bluuebunny/crossref_metadata_2025 huggingface dataset:
Determination of Ivermectin in Salmon Muscle Tissue by Liquid Chromatography with Fluorescence Detection
Authors: Rupp Heidi S , Turnipseed Sherri B , Walker Calvin C , Roybal José E , Long Austin R
Published: February 2020

abstract

A liquid chromatographic method was developed for determination of ivermectin B1a (IVR) extracted from raw fortified and incurred Atlantic salmon muscle tissues. The method was also used to determine fortified doramectin (DOR) in Atlantic salmon. Tissue extract was applied to a C8 solid-phase extraction (SPE) column, followed by a silica SPE column. Residues in the eluate were treated with trifluoroacetic anhydride and methylimidazole to dehydrate the IVR molecule and form an aromatic fluorescent moiety with a trifluoroacetic ester. This product was subsequently treated with ammonium acetate in methanol to cleave the ester and convert the functional group back to a stable alcohol form. The analytes were determined by fluorescence with excitation at 272 nm and emission at 465 nm. A Cis Hypersil column was used for analysis with a mobile phase of acetonitrile-water (90 + 10, v/v) and an oven temperature of 65°C. IVR and DOR were determined at 5 fortification levels (1, 5,10, 20, and 40 ppb). Intra-assay absolute recoveries ranged from 75 to 89% for IVR and from 73 to 85% for DOR. Relative standard deviations (RSDs) were <7% in all cases. The limit of detection (3 x baseline noise) was 0.25 ppb extracted from tissue. Incurred tissues had an average concentration of 32 ppb, with an RSD of 3%.
Confirmation of Fluoroquinolones in Catfish Muscle by Electrospray Liquid Chromatography/Mass Spectrometry
Authors: Turnipseed Sherri B , Walker Calvin C , Roybal José E , Pfenning Allen P , Hurlbut Jeffrey A
Published: February 2020

abstract

A multiresidue liquid chromatography/mass spectrometry (LC/MS) confirmation method for fluoroquinolones in catfish muscle was developed by using an electrospray interface. Residues of ciprofloxacin, enrofloxacin, sarafloxacin, and difloxacin were positively identified in catfish muscle fortified at 10-80 ppb as well as in incurred tissue. The extraction procedure is based on an LC method with fluorescence detection for determination of these compounds in catfish. Residues were extracted from catfish muscle with an acidic ethanol solution, and the extracts were cleaned up on a propyl sulfonic acid solid-phase extraction column. Chromatographic conditions were optimized to be compatible with the electrospray interface. Internal electrospray voltages were optimized so that 3 fragment ions, in addition to the protonated molecular ion, could be monitored for each residue. To obtain maximum sensitivity, separate MS acquisition programs were developed for ciprofloxacin/enrofloxacin and sarafloxacin/difloxacin pairs.
Evaluation of Fish Decomposition by Liquid Chromatographic Assay of ATP Degradation Product
Authors: Vallé Michel , Malle Pierre , Bouquelet Stephane
Published: February 2020

abstract

A liquid chromatographic method is described for quantitative determination of nucleotide derivatives adenosine 5 -triphosphate, adenosine 5 -diphosphate, adenosine 5 -monophosphate, inosine 5 '- monophosphate, inosine, and hypoxanthine in fish. The nucleotide derivatives are extracted by grinding the flesh in cold perchloric acid, recovered, precipitated from the acid by 5M KOH, and analyzed. Nucleotide derivatives and internal standard (purine) were separated in 14 min with a new elution gradient on a reversed-phase column (Kromasil C18) at 25 C. The column was regenerated in 20 min. Regression lines gave strong correlation coefficients. This new method is fast, accurate, and more objective than the Fresh-Tester, acolorimetric determination of a ratio AC used to measure freshness. It shows that the ratio K cannot be used as a universal measure of fish decomposition.
Liquid Chromatographic Method for Analysis of AU-rac-α-Tocopheryl Acetate and Retinyl Palmitate in Soy-Based Infant Formula Using a Zero-Control Reference Material (ZRM) as a Method Development Tool
Authors: Chase G William , Long Austin R , Eitenmiller Ronald R
Published: February 2020

abstract

A liquid chromatographic method is described for analysis of all-rac-α-tocopheryl acetate, tocopherols, and retinyl palmitate in soy-based infant formula. The vitamins are extracted in isopropyl alcohol and hexane-ethyl acetate without saponification and quantitated by normal-phase chromatography with fluorescence detection. All-rac-α-tocopheryl acetate and retinyl palmitate are quantitated isocratically with mobile phases of 0.5% (v/v) and 0.125% (v/v) isopropyl alcohol in hexane, respectively. Recoveries from zero control reference material soy-based formula averaged 97.2% (n = 25) for retinyl palmitate and 100% (n = 25) for all-rac-α-tocopheryl acetate. Coefficients of variation ranged from 1.21 to 2.86% for retinyl palmitate and from 1.49 to 5.16% for all-rac-α-tocopheryl acetate. The method provides a rapid, specific, and easily controlled assay for analysis of vitamin A and vitamin E in fortified infant formula. Additionally, the method eliminates use of chlorinated solvents.
Liquid Chromatographic Determination of Oxytetracycline in Edible Fish Fillets from Six Species of Fish
Authors: Meinertz Jeffery R , Stehly Guy R , Gingerich William H
Published: February 2020

The approved use of oxytetracycline (OTC) in U.S. aquaculture is limited to specific diseases in salmonids and channel catfish. OTC may also be effective in controlling diseases in other fish species important to public aquaculture, but before approved use of OTC can be augmented, an analytical method for determining OTC in fillet tissue from multiple species of fish will be required to support residue depletion studies. The objective of this study was to develop and validate a liquid chromatographic (LC) method that is accurate, precise, and sensitive for OTC in edible fillets from multiple species of fish. Homogenized fillet tissues from walleye, Atlantic salmon, striped bass, white sturgeon, rainbow trout, and channel catfish were fortified with OTC at nominal concentrations of 10, 20, 100,1000, and 5000 ng/g. In tissues fortified with OTC at 100,1000, and 5000 ng/g, mean recoveries ranged from 83 to 90%, and relative standard deviations (RSDs) ranged from 0.9 to 5.8%. In all other tissues, mean recoveries ranged from 59 to 98%, and RSDs ranged from 3.3 to 20%. Method quantitation limits ranged from 6 to 22 ng/g for the 6 species. The LC parameters produced easily in teg ratable OTC peaks without coelution of endogenous compounds. The method is accurate, precise, and sensitive for OTC in fillet tissue from 6 species of fish from 5 phylogenetically diverse groups.
Determination of Free Metabolites of Ceftiofur in Animal Tissues with an Automated Liquid Chromatographic Cleanup
Authors: Moats William A , Buckley Sandra A
Published: February 2020

Ceftiofur, a recently introduced antibiotic of the β-lactam group, is rapidly converted to both free and protein-bound metabolites when administered by the prescribed procedure, intramuscular injection. Free metabolites retain antimicrobial activity and may be detected by antibiotic-screening tests based on antimicrobial activity. It is thus desirable to distinguish ceftiofur metabolites from other antibiotics. A multiresidue procedure for β-lactams in milk was adapted for determination of free ceftiofur metabolites by collecting appropriate liquid chromatographic fractions during cleanup. Analysis of tissues from treated animals showed that the principal free metabolite was the desfuroylceftiofurcysteine conjugate.
Methods for the Recovery of Salmonella spp. from Carboxymethylcellulose Gum, Gum Ghatti, and Gelatin
Authors: Amaguaña René Miguel , Hammack Thomas S , Andrews Wallace H
Published: February 2020

Foods analyzed for Salmonella spp. by the procedure in the U.S. Food and Drug Administration's Bacteriological Analytical Manual are preenriched at a 1:9 test portion/broth ratio. Various thickening agents preenriched at this ratio become viscous and nonpipettable after 24 h incubation at 35 C. The effects of 3 factors (presence of inorganic salts, adjustment of pH, and presence of enzymes) on the viscosity of the test portion/preenrichment mixtures of various thickening agents during incubation were determined. Reduction of the viscosities of these thickening agents was accomplished as follows: carboxymethylcellulose gum, addition of cellulase to a final concentration of 0.10℅ in lactose broth preenrichment and incubation with no pH adjustment; gum ghatti, addition of NaCI to a final concentration of 0.10℅ in lactose broth preerichment and adjustment of the pH to 6.5; and gelatin, addition of papain to a final concentration of 0.10℅ in lactose broth preenrichment and adjustment of the pH to 6.8. With these modified preenrichments, one Salmonella spp. cell/25 g (representing an approximate most probable number value of 0.04 cell/g) was generally recovered from the thickening agents.
Indirect and Direct Determination of the Casein Content of Milk by Kjeldahl Nitrogen Analysis: Collaborative Study
Authors: Lynch Joanna M , Barbano David M , Fleming J Richard
Published: February 2020

The classic method for determination of milk casein is based on precipitation of casein at pH 4.6. Precipitated milk casein is removed by filtration and the nitrogen content of either the precipitate (direct casein method) or filtrate (noncasein nitrogen; NCN) is determined by Kjeldahl analysis. For the indirect casein method, milk total nitrogen (TN; Method 991.20) is also determined and casein is calculated as TN minus NCN. Ten laboratories tested 9 pairs of blind duplicate raw milk materials with a casein range of 2.42- 3.05℅ by both the direct and indirect casein methods. Statistical performance expressed in protein equivalents (nitrogen ⨯ 6.38) with invalid and outlier data removed was as follows: NCN method (wt%), mean = 0.762, sr = 0.010, SR = 0.016, repeatability relative standard deviation (RSDr) = 1.287℅, reproducibility relative standard deviation (RSDR) = 2.146%; indirect casein method (wt℅), mean = 2.585, repeatability = 0.015, reproducibility = 0.022, RSDr = 0.560℅, RSDR = 0.841; direct casein method (wt℅), mean = 2.575, sr = 0.015, sR = 0.025, RSDr = 0.597℅, RSDR = 0.988℅. Method performance was acceptable and comparable to similar Kjeldahl methods for determining nitrogen content of milk (Methods 991.20, 991.21,991.22, 991.23). The direct casein, indirect casein, and noncasein nitrogen methods have been adopted by AOAC INTERNATIONAL.
Determination of Total Fat in Foods and Feeds by the Caviezel Method, Based on a Gas Chromatographic Technique
Authors: Pendl Roger , Bauer Marcel , Caviezel Rafael , Schulthess Peter
Published: February 2020

This peer-verified method specifies a fast, easy, and reliable quantitative method to determine total fat in foods and feeds in compliance with the new definition of fat from the U.S. Food and Drug Administration. The method takes into consideration all fatty acids, from C4 to C24, and when fat is present at 0.3-100%. The validation study included 9 matrixes, with fat levels ranging from 1 to 79%. Sample and internal standard (IS; tridecanoic acid) are added to solvent (n-butyl alcohol). Fat is extracted and simultaneously saponified by potassium hydroxide. The fatty acid potassium salts are converted to fatty acids by adding an acidic aqueous salt solution, which produces a 2-phase system. The upper phase, containing the fatty acids and IS, is injected into the fat determination system. After gas chromatographic separation, the fat content is calculated from IS and fatty acid peak areas. The fat content is automatically converted to triglyceride content with a predetermined factor. Ten replicates of 9 different food samples, which cover the whole range of different contents in fat, proteins, and carbohydrates, were analyzed by the submitting and the peer laboratories. Repeatability relative standard deviation (RSDr) values ranged from 0.47 to 4.62%. Reproducibility relative standard deviation (RSDR) values ranged from 0.85 to 9.52%. These estimates include between-run variability. The method shows good accuracy. Values for standard reference materials (SRMs) are in agreement with certified values. Regression analysis of the correlation between observed fat and certified value over all matrixes and fat levels indicated good precision and absence of method bias (5 SRMs; 1-30% fat; correlation coefficient, R2 = 99.98%)
Evaluation of Passive Samplers for Analysis of Chlorinated Solvents
Authors: Amin Thakor A , Blndra Sushmeet , Narang Rajinder S
Published: February 2020

Chlorinated solvents like tetrachloroethylene, chloroform, and trichloroethylene were trapped on commercially available diffusive sampling devices and then desorbed with carbon disulfide (1.5 mL) containing surrogate standards. The extract was analyzed by gas chromatography with electron capture detection (ECD). To overcome the incompatibility of carbon disulfide with the electron capture detector, an electronically driven, high-temperature, 6- port valve was attached to the oven of a the gas chromatograph. An RTX 502 (105 m 𝖷 0.53 mm) capillary column was connected between the injector and the detector through the 6-port valve. The solvent peak was vented by rotating the valve before the peak reached the detector, and the valve was rotated to its original position before the peak due to chloroform eluted. The sampling time of 8-24 h and the use of ECD have led to detection limits of 0.5 μg/m3 for many chlorinated solvents
Gel Permeation and Florisil Chromatographic Cleanup and Gas Chromatographic Determination of Organochlorine Pesticides in Eggs
Authors: Furusawa Naoto , Okazaki Kunio , Iriguchi Sachiko , Yamaguchi Hidemasa , Saitoh Minoru
Published: February 2020

Cleanup of residual organochlorine pesticides (OCPs; α-, β-, γ-, and δ-BHC; aldrin; dieldrin; p,p′-DDE; o,p′-DDT; p,p′-DDD; and p,p′-DUX) in eggs by gel permeation chromatography (GPC) and Florisil minicolumn chromatography is described. Ten OCPs in purified extract are determined by gas chromatography with electron capture detection. The lipids extracted from whole egg are cleaned up first by GPC with an Envirogel column and an ethyl acetate-cychlohexane (1 + 1, v/v) mobile phase and then by Florisil minicolumn chromatography with 15% (v/v) diethyl ether-hexane eluant. Cleanup is highly efficient. Average recoveries of 10 spiked OCPs (0.0025-0.0125 ppm) ranged from 81 to 101%, with coefficients of variation between 1 and 14%. The detection limit was 0.001 ppm for the 10 OCPs
Characterization of Balsamic Vinegar by Multivariate Statistical Analysis of Trace Element Content
Authors: Del Signore Antonella , Campisi Barbara , Di Giacomo Franco
Published: February 2020

To characterize vinegars according to the types prescribed by Italian regulations, 8 trace elements (Cr, Mn, Co, Ni, Cu, Zn, Cd, and Pb) were determined. The data collected were successively elaborated by 3 statistical techniques: linear principal component analysis (LPCA), linear discriminant analysis (LDA), and cluster analysis (CA). LDA and LPCA best classified and discriminated the 3 types of vinegar under study, separating traditional balsamic vinegars from the other 2 types, nontraditionally aged balsamic vinegars and common vinegars. The latter 2 types were appreciably distinguished only by LDA through bidimensional analysis of discriminant scores
Determination of Ammonia and Aliphatic Amines in Food by Ion Chromatography with Double-Cell Bulk Acoustic Wave Detection
Authors: Yao Shouzhuo , Yang Xiaorong , Zhang Hong , Xie Youtao , Wei Wanzhi
Published: February 2020

An ion chromatographic (IC) method with doublecell bulk acoustic wave (DCBAW) detection is described for determination of ammonia and low-molecular- mass aliphatic amines in food. A 9 MHz AT-cut quartz crystal is used as the resonator. This detection technique provides high sensitivity, good reproducibility, and wide work region. Its sensitivity is independent of background conductivity of the mobile phase in the range 10-2700 μS. Detection limits (peak = 3 δ) for NH4+, CH3NH3+ (CH3)2NH2+and (CH3)3NH+ were 0.02, 0.05, 0.13, and 0.6 μg/mL, respectively. Relative standard deviations for NH4+, CH3NH3+, (CH3)2NH2+, and (CH3)3NH+ were 0.7,1.0, 0.8, and 1.2%, respectively. For IC analysis, the analytical column is a Shim-pack IC-C1 column and the mobile phase is 2.0 mmol/L nitric acid solution at a flow rate of 1.5 mL/min. Detection with DCBAW was compared with series bulk acoustic wave and conventional conductivity. The method was applied to analyses of egg, fish, and cured meat
A Screening Method for β-Lactams in Tissues Hydrolyzed with Penicillinase I and Lactamase II
Authors: Medina Marjorie B , Poole Dana J , Anderson M Ranae
Published: February 2020

Antibiotic residues above tolerance levels are not allowed in foods derived from farm animals. Microbial inhibition assays are used to screen antibiotics in U.S. regulatory laboratories. We developed a screening approach to classify β-lactams through selective hydrolysis of the β-lactam ring with Penase™ or lactamase II, thereby inactivating the β- lactam activity. Optimum conditions for hydrolysis of β-lactams with Penase and lactamase II were determined. p-Lactams were detected by a microbial inhibition assay and with enzyme-linked immunosorbent assays before and after hydrolysis. β- Lactams (10-100 ppb) were spiked in kidney extracts and hydrolyzed. Results indicate a pattern that tentatively classified the β-lactams into 3 subgroups. Desfuroyl-ceftiofur-cysteine, a major metabolite of ceftiofur, was clearly detected. Penicillin G, ampicillin, amoxicillin, and cloxacillin were distinguishable from cephapirin, ceftiofur metabolite, and high levels of hetacillin. Liver and kidney tissue samples were analyzed with the combined enzyme hydrolysis and screening assays, which tentatively identified the residues. This approach can speed up screening analysis of β-lactam residues prior to identification and quantitation by chromatographic analysis, thus enhancing positive identification of residues to provide a safer food supply
Structure-Retention Relationships and Physicochemical Characterization of Solutes in Thin-Layer Chromatography
Authors: Cserháti Tibor , Forgács Esther
Published: February 2020

This review enumerates and critically evaluates experimental methods and calculation procedures used to elucidate the molecular basis of thin-layer chromatography (TLC) separations in both adsorption and reversed-phase modes. It addresses the quantitative relationship between molecular structure and retention and the determination of the solute physicochemical parameters by TLC.
Solid-Phase Extraction Cleanup and Liquid Chromatography with Ultraviolet Detection of Ephedrine Alkaloids in Herbal Products
Authors: Hurlbut Jeffrey A , Carr Justin R , Singleton Emma R , Faul Kent C , Madson Mark R , Storey Joseph M , Thomas Terri L
Published: February 2020

A solid-phase extraction (SPE) cleanup and a liquid chromatographic (LC) method with UV detection is presented for analysis of up to 7 ephedrine alkaloids in herbal products. Alkaloids from herbal products are extracted with acidified buffer, isolated on a propylsulfonic acid SPE column, eluted with a high-ionic-strength buffer, and separated by LC with detection at 255 nm. LC separation is performed by isocratic elution on a YMC phenyl column with 0.1 M sodium acetate-acetic acid (pH = 4.8) containing triethyl-amine and 2% acetonitrile. Ephedrine alkaloids are completely separated in 15 min. Average recovery of 5 common alkaloids from 3 spiked matrixes is 90%, with an average relative standard deviation (RSD) of 4.4% for alkaloid spikes between 0.5 and 16 mg/g. Average quantitation of ephedrine and pseudoephedrine from 6 herbal products is 97% of declared label claims, and average quantitation of synephrine from an herbal dietary product is 85% of label claim (RSD, 3.2%). Recoveries of synephrine, norephedrine, ephedrine, pseudoephedrine, N-methylephedrine, and N-methylpseudoephedrine spiked in 4 herbal products averaged 95%. Results of ruggedness testing and of a second laboratory validation of the procedure are also presented.
A Simple Method for Evaluating Data from an Interlaboratory Study
Authors: Horwitz William , Britton Paul , Chirtel Stuart J
Published: February 2020

Large-scale laboratory- and method-performance studies involving more than about 30 laboratories may be evaluated by calculating the HORRAT ratio for each test sample (HORRAT = [experimentally found among-laboratories relative standard deviation] divided by [relative standard deviation calculated from the Horwitz formula]). The chemical analytical method is deemed acceptable per se if HORRAT ͌ 1.0 (± 0.5). If HORRAT is ≳2.0, the most extreme values are removed successively until an "acceptable" ratio is obtained. The laboratories responsible for the extreme values that are removed should examine their technique and procedures. If ≳15% of the values have to be removed, the instructions and the methods should be examined. This suggested computation procedure is simple and does not require statistical outlier tables. Proposed action limits may be adjusted according to experience. Data supporting U.S. Environmental Protection Agency method 245.1 for mercury in waters (manual cold-vapor atomic absorption spectrometry), supplemented by subsequent laboratory-performance data, were reexamined in this manner. Method-performance parameters (means and among-laboratories relative standard deviations) were comparable with results from the original statistical analysis that used a robust biweight procedure for outlier removal. The precision of the current controlled performance is better by a factor of 4 than that of estimates resulting from the original method-performance study, at the expense of rejecting more experimental values as outliers.
A Liquid Chromatographic Method for Analysis of AU-Rac-α-Tocopheryl Acetate and Retinyl Palmitate in Medical Food Using Matrix Solid-Phase Dispersion in Conjunction with a Zero Reference Material as a Method Development Tool
Authors: Chase G William , Eitenmiller Ronald R , Long Austin R
Published: February 2020

A liquid chromatographic method is described for analysis of all-rac-α-tocopheryl acetate and retinyl palmitate in medical food. The vitamins are extracted from medical food without saponification by matrix solid-phase dispersion and chromatographed by normal-phase chromatography with fluorescence detection. Retinyl palmitate and all-rac-α-tocopheryl acetate are quantitated isocratically with a mobile phase of 0.125% (v/v) and 0.5% (v/v) isopropyl alcohol in hexane, respectively. Results compared favorably with label declarations on retail medical foods. Recoveries determined on an analyte-fortified zero reference material for a milk-based medical food averaged 98.3% (n = 25) for retinyl palmitate spikes and 95.7% (n = 25) for all-rac-α-tocopheryl acetate spikes. Five concentrations were examined for each analyte, and results were linear (r2 = 0.995 for retinyl palmitate and 0.9998 for all-rac-α-tocopheryl acetate) over the concentration range examined, with coefficients of variation in the range 0.81-4.22%. The method provides a rapid, specific, and easily controlled assay for analysis of retinyl palmitate and all-rac-α-toco-pheryl acetate in fortified medical foods.
Analytical Monitoring of Citrus Juices by Using Capillary Electrophoresis
Authors: Cancalon Paul F
Published: February 2020

A capillary electrophoretic method was developed to analyze simultaneously most citrus juice components in a single procedure. After filtration, sample components are separated with an uncoated capillary tubing and a 35 mM sodium borate buffer (pH 9.3) containing 5% (v/v) acetonitrile. Analyses were run at 21 kV and 23°C. Compounds monitored regularly were the biogenic amine synephrine, some flavonoids (didymin, hesperidin, narirutin, neohesperidin, and naringin), the polyphenol phlorin, 3 UV-absorbing amino acids (tryptophan, phenylalanine, and tyrosine), ascorbic acid, an unidentified peak generated by heat and storage, and the preservatives sorbate and benzoate that can be added to citrus products. Separation can be achieved in 20 min, and each compound can be subsequently quantitated. Didymin, narirutin, and phlorin peaks were used with an artificial neural network to assess the volume of added pulp wash, a by-product of juice preparation. This method allows rapid monitoring of citrus juices, giving information on quality, freshness, and possible adulteration of the product. Similar procedures could be used to monitor other fruit juices and quantitate diverse juice blends.
Pesticide Residues in Selected Food Commodities: Results from the Danish National Pesticide Monitoring Program 1995-1996
Authors: Juhler René K , Lauridsen Milter Green , Christensen Mette Rindom , Hilbert Gudrun
Published: February 2020

The paper presents results of analyses of 4182 samples collected from January 1995 to December 1996 for the Danish National Pesticide Monitoring Program. The program basis is a random sample control supplemented with a target control. The objectives of the control are to monitor consumer exposure to health hazards and to enforce national and European Community regulations. The Danish Veterinary and Food Administration is responsible for establishing methods, data manipulation, and evaluation, but actual analyses are performed at 4 regional laboratories. In addition to a description of the Danish National Pesticide Monitoring Program on food, the effects of lowering the reporting limits are discussed. Pesticides included are those in current use as well as chlorinated pesticides like lindane, DDT, and HCB, occurring in food now primarily as a result of environmental contamination. Commodities analyzed are fruits, vegetables, cereals, bran, fish, and animal products such as meat, butter, cheese, fat, and eggs. In fruits and vegetables, residues were detected in 10% of 2515 samples, with higher incidences of detection for foreign commodities. Violation rate was 0.6%. In food of animal origin, low levels of organo- chlorine pesticides were detected in most fish samples and in more than half of the animal product samples. However, no results exceeding maximum residue limits were found. No residues of organo- phosphorus pesticides were detected in the 231 meat samples analyzed.
A Statistical Evaluation of the Youden Matched-Pairs Procedure
Authors: McClure Foster D
Published: February 2020

AOAC INTERNATIONAL currently permits investigators to use the Youden Matched-Pairs Procedure to obtain estimates of the method performance indicators repeatability and reproducibility (sr and sR, respectively). This report explains the statistical model assumptions upon which the procedure is based, provides validity tests for several of these assumptions, explains conditions under which Youdens’ “precision error” is not consistent with precision estimate sr or sR as defined by AOAC INTERNATIONAL, and indicates when precision estimates based on the procedure should be interpreted with caution or should not be used.
Repeatability and Reproducibility of Germicide Tests: A Literature Review
Authors: Tilt Nicola , Hamilton Martin A
Published: February 2020

The results of a quantitative antimicrobial assay can be summarized by the log reduction value. For an assay to be proposed as a standard method, it is usually necessary to conduct a collaborative study to demonstrate that the repeatability and reproducibility standard deviations (SDs) of the log reduction values are sufficiently small. It is not clear, however, precisely how small those SDs should be. This paper describes the results of a literature review conducted to determine the range of repeatability and reproducibility SDs for standard quantitative antimicrobial assays. The underlying premise is that, for an assay to have been accepted as a standard method, its repeatability and reproducibility SDs must have been sufficiently small. This premise implies that the repeatability and reproducibility SDs of standard assays establish de facto guidelines for acceptability. The survey comprised papers where the SDs could be extracted directly or where they could be calculated from accessible data. Papers describing suspension tests as well as hard surface tests were included. For the standard antimicrobial assays reviewed, repeatability SDs ranged from 0.25 to 1.21 and the reproducibility SDs ranged from 0.31 to 1.54.
Gas Chromatographic Analysis of Fosfomycin in Plasma for Pharmacokinetic Analysis
Authors: Webster Gregory K , Bell Robert G
Published: February 2020

An efficient method for gas chromatographic analysis of fosfomycin in plasma was developed for preliminary investigations of the bioavailability in poultry of 3 commercial complexes of fosfomycin: a levorotatory Ca(−) salt, a racemic Ca(±) salt, and a tromethamine (THAM) salt. The method was used to determine whether the less expensive racemic mixture would provide equivalent levels of fosfomycin in blood as the pure Ca(−) form and the THAM salt. The THAM salt, a more expensive product to market, was thought to have the greatest bioavailability. The assay is selective, sensitive, and applicable to pharmacokinetic analysis.
Field Detection and Sensitive Determination of Copper in Soil and Airborne Dust Particulates with1-[Pyridyl-(2)-azo]-naphthol-(2), N-Phenyl-N′-(4-methylphenyl)benzamidine, and Triton X-100
Authors: Thakur Manisha , Deb Manas Kanti
Published: February 2020

A rapid field detection and spectrophotometric method for determining copper is described. The method is based on extraction of the red Cu(II)-1-[pyridyl-(2)-azo]naphthol-(2) (PAN) complex with N-Phenyl-N'-(4-methylphenyl)benzamidine (PMPBA) in the presence of a nonionic surfactant, Triton X-100 (TX-100) at pH 8.0–9.3. The molar absorptivity of the red Cu(II)-PAN–TX-100–PMPBA complex is 1.90 × 10s L/mol/cm at 550 nm, the wavelength of maximum absorption. The detection limit is 1 ng Cu/mL aqueous solution. The system obeys Beer’s law up to a concentration of 0.4 μg Cu(II)/mL or 4 μg/10 mL in organic solution. Precision was checked by finding the relative standard deviation (RSD) for N = 10 at a level of 2.0 μg/10 mL Cu(II), which was 1.5%. The validity was tested by determining total Cu in soil and airborne dust particulate samples. Six soil and 24 dust fallout samples were analyzed. Cu concentrations in soil ranged from 2.88 ± 0.05 ppm to 9.34 ± 0.16 ppm, with RSD values ranging from 1.6 to 2.1 % (N = 5). Cu concentrations in dust fallout ranged from 33 ± 01 ppb to 557 ±10 ppb with, RSD values ranging from 1.6 to 3.0%. These data agreed very closely with results of analyses by atomic absorption spectrophotometry.
Interference by Methyl Levulinate in Determination of Total Fat in Low-Fat,High-Sugar Products by Gas Chromatographic Fatty Acid Methyl Ester (GC-FAME) Analysis
Authors: Eller Fred J
Published: February 2020

Gas chromatographic fatty acid methyl ester (GC FAME) analyses of some acid-hydrolyzed foods revealed a large peak that did not correspond to any FAME standards. The unknown peak eluted just after the C12 FAME. If the fatty acid response factor and the conversion factor for the nearest calibrated peak (C12 FAME) were used to determine the total fat, the resulting total fat determination was much higher than expected. This peak was present only in acid-hydrolyzed samples and was absent in extracts obtained with supercritical CO2 or solvents without acid hydrolysis. The compound was isolated, analyzed by mass spectrometry and nuclear magnetic resonance spectroscopy, and proved by synthesis to be methyl-4-oxopentanoate (methyl levulinate). Its source was determined to be sugar in the product formula. Levulinic acid is produced by acid hydrolysis of sugar and is transesterified by BF3 in methanolto methyl levulinate. Although methyl levulinate may appear in the GC analyses of any acid-hydrolyzed products containing sugar, if the ratio of fat to sugar is high, the impact of methyl levulinate on fat determination would be small. Onthe other hand, the presence of methyl levulinate in analyses of low-fat, high-sugar prod ucts is potentially problematic if not recognized, al though GC analysis can account for the presence of this compound.
Rapid Determination of Lysine in Biological Samples by Isocratic Liquid Chromatography
Authors: Or-Rashid Mamun M , Onodera Ryoji , Wadud Shaila , Nasser Mohamed-Emad A , Amin Mohammad R
Published: February 2020

A simple, rapid, and sensitive method was developed for detection and quantitation of lysine (Lys) in various biological samples by isocratic liquid chromatography (LC). Samples containing Lys and other amino acids were derivatized with 9-fluorenylmethyl chloroformate (FMOC-CI). The mobile phase used for isocratic elution was 50 mmol/L sodium acetate buffer (pH 4.20)-acetonitrile (43 + 57, v/v). Lys was detected with a UV detector at 265 nm. The derivatized Lys eluted from a LiChrospher 100 RP-18 (150× 4.0 mm id) column at a retention time of 5.6 min. The limit of detection was 0.73 μmol/L (signal-to-noise [S/N] ratio, 3:1), and the limit of quantitation was 2.37 μmol/L (S/N ratio, 10:1). Lys recoveries from fortified biological samples were >97.5%. Average Lys contents found in rumen fluid samples collected before the morning feeding and at 2.0,4.0, and 6.0 h after feeding were 4.26,3.34,3.58, and 3.82 μmol/L, respectively. The hydrolysate of a sample of mixed rumen microorganisms collected before the morning feeding was determined to contain 1.372 μmol/mg microbial nitrogen in the form of Lys. The Lys concentrations of human plasma, goat plasma, human urine, and goat urine were 140.0, 102.0,58.0, and 32.0 μmol/L, respectively.
A Survey of Ochratoxin A and Aflatoxins in Domestic and Imported Beers in Japan by Immunoaffinity and Liquid Chromatography
Authors: Nakajima Masahiro , Tsubouchi Haruo , Miyabe Masaki
Published: February 2020

Analyses of ochratoxin A (OTA) and aflatoxins (AFs) in 94 imported beer samples from 31 producing countries and in 22 Japanese beer samples were performed by immunoaffinity column and reversed-phase liquid chromatography (LC) with fluorescence detection. Recoveries of OTA from beer samples spiked at 25 and 250 pg/mL were 86.1 and 88.2%, respectively. Recoveries of AFs were 98.4 and 98.9%, 95.4 and 95.5%, 101.2 and 97.8%, and 98.9 and 96.0%, respectively, from beer samples spiked at 4.1 and 41 pg AF B1, 4.45 and 44.5 pg AF B2,4.7 and 47 pg AF G1, and 4.65 and 46.5 pg AF G2/mL. Detection limits were 1.0 pg/mL for OTA, 0.5 pg/mL for AFs B1 and B2, and 1.0 pg/mL for AFs G1 and G2. OTA was detected in 86 (91.5%) of 94 imported beer samples at a mean level of 10.1 pg/mL and in 21 (95.5%) of 22 Japanese beer samples at a mean level of 12.5 pg/mL. AF B1 was detected in 11 of 94 imported beer samples at a level of 0.5–83.1 pg/mL and in 2 of 22 Japanese beer samples at 0.5 and 0.8 pg/mL. Except for one beer sample from Peru, the samples contaminated with AFs were also contaminated with OTA. Although OTA was detected in most samples from various countries, AFs were detected in the beer samples from only a limited number of countries where AF contamination might be expected to occur because of their warm climate.
pH-Metric Determination of the Acid Value of Oilseeds without Titration
Authors: Kuselman Ilya , Tur’Yan Yakov I , Bourenko Tat’Yana , Goldfeld Irene , Shenhar Avinoam
Published: February 2020

A pH-metric method for determining the acid values (AVs) of oilseeds in the range 0.6–10 mg KOH/g oil or more has been developed. The method is based on rapid (1–2 min) and complete extraction of free fatty acids from an oilseed test portion into a special reagent A, transfer of an aliquot of the reagent into pH-metric cell with another reagent B, and then measurement of the conditional pH in the mixture of reagents by a glass electrode. Total time for the determination including calculation is 9–10 min. The method is rapid, cheap, simple for automation, and not labor intensive.
Liquid Chromatographic Determination of Fenbendazole Residues in Pig Tissues after Treatment with Medicated Feed
Authors: Capece Bettencourt P S , Pérez Belén , Castells Eugeni , Arboix Margarita , Cristòfol Carles
Published: February 2020

Fenbendazole (FBZ) is an anthelmintic widely used in farm animals to treat parasitic infestations, in pigs, it is administered in the food. The aim of this study was to validate an analytical method for the determination of FBZ and its metabolites in pig tissues. This method is based on oxidation of FBZ and its sulfoxide metabolite to the sulfone metabolite (FBZSO2). The limit of quantitation for this method is 20 ng FBZSO2/g for all tissues. The maximum residue limits (MRLs) established for FBZ and its metabolites in pig tissues are 50 ng/g for muscle, fat, and kidney and 500 ng/g for liver. This method is based on a liquid-liquid extraction followed by an oxidation with peracetic acid and a cleanup procedure based on 2 liquid-liquid extractions. Determination is achieved by high- performance liquid chromatography with ultraviolet detection. The present method is adjusted to the MRL established for FBZ and its metabolite residues. The analysis of the residues shows that after 72 h posttreatment, no FBZSO2 was detected in muscle, fat, and kidney and that liver levels were below the MRL.
Improved Signals Ratio Resolution Method by Optimization of Resolution Function—Simultaneous Determination of Cu(II) and Cd(II) in Water Samples
Authors: Grabarić Zorana , Iveković Damir , Sipos Laszlo , Grabarić Bozidar S
Published: February 2020

From an ecological and economical point of view, it is important to design analytical procedures for monitoring heavy metals in the environment and industrial processes in a way to minimize the use of hazardous reagents and reduce the analysis time. In this paper, a well-known dithizonate extraction-based method for the determination of many metal ions was improved by using chemometrical selectivity of the strongly overlapped spectra of copper and cadmium dithizonates in CCl4 for their simultaneous determination from a single extraction at pH 10. The individual absorption spectra, having absorption maxima difference of only 20 nm, were separated, and the metal ions were quantified by using an improved procedure for optimizing the resolving function in a recently proposed signals ratio method. The procedure consists of using many different resolving functions and plotting the difference of the mean of absolute and nonabsolute mean values of pseudosignals [PDMMV (PS)] against analyte concentrations obtained with each of the resolving functions, thus obtaining 2 straight lines having intersections that give a unique and reliable value of the unknown concentration of the individual analyte in mixture giving strongly overlapped spectra. In this way, the main drawback of the signals ratio resolution method, that is, the visual estimation of optimal resolving function, is eliminated. The proposed parameter, PDMMV (PS), was tested by using both simulated and experimental spectra. Copper was determined in the mixture with ca 20-fold excess of cadmium, and cadmium was determined in ca 10-fold excess of copper at submicromolar concentration levels.
Determination of (–)-Quinine and (+)-Quinidine by Liquid Chromatography with Diode-Laser Polarimetric Detection
Authors: Sánchez Francisco García , Díaz Aurora Navas , Pareja Angeles García , Montiel Germán Cabrera
Published: February 2020

High-performance liquid chromatography using a combination of photometric, fluorimetric, and diode-laser polarimetric detectors in series for the determination of (+)-quinidine and (–)-quinine was investigated. An RP-8 reversed-phase column and methanol-water (80 + 20, v/v) with 0.2% triethylamine as mobile phase at a flow rate of 1 mL/min were used. A dynamic range of 0-200 μg for (+)-quinidine and (+)-quinine was established, with detection limits of 17.0 and 16.7 μg, respectively. An application of this method in spiked rabbit serum was developed.
Determination of Benomyl, Diphenyl, o-Phenylphenol, Thiabendazole, Chlorpyrifos, Methidathion, and Methyl Parathion in Oranges by Solid-Phase Extraction, Liquid Chromatography, and Gas Chromatography
Authors: Yamazaki Yoshie , Ninomiya Takahiro
Published: February 2020

A simple and rapid method was developed for determination of benomyl, diphenyl (DP), o-phenylphenol (OPP), thiabendazole (TBZ), chlorpyrifos, methidathion, and methyl parathion in whole oranges. These compounds were extracted from a mixture of samples and anhydrous sodium acetate with ethyl acetate. The ethyl acetate extract was concentrated and cleaned up by passing through tandem solid-phase extraction columns consisting of anion-exchange and primary/secondary amine bonded silica. The eluate was concentrated and volume was adjusted with methanol for subsequent liquid chromatography (LC) and gas chromatography (GC). Benomyl (as methyl-2-benzimidazole carbamate, MBC), DP, OPP, and TBZ residues were determined by LC with fluorescence detection. Recoveries at 3 fortified levels (0.1,1, and 10 μg/g) ranged from 63.9 to 97.4 %, with coefficients of variation (CVs) of 1.6 to 15.5 %. Limits of detection (LODs) were 0.01 μg/g for DP, OPP, TBZ and 0.05 μg/g for benomyl. Chlorpyrifos, methidathion, and methyl parathion residues were determined by GC with flame photometric detection. Recoveries ranged from 90.4 to 97.0 %, with CVs of 2.1 to 5.9 %. LODs were 0.005 μg/g for chlorpyrifos and methyl parathion, and 0.01 μg/g for methidathion.
Determination of Aldehydes and Ketones in Ambient Air by Micellar Electrokinetic Capillary Chromatography
Authors: Fung Ying-Sing , Long Yen-Hua
Published: February 2020

A new analytical method was developed for determining 14 aldehydes and ketones of environmental interest in ambient air. The method uses 2,4-dinitrophenylhydrazine (DNPH)-coated silica cartridges for sampling, acetonitrile for preconcentration, and micellar electrokinetic capillary chromatography for separation and quantitation. With hydrodynamic sampling of 8.5 cm cartridge for 30 s, applied voltage of 25 kV, detection at 360 nm, and separation in a 60 cm long, 50 μm id fused silica column at ambient temperature (25° ± 1°C) within an electrophoretic buffer (20 mM borate/50 mM sodium dodecyl sulfate at pH 9.2 in 20% [v/v] methanol), baseline separation was obtained for DNPH derivatives of formaldehyde, acetaldehyde, acetone, acrolein, propionaldehyde, butanone, crotonaldehyde, isobutyraldehyde/butyra(dehyde, 2-pentenaldehyde, isovaleraldehyde, valeraldehyde, benzaldehyde, and hexaldehyde. Detection limits [signal-to-noise (S/N) ratio = 2] ranged from 0.10 to 0.77 mg/L, the working range was 0.3-86 mg/L, and the precision as indicated by the relative standard deviation ranged from 2.3 to 6.6% (n = 3). With 1 h sampling at 0.25 L/min and a 1000-fold enrichment, most carbonyl compounds in ambient air can be determined with de- tection limits ranging from 0.008 to 0.1 mg/m3 and a working range of 0.04-11 μg/m3. The developed method was successfully applied to the determination of carbonyl compounds in a chemical laboratory and at street level.
New and improved rotational periods of magnetic CP stars from ASAS-3, KELT, and MASCARA data
Authors: Bernhard Klaus , Hümmerich Stefan , Paunzen Ernst
Published: February 2020

Magnetic chemically peculiar (mCP) stars allow the investigation of such diverse phenomena as atomic diffusion, magnetic fields, and stellar rotation. The aim of the present investigation is to enhance our knowledge of the rotational properties of mCP stars by increasing the sample of objects with accurately determined rotational periods. To this end, archival photometric time-series data from the ASAS-3, KELT, and MASCARA surveys were employed to improve existing rotational period information and derive rotational periods for mCP stars hitherto not known to be photometric variables. Our final sample consists of 294 mCP stars, a considerable amount of which (more than 40 per cent) are presented here as photometric variables for the first time. In addition, we identified 24 mCP star candidates that show light variability in agreement with rotational modulation but lack spectroscopic confirmation. The rotational period distribution of our sample agrees well with the literature. Most stars are between 100 Myr and 1 Gyr old, with an apparent lack of very young stars. No objects were found on the zero-age main sequence; several stars seem to have evolved to the subgiant stage, albeit well before the first dredge-up. We identified four eclipsing binaries (HD 244391, HD 247441, HD 248784, and HD 252519), which potentially host an mCP star. This is of great interest because mCP stars are very rarely found in close binary systems, particularly eclipsing ones. Using archival spectra, we find strong evidence that the HD 252519 system indeed harbours an mCP star component.
Two new double-lined spectroscopic binary white dwarfs
Authors: Kilic Mukremin , Bédard A , Bergeron P , Kosakowski Alekzander
Published: February 2020

We present radial velocity observations of four binary white dwarf candidates identified through their overluminosity. We identify two new double-lined spectroscopic binary systems, WD 0311–649 and WD 1606+422, and constrain their orbital parameters. WD 0311–649 is a 17.7 h period system with a mass ratio of 1.44 ± 0.06 and WD 1606+422 is a 20.1 h period system with a mass ratio of 1.33 ± 0.03. An additional object, WD 1447–190, is a 43 h period single-lined white dwarf binary, whereas WD 1418–088 does not show any significant velocity variations over time-scales ranging from minutes to decades. We present an overview of the 14 overluminous white dwarfs that were identified by Bédard et al., and find the fraction of double- and single-lined systems to be both 31 per cent. However, an additional 31 per cent of these overluminous white dwarfs do not show any significant radial velocity variations. We demonstrate that these must be in long-period binaries that may be resolved by Gaia astrometry. We also discuss the overabundance of single low-mass white dwarfs identified in the SPY survey, and suggest that some of those systems are also likely long-period binary systems of more massive white dwarfs.
Using more frequent haemodialysis to manage volume overload in dialysis patients with heart failure, obesity or pregnancy
Authors: Sangala Nicholas , Ficheux Maxence , Fessi Hafedh , Borman Natalie , Collins Allan
Published: February 2020

Managing dialysis in patients with heart failure, pregnancy or obesity is complex. More frequent haemodialysis 5–6 days/week in randomized clinical trials has shown benefits for controlling volume overload, blood pressure and phosphorus, reducing left ventricular hypertrophy (LVH), and improving patient tolerance to therapy. Therapy prescriptions were guided by volume of urea cleared, time-integrated fluid loading control and increased phosphate–β2 microglobulin removal, with greater treatment frequency to address clinical efficacy targets. Case studies in all three categories show that treatment with more frequent haemodialysis in low-dialysate flow systems (Qd <200 mL/min, dialysate of 25–30 L/session, 5–7 days/week for 2.5–3.0 h/session) improves control of heart failure. In pregnancy, treatment 7 days/week with 30 L and 3 h/session of dialysis enabled successful delivery of infants at 32–34 weeks, with all doing well 2–5 years after birth. Obese patients with a body mass index (BMI) >35 achieved control of volume, blood pressure and uraemic symptoms compared to their prior 3 times/week in-centre haemodialysis. Greater application of more frequent haemodialysis should be considered, particularly in high-risk populations, to improve clinical care.