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PubMed2002

Dechlorination of chlorinated phenols by catalyzed and uncatalyzed Fe(0) and Mg(0) particles.

Uncatalyzed, and palladium-catalyzed Fe(0) and Mg(0) systems were examined for their efficiencies of dechlorination of 2.86 mM 4-chlorophenol (4-CP), 2.52 mM 2,6-dichlorophenol (2,6-DCP), 3.03 mM 2,4,6-trichlorophenol (2,4,6-TCP), and 2.48 mM pentachlorophenol (PCP) in 50/50 (v/v) 2-propanol/water under room temperature and pressure conditions. Previous investigators have found that PCP is extremely recalcitrant under these conditions. In this investigation, complete dechlorination of 5.0 ml of 2.48 mM PCP was observed for 1.0 g of 2659 ppm Pd/Mg (20 mesh) after 48 h. The only detectable products were cyclohexanol and cyclohexanone at 25% yield. No other chlorinated or otherwise products were observed by mass spectral analysis. It is hypothesized that volatile low molecular weight species were formed from the Pd/Mg dechlorination of PCP. Under conditions of equal surface area (0.0786 m2), the approximate order of PCP dechlorination power of these systems followed as 2659 ppm Pd/Mg>319 ppm Pd/Mg>Mg approximately 4856 ppm Pd/Fe>Fe. Degradation of the other chlorinated phenols by all metallic systems was more facile than PCP.

Catalysis↗
PubMed1999

Detoxifying chlorine rich gas streams using solid supported nickel catalysts.

Catalytic hydrogen treatment is presented as a viable low energy means of treating/detoxifying concentrated chlorinated gas streams to generate recyclable raw materials. Nickel (1.5% w/w and 15.2%) loaded silica and nickel (2.2% w/w) exchanged Y zeolite catalysts have been used to hydrotreat a range of chlorophenols (CPs), dichlorophenols (DCPs), trichlorophenols (TCPs) and pentachlorophenol (PCP) over the temperature interval 473 K</=T</=573 K. In every instance the nickel catalysts were 100% selective in cleaving the chlorine component from the ring, leaving the aromatic nucleus and hydroxyl substituent intact. The effects of varying process time and temperature are considered in terms of phenol yield and the ultimate partitioning of chlorine in the parent organic and product inorganic hosts. Chlorine removal rates, hydrodechlorination selectivity and apparent activation energies are also provided. Prolonged exposure of the catalysts to the concentrated chlorine gas streams resulted in an irreversible loss of activity which is related to the total concentration of chlorine that had been hydroprocessed. Hydrodechlorination proceeds via irreversible stepwise and/or concerted routes as is illustrated for the treatment of 2,3,5-TCP. Increasing the nickel content was found to raise the overall detoxification efficiency while the use of a zeolite support introduced spatial constraints which had a strong bearing on process selectivity.

Catalysis↗
PubMed2000

Monitoring of the pesticide levels in some water supplies and agricultural land, in El-Haram, Giza (A.R.E.).

Monitoring of pesticide residues were conducted at different locations in the El-Haram region Giza, Egypt. The water samples were collected from El-Haram Giza, canal water supplies (El-Zomor, Abd-el-aal land and seaside and El-Mansorya), in addition to El-Moheet drainage water. The soil samples were collected from the arable land that surrounds water canals. Water samples were obtained by solid phase extraction (SPE) and soil samples by gel permeation chromatography (GPC). The combination of gas chromatography and mass spectroscopy with different ionization techniques was used for determination and identification of the pesticides, which were quantitatively determined as 1 microgram 1(-1) levels in environmental samples. The residues of pesticides were varied between different locations. Also, organochlorine pesticide residues in El-Moheet drainage water were relatively higher than in the canal water. The concentrations of organophosphorous compounds (chlorpyrifos, dimethoate and parathion) seem to be low in water as compared to soil samples. Most findings were less than 1 microgram g(-1), which is considered a low-level finding. Sixteen organochlorine pesticides were detected in most of the water samples and the percent of positive samples followed the order drins > total BHC > total DDT > endosulfan > heptachlor epoxid > heptachlor. Pentachlorophenol (PCP) was detected only in El-Zomor and Abd-el-aal canal water. Results obtained confirm the presence of different pesticide residues representing different chemical classes in the canal waters. This means that the discharging of wastes in to the water supplies must be controlled. Drainage water was highly polluted and contains much more pesticide residues than different canal waters.

Agriculture↗
PubMed1999

Peroxidase-catalyzed in vitro formation of polychlorinated dibenzo-p-dioxins and dibenzofurans from chlorophenols.

Chlorophenols (CP) are transformed in vitro to polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/F) by a peroxidase-catalyzed oxidation. This is shown for 2,4,5-tri-, 2,3,4,6-tetra- and pentachlorophenol with plant horseradish peroxidase and with myeloperoxidase recovered from human leukocytes, each in the presence of hydrogen peroxide. The yield, the reaction and the PCDD/F-pattern found are dependent on the CP. The amounts of PCDD/F formed within 4 or 24 h are in the micromol/mol-range for all substrates and both peroxidases. The experiments suggest that biochemical formation of PCDD/F from precursors such as CPs can take place in the human body and that this metabolic pathway may lead to a higher inner exposure to PCDD/F than up to now assumed based on intake data for PCDD/F.

Benzofurans↗
PubMed1999

Immune parameters in biological monitoring of pesticide exposure: current knowledge and perspectives.

Exposure to pesticides can cause a number of effects on the immune system, varying from a slight modulation of immune functions to the development of clinical immune diseases. The aim of this study has been reviewing published data on immune effects of pesticides in humans, with particular attention for effects observed in absence of any other change, and to the possibility of identifying a dose effect relationship. Some evidence of immunotoxic effects in man involve organophosphorus compounds, some organochlorine insecticides (OC), some carbamates, some phenoxy herbicides, dithiocarbamates, and pentachlorophenol (PCP). The alterations are usually observed in absence of any other change; in some cases, data suggest the presence of a dose effect relationship. The prognostic significance of the observed changes is still unclear. The Authors propose a tier approach to assess immune effects in humans.

Antibodies↗
PubMed1998

Effects of hypoxia and toxicant exposure on adenylate energy charge and cytosolic ADP concentrations in abalone.

Many studies have used adenylate energy charge (AEC) as an index of an organism's metabolic state under conditions of imposed stress, either through natural or xenobiotic stressors. AEC is a linear measure of the ratio of ATP concentration to total adenylate concentration, which ranges in value from 1 in the fully charged state to 0. Paradoxically, high values of AEC are often associated with high toxicant exposures, and low AEC values with low exposures. These discrepancies may be caused by the inability of AEC measurements to adequately evaluate cytosolic adenylate concentrations, which are the critical parameters in enzymatic regulation. Consequently, the goal of this study was to compare AEC values, as measured by high performance liquid chromatography (HPLC), to free adenosine diphosphate (ADPfree) concentrations, as measured using the arginine kinase equilibrium reaction and in vivo 31P-NMR, in red abalone (Haliotis rufescens) in response to either hypoxia or toxicant (pentachlorophenol, or sodium azide) exposure. AEC values remain essentially constant when compared with control animals during periods of stress exposure and recovery. In contrast, calculated ADPfree concentrations are approximately a third of those determined by HPLC and nearly double in response to stress exposure. The physiologic importance of this response is demonstrated by increases in ATP formation via arginine kinase. These results are discussed in light of the pertinent mammalian literature.

Adenosine Diphosphate↗
PubMed1998

Sulfation of thyroid hormones by liver of rainbow trout, Oncorhynchus mykiss.

We studied hepatic sulfation of thyroid hormones (TH) in rainbow trout, Oncorhynchus mykiss. Sulfation of thyroxine (T4) and 3,5,3'-triiodothyronine (T3) was detected in the cytosolic (63-67%), microsomal (12-16%), nuclear (12-14%) and mitochondrial/lysosomal (7-8%) fractions. Using 3'-phosphoadenosine 5'-phosphosulfate (PAPS) as a sulfate donor, sulfation of T4 and T3 by the cytosolic fraction depended on protein concentration and time. The pH profiles for T4- and T3-sulfation were broad and overlapping with optimal pH values of about 6.5 and 7.0 U respectively. At pH 7.0, apparent K(m) (microM), Vmax (pmol/mg cytosolic protein per hour) and catalytic efficiency (Vmax/K(m)) values were 3,5',3'-triiodothyronine (reverse T3, rT3) = 0.7, 583 and 832; T4 = 1.7, 46 and 27; T3 = 11.5, 840 and 73. Inhibitor profiles for both T4- and T3-sulfation were not significantly different with a common inhibitor preference of rT3 > pentachlorophenol > triiodothyroacetic acid > tetraiodothyroacetic acid T4 = T3 = 3,5-diiodothyronine. T4-, T3- and rT3-sulfation activity decreased with increasing pre-incubation temperature (12, 24, 36 degrees C); however, there were no significant differences in T4-, T3- and rT3-sulfation activity at each pre-incubation temperature. We conclude that: (i) in trout, hepatic sulfation of TH is enzymatic and obeys Michaelis-Menten kinetics; (ii) like mammalian hepatic sulfotransferases (STs), trout hepatic STs are heat-sensitive cytosolic proteins using PAPS as a sulfate donor; (iii) unlike mammalian sulfation of TH, trout hepatic sulfation of T4, T3 and rT3 may be catalyzed by a single form of ST preferring rT3 as substrate and with a catalytic efficiency of rT3 >>> T3 > T4.

Animals↗
PubMed2001

Factors influencing nominal effective concentrations of chemical compounds in vitro: cell concentration.

In vitro potency data (e.g. EC(50) values), used to characterise the biological activity of chemicals, are generally based on nominal effective concentrations and thus depend on any factor influencing the availability of a compound. In this study the significance of cell binding for the availability of chemicals in vitro is (i) theoretically investigated by means of a simple equilibrium distribution model and (ii) experimentally examined using a bull sperm assay to measure the cytotoxic potency of selected compounds at different cell concentrations. Compounds were selected either to cover a wide range of hydrophobicity (log K(ow)=2.52-5.69) or to represent modes of cell binding other than partitioning into cellular lipids. With the exception of xylene, the EC(50) values increased with increasing cell concentration. The ratios of EC(50) values determined at about 120 x 10(6) and 15 x 10(6) cells/ml were: pentachlorophenol. 1.2, 1-nitronaphthalene: 1.9, thioridazine: 2.7, dieldrin: 4.1, hexachlorophene: 4.1, digitonin: 5.1, methylmercury chloride: 7.9, antimycin A: 10.1 and p,p'-dichlorodiphenyl dichloroethylene (p,p'-DDE): >19.1. The influence of partitioning into cell lipids was rather well predicted by the equilibrium distribution model, except for p,p'-DDE. The results show that cell binding can significantly affect the availability of compounds in vitro and thus toxic potencies and toxic equivalency factors.

Animals↗
PubMedDate not supplied

Tribromophenol induces the differentiation of SH-SY5Y human neuroblastoma cells in vitro.

Tribromophenol is a pesticide with fungicide activity, presently used as a replacement of pentachlorophenol as a wood preservative, and as a flame retardant in electronic and electrotechnical devices. Retinoic acid differentiated and non-differentiated SH-SY5Y human neuroblastoma cell cultures were exposed to a range of concentrations of tribromophenol for 24, 48 and 72 h and the effects evaluated at morphological, basal cytotoxicity and biochemical levels. Neuroblastoma cell number, evaluated by quantification of total protein content, was increasingly inhibited in accordance with the concentration of tribromophenol and the exposure time period. According to the mean effective concentrations, differentiated cultures were nearly three times more sensitive than naive cells. Lysosomal function evaluated by the neutral red uptake was stimulated, particularly in non-differentiated cells. MTS metabolization was stimulated by all the treatments, with more potency at 24 h for differentiated cells. Acetylcholinesterase activity increased with the time of exposure in non-differentiated cells, while in differentiated cells the activity was doubled at 24 h. Morphological alterations were evident from 12.5 microM, showing hydropic degeneration and reduction in cell number, and from that concentration, piknosis and apoptotic bodies were observed. In conclusion, the main effects detected for tribromophenol were the induction of neuroblastoma cell differentiation, as expressed by the inhibition of cell growth and the increase in acetylcholinesterase activity with a critical cell concentration of 0.1 microM. Apoptosis was observed at high concentrations. The induction of cell differentiation and the special sensitivity of differentiated cells can explain some mechanisms involved in the embryotoxic and foetotoxic potential of tribromophenol.

Biomarkers↗
PubMed2002

Metal-independent production of hydroxyl radicals by halogenated quinones and hydrogen peroxide: an ESR spin trapping study.

The metal-independent production of hydroxyl radicals (*OH) from H(2)O(2) and tetrachloro-1,4-benzoquinone (TCBQ), a carcinogenic metabolite of the widely used wood-preservative pentachlorophenol, was studied by electron spin resonance methods. When incubated with the spin trapping agent 5,5-dimethyl-1-pyrroline N-oxide (DMPO), TCBQ and H(2)O(2) produced the DMPO/*OH adduct. The formation of DMPO/*OH was markedly inhibited by the *OH scavenging agents dimethyl sulfoxide (DMSO), ethanol, formate, and azide, with the concomitant formation of the characteristic DMPO spin trapping adducts with *CH(3), *CH(CH(3))OH, *COO(-), and *N(3), respectively. The formation of DMPO/*OH and DMPO/*CH(3) from TCBQ and H(2)O(2) in the absence and presence, respectively, of DMSO was inhibited by the trihydroxamate compound desferrioxamine, accompanied by the formation of the desferrioxamine-nitroxide radical. In contrast, DMPO/*OH and DMPO/*CH(3) formation from TCBQ and H(2)O(2) was not affected by the nonhydroxamate iron chelators bathophenanthroline disulfonate, ferrozine, and ferene, as well as the copper-specific chelator bathocuproine disulfonate. A comparative study with ferrous iron and H(2)O(2), the classic Fenton system, strongly supports our conclusion that *OH is produced by TCBQ and H(2)O(2) through a metal-independent mechanism. Metal-independent production of *OH from H(2)O(2) was also observed with several other halogenated quinones.

Chelating Agents↗
PubMed1999

The damage-inducible (din) genes of Escherichia coli are induced by various genotoxins in a different way.

The SOS response of Escherichia coli strains carrying the lacZ gene fused to the polB (dinA), dinB or dinD gene were investigated after treatment with several chemical agents and gamma-radiation. The induction levels of polB::lacZ reached levels between 4.0- and 9.0-fold 120 min after treatment with nalidixic acid, H2O2 or ethanol. Pentachlorophenol did not significantly induce any din genes. gamma-Irradiation is not an inducer of polB and ethanol failed to induce dinB::lacZ and dinD::lacZ. Following irradiation with a dose of 10 Gy the responses of dinB and dinD were induced about 2.5-3.0-fold above non-irradiated dinB and dinD. We found that the responses of din::lacZ fusion genes to these genotoxins are induced in a dose-dependent manner. The polB gene showed antagonistic responses to the simultaneous treatment of nalidixic acid and H2O2 or nalidixic acid and ethanol. In addition, dinB and dinD in the presence of both nalidixic acid and H2O2 at the same time showed no synergistic responses.

Bacterial Proteins↗
PubMed1998

The fate of organic xenobiotics in aquatic ecosystems: quantitative and qualitative differences in biotransformation by invertebrates and fish.

Biotransformation of natural and man-made foreign compounds (xenobiotics) proceeds via introduction of a functional group (phase I metabolism) and subsequent attachment of a polar moiety to the group (phase II metabolism). The biotransformation fate of xenobiotics depends on the activities, complement and inducibility of the biotransformation enzymes. Previous analysis of the dependence of in vivo rates of biotransformation on tissue parent compound concentration for marine invertebrates revealed that hydrocarbons are metabolised more slowly than xenobiotics already containing functional groups, and crustaceans metabolise both types of xenobiotics faster than molluscs (Livingstone D.R., Persistent pollutants in marine ecosystems, pp. 3-34, Pergamon, Oxford). Use of the same approach showed that fish metabolise pentachlorophenol (PCP) and benzo[a]pyrene (BaP) faster than certain aquatic invertebrates, viz. rates of biotransformation to total metabolites (pmol min-1 g-1 wet wt.) at a tissue parent compound concentration of 10 nmol g-1 were, respectively, 19.2 +/- 3.7 (Carassius auratus) and 4.8 +/- 6.6 (molluscan species) (PCP), and 19.1 +/- 6.3 (fish species) and 2.1 +/- 0.2 (crustacean species) (BaP). The higher rate of biotransformation of BaP in fish is consistent with higher levels of total cytochrome P450 and inducible cytochrome P4501A (CYP1A) activity. The similar rate of metabolism of a hydrocarbon (BaP) (requires initial metabolism by cytochrome P450) and a functional group compound (PCP) by fish may also be due to the high levels of cytochrome P450, compared with the situation in invertebrates where rate-limiting cytochrome P450 may be responsible for the lower rates of hydrocarbon compared with functional group compound metabolism.

Animals↗
PubMed2002

Differences in genotoxicity of H(2)O(2) and tetrachlorohydroquinone in human fibroblasts.

During autoxidation of the pentachlorophenol (PCP) metabolite tetrachlorohydroquinone (TCHQ) the semiquinone is formed as well as reactive oxygen species (ROS). It was examined if *OH or the semiquinone are the cause of TCHQ-induced genotoxicity by direct comparison of TCHQ- and H(2)O(2)-induced DNA damage in human cells. All endpoints tested (DNA damage, DNA repair, and mutagenicity) revealed a greater genotoxic potential for TCHQ than for H(2)O(2). In the comet assay, TCHQ induced DNA damage at lower concentrations than H(2)O(2). The damaging rate by TCHQ (tail moment (tm)/concentration) was 10-fold greater than by H(2)O(2). DNA repair was lower for TCHQ than for H(2)O(2) treatment. This was shown by measuring DNA repair in the unscheduled DNA synthesis (UDS) assay and the persistence of the DNA damage in the comet assay. In contrast to H(2)O(2), TCHQ in non-toxic concentrations was mutagenic in the hypoxanthine-guanine phosphoribosyltransferase (HPRT) locus of V79 cells. Finally, there were also differences observed in cytotoxicity (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay) of TCHQ and H(2)O(2). Whereas the TCHQ cytotoxicity was enhanced during a 21h recovery phase, the H(2)O(2) cytotoxicity did not change. The results demonstrated that the pronounced genotoxic properties of TCHQ in human cells were not caused by *OH radicals but more likely by the tetrachlorosemiquinone (TCSQ) radical.

Cells, Cultured↗
PubMed1998

Sulfotransferase-mediated genotoxicity of propane 2-nitronate in cultured ovine seminal vesicle cells.

2-Nitropropane (2-NP) is a well-known genotoxin and carcinogen in rat liver. Several metabolic pathways, particularly cytochrome P450-, peroxidase- and sulfotransferase-dependent ones, have been suggested to lead to the formation of DNA-reactive species from 2-NP. Because rat liver cells express most types of xenobiotic-metabolizing enzymes, the role of specific pathways in the metabolic activation of 2-NP is difficult to assess in these cells. We have therefore investigated the genotoxicity of 2-NP and its anionic form, propane 2-nitronate (P2N), in cultured ovine seminal vesicle (OSV) cells. OSV cells lack cytochrome P450-dependent monooxygenase activity, but express prostaglandin-H-synthase (PHS) and, as we found out, phenol sulfotransferase. The induction of DNA repair synthesis and specific DNA modifications served as indicators for the genotoxicity of 2-NP and P2N. Both forms strongly induced repair, P2N being more active than 2-NP. The secondary nitroalkanes nitrocyclopentane and nitrocyclohexane also induced repair, whereas 1-nitropropane and the reduction product of 2-NP, acetone oxime, did not. P2N also elicited the formation of the characteristic DNA modifications 'DX1' and 8-aminodeoxyguanosine and increased the level of 8-oxodeoxyguanosine residues in the DNA. Pretreatment of OSV cells with indomethacin, an inhibitor of PHS, affected neither the induction of repair nor the formation of the DNA modifications, and P2N was not a reducing substrate for the PHS-peroxidase activity. In contrast, the sulfotransferase inhibitor pentachlorophenol strongly reduced genotoxicity. The results show that cytochrome P450-dependent monooxygenases are not required for the metabolic conversion of secondary nitroalkanes or their nitronates into DNA-damaging products, nor is PHS involved in the metabolic activation. Instead, the data corroborate an essential role of sulfotransferase(s) in the genotoxicity and carcinogenicity of secondary nitroalkanes. Moreover, it is demonstrated for the first time that these compounds can be genotoxic in cells other than hepatocytes or hepatoma cells. This implies that in species other than the rat, organs other than the liver can be targets for the genotoxicity, and possibly carcinogenicity, of secondary nitroalkanes.

Animals↗
PubMed2002

Vibrational analysis of substituted phenols: part I. Vibrational spectra, normal coordinate analysis and transferability of force constants of some formyl-, methoxy-, formylmethoxy-, methyl- and halogeno-phenols.

The Raman (including FT-Raman) and Fourier transform infrared (FTIR) spectra of 1,3-dihydroxybenzene, 1,4-dihydroxybenzene, 2-hydroxybenzaldehyde, 2-hydroxy-3-methoxybenzaldehyde, 4-hydroxy-3-methoxybenzaldehyde, 1,2-dihydroxy-3-methoxybenzene, 2,5-dihydroxytoluene, 2,6-dihydroxytoluene, pentachlorophenol and pentabromophenol were measured. Raman polarisation measurements were made wherever possible. A normal coordinate treatment was carried out for both the in-plane and out-of-plane vibrations of these molecules using a 123-parameter-modified valence force field. An overlay least-squares technique was employed to refine the force constants using 347 frequencies of 10 molecules. The reliability of these force constants was tested by making a zero-order calculation for 10 related molecules. Unambiguous vibrational assignments of all the fundamentals were made using the potential energy distributions and eigenvectors.

Fourier Analysis↗
PubMed2002

Solid-phase extraction method for the determination of free and conjugated phenol compounds in human urine.

A rapid flow system for automatic sample conditioning for the determination of phenol compounds in human urine has been developed and optimised. Free phenols are detected directly in urine samples while total phenols require acid hydrolysis to convert their conjugate fraction into free phenols, all compounds then being cleaned up and preconcentrated by solid-phase extraction. Separation and determination are done by gas chromatography, using mass spectrometry operating in the selective ion monitoring mode for quantitation. The linear range was 1-160 ng/ml of urine for most of the phenols. Limits of detection for phenol compounds (phenol, alkylphenols and chlorophenols) in the nanogram-per-millilitre range (0.3-0.6 ng/ml) are thus achieved by using 1 ml of urine; also, the repeatability, as RSD, is less than 6.5%. Based on the results for urine samples from unexposed individuals, 2-methylphenol, 2-chlorophenol and 2,4-dichlorophenol are largely detected in hydrolysed urine samples, whereas phenol and 4-methylphenol are detected in hydrolysed and unhydrolysed urine. Other chlorophenols such as trichlorophenols and pentachlorophenol are not detected. The results obtained in the analysis of urine from an individual before and after dietary intake reveal that the levels of phenol compounds in urine look related to food intake.

Calibration↗
PubMed2003

Spectrofluorimetric analysis of 7-hydroxycoumarin binding to bovine phenol sulfotransferase.

Phenol sulfotransferases (SULT1s, EC 2.8.2.1) catalyze sulfuryl group transfer from 3'-phosphoadenosine-5'-phosphosulfate (PAPS) to the hydroxyl oxygen of aromatic acceptor substrates. Previous work with the bovine SULT1A1 has utilized the highly fluorescent substrate 7-hydroxycoumarin (7-HC, umbelliferone) as an acceptor substrate [Biochem. Biophys. Res. Commun. 261 (1999) 815]. Here we report that adenosine-3',5'-bisphosphate (PAP)-dependent binding of 7-HC to bSULT1A1 can be observed due to the appearance of a 400-420-nm shoulder in the emission spectrum, using an excitation wavelength of 280 nm. This emission was observed by placing 7-HC in ethanol, which is consistent with bSULT1A1 phenol binding site hydrophobicity. Titrations with 7-HC indicate a K(d) for 7-HC of 0.58 microM and substoichiometric binding to the homodimeric enzyme. The bSULT1A1:PAP:7-HC complex could be disrupted with pentachlorophenol (PCP), titrations with which indicated 0.5 equivalents per enzyme subunit. Titrations of enzyme plus 7-HC with PAP also indicated 0.5 equivalents per enzyme subunit. These results suggest a model of homodimeric bSULT1A1 in which subunit interactions favor half-site reactivity in the formation of a dead end complex.

Animals↗
PubMed2001

Development of rotating electrochemical detectors for capillary electrophoresis.

A rotating disk electrode (RDE) has been evaluated and optimized for the detection of electroactive species separated by capillary electrophoresis (CE). With catechol as a working model, the limit of detection was estimated to be 0.3 microM, i.e., approximately 2.5-fold better than that of the stationary disk electrode (0.7 microM). Separation efficiency was significantly improved as exemplified by an increase of theoretical plates from 26,000 plates/m at 0 rpm to 67,000 plates/m at 500 rpm. Of particular importance was the capability of RDE to alleviate electrode passivation and electrical interference associated with high separation potential fields. Therefore, rotation amperometry was especially useful for analytes such as phenolic compounds that tended to rapidly foul the electrode surface. The RDE/ CE system was capable of separation and determination of pentachlorophenol in contaminated soils, and the result obtained agreed well with conventional liquid chromatography, an EPA recommended procedure.

Journal Article↗