SPME carryover effect

Several characteristics of the polymeric coatings affect the performance of SPME. Using thick coatings requires larger equilibrium and desorption times, and carryover effects may appear. See Chapter 2 of this volume for further details. 

Three different extraction volumes (2,4, and 8 mL) were tested with SPME extraction time set to IS min. The solid-phase microextraction time studied was IS, 30, and 60 min viiile die water volume was set to 4 mL. In order to study the fiber carryover effect in GC analysis, the total thermal desorption time (at 250 °C) was set to 10 min. Two sets of experiments were performed 1-min thermal desorption followed by 9-min desorption, and S-min desorption followed by S-min desotptioa... 

Urdike any other traditional GC injection methods (e.g., solvent injection using a traditional syringe), carryover effect plays an ingiortant role in SPME/GC analysis. If the thermal desorption time is not properly chosen, the con unds remaining on the SPME fiber lead to poor accuracy and precision in SPME/GC analysis. 

Table 1. Influence of Thermal Desorption Time on Carryover Effect of SPME Fiber...

There are some principal disadvantages that limit the use of fiber SPME. These include fhe limited capacity of SPME fiber and a requiremenf for a very low initial temperature for GC temperature programs because of the necessity of cryofocusing of the analyte, thus prolonging GC analysis time. In addition, desorption takes more time than in the injection of LEE or SPE extracts, and carryover effects occur very easily. As SPME is by nature a dirty extraction, quantification is more prone to errors due to changes in the matrix even when internal standards are used. Finally, SPME fiber is quite fragile. Because of these restrictions and limitations, fiber SPME is not a universal sample preparation method, especially not in bio-analytical laboratories, and is unlikely to become so in the future. 

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