Differentiation of organically and conventionally produced milk by stable isotope and fatty acid analysis

Increasing sales of organic milk mean intensified tests for authenticity are required. In addition to comprehensive documentation, analytical methods to identify organic milk, and thus to differentiate it from conventional milk, are needed for consumer protection. Because the composition of milk is fundamentally dependent on the feeding of the cows, thirty-five samples from both production systems in Germany, including farm and retail milk, were collected within 12 months, to reflect seasonal variation, and appropriate properties were analysed. Fatty acid analysis enabled organic and conventional milk to be completely distinguished, because of the higher α-linolenic acid (C18:3ω3) and eicosapentaenoic acid (C20:5ω3) content of the former. Organic milk fat contained at least 0.56% C18:3ω3 whereas the maximum in conventional milk was 0.53%. Because of the parallel seasonal course of the C18:3ω3 content of organic and conventional retail samples, however, time-resolved comparison at the five sampling dates resulted in a clearer difference of 0.34 ± 0.06% on average. Analysis of stable carbon isotopes (δ¹³C) also enabled complete distinction of both types of milk; this can be explained by the different amounts of maize in the feed. For conventional milk fat δ¹³C values were −26.6‰ or higher whereas for organic milk fat values were always lower, with a maximum of −28.0‰. The time-resolved average difference was 4.5 ± 1.0‰. A strong negative correlation (r = −0.92) was found between C18:3ω3 and δ¹³C. Analysis of a larger number of samples is required to check the preliminary variation ranges obtained in this pilot study and, probably, to adjust the limits. Stable isotopes of nitrogen (δ¹⁵N) or sulfur (δ³⁴S) did not enable assignment of the origin of the milk; in cases of ambiguity, however, some trends observed might be useful in combination with other properties. Figure Correlation (r = −0.92) between δ¹³C value and C18:3ω3 content of milk fat from different production systems     

同步荧光光谱分析法在海面溢油鉴别中的应用研究

为了实现海面溢油快速筛选和鉴别,文章提出了应用同步荧光光谱技术结合系统聚类分析方法鉴别海面溢油的方法,并应用于不同原油样品及风化油样的分析。结果表明,选择波长差为25nm,采用300～500nm范围内数据进行聚类分析,可以将原油样品和风化样品完全区分开,不同海区、不同采集时间的原油样品可大致分开。作为溢油鉴别的一种辅助方法,同步荧光光谱分析法能够对可疑油源及溢油样品实现初步筛选。     

基于SVM的天津产地玫瑰香葡萄酒定性分析

利用红外光谱法对天津产地玫瑰香葡萄酒识别鉴定,提出了用支持向量机(SVM)算法对干白葡萄酒红外光谱图进行分析,详细介绍了干白葡萄酒谱图的预处理过程,包括基线校正、消除噪声、标准归一化和去除异常样本点。选取了不同产地的玫瑰香原酒样品511个、贵人香原酒样品438个、霞多丽原酒样品307个、白玉霓原酒样品29个、白羽原酒样品44个、龙眼原酒样品31个、泽香原酒样品79个,针对不同分类将80%样品谱图用SVM建立分类模型,并用剩余20%样品谱图对这些模型进行验证,实验结果表明该方法行之有效,不同葡萄品种干白葡萄酒模型正确率、识别率和拒绝率达到97%以上,不同产地玫瑰香干白葡萄酒正确率、识别率和拒绝率达到98%以上。该方法可以对天津产地玫瑰香葡萄酒进行定性识别鉴定。     

Comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometry for the identification of organobrominated compounds in bluefin tuna

This study evaluates comprehensive two-dimensional gas chromatography (GC×GC) coupled to time-of-flight mass spectrometry (GC×GC-ToF MS) for the simultaneous analysis of several classes of organobromines (OBs), including polybrominated diphenyl ethers (PBDEs), polybrominated biphenyls (PBBs), methoxylated PBDEs (MeO-PBDEs), several halogenated naturally produced compounds (HNPs) and eight novel brominated flame retardants (NBFRs), polybrominated hexahydroxanthene derivates (PBHDs), 2,4,6-tribromoanisole and a mixed halogenated compound (MHC-1), in bluefin tuna muscles. The proposed methodology maximised separation of both within and among OB families, and among these and other halogenated micropollutants detected in these samples and co-extracted matrix components. Special attention has been paid to solve co-elution problems observed during the analysis of OBs with one-dimensional GC-based techniques. Satisfactory separation among several relevant PBDEs and MeO-PBDEs has been obtained allowing their unambiguous determination in a single run. Additional studies were conducted to identify selected NBFRs and HNPs. 2,4-Dibromoanisole, a dibromophenol isomer and hexabromobenzene were identified in the investigated samples. Several new tri- and tetra-BHD derivates were also identified, indicating that these compounds could apparently exist as structured families in nature. In addition, a tetrabrominated diMeO-biphenyl and two tetrabrominated diMeO-BDEs were also tentatively identified.     

Direct identification of bacteria in blood culture by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry: a new methodological approach

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) has recently been demonstrated to be a powerful tool for the rapid identification of bacteria from growing colonies. In order to speed up the identification of bacteria, several authors have evaluated the usefulness of this MALDI-TOF MS technology for the direct and quick identification bacteria from positive blood cultures. The results obtained so far have been encouraging but have also shown some limitations, mainly related to the bacterial growth and to the presence of interference substances belonging to the blood cultures. In this paper, we present a new methodological approach that we have developed to overcome these limitations, based mainly on an enrichment of the sample into a growing medium before the extraction process, prior to mass spectrometric analysis. The proposed method shows important advantages for the identification of bacterial strains, yielding an increased identification score, which gives higher confidence in the results.     

Transfer function identification from impulse response via a new set of orthogonal hybrid functions (HF)

The present work proposes a new set of hybrid functions (HF) which evolved from the synthesis of sample-and-hold functions (SHF) and triangular functions (TF). Traditional block pulse functions (BPF) still continue to be attractive to many researchers in the arena of control theory. Block pulse functions also gave birth to a few useful variants. Two such variants are SHF and TF. The former is efficient for analyzing sample-and-hold control systems, while triangular functions established their superiority in obtaining piecewise linear solution of various control problems. After developing the basic theory of HF, a few square integrable functions are approximated via this set in a piecewise linear manner. For such approximation, it is shown, the mean integral square error (MISE) is much less than block pulse function based approximation. The operational matrices for integration in HF domain are also derived. Finally, this new set is employed for solving identification problem from impulse response data. The results are compared with the solutions obtained via BPF, SHF, TF, etc. and many illustrations are presented.     

High-performance liquid chromatography-time-of-flight mass spectrometry with adjustment of fragmentor voltages for rapid identification of alkaloids in rat plasma after oral administration of rhizoma Corydalis extracts

A tandem high-performance liquid chromatography and time-of-flight mass spectrometry method has been developed for rapid separation and identification of alkaloids in rat plasma after oral administration of rhizoma Corydalis extracts. Compounds were separated on a Zorbax XDB-C(18) column and the linear gradient elution was used with the mobile phase consisting of ammonium acetate-0.01% acetic acid and acetonitrile. Mass spectra were acquired by electrospray ionization in the positive ion mode. Fifteen components were detected in vitro, among which 12 components were rapidly identified based on the accurate-mass capability of time-of-flight analyzer. Eleven prototype components were detected in dosed rat plasma (in vivo). Three isomers, which had the same [M+H](+) ion at m/z 356.1856, were distinguished as glaucine, tetrahydropalmatine, and corybulbine by dynamic adjustment of fragmentor voltages. This study developed a rapid and sensitive method that was successfully utilized for screening the active ingredients of rhizoma Corydalis in rat plasma, which provided helpful information for further pharmacokinetic research of active components in this medicine.     

基于太赫兹谱分析中药材鉴别

中草药分析与鉴定对中草药质量控制意义重大,以飞秒激光为基础的太赫兹时域光谱技术(THz-TDS)是一种新型相干远红外光谱测量技术。为了研究基于太赫兹谱的中药材鉴别可行性,应用THz-TDS研究了室温下黄芪、当归、杜仲及三种掺杂的黄芪在0.2~2.2 THz范围内的光学特性,得到了对应的时域谱、频域谱和吸收谱。结果表明在此波段三种中草药的时域谱、频域谱及吸收谱存在显著差异;三种掺杂黄芪的频域谱、吸收谱虽相似但也有明显不同。利用太赫兹时域光谱技术鉴别中药材是可行的,它可为中草药质量控制提供一种新的方法。     

九种蔷薇科植物叶片的傅里叶红外光谱与亲缘关系分析

以蔷薇科三个亚科九种植物的叶为材料,利用傅里叶变换红外光谱法对九种植物进行亲缘关系分析和品种鉴定。叶中主要含有大量的碳水化合物、蛋白质、脂类、核酸等物质。糖类物质的峰主要在1 440～775 cm-1之间,1 440～1 337 cm-1为纤维素、木质素的振动峰,1 000～775 cm-1为核糖的伸缩振动。蛋白质的峰主要在1 620～1 235 cm-1之间,1 620 cm-1为蛋白质酰胺Ⅰ带的CO伸缩振动,1 523 cm-1为蛋白质酰胺Ⅱ带N—H和C—N吸收峰。脂类物质的峰主要出现在2 930～1 380 cm-1之间,2 922 cm-1为脂肪CH₂的伸缩振动,1 732 cm-1是脂肪酸CO的伸缩振动。核酸的标志峰出现在1 250～1 000 cm-1,1 068 cm-1是磷酸基团的对称伸缩振动,1 246 cm-1是磷酸基团的不对称伸缩振动。研究结果表明：FTIR光谱数据经平滑、标准化处理、二阶求导、主成分分析和系统聚类建立的聚类分析模型与传统分类结果相一致。杏、樱桃聚为一类(李亚科),翻白叶、月季、草莓聚为第二类(蔷薇亚科),火棘、苹果、枇杷、海棠聚为第三类(苹果亚科),亚科聚类正确率为100%,但属聚类的正确率仅为55.56%。利用该聚类模型进行物种鉴定正确率为100%。该项研究为植物的亲缘关系分析提供了新的思路与方法。