Determination of narasin and monensin in bovine, swine, and chicken tissues by liquid chromatography with tandem mass spectrometry: first action 2011.24

The single-laboratory validation (SLV) of an LC-MS/MS method for determination and confirmation of two ionophores, narasin and monensin, in animal tissues is described. The data demonstrated linearity of matrix-matched calibration curves using a weighted (1/x) regression and selectivity of the method for narasin and monensin in the presence of lasalocid, salinomycin, maduramycin, nicarbazin, and sulfadiazine. Recoveries varied from 86.2 to 103.5% for narasin and 89.1 to 105.1% for monensin. Intertrial repeatability precision [relative standard deviation of repeatability (RSDr)] varied from 3.9 to 13.8% for narasin and 3.3 to 16.3% for monensin in fortified tissue. Precision of the method was verified in incurred tissues. The LOQ of the method was validated and ranged from 0.45 ng/g in milk, to 4.0 ng/g in chicken fat, but was 0.75 ng/g for most tissues. Two confirmatory ions for each analyte were examined across all matrixes, resulting in estimated false-negative rates of 0.00% (95% confidence interval of 0.00-0.68%) for monensin ions (540 samples) compared to the U.S. and European Union (EU) acceptance criteria. The confirmatory ions for narasin demonstrated 0.00% false-negative rates (95% confidence interval of 0.00-0.58%) when compared to either the U.S. or EU criteria in 630 samples. The method was robust when small changes in method parameters were made and stability of fortified tissues, extracts, and calibration solutions were estimated. The data satisfy the requirements of the AOAC Stakeholder Panel on Veterinary Drug Residue for SLV studies, and the method was adopted Official Methods of Analysis First Action 2011.24 by the AOAC Expert Review Panel on Veterinary Drug Residues.     

Multilaboratory trial for determination of ceftiofur residues in bovine and swine kidney and muscle,and bovine milk

A multilaboratory trial for determining ceftiofur-related residues in bovine and swine kidney and muscle, and bovine milk was conducted following regulatory guidelines of the U.S. Food and Drug Administration, Center for Veterinary Medicine. The methods convert all desfuroylceftiofur-related residues containing the intact beta-lactam ring to desfuroylceftiofur acetamide to establish ceftiofur residues in tissues. Four laboratories analyzed 5 sets of samples for each tissue. Each sample set consisted of a control/blank sample and 3 control samples fortified with ceftiofur at 0.5 Rm, Rm, and 2 Rm, respectively, where Rm is the U.S. tolerance assigned for ceftiofur residue in each tissue/matrix: 0.100 microg/mL for milk, 8.0 microg/g for kidney (both species), 1.0 microg/g for bovine muscle, and 2.0 microg/g for swine muscle. Each sample set also contained 2 samples of incurred-residue tissues (one > Rm and one < Rm) from animals treated with ceftiofur hydrochloride. All laboratories completed the method trial after a familiarization phase and test of system suitability in which they demonstrated > 80% recovery in pretrial fortified test samples. Results showed that the methods met all acceptable performance criteria for recovery, accuracy, and precision. Although sample preparation was easy, solid-phase extraction cartridge performance must be carefully evaluated before samples are processed. The liquid chromatography detection system was easily set up; however, the elution profile may require slight modifications. The procedures could clearly differentiate between violative (> Rm) and nonviolative (< Rm) ceftiofur residues. Participating laboratories found the procedures suitable for ceftiofur residue determination.     

Determination of calcium, copper, iron, magnesium, manganese, potassium, phosphorus, sodium, and zinc in fortified food products by microwave digestion and inductively coupled plasma-optical emission spectrometry: single-laboratory validation and ring trial

A single-laboratory validation (SLV) and a ring trial (RT) were undertaken to determine nine nutritional elements in food products by inductively coupled plasma-optical emission spectrometry in order to modernize AOAC Official Method 984.27. The improvements involved extension of the scope to all food matrixes (including infant formula), optimized microwave digestion, selected analytical lines, internal standardization, and ion buffering. Simultaneous determination of nine elements (calcium, copper, iron, potassium, magnesium, manganese, sodium, phosphorus, and zinc) was made in food products. Sample digestion was performed through wet digestion of food samples by microwave technology with either closed- or open-vessel systems. Validation was performed to characterize the method for selectivity, sensitivity, linearity, accuracy, precision, recovery, ruggedness, and uncertainty. The robustness and efficiency of this method was proven through a successful RT using experienced independent food industry laboratories. Performance characteristics are reported for 13 certified and in-house reference materials, populating the AOAC triangle food sectors, which fulfilled AOAC criteria and recommendations for accuracy (trueness, recovery, and z-scores) and precision (repeatability and reproducibility RSD, and HorRat values) regarding SLVs and RTs. This multielemental method is cost-efficient, time-saving, accurate, and fit-for-purpose according to ISO 17025 Norm and AOAC acceptability criteria, and is proposed as an extended updated version of AOAC Official Method 984.27 for fortified food products, including infant formula.     

Reversed-phase high-performance liquid chromatographic determination of dexamethasone in bovine tissues.

A sensitive and selective high-performance liquid chromatographic procedure is described for the determination of the synthetic corticosteroid dexamethasone (DXM), in bovine muscle, kidney, liver and fat tissues, using methylprednisolone as the internal standard. Following extraction with ethyl acetate (muscle, kidney and liver) or diethyl ether (fat) and clean-up of the tissue extract, the drug residue was isolated using a C18 solid-phase extraction column. Separation of DXM was achieved by reversed-phase high-performance liquid chromatography with ultraviolet detection at 254 nm. By using this procedure, DXM levels as low as 0.01 mg kg-1 can be detected in muscle, kidney, liver and fat.     

Simultaneous determination of vitamins D2 and D3 by LC-MS/MS in infant formula and adult nutritionals: First Action 2011.13

During the "Standards Development and International Harmonization: AOAC INTERNATIONAL Mid-Year Meeting" held on June 29, 2011, an Expert Review Panel (ERP) on behalf of AOAC INTERNATIONAL adopted the method "Simultaneous Determination of Vitamins D2 and D3 by LC-MS/MS in Infant Formula and Adult Nutritionals" as an AOAC Official First Action method. Vitamins D2 and D3 are extracted from the sample using pentane-ether; the extract is collected and dried under nitrogen. Vitamin D is separated from interfering compounds using UPLC, and quantitated using tandem mass spectrometry (MS/MS). Preliminary data showed the intermediate precision ranged from 3.34-8.05% and an accuracy range of 98.5-111% over the samples tested for vitamin D3. For vitamin D2, the intermediate precision ranged from 2.37-5.45% and accuracy ranged from 96.4-104% over the four matrixes evaluated. The analytical range for the method is bounded by the concentrations of the working standards, 21-270 ng/mL, and is equivalent to 0.168-2.16 mcg/100 g in ready-to-feed product. The practical method quantitation limit is 0.168 mcg/100 g product with method detection limit of 60 ng/100 g product. The ERP reviewed the data and determined that the performance characteristics of the method met the standard method performance requirements, and therefore the method was granted First Action status.     

Application of ion-exchange cartridge clean-up in food analysis IV. Confirmatory assay of benzylpenicillin, phenoxymethylpenicillin, oxacillin, cloxacillin, nafcillin and dicloxacillin, in bovine tissues by liquid chromatography-electrospray ionization tandem mass spectrometry

A multiresidue analytical method was developed for the confirmation of benzylpenicillin (PCG), phenoxymethylpenicillin (PCV), oxacillin (MPIPC), cloxacillin (MCIPC), nafcillin (NFPC) and dicloxacillin (MDIPC) in bovine tissues using electrospray ionization liquid chromatography-tandem mass spectrometry (LC-ESI-MS-MS) with a product ion scan mode. All penicillins gave [M-H]-, [M-H-CO2]- and [M-H-141]- as the product ion, when [M-H]- was selected as the precursor ion. Combination of an ion-exchange cartridge clean-up and the LC-ESI-MS-MS method can reliably identify all of these penicillins fortified at a concentration of 0.05 mg/kg in bovine tissues, including liver, kidney and muscle. The limits of confirmation satisfy the maximum residue limits for each of the penicillins established by the World Health Organization, US Food and Drug Administration, European Union and Japan.     

Determination of tilmicosin residues in chicken, cattle, swine, and sheep tissues by liquid chromatography

A method was developed and validated for determination and quantitation of tilmicosin residues in swine, cattle, and sheep edible tissues, as well as chicken fat, skin, and muscle over a concentration range of 0.025 microg/g-20 microg/g. For chicken kidney and liver, the method was validated over a range of 0.060 microg/g-20 microg/g. The tissue sample was extracted with methanol and a C18 cartridge was used for solid-phase extraction cleanup. A reversed-phase gradient liquid chromatographic method with detection at 280 nm was used to separate the tilmicosin from matrix components in 30 min run time. The limit of quantitation (LOQ) of the method was 0.025 microg/g for all tested tissues except chicken kidney and liver, for which the LOQ was 0.06 microg/g. Average recoveries for tissue samples ranged from 73 to 98%. Relative standard deviation values ranged from 0.6 to 14.7%.     

Determination of sulfamethazine in swine and cattle feed by reversed-phase liquid chromatography with post-column derivatization: pre-collaborative study

In-house validation of a liquid chromatographic method for determination of sulfamethazine in swine and cattle feed was performed to verify that the method was ready for collaborative study under AOAC INTERNATIONAL guidelines. In this method, sulfamerazine is added during the extraction procedure and is used as an internal standard to correct for variable recovery of sulfamethazine from a variety of swine and cattle feed matrixes. The determinative step involves the use of post-column derivatization with dimethylaminobenzaldehyde which reacts with the primary amine group on the sulfonamides. Detection is at 450 nm, a wavelength at which most co-extracted matrix materials and other feed additives do not absorb light. The results indicate that the method recovery, precision, and ruggedness meet normal criteria to be ready for a collaborative study. Fortification experiments over a range of sulfamethazine concentrations from 0.006 to 0.26% showed an overall recovery relative to the internal standard of 100 +/- 2%. These studies include both swine and cattle feed matrixes. The mean recovery in the analysis of 3 beef cattle experimental feeds was 98.9%. The method results agreed with the AOAC INTERNATIONAL Official Method for colorimetric analysis of swine feed. Method precision was excellent during in-house validation studies, with coefficients of variation (CVs) ranging from about 0.5 to 3%. The method ruggedness was verified with an overall CV of 3.5%.     

Liquid chromatographic determination of fenbendazole residues in pig tissues after treatment with medicated feed.

Fenbendazole (FBZ) is an anthelmintic widely used in farm animals to treat parasitic infestations. In pigs, it is administered in the food. The aim of this study was to validate an analytical method for the determination of FBZ and its metabolites in pig tissues. This method is based on oxidation of FBZ and its sulfoxide metabolite to the sulfone metabolite (FBZSO2). The limit of quantitation for this method is 20 ng FBZSO2/g for all tissues. The maximum residue limits (MRLs) established for FBZ and its metabolites in pig tissues are 50 ng/g for muscle, fat, and kidney and 500 ng/g for liver. This method is based on a liquid-liquid extraction followed by an oxidation with peracetic acid and a cleanup procedure based on 2 liquid-liquid extractions. Determination is achieved by high-performance liquid chromatography with ultraviolet detection. The present method is adjusted to the MRL established for FBZ and its metabolite residues. The analysis of the residues shows that after 72 h posttreatment, no FBZSO2 was detected in muscle, fat, and kidney and that liver levels were below the MRL.     

Determination and quantification of sulfadiazine and trimethoprim in swine tissues using liquid chromatography with ultraviolet and mass spectrometric detection

High-performance liquid chromatographic procedures with ultraviolet detection were developed for the quantitative determination of sulfadiazine (SDA) and trimethoprim (TMP) in swine tissues (kidney, liver, muscle, fat and fat + skin). In addition, high-performance liquid chromatography with atmospheric pressure chemical ionization mass spectrometry was used for the confirmation of the identity of the analytes of interest. Chromatographic separation was achieved on a Spherisorb ODS-2 column (250 x 4.6 mm id, dp 5 microns). The mobile phase for SDA analysis consisted of 1% acetic acid in water-acetonitrile (85 + 15, v/v). For TMP analysis a 80 + 15 + 5 (v/v/v) mixture of 0.25% triethylammonium acetate in water, acetonitrile and methanol was used as the eluent. Sulfamerazine and ormethoprim were used as the internal standards for SDA and TMP analysis, respectively. For the isolation of the compounds of interest from biological samples, a liquid-liquid extraction with acetone and ethyl acetate, followed by a clean-up using a solid-phase extraction column (aminopropyl and benzenesulfonic acid for SDA, benzenesulfonic acid for TMP) was performed. Calibration graphs were prepared for all tissues and linearity was achieved over the concentration ranges tested (50-1000 ng g-1 for SDA, r > or = 0.9979; 25-500 ng g-1 for TMP, r > or = 0.9994). The method was validated at the maximum residue level (MRL, 100 ng g-1 for SDA and 50 ng g-1 for TMP), at half the MRL and at double the MRL for both SDA and TMP. The accuracy and precision (expressed as the within-day repeatability) were found to be within the required ranges for each specific concentration. The quantification limits were 50 ng g-1 for SDA and 25 ng g-1 for TMP. The limits of detection were below one half the MRLs. Both methods were selective for the determination of SDA and TMP. Biological samples (kidney, liver, muscle, fat and fat + skin) from pigs that received a commercial SDA-TMP preparation with the feed for five consecutive days (dose rate: 25 mg SDA and 5 mg TMP kg body weight-1 day-1) were analyzed using the described methods. The quantitative results were used to calculate a withdrawal time (12 days) to reach residue levels below the respective MRLs. This calculation was performed according to the recommendations of the European Agency for the Evaluation of Medicinal Products (EMEA/CVMP/036/95).     

Determination of vitamin A (retinol) in infant formula and adult nutritionals by liquid chromatography: First Action 2011.15

During the "Standards Development and International Harmonization: AOAC INTERNATIONAL Mid-Year Meeting," held on June 29, 2011, an Expert Review Panel (ERP) reviewed the method for the "Determination of Vitamins A (Retinol) and E (alpha-Tocopherol) in Foods by Liquid Chromatography: Collaborative Study," published by Jonathan W. DeVries and Karlene R. Silvera in J. AOAC Int. in 2002. After evaluation of the original validation data, an ERP agreed in June 2011 that the method meets standard method performance requirements (SMPRs) for vitamin A, as articulated by the Stakeholder Panel on Infant Formula and Adult Nutritionals. The ERP granted the method First Action status, applicable to determining vitamin A in ready-to-eat infant and adult nutritional formula. In an effort to achieve Final Action status, it was recommended that additional information be generated for different types of infant and adult nutritional formula matrixes at varied concentration levels as indicated in the vitamin A (retinol) SMPR. Existing AOAC LC methods are suited for specific vitamin A analytical applications. The original method differs from existing methods in that it can be used to assay samples in all nine sectors of the food matrix. One sector of the food matrix was powdered infant formula and gave support for the First Action approval for vitamin A in infant and adult nutritional formula. In this method, standards and test samples are saponified in basic ethanol-water solution, neutralized, and diluted, converting fats to fatty acids and retinol esters to retinol. Retinol is quantitated by an LC method, using UV detection at 313 or 328 nm for retinol. Vitamin concentration is calculated by comparison of the peak heights or peak areas of retinol in test samples with those of standards.     

Determination of gentamicin in swine and calf tissues by high-performance liquid chromatography combined with electrospray ionization mass spectrometry

Gentamicin is a broad-spectrum aminoglycoside antibiotic widely used in veterinary medicine for the treatment of serious infections. The purpose of this study was to develop and validate a method to determine gentamicin residues in edible tissues of swine and calf. Extraction of gentamicin was performed using a liquid extraction with phosphate buffer containing trichloroacetic acid, followed by a solid-phase clean-up procedure on a CBA weak cation-exchange column. Tobramycin was used as the internal standard. After drying of the eluate, the residue was redissolved and further analyzed by reversed-phase liquid chromatography/electrospray ionization tandem mass spectrometry (MS/MS). Chromatographic separation of the internal standard tobramycin and the gentamicin components was achieved on a Nucleosil (5 microm) column using a mixture of 10 mM pentafluoropropionic acid in water and acetonitrile as the mobile phase. The gentamicin components C1a, C2 + C2a and C1 could be identified with the MS/MS detection, and subsequently quantified. The method was validated according to the requirements of the EC at the maximum residue limit (MRL) (100 ng g(-1) for muscle and fat, 200 ng g(-1) for liver and 1000 ng g(-1) for kidney), half the MRL and double the MRL levels. Calibration graphs were prepared for all tissues and good linearity was achieved over the concentration ranges tested (r > 0.99 and goodness of fit <10%). Limits of quantification of 25.0 ng g(-1) were obtained for the determination of gentamicin in muscle, fat, liver and kidney tissues of swine and calf, which correspond in all cases to at least half the MRLs. Limits of detection ranged between 0.5 and 2.5 ng g(-1) for the tissues. The within-day and between-day precisions (RSD) and the results for accuracy fell within the ranges specified. The method was successfully used for the determination of gentamicin in tissue samples of swines and calves medicated with gentamicin by intramuscular injection.     

Multiresidue method for simultaneous determination of ten quinolone antibacterial residues in multimatrix/multispecies animal tissues by liquid chromatography with fluorescence detection: single laboratory validation study

Quinolone antibacterials are veterinary drugs authorized for use in food animal production. The analysis of residual amounts of drugs in food from animal origin is important for quality control of products for consumers. For this purpose, Maximum Residue Limits (MRLs) have been set up by a European Union Council Regulation on Veterinary Drug Residues (No. 90/2377/EEC and subsequent), and 8 quinolones received MRLs at concentration levels depending on both the matrix and the animal species of interest. A method was developed for screening and confirming 10 quinolone residues (ciprofloxacin, danofloxacin, difloxacin, enrofloxacin, flumequine, marbofloxacin, nalidixic acid, norfloxacin, oxolinic acid, sarafloxacin) in a wide variety of matrixes of different animal species. It involves extraction of the residues from the biological tissues/fluids by acidic aqueous solution, centrifugation and filtration prior to injection on a C18 narrow-bore column, and detection through a 3-step-mode fluorescence detector. The method was validated during a 2-week study for a set of 8 species-matrixes (i.e., bovine raw milk, bovine muscle, porcine muscle, porcine kidney, porcine liver, fish flesh and skin, poultry muscle, whole egg). Residues were quantified down to 15 microg/kg with limits of detection and quantitation ranging from 4 to 11 and 13 to 36 microg/kg, respectively, which are sufficient compared to the wide range of MRLs set for these substances (from 30 microg/kg for danofloxacin in milk to 1900 microg/kg for difloxacin in poultry liver). The limit of performance of the method in terms of CCalpha and CCbeta, the critical concentrations stated in the Decision No. 2002/657/EC and the ISO Standard No. 11843, has been calculated for the authorized (MRL) substances but only estimated in the case of the nonauthorized (non-MRL) substances.     

Confirmatory method for macrolide residues in bovine tissues by micro-liquid chromatography-tandem mass spectrometry

A new confirmatory method for three macrolides (tylosin, tilmicosin and erythromycin) in bovine muscle, liver and kidney by micro-LC-MS-MS using an atmospheric pressure ionisation source and an ionspray interface has been developed. Roxithromycin was used as internal standard. The molecular related ions, [M+2H]2+, at m/z 435 for tilmicosin, and [M+H]+, at m/z 734 and 916 for erythromycin and tylosin, respectively, were the precursor ions for collision-induced-dissociation and two diagnostic product ions for each macrolide were identified for the unambiguous confirmation by selected reaction monitoring LC-MS-MS. Precision values (relative standard deviations) were all below 14.9%, whereas the overall accuracy (relative error) ranged from -17.7 to -9.8% for tylosin, from -17.5 to -10.7% for tilmicosin and from -19.6 to -13.7% for erythromycin, in all the investigated bovine tissues. The limits of quantification were 30 (muscle) or 40 (liver, kidney) microg kg(-1), 20 (muscle) or 150 (liver, kidney) microg kg(-1), 50 (muscle, liver) or 80 (kidney) microg kg(-1), 20 (muscle, liver) or 50 (kidney) microg kg(-1) for tylosin, tilmicosin, erytromycin and roxithromycin, respectively.     

Determination of sulfonamide residues in the tissues of food animals using automated precolumn derivatization and liquid chromatography with fluorescence detection

A liquid chromatographic method for the determination of sulfachloropyridazine, sulfadiazine, sulfadimethoxine, sulfadoxine, sulfaethoxypyridazine, sulfamethazine, sulfaquinoxaline, and sulfathiazole residues in the muscle, liver, and kidney of food animals using sulfapyridine as internal standard is reported. Tissues are extracted using a modified version of AOAC Official Method 983.31 (Sulfonamide Residues in Animal Tissues). The sample extract is reconstituted in pH 3.0 buffer-acetonitrile (60 + 40) and filtered into an autosampler vial. Using a programmable autosampler of a liquid chromatograph, a portion of the sample is derivatized precolumn with fluorescamine. The sulfonamide derivatives are separated by liquid chromatography using a C18 column with a mobile phase of 0.02M phosphoric acid-acetonitrile (60.5 + 39.5) and detected by fluorescence (excitation, 405 nm; emission, 495 nm). The method was applied to swine and cattle muscle, liver, and kidney; sheep and horse muscle and kidney; and chicken muscle and liver. The mean values for samples fortified with sulfonamides at levels between 0.05 and 0.2 microg/g agreed within 96-99% of spiked levels, with coefficients of variation ranging from 4-10%. The limit of detection (LOD) for all sulfonamides was 0.01 microg/g, with the exception of sulfaquinoxaline, for which the LOD was 0.015 microg/g.     

Residue depletion of valnemulin in swine tissues after oral administration

The depletion profile of valnemulin (VLM) was studied in healthy piglets after oral administration of a premix. Thirty pigs were given doses of 7.5 mg/kg body weight/day in the feed for 21 days. One control and five medicated piglets were randomly selected for sacrifice at 0.25, 0.5, 1, 2 and 3 days post-treatment. The residue concentrations of VLM in swine muscle, liver and kidney were detected using high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). The highest residue concentrations of VLM were attained in 0.25 day, and all of the samples were below the maximum residue limit (MRL) recommended by the European Medical Evaluation Agency (EMEA) at 0.5 day post-treatment. The residue concentrations of swine liver were significantly higher than those of kidney and muscle, which indicated liver to be the target tissue for VLM. The withdrawal period of VLM with oral administration was 24 hours.     

Determination of methylcellulose and hydroxypropyl methylcellulose food gums in food and food products: collaborative study

A collaborative study was performed to determine the reproducibility of a method for the determination of methylcellulose (MC) and hydroxypropyl methylcellulose (HPMC) in food. These widely used food gums possess unusual solubility characteristics and cannot accurately be determined by existing dietary fiber methods. The new method uses the enzyme-digestion procedure of AOAC Official Method 991.43. Digestate solutions must be refrigerated to fully hydrate MC or HPMC. The chilled solutions are filtered and analyzed by size-exclusion liquid chromatography. Collaborating laboratories received 28 samples containing MC or HPMC in the range of 0-100%. The sample set included blind duplicates of 5 food matrixes (bread, milk, fish, potato, and powdered juice drink). Cochran and Grubbs tests were used to eliminate outliers. For food samples containing MC, values for within-laboratory precision, repeatability relative standard deviation (RSDr), ranged from 4.2 to 16%, and values for among-laboratories precision, reproducibility relative standard deviation (RSDR), ranged from 11 to 20%. For HPMC samples, RSDr values ranged from 6.4 to 27%, and RSDR values ranged from 17 to 39%. Recoveries of MC and HPMC from the food matrixes ranged from 78 to 101%. These results show acceptable precision and reproducibility for the determination of MC and HPMC, for which no Official AOAC Methods exist. It is recommended that this method be adopted as AOAC Official First Action.     

Determination of vitamin B12 in infant formula and adult nutritionals by surface plasmon resonance: First Action 2011.16 (test kit method)

At the "Standards Development and International Harmonization: AOAC INTERNATIONAL Mid-Year Meeting" on June 29, 2011, an Expert Review Panel (ERP) agreed to further examine AOAC Official Method 2011.01, "Determination of Vitamin B12 by Surface Plasmon Resonance," for use with infant formula and adult nutritionals. The original collaborative study was conducted using the Biacore Q biosensor instrument and the Biacore Q Qflex Kit Vitamin B12 PI. Samples included in the study were infant formula, cereals, premixes, vitamin tablets, dietary supplements, and baby food. Eleven laboratories participated in the collaborative study. The results demonstrated a repeatability RSD (RSDr) of 1.59-27.8 and HorRat values for reproducibility of 0.34-1.89 in samples with levels ranging from ppm to ppb. The assay studied is a label-free protein binding-based assay that uses the principle of surface plasmon resonance to measure the interaction between vitamin B12 and a specific binding protein by passing a portion of the prepared sample extract combined with binding protein solution across a functionalized sensor chip. The response from the functionalized sensor chip is given as free-binding protein, as the mixture binds to the prepared surface of the chip. The ready-to-use Qflex Kit Vitamin B12 PI provides the reagents and accessories necessary to perform this assay. AOAC Method 2011.01 was approved by the AOAC Method Committee on Food Nutrition for Official First Action status, applicable to a wide range of food products, dietary supplements, and multivitamin premixes. After evaluation of the validation data available, an ERP agreed in June 2011 that the method meets standard method performance requirements, as articulated by the Stakeholder Panel on Infant Formula and Adult Nutritionals. The ERP granted the method First Action status, applicable to infant formula and adult/pediatric nutritional formula.     

Determination of clopidol residues in chicken tissues by liquid chromatography: part I. Optimization of analytical conditions and comparison with AOAC gas chromatography method

A simple and specific liquid chromatographic method was developed for determination of clopidol in chicken tissues. Samples were extracted with acetonitrile. The extracts were cleaned up on an alumina column and an anion exchange column. The clopidol was separated on a column (30 cm x 3.9 mm) of microBondapak C18 (10 microm) by using acetonitrile-water (20 + 80, v/v) as mobile phase, and determined quantitatively at 270 nm. Recoveries were 86.0-97.6%, with relative standard deviations of 2.14-9.42% at 0.010-2.0 mg/kg from 4 spiked matrixes of chicken muscle, egg, liver, and kidney. The limit of detection was 0.005 mg/kg. Compared with the modified AOAC gas chromatographic method, the present method is simple and fast to operate. Its results are accurate and reliable, making it favorable for environmental protection and meeting requirements for human safety. Thus, it is suitable for routine analysis of large quantities of samples.     

Determination of vitamin B12 in infant formula and adult nutritionals by HPLC: First Action 2011.10

During the "Standards Development and International Harmonization: AOAC INTERNATIONAL Mid-Year Meeting" held on June 29, 2011, an Expert Review Panel (ERP) reviewed the method "Determination of Vitamin B12 in Infant Formula and Adult Nutritionals by HPLC." Under the new pathway to Official Methods, the ERP adopted the method as Official First Action. The method is applicable to the determination of vitamin B12 in infant formula and adult nutritionals. Data showed an average overall intermediate precision of 6.64% RSD, an estimated quantitation limit of 0.8 microg/kg, and a detection limit of 0.2 microg/kg in prepared samples. The standard range of the method is 2 to 200 microg/L, which corresponds to an analytical range of 0.8 to 500 microg/kg.