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PubMedDate not supplied

Determination of ethyl carbamate in alcoholic beverages and soy sauce by gas chromatography with mass selective detection: collaborative study.

A method using gas chromatography with mass selective detection for the determination of ethyl carbamate (EC; also known as urethane) in alcoholic beverages and soy sauce was collaboratively studied by 17 laboratories including authors' laboratories. The method uses prepacked columns for extraction of liquids with methylene chloride, and n-propyl carbamate as the internal standard. A practice sample and 6 samples of distilled spirits, fortified wines, table wines, and soy sauces were analyzed by each collaborator. Each matrix included blind duplicates of incurred and fortified EC at 3 levels. Distilled spirits contained 50-330 ng EC/g (ppb), fortified wine 40-160 ppb, table wine 10-50 ppb, and soy sauce 15-70 ppb. The ranges of the repeatability relative standard deviations, excluding outliers, were 4.03-6.63% for distilled spirits, 4.01-5.05% for fortified wine, 3.94-6.73% for table wine, and 4.70-8.49% for soy sauce. The ranges of the reproducibility relative standard deviations, excluding outliers, were 8.53-9.49% for distilled spirits, 6.84-12.02% for fortified wine, 8.86-18.47% for table wine, and 13.87-27.37% for soy sauce. Recoveries of added EC ranged from 87 to 93%. Recoveries relative to reference values, labeled as the internal standard, obtained by using gas chromatography/tandem mass spectrometry with a triple quadrupole mass spectrometer ranged from 89 to 100%.

Alcoholic Beverages↗

PubMed1993

The orbital glands of the terrapin Pseudemys scripta in response to osmotic stress: a light and electron microscope study.

The histochemical and ultrastructural features of both orbital glands--the anterior lacrimal and harderian glands--were compared in the terrapin Pseudemys scripta following adaptation either to distilled water or to seawater. Seawater adaptation activated the harderian gland and caused a major structural reorganisation. Type I cells increased in number, whereas type II cells became smaller and less numerous. The most striking change was shown by the type IV cells which display the features of a salt-secreting cell. This cell type increased in number and changed from a unicellular form to multicellular complexes. Transfer from fresh water to distilled water caused a decrease in alcianophilia in type I and type III glandular cells and degenerative phenomena were often seen in type I and type IV cells. The anterior lacrimal gland showed only minor changes either in distilled or seawater adapted terrapins. Transfer to distilled water also caused degenerative phenomena in the lacrimal gland. These results establish for the first time the involvement of the harderian gland of a terrapin in osmoregulation.

Adaptation, Physiological↗

PubMedDate not supplied

Supercritical fluid extraction of volatile N-nitrosamines in fried bacon and its drippings: method comparison.

N-Nitrosopyrrolidine (NPYR) and N-nitrosodimethylamine (NDMA), known animal carcinogens, are consistently formed in bacon during frying. As a result, commercial bacon has been subject to regulatory monitoring and compliance for the past 20 years to ensure that N-nitrosamines do not exceed the 10 ppb volatile level. Currently, time-consuming distillation-solvent extraction and solid-phase extraction (SPE) methods are used for this purpose. With an emphasis on reducing solvent use, we investigated supercritical fluid extraction (SFE) using supercritical carbon dioxide (SC-CO2) for isolation of volatile nitrosamines common to fried bacon. Eighteen fried bacon samples were analyzed for NPYR and NDMA by SFE, SPE, mineral oil distillation (MOD), and low-temperature vacuum distillation (LTVD) methods, using the same gas chromatographic-chemiluminescence detection (thermal energy analyzer) conditions. The range of values for SFE was 0.7 to 20.2 ppb for NPYR and none detected (ND) to 2.4 ppb for NDMA. Analysis of variance of the NPYR data showed a significant difference (p < 0.05) between SFE and SPE results and significant differences between these and those obtained by MOD and LTVD. Overall, SFE was superior to the other methods with the highest recoveries, best repeatability, rapidity of analysis, and solvent-sparing characteristics. Similar results were obtained for SFE after comparison with distillation and SPE methods for determining the same nitrosamines in fried bacon drippings.

Analysis of Variance↗

PubMedDate not supplied

In vitro comparative fluoride release, and weight and volume change in light-curing and self-curing glass ionomer materials.

The purpose of this study was to evaluate and compare in vitro fluoride release from and weight and volume changes of Photac-Fil, a light-curing polymaleinate restorative glass ionomer, with Ketac-Fil, a self-curing glass ionomer, and Ketac-Silver, a metal reinforced glass ionomer. Five discs of each material, measuring 2 mm height and 5 mm diameter, were suspended in separate vials of distilled water and laboratory artificial saliva. Fluoride release into the solutions was measured using a calibrated fluoride-sensitive ion meter initially at 24 hr and then weekly from 1 to 9 weeks. These results were evaluated statistically using repeated measures analysis of variance. Volumes and weights were recorded at the start and end of the experiment and analyzed using the paired t-test. Photac-Fil released similar amounts of fluoride to Ketac-Silver, but significantly less than Ketac-Fil in distilled water (P < or = 0.05). In artificial saliva, Photac-Fil released similar amounts to Ketac-Fil, but significantly more than Ketac-Silver (P < or = 0.05). Photac-Fil volume increased in distilled water and artificial saliva (P < or = 0.05) as did Ketac-Fil and Ketac-Silver in artificial saliva (P < or = 0.05). The only material that demonstrated significant net weight increase was Ketac-Silver in artificial saliva (P < or = 0.05). In summary, differences in fluoride release between these three glass ionomer materials varied as a function of the media in which they were stored. Whereas Ketac-Fil exhibited significantly greater fluoride release than the other materials in distilled water, in artificial saliva Ketac-Fil and Photac-Fil exhibited comparable fluoride release. Dimensional change, as evaluated by volume and weight differences, was also affected by storage media.

Analysis of Variance↗

PubMed1997

[Pharmacologic activity of the aqueous wood extract from Quassia amara (Simarubaceae) on albino rats and mice].

All the assays were done with an aqueous preparation of dry wood from Quassia amara (Simarubaceae). For the hippocratic assay, 12 female SDN rats were used, with an average weight of 144 g and separated in three groups of four individuals each. The dose used were 500 mg/kg and 1,000 mg/kg and the control group received 0.5 ml of distilled water. The extract administration and the observation of the animals were done daily during nine days. Acute toxicity of the preparation was studied with 25 male NGP mice with an average weight of 20.13 g, in groups of five individuals per dose. The oral administration was carry out with the following doses: 250, 500, 750 and 1,000 mg/kg, the control group received 0.5 ml of distilled water. No sign of acute toxicity was observed at any dose. For the toxicity analysis via intraperitoneal injection 15 male NGP mice were assigned to five groups (5 animals each) with doses of 500 and 1,000 mg/kg and a control group with 0.5 ml of distilled water. The group with the dose of 500 mg/kg, presented acute toxicity signs with a 24 hr recovery, and the 1,000 mg/kg dose was lethal to a 100% within 24 hr. The measuring of the peristaltic activity (movement of the intestinal content) were performed on 30 NGP male mice with an average weight of 22 g assigned to three groups of ten individuals each. One dose of 500 mg/kg and 1,000 mg/kg were orally administrated to each experimental group and 0.5 ml of distilled water to the control group. The marker used was activated carbon, orally supplied to every mice 30 min after the administration of the aqueous extract. The animals are decapitated and the measurement of the carbon motion in the small intestine was done after 30 min. Both dose increased the intestinal movement compared to the control group, but only the 1,000 mg/kg dose showed a statistically significant difference (p < or = 0.05).

Animals↗

PubMed1998

Analysis of fluconazole effect on Candida albicans viability during extended incubations.

Fluconazole is an azole agent with primarily fungistatic activity in standard in vitro susceptibility tests. However, recent work has demonstrated that this drug can reduce Candida albicans viability during prolonged incubations under non-growing conditions. The present study was undertaken to examine more closely some of the parameters of this killing activity. Fungicidal effects of 1.0 microg ml-1 of fluconazole were found during 7-14-day exposures in each of two media that prevented proliferation, distilled water and metal-depleted RPMI 1640 tissue-culture medium. Fluconazole appeared to be stable after being incubated at 37 degreesC for either 7 or 14 days. Strains of C. albicans resistant to fluconazole in standard short-term growth-inhibition assays were also found to be resistant to fluconazole's effect on viability in prolonged culture, suggesting similar mechanisms of action for these effects. C. albicans yeast cells pre-incubated for 7 days in distilled water were not more sensitive to the drug in short-term susceptibility assays. Although all proliferation of the organisms in distilled water cultures appeared to cease after 3 days, fluconazole added at 7 days still reduced C. albicans viability. Therefore, the drug appeared to kill the non-proliferating organisms directly rather than preventing growth and thereby the emergence of younger organisms that would live longer. Transmission electron microscopy demonstrated damage to the cell wall-cell membrane complex and interior contents of yeast cells incubated in distilled water alone; fluconazole appeared to increase the percentages of cells so affected. In summary, extended-incubation susceptibility tests demonstrated that fluconazole has direct fungicidal activity of non-proliferating C. albicans yeast cells. These results may be relevant to the manner in which this drug promotes clearance of chronic fungal infections.

Antifungal Agents↗

PubMed2000

Evaluation of dentin root canal permeability after instrumentation and Er:YAG laser application.

BACKGROUND AND OBJECTIVES: Smear layer removal with EDTA from root canal walls allows greater cleaning and disinfection of root canals. However, because Er:YAG laser acts on the removal of the smear layer, the objective of investigation was to analyze in vitro the effect of Er:YAG laser on dentin root canal wall permeability after endodontic instrumentation and irrigation with water or sodium hypochlorite and Er:YAG laser application. STUDY DESIGN/MATERIALS AND METHODS: A total of 25 extracted human maxillary incisors were divided into five groups: Group I, instrumentation with deionized distilled water as the irrigating solution; Group II, instrumentation with 1% sodium hypochlorite as the irrigating solution; Group III, instrumentation with deionized distilled water as the irrigating solution and Er:YAG laser application; Group IV, instrumentation with 1% sodium hypochlorite solution as the irrigating solution and Er:YAG laser application; Group V, instrumentation only up to #20 file with deionized distilled water as the irrigating solution and Er:YAG laser irradiation. The laser parameters were 15 Hz, 140 mJ, total energy 42 J, 300 pulses (Kavo Key Laser). Copper sulfate (10%) was used to evaluate dentin permeability. The penetration of copper ions into the dentinal tubules was observed using 1% rubeanic acid, which reveals copper ions, forming a stained compound ranging in color from deep blue to black. Transverse sections (500-microm thick) were obtained with a diamond disk from the cervical, middle, and apical thirds. RESULTS: The instrumentation of the root canal that used water as the irrigating solution followed by Er:YAG laser irradiation promoted the greatest increase in dentin permeability. The use of Er:YAG laser, 1% sodium hypochlorite + Er:YAG, and 1% sodium hypochlorite used alone showed an intermediate capacity of increasing dentin permeability. The use of water as the irrigating solution without Er:YAG laser promoted the least dentin permeability. CONCLUSIONS: The use of water as the irrigating solution after instrumentation and Er:YAG laser irradiation was an effective procedure for increasing dentin permeability.

Dental Pulp Cavity↗

PubMed1996

Wear testing of materials and surfaces for total knee replacement.

A simple wear test was investigated for evaluating the wear and damage of material pairs when used in total knee replacement. The test consisted of an axially loaded metallic femoral indentor and a reciprocating ultrahigh molecular weight polyethylene (UHMWPE) flat disk that represented the tibial component. A number of variables were studied including the effect of conformity by varying the radii of the femoral surface, distilled water or serum as a lubricant, different femoral materials, and different types of UHMWPE. In general, the different morphologies of the surface wear of the UHMWPE were similar to those seen on retrieved total knee replacements. Increased conformity with a cylindrical indentor gave a reduced wear rate initially, compared with that of the lower conformity spherical indentor. However, the wear rates were similar subsequent to this initial wearing in phase. Transfer films of UHMWPE were observed on the cobalt-chrome indentors for both serum and distilled water lubrication, although this film was more extensive for distilled water. The lowest wear rate was observed when oxidized zirconium was used on the femoral side, which was attributed to greater wettability, surface hardness, and immunity to oxidative wear. Tests using cobalt-chrome femoral cylinders and different grades of UHMWPE showed different wear rates. Of these PEs, GUR 415 showed less wear than both RCH 1000 and UHMWPE containing numerous fusion defects. For the latter, wear was attributed to a fatigue mechanism, although in most cases it was associated with surface phenomena rather than subsurface cracking. However, in some specimens of UHMWPE subsurface crack propagations occurred with defects. The test method is discussed in relation to its applicability to the evaluation and comparison of bearing materials and surfaces, with particular application to total knee replacements.

Alloys↗

PubMed2001

Investigation of the physicochemical basis of enantiomeric enrichment: The example of alpha-phenylethylamine with achiral dicarboxylic acids.

We investigated the enantiomeric enrichment of enantiomeric mixtures of alpha-phenylethylamine by achiral dicarboxylic acids. As achiral agents oxalic, malonic, fumaric, and phthalic acids were used. The results of the enantiomeric enrichment via partial salt formation followed by distillation were compared with enantiomer separation via crystallization of the neutral salt. Without the presence of a solid phase, enantiomeric separation is impossible. Our results show that the properties of the solid phase determine the separation. It is also confirmed by our observation that the eutectic points, which are observed on the 3-phase solubility diagrams of the solid neutral salts, can be found at the same initial enantiomeric composition as the point of intersection of distillate and residue of the distillation curves and the point of intersection of precipitated salt and mother liquor of the crystallization curves. Copyright 2000 Wiley-Liss, Inc.

Journal Article↗

PubMedDate not supplied

In vivo gene delivery to the lung using polyethylenimine and fractured polyamidoamine dendrimers.

BACKGROUND: Gene transfer into the airways could be of importance for the treatment of chronic lung diseases such as cystic fibrosis. In the past few years several attempts have been made to effectively deliver DNA to the lung using different viral and non-viral vector systems. Viral vectors and cationic lipids have been tested intensively but the properties of cationic polymers such as polyethylenimine (PEI) 25 kDa and fractured polyamidoamine dendrimers to deliver DNA to the airways have not been studied. Surfactant preparations have been shown to influence pulmonary adenoviral and naked plasmid DNA mediated gene transfer in vivo. We investigated the gene delivery efficiency of branched PEI 25 kDa and fractured dendrimers to the murine lung in vivo and also examined the effect of surfactant on PEI 25 kDa mediated gene transfer to the lung. METHODS: Cationic polymer/DNA complexes were prepared in 25 mM HEPES buffer (pH = 7.4) or double distilled water and administered to the lungs of BALB/c mice via cannula intubation. The trachea, left and right lung, heart, liver and esophagus were examined for luciferase activity. Inflammation was assessed by performing standard histology. RESULTS: PEI/DNA complexes showed a high level of luciferase gene expression in the lung. Complexes formed in double distilled water exhibited higher gene expression than complexes formed in 25 mM HEPES buffer (pH 7.4). The optimal N/P ratio was found to be N/P = 10 in double distilled water. Luciferase activity was only detected in the lung and decreased rapidly in a time-dependent manner. The addition of a natural surfactant preparation, Alveofact, slightly reduced gene transfer of branched PEI 25 kDa. Luciferase gene expression obtained by using fractured dendrimers was very low. CONCLUSION: The present study demonstrates that PEI 25 kDa, but not polyamidoamine dendrimers, effectively mediates transient gene transfer to the murine lung after intratracheal intubation. In conclusion, branched PEI 25 kDa was found to be an effective vector for pulmonary gene delivery in vivo, being superior to fractured dendrimers.

Animals↗

PubMed1996

Zinc-imidazole positive: a new method for DNA detection after electrophoresis on agarose gels not interfering with DNA biological integrity.

Nucleic acids separated by gel electrophoresis are commonly detected within the gel matrix with ethidium bromide staining, followed by gel irradiation with ultraviolet (UV) light. When the separated nucleic acids are to be recovered for further characterization or use, this methodology is unsuitable (i) because a significant number of chemical lesions to the nucleic acid molecules are caused, heavily compromising their biological activity, and (ii) because of health hazards due to accumulative direct contact with ethidium bromide and exposure to UV-light. As an alternative, for preparative purposes, a new nontoxic detection method employing zinc and imidazole salts is described. After electrophoresis, the gel is first washed in distilled water to substantially remove remaining electrophoresis reagents, then incubated in 40 mM zinc sulfate for 10 min to allow binding of Zn2+ to the DNA, and subsequently washed with distilled water to remove unbound Zn2+ from gel regions devoid of DNA. On soaking in 0.2 M imidazole for a few minutes, zinc-DNA complexes are visualized as deep-white (positive) stained bands against a slightly opaque background. The sensitivity is similar to that of ethidium bromide. Gels can be kept in distilled water for months without loss of staining. After zinc chelation, e.g. with EDTA, it is feasible to quantitatively recover chemically intact and biologically active DNA from the gels, as shown by reelectrophoresis and transformation experiments.

DNA↗

PubMed2003

The effect of 30% hydrogen peroxide on the color of compomers.

The interaction between bleaching agents and recently introduced compomers has several issues that need to be explored, including morphology and mechanical properties. To investigate the effect of 30% hydrogen peroxide, a bleaching agent, on the color of compomers, three compomers (Compoglass F, Elan, and F2000) were polymerized, bleached up to 120 h, and then measured to determine the reflectance of the specimen during the bleaching process. Color differences were evaluated from the reflectance and color values that were represented by CIE L*a*b* values. Compomers stored in distilled water were used as a source of reference. Teeth were also used for comparison. Color differences for both the tested teeth and compomers and different periods of bleaching and soaking in distilled water showed statistically significant difference (p < 0.0001). Among the tested compomers, Compoglass F demonstrated the highest color difference. In addition, the color differences were maximal during the first 24 h. After 24 h, the color difference increased nearly linearly. Compomers stored in both a bleaching agent and distilled water did not exhibit much color difference between them. However, the color difference between teeth and compomers was considerable.

Animals↗

PubMed1993

Irrigation does not dislodge or destroy tumor cells adherent to the tumor bed.

Local recurrences in the surgical bed after tumor resection may be due to residual tumor cells "dropping" into the wound. Irrigation with water is often used to remove these cells. We designed experiments to determine whether irrigation would prevent tumor recurrence. Surgical wounds of uniform size in C57BL/6 mice were seeded with 5 x 10(2), 5 x 10(3), 5 x 10(4), 5 x 10(5), or 5 x 10(6) viable syngeneic B16-F10 melanoma cells to test the hypothesis that irrigation with water would decrease local tumor recurrence. The tumor-contaminated wounds were irrigated with distilled water or with saline (0.9% NaCl) immediately or 5, 30, 60, 120, or 240 min after seeding. Control wounds were seeded but not irrigated. The technique of irrigation was altered in a second group of experiments such that the amount of time the tumor cells were exposed to the water or saline was 5, 10, or 15 min. To determine the rapidity and durability of tumor cell attachment to host tissue, 1 x 10(4) viable B16-F10 tumor cells were seeded in vitro onto freshly cut disks of syngeneic mouse dermis. The tissue was irrigated with saline or distilled water 0, 2, 5, 10, 15, 30, 60, 120, or 240 min later. Tumor growth was observed in all the mice and neither the mechanical action of irrigation nor the hypotonic effect of distilled water changed the rate of growth. Scanning electron microscopy (SEM) demonstrated stable and firm attachment to mouse tissue within seconds of seeding with no noticeable dislodgement or cytotoxicity by either saline or water irrigation. The data suggest that the commonly used technique of irrigating the bed of the resected tumor may not be of value in preventing local recurrences.

Animals↗

PubMed2000

Chemically mediated predator inspection behaviour in the absence of predator visual cues by a characin fish.

Animals commonly approach (i.e. 'inspect') potential predators. Glowlight tetras, Hemigrammus erythrozonus, have previously been shown to inspect the combined chemical and visual cues originating from novel predators and to modify their inspection (approach) behaviour depending upon the predator's diet. We conducted two experiments to determine whether tetras would inspect the chemical cues of injured prey or the dietary cues of a novel predator in the absence of any visual cues. Shoals of glowlight tetras were exposed to either distilled water (control) or the skin extract of swordtail (lacking ostariophysan alarm pheromones) or the skin extract of tetra (with alarm pheromones). There was no significant difference in the frequency of predator inspection behaviour towards swordtail or tetra skin extract compared to the distilled water controls. In the second experiment, we exposed shoals of tetras to either distilled water or the odour of Jack Dempsey cichlids, Cichlasoma octofasciatum, which had been food deprived, or fed a diet of swordtails or tetras. There was no significant difference in the frequency of predator inspection behaviour towards the odour of the starved cichlids and the odour of the fed cichlids in either of the two diet treatments. However, when tetras were exposed to the odour of cichlids fed tetras, they took significantly longer to initiate an inspection visit, remained further from the source of the chemical cues and inspected in smaller groups, compared with the odour of a starved cichlid or a cichlid fed swordtails. These data strongly suggest that tetras will inspect chemical cues alone, but only if the cue contains information about the predator. Copyright 2000 The Association for the Study of Animal Behaviour.

Journal Article↗

PubMed1997

Kinetics of Colloidal Deposition and Release of Polystyrene Latex Particles in the Presence of Adsorbed beta-Lactoglobulin Studied Using a Flow Cell

The effect of adsorbed whey protein, beta-lactoglobulin, has been investigated on the attachment of polystyrene latex particles to an indium tin oxide (ITO) surface and the subsequent release in anionic surfactant SDS solution and distilled-deionized water at pH 6.0. Experiments were carried out using a wall-jet flow cell and particle attachment was measured in situ using the technique of evanescent wave microscopy. The deposition rate of particles increased as predicted up to a shear rate of approximately 1000 s-1, for deposition at a diffusion-limited rate. There was a reduction in the rate at higher shear rates indicating a decrease in sticking efficiency. As the shear rate increased, the ITO surface became saturated more quickly due predominantly to blocking of the surface by deposited particles. The presence of adsorbed beta-lactoglobulin on the ITO surface caused a large reduction in the subsequent deposition rate of protein-coated particles. This was due to an increase in electrostatic repulsion. Differences were found in both the extent of removal and in the release (cleaning) kinetics of particles in SDS and in distilled-deionized water for the different particle-protein-ITO surface conditions investigated. Release of particles was also independent of the shear rate. Results were interpreted by considering the roles of protein replacement and elution which occurs in SDS solutions; >90% removal of protein-coated particles from a coated ITO surface was observed in SDS when both processes play a role. This compared to 55% removal in distilled-deionized water where they were considered negligible. Copyright 1997Academic Press

Journal Article↗

PubMed1994

Aluminum concentrations in tissues of rats: effect of soft drink packaging.

Aluminum is a commonly occurring trace element for which no nutritional requirements have been set. Some non-conclusive evidence exists suggesting a need of aluminum for growth, reproduction or health of man and animals. There is concern that exposure or consumption of aluminum may be toxic to humans and animals. The objective of the current study was to compare tissue levels of aluminum of rats fed soft drinks packaged in aluminum cans, glass bottles or distilled water. Thirty male weanling rats (Sprague-Dawley) were divided into three treatment groups of 10 rats each. All rats were fed rodent chow ad libitum throughout the study. Three different fluids, i.e. distilled water, diet soft drinks from aluminum cans and diet soft drinks from glass bottles, were fed for a period of 3 weeks. Aluminum contents of tissues were measured by atomic absorption spectrophotometry. Canned soft drink fed rats had significantly higher blood, liver and bone aluminum concentration than rats that were given glass bottled soft drink. There was a 69% higher bone aluminum concentration and 16% lower femur weight in rats fed aluminum canned soft drinks when compared with rats fed with distilled water.

Aluminum↗

PubMed1994

Differential staining of nerve cells and fibres for sections of paraffin-embedded material in mammalian central nervous system.

A differential staining method is described of myelinated fibres and nerve cell bodies applicable to sections of mammalian, including human, central nervous system specimens embedded in paraffin wax. Experimental and human necropsy material fixed in acetic paraformaldehyde in phosphate buffer was used. Sections of 15-20 microns in thickness were obtained, attached to slides, deparaffinized and hydrated. After hydration, sections are oxidized (30 s) in 2% potassium permanganate, bleached (1 min) in 5% oxalic acid and rinsed in distilled water. Staining is for 2-5 h in the following solution: 0.06% thionin, 1% formaldehyde, 10% acetic acid in distilled water. Sections are subsequently washed in distilled water, dehydrated through 96% and absolute ethanol, cleared in eucalyptol and mounted in Eukitt. Using the method described in the present paper, a differential coloration of myelin and neurons is obtained. Myelinated fibres appear red, whereas nerve cell bodies and glial nuclei are stained blue. This procedure provides a high contrast between myelin and cells suitable for observation and photography of sections. Simultaneous and differential coloration of both myelin and cells is easily and directly obtained with constant and homogeneous results.

Animals↗

PubMed1982

Determination of total pentachlorophenol in the urine of workers. A method incorporating hydrolysis, an internal standard and measurement by liquid chromatography.

Free pentachlorophenol (PCP) represents a small and variable fraction of total PCP excreted in the urine of exposed workers. A method incorporating hydrolysis is essential to be able to relate PCP excretion to absorbed dose. 3,5-Dichloro-2,4,6-tribromophenol (DTP) is added as an internal standard to a urine sample which is then acidified and steam-distilled. The distillate is made alkaline and extracted with methylene chloride to remove interferences. The distillate is then acidified and the phenols extracted into methylene chloride. The extract is evaporated, redissolved in acetonitrile and the PCP is measured using high pressure liquid chromatography (HPLC) using a 15 X 0.46 cm Spherisob-ODS 5 microns column with isocratic elution (H2O:CH3CN:CH3CO2H, 45:55:0.3 v/v). Detection is by fixed wavelength detector at 313 nm and calculation by the method of internal standardization. The biological threshold value used to trigger action to reduce exposure is 7 mg/l (corrected to a specific gravity of 1.024).

Chlorophenols↗