Evaluation and application of a simple and rapid method for the analysis of aflatoxins in commercial foods from Malaysia and the Philippines.

For application to the analysis of aflatoxins (AF) in commercial peanut and corn products, the ISOLUTE multimode column (IMC, solid phase multifunctional column) method was validated by comparing with the modified Florisil column (MFC) method. Twenty-two peanut and eight corn products from Malaysia and the Philippines were analysed for AFB1, AFB2, AFG1 and AFG2 firstly by the MFC method and then by the IMC method. For peanut products, 14 out of 22 samples were positive by the two methods in the range of 1-378 micrograms/kg of AF, and correlation coefficients (r) for AFB1 and AFB2 were 0.987 and 0.997, respectively. For corn and corn products, all the samples were positive in the range of 1-130 micrograms/kg, and r values were 0.992 and 0.805 for AFB1 and AFB2 respectively. Thus, the results were significantly (p < 0.01) in close agreement, particularly for lower range of 1-50 micrograms/kg of AF concentrations in all the samples. For the occurrence of AF, 11 (65%) of peanut products from Malaysia were contaminated with AF at a mean level of 50 micrograms/kg (maximum 180 micrograms/kg) and two (40% products from the Philippines were contaminated with as high as 375 micrograms/kg and 177 micrograms/kg of AF, respectively. All the corn products from the Philippines were contaminated with AF at a mean level of 44 micrograms/kg (maximum 130 micrograms/kg). Contamination of commercial foods with high levels of AF is a very important issue to both the countries since these foods are very popular among children.     

Occurrence of aflatoxins, ochratoxin A, and fumonisins in retail foods in Japan

We conducted a survey of aflatoxin B1, B2, G1, and G2, ochratoxin A, and fumonisin B1, B2, and B3 contamination in various foods on the retail market in Japan in 2004 and 2005. The mycotoxins were analyzed by high-performance liquid chromatography, liquid chromatography-mass spectrometry, or high-performance thin-layer chromatography. Aflatoxins were detected in 10 of 21 peanut butter samples; the highest concentration of aflatoxin B1 was 2.59 microg/kg. Aflatoxin contamination was not found in corn products, corn, peanuts, buckwheat flour, dried buckwheat noodles, rice, or sesame oil. Ochratoxin A was detected in oatmeal, wheat flour, rye, buckwheat flour, green coffee beans, roasted coffee beans, raisins, beer, and wine but not in rice or corn products. Ochratoxin A concentrations in contaminated samples were below 0.8 microg/kg. Fumonisins were detected in popcorn, frozen corn, corn flakes, and corn grits. The highest concentrations of fumonisins B1, B2, and B3 in these samples were 354.0, 94.0, and 64.0 microg/kg, respectively.     

Monoclonal-based enzyme-linked immunosorbent assay for the detection of zearalenone in cereals.

A monoclonal antibody against zearalenone (ZEA) was produced and used successfully to develop a direct competitive enzyme-linked immunosorbent assay (DC-ELISA) for the analysis of ZEA in cereals. This DC-ELISA had a limit of detection of 0.15 +/- 0.02 microg l(-1) and an IC50 value of 1.13 +/- 0.16 microg l(-1). Matrix interference was minimized by dilution of the sample extract before ELISA assays. Aqueous methanol (80%) gave good extraction efficiencies, and the recovery from spiked rice, barley, and corn samples averaged between 87 and 112%. Although ZEA was detected in seven (9%) of 80 rice samples and in eight (16%) of 50 barley samples, the concentration of ZEA in samples was around or below the limit of detection of DC-ELISA. Among 38 corn samples, ZEA was detected in nine (24%) samples in the range 41.0-909.8 microg kg(-1). Re-analysis of the ELISA-positive corn samples by high-performance liquid chromatography (HPLC) confirmed that seven (18%) corn samples were positive. The ZEA results for corn showed very good agreement between DC-ELISA and a commercial AgraQant zearalenone kit (r2 = 0.98). Thus, the monoclonal antibody-based DC-ELISA could be applied to the preliminary screening of ZEA contamination when analysis of a large sample number is needed.     

Monoclonal-based enzyme-linked immunosorbent assay for the detection of zearalenone in cereals

A monoclonal antibody against zearalenone (ZEA) was produced and used successfully to develop a direct competitive enzyme-linked immunosorbent assay (DC-ELISA) for the analysis of ZEA in cereals. This DC-ELISA had a limit of detection of 0.15 +/- 0.02 microg l(-1) and an IC50 value of 1.13 +/- 0.16 microg l(-1). Matrix interference was minimized by dilution of the sample extract before ELISA assays. Aqueous methanol (80%) gave good extraction efficiencies, and the recovery from spiked rice, barley, and corn samples averaged between 87 and 112%. Although ZEA was detected in seven (9%) of 80 rice samples and in eight (16%) of 50 barley samples, the concentration of ZEA in samples was around or below the limit of detection of DC-ELISA. Among 38 corn samples, ZEA was detected in nine (24%) samples in the range 41.0-909.8 microg kg(-1). Re-analysis of the ELISA-positive corn samples by high-performance liquid chromatography (HPLC) confirmed that seven (18%) corn samples were positive. The ZEA results for corn showed very good agreement between DC-ELISA and a commercial AgraQant zearalenone kit (r2 = 0.98). Thus, the monoclonal antibody-based DC-ELISA could be applied to the preliminary screening of ZEA contamination when analysis of a large sample number is needed.     

Updated profile of aflatoxin and Aspergillus section Flavi contamination in rice and its byproducts from the Philippines.

Our goal was to develop an updated profile of aflatoxin (AF) and AF-producing fungi contamination in rice and its byproducts from the Philippines. The total AF levels in 78 samples of polished and brown rice, determined by an immunoaffinity column clean-up method coupled with HPLC (detection limit: 25 ng/kg), ranged from <0.025-2.7 microg/kg (mean of positive samples: 0.37 microg/kg) and 0.03-8.7 microg/kg (mean of positive samples: 2.7 microg/kg), respectively. The incidence (% of positive samples) of AF in polished and brown rice were 94% and 100%, respectively. The AF levels in polished rice imported from Thailand and Vietnam were approximately 20% of the levels found in locally produced polished rice. AF levels decreased as the rice progressed through the various stages in milling. Fungi recovered include toxigenic Aspergillus flavus and A. parasiticus with an incidence ranging from 14% in rice bran to 78% in rough rice and producing <0.025-6200 microg/kg total AF in in vitro cultures on rice. All samples of rice bran and rice hull contained AF at levels ranging from 0.27-11 microg/kg. The estimated potential daily intake of AFB(1) from rice is between 0.1 and 7.5 ng/kg of body weight/day, the mean of which is 1.0 ng representing 9.1-5.3 times the estimated tolerable daily intake for AFB(1) reported to date for Asia. Thus, Filipinos have a potentially high risk of exposure to AF that can be easily controlled through proper post-harvest handling and storage of rice and its byproducts.     

Occurrence of aflatoxins B1, B2, G1, and G2 in peanuts and their products marketed in the region of Campinas, Brazil in 1995 and 1996.

Samples of peanuts and their products marketed in the region of Campinas, Brazil in 1995 and 1996 were analysed in terms of aflatoxin B1, B2, G1, and G2 by thin-layer chromatography, aiming at the protection of consumer health. Of the 80 samples analysed, 35 of peanuts and 45 of peanut products, 41 (51%) presented contamination with aflatoxin, 11 of them being peanuts (27%) and 30 being products (67%), in a range of 43 to 1099 micrograms/kg for B1 + B2 + G1 + G2 with a 90th percentile of 415 (B1 + G1) and of 615 (B1 + B2 + G1 + G2). The results also demonstrated that aflatoxin B1 (AFB1) reached the highest incidence and the highest upper limits compared with all the other aflatoxins.     

Aspergillus section Flavi and aflatoxins in dried figs and nuts in Algeria

The presence of Aspergillus section Flavi and aflatoxin (AF) contamination was investigated in 112 samples of peanuts, almonds and dried figs collected in Algeria. The occurrence of aflatoxin B1 (AFB1), B2 (AFB2), G1 (AFG1) and G2 (AFG2) in different commodities has been determined with a sensitive method based on high performance liquid chromatography (HPLC) coupled with fluorescence detection with post-column photochemical derivatisation. Analytical results indicated that 28 samples of peanuts, 16 samples of almonds and 26 samples of dried figs contained detectable levels of AFs. A total of 69 samples (61.6%) were contaminated with AFB1 ranging from the limit of quantification to 174 µg kg^?1. AFB2 was found in 12 samples (10.7%) and varied from 0.18 to 193 µg kg^?1. Seven samples revealed AF concentrations lower than the limit of quantification. Eleven peanut and fourteen dried fig samples exceeded the European maximum limits for AFB1.     

Natural occurrence of aflatoxin B1 in marketed foods and risk estimates of dietary exposure in Koreans

Aflatoxin B1 (AFB1) is an unavoidable food contaminant. To evaluate the potential health risk of AFB1 to Koreans posed by food consumption, we determined the natural occurrence of AFB1 in food and estimated the excess risk for liver cancer through dietary exposure to AFB1. A total of 694 food samples collected from six different regions of South Korea were analyzed for their AFB, content. One hundred four of the 694 samples were found to give positive enzyme-linked immunosorbent assay (ELISA) readings for AFB1 and were further investigated with high-performance liquid chromatography. Thirty-two samples, including 2 maize samples, 3 soybean products, 20 peanut samples, nut samples, and their products, and 7 spices, were found to be contaminated with AFB1 (4.6% incidence), up to 48.6 microg kg(-1). The level of AFB1 contamination in 28 of the 32 food products was below 10 microg kg(-1), which is the legal tolerance limit in Korea. From data on daily food consumption, the exposure dose of AFB1 was estimated to be 6.42 x 10(-7) mg kg(-1) body weight (bw) day(-1). The major contributors to the dietary intake of AFB1 were soybean paste and soy sauce, which composed 91% of the total exposure to AFB1. The excess risk of liver cancer for those exposed to AFB1 through food intake was estimated to be 5.78 x 10(-6) for hepatitis B-negative individuals and 1.48 x 10(-4) for hepatitis B-positive individuals. These results suggest that special consideration is required to reduce the intake of AFB1 in hepatitis B-positive individuals.     

Natural and in vitro coproduction of cyclopiazonic acid and aflatoxins

Eighty samples of animal feeds of different origins were screened for the natural co-occurrence of cyclopiazonic acid (CPA) and aflatoxins in Portugal. Forty-five strains of Aspergillus flavus were collected from those samples and studied for their ability to produce these mycotoxins, in vitro. CPA was detected by thin-layer chromatography using Erhlich's reagent for confirmation. Aflatoxins were determined by high-pressure liquid chromatography with postcolumn iodination. Only 5 of the 80 samples (6.2%) were naturally contaminated with cyclopiazonic acid (0.16 mg/kg) and 36 (45.0%) with aflatoxin B1 (AFB1) (from 0.001 to 0.016 mg/kg). An in vitro study of the 45 strains of A. flavus was performed in cracked corn at 25 degrees C (water activity, a(w) = 0.96), incubated for 21 days to CPA production. For in vitro production of aflatoxins, the same substrate was incubated at 28 degrees C for 14 days. Nineteen of the strains (42.2%) produced CPA (ranging from 0.5 to 1.45 mg of CPA/kg) and 23 of them (51.1%) produced AFB1 (from 0.001 to 0.844 mg/kg). Only 10 isolates (22.2%) produced both CPA and AFB1 (0.05 to 0.10 mg/kg and 0.001 to 0.230 mg/kg, respectively). Thirteen strains did not produce either CPA nor AFB1.     

Aflatoxin residues in eggs of laying Japanese quail after long-term administration of rations containing low levels of aflatoxin B1.

The aim was to evaluate the excretion of residues of aflatoxin B(1) (AFB(1)), aflatoxin M(1) (AFM(1)), aflatoxin B(2a) (AFB(2a)) and aflatoxicol (AFL) in eggs of laying Japanese quail fed rations with low levels of aflatoxin B(1) for 90 days. The quail were randomly assigned into four experimental groups and given prepared rations containing either 0 (controls), 25, 50 or 100 microg AFB(1) kg(-1) feed. Thirty-two eggs per treatment were collected on days 1-7, 10, 20, 30, 60 and 90 of the aflatoxin treatment period, and submitted to aflatoxin analysis by high-performance liquid chromatography. Average egg production and feed consumption were not affected ( p > 0.05) by AFB(1). Egg weight was significantly lower ( p<0.05) only for groups exposed to 100 microg AFB(1) kg(-1). Residues of aflatoxins were detected in eggs at levels that ranged from 0.01 to 0.08 microg kg(-1) (AFB(1)), 0.03-0.37 microg kg(-1) (AFM(1)), 0.01-1.03 microg kg(-1)(AFB(2a)) and 0.01-0.03 microg kg(-1) (AFL). Results indicate that the excretion of aflatoxin residues in quail eggs might occur at relatively low concentrations under conditions of long-term exposure of quail to low levels of AFB(1).     

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.     

Distribution of fumonisins in dry-milled corn fractions in Argentina.

Corn samples and different dry-milled fractions collected from an industrial mill in Argentina were analysed. Average contaminations were FB(1) 1540 microg kg(-1), FB(2) 716 microg kg(-1) and FB(3) 152 microg kg(-1) in whole corn; FB(1) 135 microg kg(-1), FB(2) 39.1 microg kg(-1) and FB(3) 10.2 microg kg(-1) in corn grits; FB(1) 358 microg kg(-1), FB(2) 122 microg kg(-1) and FB(3) 45.9 microg kg(-1) in 'C' flour; FB(1) 148 microg kg(-1), FB(2) 52.5 microg kg(-1) and FB(3) 28.3 microg kg(-1) in corn meal; and FB(1) 4210 microg kg(-1), FB(2) 2010 microg kg(-1) and FB(3) 447 microg kg(-1) in germ and bran together. The fumonisin contamination level was approximately three times higher in germ and bran than in whole corn, 13 times higher than in 'C' flour and 29 times higher than in corn meal and corn grits. Taking into account the distribution of fumonisins in commercial dry-milled corn fractions and corn meal consumption in Argentina, a theoretical whole corn level of 6640 microg kg(-1) maximum of total fumonisins could be processed to obtain products considered safe for human health.     

Investigation of ochratoxin a, B and citrinin contamination in various commercial foods

Ochratoxin A (OTA), ochratoxin B (OTB) and citrinin (CIT) in commercial foods were simultaneously determined and confirmed with high-performance liquid chromatography (HPLC) and liquid chromatography coupled with tandem mass spectrometry (LC/MS/MS). The samples examined were made up of cereal, fruit, coffee, and cacao products. The limits of quantification (S/N> or =10) of OTA, OTB and CIT were 0.1 microg/kg or less. Aflatoxins (AF), deoxynivalenol (DON) and fumonisins were also surveyed. Of 157 samples examined, 44 were contaminated with OTA at levels of 0.11 to 4.0 microg/kg. At least 2 positive samples were labeled as domestics. In most positive samples, the OTA level was low, less than 1 microg/kg. The highest incidence of OTA was observed in cacao powder (10/12), followed by instant coffee (5/7), cocoa (5/8) and raisin (6/13). OTB was found in fruit and cacao products containing relatively high levels of OTA. Co-occurrence of OTA, CIT and DON was found in cereal products, and co-occurrence of OTA and AF was found in cacao products. Approximately 30% of naturally contaminated OTA in roasted coffee bean moved into the extract solution when brewed with paper filter.     

Occurrence of Aspergillus spp. and aflatoxin B1 in Malaysian foods used for human consumption

Malaysian population widely consumes the cereal-based foods, oilseeds, nuts, and spices in their daily diet. Mycotoxigenic fungi are well known to invade food products under storage conditions and produce mycotoxins that have threat to human and animal health. Therefore, determining toxigenic fungi and aflatoxin B(1) (AFB1) in foods used for human consumption is of prime importance to develop suitable management strategies and to minimize risk. Ninety-five food products marketed in Penang, Malaysia were randomly collected from different supermarkets and were analyzed for presence of Aspergillus spp. by agar plate assay and AFB1 by enzyme-linked immunosorbent assay (ELISA). A. flavus was the dominant fungi in all foods followed by A. niger. Fifty-five A. flavus strains were tested for their ability to produce aflatoxins on rice grain substrate. Thirty-six (65.4%) strains out of 55 produced AFB1 ranging from 1700 to 4400 μg/kg and 17 strains (31%) produced AFB2 ranging from 620 to 1670 μg/kg. Natural occurrence of AFB1 could be detected in 72.6% food products ranging from 0.54 to 15.33 μg/kg with a mean of 1.95 μg/kg. Maximum AFB1 levels were detected in peanut products ranging from 1.47 to 15.33 μg/kg. AFB1 levels detected in all food products were below the Malaysian permissible limits (<35 μg/kg). Aspergillus spp. and AFB1 was not detected in any cookies tested. Although this survey was not comprehensive, it provides valuable information on aflatoxin levels in foods marketed in Malaysia.     

Natural co-occurrence of aflatoxin B1, fumonisin B1 and ochratoxin A in barley and corn foods from Korea

A survey for aflatoxin B₁ (AFB₁), fumonisin B₁ and ochratoxin A (OTA) was conducted on 127 samples that included 30 food-grade barley, 32 barley foods, 18 food-grade corn and 47 corn foods, randomly collected during 1998-99 in Seoul, Korea. The presence of mycotoxins was analysed by direct competitive enzyme-linked immunosorbent assay (ELISA), and most of the positive samples from ELISA were confirmed using high-performance liquid chromatography (HPLC). Recoveries of AFB₁ and OTA spiked at 10 ng g -1 and FB₁ spiked at 50 ng g^-1 were 106, 87 and 105% by ELISA, whereas those by HPLC were 80, 79 and 84%, respectively. Detection limits by ELISA for AFB₁, FB₁ and OTA were 1, 5 and 5 ng g^-1, and those by HPLC were 0.6, 35 and 1 ng g^-1. Naturally occurring AFB₁, FB₁ and OTA were found in 4/32 (12%), 2/32(6%) and 4/32 (12%) samples of barley foods with an average of 26, 16 and 9 ng g^-1, respectively. AFB₁ and FB₁ in corn foods were detected in 4/47 (8%) and 9/47 (19%) samples with the average being 20 and 74 ng g^-1, while no OTA was found in any corn foods samples. No AFB₁, FB₁ or OTA was detected in any of food-grade barley and corn samples. This is the first report on the natural co-occurrence of AFB₁ and FB₁ in barley and corn foods as well as on surveillance of OTA in Korea.     

Aflatoxin B1 contamination in wheat grain samples collected from different geographical regions of India: A multicenter study

In a multicenter study conducted by the Indian Council of Medical Research, 1,646 samples of wheat grain collected from rural and urban areas of 10 states representing different geographical regions of India were analyzed for aflatoxin B1 (AFB1). AFB1 concentrations of > or = 5 microg kg(-1) were recorded in 40.3% of the samples, and concentrations above the Indian permissible regulatory limit of 30 microg kg(-1) were found in 16% of the samples. The proportion of samples with AFB1 concentrations above the Indian regulatory limit ranged from 1.7 to 55.8% in different states, with the minimum in Haryana and the maximum in Orissa. The variation in wheat contamination among states seems to be mainly the result of unsatisfactory storage conditions. Median AFB1 concentrations of 11, 18, and 32 microg kg(-1) were observed in samples from Uttar Pradesh, Assam, and Orissa, respectively; concentrations in other states were <5 microg kg(-1). The maximum AFB1 concentration of 606 microg kg(-1) was observed in a sample from the state of Uttar Pradesh. The calculated probable daily intakes of AFB1 through consumption of contaminated wheat for the population in some states were much higher than the suggested provisional maximum tolerable daily intake. Human health hazards associated with such AFB1 exposure over time cannot be ruled out.     

Preparation of anti‐danofloxacin antibody and development of an indirect competitive enzyme‐linked immunosorbent assay for detection of danofloxacin residue in chicken liver

BACKGROUND: Danofloxacin is used widely as both a clinical medicine for humans and a veterinary drug in animal husbandry. In this study a polyclonal anti‐danofloxacin antibody was prepared for the first time and a simple and rapid indirect competitive enzyme‐linked immunosorbent assay (cELISA) method based on the antibody was developed to monitor danofloxacin residue in chicken liver. RESULTS: The prepared antibody showed high sensitivity, with an IC₅₀ value of 2.0 ng mL^?1 towards danofloxacin, and good specificity, with significant cross‐reactivity only towards pefloxacin (22%) and fleroxacin (21%) among commonly used (fluoro)quinolones evaluated in the study. The developed cELISA test kit had a detection limit of 0.8 ng mL^?1, and satisfactory results were obtained when it was applied to chicken liver spiked with various levels of danofloxacin. The cELISA test kit was also used to detect danofloxacin in chicken liver samples purchased from a local food market, and the results were confirmed by liquid chromatography/mass spectrometry. CONCLUSION: The anti‐danofloxacin antibody prepared in this study exhibits excellent quality, with high sensitivity and good specificity. The cELISA test kit based on the antibody has a very low detection limit and is suitable for use as an efficient screening method to detect danofloxacin residue in foods and food products. Copyright © 2009 Society of Chemical Industry     

Fumonisins in Brazilian corn-based foods for infant consumption.

A survey of 196 samples of corn-based infant foods from 13 cities of Sao Paulo State, Brazil, was carried out to investigate the fumonisin contamination in the products. Based on their ingredients, the products were divided into seven groups: infant cereal designated as types A-D, corn meal, corn starch and instant cereal baby food. Although certain infant food samples were free of fumonisin contamination (<20 microg kg(-1); corn starch and infant cereals of type A, B and D), contamination levels in the other products (corn meal, instant corn-based baby food and cereal type C) were of concern, particularly those in corn meal. All samples in these categories contained fumonisins. The mean level for total fumonisins (FB1 + FB2 + FB3) in corn meal was 2242 microg kg(-1) (maximum 8039 microg kg(-1)), in instant corn-based baby food was 437 (maximum 1096) microg kg(-1) and in infant cereal type C was 664 (maximum 1753) microg kg(-1).     

Limited survey for the occurrence of aflatoxins in cereals and poultry feeds from Rabat, Morocco

Fifty eight (58) samples of cereals for human consumption (20 corn flour, 17 wheat flour) and poultry feeds (n=21) purchased from popular markets of Rabat in Morocco were analyzed for aflatoxins (AF) by HPLC with immunoaffinity column (IAC) clean-up and fluorimetric detection. The incidence of AF in corn, wheat flour and poultry feeds was about 80, 17.6 and 66.6% respectively. High contamination levels were found in corn and poultry feeds samples. Levels of contamination of analyzed samples with AFB1 ranged from 0.23 to 11.2, 0.03 to 0.15 and 0.05 to 5.38 ng/g for corn, wheat and poultry feeds respectively. Results showed also that the contamination of 10% of samples of corn was higher than the limit set by EU regulations for AFB1 and total AF. This is the first report on the determination of AF in corn, wheat and poultry feeds from Morocco by HPLC and IAC.     

基于适配体亲和磁珠的黄曲霉毒素B1单样本前处理试剂盒的制备及应用

黄曲霉毒素B₁(aflatoxin B₁, AFB₁)适配体共价偶联于磁珠表面制备适配体亲和磁珠(aptamer affinity magnetic beads, AAMB),将AAMB、孵育液、洗涤液和洗脱液预封装于试剂条中开发了AFB₁单样本前处理试剂盒,借助真菌毒素全自动净化仪实现了AFB₁前处理的自动化,使用超高效液相色谱仪对洗脱液中AFB₁的含量进行测定。通过优化磁珠粒径、适配体间接臂长度、适配体亲和磁珠用量、孵育液体积确定了AAMB的制备条件以及AFB₁单样本前处理试剂盒的使用条件,对比了手动和自动两种前处理方式下AAMB回收率的差异。在优化条件下,AFB₁的检出限(limit of detection, LOD)为0.6 ng/mL,玉米和小麦中低、中、高三个水平的加标回收率在92.8%～110.1%之间,日内精密度的相对标准偏差(relative standard deviation, RSD)小...