This project contents two sections: In first section, for the first time, a Solid-Phase Extraction (SPE) based on aptamer sorbent combined with Electrospray Ionization-Ion Mobility Spectrometry (ESI-IMS) was developed for the analysis of tetracycline in human urine and plasma samples. The effects of elution solvent, elution flow rate and extraction time were optimized. Under the optimized conditions, the detection limits were obtained 0.05 and 0.1 ? g mL -1 for urine and plasma respectively. The linear dynamic range is from 0.01 to 5.00 ? g mL -1 for the tetracycline. Extraction recovery close to 86.55% was obtained for urine samples and 82.84% for plasma samples. The relative standard deviation is about 6 for both urine and plasma samples. Ion mobility spectrometry with low cost, inexpensive maintenance and very fast analysis makes an attractive technique for the determination of the tetracycline in biological matrices. In second section, a new application of ESI-IMS has been introduced for analyze of human chorionic gonadotropin (hCG) and its various subunits. In molecular biology , hCG is a hormone produced during pregnancy that is made by the developing embryo after conception . Some cancerous tumors produce this hormone; therefore, elevated levels measured when the patient is not pregnant can lead to a cancer diagnosis. Due to gonadotropins extensive structural heterogeneity, the elucidation of hCG,, hCG?, and hCG?, remains one of the most challenging problems in the analysis of biological fluid. In this project the limit of detection 0.004 µg/mL and the linear dynamic range 0.05- 18.00µg/mL was obtained.