QuEChERS净化-超高效液相色谱-串联质谱法测定凯特芒果中14种农药残留

建立QuEChERS净化-超高效液相色谱-串联质谱法同时测定凯特芒果中14种农药残留。取10.0 g样品经改进的QuEChERS方法进行前处理,采用ZORBAX SB-C_(18)色谱柱分离,以4 mmol/L甲酸水溶液和甲醇为流动相进行梯度洗脱;质谱采用电喷雾正离子源和多反应监测模式。14种农药的质量浓度为4.0～200.0μg/L时,线性关系良好,相关系数r0.999,定量限为0.15～1.0μg/kg,回收率为86.5%～103.1%,相对标准偏差为4.1%～11.5%。方法灵敏度及准确度良好,能满足凯特芒果中14种农药残留检测的要求。     

LC-MS/MS测定蔬菜中苯醚甲环唑残留的研究

使用高效液相色谱—串联质谱法测定蔬菜中苯醚甲环唑农药残留.样品前处理采用振荡、超声、均质3种方法提取,分别以QuEChERS净化柱、氨基净化柱、弗罗里硅净化柱、C18净化柱进行净化,使用高效液相色谱串联质谱仪(LC-MS/MS)测定,对比回收率,确定最优的提取、净化方法.试验结果表明,使用振荡提取、QuEChERS净化...     

QuEChERS结合高效液相色谱-串联质谱法测定禽蛋中的氯霉素药物残留

目的建立QuEChERS(Quick、Easy、Cheap、Effective、Rugged、Safe)结合高效液相色谱-串联质谱法(HPLC-MS/MS)测定禽蛋(鸡蛋、鸭蛋、鹌鹑蛋、鹅蛋)中的氯霉素药物残留的分析方法。方法 禽蛋样品经乙腈提取,经(PSA∶C18=1∶1)净化处理,采用高效液相色谱-串联质谱法测定,同位素内标法定量。结果 禽蛋基质中氯霉素在0.020～2.0μg/kg线性范围内,相关系数r>0.999;方法检出限0.020μg/kg,定量限0.050μg/kg;在添加浓度水平为0.020、0.10、0.50μg/kg时,回收率范围为80.8%～119.0%,相对标准偏差为4.09%～15.21%(n=6)。采用建立的方法对市购禽蛋样品和天然污染鸡蛋样品进行验证测试,方法实用性满足残留测试要求。结论 本方法前处理操作简便、灵敏度高、可有效用于禽蛋中氯霉素药物残留的监控与定量测定。     

QuEChERS结合质谱法测定食用菌中13种农药残留

本文目的在于建立QuEChERS前处理方法测定食用菌中13种农药残留量同时供气相色谱—串联质谱仪和液相色谱—串联质谱仪测定的分析方法。本实验采用冬菇、草菇和金针菇三种食用菌,分别以乙腈提取,改良的QuEChERS(Quick、Easy、Cheap、Effective、Rugged、Safe) 方法净化,气相色谱-串联质谱法采用Agilent HP-5MS ultralnert 柱 (30.0 m×250μm×0.25μm) 柱上分离,液相色谱-串联质谱法采用农残色谱柱ACQUITY UPLC? BEHC181.7um 2.1x50mm Column分离。结果表明,在添加水平< 0.1mg/kg 时,13种农药的回收率在 60% ～ 120% 之间,添加水平在 0.1～1mg/kg 时,13种农药的回收率在80% ～ 110% 之间。相关系数>0.99,符合农药残留国家标准要求。此方法适用但不限用于食用菌中13种农药残留测定。     

改进的QuEChERS-UPLCMSMS测定姜中32种氨基甲酸酯类农药

建立了一个基于QuEChERS技术的超高效液相色谱-串联质谱法同时检测姜中32种农药的方法。改进了传统的QuEChERS方法通过基质标定量校正基质效应的方式。通过优化仪器条件结合稀释的方法,实现溶剂标定量。试验结果表明, 32种农药除久效威定量限为30μg/kg,其他农药的定量限均在0.05～1.8μg/kg。丁酮威和久效威在50, 75和100μg/kg水平加标,其他农药在10, 20和50μg/kg水平加标,回收率范围为63.06%～109.65%, SRSD≤15%(n=6)。在0.5～100 ng/mL范围内,标准曲线相关系数>0.99。该方法便捷、快速、准确,可满足基层农药残留筛查的需求。     

GC-MS同时测定霍山石斛及霍山产铁皮石斛中拟除虫菊酯和氨基甲酸酯类16种农药残留的检测方法

建立了气相色谱-质谱(GC-MS)联用法同时测定霍山石斛及霍山产铁皮石斛中16种农药残留的分析方法。石斛样品经乙腈提取,减压浓缩后,采用SPE固相萃取法和QuEChERS法净化,GC-MS采用选择离子测试(SIM)模式进行检测。结果表明,16种农药在5.0～80.0μg/mL浓度范围内呈现良好的线性关系,使用SPE固相萃取法在500μg/L加标水平下各农药的加标回收率为84.87%～95.96%,相对标准偏差(RSD)为4.08%～7.66%,当使用QuEChERS法在500μg/L加标水平下各农药的加标回收率为94.90%～104.91%,相对标准偏差(RSD)为2.23%～4.67%,且QuEChERS法加样回收率和相对标准偏差略优于SPE固相萃取法。16种农药残留定量限为0.0003～0.2331μg/mL,精密度(RSD)为1.02%～2.58%,稳定性(RSD)为1.82%～2.97%。该方法快速、灵敏、准确,可应用于霍山石斛及霍山产铁皮石斛中多种农药残留的测定。     

QuEChERS-高效液相色谱-串联质谱法测定牛奶中氨基甲酸酯类农药残留量

目的建立高效液相色谱-串联质谱法(high performance liquid chromatography-tandem mass spectrometry,HPLC-MS/MS)测定牛奶中5种氨基甲酸酯类农药的方法。方法样品经乙腈提取、氮吹浓缩、QuEChERS净化,高效液相色谱-串联质谱法测定,采用外标法定量。结果5种氨基甲酸酯类农药在2.00-200μg/kg范围内线性关系良好(r>0.999);方法检出限为0.50~3.00μg/kg,定量限为1.50~10.00μg/kg;加标水平为0.010~0.050 mg/kg时,回收率为83.6%-108%,相对标准偏差为1.6%~15.6%。结论该方法简便快捷、灵敏度高,适用于牛奶中氨基甲酸酯类农药的检测。     

QuEChERS-高效液相色谱-串联质谱法测定鸡蛋中38种药物残留

目的建立高效液相色谱-串联质谱法(high performance liquid chromatography-tandem mass spectrometry, HPLC-MS/MS)测定鸡蛋中38种药物残留的分析方法。方法样品采用0.1 mol/L乙二胺四乙酸二钠(ethylene-diamine-tetra-acetate,EDTA)和乙腈提取,经QuEChERS净化后,通过LC-MS/MS测定,外标法定量。结果鸡蛋中38种药物在0.3～100μg/kg浓度范围内相关系数(r~2)在0.99138～0.99989之间,线性关系良好。方法检出限0.05～1.0μg/kg,定量限0.1～3.0μg/kg,在3.0、10.0、50.0μg/kg 3个添加水平的平均回收率72.49%～114.06%,相对标准偏差(n=6)2.37%～13.85%。结论本方法操作简便快速、灵敏稳定,适用于鸡蛋中多种药物残留的高通量快速检测。     

QuEChERS结合高效液相色谱串联质谱法测定畜禽肉中工业松香残留

采用QuEChERS(Quick, Easy, Cheap, Effective, Rugged and Safe)结合高效液相色谱串联质谱法建立一种快速检测畜禽肉中工业松香残留的方法。样品中的松香酸和脱氢松香酸2种工业松香残留标志物用乙腈提取,经含PSA、C18、硫酸镁的QuEChERS净化包净化,采用高效液相色谱串联质谱仪进行检测。在0～200 ng/mL浓度范围内,线性关系良好,松香酸和脱氢松香酸的相关系数(R)均达到0.999以上,检出限分别为1.8、4.5μg/kg,定量限分别为3.2、10.6μg/kg,回收率为85.1%～92.1%,相对标准偏差为6.6%～9.7%。模拟工业松香和松香甘油酯脱毛,畜禽肉的表皮和肌肉组织中均有一定量的松香酸和脱氢松香酸检出。变质畜禽表皮组织中由于产生有机胺类物质,使得松香酸和脱氢松香酸回收率降低。试验方法操作简单、灵敏度高,能够快速处理样品,可用于实际样品中工业松香残留标志物的检测分析。     

QuEChERS-液相色谱-串联质谱法测定葵花籽中30种农药残留

目的建立QuECHERS-液相色谱-串联质谱法测定葵花籽中30种农药残留的分析方法。方法葵花籽用1%乙酸-乙腈溶液提取,QuEChERS试剂净化,液相色谱-串联质谱法(liquid chromatography-tandem mass spectrometry,LC-MS/MS)测定,多反应监测模式(multiple reaction monitoring,MRM)分析,外标法定量。结果 30种农药分为2组,第1组23种农药在10~100μg/L范围内,第2组7种农药在1~10μg/L范围内,这2组的峰面积与对应的质量浓度间都呈良好的线性关系,相关系数大于0.9970。各组在3个添加水平的平均回收率为70%~120%(第1组10、20和100μg/kg,第2组1.0、2.0和10μg/kg各3个添加水平),相对标准偏差1.50%~9.57%(n=6),定量限0.01~0.20μg/kg。结论该方法操作灵敏、准确、可靠,能满足葵花籽中多种农药残留量的检测。     

Arsenic content of some edible mushroom species

The arsenic contents of 162 fruit body samples of 37 common edible mushroom taxa were analyzed. The samples were gathered from different habitats of Hungary (mainly from mountains) between 1984 and 1999. The arsenic content of the samples was measured by the inductively coupled plasma spectrometry method. Very low [lower than 0.05 mg/kg dry matter (DM)] concentrations were found in the samples of 13 taxa, while higher (or very high) contents were quantified in other common taxa (the highest arsenic content was recorded in the fruit body of Laccaria amethysthea at 146.9 mg/kg DM). The species of eight genera (Agaricus, Calvatia, Collybia, Laccaria, Langermannia, Lepista, Lycoperdon, Macrolepiota) belong to the so-called accumulating taxa, and this tendency is evident on all habitats. This arsenic accumulation capability is found in two orders of Basidiomycetes (Agaricales and Gasteromycetales), which is to say this phenomenon occurs in the families Agaricaceae, Tricholomataceae and Gasteromycetaceae. The accumulating taxa found all have a saprotrophic type of nutrition; arsenic accumulation is not detectable in xilophagous or in mycorrhizal species. The consumption of the accumulating species found has only a low toxicological risk for three reasons: the consumed fresh fruit bodies contain about a tenfold lower arsenic level than the dried ones, the majority of arsenic occurs not in poisonous inorganic, but in less dangerous (or not poisonous) organic forms, and the frequency of consumption is low.     

Organization and localization of the dnaA and dnaK gene regions on the multichromosomal genome of Burkholderia multivorans ATCC 17616

The Burkholderia multivorans strain ATCC 17616 carries three circular chromosomes with sizes of 3.4, 2.5, and 0.9 Mb. To reveal the distribution and organization of the genes for fundamental cell functions on the genome of this bacterium, the dnaA and dnaK gene regions of ATCC 17616 were cloned and characterized. The gene organization of the dnaA region was rnpA-rmpH-dnaA-dnaN-gyrB with a single consensus DnaA-binding box (TTATCCACA) between the rmpH and dnaA genes. This intergenic region, however, did not work as an autonomously replicating sequence in ATCC 17616. On the other hand, the gene organization of the dnaK region was grpE-orf1 (gene for thioredoxin homologue)-dnaK-dnaJ-pabB (gene for p-aminobenzoate synthetase component homologue). A putative heat-shock promoter that showed good homology to the sigma32-dependent promoter consensus sequence in Escherichia coli was found upstream of the grpE gene, suggesting that these five genes constitute an operon. In M9 succinate minimal medium the dnaJ mutant grew more slowly than the wild-type strain, indicating that this operon is functional. Pulsed-field gel electrophoresis and Southern blot analyses indicated that both the dnaA and dnaK gene regions exist as single copies on the 3.4 Mb chromosome.     

Microbial profiles of frozen trimmings and silver sides prepared at Indian buffalo meat packing plants

To assess microbiological quality of buffalo meat trimmings (TT = 114) and silver sides (SS = 41), samples were collected from four different Indian meat packing plants. The aim of this study was: (i) to evaluate standard plate count (SPC), psychrotrophic count (PTC), Enterococcus feacalis count (EFC), Staphylococcus aureus count (SAC) and Escherichia coli count (ECC) and the presence of Salmonella spp. and Listeria monocytogenes; and (ii) also to determine vero toxic E. coli (VTEC) by polymerase chain reaction (PCR). TT samples had significantly higher (P < 0.001) SPC, PTC, EFC, and SAC than SS, while across the meat types there was no difference (P > 0.05) in ECC. E. coli was recovered from 32.4% TT and 19.5% SS samples. The prevalence rate of Salmonella spp. and L. monocytogenes in TT was 1.75% and 0.87%, respectively. But no SS sample was found to be positive for any of these two pathogens. VTEC was found in 2.58% of all the tested samples. This finding suggests that TT contain higher microbes but only small numbers of pathogens of latent zoonotic importance. The present study confirmed the importance of maintaining good process hygiene at meat plants for microbiological status of buffalo meat.     

Susceptibility of stored product insects to high concentrations of ozone at different exposure intervals

Ozone is a highly reactive gas with insecticidal activity. Past studies have indicated that ozone technology has potential as a management tool to control insect pests in bulk grain storage facilities. The objective of this study was to determine the efficacy of short periods of exposure to high ozone concentrations to kill all life stages of red flour beetle (Tribolium castaneum (Herbst)) (Coleoptera: Tenebrionidae), and Indianmeal moth (Plodia interpunctella (Hübner)) (Lepidoptera: Pyralidae), adult maize weevil (Sitophilus zeamais (Motsch.)) (Coleoptera: Curculionidae) and adult rice weevil (S. oryzae (L)) (Coleoptera: Curculionidae). Insects were treated with six ozone concentrations between 50 and 1800 ppm. The specific objective was to determine minimal time needed to attain 100% mortality. The most ozone-tolerant stages of T. castaneum were pupae and eggs, which required a treatment of 180 min at 1800 ppm ozone to reach 100% mortality. Eggs of P. interpunctella also required 180 min at 1800 ppm ozone to reach 100% mortality. Ozone treatments of 1800 ppm for 120 min and 1800 ppm for 60 min were required to kill all adult S. zeamais and adult S. oryzae, respectively. The results indicate that high ozone concentrations reduce the treatment times significantly over previously described results. Our results also provide new baseline information about insect tolerance to ozone treatment.     

Contamination with storage fungi of human food from Cameroon

In a mycological study, a total of 95 human food samples were investigated to evaluate the incidence of fungal contamination in Cameroon by conventional identification method and partly confirmed by DNA sequencing. The isolated fungal spp. were further studied to determine their toxigenic potentials. The investigation revealed the predominance of Aspergillus and Penicillium with 96% of samples contaminated with at least one species of these fungi, whereas the incidence of co-contamination of samples was 85%. Aspergillus flavus and Aspergillus parasiticus (Flavi section) were the most predominant species contaminating mainly maize and peanuts. In addition, P. crustosum and P. polonicum were the most common contaminants belonging to the genus Penicillium. On the other hand, A. ochraceus (Circumdati section) registered a low incidence rate of 5%, including other members of the Aspergillus group. Other members of the genera Rhizopus and Alternaria spp. were also registered in the study. A majority of fungal strains of A. ochraceus, A. parasiticus, P. crustosum and P. polonicum isolated were toxigenic, producing the mycotoxins tested for, while none was detected in cultures of A. fumigatus. The high incidence rate of fungi contamination coupled with their potentials in producing mycotoxins gives a strong indication that the samples tested may likely be contaminated with various mycotoxins. There is need for further study to assess the incidence of mycotoxins contamination in similar food samples.     

Effect of Zataria multiflora Boiss. essential oil and nisin on Salmonella typhimurium and Staphylococcus aureus in a food model system and on the bacterial cell membranes

The effects of different concentrations of Zataria multiflora Boiss. essential oil (EO: 0, 5, 15 and 30 μl 100 ml⁻¹) and nisin (N: 0, 0.25 and 0.5 μg ml⁻¹), temperatures (T: 25 and 8 °C), and storage times (up to 21 days) on growth of Salmonella typhimurium and Staphylococcus aureus in a commercial barley soup were evaluated in a factorial design study. The growth of S. typhimurium was significantly (P < 0.05) decreased by EO concentrations and their combinations with N concentrations at 8 °C. For S. aureus, the viable count was significantly (P < 0.05) inhibited by EO and N concentrations and their combinations, incubated at both storage temperatures. The mechanism of the antimicrobial action of EO, N, and their combinations against cell membranes of the tested organisms were also studied by measurement of the release of cell constituents and by the electronic microscopy observations of the cells. The significant increase of the cell constituents’ release of both organisms was observed as a result of treatments with EO and EO in combination with N. Electronic microscopy observations revealed that the cell membranes of S. typhimurium treated by EO and EO in combination with N were significantly damaged, while cells treated with only N looked similar to untreated cells. The electron micrographs of treated cells of S. aureus with EO, N, and their combination also showed important morphological damages and disrupted membranes.     

Cloning and expression analysis of two catalase genes from Aspergillus oryzae

Fungi contain distinct genes encoding the same class of enzyme that are differentially regulated according to conditions. We cloned two catalase genes, catA and catB, from Aspergillus oryzae. The catA gene predicts a 747-amino-acid polypeptide sharing 81% identity with Aspergillus fumigatus catalase (catA) and 77% with Aspergillus nidulans catalase (catA). The catB gene predicts a 725-amino-acid polypeptide sharing 82% identity with A. fumigatus catalase (catB) and 75% with A. nidulans catalase (catB). However, the catA and catB genes share little homology (41%) with one another, suggesting that each gene belongs to a distinct gene family. Overexpression studies demonstrated that both genes encode a functional catalase. Promoter assays indicated that the catA gene is developmentally regulated as it was preferentially expressed in solid-state cultures undergoing sporulation. However, its expression was not affected by hydrogen peroxide treatment. Conversely, the catB gene was highly expressed under all culture conditions tested, and it was induced by hydrogen peroxide treatment. These results suggest that the catB gene may be mainly used for detoxification of oxidative stress while the catA gene may have another role such as chaperoning proteins in the spore.     

Formation of cereulide and enterotoxins by Bacillus cereus in fermented African locust beans

Afitin, iru and sonru are three spontaneously fermented African locust bean Benin condiments. The fermentation processes are exothermic, with temperatures mostly being above 40 °C. A total of 19 predominant Bacillus cereus isolates from afitin, iru and sonru, were investigated. The enterotoxin genes nhe (A, B, C) were present in all 19 isolates, the hbl (A, C, D) in one (afitin), and the cytK gene in three isolates (afitin). Levels of cytotoxicity to Vero cells and NheA production in BHI-broth was within the range of known diarrheal outbreak strains. Autoclaved cooked African locust beans inoculated with emetic (cereulide producing) B. cereus Ba18H2/RIF supported growth at 25, 30 and 40 °C with highly different maximum cereulide productions of 6 ± 5, 97 ± 3 and 0.04 ± 0.02 μg/g beans, respectively (48 h). For non-autoclaved cooked beans inoculated with 2, 4 and 6 log₁₀B. cereus Ba18H2/RIF spores/g beans, cereulide production was 5 ± 4, 64 ± 8 and 69 ± 34 μg/g beans, respectively at 24 h, while it was 70 ± 43, 92 ± 53 and 99 ± 31 μg/g at 48 h of fermentation at 30 °C. Even though high toxin levels were observed, to date there are no known reports on diarrhea or vomiting due to the consumption or afitin, iru and sonru in Benin, which also according to the present study is likely to be expected from the low levels of cereulide produced at 40 °C.