Determination Of Organic Species Research Articles

Extraction and speciation of arsenic in plants grown on arsenic contaminated soils

A sequential arsenic extraction method was developed that yielded extraction efficiencies (EE) that were approximately double those using current methods for terrestrial plants. The method was applied to plants from two arsenic contaminated sites and showed potential for risk assessment studies. In the method, plants were extracted first by 1:1 water–methanol followed by 0.1 M hydrochloric (HCl) acid. Total arsenic in plant and soil samples collected from contaminated sites was mineralized by acid digestion and detected by inductively coupled plasma-atomic emission spectrometry (ICP-AES) and hydride generation-atomic absorption spectrometry (HG-AAS). Arsenic speciation was done by high performance liquid chromatography coupled with HG-AAS (HPLC–HGAAS) and by HPLC coupled with ICP-mass spectrometry (HPLC–ICP-MS). Spike recovery experiments with arsenite (As(III)), arsenate (As(V)), methylarsonic acid (MA) and dimethylarsinic acid (DMA) showed stability of the species in the extraction processes. Speciation analysis by X-ray absorption near edge spectroscopy (XANES) demonstrated that no transformation of As(III) and As(V) occurred due to sample handling. Dilute HCl was efficient in extracting arsenic from plants; however, extraction and determination of organic species were difficult in this medium. Sequential extraction with 1:1 water–methanol followed by 0.1 M-HCl was most useful in extracting and speciating both organic and inorganic arsenic from plants. Trace amounts of MA and DMA in plants could be detected by HPLC–HGAAS aided by the process of separation and preconcentration of the sequential extraction method. Both organic and inorganic arsenic compounds could be detected simultaneously in synthetic gastric fluid extracts (GFE) but EEs by this method were lower than those of the sequential method. The developed sequential method was shown to be reliable and applicable to various terrestrial plants for arsenic extraction and speciation.

Quantitative Resonance Raman Spectroscopy

Abstract Determination of organic species at low concentration levels, particularly the simultaneous determination of a number of related compounds, challenges the ingenuity of the analyst. Measurements for nonvolatile and thermally labile compounds in the complex materials derived from the environment and living systems are especially difficult, and existing techniques aremostly ill-suited to this task. Resonance Raman spectroscopy provides an appropriate basis for such analyses.

Evaluation tests and applications of a double-layer tube-type passive sampler

Validation tests on a thermally desorbable tube-type passive sampler filled with two different graphitized carbon blacks were conducted in order to determine the influence of air velocity and direction, concentration and sampling time on sampling rate. A specially made apparatus was used to study the behaviour of the passive sampler in dynamic artificial atmospheres. This apparatus permits the simultaneous sampling of 48 tubes at two different air velocities, minimizing errors due to random variations of the operating conditions during a prolonged sampling time, which allows a better stochastic analysis of data to be performed. The results were in agreement with those obtained by actively sampling the same test-tubes. The results of laboratory and field tests showed that the behaviour of tube-type devices having a small cross-section is independent of the environmental parameters checked over a wide range of operating conditions. The constant sampling rate with these samplers in the range from 30 min up to more than 12 h and the high sensitivity of thermal desorption methods allow the determination of organic species down to the ppb level. A field experiment on the evaluation of the indoor pollution in a domestic environment is also described. The use of a double-layer tube-type passive sampler, with the adsorbent of lower specific surface area positioned at the exposed side of the device, allows a better desorption efficiency.

The Determination of Organic Species in the Telephone Central Office Ambient

The results of an analytical study are described characterizing the organic components in the air of a telephone central office. Air samples were taken from four telephone central offices and one telephone business office located across the continental United States for a period of about nine months. Samples were taken by passing a known quantity of air over activated charcoal and desorbing the entrapped gases into a gas chromatograph--mass spectrometer for analysis. The initial experimental results, the type and concentrations of the organic species, the source or origin of the species, the correlation between the inside and the outside air, and the importance or consequence of the findings are discussed. In addition, some mention is also made of the calibration procedure and the sample handling techniques.