bluuebunny/crossref_metadata_2025 huggingface dataset:
Liquid Chromatographic Determination of Triasulfuron in Soil
Authors: Gennari Mara , Ferraris Lucia , Nègre Michèle , Cignetti Alessandro
Published: February 2020

Two extraction methods were developed for the determination of triasulfuron in soil. Method I included extraction with methanol–phosphate buffer at pH 7 (2 + 1, v/v), liquid–liquid partition with dichloromethane, and cleanup on a liquid chromatographic Si adsorption solid-phase extraction tube. In Method II, Extrelut was added and the sample was then extracted with acetonitrile. In both cases, the extracts were analyzed by liquid chromatography (LC) with UV detection and the LC peak was confirmed by LC/mass spectrometry (MS). The 2 methods were tested on 3 soils having different physicochemical characteristics. Method I gave 83% average recovery and a determination limit of 0.4 μg/kg soil. Method II gave 67% average recovery and a determination limit of 2 μg/kg soil. Examples of application of Method I to field samples are reported.
Enumeration of Cryptosporidium spp. in Water with U.S. EPA Method 1622
Authors: Sinclair James L
Published: February 2020

The occurrence of Cryptosporidium parvum or other pathogenic Cryptosporidium species in water must be known in order to assess risk and determine the treatment needed to reduce Cryptosporidium oocysts to acceptable levels in finished drinking water. Because Cryptosporidium oocyst occurrence may be sparse, methods must concentrate a large volume of water and correctly identify oocysts in the concentrate. The U.S. Environmental Protection Agency Information Collection Rule (ICR) protozoan method gives low and variable recoveries of Cryptosporidium oocysts, making risk assessment difficult. Therefore, a method giving better oocyst recovery and more consistent results was needed. Method 1622 was developed with existing materials and procedures, and improvements were made in filtration, cleanup, and detection. Absolute porosity filters were used, with cleanup by immunomagnetic separation and detection by direct fluorescent antibody stain with 4′,6-diamidino-2-phenylindole (DAPI) staining for additional cell structures. Both the level and consistency of oocyst recovery were improved compared to recovery with the ICR method.
Determination of Sulfite in Oriental Herbal Medicines
Authors: Kim Young-Kyung , Koh Eunmi , Park Sang-Yong , Chang Seung-Yeup , Park Soo-Jin , Na Won-Il , Kim Hie-Joon
Published: February 2020

Sulfite was detected in 7 varieties of Oriental herbal medicines (Pueraria radix, Zingiberis rhizoma, Platycodon radix, Adenophora radix, Pinellia tuber, Astragalus radix, and Paeonia radix) on the Korean market. Sulfiting of commercial Oriental herbal medicines by fumigation with burning bituminous coal was simulated, and the accumulation of sulfite was investigated by using fresh Platycodon radix roots obtained from a growing field. The sulfite level reached a plateau in 9 h, and the maximum sulfite level found by the Monier-Williams (MW) method (AOAC 990.28) was 1020 ppm. The sulfite content in the simulated Platycodon radix sample determined by alkali extraction followed by ion-exclusion chromatography with electrochemical detection (AOAC 990.31) was approximately 17% lower on average than the MW results. Free-sulfite levels determined by acid extraction and ion-exclusion chromatography with electrochemical detection were between 19 and 49% of the MW results. The advantages of different methods for sulfite determination and the significance of the results are discussed.
Determination of Fluvalinate Residues in Beeswax by Gas Chromatography with Electron-Capture Detection
Authors: Tsigouri Angeliki , Menkissoglu-Spiroudi Urania , Thrasyvoulou Andreas T , Diamantidis Grigorios C
Published: February 2020

A simple, rapid, and accurate method is described for the determination of residual fluvalinate in beeswax. The procedure consists of partitioning on a disposable column of diatomaceous earth (Extrelut®), followed by chromatographic cleanup on a Florisil cartridge. The final extract is analyzed by capillary gas chromatography with electron-capture detection (GC–ECD). Briefly, wax samples were dissolved in n-hexane, and the solutions were sonicated and transferred to Extrelut columns. The fluvalinate was extracted with acetonitrile, and a portion of the extract was cleaned up on a Florisil cartridge. The fluvalinate was eluted with diethyl ether–n-hexane (1 + 1) and directly determined by GC–ECD. Recoveries from wax samples spiked at 5 fortification levels (100–1500 μg/kg) ranged from 77.4 to 87.3%, with coefficients of variation of 5.12–8.31%. The overall recovery of the method was 81.4 ± 3.2%, and the limit of determination was 100 μg/kg.
Sampling, Sample Preparation, and Analytical Variability Associated with Testing Wheat for Deoxynivalenol
Authors: Whitaker Thomas B , Hagler Winston M , Giesbrecht Francis G , Johansson Anders S
Published: February 2020

The variability associated with testing wheat for deoxynivalenol (DON) was measured using a 0.454 kg sample, Romer mill, 25 g comminuted subsample, and the Romer Fluoroquant analytical method. The total variability was partitioned into sampling, sample preparation, and analytical variability components. Each variance component was a function of the DON concentration and equations were developed to predict each variance component using regression techniques. The effect of sample size, subsample size, and number of aliquots on reducing the variability of the DON test procedure was also determined. For the test procedure, the coefficient of variation (CV) associated with testing wheat at 5 ppm was 13.4%. The CVs associated with sampling, sample preparation, and analysis were 6.3, 10.0, and 6.3%, respectively. For the sample variation, a 0.454 kg sample was used; for the sample preparation variation, a Romer mill and a 25 g subsample were used; for the analytical variation, the Romer Fluoroquant method was used. The CVs associated with testing wheat are relatively small compared to the CV associated with testing other commodities for other mycotoxins, such as aflatoxin in peanuts. Even when the small sample size of 0.454 kg was used, the sampling variation was not the largest source of error as found in other mycotoxin test procedures.
Recovery of Atrazine, Bromacil, Chlorpyrifos, and Metolachlor from Water Samples after Concentration on Solid-Phase Extraction Disks: Interlaboratory Study
Authors: Mueller Thomas C , Senseman Scott A , Wauchope R Don , Clegg Chris , Young Roddy W , Southwick Lloyd M , Riley Melissa B , Moye H Anson , Dumas Jose A , Mersie Wondi , Mattice John D , Leidy Ross B
Published: February 2020

An interlaboratory comparison was conducted in 1997 and 1998 to examine the feasibility of using C18 solid-phase extraction disks (Empore™) to simultaneously determine the herbicides atrazine, bromacil, and metolachlor and the insecticide chlorpyrifos in water samples. A common fortification source and sample processing procedure were used to minimize variation in initial concentrations and operator inconsistencies. The protocol consisted of paired laboratories in different locations coordinating their activities and shipping fortified water samples (deionized or local surface water) or Empore disks on which the pesticides had been retained and then quantitating the analytes by a variety of gas chromatographic methods. Average recoveries from all laboratories were >80% for atrazine, bromacil, and metolachlor, and >70% for chlorpyrifos. Detection of bromacil was unachievable at some locations because of chromatographic problems. Shipping samples between cooperating laboratories did not affect the recovery of atrazine, chlorpyrifos, or metolachlor in either matrix. Recoveries tended to be higher from disks shipped to cooperating laboratories compared with those from fortified water. Shipping disks eliminated many problems associated with the shipment of water samples, such as bottle breakage, higher shipping cost, and possible pesticide degradation. Recoveries of bromacil and metolachlor were lower from fortified surface water samples than from fortified deionized water samples. This collaborative research demonstrated that pesticides in water samples can be concentrated on solid-phase extraction disks at one location and quantitated under diverse analytical conditions at another location. The extraction efficiencies of the disks were comparable with or better than the recoveries obtained from the shipped water samples, and the problems associated with shipping water samples were eliminated by using the disks.
Use of Fuzzy Regression for Calibration in Thin-Layer Chromatography/Densitometry
Authors: Sârbu Costel
Published: February 2020

A new fuzzy regression algorithm was successfully applied to calibration in thin-layer chromatography (TLC)/densitometry. Different regression techniques were also considered, and objective quality coefficients were used for evaluation of the results. Depending on the structure of the data, the fuzzy procedure can improve the results dramatically. From the results reported in this paper and other unpublished results, it appears clear that the calibration procedure based on fuzzy regression is the most suitable regression method in quantitative TLC.
Simultaneous Determination of Amoxycillin Trihydrate and Clavulanate Potassium in Pharmaceutical Preparations by Thin-Layer Chromatography/Densitometry
Authors: Indrayanto Gunawan , Sa Tan Kiauw , Widjaja Sonja
Published: February 2020

A simple and rapid densitometric method has been developed for the simultaneous determination of amoxycillin trihydrate and clavulanate potassium in pharmaceutical preparations. After extraction of the analytes with distilled water, the extracts were spotted on precoated silica gel plates, which were then eluted with butyl acetate–methanol–glacial acetic acid–water (15 + 7.5 + 7.5 + 3, v/v). Quantitative evaluation was performed by measuring the absorbance reflectance of the analyte spots at λ = 240 nm. The densitometric method is rapid, selective, precise, and accurate and, thus, can be used for routine analysis of pharmaceutical preparations in quality control laboratories of the pharmaceutical industry.
Determination of Halofuginone and Amprolium in Chicken Muscle and Egg by Liquid Chromatography
Authors: Yamamoto Yuzo , Kondo Fusao
Published: February 2020

A liquid chromatographic (LC) method was developed for simultaneous measurement of halofuginone (HFN) and amprolium (APL) in chicken muscle and egg. HFN and APL were extracted from chicken muscle and egg with acetonitrile. In chicken egg, they were partially purified by solid-phase extraction (SPE) to separate them from impurities. The LC separation was performed on a 4.6 mm id × 250 mm TSK-gel ODS-80TM column using acetonitrile–McIlvaine buffer, pH 3.4, containing 0.01M sodium lauryl sulfate (42 + 58) as the mobile phase. Ultraviolet detection of HFN and APL was performed at wavelengths of 242 and 265 nm, respectively. Recoveries of HFN and APL from chicken muscle spiked at 0.5 μg/g were 74.8 ± 17.7 and 94.2 ± 5.0%, respectively (mean ± standard deviation [SD], n = 10). In chicken muscle, the lower limit of determination for both APL and HFN was 0.03 μg/g. Recoveries of HFN and APL from chicken egg spiked at 0.5 μg/g by a cleanup procedure using SPE were 54.6 ± 3.4 and 85.0 ± 2.4%, respectively (mean ± SD, n = 5). In chicken egg, the lower limit of determination for both APL and HFN was 0.04 μg/g.
Comparison of Amplified ELISA and Mouse Bioassay Procedures for Determination of Botulinal Toxins A, B, E, and F
Authors: Ferreira Joseph L
Published: February 2020

The amplified enzyme-linked immunosorbent assay (amp-ELISA) was compared to the mouse bioassay for determination of botulinal neurotoxin types A, B, E, and F. Twelve different toxin-producing type A, 13 proteolytic type B, 9 nonproteolytic type B, 16 type E, 8 proteolytic type F, 5 nonproteolytic type F, and 6 nontoxigenic clostridial strains were tested. The cultures were inoculated into cooked meat medium (CMM) and tryptone-peptone-glucose-yeast extract (TPGY) medium, incubated for 5 days, and then examined for biological toxicity in mice and amp-ELISA endpoints. The amp-ELISA was less sensitive in detecting toxins produced by nonproteolytic than proteolytic strains of type B and F organisms. All of the toxin-producing strains tested were positive by the AOAC method and the amp-ELISA in either undiluted TPGY or CMM culture fluids regardless of mouse toxicity level, source, or strain. Cross-reactivity was observed between some but not all of the botulinal strains tested. None of the nontoxigenic strains were positive by the amp-ELISA. Purified botulinal toxins were also assayed using these 2 methods. The sensitivity of the amp-ELISA using purified neurotoxins was about 0.1 ng/mL for types A, B, and E and about 1.0 ng/mL for type F.
Comparison of Methods for Extraction of Tobacco Alkaloids
Authors: Jones Nadiá M , Bernardo-Gil M Gabriela , Lourenco M Graço
Published: February 2020

Ultrasound and microwave techniques were used to extract tobacco alkaloids, and response surface methodology was used to optimize extraction conditions. Ultrasonic technique factors were temperature, 30–85°C; time, 3–45 min; solvent volume, 8–80 mL. Microwave extraction factors were pressure, 15–75 psi; time, 3–40 min; power, 30–90% of the maximum magnetron power of 650 W. Soxhlet and solvent AOAC-modified extraction methods were also applied after some improvements. Nicotine, nornicotine, anabasine, and anatabine were quantified by gas chromatography. A steam distillation International Standards Organization method for total alkaloid evaluation was used as reference. The results obtained by the different methods were compared using a least squares deviation test. The ultrasonic and the proposed modified-AOAC extraction method were the more convenient with regard to practicability and precision. The relative deviations (n = 5) were as follows: For the ultrasonic method in low-level alkaloid tobaccos, 0.7% nicotine and 1.4–14% minor alkaloids; in high-level alkaloid tobaccos, 2.4% nicotine and 4.5–5.1% minor alkaloids. For the modified AOAC method in low-level alkaloid tobaccos, 0.9% nicotine and 2.4–11.6% minor alkaloids; and in high-level alkaloid tobaccos, 1.7% nicotine and 2.0–2.4% minor alkaloids.
Determination of Acetochlor in Technical and Formulated Products by Capillary Gas Chromatography
Authors: Kahn Bobbi B , Tomkins David F
Published: February 2020

A peer-verified gas chromatographic (GC) method is presented for the weight percent (wt %) determination of acetochlor herbicide in technical and formulated products. During method development, the method was found to be rugged by the Youden Ruggedness Test. Two laboratories with experience in the wt % determination of acetochlor in various matrixes participated in this study. Each laboratory received 10 blind duplicate test samples of the following 5 matrixes: one acetochlor technical and 4, different, emulsifiable concentrate (EC) formulations—Harness® EC (MON 5841), Harness ® Export/Fist (MON 8435), Surpass® EC (HF), and Surpass ® EC (LF). Each participant was asked to make duplicate weighings of each of the test samples and to inject each test sample solution twice. All test samples were analyzed on the same day, and 8 data points (replicates) per matrix were obtained. The test samples were dissolved in acetone that contained dipentyl phthalate as an internal standard. They were analyzed by GC on a 15 m capillary column by using split injection and a flame ionization detector. Acetochlor (wt %) was determined by comparing the ratios of peak area of acetochlor/peak area of dipentyl phthalate internal standard obtained for the test sample and calibration solutions. Repeatability of the method, expressed as the within-laboratory (between replicates) relative standard deviation (RSDr), was found to be 0.09–0.77% for the 5 matrixes. Reproducibility of the method, expressed as the within-test sample relative standard deviation (RSDR), was found to be 0.18–0.78% for the 5 matrixes.
Visible Spectrophotometric Determination of Tantalum in Soil, Sediment, Minerals, and Alloys
Authors: Patel Khageshwar Singh , Shukla Aditya , Agarwal Neeta , Hoffmann Peter
Published: February 2020

A new, sensitive, and selective method is described for the spectrophotometric determination of Ta(V). The method is based on the extraction of the Ta(V)–F−–CV+ complex (CV+ = crystal violet cation) with a benzene solution of imidoyl derivatives (ID), i.e., N,N′-diphenylbenzamidine (DPBA), N-hydroxy- N,N′-diphenylbenzamidine, and N-(2,5-dimethyl)phenyl-p-tolylimidoylphenylhydrazine, from sulfuric acid solution; DPBA was selected for detailed study. The molar absorptivities of the Ta(V)–F−–CV+–ID complexes in the benzene solution were in the range of (1.00–1.65) × 105 L/mol·cm at 600 nm. The limit of detection was 7 ng Ta/mL (which had an absorbance greater than that of the blank + 3 standard deviations). The optimization of the analytical variables, the composition of the complex, and the effect of diverse ions in the determination of Ta are discussed. The present method was applied to the determination of Ta in environmental samples, i.e., soil, sediment, minerals, and alloys.
Determination of Sucrose Esters of Fatty Acids in Food Additive Premixes by Gas Chromatography and Confirmation of Identity by Gas Chromatography/Mass Spectrometry
Authors: Uematsu Yoko , Hirata Keiko , Suzuki Kumi , Iida Kenji , Kan Teruo , Saito Kazuo
Published: February 2020

A gas chromatographic (GC) method was developed for the determination of sucrose monoesters of fatty acids (mono-SuE) and sucrose acetate isobutyrate (SAIB) in food additive premixes. Mono-SuE and SAIB fractions were prepared by column chromatography with either a C8 or a silica gel solid-phase extraction column. The mono-SuE fraction was acetylated and applied to a wide-bore GC column (0.53 mm × 15 m) by splitless injection for determination. The SAIB fraction was applied to the GC column without derivatization. Gas chromatography/mass spectrometry was used to confirm the identity of GC peaks. The detection limits for mono-SuE and SAIB were 0.005 and 0.01%, respectively. Mono-SuE (C12, C14, C16, C18, and C18:1) and SAIB were found in commercial food additive premixes and some foods.
Simultaneous Determination of Imazalil and Its Major Metabolite in Citrus Fruit by Solid-Phase Extraction and Capillary Gas Chromatography with Electron Capture Detection
Authors: Matsumoto Hisashi
Published: February 2020

A method was developed for the simultaneous determination of imazalil and its major metabolite, R 14821, in citrus fruit. This method (designated the SPE method) is based on solid-phase extraction (SPE) and capillary gas chromatography (GC) with electron-capture detection (ECD). The SPE method is highly sensitive for both compounds (limit of detection for each: 0.001 μg/g) and is less time consuming than the previously reported method based on repeated liquid–liquid partitioning and GC–ECD. Recoveries for 3 levels of fortification (0.02, 0.2, and 2.5 μg/g) from satsuma mandarins ranged from 94.3 to 96.5% for imazalil and from 93.9 to 96.3% for R 14821, with coefficients of variation (CVs) ranging from 3.1 to 6.3% for imazalil and from 4.5 to 5.6% for R 14821. Average residual levels found in grapefruit, oranges, and lemons by the SPE method and the previously reported method, and the corresponding CVs, were similar.
Occurrence of 1,4-Dioxane in Cosmetic Raw Materials and Finished Cosmetic Products
Authors: Black Roderick E , Hurley Fred J , Havery Donald C
Published: February 2020

Surveys of cosmetic raw materials and finished products for the presence of the carcinogen 1,4-dioxane have been conducted by the U.S. Food and Drug Administration since 1979. Analytical methods are described for the determination of 1,4-dioxane in ethoxylated cosmetic raw materials and cosmetic finished products. 1,4-Dioxane was isolated by azeotropic atmospheric distillation and determined by gas chromatography using n-butanol as an internal standard. A solid-phase extraction procedure based on a previously published method for the determination of 1,4-dioxane in cosmetic finished products was also used. 1,4-Dioxane was found in ethoxylated raw materials at levels up to 1410 ppm, and at levels up to 279 ppm in cosmetic finished products. Levels of 1,4-dioxane in excess of 85 ppm in children's shampoos indicate that continued monitoring of raw materials and finished products is warranted.
Determination of Niacin in Infant Formula by Solid-Phase Extraction and Anion-Exchange Liquid Chromatography
Authors: LaCroix Denis E , Wolf Wayne R , Porter Eural , Cantellops Dennis , Chase G William , Woollard David
Published: February 2020

A peer-verified, solid-phase extraction (SPE)/anion exchange liquid chromatographic method is presented for the determination of niacin in milk-based and soy-based infant formula. Analysis is in 3 steps: test sample digestion, extraction/cleanup, and liquid chromatography (LC). Digestion uses a standard AOAC digestion procedure that involves autoclaving at 121°C for 45 min in (1 + 1) H2SO4 to free endogenous niacin from protein and to convert added niacinamide to niacin. The digest solution is adjusted to pH 6.5 with 7.5M NaOH. Acidification to pH <1.0 with (1 + 1) H2SO4 precipitates the protein. The clarified solution is then filtered, and the filtrate is brought to volume. SPE of niacin is accomplished by passing an aliquot of the digest solution through an aromatic sulfonic acid–SPE (ArSCX–SPE) column. After the column is washed with methanol and water to remove extraneous material, the niacin is eluted with 0.25M sodium acetate/acetic acid buffer at pH 5.6. An anion-exchange polystyrene–divinylbenzene column with 0.1M sodium acetate/acetic acid buffer at pH 4.0 is used for LC. Niacin is determined by UV detection at 260 nm. A standard curve is prepared by passing known amounts of niacin through the ArSCX–SPE columns used for niacin extraction. The following values for x_bar and relative standard deviation (RSD) were obtained for National Institute of Standards and Technology Standard Reference Material (NIST SRM) 1846 Infant Formula with a certified value for niacin of 63.3 ± 7.6 μg/g: Submitting laboratory.— x_bar = 59.7 ± 4.0 μg/g; RSD = >6.7%; confidence interval (CI) = ± 1.4 μg/g; n = 27. Peer laboratory.— x_bar = 56.6 ± 6.6 μg/g; RSD = >11.7%; CI = ± 4.1 μg/g; n = 8.
Determination of Phenolic Disinfectant Agents in Commercial Formulations by Liquid Chromatography
Authors: Thompson Richard D
Published: February 2020

Using liquid chromatography (LC), a convenient and versatile method was developed for the assay of disinfectant products containing the commonly used phenolic agents, alone or in combination, including phenol, 2-phenylphenol, 4-t-amylphenol, 4-chloro-3,5-dimethylphenol (PCMX), 2-benzyl-4-chlorophenol, and triclosan. The procedure involves a simple dilution or dissolution of the product aliquot or portion followed by membrane filtration and LC. The method was applied to 19 different products representing 17 manufacturers and containing from one to 4 phenolic agents. Chromatography was performed using a Zorbax SB-C18 column, acetonitrile–0.05M KH2PO4 (55 + 45, v/v) pH 3.00, as mobile phase and UV detection at 280 nm. The intralaboratory precision of the product assays ranged form 0.34–5.35% (n = 5) and recoveries via fortification varied from 96.1–103.8%. The limits of quantitation (LOQ) and detection (LOD) ranged from 5.58 × 10−5 to 2.50 × 10−4 mg/mL and from 1.76 × 10−5 to 0.67 × 10−4 mg/mL, respectively, for the 6 analytes. The response for all analytes was observed to be linear for at least a 50-fold range in concentration (0.001–0.05 mg/mL). The proposed method provides an efficient means for the isolation and quantitation of these phenolic compounds.
Procedures for Estimating Confidence Intervals for Selected Method Performance Parameters
Authors: McClure Foster D , Lee Jung-Keun
Published: February 2020

Procedures for estimating confidence intervals (CIs) for the repeatability variance (σr2), reproducibility variance (σR2 = σL2 + σr2), laboratory component (σL2), and their corresponding standard deviations σr, σR, and σL, respectively, are presented. In addition, CIs for the ratio of the repeatability component to the reproducibility variance (σr2/σR2) and the ratio of the laboratory component to the reproducibility variance (σL2/σR2) are also presented.
Synergy between Liquid Chromatographic–Pulsed Amperometric Detection and Capillary-Gas Chromatographic Methods for the Detection of Juice Adulteration
Authors: Hammond David A
Published: February 2020

The use of liquid chromatography linked with pulsed amperometric detection, and capillary-gas chromatography to detect the adulteration of fruit juices is discussed. These are 2 complementary approaches which can be used to detect the addition of sugar syrups to juices at low levels.
Routine Analysis of Ascorbic Acid in Citrus Juice Using Capillary Electrophoresis
Authors: Cancalon Paul F
Published: February 2020

A procedure to monitor citrus juice samples was established to quantitate vitamin C by capillary electrophoresis using a previously developed method. Dilution and filtration were the only preparation requirements and separation was achieved with an uncoated capillary using a 35mM sodium borate buffer (pH 9.3) containing 5% (v/v) acetonitrile at 21 kV and 23°C. Detection was performed by high speed scanning between 200 and 360 nm. From the multiwave length scan, the electropherogram at 270 nm was extracted and used to quantitate ascorbic acid. The ascorbic acid concentration was calculated with an internal standard method, with ferulic acid as internal standard. The level of ascorbic acid during analysis was stabilized with ethylenediaminetetraacetic acid and dithiothreitol was used to reduce dehydroascorbic acid to ascorbic acid to estimate the total vitamin C level. Results were similar to those obtained by liquid chromatography and the method is now used to determine routinely the level of ascorbic acid in citrus juices.
Stability and Recovery of Triazine and Chloroacetamide Herbicides from pH Adjusted Water Samples by Using Empore Solid-Phase Extraction Disks and Gas Chromatography with Ion Trap Mass Spectrometry
Authors: Mueller Thomas C , Senseman Scott A , Carson Kathy H , Sciumbato Audie S
Published: February 2020

Empore disks were used to successfully extract herbicide residues from a difficult-to-analyze surface water source and deionized water. Herbicide recoveries were lower in surface water at 7, 14, or 21 days after fortification and storage at 4°C, presumably due to chemical sorption onto precipitated organic particulates. The addition of acid to the samples, as recommended in EPA Method 525.2, did not affect recoveries of alachlor and metolachlor, but reduced recoveries of atrazine, simazine, and cyanazine. Treatment of water samples with sodium hypochlorite did not affect alachlor or metolachlor recoveries, but greatly reduced the recovery of all triazine herbicides. This indicates that addition of acid or sodium hypochlorite to water samples may be detrimental to triazine analysis.
Multiresidue Determination of Pesticides in Fruit and Vegetables by Gas Chromatography/Tandem Mass Spectrometry
Authors: Gamón Miguel , Lleó Concha , Ten Amparo , Mocholí Francisco
Published: February 2020

Pesticide residues in fruit and vegetables were determined by gas chromatography/tandem mass spectrometry (GC/MS/MS). Electron impact (EI)/MS/MS and chemical ionization (CI)/MS/MS were developed for 80 compounds, including organochlorine, organophosphorus, organonitrogen, and pyrethroids, providing unambiguous spectral confirmation for these complex matrixes. Residues were extracted from samples with acetone followed by a mixture of dichloromethane–petroleum ether. Two injections per sample were required for analysis of the entire pesticide list by EI/MS/MS and CI/MS/MS.Initial steps involving cleanup and concentration of extracts were eliminated. The excellent selectivity and good linearity allowed quantification and identification of low levels of pesticides in the most difficult matrixes. The method has been used for routine analysis of many vegetables.
Plasma Analysis of Celiprolol by HPTLC: A Useful Technique for Pharmacokinetic Studies
Authors: Savale Hema S , Pandya Kalpesh K , Gandhi Thakorbhai P , Modi Indravadan A , Modi Rajiv I , Satia Milan C
Published: February 2020

A rapid and sensitive high performance, thin-layer chromatographic (HPTLC) method has been developed for the measurement of celiprolol in human plasma and its use in pharmacokinetic studies has been evaluated. Detection and quantitation were performed without using an internal standard. A simple extraction procedure was followed for extracting celiprolol from plasma and a known amount of the extract was spotted on precoated silica gel 60 F254 plates using a Camag Linomat IV autosampler. Celiprolol was quantitated using a Camag TLC Scanner 3. The average recovery of authentic analytes (20 to 200 ng/mL) added to plasma was 72.06 ± 2.8% and the lowest amount of celiprolol that could be detected was 10 ng/mL. The method provides a direct estimate of the amount of celiprolol present in plasma. Pharmacokinetic parameters of 2 marketed preparations have also been determined after oral administration to 12 healthy human volunteers.
TLC Determination of Mebendazol and Pentoxifylline as Residues on Pharmaceutical Equipment Surfaces
Authors: Vovk Irena , Simonovska Breda
Published: February 2020

This paper presents the applicability of thin-layer chromatographic methods with a subsequent densitometric or video densitometric quantitation for determination of residues in controlling pharmaceutical equipment cleanliness. Analytical methods were developed for monitoring residues of pentoxifylline at 10 mg/m2 and mebendazol at 1 mg/m2 on stainless steel surfaces. Simulated samples were prepared by addition of a calculated amount of pharmaceutical (as a solution) on a 35 × 35 cm stainless steel surface. After evaporation of solvent, the residues were wiped with wetted cotton. The cotton was extracted with dichloromethan–methanol (1 + 1). Filtered extract was concentrated by vacuum evaporation and an aliquot applied to the plate, where standards were also applied. In the narrow concentration range near the acceptable residue limits, linear calibration curve could be obtained for both substances. The mean recovery (n = 4) obtained by densitometric quantitation was 93.4% for pentoxifylline and 85.6% for mebendazol, with coefficients of variation of 3.5 and 8.3%, respectively. Results of video densitometric quantitation did not differ significantly. However, data acquisition and evaluation is faster compared with densitometry and allows better archiving possibilities as required by the regulatory authorities. Both quantitation modes can be applied to routine control of pharmaceutical equipment cleanliness.
Supercritical Fluid Extraction of Halogenated Monoterpenes from the Red Alga Plocamium cartilagineum
Authors: Gao Donqhui , Okuda Roy , Lopez-Avila Viorica
Published: February 2020

Supercritical fluid extraction (SFE) of the marine red alga Plocamium cartilagineum, which is known to contain complex mixtures of halogenated monoterpenes, was investigated. P. cartilagineum samples were extracted by SFE with carbon dioxide and modified carbon dioxide containing up to 10% methanol at different pressure and temperature conditions to establish the optimum conditions for extraction. These conditions were then used in the extraction of halogenated monoterpenes from 2 different samples of P. cartilagineum: one from Davenport, CA, and the other from Casa Beach (San Diego, CA). Several halogenated monoterpenes isolated by conventional solvent extraction with methanol and purified by column chromatography were used as the reference compounds for the determination of the extraction efficiency in the SFE experients. Plocamium cartilagineum belongs to the red alga family—Plocamiaceae, and has been found to contain a large number of halogenated monoterpenes, whose structures typically contain 1–6 bromine and/or chlorine atoms. P. cartilagineum grows along the Pacific coast from Washington to Chile, the British Isles, Australia, and Spain. Interestingly, P. cartilagineum collected from different geographical areas in the world are all reported to produce halogenated monoterpenes, but of different structural types and halogen substitution patterns. Most of these halogenated monoterpenes have been found to exhibit varied biological activities, including antifungal, antimicrobial, and molluscicidal activity.
Enzyme Immunoassay for Aflatoxin B1-Lysine Adduct and Its Validation
Authors: Sujatha Nayak , Suryakala Sarilla , Rao Beedu Sashidhar
Published: February 2020

A simple procedure was developed for in vitro synthesis and characterization of aflatoxin B1-lysine adduct using aflatoxin B1, N-α-acetyl lysine and m-chloroperbenzoic acid (MCPBA). At a molar ratio of 1:16 (aflatoxin B1:N-α-cetyl lysine), the recovery of adduct was 62%. Analysis of the adduct by thinlayer chromatography showed a single spot (Rf= 0). Absorption spectra of the adduct showed 2 peaks at 275 and 335 nm. Liquid chromatographic (LC) analysis of th AFB1-lysine adduct showed a relative retention time of 2.1 min. Using the same epoxidation procedure, BSA-AFB1 adduct and ovalbumin-AFB1 adduct were synthesized for production of antibodies and as coating antigen, respectively. Control rat serum, spiked with AFB1-lysine adduct and subjected to LC analysis showed a retention time of 2.1 min, which is similar to that of AFB1-lysine reference standard, synthesized. Further, enzymatically hydrolyzed, control rat serum spiked with BSA-AFB1 adduct showed 2 peaks with retention times of 2.1 and 2.7 min. Based on the LC analysis, recovery of BSA-AFB1 in terms of AFB1-lysine adducts was 67 ± 5%. The major peak (2.1 min) accounted for 72% of the adduct; the second minor peak (2.7 min) accounted for 28% of the total AFB1-lysine adducts formed. Stability studies on the AFB1-lysine adduct synthesized, indicated that it was stable for 1 month. Antibody capture assay showed an absorbance of 0.9 to 1.0 at a dilution of 1:50 000 when ovalbumin-AFB1 was used as a coating antigen. Indirect competitive ELISA showed 50% displacement (IC50) of the antibodies at a concentration of 13 ng AFB1-lysine, whereas the IC50 for AFB1 was 7 ng. The recovery of AFB1-lysine adduct spiked to control rat serum followed by enzymatic hydrolysis and immunoanalysis (indirect ELISA) was 93 ± 6%. The enzyme immunoassay was validated by a rodent model, in which the animals were exposed to aflatoxin B1 (20 μg AFB1/kg body mass/day). The level of AFB1-lysine adduct in the rat serum was 27.3 ± 4.37 μg/mg albumin.
Simultaneous Determination of Six Triazolic Pesticide Residues in Apple and Pear Pulps by Liquid Chromatography with Ultraviolet Diode Array Detection
Authors: Bicchi Carlo , Cordero Chiara , Rubiolo Patrizia , Occelli Alessandro
Published: February 2020

A method is described for the simultaneous determination of diclobutrazol, flusilazole, flutriafol, hexaconazole, paclobutrazol, and tetraconazole in apple and pear pulps used in baby food at a limit of 0.01 mg/kg. Apple and pear pulp samples are subjected to selective solid-phase microdispersion (SPMD) with SPE-ED Matrix-38 and acetone–cyclohexane, and the extracts are cleaned up on a Florisil cartridge with hexane–cyclohexane–acetone. The extracts are then analyzed by liquid chromatography with ultraviolet detection, using an octadecylsilane column with a gradient-programmed acetonitrile–water mobile phase. Recoveries were determined by spiking apple and pear pulps with the 6 pesticides under investigation at 0.1, 0.05, 0.03, and 0.01 mg/kg. Six determinations were performed at each level for each pesticide. Recoveries were ≥70% at the 0.01 mg/kg level.
Multiresidue Determination of Organochlorine Pesticides and Polychlorinated Biphenyls in Milk by Gas Chromatography with Electron-Capture Detection after Extraction by Matrix Solid-Phase Dispersion
Authors: Yagüe Cristina , Bayarri Susana , Lázaro Regina , Conchello Pilar , Ariño Agustín , Herrera Antonio
Published: February 2020

A multiresidue analytical method based on matrix solid-phase dispersion was developed to analyze liquid milk for 22 organochlorine pesticides (OCPs) and 6 polychlorinated biphenyls (PCBs). Initial extraction is performed by loading 3 mL milk onto a 2.0 g octadecyl (C18)-bonded silica cartridge with n-hexane as the eluant. Neutral alumina column chromatography with sodium sulfate as the drying agent is used for further cleanup. The eluate is concentrated to 0.5 mL, and target analytes are determined by capillary gas chromatography with electron-capture detection. The optimized method was validated by determining accuracy (recovery percentages), precision (repeatability and reproducibility), and sensitivity (detection and quantitation limits) from analyses of milk samples fortified at 10 and 1 μg/L levels. Average recoveries were between 74 and 106% for all residues except β-HCH, β-endosulfan, and endosulfan sulfate. Both repeatability and reproducibility relative standard deviation values were < 22% for all residues. Detection limits ranged from 0.02 to 0.12 μg/L and quantitation limits were between 0.02 and 0.62 μg/L. The proposed analytical method may be used as a fast and simple procedure in routine determinations of OCPs and PCBs in milk.
Enzyme Immunoassay of Staphylococcal Enterotoxins in Dairy Products with Cleanup and Concentration by Immunoaffinity Column
Authors: Lapeyre Christiane , Maire Tiphaine , Messio Sabine , Dragacci Sylviane
Published: February 2020

Two different immunoaffinity columns (IACs) were prepared for detection of staphylococcal enterotoxins (SETs) from dairy products. First, a specific IAC for staphylococcal enterotoxin A (SEA), IAC-1, was prepared by coupling monoclonal antibody (mAb) directed against SEA; second, a polyspecific IAC for SEA, staphylococcal enterotoxin B (SEB), staphylococcal enterotoxin C (SECs), and staphylococcal enterotoxin D (SED), IAC-2, was prepared by coupling a mixture of mAbs against SEA, SECs, and SED, and rabbit IgG against SEB. These columns were applied for detection of SETs in dairy products, after extraction, immunoaffinity chromatography, and enzyme immunosorbent assay (EIA). Overall recoveries from dairy products spiked with 1 ng SEA/25 g averaged 81.2% (range, 76–85%) on IAC-1. The repeated use of IAC-1 was then determined with good efficiency of 91.5%, in more than 10 runs. On the other hand, a recovery yield of 77%of SETs (SEA, SEB, SEC, and SED) from dairy products spiked with 2.5 ng of each enterotoxin per 25 g, was obtained with IAC-2. IAC-2 was also successfully subjected to the chromatography of naturally contaminated foods implicated in staphylococcal food poisoning outbreaks. This new extraction–concentration–immunoaffinity–chromatography method (ECIC) is very useful for improving staphylococcal enterotoxin detection and eliminating matrix effect in EIA of dairy products.
Broad-Spectrum Determination of Pesticides in Groundwater by Gas Chromatography with Electron Capture Detection, Nitrogen–Phosphorus Detection, and Tandem Mass Spectrometry
Authors: Frenich Antonia Garrido , Espada Maria Del Carmen Pablos , Vidal Jose Luis Martínez , Molina Luis
Published: February 2020

Gas chromatography with electron capture detector (ECD), nitrogen–phosphorus detector (NPD), and tandem mass spectrometry (MS/MS) was used to identify 36 pesticides, widely used to control various pest and diseases in vegetables, in water after a preconcentration step on C18 cartridges. The recoveries obtained ranged from 70 to 135% at a fortification level of 100 ng/L with relative standard deviations of <36.2%. The limits of detection and quantitation were ≤48 and ≤160 ng/L, respectively. Important advantages of MS/MS over ECD and NPD in the determination of pesticides are also presented. The proposed analytical methodology was applied to the determination of pesticides in groundwater samples from an agricultural area, the Campo de Dalías (Almería, Spain). The most frequently encountered pesticides were endosulfan sulfate and metalaxyl, whereas the pesticide found at the highest concentration was fenamiphos.
Enzyme Assay for Identification of Pectin and Pectin Derivatives, Based on Recombinant Pectate Lyase
Authors: Hansen Karin M , Thuesen Annette B , Soderberg Jørgen R
Published: February 2020

A simple method was developed for fast identification of pectin, based on a recombinant endopectate lyase cloned from Aspergillus niger. When pectin was demethylated and treated with pectate lyase, β-elimination occurred, resulting in a double bond between C-4 and C-5 in the galacturonic acid residue of the released nonreducing end. The formation of double bonds produced an increase in light absorption, which was detected at 235 nm. The assay was tested on pectin of different origins (apple, orange, sugar beet, sunflower, celery, lemon), pectin derivatives (amidated pectin), and speciality types such as low molecular weight and low %DE (degree of esterification, percentage of galacturonic acid groups esterified with methanol) pectin. The highest response was given by pectate (pectin with %DE<5) and the lowest by pectin extracted from sugar beet. No other gums (carboxymethylcellulose, carrageenan, locust bean gum, tragacanth, gellan, tamarind, xanthan, amylogum, sodium alginate, or agar) gave any response. Members of IPPA (International Pectin Producers Association) have evaluated the validity of the assay in a ring test. All members of the Association were able to identify pectin from other gums in a blind test. The method can replace more laborious and ambiguous identification tests which exist today.
Determination of Total Metals in Cultivated Oysters (Crassostrea gigas) from the Northwest Coast of Mexico by Microwave Digestion and Atomic Absorption Spectrometry
Authors: García-Rico Leticia , Ruiz Rita E Ramos , Jiménez Javier Vivian
Published: February 2020

Bivalves such as oysters often accumulate heavy metals, and therefore can be used to monitor changes of pollutant concentrations in the environment. Cultivated oysters from the northwest coast of Mexico are widely used for human consumption and thus have an important commercial value. Information was gathered on the concentration of these elements in oysters (Crassostrea gigas) cultivated on the coast of Sonora. Oysters were randomly collected from April to October 1997, from 6 different locations (65 individuals per site) in 4 different months. Metals were determined by microwave digestion followed by atomic absorption spectroscopy. The mean values (μg/g fresh weight) for each metal were: Cd, 0.76; Cu, 3.64; Zn, 17.71; Pb, 0.50; As, 0.05; Hg, 0.03; and Se, 0.21. The results show that, except for Cd, concentrations of regulated metals were under the maximum permitted values specified by regulatory agencies of Mexico and were comparable to those reported from other areas.
Slurry Atomization of Wheat-Milled Fractions for Electrothermal Atomic Absorption Spectrometric Determination of Nickel and Chromium
Authors: González M Mar , Gallego Mercedes , Valcárcel Miguel , Gómez-Cárdenas Gaspar
Published: February 2020

A slurry electrothermal atomic absorption spectrometric technique was used to determine Ni and Cr in wheat flour and its by-products. Slurries (3%, w/v) were prepared in a mixture of 15% HNO3–10% H2O2 as suspended medium. Differences in Ni and Cr contents due to origin and texture of the wheat and to the effects of the milling process were studied. Ni and Cr levels were more markedly influenced by the geographical origin of the wheat than by its texture. Both metals were related to the amount of bran present in each milled fraction and varied over the ranges of 212–298 ng/g (Ni) and 34–85 ng/g (Cr) in flours (with minimal bran contents); 297–460 ng/g (Ni) and 67–118 ng/g (Cr) in shorts; and 424–723 ng/g (Ni) and 106–165 ng/g (Cr) in brans. The Ni and Cr contents were not significantly affected by the technological processes typically performed in a flour-producing factory.
Quantitation of Nicotine in Tobacco Products by Capillary Electrophoresis
Authors: Clarke Michelle Bruffey
Published: February 2020

A simple and rapid capillary electrophoresis (CE) method was developed for the quantitation of nicotine in commercial tobacco products. The method involves a 6 min run at 30 kV, using a 50mM phosphate buffer (pH 2.5), paraquat as internal standard, and UV detection at 260 nm. Nicotine was extracted from tobacco products in <15 min. Recoveries from spiked extracts were >95%, and the extraction efficiencies of water, 1M HCl, 1M acetic acid, 5mM phosphate buffer (pH 2.5), and 1% triethanol amine were similar. Nicotine concentrations in 67 samples of cigarettes, cigars, and bidis varied between 0.37 and 2.96% (w/w). An established gas chromatography/mass spectrometry method using toluene extraction consistently yielded lower nicotine values than the CE method. Experimental evidence suggests that this is due to insufficient extraction of nicotine by toluene.
Optimization and Validation of Arsenic Determination in Foods by Hydride Generation Flame Atomic Absorption Spectrometry
Authors: Kabengera Charles , Bodart Patricia , Hubert Philippe , Thunus Leopold , Noirfalise Alfred
Published: February 2020

A hydride generation flame atomic absorption spectrometric method was developed and optimized to quantitate arsenic (As) in foods. A wet digestion of the samples with HNO3 + H2O2 was performed and excess oxidants were eliminated by addition of hydrochloric acid and urea. As5+ in As3+ was then reduced by potassium iodide. The As3+ solution was analyzed by generation of arsine with sodium tetrahydroborate. As determination ranged from 2.5 to 20 μg/L, with a determination coefficient of 0.997. The limits of detection (LOD) and quantitation (LOQ) were 0.6 and 2.1 μg/L, respectively. The method was validated and good results were obtained for recovery, precision, accuracy, LOD, and LOQ. This method is now used to analyze foods from Rwanda.
Rapid Food Decomposition by H2O2–H2SO4 for Determination of Total Mercury by Flow Injection Cold Vapor Atomic Absorption Spectrometry
Authors: Zenebon Odair , Sakuma Alice M , Dovidauskas Sergio , Okada Isaura A , Maio Franca D De , Lichtig Jaim
Published: February 2020

A mixture of 50% H2O2–H2SO4 (3 + 1, v/v) was used for decomposition of food in open vessels at 80°C. The treatment allowed rapid total mercury determination by flow injection cold vapor atomic absorption spectrometry. Cabbage, potatoes, peanuts paste, hazelnuts paste, oats, tomatoes and their derivatives, oysters, shrimps, prawns, shellfish, marine algae, and many kinds of fish were analyzed by the proposed methodology with a limit of quantitation of 0.86 ± 0.08 μg/L mercury in the final solution. Reference materials tested also gave excellent recovery.
Liquid Chromatographic Determination of Amphotericin B in Different Pharmaceuticals
Authors: Lue Louis P , Hadman Susan T , Vancura Ales
Published: February 2020

Amphotericin B (AmB) is one of the most potent antifungal agents and the drug of choice in the treatment of serious fungal infections. A liquid chromatographic (LC) method was developed to determine AmB in pharmaceutical formulations for injection, tissue culture, cream, and lotion. μBondapak C18 reversed-phase column and a simple mobile phase consisting of acetonitrile–water–acetic acid (40 + 54 + 6, v/v) was used. The flow rate was 1.8 mL/min and the effluent was monitored at 405 nm. The developed LC method uses piroxicam as an internal standard and has a limit of detection of 10 ng/mL, a limit of quantitation of 30 ng/mL, and the assay is linear from 0.01 to 100 μg/mL. AmB and piroxicam elute with retention times of 12.4 and 4.0 min, respectively, and the resolution between AmB and piroxicam was 10.6. In comparison with the official United States Pharmacopeia microbial assay for AmB, this LC method is more rapid, selective, sensitive, and offers positive identification.