When considering new sensory technologies one should look to nature for guidance. Indeed, living organisms have developed the ultimate chemical sensors. Many insects can detect chemical signals with perfect specificity and incredible sensitivity. Mammalian olfaction is based on an array of less discriminating sensors and a memorized response pattern to identify a unique odor. It is important to recognize that the extraordinary sensory performance of biological systems does not originate from a single element. In actuality, their performance is derived from a completely interactive system wherein the receptor is served by analyte delivery and removal mechanisms, selectivity is derived from receptors, and sensitivity is the result of analyte-triggered biochemical cascades. Clearly, optimal artificial sensory sys-

Conjugated polymer-based chemical sensors.

Headspace solid-phase microextraction is a solvent-free sample preparation technique in which a fused silica fiber coated with polymeric organic liquid is introduced into the headspace above the sample. The volatilized organic analytes are extracted and concentrated in the coating and then transferred to the analytical instrument for desorption and analysis. This modification of the solid-phase microextraction method (SPME) shortens the time of extraction and facilitates the application of this method to analysis of solid samples. The detection limits of the headspace SPME technique are at ppt level when ion trap mass spectrometry is used as the detector and are very similar to that of the direct SPME technique

Headspace solid-phase microextraction

Evolution of solid-phase microextraction technology

Solid-Phase Microextraction. A Solvent-Free Alternative for Sample Preparation

The solid-phase microextraction (SPME) technique involves exposing a fused silica fiber that has been coated with a stationary phase to and aqueous solution containing organic contaminants. The analytes partition into the stationary phase until an equilibrium has been reached, after which the fiber is removed from the solution and the analytes are thermally desorbed in the injector of a gas chromatograph

Automation and optimization of solid-phase microextraction

Mathematical descriptions of the absorption and desorption processes were developed and compared with experimental results for solid-phase microextraction (SPME) using poly(dimethylsiloxane)-coated fused silica optical fibers. Extraction times for benzene, toluene, and p-xylene using a coating thickness of 55 {mu}m are under 10 min and can be shortened substantially using agitation. Detection limits and distribution coefficients for several organic compounds are presented. 20 refs., 13 figs., 1 tab.

Dynamics of organic compound extraction from water using liquid-coated fused silica fibers

rn Solid-phase microextraction (SPME) is applied to the analysis of benzene, toluene, ethyl benzene, and xylenes in groundwater. The inexpensive SPME method reduced the sample preparation time by 3-7-fold when compared to purge and trap methods. The relative standard deviation ranged from 3 to 5% for the single-operator relative standard deviation using a methyl silicone fiber. Limits of detection of 1-3 ppb (w/v) were obtained when using a fiber coated with 56-pm methyl silicone film and FID detection. The linear range extended from 15 to 3000 ppb (w/v). Solvents have been completely removed from the sample preparation step.

Analysis of Substituted Benzene Compounds in Groundwater Using Solid-Phase Microextraction

Solid Phase Micro Extraction (SPME) involves exposing a fused silica fiber coated with stationary phase to a contaminated water sample. The organic analytes become partitioned between the stationary phase and the water and when equilibrium is reached the fiber is removed from the solution and the analytes are thermally desorbed in the injector of a gas chromatograph. The fiber is contained in a syringe to facilitate handling.

Factors which affect linear range, limit of detection, and total analysis time are discussed with regard to the development of a method for analysis of volatile compounds in environmental water samples. The sensitivity of the method was determined by the thickness of the film of stationary phase; the equilibration time, however, increased with the film thickness, although it can be minimized by use of a cross-shaped stirrer bar.

Increasing the thickness of stationary phase in the analytical column enables the cryofocusing temperature to be increased from −40 to −15°C. With an ion trap mass spectrometer, detection limits required by the US Environmental Protection Agency are met for all compounds except chloromethane and chloroethane. The method has been applied to environmental water samples.

Safa Motlagh

Papers

Dynamics of organic compound extraction from water using liquid-coated fused silica fibers

Analysis of Substituted Benzene Compounds in Groundwater Using Solid-Phase Microextraction

Environmental analysis of organic compounds in water using solid phase micro extraction

Solid-phase microextraction for the direct analysis of water: theory and practice

On-line monitoring of flowing samples using solid phase microextraction-gas chromatography