Chemical Analysis Procedures Research Articles

Determination of tibric acid and clofibrate in animal feed, wastewater and hunan urine.

Analytical chemical procedures are described to determine residues of the drugs clofibrate and tibric acid in animal feed, wastewater, and human urine. Clofibrate was extracted from animal feed and human urine with hexane, whereas residues from wastewater were collected on a Sep-PakTM then eluted with methanol for analysis. Clofibrate residues from the feed, wastewater, and urine were analyzed by high-pressure liquid chromatography (HPLC) with minimum detectable levels (MDL) of about 40, 0.5 and 1.0 ppb, respectively. Tibric acid was extracted from animal feed with 90% methanol and 10% 0.1 N NaOH, whereas wastewater and human urine were acidified with 12 N HCl and then extracted with benzene. The MDL for tibric acid in feed by electron capture/gas chromatography (EC/GC) and HPLC were about 40 ppb and 2.0 ppm, respectively. Residues from these extracts that contained more than 5 ppm of tibric acid were analyzed by HPLC, whereas GC was required for levels below 5 ppm. The GC procedures, which required that tibric acid be derivatized (methylated) prior to analysis, had MDL of 0.1 and 1.0 ppb for wastewater and human urine, respectively. Data are also presented concerning partition values, stability of the compounds in animal feed, and recoveries of the compounds from the three substrates.

Trace analysis of sulfamethazine in animal feed, human urine, and wastewater by electron capture gas chromatography.

Sulfamethazine, a widely used antibacterial drug additive in feeds for swine, chickens, and cattle, was scheduled for toxicological evaluation because of potential human health hazards associated with its residues in edible animal tissues. Analytical chemical procedures that would ensure proper concentration, homogeneity, and stability of the drug in dosed feed and its safe usage during the animal studies were prerequisites for such toxicological tests. Electron capture gas chromatographic (EC/GC) methods were therefore devised for the analysis of sulfamethazine residues in animal feed, human urine, and wastewater at levels as low as 100, 10, and 10 ppb, respectively. Sample extracts were cleaned up by using liquid/liquid partitioning, and the extracts were subjected to two derivatizations followed by cleanup on a silica gel column. The derivatizations of sulfamethazine consisted of methylation followed by trifluoroacetylation of the primary amine function. Ancillary data concerning stability of the compound in animal feed, water, and as a dry residue on glass, extraction efficiencies, partition values with various solvents, and the analysis of residues in feed by high pressure liquid chromatography (HPLC) at levels as low as 1.0 ppm are presented.

On the stoichiometry of HgI 2

The occurrence of deviations from stoichiometry of the semi-insulator compound HgI 2 has been established using a very elaborate chemical analytical procedure. It was found that the molar ratio of I 2 Hg varies from 1.993 to 2.015 (±0.002). The deviations from stoichiometry have been corroborated by studying the red to yellow solid state phase transformation temperature. It was found that the compounds, whether rich or poor in iodine, have lower T tr than those closest to stoichiometry, i.e., where the I 2 Hg ratio is 2.000.

Regional haze case studies in the southwestern U.S—I. Aerosol chemical composition

Aerosol chemical composition as a function of particle size was determined in the southwestern U.S.A. during four weeks of sampling in June, July and December, 1979 as a part of project VISITA. Samples were collected at two ground stations about 80 km apart near Page (AZ) and in two aircraft flying throughout the region. Several different size separating aerosol samplers and chemical analysis procedures were intercompared and were used in determining the size distribution and elemental composition of the aerosol. Sulfur was shown to be in the form of water soluable sulfate, highly correlated with ammonium ion, and with an average [NH + 4]/[SO 2− 4] molar ratio of 1.65. During the summer sampling period, three distinct regimes were observed, each with a different aerosol composition. The first, 24 h sampling ending 30 June, was characterized by a higher than average value of light scattering due to particles (b sp) of 24 × 10 −6 m −1 and a fine particulate mass ( M f ) of 8.5 μg m −1. The fine particle aerosol was dominated by sulfate and carbon. Aircraft measurements showed the aerosol was homogeneous throughout the region at that time. The second regime, 5 July, had the highest average b sp of 51 × 10 −6m −1 during the sampling period with M f of 3.2 μgm −3. The fine particle aerosol had nearly equal concentrations of carbon and ammonium sulfate. For all three regimes, enrichment factor analysis indicated fine and coarse particle Cu, Zn, Cl, Br, and Pb and fine particle K were enriched above crustal concentrations relative to Fe, indicating that these elements were present in the aerosol from sources other than wind blown dust. Particle extinction budgets calculated for the three regimes indicated that fine particles contributed most significantly, with carbon and (NH 4) 2SO 4 making the largest contributions. Fine particle crustal elements including Si did not contribute significantly to the extinction budget during this study. The December sampling was characterized by very light fine particle loading with two regimes identified. One regime had higher fine mass and sulfate concentrations while the other had low values for all species measured.

Control of Test Substances

The efficient control of chemicals during a nonclinical laboratory study is of the utmost importance from three main points of view: (1) integrity of the experiment, (2) safety of personnel, and (3) protection of the environment. While the general principles involved in chemical control may be set forth in formal GLPs, detailed problems concerning individual test substances can only be resolved by utilizing the competency and judgment of a researcher who possesses adequate analytical chemical methods. Integrity of an experiment requires knowledge of the identity, purity, and stability of the test substance, as well as its proper handling and storage and a knowledge of its chemical properties. Assurance of homogeneity, stability, and proper concentration of the chemical in the dosage form is also of primary importance. The development and use of adequate analytical chemical procedures for determining the test agent in human samples, air, clothing, and on work surfaces is necessary for the initiation of surveillance procedures to assure safety of personnel from exposure to the test substances. The environment must be protected from hazardous test substances by using adequate disposal techniques for the chemical and all contaminated materials. This usually involves development of wastewater cleanup systems and continuous monitoring of the effluent to prevent discharge of hazardous substances. Incineration is the most useful method for disposal of solids and highly contaminated liquids. Work from our laboratory, done during the past 5 years, provides an illustration of the important principles, problems, and pitfalls encountered in chemical control.

A new procedure for the wet chemical analysis of the lead—noble metals button

Thiobarbituric acid can be used as a group precipitant for the recovery of Pt, Pd, Rh and Au from the lead perchlorate—perchloric acid solution, obtained after the lead—noble metals button has been parted with perchloric acid. By integration of this procedure with the recovery of Ir, Ru and Os from the parting residue, a scheme is evolved which makes possible the determination of all the platinum metals and gold from a single button. The results of analyses of various platiniferous materials by the proposed lead—wet method and the classical lead-cupellation method are compared.

An application of pert to R & D scheduling

This paper deals with an application of PERT to R & D scheduling for the National Center for Drug Analysis, U. S. Food and Drug Administration. The Center is a pharmaceutical-chemistry laboratory having specialized functional responsibilities for research and development of analytical chemical procedures. The model was constructed based on the empirical data obtained at the Center for a five-year period. The model has been statistically tested and interpreted. It assists the management of the Center in developing a complete work-planning process and in controlling the project tasks, thus achieving the effective utilization of human and physical resources.

Automated Hydrolysis of Nonreducing Sugars and Fructosans from Plant Tissue1

Analytical procedures for chemical analysis of carbohydrates by measuring reducing power before and after hydrolysis, have been automated once the carbohydrates have been removed from the plant tissue. Sugars and fructosans were removed from forage tissue by hot water treatment. Reducing sugars in an aliquot were assayed by automated procedures without acid hydrolysis. Total water‐soluble carbohydrates were measured with automated acid hydrolysis of the same aliquot. Nonreducing carbohydrates were calculated as the difference between total water‐soluble carbohydrates and reducing sugars. Sucrose and fructosan were completely hydrolyzed during the 2 min. exposure to 0.2 N acid at 95 C that were the conditions in automated hydrolysis. However, starch, if present in the water solution, was not broken down by the automated hydrolysis procedure due to low acid concentration and short duration of exposure to heat.Automated procedures increased lab efficiency, reduced routine errors, and eliminated filtration, pipetting, and manual dilution often required by most procedures.

Continuous titrations in ultramicrodeterminations

Problems in scaling-down procedures of chemical analysis are generally stated. Titrations are to be preferred over single measurements. Continuous titration in a titration system may help in solving the stated problems. Detection is easy and may be done by simple electrodes. Illustrations from the authors' practice are given.

Rapid biological and chemical analyses of bacterial endotoxins separated by preparative thin-layer chromatography

Methods have been elaborated for rapid location of biologically active bacterial endotoxin components on preparative thin-layer chromatography (tlc) by Limulus lysate clotting assay. The separation of the components from silicic acid is not necessary. Further assays were established for the semiquantitative estimation of endotoxic activites (Shwartzman reactivity, chick embryo lethality, and non-specific tumor resistance enhancement) without complete removal of silicic acid. Quantitative chemical analytical procedures were also elaborated to determine the molar ratios of the biologically active components separated and detected in the above tlc system. These included phosphorus, hexosamine, heptose, 2-keto-3-deoxyoctonate, and long-chain carboxylic acid content measurements. Here again, the chemical determinations were carried out in the presence of silicic acid.

Simulation of the Dynamics of Machinery

The dynamics of motion of general, two-dimensional machine systems incorporating linkage elements is studied by a procedure which eliminates equation writing. The method is similar to chemical engineering process analysis procedures utilizing an interconnection matrix to describe attachments between components of a system. A digital computer program based on the procedure, termed the Machine Dynamics-Universal System Analyzer (MEDUSA), has been written and tested. This program contains subroutines for simulating the behavior of the following standard components: rigid links, torsional and linear springs, torsional and linear dashpots, force sources, motion generators, and flexible beams. Gears, chain drives, hydraulic transmissions, electric motors, and other components may be added to the simulation without difficulty. To use the program, the engineer follows a standard method to develop a special subroutine calling various component subroutines in proper order. The program computes the accelerations at the centers of mass of the various rigid elements and the interconnection forces simultaneously. Numerical integration alternating with the acceleration computation determines the position and force history of the machine. Experience shows that the engineering effort needed to develop a dynamic simulation of a general machine system using MEDUSA is greatly reduced compared to deriving the equations of motion.

Amino-acid sequence of porcine pancreatic elastase and its homologies with other serine proteinases.

The primary structure of porcine elastase has been determined by classical procedures of enzymatic digestion and chemical sequence analysis and shown to be closely related to those of chymotrypsins A and B and trypsin. Differences in side-chains offer an explanation of the differences in substrate specificity.

The ultrastructures of autotrophically and heterotrophically grown Thiobacillus novellus.

Studies of heterotrophically and autotrophically grown Thiobacillus novellas (A.T.C.C. 8093) showed several differences in cell structure. The envelope of the heterotrophically grown cell appeared as a homogeneous three-layered structure. The envelope of the autotrophically grown cell under the same fixing and staining procedure also appeared as a three-layered structure; however, differences were evident in the outermost layer of the two envelopes. Chemical analysis and specific staining procedures suggested that globules present in the heterotrophic cells were made up of polysaccharide.

Concepts in developing in-process calutron controls

Methods of identifying problems occurring in the various steps of the electromagnetic separation of isotopes at the Oak Ridge National Laboratory (ORNL) have been developed. Most variations in isotopic purity can be traced to separator (calutron) performance, with only minor variations in purity introduced by chemical or mass analysis procedures. The contamination approach used to evaluate and interpret routine and experimental results has been programmed for use in computers. The knowledge of calutron behavior gained in this manner has been applied in efforts to improve the separation process and minimize the number of mass assays required. Experimental work toward stabilizing ion beams is described; however, the improved stability appears to be of value only in separating isotopes of the heavy elements. Simple techniques for detecting charge exchange, for studying changes in contaminating ion currents produced by experimental modifications and for evaluating charge recovery processes are described.

PRESSOR SUBSTANCES IN ARTERIAL HYPERTENSION

Some pharmacological and chemical qualities of pherentasin, a vasoconstrictor substance procured from human hypertensive blood, were studied by a new assay method using the spirally cut rabbit aorta. Of a number of drugs tested, six metal-binding agents including hydralazine inactivated the active principle. The material was stable in acid but not in alkali. It was destroyed by drying. Chemical analysis and inactivation procedures suggested the presence of primary amine and considerable sulfur; a peptide linkage was suspected because of inactivation by manganous ion and papain. The material was remarkably resistant to most pharmacological agents and appeared to act directly on smooth muscle.

Simultaneous Spectrophotometric Determination of Pyrilamine Maleate and Quinine

The inclusion of the recently developed antihistamines in cold tablets has led to the interesting problem of quantitatively estimating constituents which have very similar chemical and physical properties. Formulations have appeared containing aspirin, caffeine, phenacetin, and quinine hydrobromide in combination with the well established antihistaminic, Pyrilamine Maleate. The pyrilamine maleate (pyranisamine maleate) and quinine in such combinations pose a difficult problem in separation and estimation. Pyrilamine maleate has the empirical formula C17H23N3OC4H4O4, is very soluble in chloroform and water, freely soluble in alcohol and slightly soluble in benzene and ether. In alkaline solution the free base is liberated. Most of the chemical reactions for its determination or separation from other constituents make use of the one tertiary amine type nitrogen contained in the molecule. Quinine hydrobromide is, of course, one of the well known alkaloid by addition of ammonia followed by the extraction of the free alkaloid with chloroform. Under such conditions, pyrilamine base will be extracted along with the alkaloid. Thus, it is quite impractical to attempt a chemical separation of these constituents from a mixture containing both. The actual deter mination of one in the presence of the other is not possible by the chemical analytical procedures usually used. However, their resolution by ultraviolet spectrophotometric means is a relatively simple matter.

SHORT METHODS FOR CHEMICAL ANALYSIS OF GLASS*

AbstractAnalytical methods have been developed which shorten the time required for the determination of many of the constituents found in glass. These short methods have been worked into a procedure for the routine chemical analysis of container and sheet glasses.The determination of SiO2, BaO, SO3, R2O3, CaO, MgO, B2O3, Na2O, and K2O percentages on several samples can be made in a single day. Most of the experimental work has been done on Bureau of Standards glass No. 128, but results from several other glasses are included. Particular care has been taken to discover interfering substances and to eliminate errors from this source. The accuracy is comparable with that obtained from the use of umpire methods.