Caution:

Without gas protection the fiber surface will be damaged if exposed to elevated temperatures.

Fiber Preconditioning

Prior to analytical use, it is mandatory to precondition each fiber at a specified temperature in an inert gas phase environment. The life span of the fiber can be extended if the fiber is not unnecessarily preconditioned at maximum Temperature. Generally, it is recommended to precondition the fiber 20°C above the planned operating temperature, while respecting the maximum temperature threshold. Recommended temperatures and conditioning times are given in Table 2.

Fiber Conditioning

It is part of the analytical process to condition the fiber after thermal desorption of the analytes has been completed. This conditioning is a preparatory step for the next analytical run. It is necessary to eliminate all possible contaminants from the fiber which have not been desorbed and transferred to the GC

column. To avoid contamination of the GC inlet system and/or the GC column, it is recommended to remove the fiber after the thermal desorption step from the GC injector and move the SPME Tool to the SPME Conditioning Module for the conditioning step. The large surface of the fiber can trap impurities from the ambient atmosphere if a fiber has been left in the open. Considering this, it is good recommended practice to run a blank prior to running a series of analytical samples. Evaluating the baseline level of the GC detector helps to ensure that the entire system, such as the fiber, the GC inlet, the GC column, and detector, is free from any contaminants.

Rinsing of Fibers

It is possible to clean the fiber using an organic solvent, should the fiber be subject to inappropriate storage, e.g keeping the fiber in the open at ambient environment without protection for a prolonged period, or if obvious dust particles are sticking to the fiber. The recommended types of solvents are listed in Table 2.

Do not use any other solvents than those mentioned here. Other solvents can cause a swelling of the fiber which would lead to significant damage. It is important that a fiber is not cleaned mechanically by any means; do not touch the fiber with fingers, not even when wearing gloves. The cleaning process can be done manually by dipping the fiber into a container filled with the appropriate solvent or in an automated manner by defining a vial for cleaning.

To avoid a potential misunderstanding, do not use a wash or waste solvent of the Wash Module from the PAL System. This solvent can be contaminated or the solvent in use may not be suitable for the particular fiber type.

General Remarks for Fiber Conditioning

and Cleaning

Table 2 summarizes the various parameters for conditioning and cleaning. The values provided are empirical values which are suitable for a number of applications and give reliable results. The life span of a fiber depends to a great degree on the field and type of application. Using the SPME technique, by inserting the fiber into a liquid with a high degree of matrix, the number of analyses can vary from a few to approximately 100 analyses. If the fiber is positioned in the headspace of a vial and avoids any contact with liquid and matrix, it is typically possible to run several hundred extractions.

It is not possible to visually judge the fiber quality if there are no obvious signs of major mechanical damage, such as a fiber fracture. Any sign of staining, caused by a starting vitrification of the surface in case of a PDMS fiber, or signs of a yellowish discoloration in the case of a Polyacrylate fiber, does not give any indication on theremaining life span of the particular fiber.

As a rule of thumb, the life span of a fiber can be extended if its exposure to high temperatures is minimized. Do not exceed the maximum temperature for each fiber type as shown in Table 2.