bluuebunny/crossref_metadata_2025 huggingface dataset:
Development of the Infrared Hollow Waveguide Sampler for the Detection of Chlorophenols in Aqueous Solutions
Authors: Yang Jyisy , Lee Chung-Jay
Published: February 2020

A method based on the infrared hollow waveguide sampler was developed for sensing chlorophenols in aqueous solutions. This sampler was constructed by coating a suitable hydrophobic film onto the inner surface of an infrared hollow waveguide. By passing the aqueous solution through the hollow waveguide sampler, analytes can be absorbed into the hydrophobic layer. The adsorbed analytes can be sensed later by using Fourier transform infrared spectrometry. Six hydrophobic polymers were investigated for their performance in conjunction with the infrared hollow waveguide sampler for the detection of chlorophenols. Results indicated that poly(acrylonitrile-co-butadiene) was a most suitable hydrophobic material for absorption of chlorophenols in aqueous solutions. To further increase the detection sensitivity, factors such as sampling flow rate, sampling time, and thickness of the hydrophobic film were also investigated. Results indicated that the infrared signals were similar in the examined flow rates (2–30 mL/min), but that a higher flow rate tended to produce a higher analytical signal. Fast detection speed was an advantage of this method for the detection of chlorophenols, and the sampling/detection time can be <10 min. In addition, analytical signals were nearly proportional to the thickness of the hydrophobic film coating the inside of the hollow waveguide. With the optimal conditions found in this work, detection limits based on 3 times the peak-to-peak noise level were around 300 ppb for the chlorophenols examined. A high degree of linearity in the standard curves was also observed for this method in the concentration range of 10–100 ppm. The typical regression coefficients were >0.994 for the chlorophenols examined.
Gas Chromatographic/Mass Spectrometric Determination of Benzene and Its Alkyl Derivatives in Indoor and Outdoor Air in Fuji, Japan
Authors: Amagai Takashi , Ohura Takeshi , Sugiyama Tomohiko , Fusaya Masahiro , Matsushita Hidetsuru
Published: February 2020

An analytical method was established for the determination of benzene and 13 of its alkyl derivatives. The method was applied to a survey of indoor pollution that investigated the usefulness of the method, concentration levels, seasonal variations, profiles, correlations between compounds, and factors that affected indoor pollution by these compounds. The survey was performed in 21 houses in the summer of 1999 and 20 houses in the winter of 1999–2000 in Fuji, Japan. All the target compounds were detected in the indoor and outdoor air of all houses. Outdoor concentrations of benzene ranged from 0.779 to 3.17 μg/m3 in summer and from 1.35 to 6.04 μg/m3 in winter, whereas indoor concentrations of benzene ranged from 0.694 to 3.11 μg/m3 in summer and from 1.65 to 6.89 μg/m3 in winter. Indoor concentrations of the target compounds, except for benzene, were elevated, compared with outdoor concentrations. Because indoor and outdoor concentrations of benzene and its derivatives in summer were lower than in winter, the emission of these compounds may be increased by use of a heater and other variables present in winter. Profiles of the compounds, correlations between the compounds, and factors that affected indoor pollution (determined by multiple regression analysis) were investigated. These results suggested that indoor benzene predominantly penetrated from outdoors and that other benzene derivatives were emitted from indoor sources, such as paint solvents and kerosene heaters.
Evaluation of Platanus occidentalis and Pinus sylvestris as Bioindicators for Lead and Cadmium by Slurry Sampling-Electrothermal Atomic Absorption Spectrometry
Authors: Amoedo Luisa , Capelo J Luis , Lavilla Isela , Bendicho Carlos
Published: February 2020

Two higher plants (Platanus occidentalis and Pinus sylvestris) were used as bioindicators for assessment of contamination by Pb and Cd in an urban and industrialized area. Both toxic metals in plant tissue were determined by transverse-heated electrothermal atomic absorption spectrometry-longitudinal Zeeman background correction combined with automated ultrasonic slurry sampling. Twenty sampling points were established to observe a relationship between metal concentration in plant and traffic density. Screening optimization of variables influencing slurry preparations (sonication time, sonication power, and surfactant concentration) followed a fractional factorial design at 2 levels. No significant effects were observed in the interval of variables studied. Limits of detection of Pb and Cd in the plants were 0.28 and 0.025 μ/g (dry weight), respectively. Metal concentrations in the plants were in the range of 5–51 and 0.05–0.7 μg/g for Pb and Cd, respectively. Factor analysis to data of metal concentration in both plants, extractable metal content in soil, distance to traffic, and traffic density, showed a significant association between features such as concentration of Pb and Cd in leaves of P. occidentalis and traffic density, which accounted for the largest variance. Other features such as extractable metal contents in soil accounted for lesser variance, meaning that soils in the area investigated were less suitable than plants for monitoring metal pollution caused by vehicular traffic.
Determination of Mercury in Sewage Sludges by Slurry Sampling Electrothermal Atomic Absorption Spectrometry
Authors: López-García Ignacio , Sánchez-Merlos Mateo , Arroyo-Cortez Jesús , Hernández-Córdoba Manuel
Published: February 2020

An electrothermal atomic absorption spectrometric procedure was developed for the determination of mercury in sewage sludge, in which the samples were suspended in a solution containing hydrofluoric and nitric acids. Silver nitrate (4%, m/v) and potassium permanganate (3%, m/v) were incorporated as matrix modifiers, and aliquots were directly introduced into the graphite furnace. A fast-heating program with no conventional pyrolysis step was used. The detection limit for mercury in a 50 mg/mL suspension was 0.1 μg/g. Calibration was performed by using aqueous standards. An analysis of certified reference materials confirmed the reliability of the procedure.
Size Exclusion Chromatographic Cleanup for GC/MS Determination of Organophosphorus Pesticide Residues in Household and Vehicle Dust
Authors: Moate Thomas F , Furia Matthew , Curl Cynthia , Muniz Juan F , Yu Jianbo , Fenske Richard A
Published: February 2020

Size exclusion chromatography (SEC) was used as a cleanup method for the analysis of organophosphorus pesticides in household and vehicle dusts. The pesticides investigated were diazinon, methyl parathion, chlorpyrifos, malathion, phosmet, and azinphosmethyl. These compounds are of interest due to their use in agricultural tree fruit production and/or urban pest control. Pesticides were determined via gas chromatography/mass spectrometry with selected-ion monitoring and cool on-column injection. The lower limit of method validation was 0.20 μg/g. Method limits of detection in dust ranged from 0.012–0.055 μg/g. Dust samples were collected with vacuums from the homes and vehicles of people living and working in a rural agricultural region in the central part of Washington State. The analytes were extracted from the dust by sonication in acetone. The extracts were solvent-exchanged to cyclohexane, frozen, thawed, and centrifuged prior to SEC injection. Following SEC, the eluent was split into 2 fractions, concentrated, and injected on-column into the gas chromatograph. This method represents the first complete publication describing the SEC cleanup of organophosphorus pesticides in dusts. Recoveries of pesticides in dusts ranged from 63.5–110.8 ± 4.9–19.6% over a fortification range of 0.20–10.00 μg/g. This optimized, automated, and reproducible SEC method does not require further treatment or cleanup for trace determination of these organophosphorus pesticides.
Automatic Flow System Titration Based on Multicommutation for Spectrophotometric Determination of Total Acidity in Silage Extracts
Authors: Tumang Cristiane A , Paim Ana Paula S , Reis Boaventura F
Published: February 2020

A multicommutated flow titration procedure is proposed for the spectrophotometric determination of total acidity in silage extracts. The flow network comprises a set of 3-way solenoid valves, computer-controlled to provide facilities to handle the titrand, titrant, and carrier solutions by using a single pumping channel. The procedure is based on the volumetric fraction variation approach that maintains the same volume of titrand solution and varies the titrant solution step by step, to provide determination without the use of an analytical curve. The procedure is implemented by using phenolphthalein as an external indicator; the proposed algorithm was able to titrate silage extracts presenting different color intensities. Sample solutions with concentrations ranging from 10−3 to 10−1 mol/L total acidity could be analyzed by using 10−2 mol/L sodium hydroxide as the titrant solution. Other advantages include a relative standard deviation of <1.0% (n = 4) for a typical silage extract solution containing 26 mmol/L total acidity; an analytical throughput of 16 determinations per hour was also achieved. Accuracy was assessed by processing a set of silage extract solutions and comparing the results with those obtained by using the conventional potentiometric titration procedure. No significant difference at the 95% confidence level was observed.
Virulence Testing of Listeria monocytogenes
Authors: Raybourne Richard B
Published: February 2020

A major problem in understanding foodborne listeriosis from both the basic science and regulatory perspectives revolves around the role played by virulence factors of Listeria monocytogenes and how these interact with host susceptibility to result in the observed incidence of disease. From a mechanistic perspective, this problem has been well investigated, and many virulence components of L. monocytogenes have been discovered. Deletion of these genes results in large reductions in virulence functions in vitro and in vivo. The clonal bacteria and genetically identical hosts necessary to solve the riddles associated with virulence mechanisms are not likely to reflect the natural diversity found among wild populations of L. monocytogenes, including those associated with food. These factors contribute to a major dilemma in risk assessment and risk management of foodborne listeriosis: Although low-level L. monocytogenes contamination of certain foods is relatively common, suggesting widespread exposure, illness is overwhelmingly associated with only a relatively small subpopulation (3 of the 13 L. monocytogenes serotypes) and occurs in only a small proportion of susceptible individuals. Virulence testing based on DNA probes for virulence genes is confounded by the widespread distribution of these genes in food isolates. In terms of the distribution of virulence factors among food isolates of L. monocytogenes, only listeriolysin is well characterized, because β-hemolysis is often used to confirm the presence of L. monocytogenes in foods. The presence of other virulence genes such as those involved in host cell invasion and cell-to-cell spread (inIA and actA) among food isolates has not been extensively investigated. How the presence of these components translates into functional virulence as measured in vivo and in vitro is also unknown. Animal studies and cell culture systems show a range of virulence among food isolates of L. monocytogenes. However, clinical isolates included in such studies are not consistently more virulent than food isolates with no known human disease association. Where multiple serotypes or ribotypes are compared, it has been difficult to demonstrate a consistent pattern of increased virulence associated with any subtype(s) in animal or in vitro studies. Development of model systems that adequately reflect the complexity of the host–pathogen relationship remains a challenge.
Simultaneous Determination of Promethazine, Chlorpromazine, and Perphenazine by Multivariate Calibration Methods and Derivative Spectrophotometry
Authors: Shamsipur Mojtaba , Hemmateenejad Bahram , Akhond Morteza
Published: February 2020

Partial least-squares (PLS) regression, singular value decomposition-based PLS, and an artificial neural network (ANN) were tested as calibration procedures for the simultaneous determination of promethazine, chlorpromazine, and perphenazine by both conventional and derivative spectrophotometry. Comparison of the results revealed that the application of the ANN to the derivative spectra is superior to the application of the 2 PLS methods used. Different binary and ternary synthetic mixtures of the phenothiazine drugs in pure form and in tablets were analyzed by the proposed method, and acceptable results were obtained.
Validation of a Gas Chromatographic Method for Determination of Fatty Alcohols in 10 mg Film-Coated Tablets of Policosanol
Authors: Sierra Roxana , González Víctor L , Magraner Juan
Published: February 2020

A gas chromatographic method using a packed column and 1-eicosanol as an internal standard was validated for the determination of the fatty alcohols that compose policosanol in 10 mg film-coated tablets. The alcohols were determined as trimethylsilyl derivatives, prepared with N-methyl-N-trimethylsilyltrifluoroacetamide. The method can detect degradation products with high retention times, without interfering with the peaks of the active principle. Good linearity (correlation coefficient = 0.9992) and accuracy (mean recovery = 100.27 ± 1.66%) were proven over a range of 25–200% of the nominal concentration. Within- and between-day precision at the nominal 100% value met the acceptance criteria (<2%). Ruggedness was examined through an intralaboratory experimental study in which 6 operational changes were made; the changes were found to have no effect on quantitation, repeatability, resolution, and relative retention time. The method is suitable for the quality control process and stability studies of these tablets.
Monitoring of Five Postharvest Fungicides in Fruit and Vegetables by Matrix Solid-Phase Dispersion and Liquid Chromatography/Mass Spectrometry
Authors: Blasco Cristina , Picó Yolanda , Font Guillermina
Published: February 2020

A method was developed for monitoring dichloran, flutriafol, o-phenylphenol, prochloraz, and tolclofos-methyl in fruits and vegetables, using matrix solid-phase dispersion and liquid chromatography with mass spectrometry detection. The method was used to determine fungicide content in 200 samples of chards, onions, peppers, bananas, lemons, and oranges. Of the samples examined, 54% contained o-phenylphenol with concentrations ranging from 0.005 to 3.34 mg/kg and 35% showed prochloraz in the range of 0.06–1.95 mg/kg. Dichloran, flutriafol, and tolclofos-methyl were detected only occasionally. Only 4% of the samples exceeded the European Union maximum residue limits. The pesticides involved were tolclofos-methyl in 3 samples, o-phenylphenol and flutriafol in 2, and dichloran in one. The calculation of estimated daily intake from these monitoring data showed that dietary intakes were much lower than the acceptable daily intakes established by international agencies.
Differential Pulse Polarographic Determination of Procymidone in Formulations and Wine
Authors: Sreedhar Neelam Y , Babu Thommandru R , Samatha Kethamreddy , Sujatha Devarapalli , Thriveni Thenepalli
Published: February 2020

The dicarboximide fungicide procymidone was studied systematically by using direct current polarography, cyclic voltammetry, differential pulse polarography (DPP), controlled potential electrolysis, and millicoulometry in the universal buffer medium with dimethylformamide as the solvent. Procymidone exhibited a single well-defined polarographic wave in the pH range 2.0–6.0, leading to the formation of the hydroxy compound. The overall reduction process was diffusion-controlled and adsorption-free. The variation of half-wave potential with pH, the concentration of the analyte, and other experimental conditions are described. The reduction mechanism proposed is an overall 4-electron process, in which the dicarboximide group is reduced. DPP was used to determine procymidone in agricultural formulations and wine at the optimum conditions found; a detection limit of 2.4 × 10−9M was estimated. The results obtained by the proposed method were also compared with those obtained by other methods.
Spectrophotometric Determination of Caramel Content in Spirits Aged in Oak Casks
Authors: Boscolo Mauricio , Andrade-Sobrinho Luiz G , Lima-Neto Benedito S , Franco Douglas W , Ferreira Marcia Miguel Castro
Published: February 2020

A new methodology was developed for determination of caramel in spirits aged in oak casks. The method is based on differences between the electronic spectra of oak aqueous alcoholic extracts and caramel solutions in the same solvent. The data were treated by 2 different approaches: the simplest one was based on the plot of caramel concentration versus the ratio of absorbance at 210 and 282 nm; the other was based on a partial least squares (PLS) calibration model using the first derivative of the spectral data. Both methodologies were applied to analysis of 159 aged spirit samples. The mean caramel content of several Brazilian sugar cane spirits (cachaça) and all United States whiskies was smaller than that of Scottish whiskies and other brandies from several countries. Correlation was good between caramel concentrations for the same sample calculated by the 2 methods. The uncertainties following PLS and the absorbance ratio method were 0.01 and 0.03 g/L, respectively, for a sample containing 0.45 g/L caramel. Treatment of UV-VIS spectra by pattern recognition using hierarchical clustering analysis and principal components analysis allowed discrimination of the samples as a function of their caramel content. It was possible to distinguish U.S. whiskies from other whiskies, but a clear differentiation among Brazilian cachaças as a function of their geographic origin was not feasible. Small caramel quantities as low as 0.08 g/L were clearly detected by these methodologies.
Spectrophotometric Determination of Phenylephrine Hydrochloride in Pharmaceuticals by Flow Injection Analysis Exploiting the Reaction with Potassium Ferricyanide and 4-Aminoantipyrine
Authors: Rocha José R C , Galhardo Cristiane X , Natividade Maria Auxiliadora E , Masini Jorge C
Published: February 2020

This paper presents a method for the determination of phenylephrine hydrochloride in pharmaceuticals by spectrophotometric flow injection analysis exploiting the reaction with potassium ferricyanide and 4-aminoantipyrine, which leads to the formation of a condensation product with strong absorptivity at 500 nm. The linear dynamic range was between 0.95 and 9 mg/L, with a limit of detection of 0.2 mg/L and a sampling throughput of 120 samples per hour. The method was applied to eyewashes and nasal decongestant liquid medicines.
DNA Microarray Technology Used for Studying Foodborne Pathogens and Microbial Habitats: Minireview
Authors: Al-Khaldi Sufian F , Martin Scott A , Rasooly Avraham , Evans Jeff D
Published: February 2020

Microarray analysis is an emerging technology that has the potential to become a leading trend in bacterial identification in food and feed improvement. The technology uses fluorescent-labeled probes amplified from bacterial samples that are then hybridized to thousands of DNA sequences immobilized on chemically modified glass slides. The whole gene or open reading frame(s) is represented by a polymerase chain reaction fragment of double-strand DNA, approximately 1000 base pair (bp) or 20–70 bp single-strand oligonucleotides. The technology can be used to identify bacteria and to study gene expression in complex microbial populations, such as those found in food and gastrointestinal tracts. Data generated by microarray analysis can be potentially used to improve the safety of our food supply as well as ensure the efficiency of animal feed conversion to human food, e.g., in meat and milk production by ruminants. This minireview addresses the use of microarray technology in bacterial identification and gene expression in different microbial systems and in habitats containing mixed populations of bacteria.
Comparison of Visual Immunoassay and Chromogenic Culture Medium for the Presence of Listeria spp. in Foods
Authors: Istafanos Philip , James Lawrence
Published: February 2020

Two rapid screening methods [the TECRA™ Listeria Visual Immunoassay (LIS–VIS) kit, an AOAC-approved 48 h visual test, which detects Listeria through colorimetry, and BCM™ Listeria isolation and differentiation plating agar] were used to screen U.S. Food and Drug Administration-regulated commodities for the presence of Listeria spp. Seventy-four different food samples were screened for the presence of Listeria spp. by using both protocols. Test results for the TECRA LIS–VIA showed 66 negative samples and 1 false positive, with 4 confirmed as L. monocytogenes and 3 as L. innocua. With the BCM agar, 67 samples were negative, 4 were confirmed as L. monocytogenes, and 3 were confirmed as L. innocua. Both methods showed similar results and were effective screening tools for Listeria spp. in foods. The BCM agar method proved to be a rapid, sensitive, and excellent tool for early screening and differentiation of Listeria spp. present in foods.
Improved Thin-Layer Chromatographic Method for the Separation of Cholesterol, Egg Phosphatidylcholine, and Their Degradation Products
Authors: Gabriëls Margriet , Camu Frederik , Plaizier-Vercammen Jacqueline
Published: February 2020

Degradation products of egg phosphatidylcholine (EPC) and cholesterol were analyzed with different normal- and reversed-phase thin-layer chromatography (TLC) systems. The best separation, in terms of the highest number of degradation products from both analytes, was obtained with a reversed-phase system, using butanol–methanol–water–96–98% (v/v) acetic acid (40 + 40 + 20 + 4, v/v/v/v) as the mobile phase after overnight saturation at 25°C. A special development technique was used. After a first development, the plate was dried and a second development was performed in the same direction. This method enabled us to separate lysophosphatidylcholine, several free fatty acids and hydroperoxides, and several undefined degradation products of EPC and cholesterol. All products were visualized after the plate was dipped in a 1% (v/v) solution of 4-methoxybenzaldehyde in 98% sulfuric acid–96–98% (v/v) acetic acid–ethanol– water (2 + 10 + 60 + 30), presenting a blue color or a white spot against a colored background. After activation at 110°C, a stable color for both analytes was reached after 12 min. Precision of <5% was obtained at 2 levels of analysis. Good linearity was obtained in the range of 5–30 μg for EPC (r = 0.991) and 5–40 μg for cholesterol (r = 0.991). These results show that TLC can be an inexpensive and easy alternative for the analysis of EPC and cholesterol.
Immunoaffinity Column as Sample Cleanup Method for Determination of the Beta-Adrenergic Agonist Ractopamine and Its Metabolites
Authors: Shelver Weilin L , Smith David J
Published: February 2020

A monoclonal antibody-based immunoaffinity column (RAC-IAC) was developed as a cleanup method for the determination of ractopamine and ractopamine glucuronides. [14C]Ractopamine (5 μg) and [14C]ractopamine glucuronides (5 μg) were fortified into 10 mL cattle urine, and loaded onto an RAC-IAC (5 mg IgG/mL) column. The column was washed and the bound analytes were eluted. In the initial loading and washing, 22% of the radioactivity was washed off and the subsequent elution step recovered 78%. A blank column prepared from nonspecific IgG retained <10% of the radioactivity. The RAC-IACs were damaged by high methanol concentrations, preventing reuse. Elution of the analytes with 50mM glycine buffer, pH 2.8, prevented damage, and the columns could be reused at least 20 times with no change in performance. They were stored >3 months in phosphate- buffered saline with 0.02% sodium azide at 4°C. The method was used with fortified cattle muscle, liver, and kidney samples with recoveries of 82.1 ± 7.6, 87.8 ± 1.9, and 92.5 ± 0.4%, respectively (n = 3). Similar studies with sheep muscle, liver, and kidney samples gave recoveries of 91.8 ± 0.2, 91.7 ± 0.3, and 92.3 ± 0.3, respectively ( n = 3). Liver and kidney samples were diluted to prevent column plugging, but all of the eluants were suitable for liquid chromatography analysis. This IAC is a selective, efficient, and economical cleanup method in a variety of matrixes for ractopamine determination.
Interlaboratory Comparison of Pesticide Recovery from Water Using Solid-Phase Extraction Disks and Gas Chromatography
Authors: Mersie Wondi , Clegg Chris , Wauchope R Don , Dumas Jose A , Leidy Ross B , Riley Melissa B , Young Roddy W , Mattice John D , Mueller Thomas C , Senseman Scott A
Published: February 2020

An interlaboratory study was conducted to assess the suitability of C18 solid-phase extraction disks to retain and ship different pesticides from water samples. Surface and deionized water samples were fortified with various pesticides and extracted using C18 disks. Pesticides were eluted from disks and analyzed in-house, or disks were sent to another laboratory where they were eluted and analyzed. Along with the disks, a standard pesticide solution in methanol was also shipped to be used for fortification, extraction, and analysis. The highest recovery from deionized or surface water using shipped disks was obtained for cyanazine (>97%), followed by metalaxyl (>96%), and atrazine (>92%). Although <40% of the bifenthrin, chlorpyrifos, and chlorothalonil fortified in surface water was recovered from shipped disks, recoveries from deionized water were >70%. From in-house eluted disks, bifenthrin and chlorpyrifos were recovered at 118 and 105%, whereas chlorothalonil showed 71% recovery, indicating that poor recovery from surface water was due to loss during shipping rather than low retention by the C18 disks. There was no consistent relationship between recovery from C18 disk and physicochemical properties for the pesticides included in this study. For most of the 13 pesticides tested, there were no differences in recovery between in-house extracted disks and shipped disks, indicating the suitability of disks to concentrate and transport pesticides extracted from water samples.
Determination of St. John's Wort Components in Dietary Supplements and Functional Foods by Liquid Chromatography
Authors: Ang Catharina Y W , Cui Yanyan , Chang Hebron C , Luo Wenhong , Heinze Thomas M , Lin Lawrence J , Mattia Antonia
Published: February 2020

St. John's wort ( Hypericum perforatum L.) preparations, a top-selling botanical dietary supplement used primarily as an antidepressant, has recently been used as an ingredient in some food products sold as functional foods. A rapid extraction technique followed by a liquid chromatographic (LC) method was developed to determine 4 characteristic bioactive compounds (pseudohypericin, hypericin, hyperforin, and adhyperforin) from St. John's wort in dietary supplements and functional foods to which it was added. Solid samples, including including dried leaf/flower mixture, dietary supplement capsules, tea bags, puff and snack bar, were extracted with methanol by sonication.Noncarbonated, fruit-flavored drinks were centrifuged and mixed with methanol. Compounds were then determined by isocratic, reversed-phase LC with UV detection at 2 wavelengths and further identified or confirmed by photodiode array spectra and LC/mass spectrometry. Within-laboratory method variations (% RSD) were satisfactory. Very low amounts, if any, of the 4 components were found in drink and puff samples, and none was found in the snack bar. The methods developed provide a useful means for the determination of St. John's wort components in dietary supplements and functional foods.
Stability of Sulfonamides, Nitrofurans, and Chloramphenicol Residues in Preserved Raw Milk Samples Measured by Liquid Chromatography
Authors: Noa Mario , Perez Norma , Gutierrez Rey , Escobar Irma , Diaz Gilberto , Vega Salvador , Prado Guadalupe , Urban Georgina
Published: February 2020

A stability study was made of 10 antimicrobials: 6 sulfonamides, 3 nitrofurans, and chloramphenicol residues in raw milk samples preserved with 0.1% potassium dichromate (K2Cr2O7) and 0.05% mercuric bichloride (HgCl2) during cold storage for 7 days. Preserved milk samples fortified with 50 ppb of each antimicrobial were analyzed by liquid chromatography (modified AOAC Method 993.32). Drugs were extracted with chloroform–acetone after solvent evaporation residues were dissolved with aqueous sodium acetate buffer solution (0.02M, pH 4.8), and fat was removed with hexane. Sulfonamides and chloramphenicol were detected at 275 nm (UV) by using a gradient system of sodium acetate buffer solution–acetonitrile starting at 95 + 5 (v/v) and finishing at 80 + 20 (v/v). Nitrofurans were detected at 375 nm (UV) isocratically with sodium acetate buffer solution–acetonitrile (80 + 20, v/v). Residues stability was measured through recovery data. Sulfamethoxazole, sulfachloropyridazine, nitrofurazone, furazolidone, and furaltadone residues remained stable in the presence of either preservative for 7 days. Sulfamethazine and chloramphenicol were not affected by K2Cr2O7, but had significant losses ( p <0.05) when HgCl2 was used: 26.2 and 13.4%, respectively. Average recoveries of sulfamonomethoxine, sulfamerazine, and sulfathiazole significantly decreased by Day 7, with losses of 17.1, 17.2, and 23.2% for K2Cr2O7, and 23.3, 20.7, and 48.0% for HgCl2, respectively. During 5 days of cold storage all antimicrobials tested, except sulfathiazole, remained stable in milk samples preserved with 0.1% K2Cr2O7 or 0.05% HgCl2.
Determination of Active Ingredient in Synthetic Pyrethroid Formulations by High-Performance Thin-Layer Chromatography/Densitometry
Authors: Sharma Krishan K
Published: February 2020

A new, simple, precise, and rapid high-performance thin-layer chromatography (HPTLC) method was developed for the analysis of commercial emulsifiable concentrate (EC) formulations of cypermethrin, α-cypermethrin, and λ-cyhalothrin. A known amount of reference grade synthetic pyrethroid and its EC formulation was subjected to TLC, and the amount of pesticide present in the active ingredient spot was estimated by densitometry in a single beam, single wavelength reflectance mode. Calibration curves of the synthetic pyrethroid was linear in the range of 8–24 μg, and the correlation coefficient for the calibration equation ranged between 0.97 and 0.99. Recoveries from laboratory-prepared test samples of the EC formulation were in the range of 95–99%. Pesticide formulations were further analyzed by gas liquid chromatography using flame ionization detector, and results were comparable. The proposed HPTLC method has application for quality control and determination of the shelf life of EC formulations.
Rapid Determination of 2,3,7,8-Tetrachlorodibenzo-p-Dioxin in Water Samples by Using Solid-Phase Microextraction Followed by Gas Chromatography with Tandem Mass Spectrometry
Authors: Landín Pedro , Llompart María , Lourido Mercedes , García-Jares Carmen , Carro Nieves , Cela Rafael
Published: February 2020

A rapid and simple method of using solid-phase microextraction was developed for determination of 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD) in water samples. In this method, the target analyte is extracted from the sample into the polymeric coating of the fused-silica fiber. After exposure, the fiber is thermally desorbed in the heated injection port of the gas chromatograph, and a chromatographic analysis is performed by using low-resolution tandem mass spectrometry. Parameters that may affect the extension of the microextraction process, such as sampling mode, sample volume, temperature, agitation, and sampling time, were studied. Extraction efficiencies for 3 coating fibers were investigated: 100 μm poly(dimethylsiloxane) (PDMS), 65 μm PDMS-divinylbenzene, and 75 μm carboxen-PDMS. Linearity was evaluated (R = 0.999) for a 250-fold concentration range from the fg/mL to the pg/mL level. The 2,3,7,8-TCDD was detected at the fg/mL level when the headspace over the water sample was sampled for 60 min; the limit of detection obtained was better than that of Method 8280B of the U.S. Environmental Protection Agency. The proposed method performed well when applied to the analysis of tap water, lake water, and seawater samples.
Determination of Deoxynivalenol and Nivalenol in Corn and Wheat by Liquid Chromatography with Electrospray Mass Spectrometry
Authors: Plattner Ronald D , Maragos Chris M
Published: February 2020

The fungus Fusarium graminearum is a pathogen of both wheat and corn. Strains of the fungus from the United States produce a toxin, deoxynivalenol (DON); strains of the fungus from Asia and Europe produce DON or a related toxin, nivalenol. These toxins can cause disease in livestock, and their potential presence in feed and foods is a concern for animal and human health. A method was developed to detect both toxins in corn and wheat by liquid chromatography/mass spectrometry of an extract of ground grain. The method requires no sample cleanup and can detect the toxins at 0.05 μg/g.
Analytical Pervaporation: A Key Technique in the Enological Laboratory
Authors: Luque de Castro Maria D , Luque-García Jose L , Mataix Eva
Published: February 2020

This paper reviews the use of analytical pervaporation (defined as the integration of 2 different analytical separation principles, evaporation and gas diffusion, in a single micromodule) coupled to flow-injection manifolds for the determination of analytes of interest in enology; the review discusses the advantages that these techniques can provide in wine analytical laboratories. Special attention is given to methods that enable the determination of either of 2 volatile analytes, or of one volatile analyte and one nonvolatile analyte by taking advantage of the versatility of the designed approaches. In a comparison of these methods with the official and/or standard methods, the results showed good agreement. In addition, the new methods offer improvements in linear determination range, quantitation limit, precision, rapidity, and potential for full automation. Thus, this review demonstrates that although the old technologies used in wine analytical laboratories may be supported by official and standard methods, they should be replaced by properly validated, new, and automated technologies.
Determination of Nitroimidazoles and Their Metabolites in Swine Tissues by Liquid Chromatography
Authors: Shen Jianzhong , Yhang Yue , Zhang Suxia , Ding Shuangyang , Xiang Xinhua
Published: February 2020

A liquid chromatographic method was developed for determination of metronidazole (MNZ), ronidazole (RNZ), dimetridazole (DMZ), and 2-hydroxymethyl-1-methyl-5-nitroimidazole (DMZOH) in swine tissue. After extraction with ethyl acetate and evaporation, the nitroimidazoles were redissolved in hydrochloric acid. Hexane was used in the liquid–liquid extraction to remove fat. An Oasis® HLB solid-phase extraction was performed after neutralization of the acidic extract. The limits of detection were 1.0–2.0 μg/kg for DMZOH, MNZ, RNZ, and DMZ in muscle and liver. Average recoveries ranged from 80.1 to 83.9% in muscle fortified at 10, 20, and 50 μg/kg; average re-coveries in liver ranged from 78.9 to 82.3%. The procedure provides a simple and sensitive method for monitoring DMZOH, MNZ, RNZ, and DMZ residues in swine tissues.
Simultaneous Determination of Residues of Chloramphenicol, Thiamphenicol, Florfenicol, and Florfenicol Amine in Farmed Aquatic Species by Liquid Chromatography/Mass Spectrometry
Authors: van de Riet Jeffery M , Potter Ross A , Christie-Fougere Melissa , Burns B Garth
Published: February 2020

A liquid chromatographic (LC)/mass spectrometric (MS) method was developed for determining the residues of chloramphenicol, thiamphenicol, florfenicol, and florfenicol amine in a number of aquatic species. The phenicols are extracted with acetone, the extracts are partitioned with dichloromethane, the aqueous layer is removed, and the organic layer is evaporated to dryness. The residue is dissolved in dilute acid and defatted with hexane, and the aqueous layer is prepared for analysis by LC. The phenicols are determined by reversed-phase LC by using a Hypersil C18-BD column with a water–acetonitrile gradient and MS detection using selectedion recording. Calibration curves were linear for all analytes between 0.015 and 0.425 ng injected. The relative standard deviations for measurements by the proposed method were <10% for all of the analytes studied, with re-coveries ranging from 71% for florfenicol amine to 107% for florfenicol in salmon tissue spiked at the 2 ng/g level. Detection limits of 0.1 ng/g for florfenicol and chloramphenicol, 0.3 ng/g for thiamphenicol, and 1.0 ng/g for florfenicol amine are easily obtainable. The operational errors, interferences, and recoveries for spiked samples compare favorably with those obtained by established LC methodology. The proposed method is simple, rapid, and specific for monitoring residues of chloramphenicol, thiamphenicol, florfenicol, and florfenicol amine in a number of aquatic species.
Detection of Paralytic Shellfish Poison by Rapid Cell Bioassay: Antagonism of Voltage-Gated Sodium Channel Active Toxins in vitro
Authors: Manger Ronald L , Leja Linda S , Lee Sue Y , Hungerford James M , Kirkpatrick Mary Ann , Yasumoto Takeshi , Wekell Marleen M
Published: February 2020

Although cytotoxicity assays provide several advantages over mouse bioassays, sodium channel-blocking marine toxins, such as those associated with paralytic shellfish poison (PSP), require prolonged incubation periods of 24–48 h. This is in marked contrast to in vitro detection of sodium channel-enhancing marine toxins such as ciguatoxins or brevetoxins which can be accomplished in as few as 4–6 h. We developed a modified PSP cell bioassay that is as rapid as in vitro methods for sodium channel-enhancing toxins. The cell bioassay is based on a saxitoxin-dependent antagonism of the rapid in vitro effects of brevetoxin or ciguatoxin. Comparative analysis of naturally incurred PSP residues by both antagonism cell bioassay and the mouse bioassay demonstrated significant correlation. The simplicity, sensitivity, and enhanced kinetics of the new antagonism cell bioassay format provide the basis for development of a practical alternative to conventional mouse testing for PSP.
Rapid Determination of Fosetyl-Aluminum Residues in Lettuce by Liquid Chromatography/Electrospray Tandem Mass Spectrometry
Authors: Hernández Félix , Sancho Juan V , Pozo Óscar J , Villaplana Carme , Ibáñez María , Grimalt Susana
Published: February 2020

This paper describes a new method for the sensitive and selective determination of fosetyl-aluminum (Al) residues in vegetable samples. The method involves extraction with water by using a high-speed blender and subsequent injection of the 5-fold diluted extract into the liquid chromatograph. Fosetyl-Al is determined by liquid chromatography with electrospray tandem mass spectrometry after the addition of tetrabutylammonium acetate as the ion-pairing re-agent. The method has been used to assay lettuce samples spiked at 2 and 0.2 mg/kg. Recoveries were satisfactory, with mean values of 98 and 106%, respectively, and relative standard deviations were <10%. The limit of quantitation was 0.2 mg/kg, and the limit of detection was as low as 0.05 mg/kg. Matrix-matched calibration was used for quantitation, and the addition of an internal standard improved repeatability. The developed method allows the accurate and rapid determination of low levels of fosetyl-Al residues in lettuce with very little sample handling and good sensitivity; it was shown to be robust by the analysis of almost 100 samples.
Improved Liquid Chromatographic Method for Determination of Organic Acids in Leaves, Pulp, Fruits, and Rinds of Garcinia
Authors: Jayaprakasha Guddadarangavvanahally K , Jena Bhabani S , Sakariah Kunnumpurath K
Published: February 2020

An improved liquid chromatographic (LC) method was developed for determination of organic acids in leaves, pulp, fruits, and rinds of Garcinia. At present, the commonly used LC method for analysis of organic acids in Garcinia extracts uses direct application of the extracts on the column. This practice gradually reduces efficiency of the column and shortens its life. In the improved method, the interfering substances such as pigments and xanthones were effectively removed by passing the aqueous extract through an ODS cartridge. With subsequent injection on a C18 reversed-phase column, using 6.0mM phosphoric acid as the mobile phase with a flow rate of 1.0 mL/min and UV detection at 210 nm, the organic acids were determined in the extracts. The major organic acid was (–)-hydroxycitric acid at the level of 2.5, 0.8, 3.0, and 20.1% in leaf, pulp, fresh fruit, and dried rinds, respectively. Minor quantities of hydroxycitric acid lactone, oxalic acid, and citric acid were also identified. Limits of detection and recoveries were 0.9–1.5 μg and 93.9–99.8%, respectively. This is the first report on the composition of organic acids from Garcinia pedunculata.
APLAC Interpretation and Guidance on the Estimation of Uncertainty of Measurement in Testing
Authors: Robertson Max , Chan Terence S S
Published: February 2020

The Asia Pacific Laboratory Accreditation Cooperation (APLAC) is the organization representing the community of bodies that accredit testing and calibration laboratories throughout the Asia Pacific region, including China and North America. APLAC members assess the competence of laboratories and grant them accreditation. They also provide mutual recognition of the equivalence of their accreditations, which facilitates international trade and acceptance by regulators. Harmonization of accreditation requirements is therefore vital to maintaining Mutual Recognition Arrangements. APLAC establishes management and technical criteria for accreditation and publishes guidance documents for accreditation bodies and laboratories.
Validation of Standardized High-Performance Thin-Layer Chromatographic Methods for Quality Control and Stability Testing of Herbals
Authors: Koll Kathrin , Reich Eike , Blatter Anne , Veit Markus
Published: February 2020

In herbal medicinal products the entire herbal drug or an herbal drug preparation is regarded as the active pharmaceutical ingredient, regardless of whether constituents with defined therapeutic activity are known. In quality control and stability testing of herbal medicinal products, fingerprint chromatograms are used as powerful tools to evaluate and compare the composition of compounds in such products. To fulfill the International Conference on Harmonization and Good Manufacturing Practice-based regulatory requirements in pharmaceutical quality control, chromatographic fingerprint analysis needs to be validated. Based on a standardized methodology, this paper provides a comprehensive concept for evaluating validation parameters for planar chromatographic fingerprinting by considering the stationary phase, sample application, developing solvent, chromatogram development, plate labeling, derivatization, documentation, and chromatographic equipment. Validation parameters addressed include stability of the analyte, selectivity, robustness testing, and method reproducibility.
A New Chelating Resin for Preconcentration and Determination of Mn(II), Ni(II), Cu(II), Zn(II), Cd(II), and Pb(II) by Flame Atomic Absorption Spectrometry
Authors: Maheswari Mohan A , Subramanian Mandakolathur S
Published: February 2020

A new polychelatogen, AXAD-16-1, 2-diphenylethanolamine, was developed by chemically modifying Amberlite XAD-16 with 1, 2-diphenyl-ethanolamine to produce an effective metal-chelating functionality for the preconcentration of Mn(II), Ni(II), Cu(II), Zn(II), Cd(II), and Pb(II) and their determination by flame atomic absorption spectrometry. Various physiochemical parameters that influence the quantitative preconcentration and recovery of metal were optimized by both static and dynamic techniques. The resin showed superior extraction efficiency with high-metal loading capacity values of 0.73, 0.80, 0.77, 0.87, 0.74, and 0.81 mmol/g for Mn(II), Ni(II), Cu(II), Zn(II), Cd(II), and Pb(II), respectively. The system also showed rapid metal-ion extraction and stripping, with complete saturation in the sorbent phase within 15 min for all the metal ions. The optimum condition for effective metal-ion extraction was found to be a neutral pH, which is a great advantage in the preconcentration of trace metal ions from natural water samples without any chemical pretreatment of the sample. The resin also demonstrated exclusive ion selectivity toward targeted metal ions by showing greater resistivity to various complexing species and more common metal ions during analyte concentration, which ultimately led to high preconcentration factors of 700 for Cu(II); 600 for Mn(II), Ni(II), and Zn(II); and 500 for Cd(II) and Pb(II), arising from a larger sample breakthrough volume. The lower limits of metal-ion detection were 7 ng/mL for Mn(II) and Ni(II); 5 ng/mL for Cu(II), Zn(II), and Cd(II), and 10 ng/mL for Pb(II). The developed resin was successful in preconcentrating metal ions from synthetic and real water samples, multivitamin-multimineral tablets, and curry leaves (Murraya koenigii) with relative standard deviations of <3.0% for all analytical measurements, which demonstrated its practical utility.
New Refractive Index Method for Measurement of Alcoholic Strength of Small Volume Samples
Authors: Gerogiannaki-Christopoulou Maria , Kyriakidis Nikolaos V , Athanasopoulos Panagiotis E
Published: February 2020

A study of the correlation between the refractive index (RI) method adopted by the European Community (EC) and a reference pycnometric method for the measurement of alcoholic strength was undertaken. A new RI method with greater accuracy was also developed. Alcoholic strength measured by both RI methods presented a relatively constant negative bias compared with results by the pycnometric method. Differences found between the RI methods and the pycnometric method were 0.6–0.9% (v/v) when RI was measured by the EC method and 0.4–0.5% (v/v) when the new RI method developed in our laboratory was used. Statistical analysis of the results showed that differences between the 2 RI methods and the reference pycnometric method were statistically significant at the 95% confidence level. Correction factors are proposed for the accurate use of measurements of alcoholic strength obtained for small volume samples.
Inductively Coupled Plasma-Mass Spectrometry for the Determination of Elements and Elemental Species in Food: A Review
Authors: Cubadda Francesco
Published: February 2020

Inductively coupled plasma-mass spectrometry (ICP-MS) has definitely emerged as a powerful technique for total element determination and as a sensitive and selective detector in hyphenated methods for speciation analyses of elements in foods. In this review, the analytical challenges of elemental analysis of food and agricultural matrixes are discussed and several applications are examined. Selected examples illustrate the analytical approaches being used so far to address specific issues in various areas of food and nutrition research. The applications discussed include studies on dietary intake, element metabolism in man, transfer of elements through the food chain, effects of food processing and domestic preparation, and authenticity and origin assessment. The use of ICP-MS in the field of analytical quality assurance, food control, evaluation of food contact materials, and radionuclide contamination is also examined. Finally, the hyphenated techniques with ICP-MS detection used for elemental speciation in food are reviewed, and an overview of the main applications currently in the literature is presented. Throughout, recent trends and analytical developments likely to have a major impact on food-related areas are highlighted.