bluuebunny/crossref_metadata_2025 huggingface dataset:
Determination of Selenium in Marine Biological Tissues by Transverse Heated Electrothermal Atomic Absorption Spectrometry with Longitudinal Zeeman Background Correction and Automated Ultrasonic Slurry Sampling
Authors: Méndez Hortensia , Alava Fausto , Lavilla Isela , Bendicho Carlos
Published: February 2020

A fast, sensitive, and reliable method for determination of selenium in marine biological tissues by electrothermal atomic absorption spectrometry with slurry sampling was developed. Slurries were prepared from fresh and frozen seafood samples that were previously homogenized, dried, and ground; particle sizes <100 μm were taken for analysis. A 3% (v/v) HNO3 solution containing 0.01% (v/v) Triton X-100 was used as slurry diluent. Slurries were mixed on an automated ultrasonic slurry sampler at 20% amplitude for 30 s just before an aliquot was injected into the furnace. The method was successfully validated against the following certified reference materials: NRCC CRM DORM-2 (Dogfish muscle); NRCC CRM TORT-2 (Lobster hepatopancreas); NRCC CRM DOLT-2 (Dogfish liver); and BCR CRM 278 (Mussel tissue), and was subsequently applied to determination of Se in 10 marine biological samples. The influences of the drying procedure (oven-, microwave-, and freeze-drying), matrix modifier amount, mass of solid material in cup, and pipetting sequence are discussed. The limit of determination of Se was 0.16 μg/g and the repeatability, estimated as between-batch precision, was in the range of 4–8%. Se contents in the samples ranged from 0.6 to 2.8 μg/g. The proposed method should be useful for fast assessment of the daily dietary intake of Se.
Use of a Ruthenium(III), Iron(II), and Nickel(II) Hexacyanometallate-Modified Graphite Electrode with Immobilized Oxalate Oxidase for the Determination of Urinary Oxalate
Authors: Milardović Stjepan , Grabarić Zorana , Rumenjak Vlatko , Blau Nenad , Milošević Dražen
Published: February 2020

This paper describes the performance of a biosensor with an Ru(III), Ni(II), and Fe(II) hexacyanometallate-modified graphite electrode and immobilized oxalate oxidase for the determination of urinary oxalate. The addition of ruthenium enhances the electrochemical reversibility and chemical stability of the electrocrystallized layer and improves the sensitivity of the biosensor. Hydrogen peroxide, produced by the enzyme-catalyzed oxidation of oxalate, was measured at −50 mV vs an Hg|Hg2Cl2|3M KCl electrode in a solution of pH 3.6 succinic buffer, 0.1M KCl, and 5.4mM ethylenediaminetetraacetic acid. The linear concentration range for the determination of oxalate was 0.18–280 μM. The recoveries of added oxalate (10–35 μM) from aqueous solution ranged from 99.5 to 101.7%, whereas from urine samples without oxalate (or with a concentration of oxalate below the detection limit) the recoveries of added oxalate ranged from 91.4 to 106.6%. The oxalate in 24 h urine samples, taken during their daily routine from 35 infants and children, was measured and found to range from 0.6 to 121.7 mg/L. There were no interferences from uric acid, acetylsalicylic acid, and urea in the concentration range investigated, but paracetamol and ascorbic acid did interfere. A good correlation (R2 = 0.9242) was found between values obtained for oxalate in real urine samples by 2 laboratories, with the proposed biosensor and ion chromatography, respectively.
Sampling Grain Shipments To Detect Genetically Modified Seed
Authors: Whitaker Thomas B , Freese Larry , Giesbrecht Francis G , Slate Andrew B
Published: February 2020

Using the binomial distribution, the effect of sample size on the variability among sample test results when sampling a lot with 1.0% genetically modified (GM) or biotech seed was evaluated. The coefficient of variation, cv, among 500-seed sample test results taken from a lot with truly 1.0% was computed to be 44.5%. Increasing sample size to 1000 seeds reduced the cv among sample test results to 31.5%. The effects of sample size and accept/reject limits on the buyer's risk (bad lots accepted) and the seller's risk (good lots rejected) was also evaluated assuming a tolerance of 1.0% GM seed. Increasing sample size decreases both the buyer's and seller's risks at the same time. Using an accept/reject limit below the regulatory tolerance decreases the buyer's risk, but increases the seller's risk. Using an accept/reject limit above the regulatory tolerance decreases the seller's risk but increases the buyer's risk.
Hydrocolloid Interferences in the Determination of Pectin by the Carbazole Method
Authors: Kyriakidis Nikolaos B , Psoma Evaggelia
Published: February 2020

In the colorimetric determination of pectin by the carbazole method, some of the interfering compounds have been identified but the possible interference of different hydrocolloids is not known. Several hydrocolloids are currently used in the preparation of imitation and adulterated orange juice for cloud stabilization. Hydrocolloids studied were gum arabic, carboxylmethyl cellulose, sodium alginate, carrageenan, guar gum, and xanthan. The effects of these hydrocolloids on the carbazole method for pectin determination was studied. Procedures are proposed for the correct use of the carbazole method for pectin determination in the presence of extraneous hydrocolloids.
Study of the Versatility of a Graphite Furnace Atomic Absorption Spectrometric Method for the Determination of Cadmium in the Environmental Field
Authors: Rucandio M Isabel , Petit-Domínguez M Dolores
Published: February 2020

Cadmium is a representative example of trace elements that are insidious and widespread health hazards. In contemporary environmental analysis, there is a clear trend toward its determination over a wide range of concentrations in complex matrixes. This paper describes a versatile method for the determination of Cd at various levels (0.1–500 μg/g) in several sample types, such as soils, sediments, coals, ashes, sewage sludges, animal tissues, and plants, by graphite furnace atomic absorption spectrometry with Zeeman background correction. The effect of the individual presence of about 50 elements, with an interference/analyte concentration ratio of up to 105, was tested; recoveries of Cd ranged from 93 to 106%. The influence of different media, such as HNO3, HCl, HF, H2SO4, HClO4, acetic acid, hydroxylammonium chloride, and ammonium acetate, in several concentrations, was also tested. From these studies it can be concluded that the analytical procedure is scarcely matrix dependent, and the results obtained for a wide diversity of reference materials are in good agreement with the certified values.
Wind Tunnel Simulation of Air Pollution Dispersion in a Street Canyon
Authors: Civiš Svatopluk , Střižík Michal , Jaňour Zbynk , Holpuch Jan , Zelinger Zdenk
Published: February 2020

Physical simulation was used to study pollution dispersion in a street canyon. The street canyon model was designed to study the effect of measuring flow and concentration fields. A method of CO2-laser photoacoustic spectrometry was applied for detection of trace concentration of gas pollution. The advantage of this method is its high sensitivity and broad dynamic range, permitting monitoring of concentrations from trace to saturation values. Application of this method enabled us to propose a simple model based on line permeation pollutant source, developed on the principle of concentration standards, to ensure high precision and homogeneity of the concentration flow. Spatial measurement of the concentration distribution inside the street canyon was performed on the model with reference velocity of 1.5 m/s.
Determination of Arsenic in Homeopathic Drugs by Bromide Volatilization-Inductively Coupled Plasma-Atomic Emission Spectrometry
Authors: Lopez-Molinero Angel , Villareal Anselmo , Velilla Cesar , Andía David , Castillo Juan R
Published: February 2020

Arsenic in homeopathic drugs was determined by coupling a volatile generation with inductively coupled plasma-atomic emission spectrometry. The method is based on the chemical vaporization of arsenic(III) with bromide ions in sulfuric acid media using a batch procedure and subsequent introduction of the gaseous analyte into the plasma torch. The main and interactive effects of the experimental variables affecting this method were evaluated by a 2-level full factorial design. In optimized conditions by Simplex, the method shows an absolute detection limit (3 s) of 0.28 μg for the injection of 200 μL sample. The precision (% relative standard deviation) of the determination was 4.2% at a level of 50 μg/mL As(III) (n = 5). The interference effect of various ions on the arsenic signal was evaluated.
Dry Rehydratable Film Method for Rapid Enumeration of Coliforms in Foods (3M™ Petrifilm™ Rapid Coliform Count Plate): Collaborative Study
Authors: Lindberg Kathryn G , Lindberg Kathryn G , Kinneberg Karen M , Lindberg Kathryn G ,   Collaborators:, Batterson D , Bobb R , Boleszczuk P , Brudvig S , Bryant D , Bryce J , Buckner K , Bulthaus M , DeJesus J , Ellis K , Finkenbiner D , Fleming S , Follni-Lieder E , Harper C , Ihrke P , Johnson K , King J , Langridge M , Maycock L , McAteer L , McCann T , Otten N , Robbins R , Sass A , Saunders L , Schop R , Strand S , Tebay D , VanWinkle J , Wolowski C
Published: February 2020

A rehydratable dry-film plating method for coliforms in foods, the 3M™ Petrifilm™ Rapid Coliform Count plate method, was compared with the U.S. Food and Drug Administration's Bacteriological Analytical Manual method for nondairy foods and the American Public Health Association's Standard Methods for the Examination of Dairy Products (SMEDP) method for dairy foods. Six food types, vanilla ice cream, cheddar cheese, fresh refrigerated uncooked pasta, wheat flour, prepared frozen macaroni and cheese, and frozen hash browns, were analyzed for coliforms by 11 collaborating laboratories. For each food product tested, the collaborators received 8 blind samples consisting of a control sample and 3 levels of inoculated sample, each in duplicate. The mean log counts for the methods were comparable. The repeatability and reproducibility variances of the Petrifilm Rapid Coliform Count method at 14 and 24 h were not significantly different from those of the standard methods.
Determination of Vitamin B12 in Milk Products and Selected Foods by Optical Biosensor Protein-Binding Assay: Method Comparison
Authors: Indyk Harvey E , Persson Bjorn S , Caselunghe Malin C B , Moberg Anna , Filonzi Enrico L , Woollard David C
Published: February 2020

Biomolecular interaction analysis was evaluated for the automated determination of vitamin B12 in a range of foods. The analytical technique was configured as a biosensor-based, nonlabeled inhibition protein-binding assay using nonintrinsic R-protein. Sample extraction conditions were optimized, and both ligand specificity and nonspecific binding considerations were evaluated. Performance parameters included a quantitation range of 0.08–2.40 ng/mL, recoveries of 89–106%, agreement against assigned reference values for 3 independent certified food reference materials, and a mean between-laboratory reproducibility relative standard deviation of 4.9%. The proposed method was compared with reference microbiological and radioisotope protein-binding methods for a range of food samples. A wide selection of milks, infant formulas, meats, and liver were evaluated for their vitamin B12 content. The influence of season was studied in herd milk, early lactation was followed for a single animal, and the cobalamin content of bovine, caprine, and ovine milks was compared.
Residues of Oxytetracycline and Its 4′-Epimer in Edible Tissues from Turkeys
Authors: Capolongo Francesca , Santi Annalisa , Tomasi Luciana , Anfossi Paola , Missagia Mauro , Montesissa Clara
Published: February 2020

Residues of oxytetracycline (OTC) in edible tissues (muscle, liver, and kidney) of 18 turkeys were determined after continuous administration of the drug for 3 days in drinking water at the maximum recommended concentration of 400 mg/L. The European Union (EU) maximum residue limits (MRLs) set for OTC are 100 μg/kg in muscle tissues, 300 μg/kg in liver, and 600 μg/kg in kidney, as the sum of the parent compound and its derivative 4′-epi-oxytetracycline (4-epi-OTC). Cleanup of tissue samples was performed by metal chelate affinity chromatography (MCAC), but the original technique was miniaturized by the adoption of a mini solid-phase extraction column, allowing reduction of solvents, time, and hazardous waste. OTC and its 4′-epimer were quantitated by an isocratic liquid chromatography elution with UV detection. After 1 day of withdrawal, OTC plus 4-epi-OTC residues were greater than MRL values in muscle and liver; 3 days after the end of treatment, all tissue residues were far lower than the MRL values. At the first day after the end of treatment, 4-epi-OTC was detected at very low concentrations only in muscle, in liver after 1 and 3 days of withdrawal, and in kidney at all sampling times. The withdrawal time was calculated according to EU recommendations and was set at 5 days.
Comparison of Assurance Gold Salmonella EIA, BAX for Screening/Salmonella, and GENE-TRAK Salmonella DLP Rapid Assays for Detection of Salmonella in Alfalfa Sprouts and Sprout Irrigation Water
Authors: Stewart Diana S , Reineke Karl F , Tortorello Mary L
Published: February 2020

The Assurance Gold Salmonella EIA, BAX for Screening/Salmonella, and GENE-TRAK Salmonella DLP rapid assays were compared with official cultural methods described in the Bacteriological Analytical Manual (BAM) for analysis of alfalfa sprouts and sprout irrigation water for the presence of Salmonella. The lower limits of detection of 4 serovars of Salmonella cells (S. tennessee, S. muenchen, S. mbandanka, and S. cubana) in pure culture were determined as approximately log10 2, 5, and 6 for the BAX, GENE-TRAK, and Gold EIA, respectively. Despite its low detection limit, the BAX did not perform as well as the other assays in analyzing contaminated sprouts and sprout irrigation water. For 4 different lots of sprouts and sprout irrigation water samples inoculated with the 4 serovars at low [1-2 colony forming units (CFU/g)] and high (68–180 CFU/g) levels, the BAX detected Salmonella in 58/64 (90.6%) of the samples, compared with 64/64 (100%) by the GENE-TRAK, Gold EIA, and BAM methods. Assay performance was also compared for analysis of naturally contaminated sprouts and sprout irrigation water with 3 lots of alfalfa sprouted seeds associated with different salmonellosis outbreaks. Positive assay results for the naturally contaminated samples were Gold EIA 41, GENE-TRAK 36, BAM 33, and BAX 13.
Determination of Total Dietary Fiber in Selected Foods Containing Resistant Maltodextrin by Enzymatic-Gravimetric Method and Liquid Chromatography: Collaborative Study
Authors: Gordon Dennis T , Okuma Kazuhiro ,   Collaborators:, DeVries J W , Fukuhara K , Jacob W , Kuriyama N , Li B W , Matsuda I , McMonagle K , Parr G D , Porter S , Strong S , Sugimoto T , Tsuji K , Wolf B
Published: February 2020

A method was developed for determination of total dietary fiber (TDF) in foods containing resistant maltodextrin (RMD) which includes nondigestible carbohydrates that are not fully recovered as dietary fiber by conventional TDF methods such as AOAC 985.29 or 991.43. Because the average molecular weight (MW) of RMD is 2000 daltons, lower MW soluble dietary fiber components do not precipitate in 78% ethanol; therefore, RMD is not completely quantitated as dietary fiber by current AOAC methods. The accuracy and precision of the method was evaluated through an AOAC collaborative study. Ten laboratories participated and assayed 12 test portions (6 blind duplicates) containing RMD. The 6 test pairs ranged from 1.5 to 100% RMD. The method consisted of the following steps: (1) The insoluble dietary fiber (IDF) and high MW soluble dietary fiber (HMWSDF) were determined by AOAC 985.29. (2) Ion exchange resins were used to remove salts and proteins contained in the AOAC 985.29 filtrates (including ethanol and acetone). (3) The amount of low MWRMD (LMWRMD) in the filtrates were determined by liquid chromatography. (4) The TDF was calculated by summation of the IDF, HMWSDF, and LMWRMD fractions having nondigestible carbohydrates with a degree of polymerization of 3 and higher. Repeatability standard deviations (RSDr) were 1.33–7.46%, calculated by including outliers, and 1.33–6.10%, calculated by not including outliers. Reproducibility standard deviations (RSDR) were 2.48–9.39%, calculated by including outliers, and 1.79–9.39%, calculated by not including outliers. This method is recommended for adoption as Official First Action.
Determination of the Total Nitrogen Content of Hard, Semihard, and Processed Cheese by the Kjeldahl Method: Collaborative Study
Authors: Lynch Joanna M , Barbano David M , Fleming J Richard ,   Collaborators:,   Barbano Laboratory,   California Department of Food and Agriculture,   Dairy One,   Dairy Quality Control Institute, Inc,   Land O’Lakes,   State of Wisconsin Department of Agriculture,   U.S. Department of Agriculture (USDA) Atlanta Milk Market Administrator Laboratory,   USDA Boston Milk Market Administrator Laboratory,   USDA Chicago Milk Market Administrator Laboratory,   USDA Cleveland Milk Market Administrator Laboratory,   USDA Dallas Milk Market Administrator Laboratory,   USDA Kansas City Milk Market Administrator Laboratory,   USDA Louisville Milk Market Administrator Laboratory,   USDA Seattle Milk Market Administrator Laboratory,   USDA Tulsa Milk Market Administrator Laboratory
Published: February 2020

The objective of this collaborative study was to determine interlaboratory performance statistics for a modified and optimized version of AOAC Method 920.123 for the determination of the total nitrogen content of hard, semihard, and processed cheese by Kjeldahl analysis. Details included addressing the issues of material homogeneity, test portion size (1 g), quantitative transfer (weighing on to filter paper), ensuring system suitability (nitrogen recoveries), and using AOAC Method 991.20 as the basis for nitrogen analysis. Fifteen laboratories tested 18 pairs of blind duplicate cheese materials with a crude protein content between 18 and 36%. Materials represented hard, semihard, and processed commercial cheeses with a wide range of composition. Statistical performance parameters expressed as crude protein (nitrogen × 6.38), g/100 g, with invalid and outlier data removed were mean = 26.461, repeatability standard deviation (Sr) = 0.111, reproducibility standard deviation (SR) = 0.153, repeatability relative standard deviation (RSDr) = 0.42%, reproducibility relative standard deviation (RSDR) = 0.58%, repeatability (r) = 0.312, and reproducibility (R) = 0.428. The interlaboratory study results were acceptable and comparable to those for the milk Kjeldahl nitrogen method on a relative nitrogen basis. The Study Directors recommend that this modified method for the determination of total nitrogen in hard, semihard, and processed cheese by Kjeldahl analysis be adopted First Action as an improved method to replace Method 920.123.
Analysis of Grass Silage from Northwestern Spain by Near-Infrared Reflectance Spectroscopy
Authors: Villamarín Begoña , Fernández Esperanza , Mendéz Jesus
Published: February 2020

Near-infrared reflectance spectroscopy (NIRS) was evaluated for the determination of protein, crude fiber (CF), acid detergent fiber (ADF), and neutral detergent fiber (NDF) in grass silage. Calibration equations were based on analyses of 366 samples of grass silage produced in Northwestern Spain over 4 consecutive years (1992–1995) and validated by analyses of a set of 72 silage samples harvested during 1996. Dried and ground samples were analyzed by chemical and NIRS procedures. The spectral data were analyzed by regression against a range of chemical parameters, using modified partial least-squares (MPLS) multivariate analysis in conjunction with different mathematical treatments of the spectra. For each parameter, the optimum calibration was evaluated on the basis of the coefficient of multiple determination (R2), the coefficient of simple correlation (r2), the standard error of calibration (SEC), the standard error of cross-validation (SECV), and the standard error of validation (SEV). R2 and r2 were >0.90; SEC values were 0.58, 1.04, 1.40, and 1.75; SECV values were 0.64, 1.15, 1.50, and 2.04; and SEV values were 0.56, 1.02, 1.42, and 1.80 for protein, CF, ADF, and NDF, respectively. The ratio of the standard deviation of the reference data to the SEV was >3.0 for each of the 4 parameters, which indicates that the equations can be used in routine analysis.
Determination of Mercury in Seafood by Flow Injection–Cold Vapor Atomic Absorption Spectrometry after Microwave Digestion: NMKL Interlaboratory Study
Authors: Julshamn Kaare , Brenna Jan ,   Collaborators:, Åsman B , Ekman A , El-Ghauoui A , Gjerstad K-O , Grønningen D , Hammer S H , Jensen A M , Liukkonen-Lilja H , Mikkola J , Ruth T , Sedal L O , Solli B , Venalainen E-R , Wollertsen N
Published: February 2020

Ten laboratories participated in an interlaboratory method-performance (collaborative) study of a method for the determination of mercury in foods of marine origin by flow injection–cold vapor atomic absorption spectrometry after wet digestion using a microwave oven technique. The study was preceded by a training round of samples of known identity. The method was tested on a total of 7 seafood products: blue mussel (Mytilus edulis), cod muscle (Gadus morhua), crab (Cancer pagurus), scampi (Nephrops norwegicus), black scabbard fish (Aphnopus carbo), longnose velvet dogfish (Centroscymus crepidater), and Portuguese dogfish (Cenbroscymus coelolepis) with mercury concentrations of 0.14, 0.24, 0.35, 0.59, 1.42, 4.2, and 13.2 μg/g, respectively. The materials were presented to the participants in the study as blind duplicates, and the participants were asked to perform single determinations on each sample. Repeatability relative standard deviations (RSDr) for mercury ranged from 2.4 to 14.0%. Reproducibility relative standard deviations (RSDR) ranged from 7.7 to 16.6%. HORRAT values for all samples were <1.0.
Isolation of Light Filth from Ground Oregano and Ground Marjoram: A Modification Using Isopropanol as a Defatting Agent: In-House Study
Authors: Wheeler Mark Wheeler , Bennett Barbara , Marks Harry
Published: February 2020

A procedural modification of the AOAC Official Method for extracting light filth from ground oregano and ground marjoram was tested in an intralaboratory study. The modified method specifies isopropanol defatting, 975.49A(a), rather than chloroform–isopropanol defatting, 975.49A(b), followed by direct flotation as directed in AOAC Official Method, 975.49B(b). The modified method provided comparable results in less time while also providing safety, health, and financial benefits.
Determination of Vitamin K1 Isomers in Foods by Liquid Chromatography with C30 Bonded-Phase Column
Authors: Woollard David C , Indyk Harvey E , Fong Bertram Y , Cook Kathleen K
Published: February 2020

Vitamin K1 was determined in a variety of foods by using reversed-phase liquid chromatography with a C30 column followed by post-column reduction to the fluorescent hydroquinone derivatives. Lipids were removed by lipase digestion, followed by single extraction into hydrocarbon, and the protocol was extended to selected natural and processed foods. Biologically active trans- and inactive cis-vitamin K1 isomers were measured individually to evaluate the true nutritional status of the products. Method performance parameters confirmed the validity of the technique. The use of the triacontylbonded C30 phase for selective phylloquinone isomer measurement extends previously validated AOAC Method 999.15 for vitamin K1 in milk and infant formula to a wider range of foods important in the human diet. The cis-vitamin K1 isomer contributes up to about 15% of total phylloquinone in certain foods.
Analytical Challenges: Bridging the Gap from Regulation to Enforcement
Authors: Eede Guy van den , Kay Simon , Anklam Elke , Schimmel Heinz
Published: February 2020

An overview is presented of the analytical steps that may be needed to determine the presence of genetically modified organisms (GMOs) or for analysis of GMO-derived produce. The analytical aspects necessary for compliance with labeling regulations are discussed along with bottlenecks that may develop when a plant product or a food sample is analyzed for conformity with current European Union GMO legislation. In addition to sampling and testing, other topics deal with complications that arise from biological and agricultural realities that may influence testing capabilities. The issues presented are intended to serve as elements to examine the different challenges that enforcement laboratories might face.
Production of Certified Reference Materials for the Detection of Genetically Modified Organisms
Authors: Trapmann Stefanie , Schimmel Heinz , Kramer Gerard Nico , Eede Guy van den , Pauwels Jean
Published: February 2020

Certified reference materials (CRMs) are an essential tool in the quality assurance of analytical measurements. They are produced, certified, and used in accordance with relevant ISO (International Organization for Standardization) and BCR (Community Bureau of Reference) guidelines. The Institute for Reference Materials and Measurements (IRMM; Geel, Belgium) has produced the first powdery genetically modified organism (GMO) CRMs in cooperation with the Institute for Health and Consumer Protection (Ispra, Italy). Until now, different weight percentages in the range of 0–5%for 4 GMOs in Europe were produced and certified: Bt (Bacillus thuringiensis)-11 and Bt-176 maize, Roundup Ready® soybean, and MON810 maize. Bt-11 and Bt-176 maize and Roundup Ready soybean were produced by IRMM on behalf of Fluka Chemie AG (Buchs, Switzerland). Characterization of used base material is the first step in production and is especially important for GMO CRMs. The production of powdery GMO CRMs and methods used for production control are described. Thorough control of homogeneity and stability are essential for certification of reference materials and ensure validity of the certificate for each bottle of a batch throughout a defined shelf-life. Because production of reference materials and their maintenance are very labor- and cost-intensive tasks, the usefulness of new types of GMO CRMs must be estimated carefully.
Kinetic Spectrophotometric Determination of Atenolol in Dosage Forms
Authors: Al-Ghannam Sheikha M , Belal Fathalla
Published: February 2020

A simple kinetic procedure is described for the determination of atenolol in its dosage forms. The procedure is based on coupling the drug with 4-chloro-7-nitrobenzo-2-oxa-1,3-diazole in pH 8 borate buffer at the boiling temperature for a fixed time of 30 min, and then measuring the absorbance of the reaction product at 460 nm. The absorbance–concentration plot is rectilinear over the range 5–50 μg/mL with a minimum detection limit of 1.3 μg (4.9 × 10−6M). The determination of atenolol by the fixed-concentration and rate-constant methods is also feasible with the calibration equations obtained, but the fixed-time method proved to be more applicable. The procedure was applied successfully to commercial tablets, and statistical analysis showed that the results compared favorably with those obtained by the official methods. The interference likely to be introduced from some coformulated drugs and the effect of sensitizers and surfactants on the performance of the proposed method were also studied. A proposed reaction pathway is presented.
Simultaneous Determination of Codeine and Pyridoxine in Pharmaceutical Preparations by First-Derivative Spectrofluorimetry
Authors: Molina-Díaz Antonio , Ramos-Martos Natividad , Navalón Alberto , Capitán-Vallvey Luis F
Published: February 2020

A method for the simultaneous determination of codeine and pyridoxine was developed, based on the measurement of their native fluorescence signals, by using first-derivative spectrofluorimetry to resolve the mixture. Codeine was measured at λem = 309 nm, and pyridoxine was measured at λem = 450 nm. Instrumental parameters were optimized, and the emission spectra were recorded between 275 and 475 nm, at λex = 255 nm and excitation and emission slit widths of 2.5 and 10 nm, respectively. Systematic studies on the influence of species usually present along with the analytes (such as caffeine, ascorbic acid, paracetamol, and thiamine) were also performed. The calibration graphs were linear over the ranges of 0.5–7.0 and 0.1–1.0 μg/mL for codeine and pyridoxine, respectively, and the relative standard deviations (n = 10) were about 3%. The method was successfully applied to the determination of codeine and pyridoxine in solutions of synthetic mixtures and in synthetic and semisynthetic pharmaceutical formulations.
Liquid Chromatographic Determination of S-Adenosyl-L-Methionine in Dietary Supplement Tablets
Authors: Zhou Joseph Ziqi , Waszkuc Ted , Garbis Spiro , Mohammed Felicia
Published: February 2020

A simple and reliable liquid chromatographic method was developed for the determination of S-adenosyl-L-methionine (SAM) in dietary supplement tablets. SAM in products was extracted with a phosphate buffer and separated from the mixture on a reversed-phase C8 column by ion-pair chromatography. A gradient mobile phase containing phosphate buffer, sodium octanesulfonate as the ion-pair reagent, and acetonitrile at a flow rate of 1.2 mL/min was used in the analysis. The UV detection wavelength was set at 257 nm. The calibration curve was linear over a range of 75–375 μg/mL for the SAM active ion with R2 = 0.9999. Replicate tests indicated good reproducibility of the method with a relative standard deviation of 0.9% (n = 8). The multiple extractions and recoveries from fortified products showed the high accuracy of the analysis. The use of the acidic buffer for SAM extraction and elution and the use of a fresh standard for each calibration to counteract the instability of the SAM compound significantly improved the accuracy of the method.
Spectrophotometric Determination of Organic Nitrogen by a Modified Lassaigne Method and Its Application to Meat Products and Baby Food
Authors: Demirata Birsen , Apak Resat , Afsar Hüseyin , Tor Izzet
Published: February 2020

A modified Lassaigne method was developed for N determination based on fusion of the organic substance with metallic Na, conversion of the cyanide in the aqueous leachate to thiocyanate by ammonium polysulfide treatment, and colorimetric measurement of the thiocyanate formed by the addition of excessive ferric ions in acidic medium. The mean molar absorptivity of the Fe(NCS)2+ complex at 480 nm is 2.96 × 103 L/mol·cm, enabling quantitation of 0.25–7.72 ppm N (linear range) in the final solution. The relative amounts of Na, (NH4)2S2, and Fe(III) with respect to nitrogen in the analyte were optimized. The developed method was successfully applied to the determination of N in various brands of baby food, and it was compared statistically with the conventional Kjeldahl and elemental analysis methods. Protein nitrogen in a number of meat products was also precisely determined by the developed method. Thus, the total digestion time of the conventional Kjeldahl method was reduced considerably (e.g., to approximately 15 min for a dried sample) with a relatively simple spectrophotometric method requiring no sophisticated instrumentation.
Rapid Detection of Single Cell Bacteria as a Novel Approach in Food Microbiology
Authors: D′Haese Eva , Nelis Hans J
Published: February 2020

Solid-phase cytometry (SPC) is a novel technique that allows rapid detection of bacteria at the single cell level, without the need for a growth phase. After filtration of the sample, the retained microorganisms are fluorescently labeled on the membrane filter and automatically counted by a laser scanning device. Each fluorescent spot can be visually inspected with an epifluorescence microscope connected to the ChemScan by a computer-driven moving stage. Depending on the fluorogenic labels used, information on the identity and the physiological status of the microorganisms can be obtained within a few hours. Although SPC was originally recommended for the determination of the total viable microbial count in water and other liquid samples, it may also be a promising technique for the detection and enumeration of bacteria in food samples, provided they can be isolated from the unfilterable matrix. The short detection time inherent in this approach is a considerable advantage over conventional plate counting, especially for slow-growing microorganisms. The basic principles of SPC are discussed as well as its potential for the detection of Mycobacterium paratuberculosis, a model example of a slow-growing bacterium in milk.
Confirmation of Phenylbutazone Residues in Bovine Kidney by Liquid Chromatography/Mass Spectrometry
Authors: Clark Susan B , Turnipseed Sherri B , Nandrea Gene J , Madson Mark R , Hurlbut Jeffrey A , Sofos John N
Published: February 2020

A confirmatory method is described for phenylbutazone (PB) residues in bovine kidney tissue. Ground kidney tissue is diluted with water, and the mixture is made basic with 25% ammonium hydroxide in water; the lipids are extracted with ethyl and petroleum ethers. The ether layer is discarded, and the tissue is acidified with 6N HCl. PB residues are extracted with tetrahydrofuran–hexane (1 + 4). The extract is passed through a silica solid-phase extraction column, and the eluate is evaporated to dryness. The residue is dissolved in acidified acetonitrile–water–acetic acid (50 + 49.4 + 0.6). A single quadrupole mass spectrometer coupled to a liquid chromatograph with an electrospray interface is used to confirm the identity of the PB residues in the kidney extract. Negative-ion detection with selected-ion monitoring of 4 ions is used. Sets of control and fortified-control kidney tissues (at 50, 100, and 200 ppb PB) and several kidney tissue field samples were analyzed for method validation. The method was tested further during the course of a survey to determine the incidence of PB residues in bovine kidney samples obtained from slaughterhouses across the country. In addition, the method was tested for use with an ion-trap mass spectrometer coupled to a liquid chromatograph, which allowed confirmation of PB at lower levels (5–10 ppb) in kidney tissue.
Determination of Cimetidine, Famotidine, and Ranitidine Hydrochloride in the Presence of Their Sulfoxide Derivatives in Pure and Dosage Forms by High-Performance Thin-Layer Chromatography and Scanning Densitometry
Authors: Kelani Khadiga M , Aziz Azza M , Hegazy Maha A , Fattah Laila Abdel
Published: February 2020

A selective, precise, and accurate method was developed for the determination of cimetidine (C), famotidine (F), and ranitidine hydrochloride (R·HCI)in the presence of their sulfoxide derivatives. The method involves quantitative densitometric evaluation of mixtures of the drugs and their derivatives after separation by high-performance thin-layer chromatography on silica gel plates (10 × 20 cm) with ethyl acetate–isopropanol–20% ammonia (9 + 5 + 4, v/v) as the mobile phase for both C and F and ethyl acetate–methanol–20% ammonia (10 + 2 + 2, v/v) as the mobile phase for R·HCI; Rf values for C, F, and R·HCI and their corresponding derivatives were 0.85 and 0.59, 0.73 and 0.41, and 0.56 and 0.33, respectively. Developing time was approximately 20 min. For densitometric evaluation, peak areas were recorded at 218, 265, and 313 nm for C, F, and R·HCI, respectively. The relationship between concentration and the corresponding peak area was plotted for the ranges of 5–50 μg/spot for C and 2–20 μg/spot for F and R·HCl. Mean recoveries were 100.39 ± 1.33, 99.77 ± 1.30, and 100.09 ± 0.69% for C, F, and R·HCI, respectively. The proposed method was used successfully for stability testing of the pure drugs in the presence of up to 90% of their degradates, in bulk powder and dosage forms. The results obtained were analyzed statistically and compared with those obtained by the official methods.
Measurement of α-Amylase Activity in White Wheat Flour, Milled Malt, and Microbial Enzyme Preparations, Using the Ceralpha Assay: Collaborative Study
Authors: McCleary Barry V , McNally Marian , Monaghan Dympna , Mugford David C ,   Collaborators:, Black C , Broadbent R , Chin M , Cormack M , Fox R , Gaines C , Gothard P , Home S , Howes; E , Johnson C , Keeping R , Koliatsou M , Lindhauer M , Marins de Sa R , Martin R , Monaghan D , Nees U , Nishwitz; R , Palmer G , Panozzo J , Recabarren J , Roumeliotis S , Seddig S , Solah V , Sonnet M , Themeier H
Published: February 2020

This study was conducted to evaluate the method performance of a rapid procedure for the measurement of α-amylase activity in flours and microbial enzyme preparations. Samples were milled (if necessary) to pass a 0.5 mm sieve and then extracted with a buffer/salt solution, and the extracts were clarified and diluted. Aliquots of diluted extract (containing α-amylase) were incubated with substrate mixture under defined conditions of pH, temperature, and time. The substrate used was nonreducing end-blocked p-nitrophenyl maltoheptaoside (BPNPG7) in the presence of excess quantities of thermostable α-glucosidase. The blocking group in BPNPG7 prevents hydrolysis of this substrate by exo-acting enzymes such as amyloglucosidase, α-glucosidase, and β-amylase. When the substrate is cleaved by endo-acting α-amylase, the nitrophenyl oligosaccharide is immediately and completely hydrolyzed to p-nitrophenol and free glucose by the excess quantities of α-glucosidase present in the substrate mixture. The reaction is terminated, and the phenolate color developed by the addition of an alkaline solution is measured at 400 nm. Amylase activity is expressed in terms of Ceralpha units; 1 unit is defined as the amount of enzyme required to release 1 μmol p-nitrophenyl (in the presence of excess quantities of α-glucosidase) in 1 min at 40°C. In the present study, 15 laboratories analyzed 16 samples as blind duplicates. The analyzed samples were white wheat flour, white wheat flour to which fungal α-amylase had been added, milled malt, and fungal and bacterial enzyme preparations. Repeatability relative standard deviations ranged from 1.4 to 14.4%, and reproducibility relative standard deviations ranged from 5.0 to 16.7%.
AOAC INTERNATIONAL Methods Committee Guidelines for Validation of Qualitative and Quantitative Food Microbiological Official Methods of Analysis
Authors: Feldsine Philip , Abeyta Carlos , Andrews Wallace H
Published: February 2020

Responding to a need for a guide for conducting Official Method validation studies of microbiological methods, AOAC utilized the experience of three microbiologists who have been active in the field of method validation. In collaboration, a document was prepared which covered the following areas: terms and their definitions associated with the Official Methods program (e.g., reference methods, alternative methods, and ruggedness testing), protocols and validation requirements for qualitative methods versus those for quantitative methods, the concept of the precollaborative study, ruggedness testing, tests for significant differences, performance indicators, and the approval process. After its preparation, this document was reviewed by the members of the Methods Committee on Microbiology and Extraneous Materials and by members of the Official Methods Board. Herein is presented the approved version of that document.
Assessment of Performance of Laboratories in Determining Acrylamide in Crispbread
Authors: Clarke Don B , Kelly Janet , Wilson Lesley A
Published: February 2020

A proficiency testing round was undertaken to assess the performance of laboratories to measure acrylamide in a sample of crispbread. Retail samples of crispbread were ground to a fine powder and after thorough mixing were packed in 40 g units for distribution. Ten samples were selected at random and analyzed in duplicate for acrylamide by liquid chromatography/mass spectrometry LC/MS). Standard statistical tests showed that the material was homogeneous for the purposes of proficiency testing. Test samples were distributed to 55 laboratories in 16 countries in Europe, North America, Australia, and the Middle East. The results were analyzed by standard proficiency testing statistical procedures, and laboratories were awarded z-scores on the basis of their reported results. Based on a target standard deviation (σp value) taken from the Horwitz equation, for a robust mean value of 1.2 mg/kg acrylamide, satisfactory results (z-score within ± 2 for those between 0.8 and 1.6 mg/kg) were obtained by 86% of the 37 laboratories that returned results. Only 1 laboratory was unsatisfactory and 4 had questionable results. About equal numbers of laboratories used gas chromatography (GC)/MS and LC/MS procedures with about 25% using MS/MS and one using GC with electron capture detection. There was no evident trend in performance or bias in results. GC/MS and LC/MS data were evenly distributed across the population of laboratories reporting results.
Multilaboratory Trial for Determination of Ceftiofur Residues in Bovine and Swine Kidney and Muscle, and Bovine Milk
Authors: Hornish Rex E , Hamlow Philip J , Brown Scott A
Published: February 2020

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 desfuroyl-ceftiofur-related residues containing the intact β-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 μg/g for milk, 8.0 μg/g for kidney (both species), 1.0 μg/g for bovine muscle, and 2.0 μg/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.
Enumeration of Total Yeasts and Molds in Foods by the SimPlate® Yeast and Mold–Color Indicator Method and Conventional Culture Methods: Collaborative Study
Authors: Feldsine Philip T , Lienau Andrew H , Leung Stephanie C , Mui Linda A
Published: February 2020

The relative effectiveness of the SimPlate Yeast and Mold-Color Indicator method (Y&M–CI) was compared to the U.S. Food and Drug Administration's (FDA) Bacteriological Analytical Manual (BAM) method and the proposed International Organization for Standardization (ISO) method, ISO/CD 21527, for enumerating yeasts and molds in foods. Test portions were prepared and incubated according to the conditions stated in both the BAM and ISO methods. Six food types were analyzed: frozen corn dogs, nut meats, frozen fruits, cake mix, cereal, and fresh cheese. Nut meats, frozen fruits, and fresh cheese were naturally contaminated. All other foods were artificially contaminated with either a yeast or mold. Seventeen laboratories throughout North America and Europe participated in the study. Three method comparisons were conducted. In general, there was <0.3 mean log count difference in recovery between the SimPlate method and the 2 corresponding reference methods. Moreover, mean log counts between the 2 reference methods were also very similar. The repeatability (sr) and reproducibility (sR) standard deviations were comparable between the 3 method comparisons. These results indicate that the BAM method and the SimPlate method are equivalent for enumerating yeast and mold populations in foods. Similarly, the SimPlate method is comparable to the proposed ISO method when test portions are prepared and incubated as defined in the proposed ISO method.
Detection of Botulinal Neurotoxins A, B, E, and F by Amplified Enzyme-Linked Immunosorbent Assay: Collaborative Study
Authors: Ferreira Joseph L , Maslanka Susan , Johnson Eric , Goodnough Mike ,   Collaborators:, Barash J , Boersma T , Brown E , Dykes J , Eliasberg S , Inami G , Lau D , Lindsey C , Ludwig G , Minor E , Parker T , Reddy R , Skinner G , Solomon H , Tepp B , Tetzloff R
Published: February 2020

An amplified enzyme-linked immunosorbent assay (amp-ELISA) was compared with the AOAC Official Method 977.26 for detection of Clostridium botulinum and its toxins in foods. Eleven laboratories participated and the results of 10 laboratories were used in the study. Two anaerobic culture media, tryptone peptone glucose yeast extract (TPGY) and cooked meat medium (CMM) were used to generate toxic samples with types A, B, E, and F botulinal strains. Nonbotulinal clostridia were also tested. The toxicity of each botulinal culture was determined by the AOAC method, and the cultures were then diluted, if necessary, to high (about 10 000 minimal lethal dose [MLD]/mL) and low (about 100 MLD/mL) test samples. The overall sensitivity of detection in TPGY and CMM cultures with the amp-ELISA was 94.7% at about 100 MLD/mL and 99.6% for samples with ≥10 000 MLD/mL toxicity. The amp-ELISA detection sensitivity for low toxin samples was 92.3% in TPGY and 99.4% in CMM. The false-positive rate ranged from 1.5% for type A to 28.6% for type F in TPGY, and from 2.4% for type A to 11.4% for type F in CMM. Most of the cross-reactivity was due to detection of other botulinal types, especially in high toxin samples. The amp-ELISA could be used to screen suspect cultures for botulinal toxins. Positive amp-ELISA samples would be confirmed by the AOAC reference method.
First Proficiency Testing To Evaluate the Ability of European Union National Reference Laboratories To Detect Staphylococcal Enterotoxins in Milk Products
Authors: Hennekinne Jacques-Antoine , Gohier Martine , Maire Tiphaine , Lapeyre Christiane , Lombard Bertrand , Dragacci Sylviane
Published: February 2020

The European Commission has designed a network of European Union-National Reference Laboratories (EU-NRLs), coordinated by a Community Reference Laboratory (CRL), for control of hygiene of milk and milk products (Council Directive 92/46/ECC). As a common contaminant of milk and milk products such as cheese, staphylococcal enterotoxins are often involved in human outbreaks and should be monitored regularly. The main tasks of the EU-CRLs were to select and transfer to the EU-NRLs a reference method for detection of enterotoxins, and to set up proficiency testing to evaluate the competency of the European laboratory network. The first interlaboratory exercise was performed on samples of freeze-dried cheese inoculated with 2 levels of staphylococcal enterotoxins (0.1 and 0.25 ng/g) and on an uninoculated control. These levels were chosen considering the EU regulation for staphylococcal enterotoxins in milk and milk products and the limit of detection of the enzyme-linked immunosorbent assay test recommended in the reference method. The trial was conducted according to the recommendations of ISO Guide 43. Results produced by laboratories were compiled and compared through statistical analysis. Except for data from 2 laboratories for the uninoculated control and cheese inoculated at 0.1 ng/g, all laboratories produced satisfactory results, showing the ability of the EU-NRL network to monitor the enterotoxin contaminant.