Part I. Development of low power, reduced pressure plasma ionization sources for mass spectrometry: The potential for enhanced speciation studies. Part II. Application of inductively coupled plasma mass spectrometry with high performance liquid chromatography for chromium speciation of chromium complexed azo dyes.

摘要

Part I. Low power, reduced pressure (LP/RP) plasmas are under investigation as ionization sources for mass spectrometry due to the potential for providing qualitative information not obtainable with conventional inductively coupled plasma mass spectrometry (ICP-MS). The addition of molecular mass spectra capabilities to trace elemental detection would be a significant advance in the field of elemental speciation.;A novel, lab manufactured LP/RP-He-ICP was interfaced with quadrupole mass spectrometry and gas chromatography for detection of four organotin species-tetramethyltin (TMT), tetraethyltin (TET), trimethylphenyltin (TMPT) and tetrabutyltin (TBT) and three volatile organobromine species-bromobenzene, 1-bromoheptane and benzyl-bromide. Sub picogram and low picogram elemental limits of detection were achieved for the organotin and organobromine species, respectively. Molecular mass spectra exhibiting characteristic fragmentation patterns resembling spectra from electron impact mass spectrometry (EI-MS) were extracted from the total ion chromatograms. Molecular ions for all three organobromine compounds were observed.;A mixed gas He/Ar radio frequency glow discharge (RF-GD) source was evaluated for tunable fragmentation capabilities. For tetramethyltin (TMT), the ratio of the elemental tin fragment (120Sn+) intensity to the molecular fragment (120Sn+-[CH 3]x) intensity was plotted versus the He/Ar plasma gas composition. Tunability towards more elemental fragmentation was observed with the addition of argon. Overall sensitivity for elemental tin (Sn+) decreased with the addition of argon to the plasma gas.;Part II. ICP-MS with high performance liquid chromatography (HPLC) was applied to determine the ratio of unbound chromium III to complexed dye chromium in the commercially produced azo dyes Acid Blue (AB)-158 and Acid Blue (AB)-193. Separation of unbound Cr III from complexed dye chromium was achieved for both dyes using a reversed phase C-18, endcapped column. The Cr III peak was identified by chromatographic retention time matching and spiking with a Cr III standard. A reproducible ratio of the unbound Cr III to complexed dye Cr peak areas was obtained for both AB-158 and AB-193. Process dye samples were analyzed but no unbound Cr III was detected. Investigation of the utility of a polymeric column to alleviate adsorption problems and solution desolvation to improve sensitivity were suggested as future directions in the development of this method.