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排序方式: 共有110条查询结果,搜索用时 31 毫秒
101.
102.
Li F Zhao S Chin L Li Y Wu D Zhao X Han C Zhang H Ji R 《Journal of AOAC International》2007,90(1):167-172
The use of solid-phase filtration column (MycoSep 228) and liquid chromatography for determination of patulin in apple and hawthorn beverages was investigated. The method passed a series of validation tests, including separation efficiency, sensitivity, repeatability, validation within a collaborative trial, recoveries, and applicability. Accuracy and precision were very good for determination of patulin in both spiked and naturally contaminated apple/hawthorn beverage samples at levels of 10 microg/L and above, with limits of detection and quantification at 8 and 23 [microg/L, respectively. The applicability of the method was tested by analyzing commercially available domestic apple and hawthorn beverages. Patulin was found in 3 of 52 (5.77%) apple beverages at concentrations ranging from 63.45 to 88.44 [microg/L, and in 6 of 43 (13.95%) hawthorn beverages ranging from 19.8 to 206.88 microg/L. Among these were 3 apple and 4 hawthorn beverage samples with toxin levels that exceeded the Chinese legislative requirement of 50 microg/L in apple- and hawthorn-based products intended for human consumption. Comparable tests revealed that the results obtained by both the new MycoSep-based method and the official AOAC method are not significantly different (t value = 0.003268 < to.05, P > 0.05). 相似文献
103.
104.
基于96孔固相萃取-超高效液相色谱-串联质谱法,建立了人尿中2种苯氧乙酸除草剂、2种有机磷农药代谢物和4种拟除虫菊酯农药代谢物的测定方法。通过对液相色谱条件、质谱条件和样品前处理过程的系统优化,实现了在16 min内对8种目标分析物的分析测定。具体方法:1 mL尿液经β-葡萄糖醛酸酶酶解过夜,Oasis HLB 96孔固相萃取进行目标分析物的提取净化,甲醇洗脱;以0.1%(体积分数)乙酸乙腈和0.1%(体积分数)乙酸水作为流动相,Acquity BEH C_(18)作为分析柱进行色谱分离;负离子电喷雾(ESI-)多反应监测(MRM)模式下检测目标化合物,同位素内标法定量。2,4-二氯苯氧乙酸(2,4-D)、2,4,5-三氯苯氧乙酸(2,4,5-T)2种苯氧乙酸除草剂和3-苯氧基苯甲酸(3-PBA)、4-氟-3-苯氧基苯甲酸(4F-3PBA)、反式二氯乙烯基二甲基环丙烷羧酸(trans-DCCA)3种拟除虫菊酯农药代谢物在0.1~100μg/L内、对硝基苯酚(PNP)、3,5,6-三氯-2-吡啶酚(TCPY)2种有机磷农药代谢物、顺式二氯乙烯基二甲基环丙烷羧酸(cis-DCCA)1种拟除虫菊酯代谢物在0.2~100μg/L内线性关系良好,相关系数均大于0.9993;方法检出限为0.02~0.07μg/L,方法定量限为0.08~0.2μg/L;低、中、高3个水平下的加标回收率为91.1%~110.5%,日内精密度为2.9%~7.8%,日间精密度为6.2%~10%。应用该方法测定了214份尿液样本。结果显示除2,4,5-T外,其余7种目标分析物均有检出。TCPY、PNP、3-PBA、4F-3PBA、trans-DCCA、cis-DCCA、2,4-D的检出率为2.8%~99.1%。检出浓度(中位值)由高到低分别是2.0μg/L(TCPY)、1.8μg/L(PNP)、0.99μg/L(trans-DCCA)、0.81μg/L(3-PBA)、0.44μg/L(cis-DCCA)、0.35μg/L(2,4-D)和未检出(4F-3PBA)。该方法操作简便,定量准确,灵敏度高,每批次可完成96个样品测定,适用于人尿中多种农药及农药代谢物的批量分析测定。 相似文献
105.
《中国化学快报》2023,34(11):108322
On-tissue chemical derivatization (OTCD) effectively enhances ionization efficiency of low abundant and poorly ionized functional molecules to improve detection sensitivity and coverage of mass spectrometry imaging (MSI). Combination OTCD and MSI provides a novel strategy for visualizing previously undisclosed metabolic heterogeneity in tumor. Herein, we present a method to visualize heterogeneous metabolism of oxylipins within tumor by coupling OTCD with airflow-assisted desorption electrospray ionization (AFADESI)-MSI. Taking Girard's P as a derivatization reagent, easily ionized hydrazide and quaternary amine groups were introduced into the structure of carbonyl metabolites via condensation reaction. Oxylipins, including 127 fatty aldehydes (FALs) and 71 oxo fatty acids (FAs), were detected and imaged in esophageal cancer xenograft with AFADESI-MSI after OTCD. Then t-distributed stochastic neighbor embedding and random forest were exploited to precisely locate the distribution of oxylipins in heterogeneous tumor tissue. With this method, we surprisingly found almost all FALs and oxo FAs significantly accumulated in the core region of tumor, and exhibited a gradual increase trend in tumor over time. These results reveal spatiotemporal heterogeneity of oxylipins in tumor progression, highlighting the value of OTCD combined with MSI to gain deeper insights into understanding tumor metabolism. 相似文献
106.
Jingguang Li Feifei Guo Yuxin Wang Jiaying Liu Zongwei Cai Jialing Zhang Yunfeng Zhao Yongning Wu 《Journal of chromatography. A》2012
Perfluorinated compounds (PFCs) are ubiquitous in the environment and are becoming a public health concern. It is desirable to develop sensitive and accurate methods to measure PFCs in non-invasive matrices such as hair and nail for biomonitoring of body burden. Different extraction methods coupled with solid phase extraction were investigated for extraction efficiency. The extracts were separated, identified and quantified by liquid chromatography-tandem mass spectrometry. Extraction with acetonitrile proved to be the most efficient extraction method for human hair sample, while extraction by methanol with alkaline digestion performed best for human nail sample. The matrix recoveries of the optimized methods ranged from 78% to 116% for hair and from 87% to 126% for nail sample. The ranges of the limit of detection (LOD) were 0.026–0.069 ng/g and 0.023–0.094 ng/g for hair and nail, respectively. These methods were validated by evaluating LOD, accuracy and precision and were proven to be useful for measuring paired human hair and nail samples collected from the general population. 相似文献
107.
《Chaos, solitons, and fractals》2000,11(13):2001-2016
Equipotential effect of gravity (EEG), as opposed to radial interactions between bodies, is introduced here as the impact of a tangential potential. EEG causes frequency decrease that was observed in two specially devised and several indirect experiments. It depends on the distance that is measured along equipotential parts of trajectories and can explain an extraneous frequency decrease found in radio signals emitted by navigational positioning systems. It retrodicts the observed differential rotation of the sun without the assumed drag of the sun's photosphere as its cause, and predicts apparent anomalous rotation of the sun, for from the shifts in spectra taken from the sun's limb it should appear as if the sun rotates away faster than it does towards an observer on earth. The value predicted by it is over 10.56% excess over Einstein's value of deflection of light near the sun and agrees with the 10–15% excess estimated from the data that was obtained in numerous, quite independent experiments. 相似文献
108.
109.
Bremsstrahlung in intermediate-energy nucleon reactions within an effective one-boson exchange model
《Nuclear Physics A》1998,628(2):255-274
Within a covariant effective one-boson exchange model for the T matrix of NN interactions we present detailed calculations of bremsstrahlung cross sections for proton-proton and proton-neutron reactions at beam energies in the 1 GeV region. Besides pure bremsstrahlung processes we consider photons from Λ decays and contributions from the η → γγ process. At beam energies above 700 MeV the Λ decay channel dominates the spectra at large photon energies, where the interference between non-resonance processes and the Λ decay channel becomes also important. Low energy photons stem from pure bremsstrahlung processes. The available experimental data at 730 MeV beam energy is well described. We extrapolate the model down to 280 MeV, where more detailed experimental data exist, and find agreement with angular distributions. 相似文献
110.
Xiaoxiao Wang Xinran Hao Jie Yan Ji Xu Dandan Hu Fenfen Ji Ting Zeng Fuyue Wang Bolun Wang Jiacheng Fang Jing Ji Hemi Luan Yanjun Hong Yanhao Zhang Jinyao Chen Min Li Zhu Yang Doudou Zhang Wenlan Liu Xiaodong Cai Zongwei Cai 《中国化学快报》2023,34(10):108230-113
Parkinson’s disease(PD) is a complex neurological disorder that typically worsens with age. A wide range of pathologies makes PD a very heterogeneous condition, and there are currently no reliable diagnostic tests for this disease. The application of metabolomics to the study of PD has the potential to identify disease biomarkers through the systematic evaluation of metabolites. In this study, urine metabolic profiles of 215 urine samples from 104 PD patients and 111 healthy individuals were ass... 相似文献