1,720,964 research outputs found
Biological monitoring of exposure to n-heptane by gas chromatographic mass spectrometric determination of its metabolites
No full textAbstract
Urine samples from 10 workers that had been exposed to n-heptane were analysed by the GC/MS technique to verify the concentrations and the relative abundances of its metabolites. The procedure of sample preparation has undergone some modifications with respect to the Perbellini method and the mass spectrometric detection was carried out in selected ions monitoring conditions. The analyses of samples collected during three different workshifts showed that 2-heptanol was not the main metabolite and that the remains of 2-heptanone, valerolactone and 2,5-heptanedione were present at the beginning of the successive work-week at 12, 34 and 39% of the average values found at the end of the previous week. Overall, a very slow excretion rate was detected for the last metabolite. The main and significant metabolite at the end of the two workshifts was 2-heptanone which was detected in urine at average values of 413 and 238 μg g-1 creatinine. This urinary ketone correlated better than other metabolites with respect to the airborne n-heptane at the end of both the workshift and work-week. These preliminary data suggest that further studies should be carried out to confirm whether 2-heptanone is really useful as an n-heptane marker in biological monitoring
Soil organic matter mobilization by root exudates
No full textIn order to study the different soil organic matter mobilisation by agrarian (Zea mais: cultivars Paolo and Sandek)
and forest (Picea abies Karst. and Pinus sylvestris L.) root exudates, three different soils (Dystric Spodic Cambisol ± S1,
Haplic Luvisol ± S2 and Calcaric Cambisol ± S3) have been considered. Treating the soils with water (control) or plant
root exudates, soil organic matter extracts were obtained. The extracts were characterised by hormone-like activities
and gas chromatographic/mass spectrometric (GC/MS) measurements. Water extract and plant root exudates exhibited
no hormone-like activity, while the other soil-extracts were endowed with a different hormone-like behaviour. GC/MS
data indicated that in the acid soils (S1) Sandek and Picea abies exudates showed a greater ability in extracting organic
acid isomers (C14COOH, C15COOH and C17COOH), while in neutral soils (S3) all the exudates were active in separating
organic acids. In intermediate conditions (S2), Picea abies and Pinus sylvestris exudates liberated C15COOH
isomers, Paolo C11COOH isomers, while Sandek was not effective. The different role of plant root exudates in
mobilising bio-molecules from the bulk of the soil is propose
High-performance liquid chromatographic determination of urinary 2,5-hexanedione ad mono-2,4-dinitrophenylhydrazone using ultraviolet detection.
No full textAbstract
The good correlation between exposure to n-hexane and 2,5-hexanedione urinary excretion confers on this diketone an important toxicological meaning. This paper proposes a reversed-phase HPLC method which includes, after acid hydrolysis, a derivatization step of 2,5-hexanedione with 2,4-dinitrophenylhydrazine at 70°C for 20 min. The reaction conditions, such as temperature, reagent concentration and time, are optimized so as to allow the condensation of a single carbonyl group. A linear response was obtained in the 0.19-20.0 mg/l range with a detection limit of 0.03 mg/l, corresponding to a signal-to-noise ratio of 3. A phosphate buffer (pH 3.3)-acetonitrile mixture (50:50) as the eluent and UV detection at 334 nm were used
HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHIC DETERMINATION OF METHYL ETHYL KETONE IN URINE AS ITS 3-METHYL-2-BENZOTHIAZOLINONE HYDRAZONE DERIVATIVE
No full textAbstract
A HPLC method for the determination of methyl ethyl ketone (MEK) in urine after derivatization with 3-methyl-2-benzothiazolinone hydrazone is proposed. The calibration curve for the ketone was linear, ranging between 0.23-10 mg/L, with a detection limit of 0.025 mg/L. The results were compared to those obtained by GC-MS, coupled to the headspace technique. MEK derivatization and the derivative purification processes were verified with respect to the main variables such as reaction temperature, reagent concentration, probable interferences and enrichment phase. The method is simple and reliable and shows a good sensitivity
Biological Activity of soil organic matter mobilized by root exudates
No full textIn order to study the biological activity of soil organic matter mobilized by agrarian (Zea mays : cultivars Mytos and
Samantha) and forest (Picea abies Karst. and Pinus sylvestris L.) root exudates, two different soils, an Eutric Cambisol
(EC) and a Rendzic Leptosol (RL), were considered. Soil organic matter extracts were obtained by treating the soils
with water (control) or plant root exudates. The extracts were characterized by hormone-like activities and gas chromatographic/
mass spectrometric (GC/MS) measurements. Their effects on the nitrogen metabolism in maize seedlings
were evaluated. The nitrogen organification in the maize seedlings has been greatly stimulated by all the organic acid
extracts from the agrarian soil, while the extracts from the forest soil had no influence upon the metabolism; this indicated
a probable link between the plant and the environment. The different biological activities of the extracts are
discussed
MASS-SPECTROMETRIC AND GAS AND HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHIC BEHAVIOR OF AN IMPURITY IN 2,5-HEXANEDIONE
No full textAbstract
The analysis of 2,5-hexanedione, a metabolic compound of several industrial solvents, is normally carried out using gas chromatographic (GC) or CG-mass spectrometric (MS) techniques. This work, with the aim of verifying the possibility of determining the diketone by means of a high-performance liquid chromatographic (HPLC) method with UV detection, illustrates the importance of the choice of a 2,5-hexanedione standard for the determination of the diketone response factor. In some commercial diketone samples the presence of an impurity, which may interfere with the analysis of the target analyte, was ascertained. This impurity showed GC and HPLC behaviour similar to that of 2,5-hexanedione, but gave a very different UV response. This impurity was identified as 3-methylcyclopent-2-enone by means of MS, GC-MS, HPLC-photodiode-array detection, IR and UV spectrometry. The structure was confirmed by comparing the chromatographic, mass and ultraviolet data of the unknown compound with those of a synthesized reference sample. The well known difficulty in determining 2,5-hexanedione by HPLC with UV detection was reconfirmed owing to its low molar absorptivity
GC-MS investigation of polycyclic aromatic compounds in the manifacture of rubber tubes.
No full textAbstract
Mineral oils and carbon black containing polycyclic aromatic compounds (PAC), are normally used in the manufacture of rubber tubes. Owing to the toxicity of these chemicals it is important to have methods for their identification and for the monitoring of their concentration in the air of the workplace. In the present paper such a method using a two-stage air sampler and GLC-SIR-MS to monitor eight PACs is reported. PAC identification was confirmed by reference to commercially available pure compounds. Using the method, detection limits of 8-15ng ml-1, corresponding to a level of 12-23 ng m-3 in the workplace, were achieved. These are well below the NIOSH, OSHA, ACGIH prescribed TWAs.
Mineral oils and carbon black containing polycyclic aromatic compounds (PAC), are normally used in the manufacture of rubber tubes. Owing to the toxicity of these chemicals it is important to have methods for their identification and for the monitoring of their concentration in the air of the workplace. In the present paper such a method using a two-stage air sampler and GLC-SIR-MS to monitor eight PACs is reported. PAC identification was confirmed by reference to commercially available pure compounds. Using the method, detection limits of 8-15 ng ml-1, corresponding to a level of 12-23 ng m-3 in the workplace, were achieved. These are well below the NIOSH, OSHA, ACGIH prescribed TWAs
Determination of two-four condensed ring aromatic hydrocarbons in air using two specific sampling methods
No full textAbstract
In order to determine polycyclic aromatic compounds (PAH) in workplace air, we have tested two different trapping systems: a polytetrafluoroethylene filter coupled with XAD-2 sorbent and a Carbotrap 150 cartridge. The above sampling methods, that needed suitable flow rates for different adsorbent phases, were compared under the same collection conditions such as temperature, pollutant concentration and kind of analytes. Diesel engine exhaust gas was used as constant and uniform PAH source to test the two trapping systems in an highly polluted environment. The results indicated that the double sampler method was more efficient for the two-four condensed ring aromatic compounds analysed while the Carbotrap 150 proved more suitable for aromatic fraction present in the form of vapours
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