Inductively coupled mass spectrometry has, over the years, been a useful tool for the analytical chemist through the capability to qualitatively and quantitatively determine the elemental composition of unknown inorganic substances. Identification has occurred in a large variety of sample matrices such as, water, soil, inks, and industrial wastes. Within the last decade the matrix of interest has expanded into the biological realm. The ability to separate these complex bio-matrices requires reverse phase separation and usually implies the use of an organic modifier in the mobile phase. Due to the nature of the argon plasma, the use of carbon based modifiers destabilizes the plasma at the standard flow rates, decreasing the available ionization energy and depositing carbon on the sampling cone, clogging the entrance into the mass spectrometer interface.
Current research involves evaluating commercially available micro-flow nebulizers which can allow the introduction of organic modifiers for increased chromatographic resolution of sample analytes because of the much lower solvent load to the plasma. Comparisons of various capillary flow nebulizers and spray chamber configurations are presented. An in-house spray chamber designed by the author is also evaluated.
Sensitive and selective techniques for detecting phosphorus- and sulfur- based analytes with an ICPMS equipped with an rf only driven octopole collision/reaction cell (CRC) are investigated. The first technique utilizes Xe gas to reduce and remove polyatomic interferences from 31P and 32S. The second uses an oxidation reaction to form new product ions, 31P16O+ and 32S16O+, to move elemental phosphorous and sulfur away from the mass range of elemental interferences.
The remaining focus of this dissertation is to utilize these earlier experiments and data from interfacing capillary flows into the Ar plasma to establish a qualitative and quantitative method for antisense oligonucleotides. This study describes a method for the analytical separation of 21-24-mer oligonucleotides using an RP C18 capillary column. Spectral data are comprised of element specific 31P and 32S, found in the phosphorothioate oligonucleotide backbone. UV (DAD) and elemental 31P and 32S data are obtained simultaneously through direct coupling of the capillary HPLC system to the ICPMS.
The scientific significance of the data contained in this dissertation developed a low ppt and reproducible Cr speciation method and lays the foundation for Cr speciation in more complex matrices. The establishment of five interfacing variations of capillary flow nebulizers and four different spray chambers on the 7500ce displayed total consumption sample introduction, without degrading plasma performance. The introduction of O2 into an octopole collision reaction cell for the first time in ICPMS analysis allows for additional applications in ICPMS ion-molecule chemistry and the possibility of using other reactive gases in the octopole (NH3, CH4). These studies for the first time, institute the use of element specific synthetic P/S tags in phosphorothioates and natural P tags in biological oligonucleotides to qualitatively and quantitatively detect their presence by ICPMS. The methodology generated an alternative way to quantitate oligonucleotides and assist in the advancement of clinical trails profiling metabolite and pharmacokinetic data for developing anti-sense oligonucleotides.