Isolation and preconcentration of volatile organic compounds from water

Basic Overview on Gas Chromatography Injectors

The main purpose of this chapter is to give a basic overview on instrumentation as well as the basics of gas chromatography ( GC ) injectors, and it is mainly devoted to students and beginners in the field of GC .

Valorisation of orange peel residues: waste to biochemicals and nanoporous materials

FRUIT FOR THOUGHT: Low-temperature microwave hydrothermal processing of orange peel not only enables the separation of the major components but also adds further value through the production of other high-value products: pectin and D-limonene, together with a rare form of mesoporous cellulose, are produced in a single step, without added acid. A process temperature change enables the conversion of D-limonene to α-terpineol.

Novel method for the determination of the methoxyl content in lignin by headspace gas chromatography

The paper reports on a headspace gas chromatographic (HS-GC) method for the determination of methoxyl in lignin. The method involves the quantitive cleavage of methoxyl with hydroiodic acid (HI) to form methyl iodide in a closed headspace sample vial at 130 °C for 30 min. After HI has been added, the sample is neutralized by injecting a sodium hydroxide solution; the methyl iodide in the vial was determined by HS-GC using a flame ionization detector. The results showed that the method has an excellent measurement precision (RSD < 0.69%) and accuracy (RSD < 3.5%) for the quantification of methoxyl content in lignin. The present method is simple and accurate and can be used for the efficient determination of methoxy1 content in lignin and related materials.

Monitoring the formation of trihalomethanes in the effluents from a shrimp hatchery

Formation of trihalomethanes (THM) was monitored at the Laboratório de Camarões Marinhos (LCM) from the Universidade Federal de Santa Catarina. THM could be present because chlorinated effluents from disinfection are discharged from the different hatchery rooms. THM quantification was done through an analytical methodology using Purge&Trap coupled with a gas chromatograph equipped with an electron capture detector. Relative standard deviation (RSD), limit of detection (LOD) and limit of quantification (LOQ) for the methodology corresponded to the ranges of 8-17%; 0.01-0.03 microg L(-1) and 0.03-0.08 microg L(-1), respectively. Linear working range was of 0.1-8.0 microg L(-1) for all compounds. Enrichment and recovery method was applied to evaluate possible matrix effects and the results varied from 71.2% to 107.9%. LCM was monitored between August and December, 2004. This study showed that THM did not increase with the increase in postlarvae production and also that the aquatic life and the surrounding environment were not affected.

Method of determination of nitrosamines in sausages by CO2 supercritical fluid extraction (SFE) and micellar electrokinetic chromatography (MEKC)

In this paper, the use of supercritical fluid extraction (SFE) and micellar electrokinetic capillary chromatography (MEKC) is proposed for the complete analysis of volatile nitrosamines in sausages. The extraction fluid used was CO2 and variables such as density, temperature of thimbles, extraction time, modifier, fluid flow, and kind of traps were investigated. Several experiments were carried out to obtain the most favorable conditions for analysis of volatile nitrosamines in sausages. The recoveries ranged from 21 to 82% for the five nitrosamines studied. The optimal condition of extraction was 0.2 g of sample fortified with 10 mg/kg, using dynamic extraction during 20 min and with adsorbent Florisil in the trap. The solvent selected for the elution of the analytes was methanol.

Determination of acidic and basic species by headspace gas chromatography

This paper reported a novel headspace gas chromatographic (GC) technique on quantification of acidic and basic species. It is based on an acid-base reaction between the measured species and bicarbonate in an aqueous solution, which generates carbon dioxide in a closed headspace sample vial. By operating at 60 degrees C, carbon dioxide is completely released to the headspace and thus can be measured by GC with a thermal conductivity detector. Bicarbonate concentrations of 0.030 and 0.0025 mol/L are recommended for general applications and very small species content, respectively. This method is able to accurately measure small sample sizes (down to few milligrams or microliters). The present method is simple, accurate, and automatic.

Monitoring of organic pollutants in coastal waters of the Gulf of Gdańsk, Southern Baltic

This paper presents an overview of changes in organic pollution of coastal waters of the Gulf of Gdańsk (Baltic Sea). Toxic pollutants including volatile organic compounds (VOC), volatile organohalogen compounds (VOX), chlorophenols, phenoxyacids, polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs) were determined in seawater from the Gulf of Gdańsk coastal waters in the period 1996-2001. In the case of the Gulf of Gdańsk, non-conservative behaviour of VOC was observed due to random temporal and spatial of inputs along the Vistula estuary and to the dilution of VOC-enriched river water with seawater. The concentrations of VOX in seawater decreased throughout the period and the concentrations of VOX were in the range of few ng dm(-3) up to 250 ng dm(-3), similar to estuaries elsewhere. The average concentrations of chlorophenols and phenoxyacids were between 0.1 and 6.0 and 0.05 and 2.2 microg dm(-3), respectively. However, remarkably high concentrations of 2,4-dichlorophenol (6 microg dm(-3)) were obtained in samples collected from the Vistula River. Generally concentrations of PCBs did not exceed few ng dm(-3) with the exception of 1999, when all samples exhibited elevated concentrations of PCBs. In addition, higher concentrations of PCBs in the open sea compared to river waters suggested localised inputs. Due to the ability of most organic pollutants to bioaccumulate and biomagnify, especially the persistent organic pollutants, continued monitoring is of crucial importance for the health of marine life in the Gulf of Gdańsk.

Multicomponent analysis of volatile organic compounds in water by automated purge and trap coupled to gas chromatography-mass spectrometry

The performance of an automated purge and trap concentrator coupled to gas chromatography-mass spectrometric detection was evaluated by analyzing 40 volatile organic compounds of different chemical families. Compounds chosen defined as toxic for the environment and for human health were selected according to Directive 76/464/CEE. The present work includes: (i) the optimization of the purge and trap conditions, (ii) the establishment of quality parameters and in last instance (iii) the analysis of surface waters. The analytical method consisted of a modification of the EPA Method 524.2 in which water was pumped, via an automated AquaTek 70 Liquid Autosampler to a 25-ml purging device, where samples were purged and trapped in a Tenax or Tenax-Silica and Charcoal column. Afterwards, helium was used to desorb the trapped analytes that flow directly into the GC column. Mass spectrometric analysis was carried out in selected ion monitoring and scan modes to ensure quantification and confirmation of the results. Parameters optimized were the sample volume analyzed, bubbling flow-rate and time and temperature of desorption. Optimal conditions lead to mean recoveries of 80%, limits of detection between 0.002 and 0.1 microg/l, linearity from 0.01 to 2.5 microg/l and maximum standard deviation of 10%, using a Tenax trap. This protocol permitted a high precision and sample throughput and was used to determine volatile organic compounds in surface river, effluents and coastal waters of Portugal, on a routine basis.

Analysis of nonvolatile species in a complex matrix by headspace gas chromatography

This study developed a phase reaction conversion (PRC) headspace gas chromatographic (HS-GC) technique for the measurements of nonvolatile species in liquid or solid samples. The technique is demonstrated by the measurements of carbonate in aqueous carbonate solutions and in kraft pulp mill liquor samples. A very small amount of sulfuric acid (volume of 0.5 ml, concentration of 2 mol/l) is used to acidify a sample of less than 300 microl in volume and convert the dissolved carbonate into carbon dioxide (gas) in a sample vial (reactor) that is analyzed by thermal conductivity detection through a headspace sampler. The carbonate concentrations measured by PRC-HS-GC in seven kraft liquor samples agree very well with those measured using a coulometric and a titrametric method. Simultaneous analysis of multiple species was also conducted to demonstrate the versatility of the method. The present method is very simple, rapid, reliable, accurate, and fully automated. It can be applied to analyze other nonvolatile species in various industrial and environmental samples.

Analysis of odorous compounds in water by isolation by closed-loop stripping with a multichannel silicone rubber trap followed by gas chromatography-mass spectrometry

An alternative technique for the isolation and concentration of odorous compounds found in potable water is described. The method currently employed by water authorities is closed-loop stripping with the collection of these substances on a small activated carbon filter. The compounds of interest are then extracted from the carbon using a suitable solvent. The authors offer a multichannel silicone rubber trap as an alternative to the carbon filter. The absorbed compounds are thermally desorbed from the trap, directly on to the gas chromatographic column for analysis by GC-MS, thereby eliminating the solvent extraction step required by the carbon filter. The multichannel silicone rubber trap, producing equivalent results, offers a number of advantages over the carbon filter.

Occurrence and determination of pesticides in natural and treated waters

Pesticides as environmental pollutants are described in detail along with their sources and paths of entry into various elements of the environment. Comprehensive literature data on the concentration of these pollutants in natural and treated waters and wastewaters are discussed. A wide selection of isolation and preconcentration techniques for these pollutants in water is presented and discussed. An emphasis is put on solid-phase extraction. In the case of the authors' work, a more detailed description is given.

Head-space solid phase microextraction for the GC-MS analysis of terpenoids in herb based formulations

Head-Space Solid Phase Microextraction (HS-SPME) has been employed for sampling of volatile components and their volatile decomposition products occurring in herbal medicines and herb extracts with subsequent injection into a gas chromatographic column. The identification and quantification was performed by coupled gas chromatography - mass spectrometry (GC-MS) with classical splitless injection, electron impact ionization and a quadrupole mass analyzer. As fast and inexpensive technique for the isolation of organic analytes HS-SPME with GC-MS can be successfully employed for the quality control of herbal medicines and other formulations containing herb extracts. Analytical results with satisfying accuracy and precision are given.

1995 McBryde Medal Award Lecture Solid phase microextraction – a unique tool for chemical measurements

The paper presents recent advances in solid phase microextraction (SPME). The method utilizes a small fused silica fibre coated with a suitable polymeric stationary phase for analyte extraction from various matrices. The fibre is mounted in a syringe-like holder for protection. SPME has been used for the characterization of polymeric coating properties. Infinite-dilution weight-fraction activity coefficients have been determined for five solutes in two different stationary phases. Their values correlate well with the structure of the analytes and the coating. Other SPME uses include simultaneous determination of 60 pesticides in liquid matrices. A comparison between SPME, liquid extraction, and Soxhlet extraction for the analysis of Atrazine, Simazine, and Metolachlor in well water, as well as Metolachlor in soil samples, produced similar results for all three methods. The solvent-free character of SPME enables its use as sample introduction technique for fast GC analysis. Separations of BTEX in less than 9 s, and of volatile compounds described in EPA method 624 in 2.5 min, are described. SPME has also been used for the analysis of tetraethyllead and Pb(II) in water. Before the analysis, lead is derivatized with sodium tetraethylborate, and the tetraethyllead formed is extracted from sample headspace. Sub-ppb detection limits have been achieved with FID. Finally, SPME has been coupled to HPLC with the use of a specially designed interface. The combination has been tested on samples of polyaromatic hydrocarbons and surfactants in water. Very good precision of retention times and peak areas has been achieved. Key words: solid phase microextraction, coating characterization, pesticide analysis, fast GC, lead and organolead compounds, SPME/HPLC.

Occurrence and determination of organic pollutants in tap and surface waters of the Gdańsk district

The results of the determination of different classes of organic pollutants (trihalomethanes, polycyclic aromatic hydrocarbons (PAHs), pesticides, volatile hydrocarbons and phenols) in ground water and drinking water sampled at different sites in the Gdańsk District are presented. Different methods were used to determine organic compounds in water: direct aqueous injection or sorption on solid sorbent (XAD-4) and extraction with pentane followed by a gas chromatography-electron capture detection (GC-ECD) for determination of volatile organohalogen compounds: purge and trap with a gas chromatography-flame ionization detection for determination of volatile hydrocarbons; sorption on solid sorbent XAD-4 or C18, elution with organic solvent and GC-ECD for determination of pesticides; sorption on solid sorbent C18, elution with organic solvent and a gas chromatography-mass spectrometry for determination of PAHs and sorption on solid sorbent C18, elution with organic solvent and high performance liquid chromatography-ultraviolet determination of phenols. The proposed methods have been used successfully for the determination of organic compounds in samples of tap, swimming pool, river and sea waters. The content of analysed organic compounds in the water delivered to the water supply system for Gdańsk from the surface water intake in Straszyn and from other selected intakes satisfies Polish, EC and WHO standards. The surface water bodies, i.e., rivers, sea and lakes in the Gdańsk District are not very polluted by anthropogenic compounds originating from municipal and industrial sewages and from agriculture.

Solid-phase extraction in multi-residue pesticide analysis of water

The determination of pesticides in water is fundamental to the solution of environmental problems as natural waters are usually contaminated with a large number of pesticides. The selection of an isolation and/or concentration technique depends largely on the class of pesticides to be determined. It is often necessary to determine simultaneously a wide variety of compounds in a water sample. Application of solid-phase extraction techniques offers a solution. The mechanisms of solid-phase extraction, types of sorbents and their application to multi-residue pesticide analysis are reviewed.