bluuebunny/crossref_metadata_2025 huggingface dataset:
Colorimetric Determination of Zirconium in Antiperspirant Aerosols
Authors: Beavin Paul
Published: February 2020

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

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

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

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

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

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

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

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 <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

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

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

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.
Infrared Studies of the Dynamic Aspects of Hydrogen-Bonding in Hydroxylated Metabolites of 2,5,2′,5′,-Tetrachlorobiphenyl
Authors: Chen Jo-Yun T
Published: February 2020

Infrared spectral studies indicate that the hydroxylated 2,5,2′,5′-tetrachlorobiphenyls (TCBs) exist in a dynamic equilibrium of free, intramolecular, and intermolecular hydrogen-bonded forms. The relative abundances of the various species depend upon the polarity of the solvents as well as the physical state of the compound resulting from different configurations, i.e., the monohydroxylated 2,5,2′,5′-TCBs exist as cis and trans rotational isomers of OH with respect to the chlorine atom in the ortho position, and 3,4-dihydro-3,4-dihydroxy-2,5,2′,5′-TCB exists as 2 trans conformers with the OH groups either axial-axial or equatorial-equatorial with respect to the plane of the attached ring. In the solid state, the dimer or polymer is preferred with intermolecular hydrogen-bonding occurring between OH groups.
Rapid Thin Layer Chromatographic Method for the Detection of Histamine in Fish Products
Authors: Schutz David E , Chang George W , Bjeldanes Leonard F
Published: February 2020

A rapid, convenient thin layer chromatographic (TLC) method for detecting histamine in fish samples is described. Samples of press juice or fish flesh are applied directly to TLC plates. The plates are developed with acetone-ammonium hydroxide (95+5) and the spots are visualized with ninhydrin or Pauly’s reagent. Chromatographic separation of histamine from other fish components is readily achieved by this method.
A Simplified Method for the Gas-Liquid Chromatographic Determination of Methyl Mercury in Fish and Shellfish
Authors: Watts James O , Boyer Kenneth W , Cortez Anthony , Elkins Edgar R
Published: February 2020

A simple acetone wash of the fish sample which removes lipids and other organic materials replaces the cysteine cleanup specified in other methods. Methyl mercury is freed by hydrochloric acid, extracted into benzene, and determined with a gas-liquid chromatograph equipped with an electron capture detector. The method is quantitative for methyl mercury levels as low as 0.10 ppm in fish and shellfish. Ethyl mercury chloride may be used as an internal standard to detect unsuspected error or instrumental parameter variation.
A Simple Spectrophotometric Method for the Determination of Carbofuran Residues
Authors: Rangaswamy Jois R , VijayaShankar Yadathora N , Prakash Shimoga R
Published: February 2020

A method has been developed for carbofuran residues, based on coupling carbofuran (2,3-dihydro-2,2-dimethyl-7-benzofuranyl methyl carbamate) with diazotized aniline to form a yellow compound with an absorption maximum at 460 nm. The relationship between absorbance and concentration is linear for 1–10 μg carbofuran/5 ml. The method is sensitive and can be applied to the determination of levels as low as 0.025 ppm carbofuran in a 40 g crop or soil sample.
Identification of Human Seminal Acid Phosphatase by Electrophoresis
Authors: Stolorow Mark D , Hauncher James D , Stuver Willard C
Published: February 2020

Recent advances in forensic science in the identification of human seminal acid phosphatase are presented, with particular attention to the acrylamide gel electrophoretic method. In that method a difficulty in distinguishing seminal acid phosphatase from certain fecal phosphatases has been observed and an attempt is made here to distinguish the phosphatases from one another experimentally by differential substrate specificity. 4-Methylumbelliferyl phosphate and α-naphthyl acid phosphate are used as reaction substrates. Although seminal and vaginal acid phosphatases are differentiated by the modified method, fecal phosphatase is not clearly differentiated from seminal acid phosphatase.
Systematic Approach to the Detection of Explosive Residues. IV. Military Explosives
Authors: Midkiff Charles R , Washington Willard D
Published: February 2020

Part IV of the series encompasses tests for the detection and identification of military explosives collected at the scene of a criminal bombing. Major categories and typical formulations of some common military explosives are described. Tests are described and evaluated for the identification of 2,4,6-trinitrotoluene, cyclotrimethylenetrinitramine, and pentaerythritol tetranitrate. Thin layer chromatography and infrared spectroscopy are used for the identification of major explosive components. Tests for minor components to enable characterization and to distinguish similar compositions are included.
Confirmation of Results of Rapid Screening Test for Aflatoxins Performed at Corn Elevator
Authors: Shotwell Odette L , Shannon Gail M , Goulden Marion L
Published: February 2020

A screening method for corn and corn products, based on a minicolumn, was modified slightly to assay 60 lots of corn at one elevator to determine whether they could be sold as animal feed. To be salable, the lots had to contain less than 20 ppb total aflatoxin. Aflatoxin levels in the lots were later determined by the official AOAC method for corn to check effectiveness of the screening. No lot had been designated for sale that contained 20 or more ppb total aflatoxin.
Stability of Patulin to Sulfur Dioxide and to Yeast Fermentation
Authors: Burroughs Leonard F
Published: February 2020

The affinity of patulin for sulfur dioxide (SO2) is much less than was previously reported and is of little significance at the SO2 concentrations (below 200 ppm) used in the processing of apple juice and cider. However, at concentrations of 2000 ppm SO2 and 15 ppm patulin, combination was 90% complete in 2 days. Removal of SO2 liberated only part of the patulin, which suggests that 2 mechanisms are involved: one reversible (opening the hemiacetal ring) and one irreversible (SO2 addition at the double bond). Tests with 2 yeasts used in English commercial cider making confirmed that patulin is effectively removed during yeast fermentation.
Mass Spectral Confirmation of Aflatoxins
Authors: Haddon William F , Masri M Sid , Randall V Garcia , Elsken Richard H , Meneghelli Barry J
Published: February 2020

Two methods for mass spectral (MS) confirmation of aflatoxins in agricultural products and in physiological fluids are described. In the first method, electron ionization (EI) mass spectra are obtained following isolation by thin layer chromatography (TLC) and compared with available reference mass spectra to provide structural confirmation. Extensive sample cleanup is required for confirmation at the 10—1000 ppb level and minimum sample size is 10—50 ng aflatoxin isolated by TLC. The second method restricts the MS scanning to particular ions which are characteristic of the suspected aflatoxins and requires spectrometer resolution above 5000. The latter method, called high resolution selected ion monitoring (HRSIM), has a sensitivity below 0.0001 μg for aflatoxin B1 and makes possible direct analysis of complex mixtures. Employing HRSIM analysis on complex mixtures lowers the detection limit for aflatoxins M1 and B1 by 100-fold or more below the limit for highly purified samples. We attribute this dramatic sensitivity enhancement to a reduction in surface bonding between the aflatoxins and the glass sample containers used to introduce the samples. The HRSIM is generally applicable to compounds that cannot be separated by gas chromatography prior to MS analysis.
High Performance Liquid Chromatographic Determination of Provitamin A in Orange Juice
Authors: Stewart Ivan
Published: February 2020

A quantitative method has been developed for the determination of α- and β-carotenes and β-cryptoxanthin, the provitamin A carotenoids in orange juice. The carotenoids were separated by high performance liquid chromatography on a single column in approximately 30 min. The procedure may also be used to measure zeta-carotene and α-cryptoxanthin.
Practical Considerations in the Use of High Performance Liquid Chromatographic Columns
Authors: Majors Ronald E
Published: February 2020

The practical aspects of high performance liquid chromatographic (HPLC) column preparation and operation are reviewed. Recent advances in columns are briefly covered. Porous layer beads and the new microparticles are compared. The design of HPLC columns with respect to optimum dimensions in analytical and preparative techniques and the materials used for column construction are detailed. The effects on column performance of extra-column volumes (i.e., connecting tubing and fittings) and injection procedures and techniques are pointed out. Procedures for preparing the column, including slurry packing techniques for microparticles, are given. The influence of solvent purity in isocratic and gradient elution in column operation and practical techniques for removing impurities are presented. Solvents and buffers useful for operation in the far ultraviolet region (190—210 nm) are tabulated, and a practical example of the use of this wavelength region for the detection of carbohydrates is presented. The practical aspects of liquid-solid chromatography (LSC) including activity and retention time reproducibility are discussed. Difficulties encountered in LSC are listed and suggestions are made to solve them. The advantages and disadvantages of the new chemically bonded phase packings are covered. Details of a new technique, ion-pair partition chromatography, are presented along with suggested applications.
Identification of Hexachlorobenzene as a Contaminant in Laboratory Plastic Wash Bottles
Authors: Rourke David R , Mueller Wolfgang F , Yang Raymond S H
Published: February 2020

Hexachlorobenzene (HCB) is identified as a contaminant in some Nalgene plastic wash bottles by gas-liquid chromatography-mass spectrometry. Of 34 new, unused Nalgene bottles tested, all 30 of the conventional polyethylene wash bottles contained significant quantities of HCB; the remaining 2 linear polyethylene and 2 polyvinyl chloride storage bottles contained little or no HCB.
Gas-Liquid Chromatographic Determination of Butylated Hydroxyanisole and Butylated Hydroxytoluene in Edible Oils
Authors: Senten Jozef R , Waumans Jozef M , Clement Jean M
Published: February 2020

A method is described for the quantitative determination of butylated hydroxyanisole and butylated hydroxytoluene in edible oils. Both antioxidants are extracted with acetonitrile, and quantitated by gas-liquid chromatography, using a hydrogen flame ionization detection system and di-tert-butyl-4-hydroxyanisole as an internal standard. The standard addition technique is used. Recoveries from oils containing 70–400 ppm by weight of both antioxidants ranged from 88 to 104%.
Survey of Finfish and Shellfish for Volatile N-Nitrosamines
Authors: Havery Donald C , Fazio Thomas
Published: February 2020

A variety of finfish and shellfish obtained on the local retail market were analyzed for 14 volatile N-nitrosamines by using a gas-liquid chromatographic method demonstrated to be sensitive to 10 ppb (μg/kg). A total of 78 samples (fresh, frozen, and canned), representing 26 varieties of fish, were analyzed. No nitrosamines were found.
Method for the Flotation Oil Extraction of Light Filth from Ground Capsicums
Authors: Thrasher Joel J , Colliflower Emma Jean
Published: February 2020

The present official first action method for ground capsicums, 44.123, was adopted in 1945 and there have been great changes in processing and examination of spices since that time. The proposed method involves isopropanol pretreatment, followed by wet sieving and extraction of the light filth from 60% ethanol with flotation oil. The filter papers were clean and recoveries were good (95%) for 5 different lots of capsicums and annato spiked with insect fragments and rodent hairs.
New Colorimetric Method for Folic Acid Assay in Dosage Forms
Authors: Ramana Rao Griddaluru , Mahajan Surinder N , Kanjilal Geeta , Mohan Katta R
Published: February 2020

A new colorimetric method has been developed for estimating folic acid. The British Pharmacopoeial method has been modified to reduce folic acid to 2,4,5-triamino-6-hydroxypyrimidine (TAHP), which is treated with nin-hydrin to yield a stable purple complex. Participation of 5-amino and 6-hydroxy groups of TAHP in the color reaction with ninhydrin is suggested on the basis of experimental evidence. The color obtained has an absorbance maximum at 555 nm and obeys Beer’s law in the concentration range of 4.5 to 45 μg folic acid/ml. The method has been successfully used for assaying folic acid, its tablets, and injections.
Fluorometric Determination of Glycerol in Wine—Comparison with Other Known Procedures
Authors: Avellini Paolo , Damiani Pietro , Burini Giovanni
Published: February 2020

The glycerol content of 6 wines was evaluated by using 3 different preliminary treatments and, subsequently, a variety of instrumental and chemical procedures (fluorometric, vapor phase chromatography of trimethylsilyl derivatives, volumetric, and colorimetric). The data showed that all these procedures are applicable; in particular, the fluorometric procedure, which has not been used until now, provides average recoveries of added glycerol ranging from 99.3 to 100.9%, with relative standard deviations ranging from 2.9 to 3.2%. Vapor phase chromatography provides average recoveries of added glycerol ranging from 99.8 to 100.1%, with relative standard deviations ranging from 1.0 to 2.7%. Therefore, the fluorometric procedure appears especially useful for reliable routine analyses, because it is specific for glycerol and provides results that are unaffected by preliminary treatment. Thus it allows analysis of diluted wine, when the sugar content does not exceed 5 g/L; sweet wines must undergo an ion exchange pretreatment.
Spectroscopic and Chromatographic Identification of Dimethylamphetamines
Authors: Bailey Keith , Gagné Denise R , Legault Donald , Pike Richard K
Published: February 2020

The qualitative analysis of the 6 isomeric dimethylamphetamines (both methyl groups on the aromatic ring) is described. Their ultraviolet, mass, and proton magnetic resonance spectra are similar, but infrared spectra allow a positive identification to be made, and reference spectra are provided. Melting point and gas-liquid and thin layer chromatographic data are also presented.
Specific Determination of Sucrose in Honey
Authors: White Jonathan W
Published: February 2020

This paper describes a procedure for determining sucrose in honey without its preliminary separation. Interference from the large excess of glucose is removed by treating with glucose oxidase-catalase, and then the glucose from invertase hydrolysis of sucrose is measured. Sucrose is difficult to measure in honey because of its low concentration and the presence of at least 24 other sugars. Standard deviation between duplicates for 50 honey samples containing from 0.06 to 10.6% sucrose was 0.19; no known honey sugars interfered. The selective adsorption method for separating sucrose from interfering oligosaccharides is too slow for repetitive analysis of honey for sucrose only, although it is 8 times more sensitive than the procedure described. Results of analysis of 13 honey samples for sucrose by this procedure (averaging 1.66%) and the selective adsorption method (averaging 1.59%) did not differ significantly.
Separation and Analysis of the Pyrethrins by Combined Gas-Liquid Chromatography-Chemical Ionization Mass Spectrometry
Authors: Holmstead Roy L , Soderlund David M
Published: February 2020

Pyrethrins, the 6 naturally occurring insecticidal esters of pyrethrum extract, were analyzed by combined gas-liquid chromatography-chemical ionization mass spectrometry. Separation was best on an OV-25 column with temperature programming. The chemical ionization mass spectra for the 6 esters as well as for the thermally isomerized pyrethrins I and II are reported and discussed. Using selective ion monitoring, a lower limit of detectability of all 6 esters was 114 ng of total extract injected on the column.
Determination of Free Urea in Fertilizers Containing Urea Formaldehyde Polymers
Authors: Barbera Andrea , Canepa Diego
Published: February 2020

This report describes a method for determining free, unreacted urea nitrogen in mixed compounds containing condensation products of urea and formaldehyde by using an ammonia gas-sensing electrode. Free urea is determined by potentiometrically measuring the ammonia produced following exhaustive hydrolysis by urease and subtracting the amount of ammonia present before enzymatic hydrolysis. Urea of condensed polymers does not interfere in free urea determination.
Collaborative Study of High Pressure Liquid Chromatographic Method for Determining Methyl Parathion
Authors: Jackson Edwin R
Published: February 2020

Methyl parathion in technical material, 4 lb/gal. emulsifiable concentrate, and 6 lb toxaphene-3 lb methyl parathion/gal. emulsifiable concentrate was chromatographed on microparticulate silica with 40% water-saturated chloroform mobile phase and 254 nm ultraviolet detection. Ten collaborators reported results on 3 matched pairs of samples by peak height measurements with acetophenone as internal standard. The mean of the coefficients of variation for the 6 samples was 1.71%. Results for 4 of the samples were compared with gas-liquid chromatographic results on the same samples. No difference in the means by the 2 methods was noted at the 95% confidence level. The method has been adopted as official first action.
Reverse Phase High Pressure Liquid Chromatography of Vitamin A in Margarine, Infant Formula, and Fortified Milk
Authors: Thompson James N , Maxwell William B
Published: February 2020

Retinol was determined in margarine (50 mg), infant formula (1 ml), and fortified milk (1 ml) by saponification in centrifuge tubes, extraction of the unsaponifiable lipid with hexane, and high pressure liquid chromatography (HPLC) in 90% methanol on a 25 cm × 3.2 mm column containing 10 μm LiChrosorb reverse phase. β-Carotene was determined using the same column and 99% methanol as eluant. The vitamins in the eluate were identified and measured from their absorption at 325 (retinol) and 453 nm (β-carotene), using a computing integrator. Retinol and carotene were prominent peaks in the chromatograms from properly fortified samples and were satisfactorily separated from other materials. In a survey of 12 different margarines for retinol, the results from liquid chromatography agreed with those of a variety of Spectrophotometric and fluorometric procedures but they were obtained with greater ease and they could be interpreted more confidently. The recovery of retinol from oil was better than 99%. The coefficients of variation were 6.8% for 12 replicate analyses of a margarine for retinol and 5.4% for 10 replicate analyses of a margarine for β-carotene.
Argon Plasma Emission Spectroscopic Determination of Boron in Fertilizers
Authors: Melton James R , Hoover William L , Morris Patricia A
Published: February 2020

An atomic emission spectroscopic method is described for the rapid, precise, and accurate determination of boron in fertilizers at levels ≥0.002%. Acid-soluble boron is determined by argon plasma emission spectroscopy at 2497. 73Å. Lithium is added to mask enhancement of emissions by other alkali metals.
Comparison of Iodometric Titration, Potentiometric Titration, and Bromide Ion Electrode Determination for Bromide in Brominated Vegetable Oils
Authors: Conacher Henry B S , McKenzie Arthur D
Published: February 2020

Iodometric titration, potentiometric titration, and bromide selective ion electrode techniques have been evaluated for determining bromide in brominated vegetable oils. In general, the 2 titration methods gave similar percentages for the bromide content of several brominated vegetable oils, and similar recoveries of approximately 96% from soft drinks. The specific ion technique gave lower and more variable percentages for the bromide content of the brominated vegetable oils and a lower recovery of 91.6% from soft drinks. Of the first 2 methods, the potentiometric method was selected because of ease and speed of measurement.
Collaborative Study of Gas-Liquid Chromatographic Determination of Methaqualone in Pharmaceutical and Clandestine Preparations
Authors: Hanel Harold F
Published: February 2020

Eight laboratories collaboratively studied a procedure for the quantitative determination of methaqualone. HCl in pharmaceutical and clandestine preparations. Methaqualone is extracted from an aqueous bicarbonate solution into chloroform and quantitated by gas-liquid chromatography on a 3% OV-1 column. Tetraphenylethylene is used as an internal standard. Two commercial preparations and 4 sample mixtures prepared by the author were studied. Recoveries for the 4 prepared samples ranged from 100.0 to 102.6%, and the coefficients of variation ranged from 1.58 to 4.15% for the 6 samples studied. The method has been adopted as official first action.
Gas-Liquid Chromatographic Determination of Residues of Methane sulfonate of m-Aminobenzoic Acid Ethyl Ester in Fish
Authors: Sills Joe B , Luhning Charles W
Published: February 2020

In this gas-liquid chromatographic procedure for determining residues of methanesulfonate of m-aminobenzoic acid ethyl ester (MS-222) in fish muscle, homogenized tissue is extracted with distilled water, and proteins are removed by coagulation with trichloroacetic acid, centrifugation, and filtration. After careful pH adjustment of the filtrate, MS-222 is partitioned into benzene-ethyl ether and measured by alkali flame ionization gas chromatography. Tissues with known additions of 1–19 μg MS-222/ g were analyzed, with recoveries of 84–95%.
Anritsu Milk-Checker for Determining Fat in Milk
Authors: Sherbon John W , Shipe W Frank
Published: February 2020

A new instrument for measuring the fat content of milk was collaboratively studied to see if it performed similarly to machines specified in the official AOAC method. The results indicate that the instrument meets existing AOAC calibration criteria, and it has been included in the official methodology.
Simple Sensitive Technique for Detecting Organochlorine Pesticides on Thin Layer Chromatograms
Authors: Ludwick Adriane G , Lau Aldrich N K , Ludwick Larry M
Published: February 2020

Chlorinated hydrocarbon pesticides can be quickly detected using commercially available thin layer chromatographic plates dipped in an acetone solution of silver nitrate. The limits of detection are functions of the pesticide, adsorbent, developing system, and concentration of the silver nitrate in acetone solution. On exposure to ultraviolet light, 0.002 μg 2,4,5-T produced clear darkening within 30 min on precoated silica gel plates (polyvinyl alcohol binder) coated with a solution of 0.1% silver nitrate in acetone. For this system, a 60-min detection period was necessary for a 0.05% coating solution. On the silica gel plates (polyvinyl alcohol binder, 0.1% silver nitrate), 0.02 μg lindane is detected within 75 min. For alumina plates (polyvinyl alcohol binder, 0.1% silver nitrate), 0.025 μg aldrin is detected within 10 min. Darkening of this plate prohibits the detection of 0.012 μg aldrin. On silica gel plates (polyvinyl alcohol binder, 0.1% silver nitrate), 0.015 μg aldrin can be detected within 45 min. The method described provides sensitivities equal to or exceeding literature values.
Gas-Liquid Chromatography and Liquid Chromatography of Ethylenethiourea in Fresh Vegetable Crops, Fruits, Milk, and Cooked Foods
Authors: Onley John H , Giuffrida Laura , Ives N Fred , Watts Randall R , Storherr Robert W
Published: February 2020

The Onley-Yip procedure for determining ethylenethiourea (ETU) in milk and crops was modified to reduce interferences by the ethylenebisdithiocarbamates (EBDCs). A 20 g cropmethanol extract is cleaned up by adsorbing the sample onto Gas-Chrom S, desorbing ETU, and eluting ETU from aluminum oxide with chloroform containing ethanol. ETU is converted to the S-butyl derivative for gas-liquid chromatography (GLC) and flame photometric detection (sulfur mode). For liquid chromatography (LC), ETU is cleaned up on another aluminum oxide column and injected directly. LC and GLC results are confirmed by thin layer chromatography. A cooking procedure based on conversion of EBDCs to ETU is included for surveying crops for possible EBDC content. Recoveries from 8 crops and milk fortified at 0.05 ppm ETU ranged from 73 to 100%.
Estimation of Milligram and Submilligram Amounts of Methylthiophanate Fungicide
Authors: Miller Vernon L , Csonka Elizabeth , Gould Charles J
Published: February 2020

A procedure is described for estimating methylthiophanate (1,2-bis (3-methoxycarbonyl-2-thioureido) benzene) (MT) in the range of 0.002–1.0 mg/ml. In the 0.2–1.0 mg/ml range, MT is shaken with a copper-triethanolaminealkali reagent, the precipitate is filtered, and excess copper is reacted with pyridine-thiocyanate and measured by spectrophotometry or by comparison with described artificial standards for use as a field test. In the 0.002–0.1 mg range, the copper-MT compound may be estimated directly by spectrophotometry, or excess copper is determined by a diethyldithiocarbamate procedure.
Assuring Reliable Performance of Antibiotic Assay Media
Authors: Freeman Katharine A , Johnson Diana P , Garth Mary A
Published: February 2020

The Microbiological Assay Branch of the National Center for Antibiotics Analysis assays over 100,000 samples of antibiotic products annually, using more than 1000 lb dehydrated media. The media must be consistently dependable to produce accurate, reliable test results. To assure that the supply of media will meet the established requirements, each lot before purchase is subjected to a series of trials designed to examine growth support, sensitivity, and behavioral and physical factors. Actual antibiotic assays are conducted with the test medium, and performance is rated against a control medium. Controls on the system reduce the variables to allow appraisal of the medium itself.
Interlaboratory Study of Methods for Determining Global Migration of Plastic Materials in Liquids Simulating Fatty Foodstuffs
Authors: Rossi Luigi
Published: February 2020

Interlaboratory studies initiated by the Commission of the European Communities tested 3 methods for determining the global migration of plastic materials in liquids simulating fatty foodstuffs. In each method, a sample of plastic material was weighed before and after it was placed in contact with fatty simulant. The fat absorbed by the sample, extracted or dissolved by suitable solvents, was determined by gas chromatography or radiometry. Each method was fairly reliable and specific. Reproducibility in a single laboratory was satisfactory, but less so between laboratories.
Gas-Liquid Chromatographic Determination of Cholesterol and Other Sterols in Foods
Authors: Sheppard Alan J , Newkirk David R , Hubbard Willard D , Osgood Theodore
Published: February 2020

A gas-liquid chromatographic (GLC) method, using the butyryl esters of sterols, has been developed for the measurement of cholesterol, stigmasterol, sitosterol, and campesterol in foods. An immobile phase of 1 % SE-30 coated on 100–120 mesh Gas-Chrom Q packed in a 6′ × 4 mm id glass column operated at 255°C was the most satisfactory of 7 column packings evaluated. Extraction with chloroform-methanol gave 98.7 % recovery with a coefficient of variation of 1.8% for cholesterol added to a variety of foods. When cholesteryl palmitate was added to vegetable oil and the butyryl derivative was prepared, followed by GLC analysis, the recovery was 99.3% with a coefficient of variation of 0.9%. Amounts as low as 1 mg/100 g food can be detected with a precision of 2.5%. The results of the analysis of a variety of foods for cholesterol, campesterol, sitosterol, and stigmasterol are given.
High Pressure Liquid Chromatographic Determination of Mannitol and Sorbitol in Sugarless Chewing Gums
Authors: Samarco Eugene C
Published: February 2020

A precise and accurate high pressure liquid chromatographic method is presented for the simultaneous separation and determination of mannitol and sorbitol in sugarless chewing gums. The 2 isomers are extracted into water, using a 2-phase system to facilitate dissolution of the chewing gum. The aqueous phase is filtered through a 0.45 μm pore membrane filter and injected into the liquid chromatograph. The mannitol and sorbitol are eluted from an Aminex Q-15S cation exchange resin with water as the mobile phase and are quantitated by using a differential refractive index detector. Average recoveries for mannitol and sorbitol are 98.9 and 99.2%, respectively.
Systematic Approach to the Detection of Explosive Residues. V. Black Powders
Authors: Washington Willard D , Kopec Robert J , Midkiff Charles R
Published: February 2020

Part V of the series describes tests for the detection and identification of black powder explosives residues in post-blast debris. Standard and modified formulations of commercial or custom origin can be distinguished. Different tests used in characterizing black powder residues are microscopy, ignition characteristics, spot chemical tests, IR spectroscopy, thin layer chromatography, x-ray diffraction, and scanning electron microscopy with energy dispersive x-ray spectroscopy.
Radionuclides in Foods
Authors: Simpson Robert E , Baratta Edmond J , Jelinek Charles F
Published: February 2020

The results are summarized of the analysis for strontium-90, cesium-137, iodine-131, ruthenium-106, and potassium-40, a naturally occurring radionuclide, in samples of total diet and selected import commodities in the foods compliance program of the Food and Drug Administration. On the basis of the radionuclide intake guidelines established by the Federal Radiation Council (FRC), the low content of radionuclides found in the total diet samples for fiscal years 1973 and 1974 demonstrates the need for surveillance only at the present level. The low levels of radionuclides found in a limited number of edible imported commodities indicate that their contribution to the total diet would not increase the levels of these radionuclides above those recommended for only periodic surveillance by the FRC. The potassium levels, determined from potassium-40 activity, found in meats and fish agree with the value for normal muscle tissue for the reference man reported by the International Commission on Radiation Protection. Of the other commodities, nuts contained the highest levels, while sugar, beverages, and processed foods contained the lowest levels of potassium. Although cesium and potassium are chemical analogs with similar metabolic properties, because of their variable content in some leafy samples as a result of surface contamination, a correlation between cesium-137 levels and the cesium-137-to-potassium ratio was inconclusive.
Screening Method for the Detection of Aflatoxins, Ochratoxin, Patulin, Sterigmatocystin, and Zearalenone in Cereals
Authors: Josefsson B G Egon , Möller Tord E
Published: February 2020

A screening method has been developed for the detection of aflatoxins, ochratoxin A, patulin, sterigmatocystin, and zearalenone in cereals. After extraction, the sample is cleaned up by gel filtration. The mycotoxins are separated by thin layer chromatography. The limits of detection are about 5 μg aflatoxins, 10 ochratoxin A, 50 μg patulin, 10 μg sterigmatocystin, and 35 μg zearalenone/kg.
Application of Linear Discriminant Analysis to the Differentiation of Pure Milk from Different Species and Mixtures
Authors: Smeyers-Verbeke Johanna , Massart Désiré L , Coomans Danny
Published: February 2020

Discriminant analysis is used to identify different milk samples on the basis of the gas chromatographic data for fatty acids in 20 samples each of milk fat from cows, sheep, and goats. The method can differentiate mixtures and pure milks with a high degree of correct classifications. A good discrimination can also be obtained by using a reduced set of variables. The method is useful for the interpretation of gas chromatographic data and should allow a higher proportion of correct classifications than is possible by visual inspection of the chromatograms.
Microwave Technique for Rapid Determination of Moisture in Cheese
Authors: Pieper Heinrich , Stuart James A , Renwick William R
Published: February 2020

Microwave drying of cheese permits rapid moisture determinations in 2.25 min. For uniformity, each sample was prepared according to 16.216. A special microwave unit was designed for this experiment which used an internal balance, a re-circulating water system, and a variable power control for adjusting microwave intensity. Approximately 10 g prepared sample was placed on a Pyrex Petri dish and covered with a piece of glass fiber filter paper to prevent spattering. The sample was then placed on the internal balance and exposed to microwave energy for 2.25 min at a power setting of 74 (maximum power is 78). At the end of the test cycle, the result was read directly in per cent moisture. The results obtained by this method compare favorably with existing AOAC methods, with improved repeatability and reproducibility. The method has been adopted as official first action.
Rapid Determination of Alkaline Phosphatase Activity in Cheese
Authors: Kleyn Dick H , Goodman Steven T
Published: February 2020

A visual screening method specifying phenolphthalein monophosphate as the substrate was applied to cheese by analyzing the extract obtained with 7.5% butanol. In the extraction step, all of the alcohol was added at one time, and the mixture was filtered after mixing. Analysis of 10 samples of various types of cheese resulted in data identical to that obtained by the Scharer rapid method. Quantitative data obtained by dialysis of the butanol filtrate and spectrophotometric measurement of the phenolphthalein compared favorably (r = 0.96) with data obtained by the Scharer spectrophotometric method on 13 samples of cheese.