bluuebunny/crossref_metadata_2025 huggingface dataset:
Simultaneous Determination of the Predominant Hyperforins and Hypericins in St. John's Wort (Hypericum perforatum L.) by Liquid Chromatography
Authors: Gray Dean E , Rottinghaus George E , Gene Garrett H E , Pallardy Stephen G
Published: February 2020

Hypericin and hyperforin are believed to be among the active constituents in common St. John's wort (Hypericum perforatum L.). Presently, dietary supplements are generally standardized to contain specified levels of hypericin and hyperforin, and the related compounds, pseudohypericin and adhyperforin. A rapid method was developed for simultaneous determination of these 4 active constituents by liquid chromatography (LC). A 1 g portion of dried, finely ground leaf/flower sample is extracted with 20 mL methanol for 2 h. A 0.6 mL aliquot of the crude extract is combined with 5.4 mL acetonitrile–methanol (9 + 1) and passed through a mixed solid-phase cleanup column. The eluate is examined by LC for hyperforin, adhyperforin, hypericin, and pseudohypericin on a Hypersil reversed-phase column by using simultaneous ultraviolet (284 nm) and fluorescence detection (excitation, 470 nm; emission, 590 nm). The compounds are easily separated isocratically within 8 min with a mobile phase of acetonitrile–aqueous 0.1M triethylammonium acetate (8 + 2). Average recoveries of hyperforin and adhyperforin were 101.9 and 98.4%, respectively, for 3 sample mixtures containing concentrations ranging from approximately 0.2 to 1.5% combined hyperforins per gram dry weight. Average relative standard deviation (RSD) values for hyperforin and adhyperforin for all 3 mixtures were 18.9 and 18.0%, respectively. Average recoveries of hypericin and pseudohypericin were 88.6 and 93.3% respectively, from 3 sample mixtures containing concentrations ranging from approximately 0.2 to 0.4% combined hypericins per gram dry weight. Average RSD values for hypericin and pseudohypericin for all 3 mixtures were 3.8 and 4.2%, respectively.
Determination of Vitamin K1 in Medical Foods by Liquid Chromatography with Postcolumn Reduction and Fluorometric Detection
Authors: Ware George M , Chase G William , Eitenmiller Ronald R , Long Austin R
Published: February 2020

A liquid chromatographic (LC) method is described for the determination of vitamin K1 in medical foods. The sample is enzymatically digested with lipase and α-amylase and extracted with 1% sodium bicarbonate solution–isopropanol (1 + 1). After C18 solid-phase extraction, vitamin K1 is separated by nonaqueous reversed-phase LC, converted to the hydroquinone by postcolumn zinc reduction, and quantitated by fluorescence detection. The limit of detection is 8 pg (3 σ), and the limit of quantitation is 27 pg (10 σ) on column. Linear response ranged from 0.1 to 1.0 ng vitamin K1 (r = 0.9999). The mean recovery (n = 38) for all spiking levels was 101.6 ± 2.85%. Analysis of Standard Reference Material 1846, Infant Formula, gave a mean value of 0.95 ± 0.088 mg vitamin K/kg (K or K1?)(n = 31) with a coefficient of variation of 9.26.
Determination of Binary and Ternary Mixtures of Pesticides in Wetland Waters by Gas Chromatography Using Partial Least-Squares Analysis
Authors: García María Dolores Gil , Galera María Martínez , Espada Maria Del Carmen Pablos , Frenich Antonia Garrido , Vidal José Luis Martínez
Published: February 2020

Partial least-squares (PLS) analysis was applied for the first time to ternary and binary mixtures of pesticides producing overlapping peaks in gas chromatograms. Several preprocessing algorithms for pretreatment of data were tested for optimization of the PLS models, and the most advantageous were used in each case. Three different mixtures of pesticides were resolved with satisfactory results: parathion-methyl, chlorpyrifos-methyl, and vinclozolin; parathion-ethyl, chlorpyrifos, and triadimefon; and endosulfan sulfate and carbophenothion. The proposed models were applied to the determination of 3 mixtures of pesticides at levels of 0.02–1.00 ng/mL in wetland water samples after a preconcentration step with C18 cartridges, with recoveries ranging from 82.7 to 117.4%. The reported method is sufficiently sensitive to measure pesticide residues at the maximum allowable concentrations given in the European Union Drinking Water Directive.
Determination of Inorganic Cations by Capillary Ion Electrophoresis in Ilex paraguariensis (St. H.), a Plant Used to Prepare Tea in South America
Authors: Carducci Clyde N , Dabas Paula C , Muse Jorge O
Published: February 2020

A practical and economical capillary ion electrophoresis method with indirect UV detection at 214 nm was developed for determination of inorganic cations in plants of Ilex paraguariensis (St. H.) and their infusion known as mate tea, a very popular beverage in South America. A microwave digestion procedure was used to prepare the herbal plants, but the infusion was only diluted. The background electrolyte contained 6mM imidazole and 10mM α-hydroxyisobutyric acid, pH 4.0. The running voltage was 20 kV and temperature was 25°C. K, Na, Ca, Mg, and Mn ions were quantitated, and linearity was demonstrated between 0.6 and 120 ppm. The results were in good agreement with those obtained by flame atomic absorption and emission spectrometry. Accuracy of the method was verified by comparison with Beech leaves CRM 100, a standard reference material. The high content of minerals and several oligoelements, especially Mn in mate tea, is considered to be of nutritional interest.
Determination of Two Oxy-Pyrimidine Metabolites of Diazinon in Urine by Gas Chromatography/Mass Selective Detection and Liquid Chromatography/Electrospray Ionization/Mass Spectrometry/Mass Spectrometry
Authors: Yokley Robert A , Shen Nanzhu , Cheung Max W
Published: February 2020

An analytical method was developed for the determination in urine of 2 metabolites of diazinon: 6-methyl-2-(1-methylethyl)-4(1H)-pyrimidinone (G-27550) and 2-(1-hydroxy-1-methylethyl)-6-methyl-4(1H)-pyrimidinone (GS-31144). Two of the urine sample preparation procedures presented rely on gas chromatography/mass selective detection (GC/MSD) in the selected ion monitoring mode for determination of G-27550. For fast sample preparation and a limit of quantitation (LOQ) of 1.0 ppb, urine samples were purified by using ENV+ solid-phase extraction (SPE) columns. For analyte confirmation at an LOQ of 0.50 ppb, classical liquid/liquid partitioning was used before further purification in a silica SPE column. An SPE sample preparation procedure and liquid chromatography/electrospray ionization/mass spectrometry/mass spectrometry (LC/ESI/MS/MS) were used for both G-27550 and GS-31144. The limit of detection was 0.01 ng for G-27550 with GC/MSD, and 0.016 ng when LC/ESI/MS/MS was used for both G-27550 and GS-31144. The LOQ was 0.50 ppb for G-27550 when GC/MSD and the partitioning/SPE sample preparation procedure were used, and 1.0 ppb for the SPE only sample preparation procedure. The LOQ was 1.0 ppb for both analytes when LC/ESI/MS/MS was used.
Performance of Three Pneumatic Probe Samplers and Four Analytical Methods Used to Estimate Aflatoxins in Bulk Cottonseed
Authors: Park Douglas L , Whitaker Thomas B , Giesbrecht Francis G , Njapau Henry
Published: February 2020

The requirement by the U.S. Food and Drug Administration that agricultural products susceptible to aflatoxin contamination contain aflatoxin at levels ≤20 parts per billion for consumer-ready products has led to the establishment of inspection programs by various industries. In Arizona, cottonseed samples from 100 ton piles are collected by an accumulation of 3 or more probings with a pneumatic probe. When sampling compacted cottonseed piles, the large official pneumatic probe (7.6 × 127 cm) decreases in efficiency. Two smaller probes (1.9 × 127 cm and 1.9 × 254 cm ) were therefore developed and tested for their suitability for sampling cottonseed piles. Three rapid analytical methods (one thin-layer chromatographic and 2 immunochemical) were tested for suitability as on-site assay systems. An analysis of variance of the analytical test results showed no differences between the various probes tested. Of the rapid methods, however, only the AflaTest-P immunoaffinity column gave results similar to those of the official AOAC thin-layer chromatography method. In terms of safety, however, all methods prevent material contaminated above regulatory limits from reaching the consumer.
Multiresidue Determination of Fluoroquinolones in Eggs
Authors: Schneider Marilyn J , Donoghue Dan J
Published: February 2020

A multiresidue method was developed for the determination of fluoroquinolones in eggs. Extraction of eggs with ammoniacal acetonitrile was followed by liquid–liquid defatting, solvent evaporation, and redissolution in a small volume of buffer. The fluoroquinolones were further purified by on-line microdialysis, concentrated on a trace enrichment column, and separated by reversed-phase liquid chromatography with fluorescence detection. Norfloxacin (NOR), ciprofloxacin (CIP), and sarafloxacin (SAR) were extracted from fortified eggs over a range of 2–200 μg/kg, with recoveries of 65.7–78.9%, 65.6–77.1%, and 67.6–110%, respectively. Enrofloxacin (ENRO) was extracted over a range of 1–100 μg/kg, with recoveries of 71.5–86.7%, whereas desethylene ciprofloxacin (DCIP) and danofloxacin (DANO) were extracted over a range of 0.2–20 μg/kg, with recoveries of 68.7–90.7% and 76.0–93.8%, respectively. The limits of quantitation for the 6 fluoroquinolones were as follows: DCIP and DANO, 0.3 μg/kg; ENRO, 1 μg/kg; NOR and CIP, 2 μg/kg; and SAR, 3 μg/kg. Both SAR and ENRO incurred eggs were also successfully analyzed using this method.
Measurement of Voltammetric Peak Area and Resolution of Overlapping Peaks in the Simultaneous Determination of Copper, Lead, Cadmium, and Nickel in Environmental Matrix
Authors: Locatelli Clinio
Published: February 2020

Peak area was used for the simultaneous determination of copper(II), lead(II), cadmium(II), and nickel(II) in environmental matrixes by differential pulse voltammetry. The voltammetric measurements were performed with a conventional 3-electrode cell and an ammonia–ammonium chloride buffer, pH 9.1, as the supporting electrolyte. The analytical procedure was verified first in aqueous reference solutions and later by analysis of the standard reference materials Estuarine Sediment BCR-CRM 277 and River Sediment BCR-CRM 320. The precision and accuracy of the method, expressed as the relative standard deviation and the relative error, respectively, were <5% in all cases; the detection limit for each element under the experimental conditions used was in the range 1–5 μg/L. In the case of mutual interference between neighboring elements, an analytical procedure is proposed that is based on the standard additions technique, which allows the resolution of the overlapping voltammetric peaks.
Determination of Domoic Acid in Japanese Mussels by Enzyme Immunoassay
Authors: Kawatsu Kentaro , Hamano Yonekazu , Noguchi Tamao
Published: February 2020

Ten samples of commercial blue mussels (Mytilus edulis) from Japan were analyzed for domoic acid by an indirect competitive enzyme immunoassay (idc–EIA) based on an anti-domoic acid monoclonal antibody. Domoic acid was found in all samples at low concentrations (0.11–1.81 ng/g mussel tissue). The presence of domoic acid was confirmed by liquid chromatography coupled with immunoaffinity chromatography using an anti-domoic acid monoclonal antibody as ligand. To our knowledge, this is the first reported detection of domoic acid, a causative agent of amnesic shellfish poisoning, in Japanese mussels.
Resistance of Pseudomonas aeruginosa to Liquid Disinfectants on Contaminated Surfaces before Formation of Biofilms
Authors: Sagripanti Jose-Luis , Bonifacino Aylin
Published: February 2020

A comparison was made of the effectiveness of popular disinfectants (Cavicide, Cidexplus, Clorox, Exspor, Lysol, Renalin, and Wavicide) under conditions prescribed for disinfection in the respective product labels on Pseudomonas aeruginosa either in suspension or deposited onto surfaces of metallic or polymeric plastic devices. The testing also included 7 nonformulated germicidal agents (glutaraldehyde, formaldehyde, peracetic acid, hydrogen peroxide, sodium hypochlorite, phenol, and cupric ascorbate) commonly used in disinfection and decontamination. Results showed that P. aeruginosa is on average 300-fold more resistant when present on contaminated surfaces than in suspension. This increase in resistance agrees with results reported in studies of biofilms, but unexpectedly, it precedes biofilm formation. The surface to which bacteria are attached can influence the effectiveness of disinfectants. Viable bacteria attached to devices may require dislodging through more than a one-step method for detection. The data, obtained with a sensitive and quantitative test, suggest that disinfectants are less effective on contaminated surfaces than generally acknowledged.
Determination of Hydrocarbon Types in Petroleum and Coal-Derived Products by Thin-Layer Chromatography/Densitometry
Authors: Cebolla Vicente L , Membrado Luis , Vela Jesús , Garriga Rosa , Henrion Patrick , Domingo María P , González Paula
Published: February 2020

Different methodologies based on thin-layer chromatography (TLC)/densitometry were used to separate and quantitate hydrocarbon types in middle distillates (gas oil), heavy distillates (lubricant) from petroleum, and coal-derived products. Thus, petroleum products were separated into saturates and aromatics by development, using n-hexane (9 min) followed by dichloromethane (4.5 min), of silica gel plates impregnated with berberine sulfate. Detection of saturates and aromatics was performed by fluorescence scanning using 365 nm as the excitation wavelength. Alternative detection of aromatics can be performed on either silica gel or berberine-impregnated plates by using ultraviolet (UV) densitometry at 250 nm. On the other hand, polar coal-derived products were separated into aromatics, polar compounds, and uneluted components by using silica gel plates and development with toluene (12 min), followed by dichloromethane–methanol (95 + 5, v/v), with detection by UV densitometry at 250 nm. In all cases, external standard calibration was used for quantitation. Results were validated by using standard methods or well-established techniques of the petrochemical industry. The potential usefulness of TLC/densitometry is discussed.
Determination of Phenylephrine Hydrochloride by Flow Injection Analysis with Chemiluminescence Detection
Authors: Mestre Yolanda Fuster , Zamora Luis Lahuerta , Calatayud José Martínez
Published: February 2020

A new method is proposed for the determination of phenylephrine hydrochloride by flow injection analysis with direct chemiluminescence detection. The method is based on the oxidation of the drug by potassium permanganate in sulfuric acid medium at 80°C. The calibration graph is linear over the range 0.03–8 ppm phenylephrine hydrochloride, with a relative standard deviation (n = 51, 0.5 ppm) of 1.1% and sample throughput of 134/h. The influence of 38 different foreign compounds was tested, and the method was applied to the determination of phenylephrine hydrochloride in 8 different pharmaceutical formulations.
Long-Term Monitoring of Atrazine Contamination in Soil by ELISA
Authors: Kramer Karl , Lepschy Johann , Hock Bertold
Published: February 2020

An enzyme-linked immunoassay (ELISA) was used for screening atrazine residues in soil. Samples were annually collected in Southern Germany between 1993 and 1998. An average of 419.5 samples was analyzed per year amounting to 2517 samples. The fraction of positive samples defined by atrazine concentrations >100 μg/kg soil decreased successively from 8% (corresponding to 33 samples) in 1993 to 0.6% (corresponding to 2 samples) in 1998. All positive samples and a selection of negative samples were subsequently validated by HPLC. Comparison of ELISA and HPLC data yielded correlation coefficient values of r= 0.958–0.981 (n= 18–47), except for 1995 when only a correlation of r= 0.864 (n= 18) was obtained. Four samples were overestimated and another 4 were underestimated with respect to the atrazine threshold value of 100 μg/kg soil as revealed by HPLC validation. Thus, 99.68% of 2517 analyzed samples were correctly evaluated. The precision and reproducibility of the ELISA were adequate for a prescreening tool. The low cost per sample and the high sample throughput are not yet achievable by conventional analytical methods. The described combination of ELISA and HPLC has the potential to take advantage of both methods and to restrict determination errors to a minimum.
Simultaneous Determination of E- and Z-Guggulsterones in Dietary Supplements Containing Commiphora mukul Extract (Guggulipid) by Liquid Chromatography
Authors: Nagarajan Mythili , Waszkuc Ted W , Sun Jidong
Published: February 2020

Guggulipid, the standardized product from the extraction of the ole-gum-resin from the Commiphora mukul plant, has been marketed as a hypolipidemic agent. The ketosteroids, cis- and trans-4,17(20)-pregnadiene-3,16-dione, known as E- and Z-guggulsterones, respectively, are the main ingredients in guggulipid. A liquid chromatographic method was developed for simultaneous determination of E- and Z-guggulsterones in guggulipid preparations using synthetic E- and Z-guggulsterone standards. Realtively low amounts of guggulsterones (E and Z) were found in commercial guggulipid preparations in comparison with the manufacturer's claim of 2.5%. The mixture of E- and Z-guggulsterones was extracted and separated on a Symmetry C18 reversed-phase column, with a mobile phase of acetonitrile–water (46 + 54, v/v) and detected at 242 nm. The retention times of E- and Z-guggulsterones are approximately 8 and 11 min, respectively. Assay quantitation was based on the calibration curve obtained from a mixture of synthetic standard E- and Z-guggulsterones. Experimental data on selectivity, linearity, accuracy, and recoveries are presented.
Sensitive Spectrophotometric Determination of Nitrite in Human Saliva and Rain Water and of Nitrogen Dioxide in the Atmosphere
Authors: Helaleh Murad I H , Korenaga Takashi
Published: February 2020

A new simple, sensitive, and selective spectrophotometric method was developed for the determination of nitrite. The method is based on the reaction of nitrite with sulfathiazole in acidic medium to form a diazonium cation, which is subsequently coupled with N-(1-naphthyl)ethylenediamine dihydrochloride to form a highly stable, violet azo dye. The reaction product has an absorption maximum at 546 nm and obeys Beer's law over a nitrite range of 0.054–0.816 μg/mL. The molar absorptivity of the colored compound is 4.61 × 104 L/(mol·cm). The detection limit is 12.1 μg/L. The relative standard deviation is 0.85% for 5 determinations of nitrite at 0.27 μg/mL. The reproducibility and validity of the proposed method are discussed in the present paper. The simplicity of the method is demonstrated by the high stability of the azo-dye product as well as the short time required for its complete formation in a reaction at room temperature without pH control or extra extraction. The sensitivity of the method is shown by the successful determination of nitrite in human saliva and rain water, and of nitrogen dioxide in the atmosphere. The results compare favorably with those obtained by the reference method. The selectivity of the method is indicated by its freedom from most interferences, even at high concentrations of nitrate (500 μg/mL).
Sequential-Injection Procedure for Determination of Iodide in Pharmaceutical and Drinking Water Samples by Catalytic Reaction with Spectrophotometric Detection
Authors: Erustes José Antonio , Forteza Rarel , Cerdà Victor
Published: February 2020

A novel sequential-injection system was developed for determination of iodide at very low concentrations by using a kinetic method. The method is based on the catalytic effect of iodide on the redox reaction between Ce4+ and As3+ first described by Sandell and Kolthoff. The calibration curve is constructed by measuring the decrease of Ce4+ absorbance versus iodide concentration with a delay time of 30 s. The detection limit is 1.5 μg/L, the working temperature is 45°C, and the working range is 0.002–0.5 mg/L. Reasonable agreement was obtained when the method was applied to pharmaceutical and drinking water samples. The method has a sample throughput of approximately 15/h.
Simultaneous Determination of all-trans-Retinoic Acid, β-Carotene, and Vitamin A in Galenic Preparations by Liquid Chromatography
Authors: Pucci Vincenzo , Bugamelli Francesca , Mandrioli Roberto , Raggi Maria A
Published: February 2020

The concentrations of vitamin A, β-carotene, and all-trans-retinoic acid in oral preparations were determined in a single analysis by a method based on isocratic, reversed-phase liquid chromatography (LC). The LC system consisted of a C18 column, a mobile phase of acetonitrile, dichloromethane, methanol, and water and a UV detector set at 330 nm. The linearity ranges were 25–250 ng/mL for trans-retinoic acid and vitamin A, and 100–1000 ng/mL for β-carotene. This LC method for the determination of retinoids is simple, precise, and accurate. No extraction procedure is required before the chromatographic analysis; only a suitable dilution is necessary. The method proved to be reliable, fast, and economical. Furthermore, this method is indicative of stability, because it allows for the determination of degradation products such as 13-cis-retinoic acid.
Comparison of Three Analytical Methods for Quality Control of Clozapine Tablets
Authors: Raggi Maria Augusta , Pucci Vincenzo , Bugamelli Francesca , Volterra Vittorio
Published: February 2020

Three different analytical methods for the quality control of clozapine in commercial formulations were developed and compared: a liquid chromatographic (LC) method with UV detection, a capillary zone electrophoretic (CZE) method, and a linear scan voltammetric (LSV) method. The isocratic LC procedure used a C18 reversed-phase column; the CZE method used an uncoated fused-silica capillary and phosphate buffer containing polyvinylpyrrolidone as the background electrolyte; the LSV method analyzed clozapine solutions with acidic phosphate buffer as the supporting electrolyte. The 3 methods gave similar and satisfactory results, in terms of precision and accuracy. Repeatability and intermediate precision were good (RSD% < 2.2) and accuracy, resulting from recovery studies, was between 98 and 102%. The rapidity of analysis was high for all 3 methods, especially for the LSV.
Determination of 3-Trifluoromethyl-4-Nitrophenol and 3-Trifluoromethyl-4-Nitrophenol Glucuronide in Edible Fillet Tissue of Rainbow Trout and Channel Catfish by Solid-Phase Extraction and Liquid Chromatography
Authors: Hubert Terrance D , Vue Chue , Bernardy Jeff A , Horsen Daniel L Van , Rossulek Michelle I
Published: February 2020

3-Trifluoromethyl-4-nitrophenol (TFM) is a pesticide used for the selective control of sea lampreys (Petromyzon marinus) in stream and river tributaries of the Great Lakes. To determine concentrations of TFM and TFM glucuronide in the edible fillet tissue of fish during sea lamprey control treatments, an analytical method was developed to determine the concentrations of these residues in rainbow trout (Oncorhynchus mykiss; RBT) and channel catfish (Ictalurus punctatis; CCF). Homogenized fillets were extracted with methanol–water (80 + 20). TFM and TFM glucuronide were isolated from coextractives by C18 solid-phase extraction. TFM glucuronide was hydrolyzed to TFM by the addition of β-glucuronidase to the TFM glucuronide extract. The extracts were analyzed separately by liquid chromatography with UV–visible detection. Recoveries from TFM-fortified CCF and RBT tissues were 84.1 and 96.1%, respectively. The method detection limits (MDLs) are 2.4 ng/g for TFM-fortified tissues of CCF and 3 ng/g for those of RBT. Recoveries were 78.8 and 77%from TFM glucuronide-fortified CCF and RBT tissues, respectively. The MDLs for TFM glucuronide-fortified tissues are 3.5 and 6.9 ng/g for CCF and RBT, respectively.
Determination of 3-Chloro-1,2-Propanediol in Foods and Food Ingredients by Gas Chromatography with Mass Spectrometric Detection: Collaborative Study
Authors: Brereton Paul , Kelly Janet , Crews Colin , Honour Sarah , Wood Roger , Davies Ann ,   Collaborators:, Anklam E , Baigrie B , Diserens H , Drake P , Ebden C , Fukue N , Hageman L , Louter H , McBreen M , Perfetti G A , Sayer P , Slaiding I R
Published: February 2020

The results of a collaborative study are reported for the determination of 3-chloro-1,2-propanediol (3-monochloropropane-1,2-diol; 3-MCPD) in a wide range of foods and food ingredients, using gas chromatography with mass spectrometric detection and incorporating the use of a deuterated internal standard. After a pretrial study, 12 laboratories (6 United Kingdom, 1 Switzerland, 1 Japan, 2 United States, 1 The Netherlands, and 1 from the European Commission) were asked to analyze 12 test materials (as known duplicates or split-level samples) by using a prescribed procedure. The test materials consisted of duplicate samples of acid-hydrolyzed vegetable protein (containing 3-MCPD at 0.029 mg/kg), malt extract (0.055 mg/kg), wholemeal bread crumbs (0.030 mg/kg), salami (0.016 mg/kg), cheese alternative (0.043 mg/kg), and soup powder (split levels at 0.045 and 0.041 mg/kg). Repeatability ranged from 0.005 to 0.013 mg/kg and reproducibility, from 0.010 to 0.027 mg/kg, for the samples tested. Precision values were well within statistically predicted levels (HORRAT values of <1 for 5 of the 6 matrixes tested) and within method criteria prepared by a joint working group composed of the United Kingdom Ministry of Agriculture, Fisheries and Food and industry representatives. The study demonstrated the satisfactory validation of the method for quantifying 3-MCPD at levels of ≥0.010 mg/kg. The limit of detection derived from separate in-house studies was estimated to be 0.005 mg/kg. The method was adopted First Action by AOAC INTERNATIONAL.
Identification of Hydrolyzed Inulin Syrup and High-Fructose Corn Syrup in Apple Juice by Capillary Gas Chromatography PVM 4:1999
Authors: Low Nicholas H , McLaughlin Michael A , Page Samuel W , Canas Benjamin J , Brause Allan R , Low Nicholas H
Published: February 2020

A peer-verified, gas chromatographic (GC) method is presented for the identification of hydrolyzed inulin syrup (HIS) and high-fructose corn syrup (HFCS) in apple juice. The procedure involves determining the Brix value of the apple juice or apple juice concentrate and preparing a dilution of the test sample to 5.5° Brix. A 100 μL aliquot of the 5.5° Brix test solution is then freeze-dried in a GC autosampler vial. The sugars in the freeze-dried residue are converted to trimethylsilyl derivatives, by the addition of an appropriate silylation reagent, and the vial is heated at 75°C for 30 min. After derivatization, the solution is introduced into a gas chromatograph where the analytes are separated on a 30 m, 0.25 mm id DB-5 column. The method can use hydrogen, helium, or nitrogen as the carrier gas. The analytes and marker compounds are measured by use of a flame ionization detector. Commercial apple juice concentrates were diluted with one of the 2 syrups at 2 levels. Dilution was ascertained by the presence of retrograde sugar markers found in the 2 sugar syrups. All 3 laboratories involved in the study were able to identify the correct diluent in the blind, randomly coded, apple juice test portions. The levels of dilution in the test portions were 0, 6.9% (HIS), 16.0% (HIS), 8.1% (HFCS), and 17.0% (HFCS). No false positive results were reported. Quantitative conclusions can be drawn when the same syrup is used for dilution and as a reference standard.
Moisture Variations in Brine-Salted Pasta Filata Cheese
Authors: Kindstedt Paul S
Published: February 2020

A study was made of the moisture distribution in brine-salted pasta filata cheese. Brine-salted cheeses usually develop reasonably smooth and predictable gradients of decreasing moisture from center to surface, resulting from outward diffusion of moisture in response to inward diffusion of salt. However, patterns of moisture variation within brine-salted pasta filata cheeses, notably pizza cheese, are more variable and less predictable because of the peculiar conditions that occur when warm cheese is immersed in cold brine. In this study, cold brining resulted in less moisture loss from the cheese surface to the brine. Also it created substantial temperature gradients within the cheese, which persisted after brining and influenced the movement of moisture within the cheese independently of that caused by the inward diffusion of salt. Depending on brining conditions and age, pizza cheese may contain decreasing, increasing, or irregular gradients of moisture from center to surface, which may vary considerably at different locations within a single block. This complicates efforts to obtain representative samples for moisture and composition testing. Dicing the entire block into small (e.g., 1.5 cm) cubes and collecting a composite sample after thorough mixing may serve as a practical sampling approach for manufacturers and users of pizza cheese that have ready access to dicing equipment.
Moisture Nonuniformity and Sampling Errors in Large Cheddar Cheese Blocks
Authors: Barbano David M
Published: February 2020

A study was made of the impact of nonuniform moisture distribution in 290 kg blocks of cheese on the accuracy of sampling the cheese for moisture content. The range of moisture from center to outside surfaces of the blocks was about 5%. The temperature gradient, developed in the first 24–48 h after cheese making, drove the moisture migration from warm to cold areas in the cheese blocks during initial cooling. The moisture gradient from center to outside of each block, the non-symmetrical nature of the gradient, and the actual length of the core sample all contributed to random and systemic error in sampling within a single cheese plant. It was concluded that average moisture differences from vat to vat in a factory were small, and large variations in moisture tests were due to sampling errors.
Movement of Moisture in Refrigerated Cheese Samples Transferred to Room Temperature
Authors: Emmons Douglas B , Bradley Robert L , Campbell Carol , Sauvé J Paul
Published: February 2020

When cheese samples refrigerated at 4°C in 120 mL plastic tubs were transferred to room temperature at 23°C, moisture began to move from the warmer surface to the cooler interior; the difference after 1 h was 0.2–0.4%. Others had observed that moisture moved from the interior of warmer blocks of cheese to the cooler surface during cooling at the end of cheese manufacture. In loosely packed cheese prepared for analysis, part of the moisture movement may have been due to evaporation from the warmer surface and condensation on the cooler cheese. It is recommended that cheese be prepared for analysis immediately before weighing. Cheese samples that have been refrigerated, as in interlaboratory trials, should also be remixed or prepared again.
Measuring Moisture in Cheese by Near Infrared Absorption Spectroscopy
Authors: McKenna David
Published: February 2020

Data in the literature indicate that the measurement of moisture in cheese by near infrared transmittance (NIT) is more accurate than by reflectance (NIR). The accuracy of the NIT measurement (SEP) was calculated for Edam, Gouda, Brie, Colby, and Cheddar. A range of SEP values (0.12–0.35) was obtained using different methods of calibration for different types of samples. There was close agreement between these results, as they related to the precision of the reference method. The calibration validation technique described as Standard Error of Cross Validation (SECV) generated results that compared very closely to the equivalent SEP values for independent sample sets.
Determination of DiazaCon in Quail Feed and Quail Serum by Ion Pair Reversed-Phase Chromatography
Authors: Johnston John J , Goodall Margaret J , Hurley Jerome C , Yoder Christi A , Miller Lowell A
Published: February 2020

Liquid chromatographic (LC) methods were developed for quantitating the potential avian contraceptive DiazaCon in quail feed and serum. DiazaCon was extracted from ground quail feed with basic n-butyl chloride. The n-butyl chloride extract was evaporated to dryness. The DiazaCon residues were dissolved in an aqueous methanolic ion pairing solution and quantitated by LC at 206 nm. Avian sera was combined with an equal volume of a pH 4 aqueous solution of ion pairing reagent and filtered to remove interfering proteins. DiazaCon was quantitated by LC. Mean recoveries for 500 and 2000 ppm fortified feed were 89.1 and 91.0%, respectively. The mean recovery for sera fortified at 5 levels ranging from 35 to 2000 ppm was 84.9%. Method limits of detection were approximately 14 and 13 ppm for feed and sera, respectively.
Separation and Quantitation of Hazardous Wastes from Abrasive Blast Media
Authors: Hwang Jiann-Yang , Jeong Mijeong Lee
Published: February 2020

A sample of glass bead abrasive blasting material (ABM) waste, received from Robins Air Force Base (Georgia), was examined to determine whether the waste could be rendered nonhazardous by separating paint contaminants from the ABM. The sample was analyzed with size distribution and toxicity characteristics leaching procedure. A Microtrac analyzer was used to measure the size of fine particles (−325 Tyler mesh), and scanning electron microscopy analysis was performed to identify the nature of the contaminants in the ABM waste. Tests using froth flotation, magnetic separation, desliming, and acid washing were conducted to develop a process for removing the contaminants. A pilot plant test using the developed process rendered 82.1% or the ABM waste material nonhazardous.
Determination of Trace Levels of Manganese in Various Biological and Environmental Samples by Atomic Absorption Spectrometry after Solid–Liquid Extraction and Preconcentration with the Ion Pair Formed by the Nitroso-S Anion and the Tetradecyldimethylbenzylammonium Cation
Authors: Taher Mohammad Ali , Dehzoei Ali Mostafavi
Published: February 2020

Manganese is quantitatively retained by 2-nitroso-1-naphthol-4-sulfonic acid (nitroso-S) and tetradecyldimethylbenzylammonium (TDBA) chloride on microcrystalline naphthalene in the pH range 9.5–10.6 from large volumes of aqueous solutions of various samples. After filtration, the solid mass consisting of the manganese complex and naphthalene is dissolved in 5 mL dimethylformamide and the metal is determined by flame atomic absorption spectrometry. Alternatively, the manganese complex can be quantitatively adsorbed on TDBA–naphthalene adsorbent packed in a column and determined similarly. About 0.2 μg manganese can be concentrated in a column from 400 mL aqueous sample with a concentration as low as 0.5 ng/mL. Eight replicate determinations of manganese at 0.8 μg/mL gave a mean absorbance of 0.156 for the final solution with a relative standard deviation of 1.4%. The sensitivity for 1% absorption was 23 ng/mL. The interference of a large number of anions and cations was studied, and the optimized conditions developed were used for trace determinations of manganese in various alloys, and in biological and environmental samples.
Solid-Phase Extraction, Separation, and Visible Spectrophotometric Determination of Trace Amounts of Iron in Water Samples
Authors: Yamini Yadollah , Amiri Nayyereh
Published: February 2020

A simple and reliable method is presented for the rapid extraction, separation, preconcentration, and determination of iron as its bathophenanthroline complex by the use of octadecylsilica membrane disks and spectrophotometry. We evaluted extraction efficiency, the influence of sample matrix, type and optimum amount of extractant, flow rates of sample solution and eluent, pH, amounts of bathophenanthroline and hydroxylamine hydrochloride, breakthrough volume, and limit of detection. We also studied the effects of various cationic interferences on percent recovery of iron. Complete elution of the complex from disks was obtained with a minimal amount of solvent. The limit of detection of the proposed method is 0.080 ppb. The method was applied to the recovery and determination of iron in natural waters.
Distribution among Sample Test Results when Testing Shelled Corn Lots for Fumonisin
Authors: Whitaker Thomas B , Hagler Winston M , Johansson Anders S , Giesbrecht Francis G , Trucksess Mary W
Published: February 2020

The statistical distribution known as the compound gamma function was studied for suitability in describing the distribution of sample test results associated with testing lots of shelled corn for fumonisin. Thirty-two 1.1 kg test samples were taken from each of 16 contaminated lots of shelled corn. An observed distribution consisted of 32 sample fumonisin test results for each lot. The mean fumonisin concentration, c, and the variance, s2, among the 32 sample fumonisin test results along with the parameters for the compound gamma function were determined for each of the 16 observed distributions. The 16 observed distributions of sample fumonisin test results were compared with the compound gamma function using the Power Divergence test. The null hypothesis that the observed distribution could have resulted from sampling a family of compound gamma distributions was not rejected at the 5% significance level for 15 of the 16 lots studied. Parameters of the compound gamma distribution were calculated from the 32-fumonisin sample test results using the method of moments. Using regression analysis, equations were developed that related the parameters of the compound gamma distribution to fumonisin concentration and the variance associated with a fumonisin test procedure. An operating characteristic curve was developed for a fumonisin sampling plan to demonstrate the use of the compound gamma function.
Identification of Allantoin, Uric Acid, and Indoxyl Sulfate as Biochemical Indicators of Filth in Food Packaging by LC
Authors: Carlson Marvin , Thompson Richard D
Published: February 2020

A liquid chromatographic (LC) method was developed for the determination of allantoin, uric acid, and indoxyl sulfate in mammalian urine contaminated packaging material including paper bagging, corrugated cardboard, grayboard, and burlap bagging. The procedure involves solvent extraction and isolation of the 3 analytes by reversed-phase LC with ultraviolet detection at 225 nm for allantoin and 286 nm for uric acid and indoxyl sulfate. The composition of authentic mammalian urine such as mouse, rat, cat, dog, and human were also determined with regard to the 3 compounds of interest. A linear concentration range of 0.11–20.4, 0.02–10.0, and 0.04–30.0 μg/mL was obtained for allantoin, uric acid, and indoxyl sulfate, respectively. Limits of detection (LOD) and quantitation (LOQ) were 0.0104 and 0.0345 μg/mL for allantoin; 0.0018 and 0.0060 μg/mL for uric acid; and 0.0049 and 0.0165 μg/mL for indoxyl sulfate, respectively. Interday relative standard deviation values for a mixture of standard allantoin, uric acid, and indoxyl sulfate (n = 5) were 0.97, 0.80, and 0.94%, respectively. Analyte composition for 5 types of authentic mammalian urine varied from 0.19–6.88 mg/mL allantoin; 0.08–0.57 mg/mL uric acid; and 0.03–0.78 mg/mL indoxyl sulfate. Analyte content for 8 samples including 2 samples each for paper, cardboard, grayboard, and burlap bagging each contaminated with mouse or rat urine ranged from <LOD to 4598 μg/gm allantoin; <LOD to 202 μg/gm uric acid; and 17.5 to 616 μg/gm indoxyl sulfate. Recoveries of allantoin, uric acid, and indoxyl sulfate from 11 fortified samples (4 types) for both mouse and rat urine ranged from 28.2 to 114.1% for allantoin; 32.6 to 123.4% for uric acid; and 52.6 to 118.2% for indoxyl sulfate.
Determination of Lead and Cadmium in Ceramicware Leach Solutions by Graphite Furnace Atomic Absorption Spectroscopy: Method Development and Interlaboratory Trial
Authors: Hight Susan C
Published: February 2020

This method was developed to improve sensitivity and eliminate time consuming, evaporative pre-concentration in AOAC Method 973.82 and American Society for Testing and Materials method C738 for testing foodware. The method was developed using leach solutions obtained by leaching 9 differently decorated ceramic vessels with 4% acetic acid for 24 h at room temperature. Lead and cadmium concentrations in leach solutions were 0.005–17 600 and 0.0004–0.500 μg/mL, respectively. Concentrations were determined using peak area, phosphate chemical modifier (8.3 μg PO4−3), and a standard curve for quantitation. Optimized pre-atomization and atomization temperatures were 1300 and 1800°C, respectively, for Pb and 1100 and 1700°C, respectively, for Cd. Characteristic masses (mo) were 10 and 0.4 pg for Pb and Cd, respectively. Precision of repeated analyses of calibration solutions was ≤3% relative standard deviation. Precision of duplicate leach solution analyses on different days was 0–9% relative difference. Recovery from fortified leach solutions was 96–106%. Results obtained by this method agreed 92–110% with those of confirmatory analyses. Results of certified reference material solutions agreed 94–100% with certificate values. Pb and Cd limits of quantitation (LOQ) were 0.005 and 0.0005 μg/mL, respectively. Results from 3 trial laboratories for 4 leach solutions containing Pb and Cd concentrations of 0.017–1.47 and <0.0005–0.0864 μg/mL, respectively, agreed 89–102% with results of the author. Two attributes of this method were noteworthy: (1) Background absorbance due to organic matter was entirely absent from atomization profiles, making the use of short pre-atomization hold times (2 s) possible. (2) Instrument precision was excellent and only one determination per solution was needed. Acceptance criteria for quality control measurements and a practical procedure for estimating the method LOQ during routine regulatory analyses are described.
Determination of Five Pesticide Residues in Oranges by Matrix Solid-Phase Dispersion and Liquid Chromatography to Estimate Daily Intake of Consumers
Authors: Valenzuela Ana I , Picó Yolanda , Font Guillermina
Published: February 2020

Residues of benzoylphenylurea insecticides (diflubenzuron, hexaflumuron, and flufenuxuron), carboxamide acaricides (hexythiazox), and carbamate insecticides (benfuracarb) were determined in 150 orange fruit samples from September 1998 to June 1999, to estimate exposure of the Valencian population to oranges contaminated with these newly developed pesticides. The method for monitoring these residues is based on matrix solid-phase dispersion and liquid chromatography with UV or atmospheric pressure chemical ionization/mass spectrometry (APCI/MS) detection. Orange samples representing 11 varieties were collected from an agricultural cooperative and examined for the 5 pesticides. In 74.6% of all analyzed samples, the pesticide residues were below detection limits, which ranged from 0.002 to 0.05 mg/kg. Residues were detected in 25.4% of the samples, with higher incidences of diflubenzuron, flufenuxuron, hexythiazox, and benfuracarb; hexaflumuron residues were detected only occasionally. Two different pesticides exceeded maximum residue limits (MRLs) in 4 (2.7%) of the orange samples. Diflubenzuron surpassed 1 mg/kg MRL in 3 samples and flufenuxuron exceeded the 0.3 mg/kg MRL in 3 samples. The estimated daily intake of the 5 pesticide residues during the period was 0.077 μg/kg body weight per day. This value is much lower than the total admissible daily intake proposed by the Food and Agricultural Organization and the World Health Organization.
Examination of Proficiency and Control Recovery Data from Analyses for Pesticide Residues in Food: Sources of Variability
Authors: Horwitz William , Jackson Terry , Chirtel Stuart J
Published: February 2020

We examined a number of large proficiency and control databases supporting the values reported for pesticide residues in agricultural commodities at fractions of a part per million (mg/kg). The average recovery from >100 000 recovery records in 13 databases was 94%. The overall average single-value relative standard deviation (RSD) of the reported recoveries was 17% at a mean concentration (C) of about 10−7 (0.1 mg/kg). The average apparent HORRAT value (RSD found/RSDR predicted from the Horwitz formula [2*C−0.1505]) was 0.8. Analysis of variance indicated that about 60–70% of the variance could not be associated with any particular factor or combination of factors–analyte, commodity, method, laboratory, concentration, database, or their interactions. The most predominant factor, analyte, and its third-order interaction with laboratory and concentration contributed most of the assignable variance. These findings suggested that most of the variability of trace analysis for pesticide residues is “random” in the sense of being inherent and not assignable to specific factor fluctuations.
Liquid Chromatographic Determination of Nystatin in Pharmaceutical Preparations
Authors: Wilson Phyllis , Stewart Ann , Flournoy Valerie , Zito S William , Vancura Ales
Published: February 2020

A rapid, reversed-phase liquid chromatographic method was developed for the assay of nystatin in the bulk drug and a variety of dosage forms. Analysis was performed on a Symmetry C18 reversed-phase column using a mobile phase of methanol–water–dimethylformamide (DMF; 55 + 30 + 15, v/v/v), with detection by UV at 305 nm. Quantitation is based on the sum of the peak areas of the 2 major isomers of nystatin. The linearity of the assay was determined for a concentration range of 0.05 to 0.2 mg/mL (correlation coefficient > 0.999). Accuracies and precision showed good reproducibility.
Separation and Quantitation of Alkylphosphocholines and Analogues of Different Liposome Formulations by HPTLC
Authors: Ratz Hannelore , Schnell Horst , Rischer Matthias , Eibl Hans-Jörg
Published: February 2020

High-performance thin-layer chromatographic (HPTLC) analysis of non UV-active phospholipids in biological matrixes is a common method for separation, detection, and quantitation. Liposomes containing new alkylphosphocholines and analogues with enhanced cytostatic activity had been prepared. The liposomal formulations were designed to enable the intravenous application of the alkylphosphocholines and analogues and to reduce dose-limiting toxicities observed after oral administration. For quality control the liposomes were analyzed by HPTLC for content of 1,2-dipalmitoyl-sn-glycero-3-phosphoglycerol (DPPG), cholesterol, alkylphosphocholines, and analogues and their related compounds (main degradation products). Due to the differences in lipophily of the compounds, different mobile phases were necessary to achieve separation. Automated Multiple Development was used to reduce the number of plates and to improve the selectivity and the capacity of the chromatographic system to separate the described alkylphosphocholines and analogues from DPPG and 1,2-dipalmitoyl-sn-glycero-3-phosphocholine in one chromatographic system.
Determination of Clopidol Residues in Chicken Tissues by Liquid Chromatography: Part I. Optimization of Analytical Conditions and Comparison with AOAC Gas Chromatography Method
Authors: Pang Guo-Fang , Cao Yan-Zhong , Fan Chun-Lin , Zhang Jin-Jie , Li Xue-Min , Jia Xi , Song Wen-Bin
Published: February 2020

A simple and specific liquid chromatographic method was developed for determination of clopidol in chicken tissues. Samples were extracted with acetonitrile. The extracts were cleaned up on an alumina column and an anion exchange column. The clopidol was separated on a column (30 cm × 3.9 mm) of μBondapak C18 (10 μm) by using acetonitrile–water (20 + 80, v/v) as mobile phase, and determined quantitatively at 270 nm. Recoveries were 86.0–97.6%, with relative standard deviations of 2.14–9.42% at 0.010–2.0 mg/kg from 4 spiked matrixes of chicken muscle, egg, liver, and kidney. The limit of detection was 0.005 mg/kg. Compared with the modified AOAC gas chromatographic method, the present method is simple and fast to operate. Its results are accurate and reliable, making it favorable for environmental protection and meeting requirements for human safety. Thus, it is suitable for routine analysis of large quantities of samples.