bluuebunny/crossref_metadata_2025 huggingface dataset:
Performance of Homogenizers in Infrared Milk Analyzers: A Survey
Authors: Smith Erika B , Barbano David M , Lynch Joanna M , Fleming J Richard
Published: February 2020

The objective of this survey was to determine if infrared milk analyzers can achieve a <0.05% difference in fat test between unhomogenized and homogenized portions of the same milk, as stated in official methods. Two batches of pasteurized, unhomogenized milk (3 and 6% fat) were prepared from a single source of raw cream and skim. Homogenized milks were produced at 3 pressures: 0, 10342, and 17238 kPa. Pairs of unhomogenized and homogenized portions of the same milk were tested on 22 infrared analyzers. More instruments exceeded the 0.05% difference between homogenized and unhomogenized milk than expected; differences between homogenized and unhomogenized milk increased with increasing homogenization pressure and fat concentration. At 3% fat, differences between homogenized and unhomogenized milks at both 10342 and 17238 kPa were <0.05% for 21 of 22 instruments for fat A; only 17 and 13 of 22 instruments for fat B achieved a difference of <0.05% at 10342 and 17238 kPa, respectively. At 6% fat, differences between homogenized and unhomogenized milks for fat A were <0.05% for 15 and 14 of 22 instruments at the 2 pressures, respectively. For fat B, 8 and 5 of 22 instruments achieved a difference of <0.05% at 10432 and 17238 kPa. Instruments were also evaluated for homogenization efficiency by a revised criterion that is dependent on the fat content of the samples used for the evaluation.
Automation of Potentiometric Measurements: Determination of Water-Extractable Sodium in Bread Using a Sodium Ion Selective Electrode with Minimum Sample Preparation
Authors: Yperman Jan , Carleer Robert , Reggers Guy , Mullens Jules , Poucke Lucien Van
Published: February 2020

Different automated potentiometric procedures for the determination of NaCI in bread have been investigated and evaluated. The results are compared with data from atomic absorption spectrophotometry (AAS). A continuous potentiometric Na+ determination using a sodium ion selective electrode (ISE) is superior to all other methods. The sodium content can be measured by a reliable, rapid, and inexpensive potentiometric measurement of a finely ground and dried bread sample, extracted in the measurement beaker, as an alternative to the conventional and time-consuming AAS procedure.
Liquid Chromatographic Determination of Dicloxacillin Preparations: Interlaboratoiy Study
Authors: Hsu Mei-Chich , Huang Weng F
Published: February 2020

A previously published liquid chromatographic method proposed for the analysis of dicloxacillin preparations was subjected to an interlaboratory study. The method is rigorously defined in terms of performance requirements, yet allows a degree of flexibility to the individual analyst. Eight laboratories participated in a study to analyze 3 samples in duplicate. Estimates for the repeatability and reproducibility of the method, expressed as relative standard deviations of the results of the determination of dicloxacillin preparations, were <0.57 and 2.56%, respectively.
Simultaneous Liquid Chromatographic Determination of Thiamine and Riboflavin in Selected Foods
Authors: Sims Art , Shoemaker Dirk
Published: February 2020

A reliable, improved liquid chromatographic (LC) method has been developed for the measurement of thiamine and riboflavin in foods. The major improvement in the method is the chromatographic separation achieved. The method is also very reproducible and extremely sensitive. After autoclave extraction, samples are derivatized to form thiochrome (a highly fluorescent oxidation product of thiamine). Riboflavin is naturally fluorescent. Interferences are removed on a Ci8 cartridge and chromatographed by using a reversed-phase separation. The mobile phase used is 72% 0.005M NH4OAc (pH 5.0)-28% MeOH. Fluorescence detection using wavelength switching, 370-435 for thiamine and 370-520 for riboflavin, allows determination of each vitamin at its optimum wavelength for maximum sensitivity. Detection limits were 0.05 ng for both thiamine and riboflavin. The method can also be performed by using a fluorescence detector at a single wavelength, but with a sacrifice of sensitivity. Data comparisons between AOAC fluorometric and LC results were excellent for routine samples, as well as for American Association of Cereal Chemists (AACC) check samples. All LC results from AACC samples were within 2 standard deviations of the mean. Reproducibility was 1.9% for thiamine and 1.6% for riboflavin.
Reversed-Phase Liquid Chromatographic Method for the Simultaneous Determination of Benomyl and Methyl lH-Benzimidazol-2-ylcarbamate in Wettable Powder Formulations
Authors: Singh Raj P , Chiba Mikio
Published: February 2020

A liquid chromatographic (LC) method is reported for the simultaneous determination of benomyl, methyl {1 -[(butylamino)carbonyl]-1 H-benzimidazol-2-yl}carbamate and carbendazim, methyl 1H-benzimidazol-2-ylcarbamate (MBC), in wettable powder (WP) formulations. In this method, benomyl is converted to 3-butyl-2,4-dioxo-s-triaz-ino[1,2-a]benzimidazole (STB) in 0.125M sodium hydroxide. After conversion (at room temperature in 20 min), STB is determined simultaneously with MBC (which remains intact with the sodium hydroxide treatment) at 286 nm after LC separation on a C18 column. The method was accurate and showed good reproducibility, with relative standard deviations of 0.7 and 2.2% for benomyl and MBC determinations, respectively.
Rapid Gas Chromatographic Method for the Multiresidue Screening of Fruits and Vegetables for Organochlorine and Organophosphate Pesticides
Authors: Pylypiw Harry M
Published: February 2020

A rapid and reliable method was developed for the determination of pesticides in fruits and vegetables. A100 g sample is extracted with a mixture of 200 mL petroleum ether and 100 mL 2-propanol. The extract is backwashed 4 times, twice with aqueous sodium sulfate and twice with 350 mL distilled water, and then dried over 15 g sodium sulfate. The dried extract is analyzed by capillary gas chromatography with selective organochlorine and organophosphorus detection. The method determines primarily nonpolar pesticides, with recoveries ranging from 81 to 114%, and has an average limit of detection of 10 ppb for both detectors.
Determination of 2-Methoxy-3-alkylpyrazines in Carrot Products by Gas Chromatography/Nitrogen–Phosphorus Detection
Authors: Lund Eric D
Published: February 2020

The 2-methoxy-3-alkylpyrazines in 6 types of carrot products were determined by a stripping–selective trapping procedure followed by purge-and-trap gas chromatographic analysis with an NP detector. The aroma threshold of one of the principal pyrazines, 2-methoxy-3-sec-butylpyrazine, in a carrot medium was 0.19 ng/g. The concentrations of this compound in whole-carrot products were 0.43 (fresh), 0.291 (canned, cooked), and 0.224 ng/g (frozen). A diced, cooked, and freeze-dried product contained 0.070 ng/g. All of these products contained only this pyrazine. In contrast, a shredded, bagged product contained 2-methoxy-3-isopropylpyrazine as the sole pyrazine (0.32 ng/g), and a sliced, dried product contained a mixture of 3 pyrazines: 2-methoxy-3-sec-butyl- (0.109 ng/g), 2-methoxy-3-iso-propyl- (0.176 ng/g), and 2-methoxy-3-isobutylpyra-zine (0.029 ng/g). The pyrazine concentrations in most of these products (except the freeze-dried product) exceeded the threshold value.
Detoxification of Citrinin and Ochratoxin A by Hydrogen Peroxide
Authors: Fouler Sophie G , Trivedi Alka B , Kitabatake Naofumi
Published: February 2020

The effects of hydrogen peroxide on citrinin and ochratoxin A toxicity were examined using HeLa cells. The citrinin was completely detoxified by prior incubation with 0.05% hydrogen peroxide for 30 min at room temperature, and the toxic compound(s) that resulted from heating citrinin at 100°C were also detoxified upon reheating it with hydrogen peroxide. On the other hand, ochratoxin A was not detoxified by hydrogen peroxide at room temperature, but its toxicity was reduced by heating ochratoxin A with hydrogen peroxide under alkaline conditions.
Determination of Polymerized Triglycerides in Frying Fats and Oils by Gel Permeation Chromatography: Interlaboratory Study
Authors: Beljaars Paul R , Van Dijk Remmelt , Houwen-Claassen Adrie A M
Published: February 2020

An interlaboratory study of the gel permeation chro-matographic (GPC) determination of polymerized triglycerides (PTG) in frying fats and oils was conducted by the Project Group on Collaborative Studies (PCS) of the Inspectorate for Health Protection, Food Inspection Service, The Netherlands. Thirteen laboratories participated in this study, which was focused on thermally abused oil and fat samples containing dimerized and polymerized triglycerides at levels just below and far above the Dutch regulatory limit of 16% (m/m). Samples were dissolved in tetrahydrofuran (THF) and analyzed on a GPC system, using THF as the mobile phase. Refractive index (Rl) detection was used to determine PTG. Six heat-processed fat samples containing from 14 to 28% (m/m) PTG at 3 different levels (3 pairs of split level samples) were single analyzed according to the proposed procedure. Data analysis was performed according to the International Union of Pure and Applied Chemistry/International Organization for Standardization/AOAC protocols for statistics. The results of 2 collaborators were identified as outliers at the 20% (m/m) PTG level by applying the paired Grubbs test at the 1% level of significance. The repeatability relative standard deviation (RSDr) values ranged from 0.48 to 2.25%, whereas the reproducibility relative standard deviation (RSDr) values ranged from 1.34 to 4.57%.
Liquid Chromatographic Determination of Sarafloxacin Residues in Channel Catfish Muscle Tissue
Authors: Meinertz Jeffery R , Dawson Verdel K , Gingerich William H , Cheng Bea , Tubergen Mark M
Published: February 2020

A liquid chromatographic method is described for the determination of sarafloxacin hydrochloride residues in channel catfish (Ictalurus punctatus) fillets. Sarafloxacin was extracted from fillet tissue with acetonitrile–water (1+1). The extract was centrifuged and the supernatant was partitioned with hexane. The aqueous fraction was filtered through a 0.45 μm filter and evaporated to dryness. The sample was redissolved with 20% acetonitrile–methanol (3 + 2) and 80% trifluoroacetic acid (0.1%), centrifuged, and filtered to remove proteins. Samples were analyzed by chromatography with gradient elution on a C18 column and with fluorescence detection (excitation at 280 nm and emission above 389 nm). Mean recoveries ranged from 85.4 to 104%, and relative standard deviations ranged from 1.06 to 5.58% in samples spiked at concentrations of 10.0–863.8 ng/g. The method detection limit for sarafloxacin was 1.4 ng/g.
Monitoring Pesticide Residues in Olive Products: Organophosphorus Insecticides in Olives and Oil
Authors: Lentza-Rizos Chaido
Published: February 2020

A simple and efficient gas-liquid chromatographic method was used to screen and quantitate residues of azinphos ethyl, chlorpyrifos, diazinon, di-methoate, fenthion, fenthion sulfoxide, methi-dathion, parathion ethyl, and parathion methyl in olive fruit and olive oil. Most olive fruit samples analyzed during 1991-1992 either contained no detectable residues of the insecticides or contained low concentrations of fenthion, dimethoate, and chlorpyrifos. One sample contained fenthion sulfoxide at a level exceeding FAO/WHO Codex Ali-mentarius maximum residue levels (MRL) for total fenthion. Commercially packed oil samples either contained no detectable residues of the insecticides or contained low concentrations of fenthion, fenthion sulfoxide, and chlorpyrifos. More than half of the virgin oil samples collected from individual growers contained no detectable residues. The others contained mostly fenthion and its sulfoxide metabolite. Of the samples analyzed, 13% exceeded Codex MRL for total fenthion residues. These samples were from a monitoring program targeted at produce most likely to contain residues. Refining procedures seem to act as a decontamination technique for oil containing fenthion residues.
Liquid Chromatographic Determination of Multiple Sulfonamide Residues in Bovine Milk: Collaborative Study
Authors: Smedley Michael D
Published: February 2020

A collaborative study involving 8 laboratories was conducted on the determination of 8 sulfonamide residues in raw bovine milk using a liquid chromatographic (LC) method. The sulfonamides are extracted with chloroform-acetone, the organic phase is evaporated, the residues are dissolved in an aqueous potassium phosphate solution, and the fatty residues are removed by washing with hex-ane. The aqueous layer is collected, filtered, and infected onto an LC system, and the analyte is detected by ultraviolet (UV) absorption at 265 nm. To quantitate all 8 sulfonamides isocratically, 2 chromatographic conditions are required: 12% methanol in the mobile phase for 5 sulfonamides, and 30% methanol in the mobile phase for 4 sulfonamides. Sulfamethazine (SMZ), the most widely used sulfonamide, is detected by both systems. Collaborators were instructed to analyze 3 replicates each of control milk and control milk fortified at 3 levels. They were also provided with 20 blind incurred samples (10 samples in duplicate) to analyze. For 10 ppb fortified milk, the average interlabo-ratory recovery for the 8 sulfonamides ranged from 56.2% for sulfaquinoxaline (SQX) to 82.7% for SMZ in the 12% methanol mobile phase (SMZ12). Also at this level, Sr, ranged from 3.2 for SQX to 8.9 for SMZ12, and SR ranged from 6.9 for sulfadimethox-ine to 17.2 for SMZ in the 30% methanol system (SMZ30). At 10 ppb, RSDr and RSDR ranged from 5.7% for SQX to 10.8% for SMZ12, and 10.1% for sul-famerazine to 20.9% for SMZ30, respectively. These results demonstrate that the method is suitable for the determination of the 8 sulfonamide residues in mHk at 10 ppb. However, the identification of positives by this procedure needs additional confirmation by procedures comparable to the specificity achievable by liquid or gas chromatography combined with mass spectrometry.
Evaluation of a Gas Chromatographic Method to Identify Irradiated Chicken, Pork, and Beef by Detection of Volatile Hydrocarbons
Authors: Schreiber Georg A , Schulzki Grit , Spiegelberg Almuth , Helle Norbert , Bögl Klaus W
Published: February 2020

A method suitable for routine application was used in an interlaboratory study to detect irradiation treatment of chicken carcass, pork, and beef. By using gas chromatographic analysis, 17 participating laboratories determined the quantity of 4 different radiation-induced volatile hydrocarbons (tetradecene, pentadecane, hexadecadiene, and neptadecene) in the fat fraction of coded specimens approximately 3 and 6 months after irradiation. The specimens of each type of meat were supplied by 2 different producers. The dose range tested (0.6-7.5 kGy) included levels commercially used to reduce the number of contaminating microorganisms (1-5 kGy). The method employed permitted a correct identification of irradiated or nonirradiated in 98.3% of the 864 specimens.
Integration of Liquid Chromatography with Immunoassay: An Approach Combining the Strengths of Both Methods
Authors: Krämer Petra M , Li Qing X , Hammock Bruce D
Published: February 2020

The integration of liquid chromatography (LC) with immunochemical detection combines the superior separation power of LC and the sensitivity and specificity of immunoassays. This approach is shown with 3 LC systems (Perkin-Elmer, C18 RP, 4.6 mm; Varian, C18 RP, 1 mm microbore; Michrom, C18 RP, 1 mm microbore) Integrated with an enzyme-linked immunosorbent assay (ELISA) selective for five 4-nitrophenols. The nitrophenols were separated with the 3 LC systems with isocratic runs of 15 to 20 min. Microbore LC separation showed a 10-20 times reduction in solvent amount compared to conventional separation. LC–immunoassay was about 8- to 10-fold more sensitive compared with LC with UV detection. Integrated LC–immunoassay proved to be a very selective method when 2-methylphenol was injected with an equimolar mixture of 2-amino-4-nitrophenol and 3-methyl-4-nrtrophenol; 2-methy I phenol does not crossreact with the serum used. Only 2 peaks could be seen in the detection, even when 2-methylphenol was present in very high amounts (3000 pmol). Further, the EUSA-LC detection proved to be selective and sensitive for complex matrixes. 2-Amlno-4-nitrophenol was clearly identified in spiked extracts of soil and plant, even when a very small amount (2.4 ng) was injected. Although LC–immunoassay is more labor intensive than LC with UV detection, it offers great advantages in multiresidue analysis and is generally applicable for peak confirmation.
Analysis of Chlorophenols in air at the Nanogram-per-Cubic-Meter-Level
Authors: Swami Kamal , Narang Rajinder S
Published: February 2020

A gas chromatographic (GC) method for the analysis of chlorophenols in air at the nanogram-per-cubic-meter level was developed. Chlorophenols were trapped on Porapak-N, eluted with methanol, and then derivatized before GC analysis.
Enzyme-Linked Immunosorbent Assay for Detection of Zearalenone in Corn, Wheat, and Pig Feed: Collaborative Study
Authors: Bennett Glenn A , Nelsen Terry C , Miller Brjnton M
Published: February 2020

A direct competitive enzyme-linked immunosorbent assay (ELISA) screening method for zearalenone in corn, wheat, and feed at 500 ng/g was evaluated by 23 collaborators (22 laboratories) in an international collaborative study. Eighteen samples of spiked or naturally contaminated corn, wheat, and pig feed were prepared by the sponsoring laboratory and sent for testing with complete test kits to participating collaborators in Canada, Italy, Sweden, The Netherlands, and the United States. Test samples were extracted with methanolwater solution (70 + 30) by shaking on a wrist-action shaker for 3 min. A portion of the extract was mixed with an equal volume of zearalenone-enzyme conjugate, and the mixture was incubated with zearalenone-specific monoclonal antibodies coated onto microtiter wells. All test samples were assayed in duplicate. One of 52 (2%) blanks was reported positive. Thirty-nine of the 52 (75%) samples that were spiked at 500 ng/g were reported as positive. Forty-nine of the 51 (96%) samples with concentrations at or above 1000 ng/g were reported as positive. The overall incidence of false negatives was 6.0% and the incidence of false positives was 22.7% by the ELISA method. Only one (3.4%) false negative was reported for samples containing ≥800 ng/g. In the spectrophotometric method, 8 collaborators determined approximate levels of zearalenone in test samples from standard curves constructed from spiked extracts (0–3000 ng/g of each commodity tested). This method gave and overall incidence of false negatives of 5.7% and false positives of 17.8%. Average relative standard deviations, RSDr (repeatability) and RSDR (reproducibility), were 11.6 and 25.1% for spiked samples and 11.7 and 33.1% for naturally contaminated samples, respectively. Standard curves were constructed with each set of samples assayed. Comparison of absorbance values from these standard curves indicate the performance of reagents and antibody used in the assay. The ELISA method has been adopted first action by AOAC INTERNATIONAL as a screening method for zearalenone at ≥800 ng/g in corn, wheat, and pig feed.
Development of a New Series of Agricultural/Food Reference Materials for Analytical Quality Control of Elemental Determinations
Authors: Ihnat Milan
Published: February 2020

Ten new Agricultural/Food Reference Materials — Bovine Muscle Powder (National Institute of Standards and Technology [NIST], code NIST RM 8414), Whole Egg Powder (NIST RM 8415), Microcrystalline Cellulose (NIST RM 8416), Wheat Gluten (NIST RM 8418), Corn Starch (NIST RM 8432), Corn Bran (NIST RM 8433), Whole Milk Powder (NIST RM 8435), Durum Wheat Flour (NIST RM 8436), Hard Red Spring Wheat Flour (NIST RM 8437) and Soft Winter Wheat Flour (NIST RM 8438) — were prepared by application of milling, irradiation, sieving, blending, and packaging procedures. Excellent material homogeneity was found for virtually all major, minor, and trace elements of interest. The reference materials were characterized with respect to elemental composition via an extensive international, interlaboratory characterization (certification) campaign. Chemical analyses conducted in 73 cooperating laboratories applying 13 major classes of independently different analytical methods led to 278 concentration values for 34 nutritionally, toxicologically, and environmentally pertinent elements. A total of 213 best-estimate and 65 informational concentration values are available for Al, As, B, Ba, Br, Ca, Cd, CI, Co, Cr, Cs, Cu, F, Fe, Hg, I, K, Mg, Mn, Mo, N, Na, Ni, P, Pb, Rb, S, Sb, Se, Sr, Ti, V, W, and Zn. These products make a substantial contribution to the existing world repertoire of biological reference materials with respect to natural matrix and elemental composition. They are expected to be useful to analysts for quality control of analytical data. Applications include evaluations of analytical methods and instruments used in nutritional, toxicological, monitory, regulatory, environmental, agricultural, and other investigations. These products are available to the analytical community from the Standard Reference Materials Program, NIST, Gaithersburg, MD.
Effect of Milling Procedure on the Measurement of Dietary Fiber by a Gravimetric Method
Authors: Mullin W John , Wolynetz Mark S
Published: February 2020

Samples of white potato, sweet potato, hard red spring wheat, soft white winter wheat, and soft wheat bran were ground in a Wiley mill or a Cyclotec mill. A significantly (p < 0.0001) larger proportion of coarse material (>75μ) resulted from the Wiley mill, and a significantly (p < 0.0001) larger proportion of fine material (<45μ) was produced by the Cyclotec mill. The effect of particle size on the determination of soluble, insoluble, and total dietary fiber was less well defined. In 4 of 5 commodities tested, samples from the Cyclotec mill showed a greater amount of soluble fiber, while the reverse was true for insoluble and total fiber. The difference in total dietary fiber, with respect to the mill used in sample preparation, varied from 0.24% on a total 9.10% for potatoes to 1.00% on a total of 14.05% for hard red spring wheat.
Liquid Chromatographic Assay of Diatrizoic Acid and Its Diiodo Degradation Products in Radio-Opaque Solutions
Authors: Farag Shawky A
Published: February 2020

A liquid chromatographic method is described for the analysis of diatrizoic acid (2,4,6-triiodo-3,5-diacetamidobenzoic acid) and its 2,4- and 2,6-diiodo degradation products in radio-opaque injection solutions. The method is accurate, precise, and linear at a concentration range of 5–50 ppm.
Spectrophotometric Method To Determine Ternary Mixtures of Atrazine, Diuron, and Chlorpyrifos in Water and Soil by a Ratio Spectrum-Zero Crossing Method
Authors: Galera M Martínez , Vidal J L Martínez , Frenich A Garrido , Vázquez P Parrilla
Published: February 2020

A spectrophotometric method based on simultaneous use of first derivative of ratio spectra and measurement of zero-crossing wavelengths resolves ternary mixtures of atrazine, diuron, and chlorpyrifos. Calibration graphs were linear for atrazine between 1 and 15 μg/mL and for diuron and chlorpyrifos between 1 and 10 μg/mL. The pesticides in groundwater and soil were determined by the method, at part-per-billion levels, after solidphase extraction, with good results. Interferences caused by other pesticides were studied.
Multicolumn Solid-Phase Extraction Cleanup of Organophosphorus and Organochlorine Pesticide Residues in Vegetable Oils and Butterfat
Authors: Gillespie Allesia M , Daly Sean L , Gilvydis Dalia M , Schneider Felix , Walters Stephen M
Published: February 2020

Diatomaceous earth columns used with reversed and normal solid phase extraction (SPE) cartridges were evaluated for the quantitative determination of a number of organophosphorus (OP) and organochlorine (OC) pesticide residues in edible vegetable oils and butterfat. An oil or fat sample (about 2 g) in hexane was passed through a diatomaceous earth (Extrelut QE) column and a Cis bonded silica (ODS) SPE cartridge, resulting in the separation of the pesticides from about 98% of the lipids. The eluate was split in half, with the first portion concentrated into acetone for the determination of OP pesticides by gas chromatography with flame photometric detection (GC–FPD). The other half was passed through an Alumina-N SPE cartridge for additional cleanup of lipid matrix to determine OC pesticides by GC with electron-capture detection (GC–ECD). Average recoveries from fortified samples were greater than 89% for the pesticides studied.
Determination of Six Common Phthalate Plasticizers in Grain Neutral Spirits and Vodka
Authors: Leebowitz Jeffrey N , Sarmiento Rafael , Dugar Sumer M , Ethridge Michael W
Published: February 2020

Two direct sample injection methods using liquid chromatography (LC) and gas chromatography coupled with mass spectrometry (GC/MS) were used to determine phthalate residues in grain neutral spirits and vodka. Six reported phthalates were quantitated at concentrations as low as 20 μg/L (20 ppb) with no sample preparation or sample enrichment.
Evaluation of a Liquid Chromatographic Method for the Determination of Fumonisins in Corn, Poultry Feed, and Fusarium Culture Material
Authors: Rice Larry G , Ross P Frank , Dejong Jan , Plattner Ronald D , Coats Joel R
Published: February 2020

The performance of a liquid chromatographic method for determining fumonisins in corn, animal feeds, and culture material was evaluated. Efficiencies of extractions with the following solvent systems were determined: acetonitrile–water (50 + 50, v/v), methanol–water (75 + 25, v/v), and 100% water. The acetonitrile solvent gave both higher extraction efficiencies and faster extraction times than the other 2 solvents. Extraction was followed by C18 solid-phase extraction column cleanup. Fumonisin B1 (FB1), fumonisin B2 (FB2), and fumonisin B3 (FB3) were measured by precolumn derivatization with ophthalaldehyde followed by isocratic separation on a C18 reversed-phase column with a moB1le phase of 50 mM potassium dihydrogen phosphate (pH 3.3)–acetonitrile (60 + 40). Commercially prepared poultry feed, corn, and Fusarium spp. corn cultures were analyzed at the following levels: FB1, 1.5 to 15 000 jig/g; FB2, 0.5 to 4000 μg/g; FB3, and 0.17 to 1 500 μg/g. Recoveries were 91–94%, 90–100%, and 81–93% for FB1, FB2, and FB3, respectively. Precision (coefficient of variation) was determined with pooled field samples and ranged from 2% at 19 μg/g for FB1 to 9% at 0.17 μg/g for FB3. Time and pH studies of the formation of the fluorescent derivative and its stability were conducted. Complete reaction occurred at pHs above 7.9, with optimal pH for chromatography between 8.0 and 8.5. No statistically significant response differences were detected for reaction times ranging from 4 to 40 min; however, the detector signal was significantly reduced when reaction times were shorter than 4 min. Chromatograms of samples were free of interferences for all feeds, corn, and culture material tested. Quantitation limits for the 3 fumonisins were of the same magnitude and were estimated to be 0.1 μg/g for FB1 and 0.2 μg/g for FB2 and FB3.
Analysis of Polychlonnated Biphenyls in Fatty Biological Matrixes by On-Line Supercritical Fluid Extraction and Supercritical Fluid Cleanup
Authors: Alley Earl G , Lu Guozhen
Published: February 2020

We present a method that combines the extraction of polychlonnated biphenyls (PCBs) and their separation from relatively large quantities of fat in biological matrixes by combined supercritical fluid extraction and separation. Cyano-functionalized silica gel, silica gel, aluminum oxide, Florisil, 3-aminopropyl- functionalized silica gel, and octadecyl-functionalized silica gel were tested for suitability as chromatographic media for separation of PCBs from lipids. Silica gel, 3-aminopropyl-functionalized silica gel, and Florisil adequately separated PCBs from lipids when eluted with supercritical CO2. Florisil allowed both the extraction of PCBs and their separation from lipids in PCB-spiked chicken egg and fish. Two grams of sample containing PCBs at 0.125 μg/g was sufficient for subsequent separations and the low-level analysis required for the more toxic PCB components.
Electrothermal Atomic Absorption Spectrometric Determination of Cadmium, Copper, Iron, Lead, and Selenium in Fruit Slurry: Analytical Application to Nutritional and Toxicological Quality Control
Authors: Cabrera Carmen , Lorenzo Maria Luisa , Lopez Maria Carmen
Published: February 2020

A method is described for direct determination of cadmium, copper, iron, lead, and selenium in slurried fruit samples by electrothermal atomic absorption spectrometry. The fresh samples were suspended in Triton X-100 and shaken with 10 g zirconia spheres until a slurry was formed. The graphite furnace conditions were optimized for each element. The detection limits were 0.3,3.5, 15.0,0.5, and 10.0 ng/g for Cd, Cu, Fe, Pb, and Se, respectively. Accuracy and precision were checked against sample mineralization in a microwave aciddigestion bomb. Results for analyses of National Institute of Standards and Technology standard reference materials agreed closely with certified values. Analytical application of this method was tested with 40 samples of 8 widely consumed fruit species. The mean values (referred to fresh weight of edible fraction) for each fruit species had ranges of 0.0003–0.050 μg/g for Cd, 0.316–1.094 μg/g for Cu, 2.00–5.50 μg/g for Fe, 0.050–0.396 μg/g for Pb, and 0.010–0.020 μg/g for Se. The proposed method is useful for routine multielemental analysis in nutritional and toxicological quality control of fruits and similar foodstuffs.
Enhancement of Ethylenethiourea Recoveries in Food Analyses by Addition of Cysteine Hydrochloride
Authors: Sack Chris A
Published: February 2020

The effectiveness of cysteine hydrochloride (Cys–HCI) as a preservative of ethylenethiourea (ETU) in product matrixes and during analysis was studied. ETU recoveries were adversely affected by certain product matrixes when fortified directly into the product. Recoveries in 8 selected food items were 0–92% when analyzed 30 min after fortification and 0–51% when analyzed after 24 h. When Cys–HCI was added to product prior to fortification, recoveries increased to 71–95% even after frozen storage for 2–4 weeks. Cys–HCI was added during analysis of 53 untreated items. Recoveries improved an average of 15% with Cys–HCI. Without Cys–HCI, recoveries were erratic (20–98%), but with Cys–HCI, recoveries were 68–113%. Other antioxidants (sodium sulfite, butylated hydroxyanisole, butylated hydroxytoluene, and vitamins A and C) also were evaluated as ETU preservatives. When lettuce was treated first with sodium sulfite and then fortified with ETU, recoveries averaged 86%; without sodium sulfite, they averaged 1%. The other antioxidants were less effective for preserving ETU in lettuce, giving only 8–46% recoveries. The effect of oxidizers (potassium bromate, sodium hypochlorite, and hydrogen peroxide) on ETU recovery was also determined. Recovery of ETU from a baby food product (pears and pineapple) was 82%; with oxidizers, recoveries were 0–8%.
Hard Surface Carrier Test as a Quantitative Test of Disinfection: A Collaborative Study
Authors: Hamilton Martin A , Devries Todd A , Rubino Joseph R
Published: February 2020

The hard surface carrier test (HSCT) recently was proposed as a qualitative test for disinfectant efficacy. A collaborative study of HSCT led to a suggested performance standard of ≤2 or 3 positive carriers out of 60 tested. Subsequently, it was discovered that HSCT can be used as a quantitative test, because the HSCT protocol requires measurement of inoculum level on some carriers. The data allow estimation of the log10 reduction in number of active bacteria. Producers, consumers, and policymakers will be better able to discuss merits of alternative performance standards if the focus is on log reduction of organisms rather than on number of positive carriers. Data from the collaborative study were reanalyzed from this quantitative viewpoint. If the point estimate of log reduction is LR and the 99% lower confidence limit estimate is LLR, the LR values ranged from 7.0 to 9.0 and the LLR values were greater than 6.0 for all disinfectants except the negative control formulation. The total variance for estimated LR is the sum of inter laboratory and intralaboratory variances. The total variance for LR was 0.095 for Pseudomonas aeruginosa, 0.251 for Staphylococcus aureus, and 0.118 for Salmonella choleraesuis. Percentages of the variance due to interlaboratory variability were 11% for P. aeruginosa, 52% for S. aureus, and 25% for S. choleraesuis. Chances of making false-effective and false-ineffective decisions can be calculated for the quantitative HSCT. The performance standard can be based on LLR.
Gas Chromatographic/Mass Spectrometric Confirmation of Leucomalachite Green in Catfish (Ictalurus punctatus) Tissue
Authors: Turnipseed Sherri B , Roybal José E , Hurlbut Jeffrey A , Long Austin R
Published: February 2020

A gas chromatographic/mass spectrometric (GC/MS) method was developed to confirm the presence of leucomalachite green (LMG), a metabolite of the triphenylmethane dye malachite green (MG), in catfish tissue. Residues were isolated according to a previously described liquid chromatographic (LC)A/IS spectrometric analysis of MG and LMG in fish. In our isolation procedure, analytes are extracted from tissue with acetonitrile–buffer, partitioned into CH2CI2, and applied to neutral alumina and propylsulfonic acid solid-phase extraction cartridges. Before GC/MS analysis, extracts prepared for the LC determinative method are eluted from a cyano solid-phase extraction cartridge, extracted into organic solvent, and concentrated for GC/MS analysis. Selected ion monitoring was performed by using 5 diagnostic ions (m/z 330,329,253,210, and 165) of LMG. The method was validated by confirming LMG in tissue fortified with mixtures of MG and LMG (5 and 10 ng/g each) and in tissue from fish that had been exposed to low levels of MG.
Identification and Measurement of β-Lactam Antibiotic Residues in Milk: Integration of Screening Kits with Liquid Chromatography
Authors: Hark-Khan Raida , Moats William A
Published: February 2020

A procedure for identifying and quantitating violative β-lactams in milk is described. This procedure integrates β-lactam residue detection kits with the multiresidue automated liquid chromatographic (LC) cleanup method developed in our laboratory. Spiked milk was deproteinized, extracted, and subjected to reversed-phase LC using a gradient program that concentrated the β-lactams. Amoxicillin, ampicillin, cephapirin, ceftiofur, cloxacillin, and penicillin G were, thus, separated into 5 fractions that were subsequently tested for activity by using 4 kits. (3-lactams in the positive fractions were quantitated by analytical LC methods developed in our laboratory. The LC cleanup method separated β-lactam antibiotics from each other and from interferences in the matrix and also concentrated the antibiotics, thus increasing the sensitivity of the kits to the β-lactam antibiotics. The procedure facilitated the task of identifying and measuring the β-lactam antibiotics that may be present in milk samples.
Improved Microbiological Assay for Folic Acid Based on Microtiter Plating with Streptococcus faecalis
Authors: Sarma Jayasri Das , Duttagupta Chandralekha , Ali Esahak , Dhar Tarun K
Published: February 2020

We have developed an improved method, using 96-well microtiter plates, for the microbiological assay of folic acid. With this method, the tedium of conventional microbiological analysis is substantially decreased. Culture volumes have been reduced 33-fold, and pipetting procedures have been simplified. Assay time has been reduced to 14 h, and sensitivity has increased 10-fold (0.1 ng/mL). Analytical recoveries range from 98 to 104%. Intra-assay and interassay variabilities are less than 11%. The assay does not require extensive manipulation of inoculum. Day-to-day variability has been minimized by using saline aliquots of the bacterial suspension stored at 4°C. The procedure is accurate, selective, and useful for direct measurement of folic acid in multivitamin formulations.
Evaluation of Commercially Available Milk Powders for Calibration of Mid-Infrared Analyzers
Authors: Lynch Joanna M , Barbano David M , Fleming J Richard
Published: February 2020

The performance of commercially available shelf-stable milk powders that upon reconstitution can be used as calibration samples for mid-infrared (IR) analyzers was evaluated. Twelve reconstituted powders and 7 raw milk samples were sent to each of 7 laboratories. Each laboratory analyzed the reconstituted powders and milk samples by IR and obtained both corrected and uncorrected data. The corrected data reflected the current calibrations (based on calibration with fresh, raw milk) of each instrument. The uncorrected data from the reconstituted powders were used to derive separate calibration equations for each instrument. Two of the 12 reconstituted powers were discarded from the analysis because of poor quality. The abilities of the powder-based and current calibrations to predict accurately the total protein and fat contents of the 7 raw milk samples were compared. For the current and powder-based calibrations, respectively, the mean differences from chemical analysis for total protein were −0.006 and 0.031%, and the standard deviations of the differences (SDD) were 0.029 and 0.029%. For fat, the mean difference for the current calibration was −0.001%, and the SDD was 0.034%. For the powder-based fat calibration, the mean differences were 0.034% (fat A only), −0.047% (fat B only), and −0.061% (fat A and fat B), and SDDs were 0.046% (fat A only), 0.036% (fat B only), and 0.056% (fat A and fat B). The reconstituted powders did not provide as accurate an IR fat calibration for testing raw milk samples as can be obtained with raw milk calibration samples. This is attributed primarily to differences in the characteristics of the fat in the reconstituted powders and in raw milk. For protein, analytical precisions for both types of calibrations were comparable, and the positive bias for the powder-based calibration is relatively easy to correct by basing calibration on true protein nitrogen instead of total nitrogen.
Optimization of a Liquid Chromatographic Method for Determination of Malachite Green and Its Metabolites in Fish Tissues
Authors: Plakas Steven M , El Said Kathleen R , Stehly Guy R , José E Roybal
Published: February 2020

A liquid chromatographic (LC) method was adapted and optimized for the determination of malachite green and its metabolites in fish plasma and muscle. Residues in plasma were extracted with acetonitrile, the extract was evaporated to dryness, and residues were resolubilized for LC analysis. Residues in muscle were extracted with an acetonitrile- acetate buffer mixture, reextracted with acetonitrile, and partitioned into methylene chloride with final cleanup on alumina and propylsulfonic acid solid-phase extraction columns. Residue levels were determined by using an LC cyano column with a Pb02 postcolumn and visible detection (618 nm). Overall mean recoveries of parent malachite green (MG-C) and its major metabolite, leucomalachite green (MG-L), from plasma were 93 and 87%, respectively, at fortification levels ranging from 25 to 250 ppb. Overall mean recoveries of MG-C and MG-L from muscle were 85 and 95%, respectively, at fortification levels ranging from 5 to 100 ppb. Relative standard deviations (RSDs) of recoveries at all fortification levels ranged from 3.9 to 7.0% for plasma and from 2.1 to 5.2% for muscle. The method was applied to incurred residues in tissues sampled from catfish after waterborne exposure to [14C]MG-C. Mean recoveries of total radioactive residues in plasma and muscle throughout the extraction and cleanup process were 88 and 87%, respectively, and corresponding RSDs for MG-C and MG-L were in the same range as those for fortified tissues. MG-L was confirmed as the major metabolite of MG-C in catfish.
Passive Diffusion through Polymeric Membranes: A Novel Cleanup Procedure for Analysis of Azinphos-Methyl and Azinphos-Ethyl Residues in Fruits and Vegetables
Authors: Ahmad Nazir , Guo Lin , Mandarakas Peter , Appleby Sbmeone , Bugueno George
Published: February 2020

A novel procedure is described for simple removal of coextractives prior to analysis of fruits and vegetables for azinphos-methyl and azinphos-ethyl residues. The solvent extract is concentrated, placed in a polymeric membrane tube, and then dialyzed in cyclohexane. Both azinphos-methyl and azinphos- ethyl diffuse into the surrounding solvent while coextractants remain inside the membrane. The dialyzing solvent is exchanged during concentration with n-hexane and analyzed without further cleanup by gas-liquid chromatography with a specific thermionic detector. The detection limit for a 25 g grape sample with final volume of extract made to 15 mL was 0.01 mg/kg. Recoveries of both residues from grapes averaged 107% (spike levels of 0.3 to 2.0 mg/kg). From a 20 g spinach sample, recoveries averaged 82% for azinphos-methyl and 72% for azinphos-ethyl when final volume of extract was made to 5 mL (spike levels of 0.1 to 1.0 mg/kg). Recoveries from 20 types of fruits and vegetables (20 g sample spiked at 1 mg/kg for both azinphos-methyl and azinphos-ethyl) were consistently greater than 70%, except for strawberries (61–67%) and avocado (28–34%). The high lipid content of avocado may impede diffusion of azinphosmethyl and azinphos-ethyl through the polymeric membrane. A field evaluation of the procedure showed a strong correlation (r = 0.957) between azinphos-methyl residues on grapes and treatments with 2 spray formulations. The membrane cleanup procedure is a simple and cost-effective alternative to other column or liquid–liquid partitioning procedures for azinphos-methyl and azinphosethyl residue analysis.
Modification of AOAC Multiresidue Method for Determination of Synthetic Pyrethroid Residues in Fruits, Vegetables, and Grains. Part II: Acetone Extraction System
Authors: Pang Guo-Fang , Chao Yan-Zhong , Fan Chun-Lin , Zhang Jin-Jie , Li Xue-Min , Liu Yong Ming , Zhao Tee-Sheng
Published: February 2020

To optimize conditions and to evaluate further a multiresidue method for pyrethroids, various extraction solvents and partitioning conditions were examined. Acetone and acetonitrile (for fruits and vegetables) and acetone–water and acetonitrile–water (for grains) were used as solvents with or without acetonitrile partitioning. Twenty crops fortified with 8 pyrethroid insecticides at low, medium, and high levels were analyzed. For limit of detection (LOD) levels, repeatability tests were completed with acetone–water as extraction solvent. Recoveries of 8 pyrethroid insecticides at LOD levels were 76.2–99.6%, with coefficients of variation (CVs) of 2.08–10.90% for narrow-bore capillary gas chromatography (GC) (n = 6) and 80.1–107.3% with CVs of 3.76–15.38% for wide-bore capillary GO (n = 6). Both acetone or acetone–water extraction with acetonitrile partitioning and acetonitrile or acetonitrile–water extraction with acetonitrile partitioning are suitable for multiresidue analysis of pyrethroid insecticides. However, acetonitrile and acetonitrile– water as extraction solvents were better than acetone and acetone–water at LOD-fortified levels. This finding was confirmed chromatographically with pear, cucumber, and barley control samples.
Rapid Determination of Neomycin by a Microbiological Agar Diffusion Assay Using Triphenyltetrazolium Chloride
Authors: Yamamoto Célia H , Pinto Terezinha J A
Published: February 2020

The standard, quantitative determination of neomycin activity by the agar diffusion method requires an 18 to 24 h incubation time. To reduce incubation time, an alternative method using triphenyltetra- zolium chloride has been developed. The inhibition zoneappears much earlier; hence, an effort was made to standardize it. This indicator develops a physical response, related to the biological one, after a determined period. A Staphylococcus epidermidis suspension inoculated into solid medium ata concentration low enough that growth is not visible can reduce the dye to formazan. There is enough contrast to read the inhibition zone optically after a7 h incubation. There is no significant difference between standard curves for 7 and 24 h incubations.Comparative assays for some pharmaceutical drugs containing neomycin in different forms show that it is possible to reduce incubation time. This modification is valid because no dispersion of results was detected by statistical analysis, which indicates that they belong to the same population. Thus, a rapid microbiological assay of neomycin has been validated and standardized
Use of Amino Acid Profiles of Pretermand Term Human Milks in Evaluating Scoring Patterns for Routine Protein Quality Assessment of Infant Formulas
Authors: Sarwar Ghulam , Darling Pauline , Ujiie Mariko , Botting Herbert G , Pencharz Paul B
Published: February 2020

Reports on the amino acid composition of human milk vary considerably with respect to concentrations of sulfur amino acids. Often, analyses forego tryptophan determination. A complete analysis of protein and amino acid concentrations was performed on human milk samples (5-10 days postpartum) collected from mothers of preterm (gestations of 25-32 weeks) and term (gestations of >36 weeks) infants. Careful attention was given to quantitate amino acids such as cysteine and tryptophan, which are vulnerable to acidic hydrolysis conditions. Differences in concentrations of total amino acids (expressed on protein basis) between preterm and term milks were small, despite the higher true protein content of preterm milk versus term milk (19.20 versus 12.60 g/L). The methionine + cyst(e)ine contents of term and preterm milks (3.72-3.84 g/100 g protein) were comparable with those reported in 1991 by the Food and Agricultural Organization/World Health Organization (FAO/WHO) for mature human milk (4.20 g/100 g protein) but higher than those reported in 1991 by the European Commission (2.9 g/100 g protein).The amino acid pattern of human milk obtained in this study confirms that the 1991 FAO/WHO amino acid scoring pattern for predicting protein quality of infant formulas is representative of the amino acid quality of both preterm and term human milks.
Liquid Chromatographic Determination of Mebendazole and its Metabolites, Aminomebendazole and Hydroxymebendazole, in Eel Muscle Tissue
Authors: Hajee Christiaan A J , Haagsma Nel
Published: February 2020

An analytical method is presented for liquid chromatographic (LC) determination of mebendazole (MBZ), hydroxymebendazole (MBZ-OH), and aminomebendazole (MBZ-NH2) in eel muscle tissue. Muscle tissue is extracted with ethyl acetate at pH 7.5. After addition of n-hexane, the extract is cleaned up and concentrated on an aminopropyl solid-phase extraction column. The test solutions are analyzed isocratically on a ChromSpher B LC column with acetonitrile–phosphate buffer, pH 6.2, as mobile phase. Limits of detection and quantitation were 0.7 and 1.1 ¼g/kg, respectively, for MBZOH; 1.4 and 2.3 ¼g/kg, respectively, for MBZ; and 1.5 and 2.1 ¼g/kg, respectively, for MBZ-NH2. Interand intraday coefficients of variation were 3.5 and 3.4%, respectively, for MBZ-OH; 2.5 and 3.1%, respectively, for MBZ; and 5.8 and 4.8%, respectively, for MBZ-NH2. Mean recoveries were 90% for MBZ, 74% for MBZ-NH2, and 92% for MBZ-OH. A linear range of applicability of at least 10–1000 ¼g/kg was found for each analyte. Incurred MBZ-NH2 (181.3 ¼g/kg) was identified in eel muscle tissue apart from MBZ (23.7 ¼g/kg) after 48 h exposure ina treatment bath containing MBZ at 1 mg/L.