bluuebunny/crossref_metadata_2025 huggingface dataset:
Gas Chromatographic/Nitrogen-Phosphorus Detection Method for Determination of Ethylene Thiourea in Finished Drinking Waters: Collaborative Study
Authors: Longbottom James E , Edgell Kenneth W , Erb Elizabeth J , Lopez-Avila Viorica ,   Collaborators:, Brooks M , Byrne C , Clark D , Docus S , Kary K , Parker G , Perkins K , Pierri A , Quick F E , Simmons K , Torma L , Zimmerman D
Published: February 2020

A joint U.S. Environmental Protection Agency (USEPA)-AOAC interlaboratory method validation study was conducted on USEPA National Pesticide Survey (NPS) Method 6, "Determination of Ethylene Thiourea (ETU) in Finished Drinking Water by Gas Chromatography with a Nitrogen-Phosphorus Detector." The purpose of the study was to determine and compare the mean recoveries and precision for determination of ETU in reagent water and finished drinking waters. The study design was based on Youden's nonreplicate plan for collaborative tests of analytical methods. The waters were spiked with ETU at 6 concentrations levels, prepared as 3 Youden pairs. In the method, the test water is extracted by passing the sample through an absorbent matrix type tube. ETU is recovered from the tube with methylene chloride, the extract is solvent-exchanged to ethyl acetate, and an aliquot of each extract is analyzed by gas chromatography using a nitrogen-phosphorus detector. Twelve laboratories participated in the study. Data were analyzed using a USEPA computer program, which measured recovery and precision for ETU and compared the performance of the method between the 2 water types. Over the concentration range tested, the mean percent recoveries of ETU were 82-92% in reagent water and 85-98% in finished drinking water. The range of the betweenlaboratory relative standard deviations (RSDR) for the 6 concentrations was 5-24% in reagent water, but was only 4-9% in finished drinking water. The range of the within-laboratory relative standard deviations (RSDr) was 6-14% for reagent water and 6- 10% for finished drinking water. Results for the 2 water matrixes showed no statistically significant differences. The method has been adopted first action by AOAC International for determination of ETU in finished drinking waters.
Modified Method for the Determination of Ivermectin Residues in Animal Tissues
Authors: Salisbury Craig D C
Published: February 2020

A simple, reliable method for determining residues of ivermectin in animal tissues is described combining existing sample cleanup procedures for muscle and for feed. Sample extracts are purified on alumina, C18, and silica solid-phase extraction cartridges, and ivermectin is determined by liquid chromatography with fluorescence detection. The average recovery of ivermectin from cattle, swine, and sheep muscle and liver was 87%, in the range of 5-25 ppb. Recovery from fish muscle was 77%, in the range of 5-30 ppb. The detection limit in tissue is 2 ppb.
Rapid Test for Semiquantitative Determination of Nitrate in Forages: Intralaboratory Study
Authors: Jain Anant V
Published: February 2020

A method is described for the semiquantitative determination of nitrate in forages by use of a commercially available test strip. A finely ground sample is extracted with deionized water. The color of the reaction zone on the test strip changes from white to pink or purple depending on the nitrate concentration in sample extract. The color on the test strip is compared with the color scale on the test strip container. An intralaboratory study demonstrated the applicability of the test strip to forages with nitrate concentrations from 200 to >10 000ppm.
Solubility of Antibiotics Used in Animal Feeds in Selected Solvents
Authors: Salvatore Michael J , Katz Stanley E
Published: February 2020

The solubility of antibiotics used in animal feeds in organic solvents was determined. The solubility data could be used in identification of classes and in some cases individual members of the same class of antibiotics, and in differential step(s) in the analysis of these antibiotics. A universal solvent was developed to extract ail antibiotics from animal feeds.
Variability Among Peanut Subsamples Prepared for Aflatoxin Analysis with Four Mills
Authors: Dorner Joe W , Cole Richard J
Published: February 2020

The variability in aflatoxin concentration among peanut subsamples ground with 4 different mills was evaluated. Twenty 2 kg samples of naturally contaminated peanuts were ground in a Dickens subsampling mill (DM), a Stephan model UM-12 vertical cutter mixer (SM), and a Robot Coupe model RSI6Y-1 vertical cutter mixer (RC1). Twenty 4 kg samples were ground in the DM, SM, and a Robot Coupe model R10P vertical cutter mixer (RC2). From each 2 kg sample, ten 100 g subsamples were withdrawn, and from each 4 kg sample, ten 200 g subsamples were withdrawn. Subsamples were analyzed for aflatoxin by liquid chromatography. The coefficient of variation (CV) among each set of 10 subsamples was determined for each sample, and the CVs for each sample size were ranked and analyzed by the Kruskal-Wallis test of ranks. For 2 kg samples, the CVs for the samples ground in RC1 ranked significantly lower than those for samples ground in DM and SM. For 4 kg samples, the CVs for samples ground in RC2 and SM were significantly lower than that for samples ground in DM. The averages of the CVs for 2 kg samples were 17.2% (RC1), 32.8% (SM), and 40.6% (DM). The averages of the CVs for 4 kg samples were 21.2% (RC2), 26.0% (SM), and 47.0% (DM).
Substrate Supporting Disc Method for Confirmed Detection of Total Coliforms and E. coli in all Foods: Collaborative Study
Authors: Feldsine Philip T , Falbo-Nelson Maria T , Hustead David L ,   Collaborators:, Aaronson J , Arling V , Baker M , Bozzuffi J , Bremer N , Chlebowski E , Clarke J , Crane A , Daniell E , Daugherty N , David J , Davis T , Diaz R , Donnelly S , Elwood M , Forgey R , Freshley J , Glowka L , Gottshall R , Graham R , Gray M , Griffith M , Hansen M , Harmon T , Herman R , Hofstrand P , Huether K , Irbys S , Jackey B , Jackson J , Jones T , Khasmakhi A , Lifur L , Linger T , MaCeda J , Mackin M , Marone C , McClure A , McDonagh S , Milligan L , Nelson J , Pandit K , Poole S , Rizzo M , Robinson J , Sparano R , Schriver J , Seibert M , Stone J , Summers D , Sweger L , Tebay D , Vera G , Weaver A , Wempe J , Wilkinson C , Willett J , Willoughby S , Zook T
Published: February 2020

The Coli Complete® substrate supporting disc (SSD) method for simultaneous confirmed total coliform count and Escherichia coli determination in all foods was compared with AOAC most probable number (MPN) methods, 966.23 and 966.24. Twenty-nine laboratories participated in this collaborative study in which 6 food types were analyzed. Four food types, raw ground beef, pork sausage, raw liquid milk, and nut meats, were naturally contaminated with coliform bacteria. Two foods, dry egg and fresh frozen vegetables, were seeded with coliforms. Three food types, ground beef, raw liquid milk, and pork sausage, were naturally contaminated with E. coli. Although pork sausage was naturally contaminated, the level was very low (<10/50 g); therefore, additional E. coli were inoculated into 1 lot of this food type. Three food types, nut meats, dry egg, and fresh frozen vegetables, were inoculated with E. coli. For naturally contaminated samples, duplicate determinations were made on 3 separate lots for each food type. For inoculated samples, low, medium, and high contamination levels plus uninoculated control samples were examined in duplicate. Data were analyzed separately for total coliform bacteria and for E. coli. Mean log MPN counts were determined by the SSD method and the appropriate AOAC MPN method. Results were then analyzed for repeatability, reproducibility, and mean log MPN statistical equivalence. Results were statistically equivalent for all total coliform levels in all food types except frozen vegetable and raw nut meat uninoculated control samples and 1 lot of pork sausage where the SSD method produced statistically significant greater numbers. For the E. coli determinations, results were statistically equivalent across all samples and all levels for each food type. The SSD method has been adopted first action by AOAC International for confirmed detection of total coliforms and E. coli in all foods.
Liquid Chromatographic Determination of Melengestrol Acetate in Feeds
Authors: Campbell Harold M , Sauvé François
Published: February 2020

A method for melengestrol acetate (MGA) was developed to accurately determine 0.08-220 ppm MGA in animal feeds. MGA is extracted from an aqueous slurry of feed sample with hexane and partitioned from hexane into aqueous methanol and then into dichloromethane. After evaporation of the dichloromethane, the dried extract is transferred with chloroform into a volumetric flask. An aliquot is pipetted into a mixed column of silica gel and acid aluminum oxide, and the MGA is eluted with hexane-acetone. The residue is dissolved in methanol, and the MGA is quantitated by reversed-phase liquid chromatography (LC). The method was validated by using commercial feeds and laboratory-fortified feeds. The method was also applied successfully to corn silages supplemented with MGA. Recoveries [and associated coefficients of variation (CVs)] for feeds fortified in the laboratory with MGA 100 at 0.2,0.8, and 5 ppm were 96.9 (6.28), 102 (3.59), and 109% (2.06%), respectively. CVs for a variety of commercial feeds varied from 0.88 to 3.84%. An inter laboratory study was also conducted to compare the LC method to the AOAC gas chromatographic method.
Survey of Total Tetrahydrophthalimide in Baby Foods Using Both Enzyme-Linked Immunosorbent Assay and Gas Chromatography/Mass Spectrometry: A Comparative Study
Authors: Yeung Jupiter M , Newsome W Harvey
Published: February 2020

An enzyme-linked immunosorbent assay (ELISA) method was compared with a gas chromatographic/ mass spectrometric (GC/MS) method for determining the concentration (in parts per million) of the combination of captan and its degradation product tetrahydrophthalimide (THPI) in 13 fruit samples and in a survey of baby foods. Ninety baby foods (49 fruits, 28 juices, and 13 vegetables) from 2 different suppliers were sampled. All captan in the samples was converted to THPI before each analysis. None of the samples contained a concentration of combined captan and THPI that violated the maximum residue limit of 5.0 ppm. Eight samples of baby food tested positive for THPI at levels ranging from 0.019-0.041 ppm by the GC/MS method, whereas 20 samples tested positive in the ELISA assay. All samples that tested positive with the GC/MS method also tested positive with the ELISA method. Thirteen percent of the baby food samples tested false positive with the ELISA method. The ELISA assay also gave higher values than the GC/MS method. The ELISA method can be effectively used as a primary screening tool to select samples testing positive for THPI. The concentration of THPI in these samples can then be verified using the GC/MS method.
Semiautomatic Determination of Furanic Aldehydes in Food and Pharmaceutical Samples by a Stopped-Flow Injection Analysis Method
Authors: Espinosa-Mansilla A , Peña A Muñoz Dela , Salinas F
Published: February 2020

A kinetic study of the reactions of 5-hydroxymethyl-2-furfuraldehyde and furfural with 2-thiobarbituric acid (TBA) by a stopped-flow flow injection analysis technique has been undertaken. A semiautomatic method for the analytical determination of these furanic aldehydes is proposed on the basis of reaction with TBA. The proposed stopped-flow method was successfully applied to several commercial pharmaceutical preparations and food samples. The procedure is faster than the earlier procedure for determination of these compounds in foods and pharmaceuticals.
Variability Associated with Sampling, Sample Preparation, and Chemical Testing for Aflatoxin in Farmers' Stock Peanuts
Authors: Whitaker Thomas B , Dowell Floyd E , Hagler Winston M , Giesbrecht Francis G , Wu Jeremy
Published: February 2020

Forty farmers’ stock lots of runner peanuts suspected of containing aflatoxin were identified by the Federal State Inspection Service by using the visual Aspergillus flavus inspection method. A 900 kg portion was removed from each lot and divided into 50 samples each of 2.27 kg (5 lb), 4.54 kg (10 lb), and 6.81 kg (15 lb) weights. For each sample, foreign material was removed, pods were shelled, and all kernels were comminuted for 7 min in a vertical cutter mixer. A100 g subsample was removed from each comminuted sample for aflatoxin analysis by liquid chromatography (LC). The total variance associated with each sample size was estimated. The total variance was also partitioned into sampling, sample preparation, and analytical variance components. Each variance component was shown to be a function of aflatoxin concentration. By using regression techniques, the relationship between variance and aflatoxin concentration was developed for each variance component. The total, sampling, sample preparation, and analytical variances associated with testing a lot at 100 ppb with a 2.27 kg sample, 100 g subsample, and using LC analytical techniques are 25 378,23 533,1830, and 15, respectively. Sampling, sample preparation, and analysis account for 92.7, 7.2, and 0.1% of the total variability, respectively.
Confirmation of Chloramphenicol Residues in Bovine Milk by Gas Chromatography/Mass Spectrometry
Authors: Kijak Philip James
Published: February 2020

A gas chromatographic/mass spectrometric method was developed to confirm the presence of chloramphenicol (CAP) at 0.5 ng/mL in bovine milk. meta-Nitrochloramphenicol (20 ng) is added to 10 mL milk as a surrogate standard. The milk is mixed with ethyl acetate and then loaded onto a diatomaceous earth-filled, solid-phase extraction (SPE) column; CAP is eluted with additional ethyl acetate. A solution of 4% NaCI in water is added to the eluant, and ethyl acetate is removed by evaporation under a flow of N2. The sample is defatted with hexane and then loaded onto a C18-SPE column. The column is washed with water, and CAP is eluted with methanol. The methanol is evaporated under a flow of N2, and the trimethylsilyl derivative is prepared with Sylon HTP (hexamethyldisilazane–trimethylchlorosilane–pyridine, 3 + 1 + 9). The excess reagent is evaporated under N2, and the residue is taken up in cyclohexane-hexane (60 + 40). CAP is separated on a 30 m × 0.25 mm id methylsilicone column having a film thickness of 0.25 pm and analyzed by methane negative chemical ionization with selected ion monitoring. The ions with m/z 304, 322, 358, 360, 466, and 468 are monitored. Confirmation is based on the presence of 5 ions with relative ion abundances within 10% of that obtained by using standards.
Optimization of a Liquid Chromatographic Method Based on Information Theory: Application of the Method to Dissolution Testing
Authors: Matsuda Rieko , Hayashi Yuzuru , Ishibashi Mumio , Takeda Yasushi
Published: February 2020

The simultaneous optimization of mobile phase composition, column length, detection wavelength, and flow rate was applied to the development of an assay method for dissolution testing of multi-ingredient formulations. This optimization procedure is called Total Chromatographic Optimization and is based on the information theory of chromatography. Optimal chromatographic conditions resulted in very rapid and precise measurements. The dissolution test procedures, including sampling, dilution, filtering, and assay, were performed automatically by a laboratory robotic system. The dissolution medium was sampled every 15 min and analyzed immediately for drug concentration.
Determination and Speciation of Arsenic in Human Urine by Ion-Exchange Chromatography/Flow Injection Analysis with Hydride Generation/Atomic Absorption Spectroscopy
Authors: de Blas O Jimenez , Gonzalez S Vicente , Rodriguez R Seisdedos , Mendez J Hernandez
Published: February 2020

A flow injection–hydride generation/atomic absorption spectroscopic method for the measurement of total urinary arsenic and for the selective determination of inorganic arsenic, monomethylarsonic acid (MMAA), and dimethylarsinic acid (DMAA) was developed. Destruction of the organic matrix is necessary to measure total arsenic content of urine samples. Digestion of this matrix with HNO3–H2SO4–H2O2 is described. The separation of inorganic, monomethylated, and dimethylated arsenic compounds in urine was performed with ion-exchange chromatography on AG 50 W-X8 resin. Detection limits of 2 ppb for each arsenic form and of 3 ppb for total arsenic in urine analyzed after mineralization were found. Recoveries in triplicate urine samples spiked with 10 ppb inorganic arsenic, 20 ppb MMAA, and 40 ppb DMAA were 93, 91, and 85%, respectively. The precision (relative standard deviation) of the method obtained in 10 replicate analyses of urine samples spiked with arsenic metabolites varied from 3.2 to 4.6%. This method is applicable to urine samples in studies relating to arsenic exposure and its monitoring.
Determination of Phenol Pollutants in Water at Trace Levels: Extraction by a Reversible Graphitized Carbon Black Cartridge
Authors: Di Corcia Antonio , Marchese Stefano , Samperi Roberto , Cecchini Giancarlo , Cirilli Luciano
Published: February 2020

A method for determining the 11 phenols designated as priority pollutants by the U.S. Environmental Protection Agency at the parts-per-trillion level in water sampled from the environment is described. Drinking (2 L), ground (1.5 L), and river (0.5 L) water samples are preconcentrated by passing them through a 1 g graphitized carbon black (GCB) reversible cartridge at a flow rate of approximately 70 mL/min. After the GCB cartridge is washed with 1.5 mL methanol to eliminate water, the cartridge is reversed and then back-flushed with an acidic CH2Cl2-CH3OH mixture for eluting phenols. After partial solvent removal, the sample is subjected to reversed-phase liquid chromatography with UV detection by either a conventional or a diode-array detector. Recoveries of phenols added to 2 L of drinking water at levels between 0.05 and 4 μg/L were higher than 90%. Compared with an oc-tadecyl bonded silica (C18) cartridge, the GCB cartridge had a far better extraction efficiency for the more highly water-soluble phenols. The extent to which the presence of fulvic acids in water affected the recovery of the phenols considered was investigated.
Determination of Malachite Green Residues in the Eggs, Fry, and Adult Muscle Tissue of Rainbow Trout (Oncorhynchus mykiss)
Authors: Allen John L , Gofus Jane E , Meinertz Jeffery R
Published: February 2020

Malachite green, an effective antifungal therapeutant used in fish culture, is a known teratogen. We developed a method to simultaneously detect both the chromatic and leuco forms of malachite green residues in the eggs, fry, and adult muscle tissue of rainbow trout (Oncorhynchus mykiss). Homogenates of these tissues were fortified with [14C] malachite green chloride and extracted with 1% (v/v) acetic acid in acetonitrile or in methanol. The extracts were partitioned with chloroform, dried, redissolved in mobile phase, and analyzed by liquid chromatography (LC) with postcolumn oxidation of leuco malachite green to the chromatic form. LC fractions were collected every 30 s for quantitation by scintillation counting. Recoveries of total [14C] malachite green chloride residue were 85 and 98% in eggs fortified with labeled malachite green at concentrations of 0.5 and 1.00 μg/g, respectively; 68% in fry similarly fortified at a concentration of 0.65 μg/g; and 66% in muscle homogenate similarly fortified at a level of 1.00 μg/g. The method was tested under operational conditions by exposing adult rainbow trout to 1.00 mg/L [14C] malachite green chloride bath for 1 h. Muscle samples analyzed by sample oxidation and scintillation counting contained 1.3 and 0.5 μg/g total malachite green chloride residues immediately after exposure and after a 5-day withdrawal period, respectively.
Gas Chromatographic Determination of p-Chloroaniline in a Chlorhexidine Digluconate-Containing Alcohol Foam Surgical Scrub Product
Authors: Gavlick Walter K , Davis Paula K
Published: February 2020

A gas chromatographic (GC) method with flame ionization detection was developed to separate and quantitate p-chloroaniline (PCA) from other components in a chlorhexidine digluconate (CHG)-containing alcohol foam surgical scrub product. A simple sample preparation method was developed in which 1-butanol was used to dissolve the foam and precipitate the CHG, which otherwise would interfere with the GC analysis. The method was validated with respect to linear dynamic range, precision, accuracy, selectivity, limit of detection, and limit of quantitation.
Determination of Honey Authenticity by Anion-Exchange Liquid Chromatography
Authors: Swallow Kevin W , Low Nicholas H
Published: February 2020

Methodology using anion-exchange liquid chromatography with pulsed amperometric detection was developed to determine the addition of invert syrups (beet or cane) and high-fructose corn syrup to honey. The invert syrups used were either chemically (commercially) or enzymatically prepared. Fingerprint oligosaccharides were shown to be present in these sweeteners, which were either not detectable or present at low concentrations in pure honey. Forty-four pure honey samples produced in continental North America, Hawaii, China, and Australia were used in this study.
Spectrophotometric Determination of Decamethrin and Its Residues in Insecticidal Formulations and in Water
Authors: Raju R V Prabhakara , Naidu R Raghava
Published: February 2020

Three spectrophotometric methods were developed for the microdetermination of decamethrin in insecticidal formulations and in water. The methods are based on the hydrolysis of decamethrin with methanolic KOH to 3-phenoxybenzaldehyde; condensation of the hydrolysis product with 2,4- dinitrophenylhydrazine (2,4-DNPH), 4-nitrophenylhydrazine (4-NPH), or 2,4,6-trinitrophenylhydrazine (2,4,6-TNPH) under alkaline conditions; and measurement of the condensates at the absorption maxima of 444,535, and 480 nm, respectively. The relationship between absorbance and concentration was linear in the ranges of 0.1–5.0 μg/mL, 0.5–7.0 μg/mL and 0.1–5.5 μg/mL for 2,4-DNPH, 4-NPH, and 2,4,6-TNPH, respectively. The methods are sufficiently sensitive and can be used to detect decamethrin at concentrations as low as 0.1 μg/mL.
Liquid Chromatographic Determination of Norflurazon and Its Initial Metabolite in Soil
Authors: Willian William T , Mueller Thomas C
Published: February 2020

A rapid, sensitive method for the determination of norflurazon in 4 soils is described. Data on the initial soil metabolite is also obtained in soils with low organic matter. The method consists of extraction of soil samples with methanol, filtration, liquid chromatographic separation of methanol-soluble components by using a C18 column, and fluorescence detection with excitation at 294 nm and emission measured at 398 nm. Recoveries from fortified soils were >90% for norflurazon and >80% for desmethylnorflurazon from the Shipps, Lexington, and Harkey soils. Average percent relative standard deviations over the soils examined was 5.5% for norflurazon and 8.7% for desmethylnorflurazon. The limit of detection for norflurazon was 10 ng/g soil, whereas the limit of detection for desmethylnorflurazon was 100 ng/g soil because of its smaller relative detector response.
Determination of Reserpine in Tablets by Liquid Chromatography with Fluorescence Detection: Revised Procedure
Authors: Cieri Ugo R
Published: February 2020

A procedure is presented for the determination of reserpine in tablets by liquid chromatography (LC) that is a slight modification of a method presented in a previous publication. The sample is extracted with methanol, and solutions are filtered through filter paper. For LC, a 7.5 cm column is used; the mobile phase is methanol containing a small volume of an aqueous solution of the sodium salt of 1-pentanesulfonic acid. Detection is by fluorescence with 280 nm excitation and 360 nm emission. Two commercial samples containing 0.1 and 0.25 mg reserpine were analyzed. For each sample, 2 determinations were made on a ground composite. Ten tablets were also analyzed individually. A linearity study was conducted, with solutions ranging in concentration from 80 to 120% of the amount present in the reference solution.
Determination of Trace Elements in Water by Inductively Coupled Plasma–Mass Spectrometry: Collaborative Study
Authors: Longbottom J E , Martin T D , Edgell K W , Long S E , Plantz M R , Warden B E
Published: February 2020

A joint U.S. Environmental Protection Agency (U.S. EPA)—AOAC interlaboratory method validation study was conducted on U.S. EPA method 200.8, Determination of Trace Elements in Waters and Wastes by Inductively Coupled Plasma–Mass Spectrometry. The purpose of the study was to determine and compare the mean recovery and precision of the inductively coupled plasma–mass spectrometry (ICP–MS) analyses for 20 trace elements in reagent water, drinking water, and groundwater. The formal study was based on Youden’s nonreplicate plan for collaborative tests of analytical methods. The test waters were spiked with the 20 trace elements at 6 concentration levels in the 0.8–200 μg/L range, prepared as 3 Youden pairs. Thirteen collaborators spiked 100 mL aliquots of the test waters, acidified them with 1 mL concentrated HNO3 and 0.5 mL concentrated HCl, reduced the volume to 20 mL by heating in an open beaker at 85°C, refluxed them for 30 min at 95°C, and diluted them to 50 mL. After centrifuging or settling the samples, a 20 mL portion of the supernatant was diluted to 50 mL and analyzed by ICP–MS. Related experiments evaluated the method performance in wastewater and wastewater digestate at a single concentration pair, and an alternative nitric acid digestion procedure. Mean recoveries for reagent water, drinking water, and groundwater were generally 95–105% with between-laboratory relative standard deviations about 4–8%. The method also worked well with wastewaters and digestate, with between-laboratory relative standard deviations averaging 8% and recoveries averaging 100%. Recoveries of silver, however, were low in all matrixes at concentrations over 100 μg/L. The nitric acid digestion procedure was comparable in accuracy and precision to the mixed-acid digestion in U.S. EPA method 200.8. The method was adopted first action by AOAC INTERNATIONAL.
Simultaneous Determination of Organic Acids and Vitamin C in Green Beans by Liquid Chromatography
Authors: Vazquez Oderiz M L , Vazquez Blanco M E , Lopez Hernandez J , Simal Lozano J , Romero Rodriguez M A
Published: February 2020

A method is described for determining and quantitating organic acids (oxalic, malic, citric, and fumaric) and vitamin C by liquid chromatography with a UV–visible detector that allows simultaneous monitoring at 2 wavelengths. The method was applied to samples of green beans (Phaseolus vulgaris L.). Recoveries were 97.8% for oxalic acid, 98.9% for malic acid, 98.7% for citric acid, 99.2% for fumaric acid, and 98.5% for vitamin C. Method precisions (coefficients of variation) were 1.7% for oxalic acid, 0.8% for malic acid, 0.9% for citric acid, 1.5% for fumaric acid, and 1.2% for vitamin C. Measurement precisions (coefficients of variation) were 1.32% for oxalic acid, 0.33% for malic acid, 0.62% for citric acid, 1.01 % for fumaric acid, and 0.39% for vitamin C. Limits of detection were 0.025 mg/mL for oxalic acid, 0.022 mg/mL for malic acid, 0.024 mg/mL for citric acid, 1.0 × 10−4 mg/mL for fumaric acid, and 2.7 × 10−4 mg/mL for vitamin C.
Citrate-Insoluble P2O5: Problems with Ammoniated Fertilizers
Authors: Gliksman Joseph E
Published: February 2020

An AOAC collaborative study of a new direct method for available P2O5 in fertilizer was conducted in 1992. Results on a monoammonium phosphate sample showed more variability than other sample types and also showed the largest absolute difference among the 3 methods compared in the study. Additional study pointed to problems with AOAC method 963.03 for citrate-insoluble
Determination of Ractopamine Hydrochloride in Swine, Cattle, and Turkey Feeds by Liquid Chromatography with Coulometric Detection
Authors: Turberg Michael P , Macy Thomas D , Lewis Jerry J , Coleman Mark R
Published: February 2020

A liquid chromatographic method is described for the determination of ractopamine hydrochloride (LY31537) in swine, turkey, and cattle feeds in the 1.25–100 ppm range and in swine supplement at 100 ppm. Feed samples were extracted with acidified methanol. An aliquot of the feed extract was diluted with water and buffered to pH 10.5 ± 0.5 with sodium carbonate to convert ractopamine hydrochloride to a free base. The free base was extracted from the buffered sample with ethyl acetate. The extract was further purified on an acid-washed, silica solid-phase extraction cartridge. After conversion of the free base back to the salt form with pH 4.5 buffer, analytical separation and quantitation of ractopamine hydrochloride were accomplished on IBM phenyl and Whatman ODS reversed-phase columns with coulometric detection at +600 mV. Mean daily recovery levels ranged from 85 to 100% for feeds fortified at 1.25 to 100 ppm. The coefficients of variation ranged from 1 to 6% for feeds fortified at 2.5 to 100 ppm.
Chloramphenicol Extraction from Milk by Using the Diphasic Dialysis Method Followed by Liquid Chromatographic Determination
Authors: Bayo Javier , Moreno Miguel A , Prieta Javier , Díaz Susana , Suárez Guillermo , Domínguez Lucas
Published: February 2020

An economical, fast, and simple method for the extraction and liquid chromatographic determination of chloramphenicol (CAP) in milk is described. CAP is extracted by using a recently developed membrane-based method named “diphasic dialysis.” CAP is detected and quantitated in the organic solvent used in dialysis without additional cleanup steps by reversed-phase liquid chromatography and UV detection (270 nm). The determination imit of CAP in milk was about 5 μg/L, although as little as 1 μg/L could be detected under optimal working conditions.
Liquid Chromatographic Determination of Furazolidone in Shrimp
Authors: Stehly Guy R , Plakas Steven M , El Said Kathleen R
Published: February 2020

A liquid chromatographic (LC) method was developed for the quantitation of furazolidone residues in shrimp muscle. The shrimp homogenate (1.0 g) is extracted with acetonitrile, and the extract is taken to dryness. The residue is dissolved in acetonitrile, and the solution is passed through alumina and C18 cleanup columns. The eluate is taken to dryness and reconstituted in a suitable solvent for reversed-phase (C18) LC with UV detection at 365 nm. Recoveries of furazolidone from shrimp homogenates spiked from 5 to 80 ng/g ranged from 74.3 to 79.7%, and relative standard deviations (RSDs) were 5.0–8.9%. RSDs for incurred furazolidone quantitated at 5.9 and 9.2 ng/g were 6.6 and 7.6%, respectively.
Determination of Total and Free Sulfite in Unstabilized Beer by Flow Injection Analysis
Authors: Bendtsen Anders Broe , Jørgensen Søren Storgaard
Published: February 2020

The AOAC methods for the determination of total and free sulfite by flow injection analysis (FIA) were modified for the analysis of unstabilized beer. Suggested improvements to the methods include stabilizing the sulfite standards with EDTA, changing the FIA manifold to decrease the system dispersion, and using a nonlinear calibration curve. The modifications are simple to implement and provide a more stable, sensitive, and accurate method. The method for the determination of free sulfite is criticized, because the dynamic range of the method is very limited. Analysis of several beer types showed that none exceeded the regulatory limit of 20 ppm sulfite, but several beers contained sulfite without sulfite being declared as an additive by the manufacturer.
Gas Chromatographic Determination of Polychlorinated Biphenyls in Mussels from Galicia, Spain
Authors: Piñeiro Elena Alvarez , Lozano Jesus Simal , Yusty Asuncion Lage
Published: February 2020

We have modified a standard capillary column gas chromatographic method (U.S. Environmental Protection Agency No. 505) for the determination of polychlorinated biphenyl (PCB) residues and applied the technique to mussels (Mytilus galloprovincialis) from Galicia, Spain. During the purification step, SepPak Florisil minicolumns are used instead of conventional columns. Method performance is good (limit of detection, 0.032 μg/kg; recovery, 99%; method precision as coefficient of variation among 10 samples, 2.5%), and compared with the standard method, less eluant is required and analysis is faster. The mean PCB content of 107 mussels collected from various points on the coast of Galicia was 113 μg/kg.
Rapid Ultraviolet Spectrophotometric Assay of Ibuprofen in Liquid Oral Formulations
Authors: Sanyal Asis K , Laha Dinabandhu
Published: February 2020

A selective and sensitive method was developed for rapid estimation of ibuprofen in complex liquid oral formulations. The method is based on spectrophotometry (352 nm) measurement of iodine released by ibuprofen from an iodide-iodate mixture. Absorbance of liberated iodine was linearly related to ibuprofen at concentrations within the range of 10-40 μg/mL. Ibuprofen was made free from interfering excipients and additives through selective extraction with hexane before assay. The results of ibuprofen determination in a syrup and an oral suspension and of recovery experiments performed on various excipients confirmed the applicability of the proposed method to complex formulations.
Determination of Bronopol, Bronidox, and Methyldibromo Glutaronitrile in Cosmetics by Liquid Chromatography with Electrochemical Detection
Authors: Weyland J W , Stern A , Rooselaar J
Published: February 2020

A method for the simultaneous determination of methyldibromo glutaronitrile, bronopol, and broni-dox in cosmetics, based on liquid chromatography with electrochemical detection, is described. The method is suitable for both aqueous products and emulsions. The detection limit is better than 0.002% for all analytes. Recoveries from an emulsion, spiked to concentrations of 0.03% of the analytes, were 100.4% for bronopol [relative standard deviation (RSD), 0.43%], 97.1% for bronidox (RSD, 0.83%), and 98.4% for methyldibromo glutaronitrile (RSD, 1.7%). Repeatabilities were calculated from 10 replicate analyses of commercial samples. The repeatability for bronopol from an emulsion containing 0.047% bronopol was 0.0027% (RSD, 1.99%); for bronidox from a lotion containing 0.027% bronidox, 0.0014% (RSD, 1.86%); and for methyldibromo glutaronitrile from an emulsion containing 0.031% methyldibromo glutaronitrile, 0.0019% (RSD, 2.16%). A ruggedness test showed that sample amount influenced the results for all 3 analytes. The results obtained for bronidox also depended on detection parameters and composition of extraction solvent. The method was applied to 138 cosmetic products and performed trouble free during these analyses. Bronopol was found in 14 samples, and bronidox was found in 4 samples, including a baby hair lotion, in which it is prohibited. Methyldibromo glutaronitrile was present in 27 samples, including creams, lotions, and sun protection cosmetics.
Graphite Furnace Atomic Absorption Method for the Determination of Lead in Sugars and Syrups
Authors: Miller-Ihli Nancy J
Published: February 2020

A method was developed for the determination of lead in sugars and syrups. Samples are wet-ashed with a nitric acid–hydrogen peroxide procedure and analyzed by graphite furnace atomic absorption spectrometry. The method involves the use of magnesium nitrate as a matrix modifier, air ashing, platform atomization, and quantitation by peak area measurements with direct calibration against aqueous standards. The instrumental detection limit (based on 3.29σ) was 10 pg, or 0.5 μg/L for a 20 μL injection, corresponding to a method detection limit of 3.3 ng/g sugar. The characteristic mass was approximately 12 pg. This method was validated by analyzing sucrose and high-fructose corn syrup samples spiked with known quantities of lead. The average recovery was 101 ± 6%.
Hydrolysis of Peptide Binding by Phosphotungstic Acid
Authors: Fialaire Anne , Postaire Eric
Published: February 2020

A new method for the precipitation of protein and oligopeptides is described. In this method, the selectivity of precipitation is a function of the percentage of alcohol. With an 80:20 (v/v) mixture of ethanol and water at room temperature, the selectivity of oligopeptide precipitation was as good as that using phosphotungstic acid.
Liquid Chromatographic Determination of Ivermectin in Feed at the 2-PPM Level: Interlaboratory Study
Authors: Fink David W
Published: February 2020

An analytical method for the determination of ivermectin in feed at the 2 ppm level was evaluated in an interlaboratory study involving 4 laboratories. The method is based on liquid chromatographic measurement following sample preparation by adsorption chromatography on alumina and solid-phase extraction techniques. Each laboratory analyzed 2 complete, final, finished medicated feeds and the corresponding control feeds used in their preparation. In addition, they also measured recoveries in fortified feeds covering 50–150% of the 2 ppm ivermectin use concentration. The mean recoveries from the replicate analyses reported by the laboratories ranged from 90 to 110% and all coefficients of variation (CVs) were less than 4.5%. No significant interferences were found in the control feeds. The pooled distribution of all the individual analytical results (n = 100) gave a mean recovery of 100%, a recovery range of 90–111%, and an overall CV of 5.5%. Resolution of the total variance into its 2 components gave a withinlaboratory CV of 4.1% and a between-laboratories CV of 3.4%. There was no significant difference in recoveries among laboratories, days, concentrations, and feed base or between fortified and medicated feeds (P > 0.2).
Rapid Analysis of Animal Drug Residues by Microcolumn Solid-Phase Extraction and Thermal Desorption–Ion TYap Mass Spectrometry
Authors: Barshick Stacy-Ann , Buchanan Michelle V
Published: February 2020

A new approach was developed for the rapid and quantitative determination of an anthelmintic drug, phenothiazine, in milk. The technique involves a simple extraction procedure using a C18 microcolumn disc, followed by thermal desorption of the analyte from the disc directly into an ion trap mass spectrometer. The compounds are selectively ionized by isobutane chemical ionization and detected by tandem mass spectrometry. With this approach, 10 ppb detection limits were achieved with as little as 100 μL milk and only 10 min of analysis time. This approach was used to analyze samples of milk taken from a cow administered a one-time therapeutic dose of phenothiazine. The target compound could be detected at 56 h post-dosage, corresponding to a concentration of 30 ppb.
Determination of Musk Ambrette in Fragrance Products by Capillary Gas Chromatography with Electron Capture Detection: Interlaboratory Study
Authors: Wisneski Harris H , Yates Ronald L , Havery Donald C
Published: February 2020

A gas chromatographic method that uses an internal standard additions technique is described for the determination of musk ambrette (MA) in fragrance products. A solution containing the product and a known amount of an internal standard, musk tibetene (MT), is injected directly into a gas chromatograph equipped with an electron capture detector. The chromatographic separation of the components on a wide-bore fused silica capillary column is recorded and a response constant is calculated from MA and MT peak heights. A similar response constant is also calculated for a standard solution containing known concentrations of MA and MT. The MA content of the fragrance product is then calculated. Average recoveries of MA from fragrance products ranged from 97.6 to 102.3%. The method was also evaluated collaboratively by 6 laboratories. In this study, the reproducibility relative standard deviation for MA in 6 fragrance test samples ranged from 2.78 to 22.87%.
Determination of Nitrate in Vegetables by Continuous Flow: Interlaboratory Study
Authors: Beljaars Paul R , Duk Remmelt Van , Van Der Horst Geertrutoa M
Published: February 2020

A collaborative study for the determination of nitrate in leafy vegetables, such as endive, lettuce, spinach, and beetroot, by continuous flow (CF) was conducted by the Project Group on Collaborative Studies of the Inspectorate for Health Protection, Food Inspection Service, in The Netherlands. After extraction with water and filtration, samples were cleaned up by dialysis in the CF system. Extracted nitrates were reduced to nitrite in the system by metallic cadmium, and then the nitrite was reacted with sulfanilamide and N-naphthylethylenediamine to form a reddish-purple azo dye. This dye was measured colorimetrically at 530 nm. Fourteen vegetable samples (including 7 blind duplicates) containing nitrate at ca 900 to 5200 mg/kg were analyzed singly by the proposed procedure by 13 laboratories. The data were analyzed by the International Union for Pure and Applied Chemistry (IUPAC)–International Organization for Standardization (ISO)–AOAC protocol for statistics. One collaborator was identified as an outlier for all results. For all samples analyzed, the repeatability relative standard deviation values varied from 1.7 to 5.5%, whereas the reproducibility relative standard deviation values ranged from 3.3 to 5.9%.
Decreasing the Number of Points in the Standard Curve for Determining Iron in Flour: Summary of Collaborative Study
Authors: Martin James I , Soliman Abdel M
Published: February 2020

Seven laboratories participated in a collaborative study conducted to (1) evaluate the effects of reducing the number of points for the standard curve in the AOAC Official Method for iron in flour 944.02A–944.02C(a) from 10 points to 5 points, and (2) compare the levels of iron found in foods by using the 10-point and 5-point standard curves. The 5 points (0.2,0.6,1.0,1.4, and 1.8 μg Fe/mL) were selected by eliminating every other standard point from the 10-point curve after correction for the reagent blank. No differences in the performance parameters between method versions were found when blind duplicate analysis was used to estimate the performance parameters for each sample analyzed. Results from 2 laboratories were excluded from statistical calculations because of failure to follow the specific instructions to increase the dilution when sample absorbance readings exceeded the highest standard point reading. The 5-point standard curve has been adopted first action in method 944.02 by AOAC INTERNATIONAL.
Liquid Chromatographic Determination of the Anticoccidial Drug Halofuginone Hydrobromide in Eggs
Authors: Holland David C , Munns Robert K , Roybal Jose E , Hurlbut Jeffrey A , Long Austin R
Published: February 2020

A liquid chromatographic (LC) method is described for the determination of 5-100 ppb halofuginone hydrobromide (HFG) in eggs. HFG as the free base is extracted from eggs with ethyl acetate. The extract is cleaned up on an acidic Celite 545 column. A Waters C18 column is used for LC separation with UV determination at 243 nm. The isocratic mobile phase is a mixture of water-acetonitrile-ammonium acetate buffer (12 + 5 + 3) and acetic acid. The interassay average recovery from eggs was 90.4%, with a standard deviation of 5.11 and a relative standard deviation of 5.65%.
Enzymatic Determination of Free Carnitine in Milk and Infant Formulas
Authors: Indyk Harvey E , Woollard David C
Published: February 2020

A simple spectrophotometric assay for free carnitine in milk and supplemented infant formulas has been developed. After acid extraction, carnitine is measured enzymatically through its reaction with carnitine acetyltransferase coupled with acetyl coenzyme A and dithiobenzoate (DTNB). The manually performed method is rapid, accurate, and convenient for routine quality-control analysis of infant formulas. The chemistry is also suitable for automation, for greatly enhanced throughput.
Liquid Chromatographic Determination of Benzoic Acid in Orange Juice: Interlaboratory Study
Authors: Lee Hyoung S
Published: February 2020

An interlaboratory study was carried out for the determination of benzoic acid in orange juice by liquid chromatography. The orange juice was fortified with 0.5–10 ppm benzoic acid. Statistical analysis of the results showed that relative reproducibility (RSDR) between laboratories ranged from 6.92 to 15.97% for juice fortified with 1-10 ppm benzoic acid; RSDr was 27.90% for juice fortified with 0.5 ppm benzoic acid. Mean recoveries ranged from 94.5% for 4 ppm benzoic acid to 114% for 0.5 ppm benzoic acid. Total variability increased with increasing fortification level as measured by standard deviation for reproducibility (SR).
Determination of Organochlorine Pesticides in Cheese
Authors: Bentabol Antonio , Jodral Manuela
Published: February 2020

A multiresidue technique was developed for the analysis of 17 organochlorine compounds in cheese: α-hexachlorocyclohexane (α-HCH), β-HCH, γ-HCH, δ-HCH, aldrin, dieldrin, endrin, heptachlor, heptachlor epoxide, chlordane, o,p′-…(o,p′-DDT), p,p′-DDT, o,p′-…(o,p’-DDD), p,p′-DDD, o,p’-… (o,p′-DDE), p,p′-DDE, and the fungicide hexachlo-robenzene. In this technique, the fat, previously extracted from the cheeses, was subjected to 2 cleanup and extraction methods: with H2SO4, for acid-resistant organochlorine pesticides, and with KOH-ethanol. The behavior of the compounds in both treatments enabled us to identify the organochlorine pesticides in cheese. The precision (repeatability and reproducibility) and accuracy of the technique were validated.
Low-Temperature Decomposition of Botanical and Biological Samples for Multielement Analysis by High-Frequency Induced Oxygen–Argon–Fluorine Plasma
Authors: White Ralph T , Lawrence Christopher W
Published: February 2020

The cool plasma asher (CPA) consists of a high-frequency generator and a quartz sample vessel equipped with a cooling finger that prevents loss of volatile elements. After sample decomposition within an O2–Ar–F plasma, the ashing residues and the elements condensed on the surface of the vessel or cooling finger are dissolved by refluxing in 1–5 mL of double-distilled acid. The sample solutions are analyzed for elemental content by inductively coupled plasma-atomic emission spectrometry (ICP–AES). The recovery values for 42 elements (Ag, Al, As, B, Ba, Be, Bi, Ca, Cd, Co, Cr, Cu, Eu, Fe, Hg, K, Li, Mg, Mn, Mo, Na, Ni, P, Pb, Pd, Pt, Rb, S, Sb, Se, Sn, Sr, Te, Ti, V, Y, Yb, Zn, Zr, La, Au, and Sc) are documented after cool plasma ashing of elemental spectrometric standards. In addition, NIST Standard Reference Materials consisting of botanical and biological samples are ashed by CPA, and results are reported for 23 elements (Al, As, Ba, Be, Ca, Cd, Co, Cr, Cu, Fe, K, Li, Mg, Mn, Na, Ni, P, Pb, S, Se, Sr, V, and Zn) analyzed by ICP-AES. This method achieves good recoveries for many elements while allowing decomposition of difficult sample matrixes without acid, at a temperature slightly above 100°C. We investigated several ashing facilitators to improve ashing efficiency. This paper describes improved ashing conditions due to sample agitation, gas mixtures, Teflon balls, and a Teflon vessel. The time required to ash 1.0 g of botanical sample in the CPA was reduced from 80 h with no ashing aids to 3 h with maximum ashing aids. The optimum plasma ashing conditions for 1.0 g of sample was 6 h at a high-frequency power of 30 W with a 1 h acid reflux to dissolve sample ash. Because reflux acid in the final sample volume was minimal, trace elemerits were concentrated and blank contamination was extremely low.