Automatic solid-phase microextraction sampling apparatus

#The present invention relates generally to analytical devices and, more particularly, to instrumentation for chemical analyses and the like.

#Solid-phase microextraction (or “SPME”) is an analytical technique that uses a fluid polymer phase, a solid adsorbent, or a combination of the two, immobilized or coated on a fused silicon fiber. The coated fiber (hereinafter referred to as an “SPME fiber”) is immersed in a liquid sample, or in the headspace above the sample, to absorb the analytes of interest, which are subsequently desorbed with the aid of heat in a gas chromatograph injector and thus transferred to a capillary column. The selectivity of this technique may be varied by changing the type or thickness of the phase coating on the fiber. This analytical method has found widespread use in various fields, being used for biological and environmental analyses, toxicology and in the agro-food sector.

#An SPME unit essentially has two parts: (1) a probe comprising coated fused silicon fiber attached at one end to a plastic connector and housed slidingly in a needle such that the opposite end of the fiber may be exposed, and (2) a tubular, syringe-like container having a plunger threadably engaged with the connector. Sliding action of the plunger causes a larger or smaller portion of the fiber to extend from, or withdraw into, the needle. The analyte may be extracted either by exposing the coated portion of the fiber to the headspace of a test tube, immersing it in a fluid (e.g. water, milk, fruit juices, wines, etc.), or by exposing the fiber to air (for instance, in a working environment where the concentration of airborne pollutants is to be measured).

#A specific, illustrative automatic solid-phase microextraction (SPME) sampling apparatus, according to the present invention, is described below with reference to the accompanying drawings, in which:

#FIG. 1 is a perspective view of an automatic solid-phase microextraction sampling apparatus, according to one aspect of the present invention;

#FIGS. 2 and 3 show exploded and assembled perspective views, respectively, of a probe with an SPME fiber, in accordance with the present invention;

#The same numerals are used throughout the drawing figures to designate similar elements. Still other objects and advantages of the present invention will become apparent from the following description of the preferred embodiments.

#Referring now to the drawings and, more particularly, to FIGS. 1-11, there is shown generally a specific, illustrative automatic sold-phase microextraction or SPME sampling apparatus, according to various aspects of the present invention. In one embodiment, set forth generally in FIG. 1, the apparatus is shown in association with a detector for gas chromatographic analyses (a mass spectrometer, for example) 1. The apparatus comprises a robotic autosampler arm 2 supported by the gas chromatograph, on which one or more trays 4 for supporting probes 5 with SPME fibers are neatly arranged. These probes may, for instance, come from a campaign of environmental analyses and are ready for gas chromatographic analysis. Alongside the trays, a bracket 6 is provided for transferring the probes. The gas chromatographic apparatus also includes a plurality of injectors, e.g., two.

#As shown in FIGS. 2 and 3, sampling probe according to one aspect of the present invention, comprises a conventional probe having a needle 8, that slidingly houses a solid-phas microextraction (“SPME”) fiber 9. A plastic connector 10 is attached to one end of the fiber and—in conventional systems—is threadably engaged with the probe holder's plunger. A spacer ring 11, e.g., of brass, is likewise attached to an adjacent end of the needle. An adapter cap 12 constructed of a selected ferromagnetic material is preferably attached to connector 10, while a flange 13 also made of a selected ferromagnetic material is secured to spacer ring 11. In particular, flange 13 has a radial discontinuity 13a and a portion 13b that is threaded both internally and externally. To mount the flange on the spacer ring, the needle is passed through discontinuity 13a until it is coaxial with the flange, which is screwed onto the spacer ring by its threaded portion 13b until the two are juxtaposed. A mounting sleeve 14 is then threadably engaged with threaded portion 13b coaxially to the needle.