Polímeros de impressão molecular no preparo de amostras por extração em fase sólida na determinação cromatográfica de amitriptilina e nortriptilina em plasma

Abstract

Molecularly imprinted polymers (MIP) have appeared as new selective sorbents for solid-phase extraction (SPE). MIP is obtained through the preparation of polymers with synthetic recognition sites and they show predetermined selectivity to one or more analytes that can be attributed to the arrangement of functional polymer around the template. In this research MIP - using methacrylic acid (MAA) as monomer and amitryptiline (AMI) and imipramine as templates – and also a organically modified molecularly imprinted silica (MIS) – using 3- aminopropyltrimethoxysilane (APTMS) as monomer and AMI and NOR as templates – as well as the corresponding non imprinted polymers (NIP and NIS) were synthesized. The polymers were evaluated to application in SPE for high performance liquid chromatography (HPLC) analysis of AMI and NOR in aqueous and plasma samples. Desorption of the templates were performed in Soxhlet apparatus until negligible levels were obtained, as monitored by HPLC analysis. The MISPE were packed on polypropylene cartridges containing 200 mg of the polymer and using a vacuum manifold system for the sample and solvents percolations. The different steps of SPE: conditioning, loading, washing and elution were optimized. A SPE C18- HPLC method was also re-validated to compare the results. The selectivity of the polymers, evaluated by imprinting factors, i.e., response in MIS versus NIS, showed values of 2.5 and 2.6 for AMI and NOR respectively, in MISAMI and 1.7 and 3.5 in MIS-NOR for AMI and NOR respectively, in MIS-NOR. In the extraction using SPE C18, adequate parameters of validation were obtained showing the reliability of the method to the therapeutic drug monitoring, as linearity between 20 and 400 ng mL-1 (r=0.996); LOQ of 20 ng mL-¹; intra assay precision between 3.2 - 16.4% for AMI and 9.5 - 14.8% for NOR; mean recovery of 99.1% for AMI and 93.8% for NOR. Neither polymers prepared, by the synthesis in bulk of MAA (MIP-AMI and MIP-IMI) or by sol-gel process using APTMS (MIS-AMI and MIS-NOR) showed satisfactory conditions for using in MISPE coupled with HPLCUV analysis of AMI and NOR, mainly due to poor precision of the results in concentration range of concern. On the other hand, the use of MISPE resulted in cleaner chromatographic profile when compared to the SPE C18 cartridges in sample preparation.