Determination of ochratoxin A in baby food by immunoaffinity column cleanup with liquid chromatography: interlaboratory study

An interlaboratory study funded by the European Commission, Standards, Measurement and Testing Programme (4th Framework Programme) was performed to evaluate the effectiveness of an immunoaffinity column cleanup liquid chromatographic (LC) method for the determination of ochratoxin A in baby food at a possible future European regulatory limit (0.1 ng/g). The test portion is extracted in a blender with tert-butyl methyl ether (chosen to avoid use of chloroform but shown to give equivalent extraction efficiency) after addition of 0.5 mol/L phosphoric acid-2 mol/L sodium chloride solution. The extract is centrifuged and redissolved in a mixture of phosphate buffered saline solution and methanol. After removal of lypophilic substances with hexane, the extract is applied to an immunoaffinity column containing antibodies specific to ochratoxin A. The column is washed with water to remove the interfering compounds and the purified ochratoxin A is eluted with methanol. The separation and determination of ochratoxin A is performed by reversed-phase LC and detected by fluorescence after postcolumn derivatization (PCD) with ammonia. Test materials (baby food infant formulae), both spiked and naturally contaminated with ochratoxin A, were sent to 13 laboratories in 8 different European countries. Test portions were spiked at a level of 0.085 ng/g ochratoxin A. The average recovery for the spiked blank baby food was 108%. Based on results for spiked samples (blind pairs at 0.085 ng/g) as well as naturally contaminated samples (blind pairs at levels between 0.05 and 0.22 ng/g) the relative standard deviation for repeatability (RSDr) ranged from 18-36%. The relative standard deviation for reproducibility (RSDR) ranged from 29-63% and HORRAT values of between 0.4 and 0.9 were obtained.     

Determination of ochratoxin A at parts-per-trillion levels in cereal products by immunoaffinity column cleanup and high-performance liquid chromatography/mass spectrometry

Ochratoxin A (OTA) is a toxic and potentially carcinogenic fungal toxin found in a variety of food commodities. A new sensitive method has been developed to quantify OTA in cereal products by reversed-phase liquid chromatography (LC) with mass spectrometric (MS) detection. Ochratoxin B was used as the internal standard. OTA was extracted from cereal products with acetonitrile-water, and the extract was diluted with a buffer; the diluted extract was cleaned up on an immunoaffinity column before LC/MS analysis. Two multiple-reaction monitoring transitions were used, one for quantification of OTA and one for confirmation of identity. The method was shown to be highly sensitive, with a low decision limit (CCalpha) of 0.012 microg/kg and a detection capability (CCbeta) of 0.021 microg/kg. Within-laboratory repeatability coefficient of variation values were 7.1, 3.7, and 3.1%, and the corresponding recoveries were 104, 106, and 103% for rice samples fortified with OTA at 0.05, 0.10, and 0.15 microg/kg, respectively. Method validation was performed according to the criteria of European Commission Decision 2002/657/EC. All criteria as presented in the Commission Decision were fulfilled. This method is the first fully validated method using immunoaffinity chromatography for cleanup and MS for detection in the analysis of cereals for OTA. The method was also successfully applied to cereal-derived products. The analytical results for determination of the OTA content of cereal products commercially available in Hong Kong are also reported.     

Determination of zearalenone in cereal grains, animal feed, and feed ingredients using immunoaffinity column chromatography and liquid chromatography: interlaboratory study

A method using immunoaffinity column chromatography (IAC) and liquid chromatography (LC) for determination of zearalenone in cereal grains, animal feed, and feed ingredients was collaboratively studied. The test portion is extracted by shaking with acetonitrile-water (90 + 10, v/v) and sodium chloride. The extract is diluted and applied to an immunoaffinity column, the column is washed with water or phosphate-buffered saline or methanol-water (30 + 70, v/v), and zearalenone is eluted with methanol. The eluate is evaporated, the residue is dissolved in mobile phase and analyzed by reversed-phase LC with fluorescence detection. The presence of zearalenone can be confirmed using an alternate excitation wavelength or diode array detection. Twenty samples were sent to 13 collaborators (8 in Europe, 2 in the United States, one in Japan, one in Uruguay, and one in Canada). Eighteen samples of naturally contaminated corn, barley, wheat, dried distillers grains, swine feed, and dairy feed were analyzed as blind duplicates, along with blank corn and wheat samples. The analyses were done in 2 sample sets with inclusion of a spiked wheat control sample (0.1 mg/kg) in each set. Spiked samples recoveries were 89-116%, and for the 18 naturally contaminated samples, RSDr values (within-laboratory repeatability) ranged from 6.67 to 12.1%, RSDR values (among-laboratory reproducibility) ranged from 12.5 to 19.7%, and HorRat values ranged from 0.61 to 0.90.     

Determination of zearalenone content in cereals and feedstuffs by immunoaffinity column coupled with liquid chromatography

The zearalenone content of maize, wheat, barley, swine feed, and poultry feed samples was determined by immunoaffinity column cleanup followed by liquid chromatography (IAC-LC). Samples were extracted in methanol-water (8 + 2, v/v) solution. The filtered extract was diluted with distilled water and applied to immunoaffinity columns. Zearalenone was eluted with methanol, dried by evaporation, and dissolved in acetonitrile-water (3 + 7, v/v). Zearalenone was separated by isocratic elution of acetonitrile-water (50 + 50, v/v) on reversed-phase C18 column. The quantitative analysis was performed by fluorescence detector and confirmation was based on the UV spectrum obtained by a diode array detector. The mean recovery rate of zearalenone was 82-97% (RSD, 1.4-4.1%) on the original (single-use) immunoaffinity columns. The limit of detection of zearalenone by fluorescence was 10 ng/g at a signal-to-noise ratio of 10:1 and 30 ng/g by spectral confirmation in UV. A good correlation was found (R2 = 0.89) between the results obtained by IAC-LC and by the official AOAC-LC method. The specificity of the method was increased by using fluorescence detection in parallel with UV detection. This method was applicable to the determination of zearalenone content in cereals and other kinds of feedstuffs. Reusability of immunoaffinity columns was examined by washing with water after sample elution and allowing columns to stand for 24 h at room temperature. The zearalenone recovery rate of the regenerated columns varied between 79 and 95% (RSD, 3.2-6.3%). Columns can be regenerated at least 3 times without altering their performance and without affecting the results of repeated determinations.     

Determination of zearalenone in barley, maize and wheat flour, polenta, and maize-based baby food by immunoaffinity column cleanup with liquid chromatography: interlaboratory study

An interlaboratory study was performed on behalf of the UK Food Standards Agency to evaluate the effectiveness of an affinity column cleanup liquid chromatography (LC) method for the determination of zearalenone (ZON) in a variety of cereals and cereal products at proposed European regulatory limits. The test portion is extracted with acetonitrile:water. The sample extract is filtered, diluted, and applied to an affinity column. The column is washed, and ZON is eluted with acetonitrile. ZON is quantified by reversed-phase LC with fluorescence detection. Barley, wheat and maize flours, polenta, and a maize-based baby food naturally contaminated, spiked, and blank (very low level) were sent to 28 collaborators in 9 European countries and 1 collaborator in New Zealand. Participants were asked to spike test portions of all samples at a ZON concentration equivalent to 100 microg/kg. Average recoveries ranged from 91-111%. Based on results for 4 artificially contaminated samples (blind duplicates) and 1 naturally contaminated sample (blind duplicate), the relative standard deviation for repeatability (RSDr) ranged from 6.9-35.8%, and the relative standard deviation for reproducibility (RSDR) ranged from 16.4-38.2%. The method showed acceptable within- and between-laboratory precision for all 5 matrixes, as evidenced by HorRat values <1.7.     

多功能柱净化-高效液相色谱法检测谷物中的玉米赤霉烯酮

建立了玉米和小麦中玉米赤霉烯酮（ZEN）的多功能柱净化-高效液相色谱检测方法。样品经乙腈-水混合溶剂（V（乙腈）：V（水）=84：16）提取,通过多功能净化柱（MFC）进行一次性净化,以Symmetry^R C18柱为分离柱,甲醇-水（V（甲醇）：V（水）=68：32）为流动相进行高效液相色谱分离和检测。玉米赤霉烯酮的质量浓度在0．01～4．0μg／mL范围内呈良好线性,相关系数为0．9996。检出限为0．04μg／g,在0、04—5．0mg／kg添加范围内的回收率为87．5％～98．6％,相对标准偏差为1．5％～8．3％。     

复合免疫亲和柱-高效液相色谱法同时测定谷物及其制品中9种真菌毒素

建立了复合免疫亲和柱-在线光化学衍生-高效液相色谱同时测定谷物及其制品中9种真菌毒素的检测方法。以乙腈-水（80：20,v/v）混合溶液提取样品中9种真菌毒素,提取液经自制真菌毒素复合免疫亲和柱净化,采用高效液相色谱进行分离,在线光化学衍生后进入荧光检测器测定,外标法定量。结果表明,9种真菌毒素在相应浓度范围内线性关系良好,相关系数均大于0.999;在低、中、高3个不同加标浓度下,9种真菌毒素的回收率均大于80%,相对标准偏差（RSD）为1.0%~5.6%;方法的检出限（LOD）为0.02~5.00 μg/kg,定量限（LOQ）为0.07~16.70 μg/kg。该方法具有重现性好、灵敏度高、结果准确的特点,适用于谷物及其制品中9种真菌毒素残留的分析检测。     

Determination of ochratoxin A in currants, raisins, sultanas, mixed dried fruit, and dried figs by immunoaffinity column cleanup with liquid chromatography: interlaboratory study

An interlaboratory study was performed on behalf of the Food Standards Agency to evaluate the effectiveness of an affinity column cleanup liquid chromatographic (LC) method for the determination of ochratoxin A in a variety of dried fruit at European regulatory limits. To ensure homogeneity before analysis, laboratory samples are normally slurried with water in the ratio of 5 parts fruit to 4 parts water, and test materials in this form were used in the study. The test portion was extracted with acidified methanol. The extract was filtered, diluted with phosphate-buffered saline, and applied to an affinity column. The column was washed and ochratoxin A was eluted with methanol. Ochratoxin A was quantified by reversed-phase LC. The use of post-column pH shift to enhance the fluorescence of ochratoxin A by the addition of 1.1 M ammonia solution to the column eluant is optional. Determination was by fluorescence. Currants, sultanas, raisins, figs, and mixed fruit (comprising dried pineapple, papaya, sultanas, prunes, dates, and banana chips), both naturally contaminated and blank (very low level), were sent to 24 collaborators in 7 European countries. Participants were asked to spike test portions of all test samples at a level equivalent to 5 ng/g ochratoxin A. Average recoveries ranged from 69 to 74%. Based on results for 5 naturally contaminated test samples (blind duplicates) the relative standard deviation for repeatability (RSDr) ranged from 4.9 to 8.7%, and the relative standard deviation for reproducibility (RSDR) ranged from 14 to 28%. The method showed acceptable within- and between-laboratory precision for all 5 matrixes, as evidenced by HORRAT values <1.3.     

Quantification of deoxynivalenol in wheat using an immunoaffinity column and liquid chromatography

A simple and accurate method to quantify the mycotoxin deoxynivalenol (DON) in wheat is described. The method uses immunoaffinity chromatography for DON isolation and liquid chromatography (LC) for toxin detection and quantification. Wheat samples are extracted in water, filtered twice and applied to an immunoaffinity column. Following a water wash, DON is eluted from the column with methanol and injected onto an LC system with a UV detector for quantification. Test performance was evaluated in terms of antibody specificity, limit of detection, percentage recovery, precision, column capacity, assay linearity and comparison with the GC-electron-capture detection (ECD) method of Tacke and Casper. Specificity of the immunoaffinity column cleanup procedure was confirmed with only DON (>80%) and its 15-C derivatives (40-50%) being recognized by the antibody while 3-C DON derivatives, nivalenol, T-2 and fusarenon-X did not bind. The limit of detection is at least 0.10 microg/g. Percentage recovery for the entire assay range averages 90% with an average relative standard deviation of 8.3%. Naturally contaminated samples showed comparable precision. Column capacity was determined to be 3.3 microg. The assay showed a high degree of linearity (r2=0.999) and an optimum assay range of 0.10 to 10.0 microg/g. Comparative analysis of 28 naturally or artificially contaminated wheat samples using DONtest-HPLC and the GC-ECD method of Tacke and Casper showed that DONtest-HPLC is a statistically significant predictor of the GC-ECD method (r2=0.982).     

Determination of fumonisins B1 and B2 in corn and corn flakes by liquid chromatography with immunoaffinity column cleanup: collaborative study.

A liquid chromatographic (LC) method for the determination of fumonisins B1 (FB1) and B2 (FB2) in corn and corn flakes was collaboratively studied by 23 laboratories, which analyzed 5 blind duplicate pairs of each matrix to establish the accuracy, repeatability, and reproducibility characteristics of the method. Fumonisin levels in the corn ranged from <0.05 (blank) to 1.41 microg/g for FB1 and from <0.05 to 0.56 microg/g for FB2, whereas in the corn flakes they ranged from <0.05 to 1.05 microg/g for FB1 and from <0.05 to 0.46 microg/g for FB2. The method involved double extraction with acetonitrile-methanol-water (25 + 25 + 50), cleanup through an immunoaffinity column, and LC determination of the fumonisins after derivatization with o-phthaldialdehyde. Relative standard deviations for the within-laboratory repeatability (RSDr) of the corn analyses ranged from 19 to 24% for FB1 and from 19 to 27% for FB2; for the corn flakes analyses, RSDr ranged from 9 to 21 % for FB1 and from 8 to 22% for FB2. Relative standard deviations for the between-laboratories reproducibility (RSDR) of the corn analyses ranged from 22 to 28% for FB1 and from 22 to 30% for the FB2; for corn flakes analyses, RSDR ranged from 27 to 32% for FB1 and from 26 to 35% for FB2. Mean recoveries of FB1 and FB2 from corn spiked with FB1 at 0.80 microg/g and with FB2 at 0.40 microg/g were 76 and 72%, respectively; for corn flakes spiked at the same levels recoveries were 110 and 97% for FB1 and FB2, respectively. HORRAT ratios for the analyses of corn ranged from 1.44 to 1.53 for FB1 and from 0.96 to 1.48 for FB2, whereas for corn flakes they ranged from 1.60 to 1.82 for FB1 and from 1.39 to 1.68 for FB2.     

Immunoaffinity column cleanup with liquid chromatography for determination of aflatoxin B1 in corn samples: interlaboratory study

An interlaboratory study was conducted to evaluate the effectiveness of an immunoaffinity column cleanup liquid chromatography (LC) method for the determination of aflatoxin B1 levels in corn samples, enforced by European Union legislation. A test portion was extracted with methanol-water (80 + 20); the extract was filtered, diluted with phosphate-buffered saline solution, filtered on a microfiber glass filter, and applied to an immunoaffinity column. The column was washed with deionized water to remove interfering compounds, and the purified aflatoxin B1 was eluted with methanol. Aflatoxin B1 was separated and determined by reversed-phase LC with fluorescence detection after either pre- or postcolumn derivatization. Precolumn derivatization was achieved by generating the trifluoroacetic acid derivative, used by 8 laboratories. The postcolumn derivatization was achieved either with pyridinium hydrobromide perbromide, used by 16 laboratories, or with an electrochemical cell by the addition of bromide to the mobile phase, used by 5 laboratories. The derivatization techniques used were not significantly different when compared by the Student's t-test; the method was statistically evaluated for all the laboratories. Five corn sample materials, both spiked and naturally contaminated, were sent to 29 laboratories (22 Italian and 7 European). Test portions were spiked with aflatoxin B1 at levels of 2.00 and 5.00 ng/g. The mean values for recovery were 82% for the low level and 84% for the high contamination level. Based on results for spiked samples (blind pairs at 2 levels) as well as naturally contaminated samples (blind pairs at 3 levels), the values for relative standard deviation for repeatability (RSDr) ranged from 9.9 to 28.7%. The values for relative standard deviation for reproducibility (RSDR) ranged from 18.6 to 36.8%. The method demonstrated acceptable within- and between-laboratory precision for this matrix, as evidenced by the HorRat values.     

Determination of aflatoxins in Chinese medicinal herbs by high-performance liquid chromatography using immunoaffinity column cleanup Improvement of recovery

Although analytical methods are available for the determination of aflatoxins in medicinal herbs, none of them can be applied satisfactorily to all sample matrices. The difficulty arises from the complex chemical composition of the herbs. Recovery is generally low by using immunoaffinity column cleanup due to the acidity of the water extractive leading to a weakened binding affinity. As a solvent for dilution and neutralization, phosphate buffer saline is useful for certain herbs but not for others that have high acidity. The problem can be solved by using 0.1 M phosphate buffer, which has a higher buffering capacity and eliminates sodium chloride. The modified method was validated by the analysis of a certified reference material and shown to be useful for the determination of aflatoxins in herbal samples of high acidity.     

Determination of zearalenone in botanical dietary supplements, soybeans, grains, and grain products by immunoaffinity column cleanup and liquid chromatography: single-laboratory validation

The accuracy, repeatability, and reproducibility characteristics of a method for measuring levels of zearalenone (ZON) in botanical root products, soybeans, grains, and grain products were determined by an AOAC single-laboratory validation procedure. Replicates of 10 test portions of each powdered root product (black cohosh, ginger, ginseng), brown rice flour, brown rice grain, oat flour, rice bran, soybeans, and wheat flour at each spiking level (ZON at 0, 50, 100, and 200 microg/kg) were analyzed on 3 separate days. Test samples were extracted with methanol-water (75 + 25, v/v). The extracts were centrifuged or filtered, diluted with phosphate-buffered saline (PBS) containing 0.5% Tween 20, and filtered; the filtrates were applied to an immunoaffinity column containing antibodies specific for ZON. After the column was washed with methanol-PBS (15 + 85, v/v) containing 0.5% Tween 20 and then with water, the toxin was eluted from the column with methanol, and the eluate was diluted with water. The eluate containing the toxin was then subjected to RPLC with fluorescence detection. All commodities that were found to contain ZON at < 10 microg/kg were used for the recovery study. The average within-day and between-days recoveries of ZON added at levels of 50-200 microg/kg ranged from 82 to 88% and from 81 to 84%, respectively, for all test commodities. The total average of within- and between-day SD and RSDr values for all test commodities ranged from 2.5 to 7.3 microg/kg and from 4.6 to 6.2%, respectively. HorRat values were <1.3 for all matrixes examined. The tested method was found to be acceptable for the matrixes examined.     

Determination of aflatoxin B1 in baby food (infant formula) by immunoaffinity column cleanup liquid chromatography with postcolumn bromination: collaborative study

A collaborative study was conducted to evaluate the effectiveness of an immunoaffinity column cleanup liquid chromatography (LC) method for determination of aflatoxin B, in a milk powder based infant formula at a possible future European regulatory limit (0.1 ng/g). The test portion was extracted with methanol-water (8 + 2 [v + v]), filtered, diluted with water, and applied to an immunoaffinity column. The column was washed with water to remove interfering compounds, and the purified aflatoxin B1 was eluted with methanol. The separation and determination of the aflatoxin B1 was performed by reversed-phase LC and detected by fluorescence after postcolumn derivatization (PCD) involving bromination. PCD was achieved with either pyridinum hydrobromide perbromide (PBPB) or an electrochemical (Kobra) cell by addition of bromide to the mobile phase. The baby food (infant formula) test samples, both spiked and naturally contaminated with aflatoxin B1, were sent to 14 laboratories in 13 different European countries. Test portions were spiked at levels of 0.1 and 0.2 ng/g for aflatoxin B1. Recoveries ranged from 101 to 92%. Based on results for spiked test samples (blind pairs at 2 levels) and naturally contaminated test samples (blind pairs at 3 levels), the relative standard deviation for repeatability (RSDr) ranged from 3.5 to 14%. The relative standard deviation for reproducibility (RSDR) ranged from 9 to 23%. Nine participants used PBPB derivatization, and     

Rapid determination of ochratoxin A in cereals and cereal products by liquid chromatography

A new method based on extraction with octylsilica (C8) followed by liquid chromatography coupled with fluorescence detection (LC-FLD) was studied to determine ochratoxin A (OTA) from cereals and cereal products. Optimization of different parameters, such as type and amount of solid phase, type and volume of eluent and amount of sample were carried out. Recovery of OTA from rice samples spiked at 10 ng/g level was of 86% with relative standard deviation of 5%. The limits of detection and quantification of the proposed method were 0.25 and 0.75 ng/g, respectively. Furthermore, LC-FLD after of OTA methylation and liquid chromatography coupled to mass spectrometry with an electrospray interface were used for confirmation of OTA in all studied samples. The proposed method was applied to 62 samples of cereals and cereal products and the presence of OTA was found in seven samples.     

Immunoaffinity column cleanup with liquid chromatography using post-column bromination for determination of aflatoxins in hazelnut paste: interlaboratory study

An interlaboratory study was conducted to evaluate the effectiveness of an immunoaffinity column cleanup liquid chromatography (LC) method for determination of aflatoxin B1 and total aflatoxins in hazelnut paste at European regulatory limits. The test portion was extracted with methanol-water (6 + 4). The extract was filtered, diluted with phosphate-buffered saline (PBS) solution to a specified solvent concentration, and applied to an immunoaffinity column containing antibodies specific to aflatoxins. The aflatoxins were removed from the immunoaffinity column with methanol, and then quantified by reversed-phase LC with post-column derivatization (PCD) involving bromination. The PCD was achieved with electrochemically generated bromine (Kobra Cell) followed by fluorescence detection (except for one participant who used pyridinum hydrobromide perbromide for bromination). Hazelnut paste, both naturally contaminated with aflatoxins and blank (<0.1 ng/g) for spiking by participants with aflatoxins, was sent to 14 collaborators in Belgium, The Netherlands, Spain, Turkey, the United Kingdom, and the United States. Test portions were spiked at levels of 4.0 and 10.0 ng/g for total aflatoxins by participants using supplied total aflatoxins standards. Recoveries for total aflatoxins and aflatoxin B1 averaged from 86 to 89%. Based on results for naturally contaminated samples (blind duplicates at 3 levels ranging from 4.0 to 11.8 ng/g total aflatoxins), the relative standard deviation for repeatability (RSDr) ranged from 2.3 to 3.4% for total aflatoxins and from 2.2 to 3.2% for aflatoxin B1. The relative standard deviation for reproducibility (RSD(R)) ranged from 6.1 to 7.0% for total aflatoxins and from 7.3 to 7.8% for aflatoxin B1. The method showed exceptionally good within-laboratory and between-laboratory precision for hazelnut paste, as evidenced by HORRAT values, which in all cases were significantly below target levels, the low levels of determination for both aflatoxin B1 and total aflatoxins.     

Determination of halofuginone in eggs by liquid chromatography/tandem mass spectrometry after cleanup with immunoaffinity chromatography

A sensitive and very selective high-performance liquid chromatography/tandem mass spectrometric (LC/MS/MS) method for the detection of halofuginone in whole egg has been developed. After deproteinisation with acetonitrile and evaporation of the organic solvent, halofuginone was further isolated by applying immunoaffinity chromatography. The concentrated eluent was injected into the LC/MS/MS system on a C18 column. The precursor ion ([M+H]+) produced by positive electrospray ionisation was selected for fragmentation with argon. Validation parameters such as recovery, linearity and repeatability, decision limit (CCalpha) and detection capability (CCbeta) were determined.     

Determination of aflatoxins and ochratoxin A in ginseng and other botanical roots by immunoaffinity column cleanup and liquid chromatography with fluorescence detection

Mycotoxins are toxic secondary metabolites produced by certain molds and are common contaminants of many important food crops, such as grains, nuts, and spices. Some mycotoxins are found in fruits, vegetables, and botanical roots. These contaminants have a broad range of toxic effects, including carcinogenicity, immunotoxicity, neurotoxicity, and reproductive and developmental toxicity. The public health concerns related to both acute and chronic effects of mycotoxins in animals have prompted more than 100 countries to establish regulatory limits for some of the well-known mycotoxins, such as the aflatoxins (AFL). Our research focused on method development for 2 of these toxins, AFL and ochratoxin A (OTA), in ginseng and other selected botanical roots. Methods using an immunoaffinity column (IAC) cleanup, liquid chromatographic separation, and fluorescence detection were modified and evaluated. Two types of IAC cleanup were evaluated: IAC for AFL, and IAC for both AFL and OTA. Three derivatization techniques to enhance the fluorescence of the AFL were compared: precolumn trifluoroacetic acid, postcolumn bromination, and postcolumn ultraviolet irradiation. No derivatization was needed for OTA. Results for AFL using the single analyte IAC cleanup and the 3 derivatization techniques were all comparable for ginseng and for other roots such as ginger, licorice, and kava-kava. Recoveries of added AFL for ginseng at levels from 2 to 16 ng/g were about 80%. Using IAC cleanup for both AFL and OTA recoveries of added AFL for ginseng at 4-16 ng/g were about 70%, and for ginger, licorice, and kava-kava were about 60%. Recoveries of added OTA for ginseng, ginger, and echinacea at 4 ng/g were about 55%.     

Multiresidue analysis of avermectins in bovine liver by immunoaffinity column cleanup procedure and liquid chromatography with fluorescence detector

A multiresidue liquid chromatography (LC) method was developed to detect avermectin, ivermectin, doramectin, and eprinomectin simultaneously in bovine liver. The extracted samples were cleaned up by an immunoaffinity column, which was prepared by coupling anti-avermectin polyclonal antibody with CNBr-activated Sepharose 4B. The dynamic column capacities of avermectin, ivermectin, doramectin, and eprinomectin were 3531, 3542, 3543, and 3284 nglmL gel, respectively. The eluate was evaporated to dryness, and residues were derivatized and determined by LC with fluorescence detector set at 365 nm excitation and 465 nm emission wavelengths. Recoveries ranged from 79.3 to 115.9% with coefficients of variation of 1.1-19.4% when avermectin, ivermectin, doramectin, and eprinomectin were spiked at levels of 5-100 ng/g. The limit of quantitation of the method was 2 ng/g for each drug.