Energetics and kinetics of various cyano radical hydrogen abstractions

The cyano radical (CN) is an abundant, open-shell molecule found in a variety of environments, including the atmosphere, the interstellar medium and combustion processes. In these environments, it often reacts with small, closed-shell molecules via hydrogen abstraction. Both carbon and nitrogen atoms of the cyano radical are reactive sites, however the carbon is more reactive with reaction barrier heights generally between 2-15 kcal mol^-1 lower than those of the analogous nitrogen. The CN + HX → HCN/HNC + X, with X = H, CH₃, NH₂, OH, F, SiH₃, PH₂, SH, Cl, C₂H, CN reactions have been studied at a high-level of theory, including CCSD(T)-F12a. Furthermore, kinetics were obtained over the 100-1000 K temperature range, showing excellent agreement with those rate constants that have been determined experimentally.

Dibridged, Monobridged, Vinylidene-Like, and Linear Structures for the Alkaline Earth Dihydrides Be2H2, Mg2H2, Ca2H2, Sr2H2, and Ba2H2. Proposals for Observations

This research reports a search for peculiar monobridged structures of the E₂H₂ molecules (E = Be, Mg, Ca, Sr, Ba). For Be₂H₂ and Mg₂H₂, the monobridged geometry is not an equilibrium but rather a transition state between the vinylidene-like structure and the global minimum HE-EH linear geometry. However, for Ca₂H₂, Sr₂H₂, and Ba₂H₂, this situation changes significantly; the linear structure is no longer the global minimum but lies higher in energy than two other equilibria, the dibridged and monobridged structures. The planar dibridged structures of both Sr₂H₂ and Ba₂H₂ should be observable via IR spectroscopy. Although the remarkable monobridged structures lie 8.3 (Sr) and 7.6 kcal/mol (Ba) higher, the large IR intensities of the terminal E-H stretching frequencies may make the monobridged structures observable. The monobridged structures have sizable permanent dipole moments (3.07 and 3.06 D for Sr and Ba, respectively) and also should be observable via microwave spectroscopy.

Use of Dexsil 300 on a Specially Washed Chromosorb W for Multicomponent Residue Determinations of Phosphorus- and Sulfur-Containing Pesticides by Flame Photometric GLC

A column containing the thermally stable liquid phase Dexsil® 300 on Chromosorb W specially washed with HC1 was found well suited for the multicomponent residue analysis of foods for phosphorus- and sulfur-containing pesticides by GLC with flame photometric detection and temperature programming. Interference accumulating on the column from analyses of large samples subjected to minimum cleanup was removed by replacing a short plug of glass wool and packing at the head of the column and purging the remaining packing with carrier gas at 400°C for 1 hr. Silicone O-rings for sealing the glass columns were replaced by asbestos-Dexsil 300 gaskets to permit operation at 400°C. Retention times relative to parathion of 146 pesticides containing phosphorus and/or sulfur are reported; they are similar to those obtained on a column of OV-101 on Gas-Chrom Q. Performance of the new column packing was illustrated by an analysis of milk for 10 organophosphorus pesticides. Recoveries of the pesticides at levels of 0.25-0.01 ppm were 73-98%. The specially washed support was superior to 2 others tried with Dexsil 300 because less conditioning of the packing was required, the resolution and response were improved, and decomposition of Dyfonate was avoided.

Convergent energies and anharmonic vibrational spectra of Ca2H2 and Ca2H4 constitutional isomers

Three constitutional isomers of both Ca₂H₂ and Ca₂H₄ have been characterized with molecular electronic structure theory. Correlation methods as complete as CCSDT(Q) and basis sets as large as cc-pwCV5Z have been used to converge the relative energies within chemical accuracy (≤1 kcal mol^-1). Anharmonic vibrational frequencies were computed using second-order vibrational perturbation theory employing CCSD(T)/cc-pwCVTZ cubic and quartic force-fields and a CCSD(T)/cc-pwCVQZ quadratic force field. The monobridged [Ca(μ₂-H)CaH] and dibridged [Ca(μ₂-H)₂Ca] isomers of Ca₂H₂ were predicted to lie 6.5 and 12.9 kcal mol^-1 below the energy of the classical HCaCaH linear isomer, respectively. Despite the energetic favorability of the bridged Ca₂H₂ isomers, we conclude (surprisingly) that only the higher energy linear structure has been observed in the laboratory. At 0 K, the tribridged [Ca(μ₂-H)₃CaH] isomer of Ca₂H₄ is predicted to be enthalpically favored by 0.9 kcal mol^-1 in comparison to the enthalpy of the dibridged [HCa(μ₂-H)₂CaH] structure. Comparison of experiment with our computed frequencies suggests that the observed vibrational features arise from both the dibridged and the tribridged Ca₂H₄ structures.

Mechanisms of the Ethynyl Radical Reaction with Molecular Oxygen

The ethynyl radical, ^•C₂H, is a key intermediate in the combustion of various alkynes. Once produced, the ethynyl radical will rapidly react with molecular oxygen to produce a variety of products. This research presents the first comprehensive high level theoretical study of the reaction of the ^•C₂H (²Σ⁺) radical with molecular oxygen (³Σ_g^-). Correlation methods as complete as CCSDT(Q) were used; basis sets as large as cc-pV6Z were adopted. Focal point analysis was employed to approach relative energies within the bounds of chemical accuracy (≤1 kcal mol^-1). Two dominate reaction pathways from the ethynyl peroxy radical include oxygen-oxygen cleavage from the ethynyl peroxy radical that is initially formed to produce HCCO (²A″) and O (³P) and an isomerization of the ethynyl peroxy radical to eventually yield HCO (²A') and CO (¹Σ⁺). The branching ratio between these two competitive reaction pathways was determined to be 1:1 at 298 K. Minor reaction pathways leading to the production of CO₂ (¹Σ_g⁺) and CH (²Π, ⁴Σ^-, ²Δ) were also characterized. The absence of CCO (³Σ^-) and OH (²Π) was explained in terms competition with more accessible reaction pathways.

Role of primary constitutive phosphorylation of Sendai virus P and V proteins in viral replication and pathogenesis

Functional analysis of the primary constitutive phosphorylation of Sendai virus P and V proteins was performed using both in vitro and in vivo systems. Sendai virus minigenome transcription and replication in transfected cells were not significantly affected in the presence of primary phosphorylation deficient P protein (S249A, S249D, P250A) as measured by either the luciferase activity or the Northern blot analysis. Similarly, recombinant Sendai viruses lacking the primary phosphorylation in P grew to titers close to the wild-type virus in cell cultures and in the natural host of Sendai virus, the mouse. Mutant viruses showed no altered pathogenesis in mice lungs. Oligomerization of P by binding WT P or mutant P to GST-P (WT) Sepharose beads revealed that the primary phosphorylation was not crucial for P protein oligomerization. Similar to P protein primary phosphorylation, the V protein primary phosphorylation at serine249 was not essential for minigenome transcription and replication, as both WT and mutant V proteins were found equally inhibitory to the minigenome replication. These results show that the primary phosphorylation of P protein has no essential role in Sendai virus transcription, replication, and pathogenesis.

Dissection of individual functions of the Sendai virus phosphoprotein in transcription

The Sendai virus P protein is an essential component of the viral RNA polymerase (P-L complex) required for RNA synthesis. To identify amino acids important for P-L binding, site-directed mutagenesis of the P gene changed 17 charged amino acids, singly or in groups, and two serines to alanine within the L binding domain from amino acids 408 to 479. Each of the 10 mutants was wild type for P-L and P-P protein interactions and for binding of the P-L complex to the nucleocapsid template, yet six showed a significant inhibition of in vitro mRNA and leader RNA synthesis. To determine if binding was instead hydrophobic in nature, five conserved hydrophobic amino acids in this region were also mutated. Each of these P mutants also retained the ability to bind to L, to itself, and to the template, but two gave a severe decrease in mRNA and leader RNA synthesis. Since all of the mutants still bound L, the data suggest that L binding occurs on a surface of P with a complex tertiary structure. Wild-type biological activity could be restored for defective polymerase complexes containing two P mutants by the addition of wild-type P protein alone, while the activity of two others could not be rescued. Gradient sedimentation analyses showed that rescue was not due to exchange of the wild-type and mutant P proteins within the P-L complex. Mutants which gave a defective RNA synthesis phenotype and could not be rescued by P establish an as-yet-unknown role for P within the polymerase complex, while the mutants which could be rescued define regions required for a P protein function independent of polymerase function.

Inter-observer variability at laparoscopic assessment of pelvic adhesions

A total of 25 women undergoing videolaparoscopy and a dye test to investigate pelvic adhesions and infertility were evaluated to determine whether applying a score system to pelvic adhesions was reproducible, and its place in determining prognosis or management. The surgeon performing the laparoscopies scored each case using the American Fertility Society (AFS) system, gave an estimate of the likely prognosis from microsurgery and recorded a recommended management [surgery or in-vitro fertilization (IVF)]. The video images and histories were independently reviewed by two other surgeons experienced in tubal surgery, who also scored each case and recorded prognosis from surgery and recommended management. Several differences in adhesion scores for each case were noted. Agreement was present between surgeons regarding estimated prognosis for microsurgery and also in recommending management, particularly when prognosis was considered poor and IVF was recommended. Despite some reproducibility, the AFS score system did not predict outcome or management decisions. However, the surgeons' fundamental impression of the state of the pelvis and recommendation for either surgery or IVF were more consistent and reproducible. Any future proposed system for adhesion classification will need to account for, and be predictive of, the decreasing number of patients for whom surgery (rather than IVF) is the preferred management.

Comparison of fallopian tube intraluminal pathology as assessed by salpingoscopy with pelvic adhesions

OBJECTIVE

To correlate the severity and extent of pelvic adhesions, as noted at laparotomy for microsurgery, with the presence and extent of fallopian tube intraluminal pathology, as noted using salpingoscopy.

DESIGN

Prospective clinical study.

SETTING

A university teaching hospital.

PATIENTS

Twenty patients presenting for pelvic microsurgery between July 1992 and January 1993.

INTERVENTIONS

Salpingoscopy was performed at the time of microsurgery and intraluminal pathology was scored. An objective assessment of the extent of pelvic adhesions was made using standardized adhesion score systems.

RESULTS

There was a strong correlation between the degree of intratubal damage and the extent of pelvic adhesions when the etiology was previous pelvic inflammatory disease (PID) but not when the underlying etiology was endometriosis. However, in the endometriosis subgroup, intraluminal ampullary pathology was noted in 27% of tubes assessed, and intraluminal fimbrial pathology was noted in 36% of tubes assessed. Intraluminal tubal pathology also was noted in a number of cases where the underlying etiology was previous surgery for benign disease.

CONCLUSIONS

This study confirms previous reports that, in cases of PID leading to adhesions, there is a high incidence of intraluminal pathology. However, this study also demonstrates that intraluminal pathology is often associated with adhesions arising from other etiologic groups, suggesting that intraluminal assessment is required for all patients in whom adhesiolysis for fertility is considered.

Community attitudes to maternal age and pregnancy after assisted reproductive technology: too old at 50 years?

Community attitudes toward oocyte and embryo donation, and toward assisted reproduction after the menopause were assessed in this survey of 1131 Australians. Of the respondents, 64.2% believed that oocyte or embryo donation was an acceptable treatment for infertile couples, 54.6% felt that it was acceptable for a woman to have her own embryos transferred after the menopause, and 37.9% are accepting of the donation of eggs or embryos to post-menopausal women. There were no significant differences in response amongst different religious groups, or in relation to gender or income level. Significantly higher levels of acceptance were noted for all categories amongst those respondents aged < 35 years. Despite the established clinical ability to achieve pregnancy in the over 50 years age group, this survey reveals only minority community support for this practice. However, public opinion may alter in the future if the attitudes of the younger proportion of the sample are maintained.

Investigation of impaired ovarian function as a contributing factor to infertility in women with pelvic adhesions

A prospective study was performed to determine whether a relationship exists between infertility as a result of pelvic adhesions, and raised follicle stimulating hormone (FSH). A total of 66 patients, who had a diagnostic laparoscopy and dye performed as part of their infertility work-up, had an early cycle serum FSH drawn one to two cycles after this procedure. Patients were divided into two groups, one with pelvic adhesions as a result of surgery, infection or endometriosis, and a control group consisting of those with a normal pelvis at laparoscopy or with minimal/mild endometriosis without adhesions. In the adhesion group, a correlation was noted between American Fertility Society (AFS) adhesion score and basal FSH concentration, although all FSH values for this group were within the normal range. This study suggests a correlation between pelvic adhesions and ovarian compromise, but a larger study involving more severe cases of adhesions is required to determine whether this finding is of clinical importance.

A comparison of early pregnancy failure and ongoing pregnancy rates between fresh and frozen embryo transfer following in vitro fertilization

In order to compare pregnancy outcomes following fresh and frozen embryo transfer after in vitro fertilization (IVF), a retrospective analysis of data from the Royal North Shore IVF Programme was performed. Six hundred and sixty seven embryo transfers following routine IVF were performed during 1991 and 1992. Four hundred and twenty fresh embryo transfers were performed during that period, resulting in a clinical pregnancy rate of 21%. In comparison, 247 frozen transfers, where the initial procedure was routine IVF, were performed, resulting in a clinical pregnancy rate of 16.6%. This difference was not significant. When varying numbers of transferred embryos in the 2 groups were taken into account, there was a significant difference in the proportion of ongoing viable fetuses per embryo returned for 1991, but not for 1992. Although there were a greater number of abortions and ectopic pregnancies in the fresh transfer group, these differences did not achieve statistical significance. The implications of improving results from frozen embryo transfer are discussed.

Vergence orthoptics: validity and persistence of the training effect

The validity and permanence of orthoptic treatment for vergence deficiencies requires investigation due to the subjective nature of determining success in most clinical cases, i.e., the amelioration of symptoms and increases in vergence ranges. The relation between Risley prism vergences, a subjective measure, and vergence tracking rate, an objective index, is investigated. The course of orthoptics progress is compared in cases of clinical vergence dysfunction. Vergence-deficient control subjects showed no significant change in either index. However, trained subjects demonstrated rapid increases in both indices. The persistence of the training effect was monitored for up to 9 months. No regression was observed in subjects who met all release criteria, but one subject who chose to terminate therapy early showed a slow regression in tracking rate and recurrence of symptoms. These data support the validity of vergence training and increase the plausibility of previous clinical reports of orthoptics success.

Chromatographic assays for traces of potentially carcinogenic metabolites of two azo dyes, Direct Red 2 and Direct Blue 15, in rat, hamster and human urine

Specific, precise and sensitive methods are described for determining traces of potentially carcinogenic metabolites of Direct Red 2 and Direct Blue 15 in rat and hamster urine and to monitor the urine from workers who may be occupationally exposed to these dyes. This methodology is generally applicable to metabolites of azo dyes based on benzidine or three of its congeners. The benzidine-congener free amines, their mono and diacetylated analogs and alkaline hydrolyzable conjugates were determined after appropriate extraction and hydrolysis by HPLC or EC/GC. Residues of metabolites in rat, hamster, and human urine were determined at levels as low as 1 ppb. Supplementary information is also presented concerning hydrolysis of diacetylated metabolites and the stability of Direct Red 2 and Direct Blue 15 in rat, hamster and human urine.

Metabolism of a dimethylbenzidine-based dye in rats and hamsters as determined by analysis of the urine for potentially carcinogenic aromatic amines

Direct Red 2 was given as an aqueous solution to rats and hamsters to determine whether the dye is cleaved to potentially carcinogenic aromatic amines. Sensitive and specific assays of the urine from treated animals by EC/GC revealed appreciable levels of 3,3'-dimethylbenzidine, mono- and di-acetyldimethylbenzidine, and alkaline hydrolyzable conjugates. Peak concentrations of the metabolites in urine occurred 12 to 24 hours after administration to rats, and within 12 hours in hamsters. The levels of all metabolites and conjugates diminished rapidly in both species after peak concentrations were reached, with no residues detected after 96 hours. The results conclusively demonstrated in vivo cleavage of the dye in both species, and it is proposed that the analytical methods employed can be used for chemical monitoring of human urine.

Metabolism of nine benzidine-congener-based azo dyes in rats based on gas chromatographic assays of the urine for potentially carcinogenic metabolites

Metabolism experiments were conducted with rats dosed with nine azo dyes based on dimethyl-, dimethoxy-, or dichlorobenzidine to determine whether the free amine congeners, their monoacetyl or diacetyl metabolites, or alkaline hydrolyzable conjugates were excreted in the urine. After preliminary tests of the dyes, 2-mg doses were administered to each animal and urine samples were collected at intervals up to 96 hours. EC/GC procedures were based on the analysis of heptafluorobutyryl derivatives of the free amine congener moieties or their monoacetyl metabolites. Peak levels of metabolites were excreted either 0-12 or 12-24 hours after administration and, in seven of nine instances, no metabolites persisted in the urine after 48 hours. Minimum detectable levels of all metabolites were 12 ppb or less. All nine dyes were shown to be converted to measurable levels of their benzidine-congener-based metabolites in rats.

A rapid procedure to efficiently clean blenders repeatedly used to prepare dosed feed for bioassays

An effective and economical procedure is described to clean blending equipment repeatedly used to prepare dosed feed for animal bioassays. The cleanup procedure was evaluated with 2 types of blenders against 10 test chemicals with a broad spectrum of polarities by separately spiking the agents into feed at various levels. Analytical data illustrating the level of contamination at each interval of the multi-step cleanup procedure are presented for each test chemical. Analytical chemical methods and efficiencies of the cleaning steps with the feed admixtures are discussed. The procedure was tested and adopted for use at the National Center for Toxicological Research (NCTR).

Trace analysis of doxylamine succinate in animal feed, human, urine, and wastewater by GC using a rubidium-sensitized nitrogen detector

Doxylamine succinate, a drug used as a sleep-inducing agent, an antihistamine, and in a therapeutic formulation taken by pregnant women as an antinauseant, was scheduled for toxicological evaluation as part of a structure activity relationship study, with rats and mice, because a deficiency of such data exists with regard to many antihistamines. Analytical chemical procedures that ensure proper concentration, homogeneity, and stability of the drug in dosed feed, as well as the safety of personnel and the environment, were prerequisites for the toxicological tests. GC methods using a rubidium-sensitized nitrogen detector were developed for analysis of doxylamine succinate in animal feed, human urine, and wastewater at levels as low as 1 ppm, 100 ppb, and 100 ppb, respectively. Sample extracts were cleaned up by liquid-liquid partitioning, followed by additional cleanup on a column of silica gel. Data are presented concerning the stability of the drug in animal feed, extraction efficiencies, and the use of the silica gel cleanup column to separate the caffeine interference from doxylamine in extracts of human urine. Partition values and ancillary data concerning analysis of the drug in feed, by HPLC at levels as low as 10 ppm, are also reported.

Benzidine-congener-based azo dyes: assays for purity and residues in feces from dosed rats

Analytical methods were required to determine purities of benzidine-congener-based azo dyes and residues of the intact dyes in feces from rats before valid metabolism studies of such compounds could be conducted. A procedure is described for purity assays based on reduction of the dyes with stannous chloride followed by gas chromatography of the released free amine. Sixteen different samples of commercial dyes based on three benzidine congeners were assayed; purities ranged from 26.4 to 83.4%. Several dyes were also shown to be partially purified by cold water washes. A method to determine two intact dyes in feces from dosed rats, which consisted of extraction with dimethylformamide: water, clean-up by a rapid procedure using an octadecylsilane column, and quantification by ion-pair high-pressure liquid chromatography (HPLC) is reported. minimum detectable levels of both dyes in feces are 0.2 ppm. Excretion profiles based on parallel HPLC and radioassays of feces from rats dosed with 14C-labeled Direct Blue 15 and Direct Red 2 are presented. Based on radioassays, about 74% of each dose was excreted via the feces; however, HPLC assays showed that only about 11% of each dose was present as intact dye in the excrement.

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.

Metabolism and distribution of two 14C-benzidine-congener-based dyes in rats as determined by GC, HPLC, and radioassays

Absorption, metabolism and tissue distribution studies were conducted in the rat with 14C-biphenyl ring-labeled Direct Blue 15, a 3,3'-dimethoxybenzidine (DiMxBzd) based azo dye; Direct Red 2, based on 3,3'-dimethylbenzidine (DiMeBzd) and corresponding benzidine congener amines. Single oral doses of the 14C-labeled dyes (12 mg/kg, 62 microCi/kg) and molar equivalent doses of the respective amines were administered and urine and fecal samples collected at intervals up to 192 hours. Urine specimens were analyzed for 14C content and further characterized by EC/GC for free amines, acetylated metabolites, and conjugates. Feces were assayed for 14C content and for unchanged dosed dyes or amines by HPLC. A comparison of the metabolism of Direct Blue 15 with its base DiMxBzd, indicated that the base was more extensively metabolized and that most of the 14C in various extracts was identified as known metabolites. The metabolism of Direct Red 2 compared with its base, DiMeBzd, indicated that the base was more extensively metabolized, yet only a small percentage of the 14C in extracts was identified as known metabolites. Most of the 14C present in the urine could not be extracted with benzene nor chloroform, indicating high polarity. Distribution studies conducted with both dyes showed that liver, kidney, and lung accumulated and retained higher levels of 14C than other tissues (at 72 hrs). Peak levels of 14C, which occurred 8-12 hours after dosing, were significantly higher with Direct Red 2 than Direct Blue 15. Tissue distribution data (72 hr) for rats dosed with the free amines compared with the dyes showed a generally lower but similar distribution pattern.

A "marker" technique to monitor treated industrial wastewater effluents

In toxicological research with hazardous substances (e.g. carcinogens), wastewater effluent from the test facility must be free of such substances before discharge into the environment. An industrial wastewater processing employing adsorbers of carbon and XAD-2 resin is described; however, chemical assays of each batch of treated effluent must certify the absence of all test agents. Elution profiles and adsorption isotherm tests with the test agents vs. the two adsorbents provided the basis for a "marker" technique which should eliminate the necessity to assay for all test agents in each batch of processed effluent. A radionale is presented for periodic introduction of a "marker" (gentian violet) into the primary adsorbers. If detected in the effluent, the "marker", which elutes from the adsorbers before most of the test agents would signal impending depletion of the adsorbent which could then be replaced. Recommendations to modify the industrial wastewater treatment plant and to implement the "marker" technique are presented as cost-effective alternatives to extensive and laborious chemical assays.

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.

Chemical monitoring of urine from workers potentially exposed to benzidine-derived azo dyes

Benzidine (Bzd) and monoacetylbenzidine (MoAcBzd) were found in the urine of workers exposed to benzidine-based azo dyes. A colorimetric screening method, based on the reaction of extracted free aromatic amines with 2,4,6-trinitrobenzene-sulfonic acid (TNBS), was used with a specific electron-capture gas chromatographic (EC-GC) method. Alkaline hydrolyzable conjugates of Bzd and 2,4-diaminoazobenzene (DiAmAzBz) were found together with free DiAmAzBz and traces of 3,3'-dimethylbenzidine (DiMeBzd) and 3,3'-dimethoxybenzidine (DiMxBzd). The presence of a known human bladder carcinogen (Bzd) and its metabolites in the urine of workers exposed to benzidine-based azo dyes is a cause for concern.

Determination of gentian violet in animal feed, human urine, and wastewater by high pressure liquid chromatography

Sensitive and specific procedures are described for the analysis of residues of gentian violet in animal feed, human urine, and wastewater at levels of 1000 ppm down to 10 ppb, 1 ppb, and 10 ppb, respectively. The cleaned-up extracts were analyzed by reverse-phase high pressure liquid chromatography by using an absorption detector at 588 nm. Recoveries of the compound from animal feed, human urine, and wastewater at the 10 ppb level were 79%, 58%, and 60%, respectively. Information concerning the stability of the compound in animal feed and the efficiency of extracting the residues is presented. Ancillary information is also reported concerning the separation and analysis of six related triphenylmethane dyes.

Analysis, purification and stability: requirements for a metabolism study of an azo dye and pigment

Impurities of aromatic amines in the azo dye and pigment, Direct Black 38 and Pigment Yellow 12, and in vitro stability of the dye were determined. These factors can affect the results of studies designed to ascertain whether the two compounds are metabolized to potential carcinogens in hamsters. Procedures for removing impurities from the two compounds are also presented. Electron-capture gas chromatography of the heptafluorobutyryl derivatives of the impurities and degradation products was used to satisfy all the analytical requirements of the experiments. Major impurities found in Direct Black 28 were benzidine, 4-aminobiphenyl and 2,4-diaminoazobenzene; whereas, only 3,3'-dichlorobenzidine was found in Pigment Yellow 12. Stability studies of the purified dye conducted in water and in urine from hamsters and humans indicated that the dye would not degrade under the conditions used for collecting and assaying samples from a metabolism experiment. However, within 48 hours at 25 and 37.5 degrees C, the dye did degrade to known carcinogens in both hamster and human urine. Such degradation not only points out the need for proper storage of samples from metabolism studies but suggests that industrial effluents containing the dye should be properly treated before release into the environment.

Trace analysis of potentially carcinogenic metabolites of an azo dye and pigment in hamster and human urine as determined by two chromatographic procedures

Analytical chemical procedures are described for determining traces of possible metabolites of two azo compounds. Direct Black 38 and Pigment Yellow 12, in hamster urine and to monitor the urine from workers who may be occupationally exposed during the manufacture or use of the dye and pigment. These methods were required for metabolism studies designed to assess the hazards that may occur if the two compounds are converted by in vivo mechanisms to potential carcinogens. Salient elements of the procedure are: extraction of the free aromatic amines and neutral compounds; alkaline hydrolysis of the aqueous phase and extraction of any hydrolyzed conjugates as free amines, and the analysis of the free amines and acetylated metabolites directly by high pressure liquid chromatography or by electron capture gas chromatography after conversion of the amines to heptafluorobutyryl derivatives. Residues of metabolites in hamster and human urine were determined at levels as low as 1 ppb. Ancillary data concerning hydrolysis of diacetylated metabolites and partition values for possible metabolites in various solvent systems are also presented.

A toxicological risk assessment procedure: a proposal for a surveillance index for hazardous chemicals

Health-oriented government agencies responsible for the protection of the public from possible adverse effects, such as that posed by chemical residues in the food supply, must establish priorities on regulatory action as well as for manpower to conduct monitoring programs. A new procedure entitled Surveillance Index (SI) is presented as a technique to evaluate toxic materials that are potential candidates as residues in food supplies and to assign an index number that identifies a relative hazard to the public among the various residues. The SI numbers can be used as criteria by which chemical residues should be monitored whenever conditions such as time and available resources are limiting factors.

Determination of sodium saccharin in animal feed, wastewater and human urine by high-pressure liquid chromatography

Analytical methods are described for sodium saccharin in animal feed, wastewater and human urine at levels as low as 10, 0.1 and 10 ppm, respectively. Samples of animal feed and wastewater are subjected to liquid-liquid partitioning then the feed is further cleaned up on a column of silica gel prior to analysis by high-pressure liquid chromatography (HPLC) using a paired-ion mobile phase and an ultraviolet detector set at 230 nm. Samples of human urine require a cleanpu on a column of XAD-2 prior to the partitioning and silica gel steps as well as an adjustment in the composition of the mobile phase to quantify saccharin. Data concerning partition values and the stability of sodium saccharin in animal feed are also presented.

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.

Trenbolone acetate and trenbolone: trace analysis in animal chow, wastewater and human urine by high pressure liquid chromatography and electron capture gas chromatography

Analytical methodology is described for determining residues of the synthetic anabolic steroid trenbolone acetate (TBA) and its hydrolysis product trenbolone (TBOH) in admixture in animal chow, human urine, and wastewater. Benzene extracts of the substrates are subjected to liquid-liquid partitioning, further cleanup on a column of silica gel, and direct analysis by high pressure liquid chromotography or derivatization with pentafluoropropionic anhydride and analysis by electron capture gas chromatography. Satisfactory recoveries were obtained with both compounds from all three substrates. Residue levels of TBA and TBOH as low as 0.32 and 0.04 ppm, respectively, could be detected in chow; about 0.6 ppb of each compound could be detected in urine and wastewater. Thin layer chromatographic behavior of the two compounds in 7 solvent systems and other ancillary analytical data are also presented.

High pressure liquid chromatographic determination of rotenone and degradation products in animal chow and tissues

An analytical procedure is described for determining residues of rotenone, rotenolone, dehydrotenone, and rotenone in admixture in animal chow and tissues. The methanol or ethyl ether extracts from samples of chow and tissues, respectively, are subjected to a liquid-liquid partitioning cleanup with hexane-acetonitrile, further cleanup on a column of silica gel, and subsequent analysis by high pressure liquid chromatography using an ultraviolet absorption detector set at 295 nm. Animal chow, mouse fetuses, and gastrointestinal tracts spiked with 0.5 ppm of each compound in admixture yielded average recoveries of 92, 51, and 79%, respectively; minimum quantities of the 4 compounds detectable in the 3 substrates averaged 0.12, 0.04, ajd 0.14 ppm, respectively. Stability studies indicate that rotenone reacts with animal chow with a half-life of 7--8 days and is photodegraded in incandescent light with a half-life of 0.65 day. No transplacental transfer of rotenone or its products was observed in fetuses from mice receiving 7 consecutive daily doses of rotenone at levels up to 25 mg/kg.

Determination of sodium phenobarbital in animal chow by high-pressure liquid chromatography

An analytical procedure is described for determining residues of sodium phenobarbital in animal chow at levels as low as 0.14 ppm. The methanol extract is subjected to a liquid-liquid cleanup at pH 13 and 1, further cleaned up on a silica gel column and assayed by high-pressure liquid chromatography by using an ultraviolet absorption detector at 210 nm. Data concerning extraction efficiency, partition values and stability of the chemical in animal chow are also presented.

Trace analysis of estradiol in animal chow by electron-capture gas chromatography

A gas chromatographic method is described for trace analysis of the natural steroidal hormone estradiol in animal chow at levels as low as 3 ppb. Salient elements of the method include extraction of the estradiol with methanol, an initial clean-up on a column of Sepadex LH-20, liquid-liquid partitioning at pH 14 and 10.2, additional cleanup on a slilica gel column, conversion of the estradiol to the pentafluoropropionly (PFP) derivative and analysis by electron-capture gas chromatography on a column of OV-25. Samples containing less than ppb of estradiol are subjected to further clean-up on silica gel after derivatization and prior to analysis.

Trace analysis of zearalenone and/or zearalanol in animal chow by high pressure liquid chromatography and gas-liquid chromatography

An analytical method is described for determining residues of the estrogens zearalenone and/or zearalanol in animal chow at levels as low as 10 ppb. The chow is extracted with methanol and cleaned up by a 3-step procedure employing a Sephadex LH-20 column, liquid-liquid partitioning at pH 13 and 8.3, and a silica gel column. Residues of the 2 compounds, separated on silica gel, are assayed by using high pressure liquid chromatography with ultraviolet detection. Additional data are also included concerning p-values of the compounds in several solvent systems, Rf values from thin layer chromatography with 9 solvent systems, solubilities in 3 solvents, and a procedure for preparing their pentafluoropropionyl derivatives for analysis by electron capture gas-liquid chromatography.

Trace analysis of diethylstilbestrol [DES] in animal chow by parallel high-speed liquid chromatography, electron-capture gas chromatography, and radioassays

An analytical method is described for determining residues of the synthetic estrogen diethylstilbestrol (DES) in animal chow at levels as low as 1 ppb. A methanol extract of the chow is subjected to a 3-step cleanup procedure including a Sephadex LH-20 column, liquid-liquid partitioning at pH 14 and 10.2, and a silica gel column. Residues of DES in the cleaned-up extract are analyzed directly by high-speed liquid chromatography or derivatized to pentafluoropropionyl-DES and assayed by electron-capture gas chromatography. Tests with 14C-DES were used to develop and validate the procedure. Ancillary data concerning extraction efficiencies of various solvents, comparisons of various derivatizing reagents, rates of trans-cis isomerization in two solvents, P-values of DES in various solvent-systems and thin-layer chromatographic behavior i