浊点萃取技术的应用

浊点萃取是近年发展起来的一种新兴的萃取技术。重点阐述了浊点萃取在环境样品、生物样品和食品工业分析中的应用,总结了浊点萃取技术的优点,指出了存在的问题,探讨了该技术的发展前景。     

高效液相色谱分析食品罐内涂料中双酚A和双酚F环氧衍生物残留

建立了高效液相色谱分析食品罐内涂料中双酚A(BPA)和双酚F(BPF)环氧衍生物的方法.样品经乙腈提取后,旋转蒸发浓缩至干,以V(乙腈)∶ V(水)=50∶ 50混合液溶解并定容;采用Lichrospher C18柱,以乙腈/水为流动相梯度洗脱,进行高效液相色谱分离;荧光检测器检测,激发波长230 nm,发射波长301 nm.在2.3～230 μg/L浓度范围内,各BPA和BPF环氧衍生物的响应峰面积与其相应浓度呈良好相关性,检出限为0.57～6.55 μg/L;在80～400 μg/L添加水平范围内,平均添加回收率为85%～107%;相对标准差小于7.4%.结果表明,本方法适用于食品罐内涂料中BPA和BPF环氧衍生物残留分析.     

北京市朝阳区食品污染物监测状况分析

为通过2008年北京市朝阳区食品污染物监测,了解辖区部分食品铅、镉、铝的污染现状,给食品风险评估和政府部门强化监管提供依据,按照国家标准方法GB／T5009对13种135件食品样品进行了铅、镉、铝含量的监测。结果表明,100件样品中铅超标率为6．O％,镉超标率为0;35件样品铝的超标率为65．71％。显示辖区经销的食品中重金属确有污染存在,而铝在油炸面制品和天然海蜇中超标率较高,仍对人体健康存在威胁。     

对食品中铝含量国标测定方法的改进

对国标GB/T 5009.182-2003中样品处理方法做了改进,用干法灰化代替湿法消解,解决了国标方法中由于pH值和高氯酸对显色反应的影响造成检测结果不准确的问题.采用干法灰化-分光光度法测定了食品中的铝含量,测定结果的相对标准偏差为1.6%(n=6),回收率为94.3%～100.7%.该方法适用于大批量食品中铝的快速检测.     

星际媒介H2NCH2CN与H2O反应中的H2O分子偶合质子转移机理和氢隧道效应

H2NCH2CN+H2O→H2NCH2C(OH)NH是一个重要的反应, 涉及到星际媒介中甘氨酸的形成, 与早期地球上的氨基酸起源有关. 如果没有考虑氢隧道效应, 在MP2/6-311+G(d,p)级别上计算反应能垒是254.7 kJ·mol-1, 在星际媒介中该气相反应很难进行. 在星际媒介冰颗粒表面上, 水分子催化反应增强了该化学反应的活性. H2NCH2CN与(H2O)3反应中的两个水分子作为催化剂降低活化能77.5 kJ·mol-1和活化自由能70.9 kJ·mol-1, 并且通过氢键桥协同传递质子. 量子氢隧道对于该反应进行至关紧要,采用小弯曲隧道(SCT)近似和正则变分过渡态理论(CVT)方法研究. 温度50 K时, 速率常数kSCT/CVT为1.86×10-23 cm3·molecule-1·s-1, 表明在星际媒介中通过质子隧道机理该反应容易进行. 研究结果与地球上的氨基酸起源于地球本身物质的观点相一致.     

纺织品与食品包装材料中烷基酚及双酚A迁移量的液相色谱-串联质谱分析

建立了纺织品与食品包装材料中烷基酚及双酚A迁移量的液相色谱-串联质谱分析方法.纺织品和食品包装材料浸泡液经Supelclean Envi-Carb石墨化碳黑固相萃取柱净化,以Waters XBridge C_(18)(150 mm×2.1 mm,3.5 μm)色谱柱分离后,进行LC-MS/MS多反应监测模式下的定性及定量分析.烷基酚和双酚A在纺织品模拟汗液、食品模拟物介质中特定迁移量的定量下限分别为2、4 μg/kg.在低、中、高3个添加水平下,测得纺织品样品的回收率为83%～91%,相对标准偏差为4.1%～9.0%;食品包装材料样品的回收率为82%～94%,相对标准偏差为3.9%～8.7%.     

Autonomously Propelled Motors for Value‐Added Product Synthesis and Purification

A proof‐of‐concept design for autonomous, self‐propelling motors towards value‐added product synthesis and separation is presented. The hybrid motor design consists of two distinct functional blocks. The first, a sodium borohydride (NaBH₄) granule, serves both as a reaction prerequisite for the reduction of vanillin and also as a localized solid‐state fuel in the reaction mixture. The second capping functional block consisting of a graphene–polymer composite serves as a hydrophobic matrix to attract the reaction product vanillyl alcohol (VA), resulting in facile separation of this edible value‐added product. These autonomously propelled motors were fabricated at a length scale down to 400 μm, and once introduced in the reaction environment showed rapid bubble‐propulsion followed by high‐purity separation of the reaction product (VA) by the virtue of the graphene–polymer cap acting as a mesoporous sponge. The concept has excellent potential towards the synthesis/isolation of industrially important compounds, affinity‐based product separation, pollutant remediation (such as heavy metal chelation/adsorption), as well as localized fuel‐gradients as an alternative to external fuel dependency.     

液相色谱串联质谱法(LC-MS/MS)分析宠物食品中三聚氰胺

三聚氰胺(melamine)为白色或无色结晶,通常用于塑料制品中合成树脂的生产中,高温和酸性条件下能引起三聚氰胺转移到食品中.三嗪类农药环丙氨嗪(cyromazine)在极端的pH条件下或者光降解的条件下也能生成三聚氰胺.     

气相色谱-质谱联用法检测保健品中的违禁药物

近年来,随着社会消费水平的不断提高,保健品市场日益兴旺,但暴露出来的问题也十分严重。假冒配方、虚假广告、任意夸大其功效作用的宣传已为社会与公众所关注,而添加违禁合成药物、假化学成分达到或增加其功效作用的行为更具隐蔽性、欺骗性和危害性,为一般消费者所难以识别。因     

Thermal behavior of glutamic acid and its sodium,lithium and ammonium salts

Glutamic acid (H2_glu) and its lithium, sodium and ammonium monosalts were submitted to thermal analysis using thermogravimetry (TG) and differential thermal analysis (DTA). The main goal of these studies was to compare the relative thermal stability and to evaluate the effect of the counter ion in the thermal decomposition pathways. Salts were obtained by direct neutralization of the purified acid with LiOH, NaOH or NH₄OH and were characterized by elemental analysis (C, H and N) and IR spectroscopy. Decomposition occurred after conversion to the pyroglutamic acid or the respective pyroglutamates and ammonium salt loosing NH₃ being converted to H₂glu before decomposition.