮类,还含有一些其他挥发性化合物。其中挥发性脂肪酸有10种,主要由短链脂肪酸和中等长度碳链脂肪酸组成。酯类物质有16种,主要包括邻苯二甲酸二丁酯、邻苯二甲酸二乙酯、14-甲基-十五酸甲酯和己二酸二（2-乙基）乙酯等。另外挥发性醇类和酮类物质共7种,其它挥发性化合物9种。      

Emissions of volatile organic compounds originating from UK livestock agriculture

In this paper we estimate the quantity of non‐methane volatile organic compounds (NMVOCs) emitted from UK livestock. The final estimate is derived from published values and from direct measurements of NMVOC emissions from dairy cattle slurry and laying hen manure. Emission rates of NMVOCs were determined for fresh dairy cattle slurry and laying hen manure using a 40 m³ emissions chamber. Dimethyl sulphides dominated emissions from laying hen manure at 753 ± 263 g m^?3 day^?1. Emissions from dairy cattle slurry were dominated by volatile fatty acids (C₂? C₅, 6.3 ± 3.1 g m^?3 day^?1) and phenols (2.4 ± 1.2 g m^?3 day^?1). Many of these NMVOCs are decomposition products from protein sources from which ammonia is also a by‐product. There is a close association between ammonia and NMVOC production from manure, and on this basis we estimated the annual NMVOC emissions from UK livestock as 165 ± 56 kt for 2002. These emissions compare to those from the larger industrial and transport sectors and exceed the 50–100 kt C year^?1 currently determined as originating from biogenic sources including agriculture. These findings have implications for air quality, and these NMVOCs may affect the cleansing capacity of the troposphere. Copyright © 2004 Society of Chemical Industry     

离子色谱测定窖泥中4种有机酸的不确定度评定

为建立离子色谱法（IC）测定窖泥中乳酸、乙酸、丁酸和己酸4种有机酸含量不确定度的评定方法,通过参考JJF 1059.1—2012《测量不确定度评定与表示》和CNAS-GL06—2006《化学分析中不确定度的评估指南》中基本流程,建立模型、量化分量、合成标准不 确定度,得到乳酸、乙酸、丁酸和己酸4种有机酸的扩展不确定度,分别为42 mg/100 g、32 mg/100 g、16 mg/100 g、42 mg/100 g。 影响乳酸 和己酸不确定度的主要因素是重复性和水分含量,而影响乙酸和丁酸不确定度的主要因素是重复性、水分含量和标准曲线。 该研究 结果为窖泥中有机酸的进一步研究提供基础技术支撑。     

HS-SPME-GC-MS结合感官评价分析丹凤佳酿白酒的挥发性风味成分

为了解丹凤佳酿白酒的香气特征,利用顶空固相微萃取（HS-SPME）结合气相色谱-质谱联用（GC-MS）仪对该酒的挥发性成分进行分析,并结合感官检验分析该酒的主要香气轮廓。结果表明,从丹凤佳酿白酒中共鉴定出45种挥发性成分,包括酯类32种、醇类6种、醛酮类5种、酸类1种和其他类挥发性成分1种,其相对含量分别为94.51%、2.40%、1.77%、1.25%和0.07%,其中酯类、醇类和醛酮类为主要挥发性风味成分,醇香和果香是丹凤佳酿白酒的主要香气特征。该结果对研究特色浓香型白酒香气特点以及改良白酒的酿造工艺提供了数据参考。     

环境检测中挥发性有机物检测方法研究

为了使本文所讨论的方向得到有关部门的重视及支持,促进检测技术的进步,本文进行了一系列的检测和试验,介绍了环境中挥发性有机化合物的检测方式,并加强对环境试验中挥发性有机物的分析和总结,为今后的制备方法提供坚实的基础和标准.     

电感耦合等离子体质谱法测定有机肥中铅含量的不确定度评定

目的评定电感耦合等离子体质谱法测定有机肥中铅含量的不确定度。方法分析采用电感耦合等离子体质谱法测定有机肥中的铅含量中的影响因素,包括测定精密度、前处理、标准溶液的配制、标准曲线拟合等,计算各不确定度分量及扩展不确定度。结果在置信区间为95%的范围内,当有机肥样品所测铅浓度为0.782 mg/L时,最终计算扩展不确定度为0.0172 mg/L(k=2)。结论本方法适用于电感耦合等离子体质谱仪法测定有机肥中铅浓度的不确定度评定。