bluuebunny/crossref_metadata_2025_split huggingface dataset:
Determination of Methyl Mercury in Fish by Flameless Atomic Absorption Spectroscopy and Comparison with an Acid Digestion Method for Total Mercury
Authors: Kacprzak Jurgen L , Chvojka Ramon 
Published: February 2020

Abstract
A method for the concurrent determination of methyl mercury and inorganic mercury by flameless atomic absorption spectroscopy (AAS) is described. Fifty-seven samples of juvenile black marlin fish were analyzed for inorganic and methyl mercury, and total mercury was calculated by addition of the 2 values. The sensitivity of the method was estimated to be 0.029 μg for inorganic mercury and 0.033 μg for methyl mercury. The detection limit of the method was about 0.02 μg inorganic mercury or methyl mercury and the error of the method was found not to exceed 10% for samples giving about 10% deflection on the absorbance scale. Samples from the same fish were analyzed by a commonly accepted flameless AAS method for the determination of total mercury. When the results for total mercury from the 2 methods were statistically compared, using a paired t-test, the difference between the results obtained by the 2 methods was found to be insignificant at the 95% confidence level.
Rapid Micro Screening Method for Direct Available P2O5 in Fertilizers
Authors: Thorpe Virginia A 
Published: February 2020

Abstract
A rapid micro screening technique is presented for determining direct available P2O5 in fertilizers containing no organic or condensed phosphates. This modification of the macro color method uses microliter pipets, automatic dispensor pipets, and a double-beam spectrophotometer equipped with a sipper system and printer. The method combines speed and simplicity with accuracy and precision and does not require specialized automated equipment.
Confirmation of Vinyl Chloride in Foods by Conversion to 1-Chloro-1,2-dibromoethane
Authors: Williams David T 
Published: February 2020

Abstract
A semiquantitative method has been developed for the confirmation of vinyl chloride (VC) in foodstuffs. The VC was brominated to give 1-chloro-1,2-dibromoethane which was analyzed by gas-liquid chromatography, using an electron capture detector. The yield of 1-chloro-1,2-dibromoethane varied between 40 and 55%, which permitted a lower limit of confirmation of VC of 15 ppb for vinegar and sherry and 50 ppb for peanut oil.
Gas-Liquid Chromatographic Determination of Nikethamide in Injectable Preparations
Authors: Newton John M 
Published: February 2020

Abstract
A gas-liquid chromatographic (GLC) method, using a 4% XE-60 on 80-100 mesh Gas-Chrom Q column, a flame ionization detector, and anthracene as the internal standard, has been developed for the direct determination of nikethamide. Eight collaborators analyzed 4 samples, using methanol as the solvent; the coefficients of variation obtained ranged from 1.19 to 3.20%. In a limited study with acetone as the solvent, the coefficients of variation ranged from 0.59 to 1.96%. The GLC method with acetone as a solvent has been adopted as official first action.
Gas-Liquid Chromatographic Determination of 3,6-Dichloropicolinic Acid in Soils
Authors: Pik Andrew J , Hodgson Gordon W 
Published: February 2020

Abstract
A gas-liquid chromatographic (GLC) method has been developed for the determination of the experimental herbicide 3,6-dichloropicolinic acid (Dowco 290) in soils. The method involves extraction of 1 g soil samples with 1N NaCl at approximately pH 7, methylation with diazomethane utilizing a microgenerator, and detection by electron capture GLC. Interferences are small, so that a cleanup step is not necessary even at the 6 ppb level. The procedure is rapid, requiring only 45 min/sample. Recoveries range from 84 to 94% at the 6–1000 ppb level with a minimum detectable limit of 6 ppb. Standard deviations for the percentage recovery values vary from 10.9 to 2.3 for the tested range of 6.7–670 ppb, respectively.
Excretion of Hydroxylated Polychlorinated Biphenyl Metabolites in Cows’ Milk
Authors: Gardner Albert M , Righter Herbert F , Roach John A G 
Published: February 2020

Abstract
Four lactating Holstein cows were each given a single oral dose of either 0,5 g 2,5,2′,5′-tetrachlorobiphenyl, 0.5 g 2,5,2′,4′,5′-pentachlorobiphenyl, 1.5 g Aroclor 1242, or 1.5 g Aroclor 1254 in gelatin capsules. Milk samples were collected twice daily at the am and pm milkings and were analyzed for polychlorinated biphenyl (PCB) metabolites and PCBs. Excretion of metabolites in the milk paralleled excretion of the parent PCBs, with maximum amounts eliminated 1 day after dosing. Less than 0.06% of the initial doses of the 2 single components appeared as metabolites in milk over a period of 10 days. Most of the metabolites occurred as conjugates. Only the 4-hydroxy metabolites were found in the milk of cows given single components. Milk samples from cows given Aroclor 1242 or Aroclor 1254 contained 10 and 4 monohydroxy metabolites, respectively. Using the same methodology, no monohydroxy metabolites were detected in whole milk samples from herds accidentally contaminated with a polybrominated biphenyl mixture.
Survey of Food Products for Volatile N-Nitrosamines
Authors: Havery Donald C , Kline David A , Miletta Elaine M , Joe Frank L , Fazio Thomas 
Published: February 2020

Abstract
A variety of food products containing nitrite were analyzed for 14 volatile N-nitrosamines by using a method demonstrated to be sensitive to 10 ppb. A total of 121 food samples were screened for volatile N-nitrosamine content. N-Nitrosopyrrolidine was confirmed in fried bacon at levels up to 139 ppb. N-Dimethylnitrosamine, N-nitrosopyrrolidine, and N-nitrosopiperidine were also confirmed in spice-cure mixtures at levels ranging from 50 to 2000 ppb.
Determination of Bergapten in Fragrance Preparations by Thin Layer Chromatography and Spectrophotofluorometry
Authors: Wisneski Harris H 
Published: February 2020

Abstract
A method has been developed for the determination of bergapten (5-methoxypsoralen), a known phototoxin, in perfumes, colognes, and toilet waters. The bergapten and other lactonic compounds were first isolated from the sample by a series of extractions. The extract containing the bergapten was diluted to a known volume and an aliquot was spotted on a thin layer chromatographic (TLC) plate coated with silica gel G. After 2-dimensional development with hexane - carbon tetrachloride - tert - butylamine (180 + 12 + 9) and hexane-toluene-ethyl acetate-acetic acid (100+10+15+0.5), the TLC plate was dried and the emitted fluorescence of bergapten was measured, using a spectrophotofluorometer equipped with a TLC accessory and coupled to an automatic digital integrator. The amount of bergapten was determined by comparing its peak area to those of bergapten standards. The average recovery for levels of 0.001, 0.005, and 0.01% bergapten was 88%.
Determination of Polychlorinated Dibenzo-p-dioxins and Dibenzofurans in Commercial Pentachlorophenols by Combined Gas Chromatography-Mass Spectrometry
Authors: Buser Hans-Rudolf , Bosshardt Hans Paul 
Published: February 2020

Abstract
Samples of commercial pentachlorophenol (PCP) and its sodium salt (PCP-Na) were examined for the presence of polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs), using a rapid, highly specific method of analysis. Phenolic compounds are removed by alkaline extraction, and the neutral components are fractionated on an alumina minicolumn. After gas chromatographic separation, individual PCDDs and PCDFs are detected by mass fragmentography and their presence is confirmed by complete mass spectral analysis. While some samples had only low amounts of PCDDs and PCDFs, others contained much higher amounts of these components. PCP-Na samples showed the unexpected presence of a tetrachlorodibenzo-p-dioxin. Re-analysis of PCP and PCP-Na samples with high PCDD contents on a high-resolution glass capillary column showed the presence of 3 hexa- and the 2 heptachlorodibenzo-p-dioxins with nearly constant isomeric ratios.
Determination of Arsenic and Selenium in Foods By Electroanalytical Techniques
Authors: Holak Walter 
Published: February 2020

Abstract
Arsenic and selenium are determined in foods by differential pulse polarography and cathodic stripping voltammetry. The sample is digested with nitric acid and magnesium nitrate and then dissolved in dilute hydrochloric acid. An aliquot is removed, the arsenic is chemically reduced to the trivalent state, and interferences are removed by ion exchange before polarography. Selenium is determined in a second aliquot by cathodic stripping voltammetry. Recoveries for both elements in several foods were from 90 to 110%. The relative standard deviations for arsenic at 5 ppm and selenium at 0.48 ppm were 5.8 and 7.3%, respectively.
Analytical Variation When Proportions of Sampled Units Contain the Active Agent
Authors: Kwolek William F , Lillehoj Eivind B 
Published: February 2020

Abstract
When a product consisting of discrete units is sampled, the number of units to be selected depends on p, the proportion of units containing an active agent. If the sample is ground, the problem of subsample size is complicated when only a proportion, g, of the subparticles generated from each unit containing the active agent is active. Procedures have been devised for determining sample size, subsample size, and fineness of grind for wide ranges of p and g. The expected precision of the analytical result is influenced by both sampling variation and analytical variation.
Chemical Confirmation of Diethylstilbestrol Residues in Beef Livers
Authors: Ryan John Joseph , Pilon Jean-Claude 
Published: February 2020

Abstract
A simple chemical technique was developed to confirm the presence of diethylstilbestrol (DES) residues in beef tissues at 2 ppb. The DES-trifluoroacetate (TFA) from the previously published method is hydrolyzed in water-methanol at 55°C for 20 min to free DES which is then extracted into benzene. Trimethylamine and a small amount of heptafluorobutyric (HFB) anhydride are added to effect the smooth conversion of DES to its di-HFB at either room temperature or 60°C. DES-HFB is determined by gas-liquid chromatography with electron capture detection on a 6′ × 4 mm id column of 3% OV-210 at 190°C. This procedure yields 2 peaks for DES-HFB (retention times 2.7 and 4.8 min for the cis and trans, respectively) which are resolved from the 2 DES-TFA peaks (retention times 2.3 and 3.3 min for cis and trans, respectively). The sensitivity of detection of DES-HFB is increased by a factor of 4–5 over that for DES-TFA. This chemical technique was successfully applied to purified extracts of beef liver fortified with DES at 2–10 ppb with recoveries from 60 to 110%.
Colorimetric Determination of Zirconium in Antiperspirant Aerosols
Authors: Beavin Paul 
Published: February 2020

Abstract
A rapid direct dilution procedure for the estimation of soluble zirconium and a fusion procedure for the determination of total zirconium (soluble and insoluble forms) in cream base concentrates prepared from antiperspirant aerosols are described. The direct dilution procedure involves extraction of soluble zirconium with HCl (55+45). The filtered extract is reacted with alizarin red S to form a stable colored complex which is measured spectrophotometrically. The fusion procedure involves ashing the aerosol concentrate followed by fusion of the ash with potassium pyrosulfate to form an acid-soluble melt. Zirconium is precipitated from solution as the hydroxide and washed to eliminate interfering ions, particularly sulfate. After redissolving in HCl (55+45) and reacting with alizarin red S, total zirconium is measured. Zirconyl chloride octahydrate, assayed gravimetrically by hydroxide precipitation and conversion to the oxide, is used as the zirconium reference standard. Concentration range of zirconium measured was 200–500 μg/100 ml. Recoveries of standard zirconium added to commercial aerosols labeled to contain aluminum and zirconyl hydroxychlorides ranged from 97 to 101% by the fusion procedure. Analysis of these aerosols by direct dilution gave generally slightly lower results than by fusion. It is recommended that the procedures be collaboratively studied after further testing of their general applicability to a variety of drugs and cosmetics.
Selenium in Foods: Evaluation of Atomic Absorption Spectrometric Techniques Involving Hydrogen Selenide Generation and Carbon Furnace Atomization
Authors: Ihnat Milan 
Published: February 2020

Abstract
The performance of hydrogen selenide generation- and carbon furnace atomization-atomic absorption spectrometry, with a semiautomated trace metal accessory and a carbon rod atomizer, respectively, was evaluated for the determination of selenium in foods. Samples were digested with nitric, perchloric, and sulfuric acids for both procedures. Hydrogen selenide was generated with stannous chloride/potassium iodide/zinc from 20 ml aliquots in a hydrochloric-sulfuric acid medium and directed into an argon-hydrogen-entrained air flame. Sample matrix interferences in the carbon furnace technique were minimized by isolating selenium by precipitation with ascorbic acid and redissolution in nitric-perchloric acid prior to taking 5 μl aliquots for estimation; precision was significantly improved by incorporating 5000 μg nickel/ml into analytical solutions. For the hydrogen selenide and carbon furnace techniques, respectively, the following data were obtained for untreated standard solutions: sensitivity, 0.15 and 10.0 ng/ml; absolute sensitivity, 2.6 and 0.05 ng; detection limit, 0.4 and 90 ng/ml; absolute detection limit, 7 and 0.45 ng. The detection limit and absolute detection limit for samples were 2.5 ng/ml and 50 ng, respectively, for the hydrogen selenide method, and 25 ng/ml and 0.15 ng, respectively, for the carbon furnace method. Taking into consideration these figures and the practical aspects of both methods, the overall performance of the hydrogen selenide method was superior.
Distribution of Aflatoxins in Some Samples of Peanuts
Authors: Diprossimo Vincent P 
Published: February 2020

Abstract
Naturally occurring C aflatoxins were found at approximately 20 times the level of B aflatoxins in one lot of roasted, blanched peanuts. Official methods, as well as high-pressure liquid chromatography, were used to confirm this finding. Additional routine sample analysis data of raw and roasted peanuts revealed that this finding is not so unusual as formerly thought. It was found that 9.8% of the raw peanut samples contained higher levels of G than B aflatoxin; 4.9% containing 2–8 times more G than B aflatoxins. In a smaller sampling of roasted peanuts, 28% of the contaminated peanuts contained more G than B aflatoxins.
Impurities in Commercial Saccharin. I. Impurities Soluble in Organic Solvents
Authors: Stavrić Bozidar , Klassen Raymond , Arnold W 
Published: February 2020

Abstract
Thirteen saccharin samples used for carcinogenicity tests in animals in various laboratories were analyzed for their chemical purity. Although most of the impurities were water-soluble, some were mainly soluble in organic solvents. These impurities were extracted with chloroform-methanol from a water solution of sodium saccharin. Samples obtained as acid-saccharin were converted to the sodium form before extraction. The major impurity in commercial saccharin, o-toluenesulfonamide, was also soluble in this system. Impurities were separated by gas-liquid chromatography of the underivatized, concentrated extract. Eleven major, well separated peaks were collected from the gas chromatographic column and identified by mass spectroscopy. Some of the peaks were compared with known standards. Qualitative and quantitative differences in impurities were observed among different saccharin samples. The identified impurities (in order of appearance from the gas-liquid chromatographic column) were as follows: o-toluenesulfonamide; p-toluenesufonamide; 1,2-benzisothiazole 1,1-dioxide; 1,2-benzisothiazoline 1,1-dioxide; diphenylsulfone; o,o′-ditolylsulfone; o,m′-ditolylsulfone, o,p′-ditolylsulfone; m,p′-ditolylsulfone; p,p′-ditolylsulfone, and tetracosane.
Detection of O,O-Diethyl-O-(2,5-dichlorophenyl) Phosphorothioate and O,O-Diethyl-O-(3,6-dichloro-2-pyridyl) Phosphorothioate in Meat Fat
Authors: Luke Barry G , Dahl Colin J 
Published: February 2020

Abstract
Two previously unreported organophosphorus residues have been detected in meat fat. The first, O,O-diethyl-O-(2,5-dichlorophenyl) phosphorothioate, apparently results from the debromination of bromophos-ethyl, while the other, O,O-diethyl-O-(3,6-dicliloro-2-pyridyl) phosphorothioate, presumably arises by the monodechlorination of chlorpyriphos. Mass spectral evidence is presented in support of the assigned structures and gas-liquid chromatographic retention data for the residues and their oxygen analogs are provided.
Microchemical Oxygen Flask Sulfur Determination: General Review and Collaborative Study of an Alternative Method Using Thorin-Methylene Blue Indicator
Authors: Scroggins Laverne H 
Published: February 2020

Abstract
Recent collaborative studies of microchemical oxygen flask sulfur determinations are summarized and compared statistically, and the 1975 collaborative study is presented. This volumetric technique, using a peroxide solution as absorbent, barium perchlorate as titrant, and a combination of thorin and methylene blue as indicator, was tested by 8 collaborators. Data from 72 determinations were reported. The samples studied were sulfanilamide, benzylisothiourea hydrochloride, cystine, potassium sulfate, and potassium sulfate with a phosphate additive. Overall statistical results for the 3 pure organic compounds gave satisfactory values: average standard deviation 0.10, overall average deviation of the mean from the theoretical value 0.13, and average bias −0.04. The overall average deviation of the mean from the theoretical value for the potassium sulfate compound was high (1.94) in this study, and that of the phosphated potassium sulfate compound was even higher (6.46). Thorin-methylene blue does not require a titration assembly (required by tetrahydroxyquinone) and has greater stability than dimethylsulfonazo III whose indicator lag-time causes troublesome pseudo end points. However, a critical factor, when using thorin-methylene blue, is the masking effect of foreign ions. All reagents must be as pure as possible, since concentrations of chloride, fluoride, nitrate, phosphate, potassium, and sodium interfere. The thorin-methylene blue method for sulfur determination has been adopted as official first action as an alternative oxygen flask microchemical method of analysis.
High-Pressure Liquid Chromatographic Determination of Piperine in Black Pepper (Piper nigrum)
Authors: Galetto William G , Walger Denise E , Levy Susan M 
Published: February 2020

Abstract
High-pressure liquid chromatography is a rapid, sensitive, and specific method for the quantitative determination of piperine in black pepper. The whole product is ground and extracted with ethylene dichloride, while the oleoresin is simply diluted with chloroform. The solution is chromatographed on a column of Porasil A, with chloroform as the liquid phase. Piperine concentration is measured by its ultraviolet absorption at 254 nm. Quantitative results were consistently lower than those obtained by using ultraviolet or Kjeldahl nitrogen methods.
Gas-Liquid Chromatographic Determination of Levamisole Residues in Bovine Milk
Authors: Smith John E , Pasarela N Robert , Wyckoff John C 
Published: February 2020

Abstract
A gas-liquid chromatographic (GLC) method is described for determining residues of levamisole, (1-)-(2,3,5,6-tetrahydro-6-phenylimidazo[2,1-b] thiazole), in milk. Levamisole is extracted from an alkaline milk sample with water-saturated ethyl acetate. After co-extractives are removed by various partitionings, the levamisole concentration is measured by GLC by using an alkali (RbSO4) flame ionization detector, vs. an external standard. This method is satisfactory for determining levamisole residues as low as 0.01 ppm in bovine milk. Apparent residues in control milk samples averaged &lt;0.001 ppm. Recoveries of 0.01–2.0 ppm added levamisole ranged from 86.5 to 113%. Animals treated with various Tramisol® formulations showed apparent levamisole residues below the validated sensitivity of the method (0.01 ppm) at sampling periods exceeding 48 hr.
Determination of Sterigmatocystin in Corn and Oats by Gel Permeation and High-Pressure Liquid Chromatography
Authors: Stack Michael E , Nesheim Stanley , Brown Nathan L , Pohland Albert E 
Published: February 2020

Abstract
Corn and oats samples are extracted with acetonitrile-water, followed by partition of the extract against hexane, transfer to chloroform, and elution from a silica gel column. The extract is purified by gel permeation chromatography on an automatic instrument. Reverse phase high-pressure liquid chromatography, using a 254 nm ultraviolet detector and 0.1M KH2PO4-acetonitrile (7+5) as the mobile phase, is used for quantitation. The average recovery from 6 samples of corn to which 0, 25, 50, and 100 μg sterigmatocystin/kg had been added was 59%, with a coefficient of variation of 8.4%. The average recovery from oats fortified at the same levels was 74%, with a coefficient of variation of 12%. A confirmation procedure based on hemiacctal derivative formation on a thin layer chromatographic plate is also described.
Ion Selective Method for the Determination of Nitrite in Smoked Fish
Authors: Sherken Stephen 
Published: February 2020

Abstract
In a direct ion selective electrode method for determining nitrite in smoked fish, the nitrite extracted from the sample is converted to nitrous acid with a measured addition of an acid buffer. The released nitrous acid is measured by a nitrogen oxide electrode. A known addition procedure is used to accurately measure the amount of nitrite in solution and the nitrite concentration is determined directly from Gran’s plot paper. Recoveries of nitrite from spiked smoked chub samples ranged from 94.0 to 100.0% with an average of 96.7 and a relative standard deviation of ±1.9% at the 100 ppm level. Results from the ion selective method were comparable with those from the official first action AOAC method 24.037–24.038.
Silicic Acid Chromatographic Separation of Polychlorinated Biphenyls and Pesticides: Some Contaminants and Limitations
Authors: Huckins James N , Stalling David L , Johnson James L 
Published: February 2020

Abstract
The Armour and Burke method for separating polychlorinated biphenyls (PCBs) from pesticides involves the use of silicic acid. However, we detected di-2-ethylhexyl phthalate, PCBs, and other impurities as interfering contaminants in several batches of silicic acid. The presence of H2SO4 in some batches of silicic acid is inferred. The acid may be responsible for the production of contaminants which interfere in gas-liquid chromatographic analyses. Contaminants in silicic acid are reduced by extracting the adsorbent with solvent, and/or partitioning the concentrated pesticide fraction with 1N NaOH. These purification procedures provide separations relatively free of impurities, but result in reduced adsorbent activity. PCB-pesticide separations are reproducible only within a given batch lot of silicic acid because of the varying adsorbent characteristics of each lot. Alternative adsorbents should be explored for most PCB-pesticide separations.