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In this research work caffeine content in coffee bean samples from Daroo Labu, Booke, Shanan Dhugoo, Haabro and Xuloo of Western Hararghe administrative zone of Ethiopia were determined using High Performance Liquid Chromatography (HPLC) method. Caffeine in aqueous extract of coffee bean samples was dissolved in water (HPLC grade) to determine caffeine contents in coffee bean samples using HPLC method. The linearity of the High Performance Liquid Chromatography (HPLC) method obtained were R2 = 0. 9998. Limits of detection (LOD) and limit of quantification (LOQ) obtained were 9.10 ppm and 27.54 ppm respectively. The caffeine concentration in coffee bean samples obtained using HPLC method was 58.7065 ppm or 1.46% (w/w), 57.7152 ppm or 1.44% (w/w), 58.23408 ppm or 1.45% (w/w), 57.59039 ppm or 1.43% (w/w), 47.79959 ppm or 1.19% (w/w) for Booke, Shanan Dhugoo, Haabro, Daroo Labu and Xuloo coffee bean samples respectively. There is no significant difference between the caffeine contents of all coffee bean samples.

The pesticide residues in foods have received increasing attention as one of the most important food safety issues.Therefore, more strict regulations on the maximum residue limits (MRLs) for pesticides in foods have been established in many countries and health organizations, based on the sensitive and reliable analysis methods of pesticide residues. However, the analysis of pesticide residues is a continuing challenge mainly because of the small quantities of analytes as well as the large amounts of interfering substances which can be co-extracted with them, often leading to experimental errors and damage to the Analytical instruments. Thus, extensive sample preparation is often required for the pesticide residue analysis for the effective extraction of the analytes and removal of the interferences. This paper focuses on reviewing the recent development in the sample preparation methods for the pesticide residue analysis in some food samples. The methods include: