XPS analysis of bio‐organic systems

A survey of the literature is made for the XPS analysis of food products (mainly spray‐dried powders, which reveal a considerable surface enrichment in lipids) and of microorganisms and related systems (extracellular polymer substances and biofilms). This survey is used as a background for discussions and recommendations regarding methodology. Sample preparation methods reviewed are freeze drying, analysis of frozen hydrated specimens and adsorption of surface‐active biocompounds on model substrates. Peak decomposition is a way to increase the wealth of information provided by the XPS spectra. It should be performed after a check that sample charge stabilization is satisfactory. Moreover, ensuring the precision needed to make comparisons within sets of samples may involve a trade‐off between imposing constraints and generating information. The examination of correlations between spectral data in the light of chemical guidelines is useful to validate or improve peak decomposition and component assignment, and may also upgrade the chemical information regarding speciation. Further upgrading may be achieved by expressing marker XPS data in terms of concentrations of compounds of interest. Different methods of computation are discussed, providing a composition in terms of ingredients, classes of biochemical compounds, or various organic and inorganic compounds. As an alternative or complement to this deterministic approach, multivariate analysis of suitable spectral windows provides spectral components, which may be used for comparing samples, and which may have a direct chemical relevance or be used to identify features of interest. Copyright © 2011 John Wiley & Sons, Ltd.     

HPLC-MS/MS测定氯羟吡啶在牛奶中的残留

建立了牛奶中氯羟吡啶残留检测的高效液相色谱-串联质谱方法(HPLC-MS/MS)。样品经乙腈提取,碱性氧化铝固相萃取柱(Alumina-B)净化,以乙腈+0.1%甲酸水溶液作为流动相洗脱,采用电喷雾离子源(ESI),多反应监测(MRM)方式进行采集,外标法定量。结果表明,氯羟吡啶在1~200ng·m L-1浓度范围内呈现良好的线性关系,相关系数R2大于0.99,方法检测限为0.2μg·kg-1,从5、10和50μg·kg-13个水平添加浓度检测结果可以看出,方法回收率在93.4%~102.6%,相对标准偏差不大于6.5%。     

聚多巴胺修饰棉花固定金属离子用于磷酸化多肽的富集

本文通过多巴胺自聚合在天然的棉花纤维表面,构建了仿生聚多巴胺(PDA)膜层,然后利用儿茶酚羟基固定Ti~(4+),设计并合成了一种固定金属亲合色谱(Immobilized Metal Ion Affinity Chromatography,IMAC)材料Cotton@PDA-Ti~(4+),并将其用于磷酸化多肽的富集。该材料机械性能好,化学性能稳定和生物相容性好,且制备过程简单,通过简易的In-pipet-tip固相萃取(SPE)装置使整个富集操作过程简便快速。实验结果表明,Cotton@PDA-Ti~(4+)不仅可以从简单的蛋白酶解物(β-casein)中富集磷酸化多肽,并且在含有大量非磷酸化多肽的复杂体系样品中对磷酸化多肽也表现出良好的选择性。另外,利用Cotton@PDA-Ti~(4+)对磷酸化多肽进行富集也有较高的效率。我们将该材料应用于实际样品,如人体血清以及脱脂牛奶酶解物中磷酸化多肽的富集,均表现出了较好的选择性。说明该方法有可能用于磷酸化蛋白质组的全分析。     

A study of enhanced ion formation from metal‐semiconductor complexes in atmospheric pressure laser desorption/ionization mass spectrometry

The study of the key parameters impacted surface‐assisted laser desorption/ionization‐mass spectrometry is of broad interest. In previous studies, it has been shown that surface‐assisted laser desorption/ionization‐mass spectrometry is a complex process depending on multiple factors. In the presented study, we showed that neither porosity, light absorbance nor surface hydrophobicity alone influence the enhancement phenomena observed from the hybrid metal‐semiconductor complexes versus individual targets, but small changes in the analyte attaching to the target significantly affect laser desorption ionization‐efficiency. By means of Raman spectroscopy and scanning electron microscopy, it was revealed that the formation of an amorphous analyte layer after drying on a solid substrate was essential for the enhanced laser desorption ionization‐signal observed from the hybrid metal‐semiconductor targets, and the crystallization properties of the analyte appeared as a function of the substrate. Obtained results were used for the screening of regular and lactose‐free milk samples through the hybrid metal‐semiconductor target. Copyright © 2016 John Wiley & Sons, Ltd.     

Lactic acid bacteria in dairy food: Surface characterization and interactions with food matrix components

This review gives an overview of the importance of interactions occurring in dairy matrices between Lactic Acid Bacteria and milk components. Dairy products are important sources of biological active compounds of particular relevance to human health. These compounds include immunoglobulins, whey proteins and peptides, polar lipids, and lactic acid bacteria including probiotics. A better understanding of interactions between bioactive components and their delivery matrix may successfully improve their transport to their target site of action. Pioneering research on probiotic lactic acid bacteria has mainly focused on their host effects. However, very little is known about their interaction with dairy ingredients. Such knowledge could contribute to designing new and more efficient dairy food, and to better understand relationships between milk constituents. The purpose of this review is first to provide an overview of the current knowledge about the biomolecules produced on bacterial surface and the composition of the dairy matter. In order to understand how bacteria interact with dairy molecules, adhesion mechanisms are subsequently reviewed with a special focus on the environmental conditions affecting bacterial adhesion. Methods dedicated to investigate the bacterial surface and to decipher interactions between bacteria and abiotic dairy components are also detailed. Finally, relevant industrial implications of these interactions are presented and discussed.     

X射线荧光光谱法测定原煤中氯量

提出了煤粉直接压片制样-X射线荧光光谱法测定原煤中氯量。将粒径小于74μm的原煤粉末经90℃烘干后置于聚乙烯模具中,以4.16 MPa压力制成直径为35 mm的样片,制成的样品保存于干燥器中应尽快进行测定。选用煤标准物质制作氯的测定范围为0.01%～0.11%(质量分数)之间的标准曲线,并建立了集校准曲线、基体校正及谱线重叠校正为一体的回归方程作为方法的定量基础。求得方法的检出限为15μg·g~(-1)。用同一标准物质(ω_(Cl)0.057%)重复测定12次,测得其相对标准偏差为1.85%。用所提出的方法测定了2个煤标准物质,所得结果与认定值一致。     

离子色谱法测定液体乳制品中硫氰酸盐

提出了离子色谱法测定液体乳中硫氰酸盐的方法。鲜奶或酸奶样品经乙腈提取和C18固相萃取柱净化后,再经Ion Pac AG11-HG保护柱及Dionex ICS-3000分离柱分离,由70 mmol.L-1氢氧化钾溶液洗脱,利用电导检测器检测。硫氰酸盐的质量浓度在0.20～10.0 mg.L-1范围内呈线性,方法的检出限(3S/N)为0.08 mg.L-1。方法用于鲜奶和酸奶样品分析,回收率在92.5%～104.5%之间,相对标准偏差(n=6)小于4.5%。     

生鲜供应链中保鲜努力投入及订货定价研究

结合生鲜损耗严重和过度保鲜双重背景,本文在区分保质期和实际有效供货时长的基础上,比较研究了由单一零售商与单一供应商构成的二级生鲜供应链中,两个主体合作与否及主导主体变化对供应链保鲜努力水平和定价的影响机制。研究表明,集中式供应链中,保鲜努力投入随新鲜度(价格)敏感性增强(减弱)而增加,而随有效供货时长增加呈倒U型;供应链的总利润也随新鲜度(价格)敏感性增强(减弱)或有效供货时长上升而增加。分散式供应链中,随新鲜度的敏感性增强,保鲜努力和总利润增加;随价格的敏感性增强,保鲜努力增加而总利润减小;而随有效供货时长上升,保鲜努力先增大后减小,总利润增加。分散式供应链存有搭便车的机会,但因有效供货时长占保质期比例不同,自身投入保鲜努力可能比搭便车更有利。     

基于质量分级的生鲜农产品供应链的定价与保鲜策略研究

为了有效降低生鲜农产品损耗,保障流通与销售过程中生鲜农产品的品质及安全,解决消费者对生鲜农产品品质及其新鲜度的高追求与生鲜农产品冷链物流成本过高导致保鲜投入不足之间的矛盾,文中以价格和新鲜度为市场需求的主要影响因素,分别在产销地均不分级、销地分级和产地分级三种质量分级模式下,构建了供应商和零售商的利润函数,采用stackelberg博弈求解得到各自的最优定价策略和最优保鲜策略.对不同质量分级模式下的定价策略和保鲜策略进行对比分析显示,产地分级模式下的定价策略有利于增加市场需求及市场主体的利润;产地分级模式下的保鲜策略在控制损耗的效果和控制保鲜的成本上都优于其他模式.     

基于突变级数-灰靶的生鲜电商O2O成熟度模型

为了对生鲜农产品电商O2O水平做出评估,本文设计了生鲜电商与传统流通体系融合发展的成熟度模型,确定了成熟度模型五个层级的十七个关键过程域及其目标。通过实例,运用突变级数法和灰靶决策对超市生鲜农产品020的成熟度进行了评估,使其发现经营过程中的薄弱环节并改善,向成熟度更高一层级迈进。结合突变级数和灰靶决策的成熟度模型避免了赋权的主观性,既提高了生鲜农产品电商与传统流通体系融合发展成熟度模型评估的准确性,又不失可靠性、合理性以及科学性,具有重要的实用价值。