Gas Chromotography Research Articles

Attractant volatiles released by female and male Triatoma infestans (Hemiptera: Reduviidae), a vector of chagas disease: chemical analysis and behavioral bioassay.

Volatiles emitted by male and female T infestans before and during copula were collected on Porapak-Q filters, desorbed with dichloromethane, and analyzed by gas chromotography and gas chromatography-mass spectrometry after confirmation of attractiveness in an arena bioassay. Chemical analysis confirmed the presence of (R,S) -2- and 3-methylbutan-1-ol in a 2:1 ratio; short chain acids (ethanoic to nonanoic acid); long chains acids decanoic to (Z)-9-octadecenoic acid; aliphatic aldehydes (hexanal to nonanal), benzaldehyde and dipropylsulphide from insects in copula. Electroantennographic studies conducted with a homologous series of aliphatic aldehydes on female and male T infestans showed that, for a given dose, EAG responses elicited from both sexes increased with increased chain length up to nonanal, after which EAG-activity declined. Attractiveness of non-acidic trace components identified in the volatiles were tested on male and female T. infestans, in an arena bioassay using a video tracking method. Aliphatic C6 to C10 aldehydes were tested: hexanal (1-100 microg) and heptanal (10 microg) were attractive to female T. infestans, high doses of octanal and nonanal (1-100 microg) were Unattractive to male and female T. infestans but low doses of nonanal (0.01-0.1 microg) were attractive to male T infestans. Benzaldehyde was highly attractive to female T. infestans at low doses (0.05- 0.1 microg). 3-methylbutan-1-ol was attractive to male T infestans at high dose (1,000 microg). (S) or (S,R) 2-methyl-butan-1-ol were attractive to males or females (1-1,000 microg). Blends of hexanal and benzaldehyde (20:1 and 40:1) showed an additive effect on attraction compared with hexanal alone, when tested on female T. infestans. The study has demonstrated the presence of a number of electrophysiologically and behaviorally active compounds in volatiles emitted by T. infestans in copula that may have a role in the postulated copulation pheromone.

Improved assay for the quantification of the major urinary metabolite of the isoprostane 15-F 2t-Isoprostane (8-iso-PGF 2α) by a stable isotope dilution mass spectrometric assay

Background: The F 2-isoprostanes (IsoPs) are a series of novel prostaglandin (PG)-like compounds generated from the free radical catalyzed peroxidation of arachidonic acid. One IsoP, 15-F 2t-IsoP (8-iso-PGF 2α), has been shown to be formed in abundance in vivo and to exert potent biological activity. Methods: As a means to assess the endogenous production of this compound, we previously developed a method to quantify the major urinary metabolite of 15-F 2t-IsoP, 2,3-dinor-5,6-dihydro-15-F 2t-IsoP (2,3-dinor-5,6-dihydro-8-iso-PGF 2α, 15-F 2t-IsoP-M ), by gas chromotography (GC)/negative ion chemical ionization mass spectrometry (MS) employing stable isotope dilution methodology. While useful, we found that the assay occasionally suffered from the presence of impurities that co-elute on GC with 15-F 2t-IsoP-M, making the measurement of this compound difficult. We now report a modified assay for the quantification of 15-F 2t-IsoP-M employing GC/MS that alleviates this problem. Results: Precision of the assay is ±7% and the accuracy is 96%. The lower limit of sensitivity is approximately 8 pg. Normal concentrations of this metabolite in urine were found to be 0.46±0.09 ng/mg creatinine (mean±1 S.D.) Urinary excretion of 15-F 2t-IsoP-M is markedly altered in situations associated with increased or decreased oxidant stress in vivo. Conclusions: This assay provided a sensitive and accurate method to assess endogenous IsoP generation and can be used to further explore the role of oxidant injury in human disease.

Nitromusk Compounds in Women with Gynecological and Endocrine Dysfunction

Musk xylene (MX), musk ketone (MK), musk ambrette, musk moskene, and musk tibetene are synthetic fragrances. Between 1994 and 1996 these five nitromusk compounds (NMCs) were tested in the blood of 152 women who consulted the Endocrinological Department of the University Hospital of Obstetrics and Gynecology, Heidelberg, Germany, because of gynecological problems. The testing was conducted by gas chromotography with mass-specific detector and mass spectrometry in a retrospective cross-sectional study. MX was detected in 95% and MK in 85% of the blood samples (>20 ng per liter whole blood). The median concentration of MX was 65.5 ng/L and the maximum level of MX was 1183 ng/L; the corresponding values for MK were respectively 55.5 and 518 ng/L. The other three NMCs were found in only a few patients or not at all. Significant associations between MX and MK concentrations were found in blood and different clinical parameters of the endocrine system. MX and MK may act centrally as a disrupter of the (supra-) hypothalamic–ovarian axis, which may result in a mild ovarian insufficiency. On the basis of our data, a reproductive toxicity and an endocrine effect of NMCs in women cannot be ruled out. Further experimental and clinical studies should be conducted.

Pyrolysis kinetics of waste automobile lubricating oil

The kinetics of waste automobile lubricating oil have been studied experimentally and modeled mathematically. Experiments were carried out in the tubing bomb microreactor at a temperature of 420–440°C and reaction times of 5–50 min. Volatile pyrolysis products were identified and quantitatively determined by gas chromotography. A lump model of combined series and parallel reactions for oil formation is proposed. Conversion data fitted first order kinetics for C 5–C 11 and C 12–C 25. The kinetic parameters were determined by nonlinear least-squares regression of the experimental data. These calculated values of the product distribution were found to be in agreement with the experimental data.

Fatty acid composition of the red blood cell membrane in relation to menopausal status

PURPOSE: Menopausal status effects female anatomical functioning at a variety of system-wide and cellular levels, including cellular membrane composition. This study analyzed a nested case-control ORDET data set of 433 pre and post-menopausal breast cancer controls to examine the effects of menopausal status on the fatty acid composition of the red blood cell membrane.METHODS: ORDET is a prospective cohort study conducted in Italy to investigate the etiologic role of hormones and diet in breast cancer development. The fatty acid composition was measured and analyzed by gas chromotography, comparing retention time with standard measurement. Twenty-two individual fatty acids were measured, recorded, and categorized into four fatty acid groups: saturated, monounsaturated, polyunsaturated n–6 (PUFA n–6), and polyunsaturated (PUFA n–3) fatty acids.RESULTS: Post-menopausal women had consistently lower mean values for all four fatty acid categories and all individual fatty acids. Statistically significant mean differences, by menopausal status, were observed for three of the four fatty acid categories: saturated fatty acids (p = 0.006), PUFA n–6 acids (p = 0.001), and PUFA n–3 acids (p = 0.000). The biggest statistically significant differences in mean values among individual fatty acids for each category were observed for Palmitic acid (p = 0.009), Oleic acid (p = 0.040), Linoleic acid (p = 0.000), and Docosahexaenoic acid (p = 0.000). Individual fatty acids were also less highly correlated among post-menopausal women.CONCLUSIONS: There was an observed relationship between menopausal status and the fatty acid composition of the red blood cell membrane that warrants further study. This relationship may contribute to the physiological and psychological changes that occur during and after menopause, and may have far-reaching implications for women's health.

Metal−Support Interactions in Co/Al2O3 Catalysts: A Comparative Study on Reactivity of Support

Co/Al2O3 catalysts have been prepared with conventional impregnation and sol−gel methods to vary the chemical reactivity of the alumina support. The material system has been investigated with X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), diffuse reflectance Fourier transform spectroscopy (DRIFT), Brunauer−Emmett−Teller (BET) method, X-ray photoelectron spectroscopy (XPS), temperature-programmed reduction (TPR) (with thermogravimetric analysis (TGA) and differential thermal analysis (DTA)), and gas chromotography (GC) for the catalytic oxidation of CO. It had been found that the reactivity of the support changes the surface structure and chemical composition of catalysts significantly. When the metal−support interaction is weak, Co3O4 is a predominant surface phase (which is interfaced by a “cobalt surface phase”). With an increase in support reactivity, CoO and CoAl2O4 are found to be present on the surface. The cobalt content on the surface decreases upon the increase in suppor...

Effect of Water Quality Parameters on the Migration of Vinyl Chloride Monomer from Unplasticized PVC Pipes

The migration of vinyl chloride monomer (VCM) from unplasticizedpolyvinyl chloride (uPVC) pipes was investigated using locallymanufactured pipes. Specimens of 33 cm long were used throughoutthe research. The investigation was carried out under differentconditions of water temperature, pH and total dissolved solidsconcentration and at different durations of exposure. The VCMconcentration in the water was evaluated using the gaschromotography (GC)/head-space technique. A VCM concentration ofmore than 2.5 ppb was detected after 30 days of exposure at45 °C. The initial VCM concentration in the uPVC pipewas predicted using equations derived from Fick's first law ofdiffusion. Water tenperature did not affect the migration ofVCM, unless it was raised to high values (i.e. 45 °C).Total dissolved solids (TDS) and pH of water were found toaffect the release of VCM from uPVC pipes. Diffusion rate of VCMwas predicted as a function of pH or TDS values.

HIGH PLASMA LEVELS OF PHYTOSTEROLS IN PATIENTS ON PARENTERAL NUTRITION: A MARKER OF LIVER DYSFUNCTION

5 The phytosterols (PS) sitosterol, campesterol and lathosterol are found in intravenous fat emulsions at a total concentration of about 40 mg / dl. They have been suspected(1) to contribute to parenteral-nutrition associated liver disease (PNAC). AIMS: To test the hypothesis that PS is involved in PNAC, children under parenteral nutrition were monitored for PS in blood and for associated liver disease METHODS: 8 children under parenteral nutrion for more than 2 weeks were continuously monitored for up to 14 months. PS in plasma were analyzed by liquid gas chromotography, liver function tests included AST, ALT, bilirubin and GGT. RESULTS: 3 patients had PNAC, 3 patients showed transient anicteric liver dysfunction and 2 patients had normal liver function. In perids of normal liver function the sitosterin plasma levels ranged from 1,2 - 4,1 mg/dl. When AST, ALT and GGT were elevated in anicteric patients, plasma values of PS ranged from 4,9 - 11 mg/dl. In patients with severe PNAC levels up to 98 mg/dl were detected. A reduction of the intravenous lipid dosage in these 3 patients resulted in a slow decrease of plasma PS levels without improvement of liver function. Transient liver dysfunction was improved by reduction of the glucose infusion rate in spite of maintenance of the intravenous lipid dosage. Conclusion: We conclude that high plasma levels of PS are rather a symptom than the cause of liver dysfunction in patients with parenteral nutrition. The withdrawal of intravenous lipid emulsions at standard dosage in parenterally fed patients with liver dysfunction seems not justified. However it cannot be excluded from our observations, that high levels of PS may contribute to or aggravate liver dysfunction in some patients with PNAC.

Analysis of a diffusion dryer for the respiratory delivery of poorly water soluble drugs.

The purpose of this study was to analyze a diffusion dryer as a means to remove organic solvents from aerosol particles of poorly water soluble drugs. Aerosols of methanol, ethanol, and ethyl acetate were generated with an ultrasonic nebulizer, and inflow to outflow concentration ratio of vapor in a annular charcoal column was determined as a function of time by gas chromotography at two to four different airflow rates. In addition, the particle transmission efficiency was determined with an ethanol solution of the test compound, budesonide. The results were analyzed with equations originally developed for assessing the loss of drug from intravenous tubing along with independent measures of the adsorption isotherm of the vapors onto charcoal. Aerosol production was relatively constant with time, and the transmission of solid particles through the column occurred with efficiency nearing 100%. The inlet to outlet vapor concentration ratio was adequately described by a model of three resistances in series composed of the inner tube, the screen mesh, and the charcoal bed. The diffusion dryer was found to be satisfactory for the removal of methanol, ethanol, and ethyl acetate and the efficiency may be assessed from the adsorption isotherms on charcoal and the geometry of the dryer.

Treatment of petroleum-contaminated soils using iron mineral catalyzed hydrogen peroxide

Naturally-occurring iron minerals, goethite and magnetite, were used to catalyze hydrogen peroxide and initiate Fenton-like reaction of silica sand contaminated with diesel and/or kerosene in batch system. Optimum reaction conditions were investigated by varying H 2O 2 concentrations (0, 1, 7, 15, and 35wt%) and iron mineral contents (0, 1, 5 and 10wt%). Contaminant degradation in silica sand-iron mineral-H 2O 2 system was identified by determining total petroleum hydrocarbon (TPH) concentration with gas chromotography. Iron mineral system was less aggressive in contaminant degradation but it was more efficient than FeSO 4 system. Magnetite system provided more strong oxidation condition than goethite system due to coexistence of Fe +2 and Fe +3 and dissolution of iron. The results indicate that iron mineral catalyzed H 2O 2 system would have a promising application to site remediation since natural soils generally contain 0.5–5 wt% of iron minerals.

Cholesteryl ester transfer activity in liver disease and cholestasis, and its relation with fatty acid composition of lipoprotein lipids

Liver disease is accompanied by major qualitative and quantitative disturbances in plasma lipoprotein metabolism, the extent and intensity of which depend on the degree of parenchymal damage, cholestasis, or both. The main objective of this study was to determine the cholesteryl ester transfer CETP activity and its association with the lipoprotein neutral lipid composition in patients with either liver cirrhosis or cholestasis, as compared to normal controls. Lipoproteins were isolated by ultracentrifugation, lipids and apolipoproteins were measured by conventional methods, and the fatty acid composition was established by gas chromotography; CETP activity in lipoprotein-deficient plasma was measured by determining the transfer of [ 3H]cholesteryl esters from HDL to VLDL. Lipoprotein lipase and hepatic lipase activities were measured in post-heparin plasma by radiochemical methods. In patients with liver cirrhosis, low levels of VLDL, HDL, apo B, and Lp(a) were observed, as well as a change in the composition of HDL particles, with increases in the relative proportion of triglyceride and free cholesterol. Respectively, the last two changes could be attributed in part to the low hepatic lipase activity observed in this study, and to the low lecithin:cholesterol acyltransferase activity previously observed by others. In patients with cholestasis, a moderate hyperlipidemia due to the elevation of LDL was found. In contrast, HDL and apo A-I levels were very low reflecting a low number of HDL particles, which also had altered compositions with increases in the triglyceride and free cholesterol contents relative to apo A-I and esterified cholesterol, respectively. As regards the fatty acid composition of lipoprotein lipids, the two groups of patients showed, in general, a lower proportion of linoleic acid and a compensating higher proportion of oleic acid as compared to the controls, changes that were observed in both cholesteryl esters and triglycerides. In contrast, the proportions of oleic and palmitoleic acids in phospholipids were increased, whereas that of stearic acid was decreased in patients as compared to controls. In patients with liver cirrhosis, as well as in controls, no changes were observed in the fatty acid compositions of cholesteryl ester, triglycerides, or phospholipids among the different lipoproteins, which probably reflects the equilibration reached by the action of CETP. In patients with cholestasis, no differences were observed in fatty acid composition among the lipoprotein phospholipids but, interestingly, cholesteryl esters from VLDL had a significantly lower linoleic acid content than those from HDL, whereas triglycerides from VLDL had significantly higher oleic acid and lower linoleic acid contents than those from HDL. This distinct fatty acid composition of the neutral lipids between lipoproteins was associated with a significant decrease (25%) in the cholesteryl ester transfer activity in patients with cholestasis. We suggest that fat malabsorption due to the biliary defect may induce a decrease in cholesteryl ester transfer protein synthesis or secretion, which in turn would slow the equilibration of the neutral lipids among plasma lipoproteins.

Comparison between Continuous Stirred Tank Reactor Extractor and Soxhlet Extractor for Extraction of El-Lajjun Oil Shale

Abstract Extraction of El-Lajjun oil shale in a continuous stirred tank reactor extractor (CSTRE) and a Soxhlet extractor was carried out using toluene and chloroform as solvents. Solvents were recovered using two distillation stages, a simple distillation followed by a fractional distillation. Gas chromotography was used to test for the existance of trapped solvent in the yield. It was found that extraction using a CSTRE gave a 12% increase in yield on average compared with the Soxhlet extractor, and an optimum shale size of 1.0 mm offered a better yield and solvent recovery for both techniques. It was also found that an optimum ratio of solvent to oil shale of 2:1 gave the best oil yield. The Soxhlet extractor was found to offer an extraction rate of 1 hour to complete extraction compared with 4 hours in a CSTRE. The yield in a CSTRE was found to increase an increase of stirring. When extraction was carried out at the boiling point of the solvents in a CSTRE, the yield was found to increase by 30% on average compared to that of extraction when the solvent was at room temperature. When toluene was used for extraction, the average amount of bitumen extracted was 0.032 g/g of oil shale and 85.8% of the solvent recovered, compared with 0.0293 g/g of oil shale and 89.9% of the solvent recovered using a Soxhlet extractor. When chloroform was used for extraction, the average amount of bitumen extracted was 0.039 g/g of oil shale and 76.4% of the solvent recovered, compared with 0.037 g/g of oil shale and 84.1% of the solvent recovered using a Soxhlet extractor.

The hydrogenation and dehydrogenation of isobutene on Pt(111) monitored by IR–visible sum frequency generation and gas chromotography

The hydrogenation of isobutene (2-methylpropene) has been monitored near ambient pressure over a Pt(111) single crystal at 295 K by SFG vibrational spectroscopy. During hydrogenation tert-butyl groups and π-bonded isobutene species were the dominant surface species detected. Only small amounts of dehydrogenated species such as isobutylidyne could be observed unless the reaction conditions were very hydrogen poor. The hydrogenation rate for isobutene was at least one order of magnitude lower than for but-1-ene and cis-but-2-ene. Vacuum studies indicated that the rate of tert-butyl hydrogenation was much slower than that of isobutyl, which may force isobutane production to proceed from π-bonded isobutene through the slow kinetic step of isobutyl formation. Vacuum studies of isobutene dehydrogenation show evidence for a stable intermediate during the dehydrogenation of di-σ-bonded isobutene to isobutylidyne.

Multidimensional gas chromatographic separation of halocarbons from permanent gases using a capillary as the precolumn for a packed column

The chromatographic problems associated with strong adsorption of halocarbons onto a Chromosorb 107 packed column were eliminated by using multidimensional gas chromotography. The adsorption required rapid temperature programming to elute the halocarbons in a reasonable time, in turn producing peaks that interfered with the analysis of other sample components. In the multidimensional systems, the halocarbons are retained on a 530 μm i.d. capillary column while gaseous sample components pass through to a Chromosorb 107 packed column. In series/bypass mode, the packed column is isolated from the flow stream to allow the halocarbons to elute from the capillary column and then returned to elute the gases. In sequence reversal mode, the column flow sequence is reversed and the halocarbons elute directly to the detector, followed by the gas components. Both techniques eliminated the problems associated with adsorption of halocarbons onto the packed column. Overall performance and instrument ruggedness was superior in the sequence reversal mode. A packed column backflush technique was also evaluated, but the detection limit for the halocarbons was too high. © 1996 John Wiley & Sons, Inc.

Multidimensional gas chromatographic separation of halocarbons from permanent gases using a capillary as the precolumn for a packed column

The chromatographic problems associated with strong adsorption of halocarbons onto a Chromosorb 107 packed column were eliminated by using multidimensional gas chromotography. The adsorption required rapid temperature programming to elute the halocarbons in a reasonable time, in turn producing peaks that interfered with the analysis of other sample components. In the multidimensional systems, the halocarbons are retained on a 530 μm i.d. capillary column while gaseous sample components pass through to a Chromosorb 107 packed column. In series/bypass mode, the packed column is isolated from the flow stream to allow the halocarbons to elute from the capillary column and then returned to elute the gases. In sequence reversal mode, the column flow sequence is reversed and the halocarbons elute directly to the detector, followed by the gas components. Both techniques eliminated the problems associated with adsorption of halocarbons onto the packed column. Overall performance and instrument ruggedness was superior in the sequence reversal mode. A packed column backflush technique was also evaluated, but the detection limit for the halocarbons was too high. © 1996 John Wiley & Sons, Inc.

Compulsory random drug testing of prisoners in England and Wales: design flaws in the system

The Home Office has recently introduced compulsory testing of prisoners in England and Wales for drug abuse. From 1996 all prisons in the UK will be involved. Urine samples from approximately 10% of the prison population will be collected each month. The method of drug analysis selected by the Home Office is fast and economical but readily prone to interference from common substances giving false results. An elaborate procedure has therefore been evolved including a rigorous personal search of the prisoner to prevent sample adulteration. The definitive test gas chromotography — mass spectrometry (GC-MS), is more expensive but is resistant to sample adulteration, and currently all positive samples are confirmed by this method. In view of the proportion of samples that have tested positive, the extent of the unknown number of false negatives, and the possible rejection of the collection protocol by prisoners, savings could be made if the method of analysis employed in the first instance was GC-MS. This paper illustrates the inaccuracies produced in an assay technique similar to that used by the Home Office when urine is contaminated by simple, commonly available substances.

Extraction of El-Lajjun Oil Shale

Abstract Extraction of the bitumen fraction of El-Lajjun oil shale was carried out using 17 different solvents, pure and combined. Out of all the solvents used, toluene and chloroform were found to be the most efficient for extraction of the bitumen to perform the major part of the experiments. This selectivity was based on the quality and quantity of the yield and on the quantity of solvent recovered. Extraction was carried out using a Soxhlet extractor. For complete recovery of solvent the extract phase was subjected to two stages of distillation, simple distillation followed by fractional distillation, where different cuts of oil were obtained. It was found that an optimum shale size of 1.0 mm offered better solvent recovery. One hour was the optimum time needed for complete extraction. The yield of oil was determined from the material balance gained from fractional distillation after testing for the existence of any traces of solvent trapped in the different cuts by using a gas chromotography techniqu...

Examination of a blooming problem in a collection of unvarnished oil paintings

Abstract The bloom found on three late nineteenth century unvarnished paintings by W H Chariton, all on commercially prepared grounds was investigated. The grounds, paint media and bloom were analysed using gas chromotography ‐ mass spectrometry and differential scanning calorimetry. Raman microscopy, energy‐dispersive x‐ray analysis and other techniques were used to identify the pigments. It was found that the bloom on these paintings consisted of a mixture of free palmitic and stearic acids. The effect of pigments used in the paintings and in the underlying compositions on the density of the surface bloom was investigated. The presence of an impervious material, Melinex was a possible contributory factor in the formation of the bloom.

Biogenic sulfur emissions and aerosols over the tropical South Atlantic: 1. Dimethylsulfide in sea water and in the atmospheric boundary layer

We measured dimethylsulfide (DMS) in air (DMSa) and surface seawater (DMSw) on board the R/V Meteor during February–March 1991 on the tropical South Atlantic. Samples for the determination of DMSa were taken through a fluorinated ethylene/propylene Teflon inlet ≈33 m above sea level, preconcentrated by adsorption onto gold wool in quartz tubes, and analyzed by gas chromotography with flame photometric detection. The DMSa instrument is fully automated, providing improved precision, and processes up to four samples per hour. Over most of the cruise track, which followed the 19°S parallel between Brazil and Africa, DMSw, was significantly correlated to climatologically averaged chlorophyll concentrations obtained from coastal zone color scanner data, suggesting that remote sensing may be useful for estimating seawater DMS levels at least in some ocean regions. The cruise track proceeded from waters of low roductivity (off the coast of Brazil and in the subtropical gyre) to higher productivity (the Benguela Current and the upwelling region off Namibia and Angola); meteorological conditions were steady with consistent easterly winds. DMS values for air and water were low (≈ 50 ppt and 1–2 nmol L−1, respectively) in the areas of low productivity and increased simultaneously (≈ 100–300 ppt and 3–15 nmol L−1) as productivity increased. DMS sea‐to‐air fluxes (average 7.3 μmol m−2 d−1) were calculated based on different parameterizations; for the study region the differences between the results obtained from the different models were minor. DMSa was strongly correlated to its emission flux from the sea surface as estimated from DMSw and meteorological parameters. This suggests that the air/sea transfer parameterizations used are suitable for providing estimates of DMS flux from the oceans.

Enhancement of PCB congener biodegradation by pre-oxidation with Fenton's reagent

Polychlorinated biphenyls (PCBs) were widely used in a number of industrial applications for about 60 years and became distributed extensively in the environment due to their insolubility and persistence. Biodegradability of some PCB congeners has been confirmed by previous work, indicating degradation mechanisms involving dechlorination and cometabolism. Slow microbial conversions can be enhanced by pre-oxidation with Fenton's reagent (FR) to assist microbial decomposition of PCB congeners. In this study two model PCB congeners, 4,4′-dichlorobiphenyl (DCB) and 2,2′,4,4′,6,6′-hexachlorobiphenyl (HCB) were used as model PCBs. Bioremediation of artificially PCB-contaminated soil was measured by gas chromotography using an electron capture detector. Soil samples, both treated with FR and untreated, were subjected to constant temperature degradation tests using a selected microbial consortium for PCBs. Statistically different biodegradation rate constants were obtained for the two model PCB congeners when FR pre-oxidation was carried out at an optimum pH of 3, compared with an unpretreated comparable system. The rate constant for HCB was 5 times greater for the pretreated system, and up to 3 times greater for DCB.