Comparison of sample preparation methods for the ICP-AES determination of minor and major elements in clarified apple juices

Inductively coupled plasma atomic emission spectrometry (ICP-AES) was used for the determination of minor and major elements present in apple juices. Prior to ICP-AES measurement, samples were diluted with nitric acid or digested in a microwave assisted digestion system. The differences in the measured element concentrations after application of different types of sample preparation procedures are discussed. The direct measurement compared to closed microwave dissolution was found to be the best sample preparation procedure. Prior to the measurements the ICP-AES method was validated and optimized for the determination of elements in apple juices. For diluted apple juice samples the lowest limits of detection (LOD) were obtained for Ba and Cd (< 20 μg L^{− 1}), moderate ones for Cu, Mn, Ni, Fe, Ag, Ca, Cr, Zn, Mg, and Sr (20–100 μg L^{− 1}), and the highest LODs for K, Pb, Na, and Al (> 110 μg L^{− 1}). The results obtained for the repeatability (< 0.9%), the intermediate precision (< 4.5%), the day-to-day reproducibility (< 5.2%), and the overall uncertainty of measurement (approx. 4–7%) for all elements analyzed demonstrated the good applicability of the proposed method. Differences in major element content in fresh and commercial apple juice are discussed.     

Kinetic and thermodynamic study of inter‐ and intramolecular proton transfer in N′‐acetyl formohydrazide tautomers

Nine tautomers and eleven possible tautomeric interconversions of N′‐acetyl formohydrazide have been studied at B3LYP/6‐311++G** level of theory. From these calculations, optimized geometries, molecular parameters, IR frequencies, NMR chemical shifts, and energetic results are obtained. In all tautomers except tautomers 4, E isomer is more stable than Z isomer. Energetic data were used to calculate the energy barriers of tautomeric interconversions and very high energy barriers were obtained for all tautomeric interconversions. Moreover, study of solvent effects on relative stabilities of tautomers and transition states showed that they are similar to those in the gas phase. In addition, intermolecular proton transfer with the assistance of one to three water molecules has been studied and the results showed that activation barriers in water‐assisted tautomerism are in general lower than those in the gas phase. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2011     

超声波辅助稠油层内催化水热裂解实验研究

将超声波应用到稠油催化水热裂解实验中,研究了超声波辅助催化水热裂解对胜利油田孤东稠油物化性质的影响。结果表明,超声波辅助作用下稠油的降黏率达到86.2%,与催化水热裂解相比,稠油的平均相对分子质量进一步减小,饱和烃和芳香烃组分含量增加,胶质和沥青质组分含量减少,稠油组分的氢碳原子比增加,杂原子含量减小。动态模拟实验中超声波辅助层内催化水热裂解效果显著,稠油采收率达到53.91%,降黏率达到80.5%。由此表明,超声波辅助催化水热裂解具有可行性,超声波与催化剂协同作用促进了水热裂解反应,一定程度上改善了稠油的品质。     

应用超高分辨质谱成像技术研究脂类分子在小鼠肝组织中的分布

利用基质辅助激光解吸电离-傅里叶变换离子回旋共振质谱仪对磷脂类分子在小鼠肝组织中的分布进行了研究,建立了质谱成像技术检测小鼠肝组织中磷脂类分子分布的分析方法.以7 g/Lα腈基-4-羟基肉桂酸的50%甲醇溶液(含0.2%三氟乙酸)作为基质,采用正离子采集模式,准确鉴定了5类13种磷脂类分子,其分子量主要分布在700～9...     

茶叶中多元素的微波消解等离子体发射光谱法测定

采用密闭式微波消解系统处理茶叶样品,以电感耦合等离子体发射光谱法测定茶叶样品中铜、铁、锌、锰、钡和铝6种元素.分别从消解液的选择、用酸量及样品消解量等方面进行消解条件的优化,对测定钡、铝元素存在的干扰进行了讨论.各元素的检出限范围为0.15～0.65μg·g-1,回收率为98.6%～106%,精密度为0.8%～5.3%...     

快速溶剂萃取-气相色谱/质谱联用测定塑料桌布中的邻苯二甲酸酯

采用快速溶剂萃取-气相色谱/质谱联用法(ASE-GC/MS)和超声波萃取-气相色谱/质谱联用法(USE-GC/MS)测定了塑料桌布中的邻苯二甲酸酯.结果表明:ASE-GC/MS的测量精度优于USE-GC/MS,后者测量值大约为前者的五分之四;ASE-GC/MS的回收率为89.0%～95.5%,相对标准偏差为4.3%～1...     

微波消解/干灰化-分光光度法测定面制食品中的铝

采用微波消解法和干灰化法对面制品进行前处理,用分光光度法测定面制品中的铝含量,建立了微波消解/干灰化-分光光度法测定铝的方法.实验结果表明,本方法前处理简单,检测结果准确度高,精密度好,在0～10μg/25 mL线性范围内:相关系数r=0.999 5,方法检出限为0.2 μg/25 mL,样品的加标回收率在92.0 %...     

微波消解-毛细管电泳法测定茶叶中的生物碱

应用微波消解-毛细管电泳法测定3种茶叶中的咖啡因、腺嘌呤及儿茶素类化合物.优化了缓冲溶液体系、浓度、pH及分离电压等实验条件.在最佳实验条件下,以30 mmol/L硼砂-10 mmol/L β-环糊精为缓冲溶液,pH为9.0,分离电压为22 kV,检测波长为280 nm,电动进样20 kV×5s时,在7 min内同时分...     

氨基甲酸酯型猪去氧胆酸分子钳的微波合成及其对卤素阴离子的识别

在微波辐射条件下,以猪去氧胆酸为隔离基,芳香胺为手臂,通过三光气桥连,合成了五个新型猪去氧胆酸分子钳(4a～4e),其结构经1H NMR,IR,MS和元素分析表征.紫外光谱滴定法的研究结果表明,4对卤素阴离子均具有良好的识别能力,选择顺序依次为I-＞ Br-＞ Cl-;主客体之间形成1∶1型超分子配合物,识别作用的主要...     

聚乙二醇对哈维氏弧菌疫苗免疫效果的影响

以聚乙二醇( PEG)作为超声介质及疫苗载体,用超声波瞬间高温、高压及剪切力作为灭活方式,将哈维氏弧菌制成PEG结合疫苗,该疫苗与传统疫苗分别经腹腔注射免疫接种锦鲤成鱼,检测了锦鲤血细胞吞噬百分率、吞噬指数、抗菌活力、抗体效价及免疫保护力等指标,评价疫苗效果.结果表明,PEG6000作为载体制备的疫苗,其各指标统计比较...