赭曲霉毒素A时间分辨荧光侧流层析试纸条的研究

目的 构建一种基于时间分辨荧光纳米微球的赭曲霉毒素A (ochratoxin A, OTA)侧流层析试纸条。方法 基于免疫层析原理, 以时间分辨荧光纳米微球为信号探针, 降低非特异性荧光的干扰, 提高检测灵敏度, 并通过优化样品提取液和样品稀释液, 进一步提高现场检测OTA的灵敏度和准确性。结果 OTA在1~50 μg/kg范围内, T线和C线荧光强度的比值与OTA浓度的对数值具有良好的线性关系, 相关系数r2为0.9981~0.9998。不同基质中OTA的检出限(limit of detection, LOD)和定量限(limit of quantitation, LOQ)分别为0.401 μg/kg~0.614 μg/kg和0.970 μg/kg~1.617 μg/kg, 加标回收率为89.53%~118.37%, 相对标准偏差(relative standard deviations, RSDs)小于12% (n=3), 且与呕吐毒素、伏马菌素B1、黄曲霉毒素B1、玉米赤霉烯酮和T-2毒素的交叉反应率均小于5%, 特异性良好。基于荧光定量快速检测技术平台OTA侧流层析试纸条可在8 min内快速准确地定量检测出待测样本中OTA的含量。结论 本研究所制备的时间分辨荧光侧流层析试纸条可实现玉米、小麦和饲料中OTA的快速定量检测, 并具有成本低、灵敏度高、操作简便、准确高、重复性好、特异性好的优点, 可满足国内外OTA检测的技术要求, 为真菌毒素快检技术的发展提供技术支撑。     

时间分辨荧光免疫层析法定量检测谷物中黄曲霉毒素B1和玉米赤霉烯酮残留

建立了一种快速定量检测谷物产品中黄曲霉毒素(Aflatoxin B1,AFB1)和玉米赤霉烯酮(Zearalenone,ZEN)的时间分辨荧光免疫层析方法。采用时间分辨荧光微球标记黄曲霉毒素B1抗体和玉米赤霉烯酮抗体,研究了如p H值、标记抗体浓度、荧光探针使用量、检测T线包被原浓度、质控C线羊抗鼠Ig G浓度、样品前处理方法等因素对时间分辨荧光免疫层析方法灵敏度的影响。结果表明:AFB1的检出限为0.80 ng/mL,线性范围(IC20~IC80)为0.81~5.67 ng/mL,半抑制浓度(IC50)为2.15 ng/mL。在ZEN检出限为4.58 ng/mL,线性范围(IC20~IC80)为4.76~85.60 ng/mL,半抑制浓度(IC50)为20.19 ng/mL。方法特异性良好,与T-2毒素、脱氧雪腐镰刀菌烯醇、伏马毒素、赭曲霉毒素A多种真菌毒素交叉率小于10%。通过选择玉米、麦麸、大豆、小麦进行添加回收试验,AFB1的添加回收率在97.1%~108.7%之间,ZEN的添加回收率在92.8%~109.1%之间,相对标准偏差小于15%。选取经HPLC-MS/MS检测过的FAPAS标准质控样本进行测试,检测结果与其结果一致。在实际产品检测对比中,与市售胶体金免疫层析卡,ELISA试剂盒的检测结果基本一致。本方法操作简单快速、可定量,检测过程约25 min,适用于谷物样品中黄曲霉毒素B1和玉米赤霉烯酮的现场快速筛。     

CdTe量子点标记同时检测黄曲霉毒素B_1和赭曲霉毒素A的新方法研究

将制备的不同发射波长的CdTe发光量子点分别标记于黄曲霉毒素B1(AFB1)、赭曲霉毒素A(OTA)的抗体上作为荧光显示探针,将制备的Fe_3O_4磁性纳米粒子与AFB1、OTA人工抗原结合形成捕获探针,通过免疫竞争反应、磁分离富集效应,建立一种在同一激发波长下,同时检测AFB1和OTA的检测新方法。     

基于核酸适配体的侧流层析技术同步检测赭曲霉毒素A和黄曲霉毒素B1

由于简单、低成本和快速的特点,侧流层析分析技术被广泛应用于食品、饲料和农产品中真菌毒素的检测。本实验基于适配体与靶标物特异性结合的原理,建立了基于适配体互补链同时检测赭曲霉毒素A（Ochratoxin A, OTA）和黄曲霉毒素B1（Aflatoxin B1, AFB1）两种真菌毒素的荧光多残留试纸条,通过优化两种适配体的浓度以及缓冲体系的PH值,提高了共同检测OTA和AFB1的灵敏度和准确性。OTA和AFB1的T线（TO和TA）和C线荧光强度比值与对应真菌毒素的浓度对数具有良好的线性关系,线性范围为0.5~50 ng/mL,相关系数r2分别为0.9887和0.9910,检出限低至0.51和0.38 ng/mL。通过对花生和葡萄干进行加标回收和实际样品检测,使用多残留试纸条检测的OTA和AFB1的回收率分别为82.06%~109.69%和83.34%~110.06%,相对标准偏差（Relative Standard Deviation, RSD）为1.89%~8.17%,检测结果与高效液相色谱-串联质谱法（HPLC-MS/MS）一致。该生物传感器可以在20 min内同时检测OTA和AFB1,并且具有成本低、检测速度快和易于操作等优点,可以满足花生和葡萄干等实际样品中OTA和AFB1残留量的现场快速检测的要求,为真菌毒素多残留检测提供理论依据和技术支撑。     

黄曲霉毒素B1/呕吐毒素/玉米赤霉烯酮真菌毒素三合一时间分辨荧光定量快速检测卡的优化

改进了一种基于时间分辨荧光纳米微球的黄曲霉毒素B1/呕吐毒素/玉米赤霉烯酮真菌毒素三合一荧光定量快速检测卡，一次提取，一次检测，8 min内即可得到三个项目的检测结果，快速、简易、省时省力。本项目成功优化了黄曲霉毒素B1/呕吐毒素/玉米赤霉烯酮真菌毒素三合一荧光定量快速检测卡的时间分辨纳米微球的整个制备工艺，解决了玉米赤霉烯酮（简称ZEN）的灵敏度低、黄曲霉毒素B1（简称AFB1）的均一性差、样本检测C线线条扩散等等问题。通过对微球制备工艺、微球表面修饰不同数量碳原子手臂，确认了ADZ检测卡中ZEN胶乳所用的荧光微球，即南京微测生物的200原子手臂的时间分辨荧光微球，解决了ZEN灵敏度低的问题；通过对样品垫的选择、样品垫缓冲液配方的优化，确认了样品垫工艺，即用上海捷宁生物的G-6玻纤垫，并处理样品垫缓冲液配方3，解决了AFB1的均一性差问题；通过对抗原稀释液的优化，确认了用50 mM PBS+5%蔗糖划膜液，解决了样本C线线条扩散问题。     

赭曲霉毒素A时间分辩荧光定量检测体系适用性评价

目的验证赭曲霉毒素A(ochratoxin A,OTA)时间分辨荧光免疫定量检测体系对谷物中赭曲霉毒素A快速检测的适用性。方法该时间分辨荧光免疫定量检测体系包括时间分辨荧光免疫层析检测卡和时间分辩荧光定量检测仪。时间分辨荧光速测仪内置标准曲线,直接得出待测样品中赭曲霉毒素A的含量。对待测样品进行低、中、高3个浓度添加,每个浓度分为7份,由不同人员检测。同时,对实际阳性样品进行检测。结果对谷物做赭曲霉毒素A添加回收率实验,回收率在98%~113%之间;批内变异系数15%。在实际样品的检测中,时间分辨荧光定量检测卡得出的数值,与质控样本标识的值没有显著性差异。结论时间分辨荧光定量检测系统检测快速、准确,稳定、检测设备小型化、联网可实现数据上传,适用于大批量谷物样品的快速检测和风险评估。     

基于核酸适配体检测玉米中的赭曲霉毒素A

目的 建立一种基于核酸适配体检测玉米中赭曲霉毒素A (ochratoxin A, OTA)的方法。方法 以微孔板为载体, 采用偶联生物素和Cy3荧光标记的核酸适配体与OTA的特异性结合, 而与偶联黑洞淬灭探针(black hole quencher 2, BHQ2)的互补序列无法配对, 导致荧光值变化从而实现对OTA的定量检测。结果 优化的条件为链亲和素质量浓度为100 μg/mL, 核酸适配体浓度为200 nmol/L, 互补序列浓度为400 nmol/L, OTA在0.05~10.00 ng/mL范围具有较好的线性关系。与赭曲霉毒素B、黄曲霉毒素B1、脱氧雪腐镰刀菌烯醇和玉米赤霉烯酮的交叉反应率均低于1%, 玉米样品中添加OTA的平均回收率为89.0%~93.8%。结论 该方法快速、准确、灵敏, 交叉反应率低, 可用于样品中OTA的分析检测。     

赭曲霉毒素A检测方法的研究进展

赭曲霉毒素A(ochratoxin A, OTA)是一种具有极端毒性、污染广泛及危害严重的次级代谢产物。由于赭曲霉毒素A具有这些特点且食品安全问题越来越被人们广泛关注, 所以确定食品和商品中的OTA污染水平非常重要。目前对于OTA的检测, 已经建立了非常多的分析手段, 如薄层色谱法(thin layer chromatography, TLC)、高效液相色谱法(high performance liquid chromatography, HPLC)、酶联免疫技术(enzyme linked immunosorlent assay, ELISA)、时间分辨荧光免疫分析技术(time-resolved fluoroimmunoassay, TRFIA)等。本文综述了多种赭曲霉毒素A的检测分析方法, 简介了它们的优缺点及研究进展, 并进行了比较, 以期为食品中赭曲霉毒素A的检测研究提供一些参考。     

霉菌毒素在肉鸡体内的残留及其控制研究?

为研究霉菌毒素在肉鸡体内的残留情况,并对3种霉菌毒素吸附剂的控制吸附效果评价,选用210羽三黄鸡,随机分成7组,每组3个重复,每个重复10羽.试验鸡分为试验组Ⅰ(霉菌毒素含量AFB124.71 ng/g;OTA 12.3 ng/g;ZEA 274.62 ng/g),试验组Ⅱ(AFB1 41.18 ng/g;OTA 20.57 ng/g;ZEA 457.7 ng/g),其他各组分别为对照组和试验组添加霉菌毒素吸附剂A与吸附剂B,试验期21 d.结果表明,霉菌毒素严重影响肉鸡的生长性能,添加吸附剂有效改善肉鸡的生长性能.试验组Ⅰ肉鸡肝内AFB1 、OTA、ZEA的残留量分别为(5.07±0.21)ng/g、(1.17±0.06) ng/g、(16.57±1.00) ng/g,肾脏为(2.57±0.25)ng/g、(2.83±0.25) ng/g、(12.17±1.73) ng/g;试验组Ⅱ肝内残留分别为(7.80±0.36) ng/g、(1.83±0.35) ng/g、(20.60±0.90) ng/g,肾脏为(3.90±0.20) ng/g、(4.50±0.75) ng/g、(18.33±0.85) ng/g.添加霉菌毒素吸附剂后,均可有效减低体内残留;AFB1、OTA、ZEA在肝中的含量分别下降了40.64％、8.74％、15.87％,肾中则降低了24.90％、18.73％、30.98％,而从粪便中排出量分别提高了93.41％、40.24％、72.58％.     

磁分离结合CdTe发光量子点标记黄曲霉毒素B1免疫检测新方法

将发光量子点标记技术与磁分离富集技术相结合,基于竞争免疫分析,成功构建了黄曲霉毒素B1(AFB1)免疫检测新方法。首先合成了巯基丙酸包覆的CdTe发光量子点,同时采用水热法合成了氨基化磁性纳米粒子,通过TEM成像、荧光光谱、XRD、红外光谱等分别对其进行了表征。随后以AFB1人工抗原功能化磁性纳米粒子作为捕获探针,以发光量子点标记免疫球蛋白G(二抗)作为信号探针,基于磁性纳米粒子表面AFB1人工抗原和样品中AFB1与AFB1单克隆抗体之间的竞争免疫结合,建立了AFB1新型检测方法。实验优化条件下,荧光强度与黄曲霉毒素B1质量浓度在0.1~100 ng/mL范围内呈良好的线性关系,检测限为0.03 ng/mL。实际样品中加标回收实验结果表明,新方法准确性良好。     

Time-resolved fluorescent immunochromatographic assay-based on three antibody labels for the simultaneous detection of aflatoxin B1 and zearalenone in Chinese herbal medicines

ABSTRACT

A time-resolved fluorescent immunochromatographic assay (TRFICA) was successfully developed for the sensitive, simultaneous, and quantitative detection of aflatoxin B₁ (AFB1) and zearalenone (ZEN) in Chinese herbal medicines. Eu-nanospheres (EuNPs) with unique optical properties increased the stability and sensitivity of the immunochromatographic assay. To obtain stable quantitative results, we applied a three-label system in which monoclonal antibodies for AFB1 and ZEN were conjugated to the EuNPs as detection probes on the test line (T line), and EuNP-labelled chicken IgY conjugates acted as the reference on the control line (C line). The fluorescence intensities of the T and C lines were recorded, and the T/C ratio was employed as the quantitative signal for the elimination of strip variation and matrix effects. The parameters that affected the TRFICA were optimised. Under optimal conditions, the established TRFICA gave good linear ranges from 0.60 μg/kg to 3.92 μg/kg for AFB1 and from 0.40 μg/kg to 1.28 μg/kg for ZEN. The limits of detection for AFB1 and ZEN were as low as 0.60 and 0.40 μg/kg, respectively, in Chinese herbal medicines Semen coicis, Rhizoma dioscoreae, and Platycodon grandiflorus, respectively. The average recoveries of the spiked samples were 73%–95% for AFB1 and 75.83%–90% for ZEN, both with a relative standard deviation of < 9.08%. The results of 15 actual samples detected by the developed TRFICA showed a satisfactory correlation with those of ultra-performance liquid chromatography tandem mass spectrometry. Therefore, the TRFICA is a simple, rapid, and sensitive approach to quantitatively detect mycotoxins in Chinese herbal medicines.     

牦牛肉中阿维菌素残留的时间分辨荧光免疫层析检测方法的建立

为建立定量检测牦牛肉中阿维菌素残留的时间分辨荧光免疫层析方法,以羧基化铕微球作为荧光标记物,与阿维菌素鼠单克隆抗体G10703进行共价偶联后喷涂于释放垫上,将阿维菌素抗原和羊抗鼠免疫球蛋白G分别包被于硝酸纤维素膜上作为检测线（T）和质控线（C）,制备免疫层析试纸条;利用牦牛肉样本阿维菌素添加量和对应的T线与C线荧光信号峰值比值（T/C）拟合得到四参数标准曲线,建立牦牛肉中阿维菌素残留的时间分辨荧光免疫层析检测方法,并对所建立方法的灵敏度、准确度、特异性、精密度和稳定性等进行评价,用液相色谱-串联质谱方法对所建立方法的性能进行确证。结果表明：本方法对牦牛肉中阿维菌素的定量限为1.0 μg/kg,加标回收率为86.9%～105.2%,与阿维菌素、伊维菌素、多拉菌素及依普菌素的交叉反应率分别为100.0%、73.1%、42.6%和97.5%,批内变异系数为5.4%～9.5%,批间变异系数为7.5%～11.2%,该方法准确度、精密度、灵敏度均较高,且性能稳定。     

量子点标记免疫层析试纸条快速检测谷物中赭曲霉毒素A

目的:根据竞争抑制免疫层析原理,构建一种基于量子点标记的免疫层析试纸条用于检测谷物中赭曲霉毒素A(Ochratoxin A,OTA)的残留量。方法:通过活化酯法将羧基功能化的量子点(Quantum dot,QD)与赭曲霉毒素A多克隆抗体(Antibody,Ab)偶联制备量子点抗体偶联物(QD-Ab);通过分别添加不同量的QD-Ab和工作液,优化量子点标记免疫层析试纸条的工作条件;通过商品化试剂盒验证该方法的有效性。结果:当QD与Ab的摩尔比为1:10时,QD-Ab荧光特性最佳;在QD-Ab和工作液添加量分别为1、10 μL时,量子点标记免疫层析试纸条结果最佳;量子点标记免疫层析试纸条的检测限为0.5 μg/L,谷物样品中的检测限为5 μg/kg,整个检测过程不超过10 min;量子点标记免疫层析试纸条特异性良好且具有有效性。结论:该方法操作简便、检测快速、结果准确灵敏,易于判断,可以满足谷物中赭曲霉毒素A残留量现场快速检测的要求。     

构建下转换荧光-适配体的免疫层析试纸条用于快速检测黄曲霉毒素B1

构建下转换荧光-适配体免疫层析试纸条用于食品中黄曲霉毒素B1（aflatoxin B1,AFB1）的快速高效检测。体系中AFB1存在会减弱下转换荧光-适配体纳米颗粒层析至T线时与AFB1半抗原的结合能力,从而导致下转换荧光信号衰减,进而实现对AFB1的高效检测。该方法在AFB1质量浓度1～40 ng/mL范围内与荧光信号呈良好的线性关系,线性相关系数为0.994,检测限为0.287 ng/mL。该方法利用稀土掺杂荧光纳米颗粒的长寿命发光及近红外荧光特性,有效降低了生物背景荧光干扰并提高了检测体系的特异性。该方法在AFB1的快速高灵敏检测中具有良好的应用前景。     

4 种硝基呋喃代谢物复合荧光免疫层析试纸条的制备

为建立一种基于量子点荧光免疫层析技术快速检测4 种硝基呋喃类代谢物的方法,采用N-羟基琥珀酰亚胺（N-hydroxysuccinimide,NHS）、1-乙基-3-（3-二甲氨基丙基）碳二亚胺盐酸盐（1-ethyl-3-（3-dimethylaminopropyl）carbodiimide hydrochloride,EDC）法合成4 种硝基呋喃类代谢物的人工抗原,并融合制备对应的单克隆抗体,通过EDC-NHS一步法将量子点微球（quantum dot submicrobeads,QBs）分别与3-氨基-2-恶唑烷酮（3-amino-2-oxazolidinone,AOZ）、5-甲基吗啉-3-氨基-2-唑烷基酮（5-morpholine-methyl-3-amino-2-oxazolidinone,AMOZ）、1-氨基-2-乙内酰（1-aminohydantoin,AHD）和氨基脲（semicarbazid,SEM）偶联,得到相应的QBs探针,在此基础上制备复合荧光免疫层析试纸条。结果表明：AOZ、AHD、SEM和AMOZ的检出限分别为0.4、0.4、0.5、0.5 μg/L;通过加标回收实验对批内和批间的重复性和准确度进行评价,得出该试纸条的批内检测回收率为80%～110%,批内变异系数在15%以内,批间回收率为80%～100%,批间变异系数在15%以内;且AOZ、AHD、SEM和AMOZ之间的交叉反应率小于0.1%,说明成功将荧光免疫层析技术和多元检测技术相结合,应用于同时检测4 种硝基呋喃类代谢物,且试纸条的灵敏度和准确性高、特异性好。     

Aflatoxins and ochratoxin A in flour: a survey of the Serbian retail market

This report presents data on the occurrence of aflatoxins (AF) and ochratoxin A in different types of flour marketed in Serbia. A total of 114 samples of wheat, buckwheat, rye, oat, barley, rice, millet and corn flour were collected in the period 2012–2016 and analysed using high performance liquid chromatography with fluorescence detection. Among flours other than corn, AFB1 was quantified only in rice, while ochratoxin A (OTA) was found in 29% of the samples. In corn flours the percentage of positive samples varied greatly over the years: AFB1 7.1–80.0%, OTA 30.0–40.6%, with a co-occurrence of 7.1–34.4%. Overall 5.2% of flours other than corn and 10.7% of corn flours exceeded the maximum levels (MLs) for AFB1 and/or OTA. The highest recorded levels were 8.80 μg kg^?1 of AFB1 (corn) and 23.04 μg kg^?1 of OTA (rye). Overall mean contamination levels of corn flours were 0.53 μg kg^?1 of AFB1 and 0.46 μg kg^?1 of OTA.     

A Survey of Barley,Malt and Beer Contamination with Ochratoxin A in Turkey

The presence of ochratoxin A (OTA) was investigated in barley, malt and beer samples using an ELISA method (RIDASCREEN). The lower detection limit of this OTA test was 0.08 μg/L for beer and 0.4 μg/kg for barley and malt. In 26 out of 29 barley samples the OTA content was between 0.53–12 μg/kg. OTA was between 0.5–6.6 μg/kg in 23 out of 24 malt samples. Only one malt sample had no detectable OTA using RIDASCREEN. The OTA content was between 0.1–8.10 μg/L in 42 out of 150 beer samples (28%) and in 108 beer samples OTA was not found at detectable levels (72%). Only one beer sample contained more than 5 μg/L OTA.     

Validation of the procedure for the simultaneous determination of aflatoxins ochratoxin A and zearalenone in cereals using HPLC-FLD

Method validation for quantitative analysis of aflatoxins (AFs), ochratoxin A (OTA) and zearalenone (ZEA) in cereals using HPLC with fluorescence detector (FLD) is described. Mycotoxins were extracted with methanol?:?water (80?:?20) and purified with a multifunctional AOZ immunoaffinity column before HPLC analysis. The validation of the analytical method was performed to establish the following parameters: specificity, selectivity, linearity, limits of detection (LOD) and quantification (LOQ), accuracy, precision (within- and between-day variability), stability, robustness, measurement of performance, and measurement of uncertainty. Calibration curves were linear (r?>?0.999) over the concentration range, from the LOQ to 26, 40 and 400?ng/g for AFs, OTA and ZEA, respectively. LOD and LOQ were 0.0125 and 0.05?ng/g for aflatoxin B1 (AFB1) and G1 (AFG1), 0.0037 and 0.015?ng/g for aflatoxin B2 (AFB2) and G2 (AFG2), as well as 0.05 and 0.2?ng/g for OTA and 0.5 and 2?ng/g for ZEA, respectively. The mean recovery values were 77–104% for different concentrations of AFs, OTA and ZEA in spiked cereal samples. Both intra- and inter-day accuracy and precision were within acceptable limits. This method was successfully applied for the simultaneous determination of mycotoxins for 60 cereal samples collected from Malaysian markets. Fifty per cent of the cereal samples were contaminated with at least one of these mycotoxins, at a level greater than the LOD. Only one wheat sample and two rice samples were contaminated with levels greater than the European Union regulatory limits for AFs and OTA (4 and 5?ng/g). The means and ranges of mycotoxins obtained for the cereal samples were 0.4?ng/g and 0.01–5.9?ng/g for total AFs; 0.18?ng/g and 0.03–5.3?ng/g for OTA; and 2.8?ng/g and 2.4–73.1?ng/g for ZEA, respectively. The results indicate that the method is suitable for the simultaneous determination of AFs, OTA and ZEA in cereals and is suitable for routine analysis.     

A Sensitive Immunoaffinity Column-Linked Indirect Competitive ELISA for Ochratoxin A in Cereal and Oil Products Based on a New Monoclonal Antibody

A new sensitive monoclonal antibody (mAb) 1H2 against ochratoxin A (OTA) was reported herein. This mAb belonged to the immunoglobulin G1 (k chain) isotype. In the optimized indirect competitive enzyme-linked immunosorbent assay (icELISA), 1H2 showed a 50 % inhibition concentration (IC₅₀) value of 0.058 ng/mL and a detection limit (IC₁₀) of 0.001 ng/mL. The cross-reactivity of 1H2 with ochratoxin B, aflatoxins, deoxynivalenol, zearalenone, T-2 toxin, or fumonisins was below 0.3 %. Based on this mAb, an immunoaffinity column (IAC)-linked icELISA was developed for OTA detection in the cereal and oil products. The working range of the assay for solid sample was 0.36–16 μg/kg. The recoveries from spiked samples of IAC-linked icELISA ranged from 83 to 101 %. These recoveries were much higher than those of icELISA (21–78 %) and in good agreement with those obtained by using the standard high-performance liquid chromatography method (87–110 %). The results indicated that the mAb 1H2 had the values for studies of OTA in the crude agricultural products.     

Surveys of rice sold in Canada for aflatoxins, ochratoxin A and fumonisins

Approximately 200 samples of rice (including white, brown, red, black, basmati and jasmine, as well as wild rice) from several different countries, including the United States, Canada, Pakistan, India and Thailand, were analysed for aflatoxins, ochratoxin A (OTA) and fumonisins by separate liquid chromatographic methods in two different years. The mean concentrations for aflatoxin B(1) (AFB(1)) were 0.19 and 0.17 ng g(-1) with respective positive incidences of 56% and 43% (≥ the limit of detection (LOD) of 0.002 ng g(-1)). Twenty-three samples analysed in the second year also contained aflatoxin B(2) (AFB(2)) at levels ≥LOD of 0.002 ng g(-1). The five most contaminated samples in each year contained 1.44-7.14 ng AFB(1) g(-1) (year 1) and 1.45-3.48 ng AFB(1) g(-1) (year 2); they were mostly basmati rice from India and Pakistan and black and red rice from Thailand. The average concentrations of ochratoxin A (OTA) were 0.05 and 0.005 ng g(-1) in year 1 and year 2, respectively; incidences of samples containing ≥LOD of 0.05 ng g(-1) were 43% and 1%, respectively, in the 2 years. All positive OTA results were confirmed by LC-MS/MS. For fumonisins, concentrations of fumonisin B(1) (FB(1)) averaged 4.5 ng g(-1) in 15 positive samples (≥0.7 ng g(-1)) from year 1 (n = 99); fumonisin B(2) (FB(2)) and fumonisin B(3) (FB(3)) were also present (≥1 ng g(-1)). In the second year there was only one positive sample (14 ng g(-1) FB(1)) out of 100 analysed. All positive FB(1) results were confirmed by LC-MS/MS.