Effects of Various Liquid Chromatography Mobile Phase Solvent Compositions and Buffers for Pharmaceutical Nonmetal Detection with ICP-AES and ICP-MS

Presented by John Carr of Northern Illinois University

                                                                                                                 Detection of heteroatoms such as sulfur, phosphorous, chlorine and fluorine is finding increasing importance in the pharmaceutical industry.  Pharmaceutical compounds and their associated impurities may be separated and detected using either high performance liquid chromatography or ion chromatography.  Classical detectors such as UV or mass spectrometry typically require a set of standards for each analyte to obtain accurate results as detectors responses vary for analytes of different structures.  Plasmas are a potentially excellent atom reservoir for atomic spectrometry.  Inductively coupled plasma atomic emission spectrometry (ICP-AES) and inductively coupled plasma mass spectrometry (ICP-MS) has the potential to effectively atomize the analyte allowing element specific detection while eliminating the need for standards.  However, plasma systems typically produce somewhat higher nonmetal detection limits due to the decreased ionization and excitation efficiencies of these elements.  Additionally, various LC mobile phase compositions and gradients are utilized in the separation process.   The composition of the solution can have an effect on the analytical response.  Efforts to examine and alleviate the aforementioned problems are examined utilizing membrane desolvation techniques.  A comprehensive study of the effects of various mobile phase compositions and buffers on the signal intensity of phosphomycin, a biologically active, phosphorous containing analyte is presented.  Optimization conditions and results for both ICP-AES and ICP-MS will be presented.  Comparisons of detection limits obtained for both instruments as well as signal response using various mobile phases will be highlighted.