Fast and efficient immunoaffinity column cleanup and liquid chromatography–tandem mass spectrometry method for the quantitative analysis of aflatoxins in baby food and feeds

An ultra high performance liquid chromatography‐tandem mass spectrometric method has been developed for the highly sensitive and selective determination of regulated aflatoxins. The extraction of aflatoxins from baby food matrices were performed using liquid–liquid extraction procedure followed by immunoaffinity column cleanup. The higher sensitivity for the determination of target aflatoxins was fulfilled by applying a preconcentration step with immunoaffinity columns after acetonitrile–water extraction. The enhanced selectivity was attained with the triple quadrupole mass analyzer operated in electrospray positive ionization mode. Method validation was tested in five different baby food matrices by recovery experiments. Satisfactory recoveries, between 92 and 103%, with relative standard deviations lower than 8% were achieved in all the tested matrices. The proposed method was found to be specific as no interference peaks were observed for blank samples. The limit of detection of the method was found to be in the range of 0.003–0.008 ng/mL. The validated method was fruitfully applied to the screening of aflatoxins in baby foods and feeds sample retailed in local markets of Riyadh, Saudi Arabia. The obtained levels of all analyzed aflatoxins were below the regulation limits set by European Agency.     

Determination of carbapenems in water samples by UHPLC–MS/MS

A rapid and reliable method for the detection of five carbapenems (biapenem, imipenem, doripenem, meropenem, and faropenem) in water was developed and validated. After acidification of water samples with acetic acid, carbapenems were isolated using a Bond Elut PPL cartridge. The target compounds were separated using ultra high performance liquid chromatography with a chromatographic run time of 5 min and detected on a triple quadrupole mass spectrometer operated in positive electrospray ionization and multiple reaction monitoring mode. Mean recoveries were in the range of 76.6–106.5%, with satisfactory intraday and interday relative standard deviations lower than 10.0 and 10.8%, respectively. The limits of detection and quantification were in the ranges of 0.05–0.2 µg/L and 0.1–0.5 µg/L, respectively, depending on the analyte. The proposed method was applied to the analysis of river samples and wastewater samples from swine farms, and no carbapenems were detected in the collected samples.     

超宽带信道下MBOK调制系统可达速率分析

该文从信息论角度分析了超宽带信道下MBOK(M-ary bi-orthogonal keying)调制系统(包括均衡、编码)的性能,以提供超宽带调制系统设计的理论分析工具.该系统采用频域均衡以获得分集增益,且均衡的残余干扰在MBOK解扩后也得以降低.基于最小均方误差(MMSE)频域均衡,并将MBOK解扩后的残余跨符号干...     

参变过程中的群速延迟对晶体匹配长度的影响

基于能量守恒和三波耦合波方程,建立了超短脉冲在参变过程中二次谐波产生时的I类和II类相位匹配条件、基波与谐波之间的群速延迟时间、以及群速失配对晶体长度限制的理论基础。以负单轴非线性光学晶体CsLiB6O10为例,分析和数值计算了超短脉冲宽度为100fs时,谐波的群速匹配长度随基波波长变化的规律。研究结果表明在I类相位匹配条件下,基波波长为642nm时,群速延迟最小,相应的群速匹配晶体长度最长为19.1mm;在II类相位匹配条件下,基波波长为767nm,群速延迟最小,群速匹配长度最长为0.89mm。     

柱前衍生-超高效液相色谱法测定3种奶粉中18种氨基酸

近年来羊奶粉和骆驼奶粉备受消费者青睐,它们具有潜在的低致敏性,因此成为牛乳不耐受人群尤其是婴幼儿的母乳替代品,其营养价值备受关注.牛奶粉、羊奶粉和骆驼奶粉中氨基酸含量的比较研究鲜有报道.利用酸水解得到游离氨基酸,选择6-氨基喹啉-N-羟基琥珀酰亚胺氨基甲酸酯(AQC)进行柱前衍生,超高效液相色谱分离并检测,外标法定量....     

原子力显微镜在癌细胞观察和研究中的应用

原子力显微镜(AFM),能够在接近生理条件下以具有原子级的分辨率对活细胞进行表面成像和超微结构观察,同时可以研究细胞的生物过程、细胞与药物之间和细胞之间的相互作用,成为细胞生物学研究的一种有效工具.近年来AFM在细胞生物学研究中的应用进展很快,许多研究成果在生物医学和临床医学方面有良好的应用前景.本文分析了原子力显微镜的成像机理、工作模式和技术要点,综述了原子力显微镜在癌细胞的研究应用现状和前景.     

一种新型温度自补偿高灵敏度折射率计

基于高频CO2激光脉冲写入的新型超长周期光纤光栅(ULPFG),提出了一种可实现温度自补偿的新型高灵敏度折射率计。理论与实验表明,新型超长周期光纤光栅不同闪耀阶次谐振峰对外界折射率与温度变化的灵敏度各自不同,特别的是,该光栅存在对外界折变不敏感的谐振峰,测量中除了可以利用该峰实现温度同时测量外,还可以补偿另一个测量折变的谐振峰因温度变化带来的测量误差。该折射率计具有制作简单、成本低、强度好,灵敏度高等优点,当外界折射率在1.43~1.45范围内变化时,其折射率测量灵敏度可达每单位折射率240 nm,在实际工业应用中具有较大的潜在实用价值。     

超高效液相色谱法检测化妆品中的12种磺胺抗生素

建立了采用超高效液相色谱(UPLC)-二极管阵列检测器（PDA）测定化妆品中12种常见的磺胺抗生素(磺胺、磺胺间甲氧嘧啶、磺胺醋酰、磺胺甲基异唑、磺胺嘧啶、磺胺二甲异唑、磺胺噻唑、磺胺二甲氧嘧啶、磺胺甲基嘧啶、磺胺喹啉、磺胺二甲嘧啶、磺胺硝苯)的方法。采用Acquity UPLCTM BEHC C18 色谱柱(50 mm×2.1 mm, 1.7 μm),流动相为乙腈/0.1%的甲酸水溶液,梯度洗脱。样品经提取、反萃取后,用UPLC-PDA进行分析检测,结合保留时间和紫外光谱进行定性分析,定量检测波长268 nm。12种磺胺的检出限(S/N=3)均为1 μg/g,定量下限(S/N=10)为2～3 μg/g,在1～25 mg/L(磺胺硝苯为0.5～12.5 mg/L)范围内,峰面积和质量浓度的线性关系良好(r>0.9997)。添加水平为40, 8 μg(磺胺硝苯为20, 4 μg)时,12种磺胺的平均回收率分别为86.8%～98.1%和80.1%～96.9%,相对标准偏差小于10%(n=6)。结果表明该方法简单,分离效果好,速度快,能够满足检测化妆品中12种常见的磺胺抗生素的需要。     

超高效液相色谱-串联四极杆质谱联用分析鸭蛋黄中的苏丹红Ⅰ～Ⅳ

建立了鸭蛋黄中苏丹红Ⅰ～Ⅳ号的超高效液相色谱-串联四极杆质谱联用（UPLC-MS/MS）的分析方法。采用乙腈提取样品中的苏丹红,加水反沉淀除去蛋白质和脂肪等杂质,冷冻后高速离心,取上层清液供UPLC-MS/MS分析。经Waters Acquity BHE C18超高效液相色谱柱分离,串联四极杆质谱多反应监测模式检测,4种物质的检出限均为0.05 μg/L,实际样品中4种物质的检出限为10 μg/kg。采用标准添加法测定苏丹红的回收率,100.0,200.0,300.0 μg/kg 3个不同添加水平的回收率为50.2%～101.3%。实验结果表明该方法灵敏度高,检出限低,确证能力强,分析时间短,可满足高通量食品样品中苏丹红的日常检测。     

超高效液相色谱-静电场轨道阱高分辨质谱法测定硝苯地平中痕量基因毒性杂质

建立了测定硝苯地平中基因毒性杂质2、6和12的超高效液相色谱-静电场轨道阱高分辨质谱法(UHPLC-Orbitrap HRMS).样品以甲醇为溶剂,提取后直接进样分析.采用ACE EXCELTM 3 C18-AR色谱柱(150 mm×4.6 mm,3μm)分离,流动相为甲醇-0.1％甲酸水(65:35,v/v),等度洗...