An analytical technique is described which combines solvent extraction with gas chromatographic (GC) analysis in a simple and inexpensive apparatus involving very little solvent consumption. A small drop (8 μL) of a water-immiscible organic solvent, containing an internal standard, is located at the end of a Teflon rod which is immersed in a stirred aqueous sample solution. After the solution has been stirred for a prescribed period of time, the probe is withdrawn from the aqueous solution, and the organic phase is sampled with a microsyringe and injected into the GC for quantification. The observed rate of solvent extraction is in good agreement with a convective−diffusive kinetic model. Analytically, the relative standard deviation of the method is 1.7% for a 5.00-min extraction of the analyte 4-methylacetophenone into n-octane.

Solvent microextraction into a single drop.

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

In recent years, much attention in analytical chemistry has been paid to sample preparation techniques, especially those which minimise the consumption of organic solvents One of the most promising of these, solid-phase microextraction (SPME), is presented in both its theoretical and practical aspects Conditions which affect its performance are assessed, as are the problems which may arise from its use Finally, some typical applications are listed, highlighting the method's sensitivity and precision, and the range of samples where SPME can be used successfully

Solid-phase microextraction

In solid-phase microextraction (SPME), sorbent-coated silicafibers are used to extract analytes from aqueous or gaseous samples. After extraction, the fibers are directly transferred to the injector of a gas chromatograph, where the analytes are thermally desorbed and subsequently separated and quantified. This is a fast and simple analytical technique, which does not require solvents. An SPME method based on poly(acrylate)coated fibers has been developed for the phenol regulated by U.S. EPA wastewater method 604 and 623 and Ontario MISA Group 20 regulations. The method is capable of sub parts per billion detection limits of detection, and precision of 5-12 RSD, depending on the compound

Optimization of solid-phase microextraction conditions for determination of phenols

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

John R. Berg

Papers

Automation and optimization of solid-phase microextraction