New developments in various spheres of the sciences have produced many commercial products and as well increased the risk to human health and environmental pollution.For example, packaging materials such as bisphenol and paraffin's have been found to migrate into food materials and also reacts with food components such as proteins. Pesticides such as chlorpyrifos and penconazole residues have been found in wines. Identifying and characterizing these materials require fast and accurate analytical instrumentation and techniques such as gas chromatography chemical ionization,(GC/CIMS). The GC/CIMS technique is based on ion molecule reactions and its usefulness depends on the types of reactions and also on the rates of its reaction. Sample ion/sample molecule (SIMS)reactions occur frequently under chemical ionization,CI, conditions with large sample size polar compounds and are useful in determining thermochemical parameters such as bimolecular rate of reactions, structure of compounds,sequence of reactions and in forming MH+ ions for molecular weight determination. SIMS reactions of polyethylene glycol and its derivatives under CI and FT/ICR are made in this report.