Enantioseparation and determination of dufulin enantiomers in cucumber and soil by chiral liquid chromatography–tandem mass spectrometry

A simple and rapid method for enantioselective determination of dufulin in cucumber and soil was developed by liquid chromatography with tandem mass spectrometry. The enantiomers were separated on a Superchiral S‐OD chiral cellulose tris(3,5‐dimethylphenylcarbamate) column at 20°C, with a mixture of acetonitrile and water (0.1% formic acid; 52:48, v/v) as mobile phase at a flow rate of 0.65 mL/min. The pretreatment conditions were optimized using an orthogonal test, and the optimized method showed good linearity and sensitivity. The limits of detection and limits of quantification of two dufulin enantiomers were 0.006 and 0.02 mg/kg, respectively. The average recoveries of S‐enantiomer and R‐enantiomer in cucumber and soil were 80.61–99.83% and 80.97–102.96%, respectively, with relative standard deviations of 1.30–9.72%. The method was successfully applied to determine dufulin in real cucumber and soil samples. The results demonstrate that the method could facilitate further research on the differences between individual dufulin enantiomers with respect to metabolites and environmental fate and finally help reveal the complex interactions that exist between dufulin, humans and the environment.     

基于高光谱图像的即食海参新鲜度无损检测

新鲜度是即食海参加工品质调控和贮藏品质监控的关键指标。针对感官评定和现有理化检测无法满足即食海参产品大批量、标准化、工业化生产问题,提出了一种基于高光谱图像的即食海参新鲜度快速无损检测方法,通过图像主成分分析和波段比运算相结合,优选特征波长和图像;依据海参腐败机理,建立图像纹理特征与即食海参新鲜度等级间的关联模型,实现即食海参新鲜度无损、快速评价。首先针对高光谱图像巨大的数据量展开降维研究。根据即食海参体壁光谱吸收特性,以具有明显化学吸收特征的波长(474和985 nm)为分界点,获得包括全检测波段(400～1 000 nm)在内的六个待处理波段,通过分段图像主成分分析实现待测波段的优选,利用权重系数和波段比图像运算,最终将686和985 nm波段比图像确定为特征图像。面向特征图像的感兴趣区域(ROI),构建灰度共生矩阵(gray-level co-occurrence matrix, GLCM)、灰度梯度共生矩阵(gray-gradient co-occurrence matrix, GGCM)、改进的局部二元模式纹理描述子(local binary pattern,LBP),分别提取纹理参数作为输入,以挥发性盐基氮(total volatile basic nitrogen, TVB-N)检测为标准,建立经粒子群优化的BP 神经网络(back propagation,BP)即食海参新鲜度判别模型,新鲜度等级判别准确率分别为90%,95%和80%。结果表明,即食海参高光谱图像灰度梯度共生矩阵的纹理特征用于新鲜度判别效果较好。为即食海参新鲜度快速无损检测方法研究和仪器开发提供了理论基础和数据支持。     

80%成标干悬浮剂在黄瓜中残留动态研究

利用高效液相色谱法研究了80%成标干悬浮剂在黄瓜中的消解动态和最终残留。结果表明,80%成标干悬浮剂在黄瓜中的半衰期为7.9d。按5760g/hm2施药,共施药4次,最后一次施药5d后取样检测,残留量为0.24mg/kg。远远低于其它国家规定的最大残留量限值。     

番茄和黄瓜贮藏保鲜技术研究

分别为保鲜剂贮藏、筐贮、减压贮藏、溶液贮藏、高温处理等方法贮藏番茄５０天后，除减压贮藏方法外，采用其它方法处理的均可使其好果率达８８％以上，商品率达９０％以上，并基本上保持了果实的品质和风味。应用保鲜剂贮藏、减压贮藏方法处理黄瓜，４５天后，好果率达９２％以上，果实品质良好，并且贮藏前后番茄和黄瓜的厉分也无大的变化。     

A new triterpene glycoside from sea cucumber Holothuria leucospilota

A new triterpene glycoside, leucospilotaside A, along with a known saponin, isolated from sea cucumber Holothuria leucospilota, and its structure was elucidated as 3β-O-[4-O-sodiumsulfate-β-D-quinovopyranosyl-(1→2)-β-D-xylopyranosyl]-holosta-22-ketone-9-en-17α,25α-diol (1) by extensive spectroscopic analysis and chemical methods. Leucospilotaside A (1) has a ketone carbonyl group (22) in the aglycon side chain.     

基于气相色谱-静电场轨道阱高分辨质谱的海参中风险物质的筛选北大核心CSCD

建立了一种基于改良QuEChERs的样品前处理新方法,并通过气相色谱-静电场轨道阱高分辨质谱(GC-Orbitrap HRMS)对海参样品中的有机氯农药类(OCPs)、多环芳烃类(PAHs)、酞酸酯类(PAEs)、多氯联苯类(PCBs)及其他农药类(ACs)等10大类289种具有健康风险的有机污染物进行了高通量高精准的定性鉴别和定量分析。通过将传统的QuEChERs方法与柱净化方法结合,提出了一种基于改良QuEChERs的简便生物样品制备新方法,经弗洛里硅土(Florisil)柱净化后脂含量降低了99.9%,显著减少了基质效应对分析结果的干扰,可在高分辨质谱(6万分辨率)全扫描模式下对289种目标化合物同时进行高精准定性筛查和定量分析。该方法定量限约0.56~57.8 pg/g,线性范围约6个数量级,回收率范围为40%~120%。由于Q Exactive GC-Orbitrap HRMS具备较高的质量分辨率和灵敏度,因此对目标化合物的定量限显著优于常规的色谱和质谱分析方法,常规方法无法检出的超痕量有机污染物利用该研究开发的方法可进行精准定量。基于此高覆盖度多目标分析方法对养殖场采集的海参样品进行分析,共从海参体内检出100种有机污染物,其中PAHs、ACs、PAEs、OCPs类检出总含量相对高于其他类污染物,总含量均值分别为157.8、153.2、64.4和46.4 ng/g dw。9-氯芴、5-氯苊、3-甲基胆蒽等多种新污染物首次在海参样品中检出,但含量都非常低。该方法简单高效,定量限低,线性范围宽,结果准确。此高覆盖度多目标分析方法可广泛应用于各种水产品中风险物质的广谱筛查和精准定量,为食品安全和绿色养殖提供技术支撑。     

Different transformation of carbosulfan to its higher toxic metabolites in pakchoi (Brassica campestris ssp.) and cucumber (Cucumissativus L.) after field application

Carbosulfan (CAS) is used as an insecticide on vegetables, but its toxicity might increase due to the formation of higher toxic metabolites including carbofuran (CAN), 3-hydroxycarbofuran (3-OH) and 3-ketocarbofuran (3-KETO). In this study, the transformation of CAS to its metabolites in pakchoi (Brassica campestris ssp.) and cucumber (Cucumissativus L.) was investigated in the field in Beijing and Changsha and in a greenhouse in Hangzhou. CAS was metabolised to CAN, 3-OH and 3-KETO in pakchoi but only to CAN and 3-OH in cucumber. In pakchoi, the degradation of CAS (as measured by the DT₅₀ value, the time marking the disappearance of 50% of the pesticide) was the fastest in Hangzhou (0.7 d), followed by Changsha (1.4 d) and Beijing (2.3 d), whereas in cucumber, its degradation was the fastest in Changsha (1.6 d) and Hangzhou (1.6 d), followed by Beijing (2.5 d). These results suggested the monitoring of metabolites should be a prior objective for CAS, and different metabolites should be considered when assessing the risk of CAS in different vegetables.     

渐降低温胁迫对黄瓜幼苗叶绿体膜相关指标的影响

为了进一步说明模拟自然界温度渐降低温胁迫的冷害作用的机理,以黄瓜品种“津优1号”为试材,以直降低温胁迫（昼温/夜温=（10±0.5）℃/（5±0.5）℃）为对照CK,常温（昼温/夜温=（25±0.5）℃/（18±0.5）℃）为对照CK₁,研究渐降低温胁迫（即以1 ℃·h^-1的平均降温速度进行降温处理）对黄瓜幼苗叶绿体膜相关指标的影响.结果表明：（1）Ca²⁺ATPase和Mg²⁺ ATPase活性在低温胁迫过程中呈先上升后下降趋势,随着低温胁迫的进程,渐降低温胁迫下2种酶活性下降的幅度明显低于直降低温胁迫.（2）经过低温胁迫,冷害指数、叶绿体膜蛋白质量浓度和叶绿素质量浓度显著下降.（3）处理T的冷害指数、膜蛋白和叶绿素质量浓度、Ca²⁺ ATPase和Mg²⁺ ATPase活性均显著高于CK.总之,渐降低温胁迫可以减少叶绿体膜的损伤,增强抵御低温逆境胁迫的能力.     

甲硫氨酸对黄瓜种子萌发、幼苗生长及离体子叶成花的影响

以黄瓜种子为材料,采用甲硫氨酸（Methionine,Met）浸种的方法,研究了不同浓度Met对黄瓜种子萌发、幼苗生长及离体子叶成花的影响．结果发现：（1）10^-4 M Met处理3h显著促进苗的生长而10^-5 M Met浸种处理则有利于子叶的生长;（2）10^-5 M Met浸种处理显著促进离体子叶成花;（3）离体子叶培养物的花芽分化力与子叶离体前的子叶／苗的鲜重比呈显著的正相关性（P〈0．01）;（4）添加10^-5 M DNA去甲基化试剂5-氮胞苷（5-Aza—cgtidine,5-Aza）能逆转10^-5 M Met处理对离体子叶培养物成花的促进作用．上述结果说明：10^-5 M Met浸种3h能显著促进子叶培养物的花芽（无论直接花还是间接花）形成,Met对离体子叶成花的诱导作用可能是作为甲基供体通过DNA甲基化途径来实现的．     

黄瓜子叶身与子叶柄的生理特性差异及其不同培养反应

与黄瓜子叶身相比,无论是子叶离体培养前还是离体培养后, 在苗龄 3d～ 9d其间,子叶柄始终具有较低的呼吸强度和较大的 A260nm物质渗漏 ,而且,两者间差异随苗龄而改变,这表明子叶柄和子叶身的细胞透性、呼吸活性存在显著差异,这些差异可能与子叶离体培养时只有子叶柄部位才能分化花芽有某种联系.