Rapid detection of aflatoxin B_1 in Chinese herbal medicines by indirect and direct competitive enzyme-linked immunosorbent assays: a comparative analysis / 中国中药杂志

The indirect competitive enzyme-linked immunosorbent assay(ic-ELISA) and direct competitive enzyme-linked immunosorbent assay(dc-ELISA) were performed for the rapid detection of aflatoxin B_1(AFB_1) in Astragali Radix, Zingiberis Rhizoma Recens, Jujubae Fructus, and Nelumbinis Semen with self-made antigens and antibodies. Different extraction methods were investigated to reduce the matrix effects of different medicinal parts in Chinese herbal medicines. The sensitivity of dc-ELISA method was improved by optimizing the molar ratio of AFB_1 to horseradish peroxidase(HRP). In this study, the sensitivity(IC_(50)) of ic-ELISA and dc-ELISA was 0.046 and 0.023 ng·mL~(-1), with the limit of detection(LOD) of 0.007 and 0.004 ng·mL~(-1), respectively. The detection time was 3 h and 50 min for ic-ELISA and dc-ELISA, respectively. The recovery rates were within the range of 62.96%-104.4%, with RSDs of less than 10%. Confirmed by LC-MS/MS, three positive samples of Nelumbinis Semen were detected from 53 samples. Two ELISA methods established in this study were accurate, rapid and sensitive, and can be used for rapid screening of AFB_1 in Chinese herbal medicines such as Astragali Radix, Zingiberis Rhizoma Recens, Jujubae Fructus, and Nelumbinis Semen. In addition, the advantages and limitations of the two methods were compared and discussed, which can provide a reference for the testing institutions to choose the proper method.

Preparation of highly sensitive monoclonal antibody against aflatoxin B_1 and its application in rapid detection of contamination in Ziziphi Spinosae Semen / 中国中药杂志

A highly sensitive monoclonal antibody against aflatoxin B_1(AFB_1) was prepared and an indirect competition enzyme-linked immunosorbent assay(ic-ELISA) was established based on the antibody which was used for high-throughput and rapid screening of AFB_1 contamination in Chinese herbal medicines to ensure the safety of medication. In this study, the structure of AFB_1 was modified by improved oxime method, and the carrier protein was coupled by EDC-NHS method to obtain the complete antigen of AFB_1, which was more convenient and environmental friendly. The Balb/c female mice were immunized using increasing the immunization dose and various ways of injection, and finally the AFB_1 monoclonal antibody was prepared. The AFB_1 monoclonal antibody belongs to IgG_(2 b) immunoglobulin by identifying its immunological characteristics, and its sensitivity(IC_(50)) can reach 0.15 μg·L~(-1), and the affi-nity is 2.81×10~8 L·mol~(-1). The cross-reaction rates of AFB_2, AFG_1, and AFG_2 were 35.07%, 8.75%, and 1.15%, respectively, and there was almost no cross-reactivity with other mycotoxins. Based on the high sensitivity and specificity of the antibody, an ic-ELISA method was established and applied to the determination of AFB_1 contamination in Ziziphi Spinosae Semen. According to the matrix matching standard curve, the linear concentration range for AFB_1 was 0.05-0.58 μg·L~(-1)(R~2=0.992), the recoveries were 88.00%-119.0%, and the detection limit was 1.69 μg·kg~(-1). The AFB_1 in 33 batches of Ziziphi Spinosae Semen samples was determined by ic-ELISA, and the contamination level was 3.62-206.58 μg·kg~(-1). The linear correlation coefficient between the detection results of ic-ELISA and UHPLC-MS/MS was 0.996, and there were no false positive and false negative cases. It indicates that the established ic-ELISA is accurate and reliable, and could provide a simple and effective technique for fast screening of AFB_1 contamination in Ziziphi Spinosae Semen, and also could be considered as the reference for the detection and monitoring of AFB_1 contamination in other Chinese herbal medicines.

QuEchERS pretreatment coupled to gas chromatography and tandem mass spectrometry to fast determination of 34 pesticide residues in Glycyrrhizae Radix et Rhizoma / 中国中药杂志

This study proposed a quantitative method for 34 pesticides including organochlorine,organophosphorus and pyrethroids in Glycyrrhizae Radix et Rhizoma herbs and medicinal slices,and analyzed the pesticide residues of collected Glycyrrhizae Radix et Rhizoma samples from different regions. With acetonitrile extraction and optimized Qu Ech ERS purification,the 32 batches of Glycyrrhizae Radix et Rhizoma herbs and medicinal slices were analyzed by matrix matching standard curve quantitative analysis under GC-MS/MS multi-response monitoring( MRM) mode. This study investigated the pretreatment of Glycyrrhizae Radix et Rhizoma samples based on the Qu Ech ERS method of Chinese Pharmacopoeia( 2015 edition,4),and the result showed that the recoveries of some pesticide was low and pigment has a strong interference in analysis,which result in worse purification effect. Therefore,this paper further optimized the Qu Ech ERS method and corrected the matrix matching standard curve method,and compensated the qualitative and quantitative effects of matrix effects on the detected target compounds in Glycyrrhizae Radix et Rhizoma. The results showed that 34 kinds of pesticide had good linear( R~2 of 0. 996 4 or higher) within a covering 0. 01-0. 2 mg·kg~(-1) concentration range. The limits of quantitation are less than 0. 01 mg·kg~(-1). This method was further applied to the simultaneous determination of 34 pesticide residues of typical organochlorine,organophosphorus and pyrethroids in 32 batches of Glycyrrhizae Radix et Rhizoma herbs and medicinal slices. Six batches containing beta-endosulfan,thiosulphate,o,p'-DDD and thrta-cypermethrin were detected,but none of them exceeded the limit of pesticide residues stipulated in the Chinese Pharmacopoeia and the EU Pharmacopoeia. This study indicates that the established method is rapid,convenient,accurate,and sensitive,which provides a rapid and efficient method for the simultaneous determination of typical organochlorine,organophosphorus and pyrethroids in Glycyrrhizae Radix et Rhizoma.

Survey on pesticide use in Crataegi Fructus and analysis of pesticide residues based on LC-ESI-MS/MS / 中国中药杂志

In order to study the pesticide residues of the medicinal Crataegi Fructus,this study aims to establish an analysis method for pesticide residues( mainly containing insecticides and fungicides) suitable for the actual situation of medicinal Crataegi Fructus based on the survey of the pesticides of the Crataegi Fructus base,combined with the blind screening results of the LC-ESI-MS/MS pesticide screening platform established by the research team in the early stage. Then,the pesticide residues in medicinal Crataegi Fructus from Shandong,Hebei,Henan,Shanxi,and Liaoning( main cultivation areas) were analyzed. The samples were pretreated by the modified Qu ECh ERS method,i.e.,extracted with acetonitrile-water( 9 ∶1),purified by PSA,C_(18),GCB,silica gel. The detection of pesticides was performed by LC-MS/MS. The ion source was ESI with positive scanning mode,and the linearity of 11 kinds of pesticides in the range of 5-300 μg·kg~(-1) was acceptable( R~2>0. 996 9). All the recoveries of pesticides were within 70. 02%~(-1)12. 0% in the low,medium and high levels,with RSD≤17%. The results showed that the detection rate of carbendazim,chlorpyrifos and difenoconazole is 79%,82%,56%,respectively. Besides,the prohibition pesticide carbofuran were detected in some of the batches,indicating the security risk. This study provides methodological references and basic data for risk assessment of Crataegi Fructus and government regulation.

Simultaneous determination of aflatoxin B_1,B_2,G_1,G_2,M_1,M_2 in Eupolyphaga Steleophaga by immunoaffinity column clean-up and HPLC-FLD with post-column photochemical derivatization / 中国中药杂志

The contamination of aflatoxin B_1,B_2,G_1,G_2,M_1 and M_2 in Eupolyphaga Steleophaga was determined by immunoaffinity column clean-up and HPLC-FLD with post-column photochemical derivatization. Chromatographic separations were carried out using a Cloversil C_(18) column( 4. 6 mm×250 mm,5 μm) that were eluted in isocratic with methanol-acetonitrile-water( 20 ∶ 20 ∶ 60) as the mobile phase. The excitation wavelength and the emission wavelength of fluorescence detector were maintained at 360 nm and 450 nm,respectively. The flow rate was 0. 8 m L·min~(-1),and the column temperature was 30 ℃ ． The sample was prepared using the immunoaffinity column,then the recovery was measured with 75. 47%-101. 8% with RSD values lower than 6. 7%. A total of 20 batches of Eupolyphaga Steleophaga samples were assayed. According to the Chinese Pharmacopoeia( 2015 edition,part 1),the aflatoxin B_1 limit should be less than 5 μg·kg~(-1),and the sum of aflatoxins( AFB_1,AFB2,AFG_1,AFG_2) should be less than 10 μg·kg-1. Therefore,the positive rate of the 20 samples was 50. 0%,and 7 batches of samples exceeded the standard,and the over-standard rate was as high as 70. 0%. Among them,aflatoxins B_1,B_2,G_1,G_2,M_1,and M_2 were detected in three batches( SD-1,AH-1,AH-3),and aflatoxins B_1,B2,G1,G2,and M1 were detected in one batch( AH-7). The results showed that the newly developed method in this work is suitable for the simultaneous determination of six aflatoxins in Eupolyphaga Steleophaga,and also suggested that it should be of high values to take the contamination with aflatoxins into concerns.