Organic Compounds In Water Samples Research Articles

Simultaneous quantification of polar and non-polar volatile organic compounds in water samples by direct aqueous injection-gas chromatography/mass spectrometry

A direct aqueous injection-gas chromatography/mass spectrometry (DAI-GC/MS) method for trace analysis of 24 volatile organic compounds (VOCs) in water samples is presented. The method allows for the simultaneous quantification of benzene, toluene, ethyl benzene, and xylenes (BTEX), methyl tert-butyl ether (MTBE), tert-butyl alcohol (TBA), as well as a variety of chlorinated methanes, ethanes, propane, enthenes and benzenes. Applying a liquid film polyethylene glycol or a porous layer open tubular (PLOT) divinylbenzene GC capillary column to separate the water from the VOCs, volumes of 1–10 μL aqueous sample are directly injected into the GC. No enrichment or pretreatment steps are required and sample volumes as low as 100 μL are sufficient for accurate quantification. Method detection limits determined in natural groundwater samples were between 0.07 and 2.8 μg/L and instrument detection limits of <5 pg were achieved for 21 out of the 24 evaluated VOCs. DAI-GC/MS offers both good accuracy and precision (relative standard deviations ≤10%). The versatility of our method is demonstrated for contaminant quantification in drinking water disinfection (advanced oxidation of MTBE) and for VOC concentration measurements in a polluted aquifer. The wide range of detectable compounds and the lack of labor-intensive sample preparation illustrate that the DAI method is robust and easily applicable for the quantification of important organic groundwater contaminants.

Application of a polysiloxane-based extraction method combined with large volume injection–gas chromatography–mass spectrometry of organic compounds in water samples

This work describes a novel, simple, and inexpensive approach for an absorptive extraction of organic contaminants from aqueous samples applying polysiloxane tubes. After the extraction, the tubes were desorbed with 200 μL of an organic solvent and 50 μL of the extract were transferred via large volume injection (LVI) into a gas chromatography–mass spectrometry system (GC–MS). Fourteen organic compounds covering a broad range in polarity with log K o/w-values between 2.6 (atrazine) and 7 (polychlorinated biphenyl 138, PCB 138) were chosen as model compounds. The experimental parameters affecting the efficiency of the process such as desorption solvents, the addition of salt and pH-change, the extraction and desorption time were carefully optimised. The recoveries were compared with theoretical values. The limits of detection (LODs) were in the range of 0.5–5 ng/L and the precision was 7–15%. The method was successfully applied to the analysis of a contaminated river water sample.

Membrane introduction/laser photoionization time-of-flight mass spectrometry

Two-photon resonance enhanced multiphoton ionization (REMPI) has been shown to be a unique ionization method for mass spectrometry, exhibiting both high sensitivity and chemical selectivity. Because REMPI is a gas-phase method, its applications have been limited either to direct analysis of vapor phase samples, or in conjunction with an initial laser desorption or other vaporization step. We describe here for the first time a combination of membrane introduction mass spectrometry (MIMS) and REMPI with time-of-flight mass spectrometry (TOF-MS), which allows for the direct analysis of trace amounts of organic compounds in water samples. The objective of our research was the detection of very low levels of aromatic contaminants, particularly benzene, toluene, and xylene (BTX), in aqueous solutions without interference due to the water. We have measured limits of detection (LOD) for selected aromatics in water below 1 part-per-trillion with an averaging time of less than 10 s using a continuous sample flow.

Oxygen consumption during mineralization of organic compounds in water samples from a small sub-tropical reservoir (Brazil)

Assays were carried out to evaluate the oxygen consumption resulting from mineralization of different organic compounds: glucose, sucrose, starch, tannic acid, lysine and glycine. The compounds were added to 1 l of water sample from Monjolinho Reservoir. Dissolved oxygen and dissolved organic carbon were monitored during 20 days and the results were fitted to first order kinetics model. During the 20 days of experiments, the oxygen consumption varied from 4.5 mg.l-1 (tannic acid) to 71.5 mg.l-1 (glucose). The highest deoxygenation rate (kD) was observed for mineralization of tannic acid (0.321 day-1) followed by glycine, starch, lysine, sucrose and glucose (0.1004, 0.0504, 0.0486, 0.0251 and 0.0158 day-1, respectively). From theoretical calculations and oxygen and carbon concentrations we obtained the stoichiometry of the mineralization processes. Stoichiometric values varied from 0.17 (tannic acid) to 2.55 (sucrose).

多孔質ポリスチレン樹脂カートリッジによる水中微量有機化合物の濃縮条件の一般化

General application conditions of the solid phase extraction with porous polystyrene polymer cartridges, Sep-Pak PS-1 and PS-2, were investigated.The PS-1 and PS-2 could adsorb various organic compounds from water in several ten times to several hundred times in comparison with tC18 which is a conventional octadecylsilane adsorbent. The adsorbable volumes for the solution to PS-2 are more than ca. 70% of those to PS-1. The adsorbable volumes for single component solution of 44 compounds to the PS-1 cartridge could be shown by the function of the concentration C and the solubility in water S. The adsorbed compounds could desorb with 3ml acetone from PS-1 and PS-2. From these results, the procedure for deciding the concentration conditions for simultaneous analysis or bioassay test of various trace organic compounds in water samples was proposed. It was confirmed that various trace compounds in the river water samples could be concentrated simultaneously by the proposed conditions.

On-Line Combination of a Silicone-Tubing-Probe Measuring System with HRGC for the Analysis of VOCs from Water Samples

A Silicone-Tubing-Probe measuring system with SnO2 sensor, based on the permeation of volatile organic compounds from a water sample to the gas phase through a dimethylsilicone membrane, was used for in-situ analysis of VOCs. The SnO2 sensor was used for the continuous determination of the sum of organic compounds liberated from the water sample. On-line combination of the measuring system with capillary gas chromatography enabled the determination of individual compounds and the study of the analyte permeation processes. The system was tested by using selected aromatic hydrocarbons, oxygenated and chlorinated compounds in water as simulated samples. The compounds were isolated from the water matrix and analyzed in the 10 μ/1 — 400 mg/1 concentration range. The combined Silicone-Tubing-Probe system can be used for monitoring volatile organic compounds in water samples.

Comparison of different methods for the determination of volatile organic compounds in water samples

The aim of this work was to compare the characteristics of three methods, membrane inlet mass spectrometry (MIMS), purge-and-trap gas chromatography-mass spectrometry (P&T) and static headspace gas chromatography (HSGC), for the determination of volatile organic compounds in water samples as used in routine analysis. The characteristics examined included linear dynamic ranges, detection limits of selected environmentally hazardous volatile organic compounds (e.g. toluene, benzene and trichloroethene) in water, required analysis time and reproducibility of the analytical methods. The MIMS and P&T methods had the lowest detection limits for all the tested compounds, ranging from 0.1 to 5 μg 1 −1. Linear dynamic ranges using the MIMS method were about four orders of magnitude and using the P&T method about two orders of magnitude. Detection limits of the HSGC method were 10–100 times higher than those of the other two methods, but the linear dynamic ranges were larger, even up to six orders of magnitude. The analysis time per sample was shortest for the MIMS method, from 5 to 10 min, and ranged around from 35 to 45 min for the HSGC and P&T methods. The reproducibilities of the methods were of the same order of magnitude, in the range of 1–13%. Agreement between the analytical results obtained for spiked samples and for environmental water samples by the three different methods was very good.

Preservation Techniques for Analysis of Organic Compounds in Water Samples – A Review –

Abstract Sample storage is a necessary and critical step in water analysis. During the storage, many changes in the sample may occur; namely chemical and physical reactions, microbiological degradation and the nature of sample-container may produce analyte losses. To minimize changes between collection and analysis, standard methods contain a part within which preservation techniques are described, e.g. chemical addition, temperature control, choice of sampling container and holding times. A review of some results published in recent studies show there are no absolute rules to prevent all the analyte modifications and to define a holding time optimized for each preservative technique. We have to take into account the character of the samples and the properties of the analytes to validate the preservation techniques. Generally, if immediate analysis is not possible, rapid addition of the extraction solvent and storage of sample extracts at 4°C is recommended. For the future, field extraction using SPE disk...

Determination of neutral chlorinated extractable organic compounds in water samples using large volume on‐column injection capillary gas chomatography–mass spectrometry

AbstractAn automated large volume on‐column injection technique (LOCI) for capillary gas chromatography – mass spectrometry, GC‐MS, with solvent divert and heated retention gap technology has been used to simplify the method for determining sixteen neutral chlorinated extractable compounds (NCEC) in industrial plant process water samples at a level of 10 ng/L. According to the simplified procedure, 30 mL of water sample is extracted with 5 mL hexane, and 100 μL of the extract analyzed by combining large volume on‐column injection with mass‐selective detection operated in the selected ion monitoring mode. This combination has enabled simplification of the sample preparation and analysis procedures and provided a fast, labor‐saving technique for analyzing water samples. Simplifications include significant reduction of sample and eluent volumes during extraction, and elimination of the Kuderna‐Danish evaporative concentration step. The latter simplification has not only resulted in significant time savings, both during the analysis and for subsequent glassware cleaning; analyte losses and the introduction of contaminants and artifacts which may occur during this step have also been eliminated.System behavior, e.g. linearity of detector response, method detection limit, and reproducibility, were evaluated for all sixteen analytes using spiked water samples in the lower ng/L range. The response of the mass detector is linear in the range 5–20000 ppt for all sixteen NCEC investigated. Injection of 100 μL of sample using LOCI makes it possible to achieve an instrument detection limit in the ppt range. The calculated method detection limits are similar to those of the instrument precision and are lower than the required method detection limit of 10 ppt.Extraction efficiency has been maximized by optimizing sample‐to‐solvent ratio and extraction time. The extraction efficiency seems to be independent of sample‐to‐solvent ratio in the range of 2. 5 to 6 and increasing the extraction time from 25 to 120 minutes resulted in no significant increase in efficiency. Extraction efficiency also seems to be independent of the concentration of analyte in the water samples. The simplified procedure presented here was automated by means of a laboratory robot and used to generate all the extraction data reported in this manuscript.

Effect of operating parameters in purge-and-trap GC-MS of polar and nonpolar organic compounds

The operating parameters of purge-and-trap sampling significantly affect the sensitivity of the analysis of volatile organic compounds in water samples. The effects of puge volume, sample temperature, sample volume, dry purge volume, desorption temperature, desorption time and cold-trap temperature have been studied for some polar and nonpolar organic volatiles using a purge-and-trap sampler interfaced with a direct coupling to a gas chromatograph-mass spectrometer. It is shown that the sensitivity and in some cases the specificity of the method can be greatly improved through careful optimization.

A new screening procedure for the estimation of oxidizable organic compounds in water samples

Immobilized lead dioxide (supported on SiO2) has been used as the packing material in a solid phase reactor for the oxidation of organic compounds in water samples by flow injection analysis (FIA). On-line oxidation takes place in a FIA-system; this allows the detection of mobilized Pb2+ either photometrically, after complex formation with 4-(2-pyridylazo)-recorcinol (PAR), or directly with flame-AAS. The oxidation yield is quite different (0–100%) for a variety of organic compounds; however, calibration was possible in all cases investigated. Thus the systems can be used for the screening of polluted waters and as a post-column chemical-reaction detector (e.g. after HPLC-separation of organic compounds). After modification the FIA determination of COD equivalent values should be possible.

Screening methods for the identification of organic emissions from indoor air pollution sources

Development of on-line gas Chromatographic screening procedures is necessary to permit subsequent evaluation of materials in test chamber studies. This screening uses techniques such as static vapor-phase sampling by ‘headspace’ methods, and a dynamic method similar to the ‘purge-and-trap’ procedures used for determination of volatile organic compounds in water samples. These are methods of sampling that simulate the chamber conditions on a small scale, while allowing emissions to be collected and analyzed. The evaluation is done to select gas Chromatographic columns and develop operating conditions that will permit the rapid and reliable separation of chemical compounds generated during testing. The Chromatographic procedure is used in the qualitative identification of chemical compounds by gas chromatography/mass spectrometry. After identification of the compounds or, alternatively, their chemical classes, representative members are selected as calibration standards for the actual emission testing program. The standards selected are adequate to allow, in most cases, either quantitative or semi-quantitative calculation of the amount of each material present in the chamber exhaust gas. The use of response curves for the chemical classes allows subsequent recalculation of the amounts for each compound.

Determination of trace volatile organic compounds in water samples by membrane introduction mass spectrometry.

A new method of analysis was proposed based on the use of permselective membrane which gives the possibility of enriching and analyzing trace volatile organics in waters. A silicone membrane introduction device which is simple and easy to construct was designed to couple with JMS-D300 Mass Spectrometer. A quantitative formula which is available in the Membrane Introduction Mass Spectrometry was deduced. This paper studied the determination of alkanes, aromatic compounds and halogenated organics in waters by MIMS and discussed the effects of equilibrium time, temperature, sample volume, sample matrix etc. on responses of analyzed components. It was found that 22 volatile organics presented a wide linear concentration range from ppb to ppm, detection limits from 0.1 to 10 ppb and recoveries from 90% to 110%.