QuPPe-超高效液相色谱-串联质谱法测定蔬菜中呋虫胺及其代谢物残留

建立超高效液相色谱-串联质谱检测蔬菜中呋虫胺及其代谢物1-甲基-3-[（3-四氢呋喃）甲基]二氢胍盐（1-methyl-3-(tetrahydro-3-furylmethyl) guanidium?dihydrogen,DN）、1-甲基-3-[（3-四氢呋喃）甲基]脲（1-methyl-3-(tetrahydro-3-furylmethyl) urea,UF）残留的方法。蔬菜样品采用QuPPe分析方法处理后,经BEH-C18超高效液相色谱柱分离,采用电喷雾正离子模式,通过多反应监测方式测定,基质匹配标准曲线外标法定量。结果表明,呋虫胺及其代谢物在1.25～500?μg/L的质量浓度范围内线性关系良好,相关系数均大于0.991,方法检出限为0.04～0.66?μg/L,定量限为0.13～2.20?μg/L。在3?个添加水平条件下,呋虫胺及其代谢物DN、UF在黄瓜、番茄、马铃薯、甘蓝4?种基质中的添加回收率为72.0%～109.1%,相对标准偏差为1.4%～12.8%,最低添加量均为10?μg/kg。基质效应结果显示,呋虫胺及其代谢物大都表现为中等强度基质效应或强基质效应。该方法简单、准确、高效,可用于蔬菜样品中呋虫胺及其代谢物农药残留的快速筛查和定量检测。     

Detection of aflatoxin B1 by aptamer-based biosensor using PAMAM dendrimers as immobilization platform

We report an aptamer-based biosensor for detection of aflatoxin B₁ (AFB₁), a mycotoxin identified as contaminant in food. The sensor is assembled in a multilayer framework that utilizes cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) for acquiring the signal response by means of redox indicators: K[Fe(CN)₆]^−3/−4. Poly (amidoamine) dendrimers of fourth generation (PAMAM G4) immobilized on gold electrode covered by cystamine, were employed for attachment of single stranded amino-modified DNA aptamers specific to AFB₁. The cystamine-dendrimers (Cys-PAMAM) layers were compared with other immobilization platforms such as cystamine (Cys), 11-mercaptoundecanoic acid (MUA) and 11-mercaptoundecanoic acid-dendrimers (MUA-PAMAM), being the first approach the most appropriate for producing sensitive and reproducible signal in the range of concentrations 0.1–10 nM AFB₁. The sensor was validated in certified contaminated peanuts extract as well as in spiked samples of peanuts-corn snacks and the sensing response was evaluated and compared in terms of the matrix effect. The aptamer specificity was analyzed by testing the sensor in other mycotoxins such as aflatoxin B₂ (AFB₂) and ochratoxin A (OTA). The limit of detection achieved by this sensor was LOD = 0.40 ± 0.03 nM, it was regenerable in 0.2 M glycine-HCl and it did not lose its stability up to 60 h storing at 4 °C. Atomic Force Microscopy (AFM) studies were also performed for illustrating individual steps of biosensor assembly.     

Aflatoxin M1 in raw milk in Croatia

In this study the levels of aflatoxin M₁ (AFM₁) of 61 milk samples delivered from small milking farms were determined in January, February, March and April (winter–spring season), and June, July and September (summer–autumn season) of 2009. The AFM₁ concentration was determined by competitive enzyme-immunoassay method. The maximum mean concentrations of AFM₁ recorded in winter–spring season were in the range of 35.8–58.6 ng/l and in summer–autumn season in the range of 11.6–14.9 ng/l. The AFM₁ levels determined in January, February, March and April were significantly higher in accordance with concentration of AFM₁ in June, July and September (P < 0.05 to P < 0.0001, respectively). Also, there was significant difference (P < 0.0001) between the mean concentrations of AFM₁ in samples taken all together in winter–spring and summer–autumn season. Only in one sample delivered in February the level of AFM₁ was higher than the maximum tolerance limit (50 ng/l). Therefore, it was concluded that in 98.4% of milk samples in Croatia the levels of AFM₁ were below maximum tolerance level accepted by the European Union.     

Levels of selected pesticides in honey samples from Kahramanmaraş, Turkey

In this study 32 pesticide residues and eight polybrominated diphenlyl ether (PBDE) congeners were measured in nine honey samples from Kahramanmaraş, Turkey. A new method based on the best recovery was column extraction with n-hexane/acetone followed by gas chromatography electron-capture detection (GC-ECD), and mass spectrometry (GC–MS). Generally the pesticide levels were low in the honey samples. γ-HCH and PCB 28 were being measured in all honey samples. The sum of HCHs in samples varied between 0.71 and 2.47 ng/g. Malathion, bromophos methyl, cis-HCE, chlordane, endrin, p,p′-DDE and o,p′-DDD were not detectable. The mean values of α-HCH and β-HCH were 0.60 and 0.52 ng/g. The mean values of HCB, α-chlordan, trans-nonachlor, cis-nonachlor, Heptachlor, aldrin, bromophos ethyl, trans-HCE, α-endosulfan, β-endosulfan, dieldrin were 0.30, 0.05, 0.14, 0.84, 0.04, 0.06, 2.74, 0.03, 0.09, 0.27, 0.36 ng/g respectively. In none of the samples PBDEs were detected.