bluuebunny/crossref_metadata_2025 huggingface dataset:
Determination of Biogenic Amines in Cheese
Authors: Vale Silvana R , Glória M Beatriz A
Published: February 2020

A liquid chromatographic (LC) procedure for determining 10 biogenic amines in cheese is described. The method is based on ion-pair chromatography on a reversed-phase column with postcolumn derivatization with o-phthaldialdehyde and fluorometric detection. It allowed simultaneous determination of 10 amines in <80 min: histamine, tyramine, tryptamine, 2-phenylethylamine, serotonin, agmatine,spermine, spermidine, putrescine, and cadaverine. Linearity for each amine was observed between 0.5 and 6.0 μg/mL. Detection limits ranged from 0.004 to 0.009 μg/20 μL, and determination limits ranged from 0.066 to 0.149 mg/100 g. Amino acids and other amines did not interfere with determination of biogenic amines. Three extractantsmethanol, hydrochloric acid, and trichloroacetic acidwere compared in their efficiency to recover aminesfrom spiked samples. Purification of the cheese extract was required prior to LC to avoid interference from compounds in the cheese matrix. Hydrochloric acid extraction followed by purification with diethyl ether gave best recoveries for all the amines (75.5-112.3%). The method is simple, fast, and reliable. It can be used to study the technological and toxicological implications of biogenic amines in cheeses.
Comparison of Methods and Kits for Colorimetric Determination of Residual Chlorine in Water
Authors: Serrat F Bosch , Morell G Bosch , Polo D Rodriguez
Published: February 2020

The use of 3,3',5,5'-tetramethylbenzidine (TMB) for residual chlorine determination in water offers 2 possibilities, one at pH 1-2 and absorbance measurement at 450 nm and another at pH 3.8-5.8 and measurement at 650 nm. The reaction of chlorine with TMB reaches its maximum sensitivity at pH 1-2. The detection limit is 2 ng/mL. A calibrated scale for colorimetric determination of residual chlorine in water with 3,3',5,5'-tetramethylbenzidine (TMB), prepared with tropaeolin O (C.I. 14270), is described. This scale is stable for several months and can be useful in replacing the conventional and much less stable scale prepared from standard solutions of oxochlorate (I). Kits for determination of residual chlorine in water by visual comparison, including a 3-dimensional scale or a color scale printed on paper or a plastic material, are described in this article. A comparative study of the analytical qualities and applications of the TMB methods against other reagents methods is performed.
Comparison of Environmental Chemical Results for Split Samples Analyzed in Different Laboratories
Authors: Grant Clarence L , Jenkins Thomas F , Mudambi Anand R
Published: February 2020

Data comparisons were made for split or co-located samples analyzed in contract laboratories and quality assurance (QA) laboratories during environmental studies directed by the U.S. Army Corps of Engineers. Archived results were analyzed statistically as concentration ratios (contract laboratory/QA laboratory). Concentration ratios were found to be lognormally distributed, and this was the model used for comparisons. For metals in soils and volatile organic compounds (VOCs) in groundwater, 10.2% of metal ratios in soils and 5.6% of VOC ratios in groundwater exceeded limits of 0.40-2.50. Considering that both methods are multianalyte, we find that only 4.0% of the metal samples and 2.0% of the VOC samples had more than one outlier ratio per sample. More recent data produced very similar results. For VOCs, total petroleum hydrocarbons (TPHs), and explosives in soils, limits of 0.25-4.00 are suggested with the understanding that large improvements are badly needed. Even with these wide limits, approximately 42% of VOCs, 14% of TPHs, and 11% of explosives contract laboratory/QA laboratory ratios were outside these limits. Here, too, the most recent data yielded very comparable results. Sampling and preparation procedures for VOCs in soils requires immediate attention, but all methods can and should be capable of producing improved agreement between laboratories.
Quantitation of Penicillin G in Medicated Premix Feeds by Micellar Electrokinetic Capillary Chromatography
Authors: Cutting Jeffrey H , Hurlbut Jeffrey A , Sofos John N
Published: February 2020

A micellar electrokinetic capillary chromatographic (MECC) method for quantitation of penicillin G in medicated premix feeds was compared with the A0AC microbiological cylinder plate method. Feed was extracted according to the AOAC method, enabling comparison of both methods with the same extract. The MECC method detected penicillin G within 20 min, using a 150 mM sodium dodecyl sulfate (SDS)-20 mM sodium borate run buffer and a UV photodiode array detector at 210 nm. Recoveries from 5 replicates of medicated feed containing 117 g penicillin G/kg and then spiked to give a concentration of 176 g/kg were 98.4-108%, with a relative standard deviation (RSD) of 3.76% for the MECC method, and 102-104% with RSD of 1.06% for the AOAC microbiological cylinder plate method. Using a 5-point calibration curve, the MECC method detected and quantitated penicillin G in medicated premix feeds within 3 h, versus 24 h for the AOAC microbiological cylinder plate method.
Assay of Chlortetracycline in Animal Feeds by Liquid Chromatography with Fluorescence Detection
Authors: Houglum Joel E , Larson Richard D , Knutson Ann
Published: February 2020

A liquid chromatographic (LC) method is described to assay chlortetracycline (CTC) at gram-per-ton and gram-per-pound levels. Feeds and premixes are extracted with acid-acetone following AOAC Method 957.23B(h). Extracts are filtered and quantitated by LC using a Ciβ column and fluorescence detection at 390 nm excitation and 512 nm emission. The mobile phase (1.5 mumin) uses a methanol gradient with an initial hold time of 5 min at 35% methanol followed by an increase to 60% methanol over 8 min. The aqueous component contains CaCI2, disodium EDTA, and sodium acetate buffered to pH 6.5. The method provides significant improvement in selectivity and limit of quantitation compared to LC with UV detection. Recovery of spiked samples averaged 98.1% and assay of samples correlated closely with the results obtained with AOAC microbiological Method 967.39. CTC and epi-CTC eluted at approximately 12.5 and 4.0 min, respectively. No interference was observed from several drugs and other antibiotics often used in combination with CTC in feeds.
Determination of Pirlimycin Residue in Milk by Liquid Chromatographic Analysis of the 9-Fluorenylmethyl Chloroformate Derivative
Authors: Heller David N
Published: February 2020

A procedure to determine pirlimycin residues in bovine milk was developed. Pirlimycin was extracted from milk after protein precipitation and 2 stages of liquid–liquid partitioning. The extract was evaporated to dryness, redissolved in dilute base, and derivatized with 9-fluorenylmethyl chloroformate (Fmoc) to impart a chromophore for ultraviolet (UV) detection. The derivatized extract was analyzed by reversed-phase liquid chromatography (LC). Pirlimycin concentration was calculated from the peak height of the extract by using a linear regression standard curve prepared from a series of derivatized standards. The procedure's performance in the range of the regulatory tolerance (0.4 ppm) was validated by replicate analysis of control, fortified control, and residue-incurred bovine milk. Average recoveries at 0.2, 0.4, and 0.8 ppm were 91, 88, and 87%, respectively, and coefficients of variation were 5,4, and 1%, respectively. Overall recovery for all samples was 89%, with 4% coefficient of variation. Linear regression analysis of LC/UV results versus results from a previously published LC/mass spectrometric assay gave a slope of 0.95, with a correlation coefficient of 0.98.
Analysis of Aflatoxins in Poultry and Pig Feeds and Feedstuffs Used in Colombia
Authors: Céspedes Angel E , Diaz Gonzalo J
Published: February 2020

Feedstuffs and mixed feeds used for poultry and pig nutrition in Colombia were analyzed for aflatoxins by using a liquid chromatographic technique with a limit of detection of 1 μg/kg for each aflatoxin (B1, B2, G1 and G2). Samples of grain sorghum, maize, processed soybean, rice meal, cottonseed meal, and poultry and pig feeds, representative of Colombian production for the 1995–1996 harvest, were taken from feed-manufacturing plants in various cities. Aflatoxins were detected in 11 of 45 samples of sorghum, 4 of 33 samples of maize, 8 of 22 samples of rice meal, 15 of 17 samples of cottonseed meal, 1 of 12 samples of other feedstuffs, 12 of 30 samples of poultry feed, and 7 of 16 samples of pig feed. Aflatoxins were not detected in soybean. Only 9 of 58 positive samples contained total aflatoxin levels exceeding maximum tolerable limits in Colombia.
Determination of Tolclofos-Methyl in Soil and Lettuce by Gas Chromatography
Authors: Gennari Mara , Cignetti Alessandro , Négre Michéle
Published: February 2020

Two simple methods for the determination of tolclofos-methyl in soil and lettuce are presented. Soil samples were extracted with a methanol–water solution (9 + 1, v/v). The extract was cleaned up on a LC C18 SPE cartridge. The method was tested on 4 soils having very different physico-chemical characteristics and gave recoveries > 70% and a determination limit of 0.02 mg/kg soil. Lettuce samples were extracted with n-hexane. The extract was cleaned up on florisil SPE cartridges. The recoveries were > 83% and the determination limit was 0.01 mg/kg lettuce.
Fully Automated Determination of Pesticides in Wine
Authors: Kaufmann Anton
Published: February 2020

A fully automated solid-phase extraction gas chromatographic/mass spectrometric (SPE/GC/MS) method was developed for determination of pesticides in wine. All steps from aspiration of infiltrated wine to printout of the integrated chromatogram were performed without human interaction. A dedicated robot performed addition of internal standard, application of wine onto the SPE cartridge, elution of analytes, drying and concentrating of eiuate, and passing of concentrate to the GC sampler. All steps were performed in standard liquid chromatography/GC vials, using a minimum of organic solvent. The method permits determination of 21 different pesticides. Individual detection limits were 0.005–0.01 mg/L. The regression coefficients relating to linearity were > 0.99; only 4,4-dichloro-benzphenone and dicofol showed lower coefficients. The recoveries for 17 pesticides ranged from 80 to 115%.
Evaluation of Materials as Bacterial Spore Carriers for Testing Disinfectants
Authors: Gangi Victor J , Leonard Ira E , Rodriguez Allison A , Margolin Aaron B
Published: February 2020

Prototype objects made of steel, glass, and various polymers were evaluated in relation to currently used objects made of silk suture and porcelain for their use as bacterial spore carriers for testing the sporicidal activity of disinfectants. The carriers were inoculated with spores of Bacillus subtilis. Spore retention was determined by detachment from the carriers by sonication and rinsing. Inoculated carriers were exposed to 2.5N HCI and 2.5% glutaraldehyde solutions to determine the effect of carrier material on spore inactivation. Carriers with the highest and lowest spore retention were steel-silicone mix carriers (1.7 × 106 spores/carrier) and polyvinylchloride cylinders (3.8 × 105 spores/carrier), respectively. Spore adhesion to carrier objects was not directly proportional to carrier surface area. Spores on silk sutures, grooved steel, and Teflon carriers survived longest in HCI solution. Spores on Teflon, grooved stainless steel, and glass cylinders survived longest in glutaraldehyde solution. In chemical and spore adhesion tests, no significant statistical differences were found between novel carrier materials and current spore carrier materials. The methods used for evaluating carrier materials were reliable and repeatable.
Spectrophotometric Determination of Pyridoxine Hydrochlorine in Pharmaceutical Preparations and Foods
Authors: Srtvidya Kailasam , Balasubramanian Natesan
Published: February 2020

An easy and sensitive spectrophotometric assay of pyridoxine is described. The procedure is based on formation of an azo dye by the reaction of pyridoxine with diazotized 2,4-dinitroaniline followed by the reaction of the dye with Hg2+ ions to form a stable complex with maximum absorbance at 545 nm. The system obeys Beer’s law for 4–75 μg pyridoxine hydrochloride in an overall aqueous volume of 25 mL (correlation coefficient, 0.9998). On extraction into 5 mL butan-1-ol, the system obeys Beer’s law in the range 0.8–15 μg pyridoxine hydrochloride at 545 nm. The color is stable for 60 min in both aqueous and organic phases (molar absorptivity, 3.7 × 104 L/mol · cm; coefficient of variation, 3.1%, n = 10). The pyridoxine contents of pharmaceutical preparations, a processed foodstuff, and 2 rice samples were determined by using the proposed method. Assay reliability was established by recovery studies and parallel determination using a reported method.
A Comparison of Statistical and Empirical Detection Limits
Authors: Su George C C
Published: February 2020

Quantitatable detection limits for 43 diverse analytes analyzed by a variety of analytical methods determined by 2 statistical methods and one empirical method were compared. One statistically derived quantitatable detection limit is the U.S. Environmental Protection Agency's minimum level (ML), which is 10 times the standard deviation of replicates of a single concentration or 3.18 times the method detection limit (MDL). The other statistical method is the alternate minimum level (AML), which is based on statistical calculations of replicates of multiple concentrations but places more weight on the lower concentrations. The empirical method is based on the analysts' experience with actual samples. All 3 approaches agree to within a factor of 5 nearly 70% of the time. This agreement suggests an uncertainty factor of 5 for laboratory analysis at the lowest concentrations at which instruments can perform quantitative analysis. The results also show that both statistical methods probably adequately account for normal matrix effects.
Examining the Origin of Melatonin from a "Natural" Source by Isotope Ratio Mass Spectrometry with Liquid Chromatographic Introduction
Authors: Chen Pei , Osborn Blaire L , Abramson Ferd p
Published: February 2020

The isotopic abundance of 13C often can be used to differentiate between natural and synthetic sources of a given material. These differences are small, and a multicollector isotope ratio mass spectrometer (IRMS) is required. In our laboratory, we developed a liquid chromatographic (LC) introduction system that enables continuous monitoring of 13C isotope ratios for nonvolatile materials without derivatization. The particular question being asked here relates to the source of melatonin in products sold in health food stores. Melatonin is a pineal hormone and its natural source is the brain's pineal gland. The increasing frequency of "mad cow disease" points to a potential danger if bovine pineals were really the source of melatonin in health food preparations. Using a system in which an LC system is interfaced to an IRMS, we evaluated the origin of one melatonin product labeled as being of bovine pineal origin by comparing its 13C/12C ratio to those of pure, synthetic melatonin and 2 other melatonin products labeled as being of synthetic origin. We did not find significant differences among the isotope ratios of these 4 melatonin sources. The finding suggests that bovine pineal melatonin is not present in the product labeled as "natural." The work demonstrates the ability of an apparatus combining LC and IRMS to provide detailed information regarding economic adulteration or fraud.
Estimating Aflatoxin in Farmers' Stock Peanut Lots by Measuring Aflatoxin in Various Peanut-Grade Components
Authors: Whitaker Thomas B , Hagler Winston M , Giesbrecht Francis G , Dorner Joe w , Dowell Floyd E , Cole Richard J
Published: February 2020

Five, 2 kg test samples were taken from each of 120 farmers' stock peanut lots contaminated with aflatoxin. Kernels from each 2 kg sample were divided into the following grade components: sound mature kernels plus sound splits (SMKSS), other kernels (OK), loose shelled kernels (LSK), and damaged kernels (DAM). Kernel mass, aflatoxin mass, and aflatoxin concentration were measured for each of the 2400 component samples. For 120 lots tested, average aflatoxin concentrations in SMKSS, OK, LSK, and DAM components were 235, 2543, 11 775, and 69 775 ng/g, respectively. Aflatoxins in SMKSS, OK, LSK, and DAM components represented 6.9, 7.9, 33.3, and 51.9% of the total aflatoxin mass, respectively. Cumulatively, 3 aflatoxin risk components—OK, LSK, and DAM—accounted for 93.1% of total aflatoxin, but only 18.4% percent of test sample mass. Correlation analysis suggests that the most accurate predictor of aflatoxin concentration in the lot is the cumulative aflatoxin mass in the high 3 risk corn ponents OK + LSK + DAM (correlation coefficient, r = 0.996). If the aflatoxin in the combined OK + LSK + DAM components is expressed in concentration units, r decreases to 0.939. Linear regression equations relating aflatoxin in OK + LSK + DAM to aflatoxin concentration in the lot were developed. The cumulative aflatoxin in the OK + LSK + DAM components was not an accurate predictor (r = 0.539) of aflatoxin in the SMKSS component. Statistical analyses of 3 other data sets published previously yielded similar results.
Determination of Trace 2,4-Dichlorophenoxyacetic Acid in Fresh Produce by Gas Chromatography with Boron Trichloride/2- Chloroethanol Derivatization
Authors: Ting Keh-Chuh , Kho Peng K
Published: February 2020

2,4-Dichlorophenoxyacetic acid (2,4-D) residues in fresh produce is officially analyzed as its methyl ester form by gas chromatography with electron capture detection (GC-ECD). Because of safety concerns with diazomethane, the reagent used to form methyl esters, a less toxic and dangerous reagent, BCI3/2-chloroethanol, was considered. With this alternative reagent, the detecting product is a 2-chloroethyl ester. Compared with the methylester, the 2-chloroethylester has a longer retention time and a better signal-to-noise ratio for trace level analysis by GC-ECD. However, the reagent produces too many unwanted background peaks. If peak retention time is the only information available to identify the residue in case of litigation, the presence of too much background noise increases the ambiguity of identification. Therefore, confirmation by interpretation of the mass spectrum and determination of the compound structure is necessary to ensure the validity of the method. Ten commodities were fortified with 2,4-D at 0.1 ppm. Recoveries of 2-chloroethyl esters and methyl esters were 91 and 92%, respectively. The method is safe, simple, and robust.
Simultaneous Liquid Chromatographic Analysis of the β-Lactam Antibiotics Cefazolin, Cefadroxil, Cephalexin, Ampicillin, and Cephradine in Solution
Authors: Farag Shawky A
Published: February 2020

abstract

A liquid chromatographic method was developed for the determination of nanogram quantities of 5 broad-spectrum structurally related β-lactam antibiotics (cefazolin, cefadroxil, cephalexin, cephradine, and ampicillin) in solution. The method uses a C18 reversed-phase column, UV absorption (240 nm) detection, and an aqueous mobile phase containing isopropyl alcohol and acetic acid. Relative resolution between the antibiotic peaks ranged from 1.7 to 5.9 for all peaks. Chromatographic retention times were 2.97, 3.92, 4.57, 5.37, and 6.56 min for cefazolin, cefadroxil, cephalexin, ampicillin, and cephradine, respectively. Accuracy, precision, linearity, and long term analytical reproducibility were determined by statistical analysis. Use of the proposed method to evaluate the degradation of cephradine solutions stored at room temperature illustrated its potential as a stability-indicating assay.
Optical Immunobiosensor Assay for Determining Enrofloxacin and Ciprofloxacin in Bovine Milk
Authors: Mellgren Catarina , Sternesjö Åse
Published: February 2020

abstract

A rapid, sensitive optical immunobiosensor assay was developed and used to determine enrofloxacin and its main metabolite, ciprofloxacin, in milk from healthy cows and cows with clinical signs of mastitis after intramuscular administration of enrofloxacin. Liquid chromatography (LC) was used to confirm results of the biosensor assay. Despite incomplete cross-reactivity between polyclonal enrofloxacin antibodies and ciprofloxacin, the biosensor assay could be used for semiquantitative analysis of the sum of the 2 substances. LC analysis showed that ciprofloxacin persisted at levels exceeding the expected future maximum residue limit in milk for several days after the end of the withdrawal period.
Comparison of Monolayer and Bilayer Plates Used in Antibiotic Assay
Authors: Reamer Richard H , Dey Bhabani P , White Clarence A , Mageau Richard p
Published: February 2020

abstract

Standard curves of 5 antibiotics were determined in an antibiotic assay using bilayer and monolayer agar plates and AOAC-specified test organisms and agar media. Micrococcus luteus ATCC 9341a and antibiotic medium No. 2 were used to prepare the penicillin G standard curve. The same organism and antibiotic medium No. 11 were used to prepare the erythromycin standard curve. Standard curves for streptomycin, tetracycline, and gentamicin were prepared, respectively, with antibiotic medium No. 5 and Bacillus subtilis ATCC 6633, antibiotic medium No. 8 and B. cereus ATCC 11778, and antibiotic medium No. 11 and Staphylococcus epidermidis ATCC 12228. Assays of inhibition by meat fortified with penicillin, streptomycin, gentamicin, tetracycline, erythromycin also were performed on monolayer and bilayer plates. Differences in standard curves and inhibitory responses obtained with monolayer and bilayer plates were <10%. Thus, monolayer plates are acceptable for use in analyses of meat and poultry for antibiotics residues, with savings in laboratory resources and time.
One-Step Solid-Phase Extraction Cleanup and Fluorometric Analysis of Deoxynivalenol in Grains
Authors: Malone Bruce R , Humphrey Craig W , Romer Tom R , Richard John L
Published: February 2020

abstract

A rapid, quantitative, inexpensive, efficient method was developed to determine deoxynivalenol (DON) in wheat, barley, corn, wheat middlings, wheat flour, bran, malted barley, and oats. Samples are ground and extracted with acetonitrile-water (86 + 14). A portion of the extract is cleaned up by passage through a MycoSep No. 225 column, evaporated to dryness, and derivatized with zirconyl nitrate and ethylenediamine in methanol. The resulting fluorescent derivative of DON is identified and quantitated with a calibrated fluorometer containing a broad wavelength pulsed xenon light source. This method quantitated DON concentrations from 0.5 to 50 ppm without dilution and was linear when applied to samples of noncontaminated wheat spiked at 0.5, 5, 10, 25, and 50 μg DON/g. Correlation coefficients of the method with LC for multiple analyses (n ≥ 14 for each commodity) applied to wheat, corn, barley, wheat flour, and wheat middlings were 0.99, 0.99, 0.99, 0.93, and 0.98, respectively. Individual analyses were conducted in < 30 min, and 24 samples were analyzed in 2 h.
Determination of Residues of Flumequine and 7-Hydroxyflumequine in Edible Sheep Tissues by Liquid Chromatography with Fluorimetric and Ultraviolet Detection
Authors: Delmas Jean-michel , Chape Anne-marie , Sanders Pascal
Published: February 2020

abstract

A simple, sensitive, and rapid method for simultaneous determination of residues of flumequine and its microbiologically active metabolite 7-hydroxyflumequine in 100 mg sheep edible tissues (muscle, liver, kidney, and fat) by liquid chromatography is reported. After liquid-liquid cleanup with ethyl acetate, tissue extracts were injected onto a Select B column. The 2 compounds were determined by ultraviolet and fluorimetric detection. The method was repeatable and reproducible for flumequine and 7-hydroxyflumequine in muscle, liver, kidney, and fat, with limits of detection below 2 and 3 μg/kg for flumequine and 7-hydroxyflumequine, respectively. Mean recoveries for flumequine were 90 ± 7, 82 ± 7,89 ± 5, and 82 ± 6% in muscle, liver, kidney, and fat, respectively. Mean recoveries for 7-hydroxyflumequine were 91 ± 2, 90 ± 4, 86 ± 3, and 84 ± 4% in muscle, liver, kidney, and fat, respectively.
Automated Screening Method for Determining Optimum Preservative Systems for Personal and Home Care Products
Authors: Lenczewski Melissa E , Kananen Lafonna L
Published: February 2020

abstract

A procedure was designed to determine the minimum preservative level (MPL) for personal and home care products. A highly preserved sample and an unpreserved sample were combined at different concentrations within a 96-we 11 microtiter plate by using an autodilutor. A unique tip design made it possible to accurately deliver viscous test materials that cannot be dispensed using vacuumor fluid-filled systems. After inoculation, the sample was evaluated at a specified time interval for the presence of surviving bacteria, yeast, and mold. The lowest concentration of preservative with no microbial growth is the recommended level of preservative for the product. Because sample turbidity may interfere with determination of the endpoint, a colorimetric endpoint was used to indicate growth of microorganisms and to differentiate product from growth. The predicted levels were tested with a modified Cosmetic, Toiletry, and Fragrance Association method. The method successfully predicted effective preservative levels in many personal and home care products with a broad range of viscosities.
Comparison of Six Methods for Determining Aged Phosphine Residues in Wheat
Authors: Desmarchelier James M , Allen Sylvia E , Ren Yong-Lin
Published: February 2020

abstract

Phosphine (PH3) and methyl bromide (ChhBr) are the main fumigants used on stored grains. Published multiresidue methods, including those based on solvent extraction and on purge-and-trap techniques, give poor recoveries of CH3Br and, in our hands, close to zero recovery of PH3 and carbonyl sulfide (COS), a potential fumigant. We examined factors influencing fumigant analysis, including stability of chemicals in leachates and partitioning of fumigant between leachate and air. The partition ratio, defined as the ratio of fumigant concentration in leachate to that in the headspace, varied between 1.1 for PH3 and >100 for ethylene dibromide (EDB). An official procedure involving solvent extraction followed by partitioning was modified by being performed in sealed flasks. This change raised the recovery of ChfoBr from 28 to 85%. Volatile fumigants, including PH3 and COS, were determined from concentrations in the headspace over the leachate (aqueous acidified acetone). Recoveries were nearly quantitative at levels down to 3 ng PH3/g and 16 ng COS/g, provided that fortified samples were used as analytical standards. Thus an existing multifumigant procedure was adapted to enable determination of the main fumigants used on staple foodstuffs.
Merging Zones Standard Addition Technique for Determination of Copper in Beer by Flow Injection Atomic Absorption Spectrophotometry
Authors: Fernandes Sílvia M V , Rangel António O S S , Lima José L F C
Published: February 2020

abstract

A flow injection system for determination of copper in beer by atomic absorption spectrophotometry by the standard additions method is described. The manifold, based on the merging zone technique, prevents the burner head from clogging, as observed with the conventional reference method. With 5 standard additions, results are comparable with those of the reference method. Relative deviations were less than 5.8%, precision was better than 6.4%, and sampling rate was about 30 samples/ h. A less precise, less accurate, but faster procedure (75 samples/h) is possible with only 2 standard additions. The detection limit was 5µg/l.
Sensitive Spectrophotometric Method for Determining Pentachlorophenol in Various Environmental Samples
Authors: Agrawal Omi , Sunita G , Gupta Vinay K
Published: February 2020

A new, simple, and sensitive spectrophotometric method is described for determination of pentachlorophenol, a widely used insecticide and herbicide, in various environmental samples. The method is based on the reaction of pentachlorophenol with concentrated nitric acid to form chloranil, which liberates iodine from potassium iodide. The liberated iodine then selectively oxidizes leucocrystal violet to form crystal violet, which has an absorption maximum at 592 nm. Beer's law is obeyed over the concentration range of 0.1-1.6 μg pentachlorophenol/ 25 ml_ (0.004-0.064 ppm). The method was applied satisfactorily to determination of pentachlorophenol in air, water, plant material, textile effluent, and biological samples.
Determination of Methylmercury in Food Commodities by Gas-Liquid Chromatography with Atomic Emission Detection
Authors: Madson Mark R , Thompson Richard D
Published: February 2020

A method was developed for determining methylmercury in various food commodities. The organomercurial species was converted to methylmercuric chloride by treatment of a sample homogenized with 1.8M HCI. The resulting chlorinated species was eluted from a Celite 545-sample homogenate column with methylene chloride. The eluate was treated with stannic chloride, and the analyte was isolated from coextractives by using a wide-bore capillary column with microwave-induced plasma atomic emission detection. The method was applied to both high- and low-moisture commodities during analysis of 32 samples of grains, cereal products, fruits, and vegetables. Methylmercury was found at trace levels (i.e., between a signal-to-noise ratio of 3:1 and 10:1) and up to 0.85 ppb. Recoveries of added methylmercury ranged from 70.0 to 114.0℅. Limits of quantitation and detection were 0.63 and 0.24 pg on column, respectively, corresponding to 0.30 and 0.11 ng Hg/g sample for a 40 g sample treated according to the method.
Determination of Deoxynivalenol in White Flour, Whole Wheat Flour, and Bran by Solid-Phase Extraction/Liquid Chromatography: Interlaboratory Study
Authors: Trucksess Mary W , Page Samuel W , Wood Garnett E , Cho Tae-Hee
Published: February 2020

A liquid chromatographic (LC) method for determining deoxynivalenol (DON) in white flour, whole wheat flour, and bran at or above the U.S. Food and Drug Administration advisory level of 1 μg/g was evaluated by an interlaboratory study. Test samples of processed wheat (flour and bran) were extracted by blending with acetonitrile-water (84 + 16). Extracts were filtered and passed through a solid-phase extraction (SPE) column. The eluate was then chromatographed on a reversed-phase LC column with a water-methanol gradient. DON was measured at 220 nm. Naturally contaminated white flour, whole wheat flour, and bran samples and spiking solutions of DON to be added to the 3 commodities at 0.5,1.0, and 2.0 μg/g were sent to 4 collaborators in Kansas, Louisiana, Missouri, and Washington states. Three collaborators completed the study. Average recoveries of DON from the 3 commodities spiked at 0.5, 1.0, and 2.0 (μg/g were 94, 87, and 97%, respectively. Within-laboratory relative standard deviations for repeatability (RSDr) ranged from 3.1 to 21.7% and between-laboratory relative standard deviations for reproducibility (RSDR) ranged from 10.8 to 38.7%. On the basis of the results of this study, the SPE/LC method for DON in white flour, whole wheat flour, and bran was adopted as a peer-verified method by AOAC INTERNATIONAL
Fluorometric Determination of Acid Phosphatase in Cooked, Boneless, Nonbreaded Broiler Breast and Thigh Meat
Authors: Davis Carl E
Published: February 2020

This method is applicable for determining activity of acid phosphatase (ACP), a heat-labile enzyme, in cooked, boneless, nonbreaded broiler marinated (83.65% meat) and nonmarinated (100% meat) breast and thigh and in a 50:50 blend of breast and thigh meat. The assay uses a self-indicating substrate that, when acted upon by ACP, loses a phosphate radical and becomes a highly fluorescent compound. Cooked meat is added to deionized distilled water in a 1:3 ratio, blended with a hand-held homogenizer, and then centrifuged at 2500 relative centrifugal force for 5 min. ACP activity in the filtrate is measured after shaking on a Vortex mixer 75 μL of the extract with a pH 5.00 acetate buffer containing a nonfluorescent aromatic monophosphoric ester substrate. The rate of fluorophore formation is monitored during a 3 min incubation period (38°C) in a fluorometer, and ACP enzyme activity (mU/kg sample) is calculated. Three laboratories analyzed 6 cooked poultry products (marinated and nonmarinated breast, thigh, and 50:50 breast/thigh blend). Five cooking temperatures were used to generate different ACP activity levels, which were replicated twice with duplicate samples and duplicate sample tests representing 720 data points. Logio ACP activity (mU/kg sample) performance repeatability and reproducibility standard deviations (sr and sR) and relative standard deviations (RSDr and RSDR) over 5 cooking treatments for 6 products were as follows: marinated breast: sr = 0.02, sR = 0.08, RSDr = 0.60%, RSDR = 2.12%; nonmarinated breast: sr = 0.02, sR = 0.04, RSDr = 0.66%, RSDR = 1.29%; marinated thigh: sr = 0.01, sR = 0.01, RSDr = 0.37%, RSDR = 0.37%; nonmarinated thigh: sr = 0.02, sR = 0.05, RSDr = 0.53%, RSDR = 1.43%; marinated 50:50 breast/thigh blend: sr = 0.01, sR = 0.05, RSDr = 0.36%, RSDR = 1.31%; nonmarinated 50:50 breast/thigh blend: sr = 0.01, sR = 0.04, RSDr = 0.32%, RSDR =1.12%
Rapid Determination of Volatile Bases in Fish by Using an Ammonia Ion-Selective Electrode
Authors: Pivarnik Lori F , Thiam Mamadou , Christopher Ellis P
Published: February 2020

A simple and rapid method using an ammonia ionselective electrode (ISE) to measure volatile bases in fish is proposed. Accuracy and precision were determined with 5,10,20, and 30 ppm NH3 standard solutions. Ammonia values obtained with the method correlate strongly with total volatile basic nitrogen (r2 = 0.88). Recoveries of added ammonia to homogenized fish samples ranged from 83.7 to 96.0%. Responses of the probe to trimethylamine (TMA), calculated as NH3 (mg/100 mL), ranged from 74.9 to 91.7%. These findings indicate that the probe measured TMA as well as ammonia. Storage trials on 8 fish species illustrated that the results obtained with the ISE method reflected nitrogen concentrations based on total volatile base (TVB) analysis. This procedure may be used in lieu of the traditional TVB method for on-site rapid screening of fish
Determination of Malathion Residues in Some Medicinal Plants by Liquid Chromatography with Gas Chromatographic/Mass Spectrometric Confirmation
Authors: Tawfic Ahmed Mohamed , Ismail Saad M M , Mosleh Yahia Y
Published: February 2020

A method for determining malathion residues by reversed- phase liquid chromatography (LC) using methanol only as mobile phase is described. Malathion [diethyl(dimethoxyphosphinothiol)succinate] was applied on marjoram, mint, and chamomile. Residues were detected in fresh and dry crops by LC and confirmed by gas-LC/mass spectrometry. Average recovery of malathion was 85%. Residues detected in fresh marjoram, mint, and chamomile were 0.18, 0.23, and 0.083 mg/kg, respectively. Residues detected in dry marjoram and mint were 0.024 and 0.050 mg/kg, respectively. No malathion residues were detected in dry chamomile. The minimum detectable concentration with this method is 0.013 mg/kg. The study suggests it is safe to use malathion up to 2 sprays per season provided the crop is harvested not less than 3 weeks from the last spray
Integration and Calculation Improvements in Monensin Liquid Chromatographic Method
Authors: Krabel Beverly J , Coleman Mark R , Winland Greg W , Cottrell Brent D , Dkon Brenda K , Dickson David A
Published: February 2020

The liquid chromatographic method for monensin in premix and animal feeds was approved by the AOAC INTERNATIONAL Methods Committee on Feeds, Fertilizer, and Related Agricultural Topics and adopted by the Official Methods Board in January 1997. Improvements have been made in the integration and calculation to include additional monensin factors. The original method accounted for monensin factors A and B only. The improved method also includes monensin factors C and D, Monensin factors C and D account for approximately 2.4% of the total biopotency of monensin in both the premix and feed
Delvotest SP for Detection of Cloxacillin and Sulfamethoxazole in Milk: IDF Interlaboratory Study
Authors: Suhren Gertraud , Beukers Robert
Published: February 2020

Under the auspices of the International Dairy Federation's Group E503, a collaborative study of the Delvotest SP multiplate microbial inhibitor test was performed to gain information about the detection limits of 2 antimicrobial agents (a β-lactam and a sulfa compound), the variation of test results between users and 2 batches of the test, and the reasons for deviating results. Lyophilized milk samples spiked with various concentrations of cloxacillin or sulfamethoxazole were analyzed. Each substance/concentration combination was tested with each of 2 test batches 14 or 15 times per participating laboratory. Test results were to be read by more than one person and reported on separate forms. Results were obtained from 29 laboratories, which included 5 with no experience and 11 with limited experience with this test. Detection limits for cloxacillin (22.5 or 30 μg/kg, depending on batch) and sulfamethoxazole (45 μg/kg) were established from dose-response curves. A small difference in cloxacillin detection levels between the 2 test batches was observed. Analyses of samples gave almost unanimous results (≥95%). Of deviating results, defined as anomalous results (1.4% of readings), half could be attributed to human errors and half to procedural errors
Gas Chromatographic Determination of Azoxystrobin, Fluazinam, Kresoxim-Methyl, Mepanipyrim, and Tetraconazole in Grapes, Must, and Wine
Authors: Cabras Paolo , Angion Alberto , Garau Vincenzo L , Pirisi Filippo M , Brandolini Vincenzo
Published: February 2020

Azoxystrobin, fluazinam, kresoxim-methyl, mepanipyrim, and tetraconazole were determined in grapes, must, and wine by a gas chromatographic method with nitrogen-phosphorus (NP) and mass spectrometric (MS) detectors. Pesticides were isolated from the matrixes by online microextraction with acetone-hexane (50 + 50, v/v). Because of the high selectivity of NP and MS detectors, no interfered peaks were present and no cleanup was necessary. Recoveries from fortified grapes, must, and wine ranged from 80 to 111 %, with coefficients of variation ranging from 1 to 14%. Limits of determination were 0.05 mg/kg for kresoxim-methyl and 0.10 mg/kg for the other compounds.
Determination of Bitertanol Residues in Strawberries by Liquid Chromatography with Fluorescence Detection and Confirmation by Gas Chromatography/Mass Spectrometry
Authors: Yamazaki Yoshie , Ninomiya Takahiro
Published: February 2020

A simple and rapid method was developed for determining bitertanol residues in strawberries. Bitertanol was extracted from samples with ethyl acetate. Bitertanol acetate was added prior to extraction as a surrogate standard. The ethyl acetate extract was cleaned up by passing through tandem solid-phase extraction columns consisting of anion-exchange (SAX) and aminopropyl (NH2) bonded silica. The eluate was evaporated to dryness and reconstituted with methanol. Bitertanol residues were determined by liquid chromatography with fluorescence detection. Recoveries at 4 fortified levels (0.05,0.25,0.5, and 1.0 (µg/g), calculated by the internal standard method, ranged from 92.1 to 99.1 %, with coefficients of variation ranging from 0.3 to 4.0%. The detection limit was 0.01 µg/g. Of 25 commercial strawberry samples analyzed for bitertanol residues, 5 contained bitertanol residues at concentrations ranging from 0.02 to 0.51 µg/g. Positive samples were confirmed by gas chromatography/mass spectrometry with mass-selective detection (m/z 170 and 168).
Thin-Layer Chromatographic Determination of Catecholamines, 5-Hydroxytryptamine, and Their Metabolites in Biological Samples: A Review
Authors: Alemany Gaspar , Akaârir Mohamed , Antonio Gamundí , Nicolau Maria C
Published: February 2020

A review of methodology for separation, detection, and quantitative determination of catecholamines, 5-hydroxytryptamine, and their acidic metabolites in biological tissue and fluids by thin-layer chromatography is presented. Selected procedures, including fluorometric scanning densitometry for catecholamine acetyl derivatives and color scanning densitometry for acids, are described.
Validation of Thin-Layer Chromatography Quantitation Determination with CCD Camera and Slit-Scanning Densitometer
Authors: Petrovic Mira , Kastelan-Macan Marija , Lazaric Katica , Babic Sandra
Published: February 2020

Video densitometric and classical slit-scanning determinations of pesticides on thin-layer chromatographic plates were validated for linearity, precision, and detection limit. A comparison of results showed that slit-scanning densitometry is more sensitive and more precise than video densitometry. However, according to validation requirements, relative standard deviation for video densitometry is acceptable (3.5–5.3%). Linearities are very good and almost identical for both techniques. The main advantage of video technology is speed (a few seconds, compared with 20 min with scanning densitometry). Video technology also provides excellent archiving facility. Image and chromatographic data can be stored together, edited, and used for many tasks.
Reversed-Phase Thin-Layer Chromatography with Different Stationary Phases in Studies of Quantitative Structure–Biological Activity Relationship of New Antimycotic Compounds
Authors: Rózylo Jan K , Zabiñska Anna , Matysiak Joanna , Niewiadomy Andrzej
Published: February 2020

Reversed-phase thin-layer chromatography with RP-8, RP-18, and RP-18W stationary phases was used in quantitative structure–activity relationship (QSAR) studies of new antimycotic compounds. The retention behavior of 10 dihydroxythioben-zanilides was examined for acquisition of log k data. With water–acetone mixtures as the mobile phases, the concentration range for which the correlation between log k′ and acetone concentration is linear was established for each stationary phase and used to determine hydrophobicity parameters log k′w by linear extrapolation. The effect of substituents on retention constants was quantitated by using the group contribution parameters τw. On the basis of QSAR equations obtained from these studies, log k′w, data can be used to predict antifungal activities of dihydroxythiobenzanilides with satisfactory accuracy.
Application of Overpressured Layer Chromatography Combined with Digital Autoradiography and Mass Spectrometry in the Study of Deramciclane Metabolism
Authors: Ludányi Krisztina , Vékey Károly , Szúnyog József , Mincsovics Emil , Karancsi Tamás , Újszászy Kálmán , Nemes Katalin Balogh , Klebovich Imre
Published: February 2020

Overpressured layer chromatography was combined with the highly sensitive and rapid digital autoradiography (DAR) and mass spectrometry to separate, detect, and identify 3H-and 14C-labeled deramciclane metabolites in different biological matrixes. Several minor and major metabolites were separated from plasma and urine samples. The radioactive metabolites localized by DAR were scraped from the thin-layer chromatographic plate and transferred to a mass spectrometer for structure identification. Several metabolites were isolated and characterized, including hydroxy-/V-des- methyl deramciclane, which is described in detail. The combination of techniques is efficient and has good sensitivity: about 2 μg metabolite from a biological matrix was isolated and identified this way.
Determination of Glycarbylamide in Chicken Tissue by High-Performance Liquid Chromatography
Authors: Yamamoto Yuzo , Kondo Fusao
Published: February 2020

A high-performance liquid chromatographic (HPLC) method for determining glycarbylamide (GB) in chicken tissue was developed. GB was extracted with acetonitrile, followed by solid-phase extraction cleanup using a Bond Elut cartridge column with neutral alumina. After the extract had been evaporated to dryness, the residue was dissolved in 1.0 mL 0.1 N sodium hydroxide. Then 1.0 mL 0.1 M potassium dihydrogen phosphate solution was added to it. HPLC separation was done on a 250 × 4.6 mm id TSK-GEL ODS 80™TM column with 0.05M potassium dihydrogen phosphate as the mobile phase. Ultraviolet detection was done at a wavelength of 260 nm. The calibration curve of standard GB solutions was linear between 0.16 and 3 μg/mL (correlation coefficient, r = 0.999). The recovery of GB from chicken muscle spiked at 0.8 μg/g was 88.6 ± 2.3% (mean ± standard deviation, n = 5), and the lower limit of determination was 0.05 μg/g in chicken muscle.
Reference Values of Urinary 3,5,6-Trichloro-2-Pyridinol in the Italian Population—Validation of Analytical Method and Preliminary Results (Multicentric Study)
Authors: Aprea Cristina , Betta Alberto , Catenacci Giovanni , Lotti Andrea , Magnaghi Silvana , Barisano Angelo , Passini Valter , Pavan Ivo , Sciarra Gianfranco , Vitalone Vincenzo , Minoia Claudio
Published: February 2020

The interlaboratory validation of analytical procedures for the assay of urinary 3,5,6-trichloro-2-pyridinol (TCP) in the general Italian population is reported. The determinations were performed by high-resolution gas chromatography (HRGS) with electron capture detection and HRGS with mass spectrometry (MS) in 2 laboratories. The urine samples were from 42 participants from 3 regions of Italy. The results were evaluated by interlaboratory quality control. Urinary TCP concentrations were above the detection limit (1.2 (μg/L) in 88% of the population, with a mean detectable concentration [GM (GSD)] of 2.8 (1.9) (μg/g creatinine (creat). (GM, geometric mean; GSD, geometric standard deviation.) The Mann-Whitney U test showed that wine consumption was a statistically significant variable (p < 0.05) for urinary concentrations of TCP. Analysis of variance of the logarithm of urinary TCP versus wine consumption and diet showed a statistically significant fit. The model used explained 30% of the total variance: wine consumption and diet accounted for 37 and 17% respectively of the explained variance.
Multiresidue Screening of Pesticides in Foods Using Retention Time Locking, GC-AED, Database Search, and GC/MS Identification
Authors: Cook Joanne , Engel Marc , Wylie Philip , Quimby Bruce
Published: February 2020

Fruit and vegetable extracts were screened for over 400 pesticides by gas chromatography with atomic emission detection (GC-AED) and an experimental database. A technique called retention time locking was used to match GC-AED and GC with mass spectrometry (MS) retention times to those of the database. Samples were analyzed for sulfur, nitrogen, phosphorus, and chlorine by GC-AED. Possible pesticides were suggested by database search and identified by GC/MS. Forty-four pesticide standards were analyzed to determine the precision of retention time matching and the accuracy of the database search. Analytical retention times matched database retention times within 0.32 min. Using elemental criteria, the database search identified the correct compound for 41 of 44 pesticide standards. For blind spikes of fruit and vegetable extracts, the database suggested 22 of 26 spiked pesticides as matches. Nineteen were identified by GC/MS. The combination of retention time locking, GC-AED, database search, and GC/MS can be a powerful tool for identifying pesticides in a complex matrix