Abstract

ABSTRACT Polyethylene glycol dialkyl ethers (PEGDAE, R(OC2H4)nOR, R= alkyl) are commonly found in many industrial products and have become a major contaminant of the environment. Simple and user friendly techniques need to be identified and used to identify and quantify these compounds in the environment. The mass spectrometer is a useful instrument for detecting, identifying, determining structures and molecular weights of compounds, and monitoring their reactions. Since electron impact study do not properly identify PEGDAE’s, soft ionization techniques such as chemical ionization (CI) was used to aid qualitative and quantitative determinations of PEGDAE’s. The study was undertaken using soft ionization techniques such as CH4, i-C4H10 and CH4NH3 CI for proper identification and quantification of the PEGDAE oligomers. Three CI gases were evaluated for their suitability as an ionization reagent gas for these compounds. The EI and CI mass spectra of the PEGDAE’s were obtained by GC/MS using three different mass spectrometers. The results showed that the EI mass PEGDME, are characterized by few low abundance high mass fragment ions, and no M+ ions.. The CH4 CI spectra are much simpler than the EI spectra and comprised mostly of fragment ions: 59, 103, 147,.. etc. The base peak in the CH4CI spectra of all the PEGDME’s is the ion at m/z 59. The i-C4H10 CI mass spectra of the PEGDME’s are dependent on the pressure of the isobutane gas. The spectra are similar to the methane CI spectra but the extent of decomposition is less. The CH4/NH3 CI mass spectra of these compounds are also dependent on the sample size and the pressure of the CH4/NH3 gas mixture. The spectra are mixtures of CH4 and NH4+ CI spectra. The CI spectra of these compounds are sample size dependent but only the i-C4H10 and CH4/NH3 gas mixture are pressure dependent. The order of the extent of fragmentation obtained for the PEGDAE is: CH4> i-C4H10≥ CH4/NH3. The high pressure CI of i-C4H10 and CH4/NH3 reagent gasses consist essentially of MH+ and (M+18)+ ions and less fragmentation , therefore, they are of equal utility for qualitative and quantitative analysis of PEGDAE compared to CH4 as reagent gases. __________________________________________________________________________________________