Huu Van Tra

Relation between lipid peroxidation and inflammation in the pulmonary toxicity of cadmium

Lipid peroxidation (LPO), measured as thiobarbituric acid reactive substances (TBARS), was evaluated in lungs of rats 24 h after intraperitoneal injection of 50, 250, and 1000 μg Cd/kg body weight as CdCl2. In order to gain some insight into possible causative factors responsible for these oxidative phenomena, the redox-active elements iron (Fe) and copper (Cu), and total lung protein content (an indication of pulmonary inflammatory processes) were also measured. Results obtained demonstrate a similar dose-related, non-linear evolution of total lung TBARS and total lung protein as a function of increasing lung Cd concentrations. Standardization of total lung TBARS to lung protein content further resulted in a linear relationship with lung Cd concentrations, thus suggesting a possible cause-effect relationship between these parameters. No statistically significant association was observed between the dose-related evolution of lung TBARS, and iron (Fe) and copper (Cu) after Cd exposure. The results obtained provide support for the possible involvement of inflammatory phenomena as the most likely events responsible for the generation of LPO in lung tissue following acute exposure to Cd salts.

Determination of unreacted 2,4-toluene diisocyanate (2,4TDI) and 2,6-toluene diisocyanate (2,6TDI) in foams at ultratrace level by using HPLC-CIS-MS-MS

Isocyanates can cause occupational asthma. By using available HPLC-UVF methods, isocyanates can be quantified only at levels above 1% of the Permissible Exposure Limits (PEL). Once sensitized, workers can react to concentrations below these limits of detection (LOD) making these methods insufficiently sensitive to adequately evaluate trace amounts of isocyanates present in air or in materials at safe levels for sensitized workers. This article describes a novel method for isocyanate analysis allowing the quantification of 2,4TDI and 2,6TDI monomers at very low concentrations using HPLC-CIS-MS-MS. The methods sensitivity increases with a decrease in the alkali radius. The LOD is 0.039 ng mL(-1) for 2,4TDI and 0.100 ng mL(-1) for 2,6TDI in solution when lithium is the alkali adduct, which is 20 times more sensitive than HPLC-UVF method. This new method allows determination in foam at levels of 0.078 ng g(-1) for 2,4TDI and 0.200 ng g(-1) for 2,6TDI respectively, for a 0.5 g foam sample. This is more than 100 times more sensitive than other methods for determining free monomers in solid materials. Analytical reproducibility and precision are better than 92% and 93% for both diisocyanate monomers. The use of HPLC-UVF conventional method failed to detect unreacted isocyanates in foam samples, but TDI monomers were quantified by HPLC-CIS-MS-MS.

Sampling and analytical methodology development for the determination of primary and secondary low molecular weight amines in ambient air

In this project, a sampling device and an analytical method have been developed to simultaneously analyse the most frequently found low molecular weight amines, including aliphatic, aromatic and alcohol amines. These amines are diethanolamine, ethanolamine, methylamine, isopropylamine, morpholine, dimethylamine, and aniline. A sampling device was developed using a 37 mm cassette with glass fibre filters impregnated with sulfuric acid. Immediately after sampling, the filter was transferred to vials containing a solution of dansyl chloride. Dansyl chloride was used for derivatisation because it forms aromatic sulfonamides that are fluorescent and easy to protonate for MS detection. The effect of using an internal standard made with the dansylated derivative of 1-(2-methoxyphenyl)piperazine (MOPIP) on the uncertainty and efficiency of the method was also evaluated. This internal standard was spiked directly onto filters. The coupling of HPLC/ESI-MS was used for the simultaneous analysis of all the derivatives. This method showed detection limits of about 0.03 microg mL(-1) to 0.3 microg mL(-1) of amine with an average expanded uncertainty of 3% to 6% depending on the amine. The methodology recoveries are close to 100% for all the amines, and the overall estimated expanded uncertainties vary between 10% and 13% depending on the amine. This new strategy will be useful in evaluating workplace air since a unique sampling system will be used, independent of the amine to be quantified.

Quantitative determination of hexamethylene diisocyanate (HDI), 2,4-toluene diisocyanate (2,4-TDI) and 2,6-toluene diisocyanate (2,6-TDI) monomers at ppt levels in air by alkaline adduct coordination ionspray tandem mass spectrometry

Occupational exposures to isocyanates can lead to occupational asthma. Once sensitized, some workers could react to isocyanate monomers at concentrations below 1% of the Permissible Exposure Limit of 5 ppb in air. Currently available methods are not sufficiently sensitive to adequately evaluate isocyanates present at these levels in workplace air. This article describes a novel method for isocyanate determination allowing the ultratrace quantification in workplace air of hexamethylene diisocyanate, 2,4-toluene diisocyanate and 2,6-toluene diisocyanate monomers. Sampling is performed during a complete workshift at a flow rate of 1 L min(-1) with a cassette containing a 1-(2-methoxyphenyl)piperazine-impregnated 25 mm filter. Analysis is performed using liquid chromatography hyphenated with coordination ionspray tandem mass spectrometry. The analytical methods linearity was measured for a concentration range varying from the limit of detection of 0.04-0.13 ng mL(-1), depending on the monomer, up to approximately 32 ng mL(-1) for every isocyanate monomer, all with correlation coefficients (R(2)) greater than 0.999. The analytical methods lower limit of quantification combined with an adapted sampling strategy allow the quantification of isocyanate monomers down to 0.04 ppt for an 8 h work shift when a lithium adduct is used, which is more than 300 times lower than the most sensitive method currently available. This novel method can be used to confirm the very low level of isocyanate monomers for the safe reassignment of sensitized workers and it is also useful for charting the isocyanate dispersion tail in workplace environments.

Van der Waals liquids, Flory theory and mixing functions for chlorobenzene with linear and branched alkanes

The basic assumption of the Flory theory of solution thermodynamics, van der Waals behaviour of the components, is contravened by chlorobenzene and other complex liquids. Their internal pressure decreases, instead of increasing, with decreasing volume. Using chlorobenzene with a series of normal alkanes and four highly branched isomers the following quantities have been measured at 25 °C and equimolar concentration: HE, VE, dVE/dT, dVE/dp, Δ(γVT), CEp, Δ(αγVT) and ΔCv. Against expectation, the Flory theory predicts the main trends of all these data. dVE/dT, Δ(γVT) and CEp for n-Cm systems show deviations from the theory which are readily explained by temperature-sensitive order in the long-chain pure n-Cm liquids. We conclude that the Flory theory remains useful, at least for chlorobenzene, in spite of the breakdown of its van der Waals assumption.

Liquid structure and second-order mixing functions for 1-chloronaphthalene with linear and branched alkanes

Expansion coefficients (α), thermal pressure coefficients (γ), isothermal compressibilities, densities and heat capacities have been measured at 25 °C for pure components and the following mixtures: 1-chloronaphthalene with the series of normal alkanes (n-Cn) where n= 6, 8, 10, 12, 14, 15 and 16, and with a series of highly branched alkanes (br-Cn), 2,2-dimethylbutane, 2,2,4-trimethylpentane, 2,2,4,6,6-pentamethylheptane and 2,2,4,4,6,8,8-heptamethylnonane. With these data the following first- and second-order mixing quantities are reported: VE, dVE/dT, dVE/dP, Δ(γVT), CEp, Δ(αγVT) and ΔCν. Excess enthalpies, HE, for 1-chloronaphthalene–br-Cn, CEp for p-xylene–n-Cn(n= 8, 10 and 14), 1-chloronaphthalene–cyclohexane and 1-methylnaphthalene–n-C12 are also reported. VE and dVE/dT are strongly negative, and dVE/dP are positive, for the lower n- and br-Cn, becoming smaller for higher alkanes. Flory theory gives excellent predictions for each quantity with both series. The mixing function, Δ(γVT), deviates from the equality Δ(γVT)=–HE which is predicted by the Flory theory and other theories which assume van der Waals behaviour. Contrasting with cyclohexane–n-Cn and benzene–n-Cn, where –Δ(γVT) > HE, 1-chloronaphthalene with n-Cn gives –Δ(γVT) 8. The excess heat capacity CEp is anomalously positive for the n-Cn series and has higher values than for br-Cn. CEp equimolar values show a maximum against the carbon number n; similar behaviour was found for Δ(αγVT). ΔCν=CEp–Δ(αγVT) values are strongly positive for both series of alkanes. The results are explained by temperature-sensitive ordering of (2–2) and (1–2) contacts. The (2–2) order between long-chain alkanes is destroyed on mixing, giving negative contributions to dVE/dT, Δ(γVT) and CEp, as in cyclohexane and benzene–n-Cn. For 1-chloronaphthalene–n-Cn(1–2) compensatory order formed in solution has the opposite effect, producing –Δ(γVT) 0.

Micro method for determination of cadmium in tissues and slurried samples by use of flameless atomic absorption spectrometry

Abstract Cadmium (Cd) was determined in rat liver, kidneys, brain, testes, heart, and lungs with graphite furnace atomic absorption spectrometry following digestion of micro quantities (100 μl) of tissue homogenates in polypropylene micro diagnostic tubes. Microwave heating was used to complete the digestion. Results obtained demonstrated adequate precision, as indicated by relative standard deviations in control (±14%) and treated rat tissues (±2.6%). Cd measured in Standard Reference Materials that represented various biological tissues agreed with certified values, and no significant differences were observed between results obtained by use of the method of additions and those obtained by use of matrix-free reference solutions. Overall mean recovery of Cd added to Cd-treated rat tissue homogenates prior to the digestion procedure was 96%.

CIP10 Optimization for 4,4-Methylene Diphenyl Diisocyanate Aerosol Sampling and Field Comparison With Impinger Method

4,4-methylene diphenyl diisocyanate (MDI) aerosol exposure evaluation in spray foam insulation application is known as being a challenge because the spray foam application actually involves a fast-curing process. Available techniques are either not user-friendly or are inaccurate or not validated for this application. To address these issues, a new approach using a CIP10M was developed to appropriately collect MDI aerosol in spray foam insulation while being suitable for personal sampling. The CIP10M is a commercially available personal aerosol sampler that has been validated for the collection of microbial spores into a liquid medium. Tributylphosphate with 1-(2-methoxyphenyl)piperazine (MOPIP) was introduced into the CIP10M to collect and stabilize the MDI aerosols. The limit of detection and limit of quantification of the method were 0.007 and 0.024 μg ml(-1), respectively. The dynamic range was from 0.024 to 0.787 μg ml(-1) (with R (2) ≥ 0.990), which corresponds to concentrations in the air from 0.04 to 1.3 µg m(-3), assuming 60 min of sampling at 10 l min(-1). The intraday and interday analytical precisions were <2% for all of the concentration levels tested, and the accuracy was within an appropriate range of 98 ± 1%. No matrix effect was observed, and a total recovery of 99% was obtained. Parallel sampling was performed in a real MDI foam spraying environment with a CIP10M and impingers containing toluene/MOPIP (reference method). The results obtained show that the CIP10M provides levels of MDI monomer in the same range as the impingers, and higher levels of MDI oligomers. The negative bias observed for MDI monomer was between 2 and 26%, whereas the positive bias observed for MDI oligomers was between 76 and 113%, with both biases calculated with a confidence level of 95%. The CIP10M seems to be a promising approach for MDI aerosol exposure evaluation in spray foam applications.

Adaptation of CIP10 for the sampling of 4,4′-methylene diphenyl diisocyanate aerosols

Some sampling comparison studies have demonstrated that impinger and filter methods are not adequate for personal sampling of MDI aerosols in fast polymerization reaction processes. Other available sampling techniques for isocyanates have not been characterized for this application. These limitations led to the development of a new sampling method for MDI aerosols. The sampling method recommends a CIP10 device with a configuration in which a centrifuged liquid medium composed of DMPS + MOPIP (0.5 mg mL−1) would collect the MDI aerosols. The DMPS + MOPIP medium was characterized in the laboratory and the MDI–MOPIP monomer and oligomer derivatives were quantitatively extracted using 4 extractions with acetonitrile. Moreover, the DMPS does not prevent the fast reaction between the free MDI and MOPIP, and reaction rates similar to those in an impinger were obtained for the free MDI monomer and oligomers in the DMPS + MOPIP medium. The LOD and LOQ of the method were 0.010 μg mL−1 and 0.033 μg mL−1 respectively. The dynamic range was from 0.079 μg mL−1 to 0.787 μg mL−1 with R2 ≥ 0.990. The intra-day and inter-day precisions were <6% for all of the concentration levels tested, and the accuracy was within an appropriate range of 100 ± 6%. No matrix effect was observed, and a total recovery of 98% was obtained. The method under the current conditions optimized in the laboratory appears suitable to be tested in the workplace for MDI aerosol sampling and to be compared in a real situation with an impinger.

Absence of in vivo lipid peroxidation in CdCl2-treated rats as measured by exhaled pentane

We have used a new sensitive and non-invasive method, measuring exhaled pentane production, to evaluate in vivo lipid peroxidation (LP) in rats treated i.p. with CdCl2. Pentane, a by-product of LP, was measured 2, 6, 12, 24, 72 h and 8, 15, 22 days after treatment. No increase in pentane production was detected at these time periods for cadmium (Cd) doses reported to increase malondialdehyde (MDA) in major organs such as liver and lungs. This suggests that Cd cannot induce LP in vivo, but a prooxidant state which fragilized the tissues. Cd could also cause changes either in the production or in the metabolism of LP by-products (e.g. pentane).