热裂解-气相色谱质谱联用法快速检测聚丙烯材料中5种抗氧剂

采用热裂解气质联用仪,建立了一种无需任何样品前处理、全程无溶剂的、同时对5种常用塑料抗氧剂的定量分析方法.结果表明:通过该方法分析的5种常用抗氧剂,在0.2～1μg之间有很好的线性关系,且该方法操作简单、 快速准确,填补了热裂解气质联用技术在塑料助剂定量分析的空白.     

阀切换技术在大气样品SF_6快速分析中的应用

建立了双柱阀切换技术分析大气样品中SF_6浓度的GC—ECD方法。采用φ3.2 mm×1 m 5A分子筛(粒径为0.246～0.369 mm)柱为预柱,φ3.2 mm×0.5 m 5A分子筛(粒径为0.1 75～0.246 mm)柱为分析柱。在实验条件下,平均峰高响应为1.08×10~(-14)mL/μV,SF_6峰高响应的相对标准偏差为2.2%,SF_6的最低检测限为6.03×10~(-13)mL(3倍基线噪音)。采用该方法分析大气中SF_6浓度,样品分析时间为1.2 min,大大缩短了样品分析时间。12 min内完成11个空气样品分析,相对标准偏差2.1%。     

Evaluation of the uncertainty associated to tar sampling with solid phase adsorption cartridges

The uncertainty evaluation associated with the quantification of tar with the use of solid phase adsorption for tar sampling and gas chromatography analysis is present. The study shows that the major contribution to the overall uncertainty is related to the extraction step. Relevant tar compounds are selected and used as model to quantify the uncertainty and for comparison with the uncertainty associates to the traditional methodology for tar sampling. The study indicates that the uncertainty associated to the tar sampling with solid phase adsorption cartridges is lower than the uncertainty associated to the tar sampling with impinger bottles.     

Rapid gas-chromatographic method for the determination of diacetyl in milk, fermented milk and butter

In this work, a simple and fast method for the determination of diacetyl by gas-chromatographic technique coupled with flame ionisation detector (GLC-FID) was developed. Diacetyl is the typical butter flavour, but it is also commonly present in others fermented dairy products. Recently, diacetyl determination has also attracted interest because it is one of the parameters on which lactic acid bacteria (L.A.B.) are characterized and valued. Only acetone and 2,3-pentanedione were used as chemicals. After centrifugation of acetone–milk mixture, supernatant was filtered and directly injected into gas-chromatographic apparatus, without a further purification procedure step.

This method was accurate and precise; diacetyl recovery on milk was 97% and the detection limit was 1 mg L⁻¹. Finally, by using this method, diacetyl was easily determined in fresh and high-temperature treated milk, commercial butter, yoghurt and also in a series of L.A.B. performance tests.     

Cholesterol oxidation in pasta produced with eggs of different origin

Cholesterol oxidation was studied in 12 samples of mass-produced egg pasta and in home-made egg pasta produced with fresh eggs obtained from hens bred in the open with organic methods (a), fresh eggs purchased in a local retail shop (b) and spray-dried eggs, which are not allowed by Italian law (c). The lipids of commercial egg pasta contained almost twice the concentration of cholesterol of hand-made egg pasta (2.6 vs. 1.4 mg/100 mg lipids). Mass-produced egg pasta contained 2.2±1.5 g oxycholesterols (cholesterol oxidation products, or COPs)/g of pasta, Epo being the most represented oxycholesterol. The oxycholesterol content in home-made pasta was 1.7, 3.5 and 3.6 g/g pasta, for pasta obtained with samples a, b and c, respectively. 7-Hydroxycholesterol and -epoxy-cholesterol were not taken in account, because they co-eluted with campesterol and campestanol, respectively. The home-made procedure (eggs mixed with flour and water and dried for 48 h at 30 °C) led to the formation of 7 k and 7, rather than Epo. The use of eggs from hens bred in the open reduced the COPs content considerably. The home-made product should be consumed within a few days after manufacturing or should be immediately refrigerated.     

Dietary intake of pesticides: State of Kuwait total diet study

The State of Kuwait conducted a total diet study (TDS) to determine the dietary intakes of selected pesticides. This paper reports the results of this study. A national food consumption survey was performed and core food lists for different population groups were established representing the total diet of the Kuwaiti population. Food items (table-ready) were purchased/prepared and analysed for their contents of organophosphate/organochlorine carbamate, benzimidazole and phenylurea pesticides according to the US FDA Pesticide Analytical Manual (PAM I). Dietary intakes of these pesticides are presented for 19 population groups, which range from infants to elderly adults. The intakes of selected population groups are compared with representative findings from the US FDA/TDS and data published from other countries. In general, the average daily intakes were well below acceptable limits, but higher than those reported from developed countries.     

Chemical compositional characterization of some apple cultivars

Eight commercially harvested apple cultivars were analysed by gas chromatography and high-performance liquid chromatography, in particular the composition and level of sugars, organic acids, amino acids, phenolic compounds and fatty acids. The results showed great quantitative differences in the composition of the apple cultivars, particularly in their phenolic contents. Fructose was the most dominant sugar in the different apple cultivars, followed by glucose and sucrose, while malic acid was the principal organic acid. The C16:0, C18:0, C18:1, C18:2 and C18:3 fatty acids were the most abundant fatty acids, and the C18 family accounted for more than 70% of the total fatty acids content. Asparagine and serine were the principal amino acids. Chlorogenic acid and protocatechuic acid were the dominating phenolic compounds. The results provide important information on how to make the best use of the apple cultivars investigated, for both technological research and processing practice.