Method development for the analysis of complex samples with inductively coupled plasma mass spectrometry

Abstract: In this thesis the development of methods for handling the problems associated with analyzing trace elements in complex matrixes using inductively coupled plasma mass spectrometry is presented. Trace elements such as Cu, Fe, Se, and Zn, to name a few, do play important roles in different organisms. Therefore it can be of importance to study trace elements in different samples of biological origin. As trace elements are low in abundance, sensitive instrumental techniques such as inductively coupled plasma mass spectrometry (ICP-MS) are required for accurate determination. Due to the complexity of samples with biological origin, careful method development, both regarding the sample preparation and instrumental analysis has to be performed to minimize negative effects on the instrument signal and introduction of interferences.For example the metal contents of mink livers were analyzed, after bomb digestion to investigate if the metal concentration could be linked to changes in the organ morphology as well as the minks’ environment. Morphological changes and capture locations could be linked to the metals investigated. The investigation of the elemental composition of cerebrospinal fluid from chronic pain patients using spinal cord stimulation electrode treatment on the other hand required less harsh sample treatment. No correlation between the spinal cord stimulation and element concentration could be found, but differences between patients and the control group were presented hinting that chronic pain intrinsically could affect the cerebrospinal fluid metal concentration. Another bodily fluid of interest is saliva and the use of paperpoint sticks as a sampling technique for Ti in saliva was investigated. As Ti is interfered by several components expected to be found in saliva, the use of reaction or collision gas was also investigated to reduce the effects of interferences. Simple leaching of the paperpoint sticks together with complexing the Ti with NH3 as reaction gas was shown to be optimal. Finally, how the selection of internal standard would be affected by the use of reaction and collision gases was also investigated. With collision gas most internal standards worked fine, while for reaction gas internal standard selection was harder. For elements with high ionization energy such as As, Se and Zn the choice of internal standard was very dependent on matrix. While ICP-MS suffers from problems when analyzing samples with complex matrixes many of them can be minimized by proper method development as shown in this thesis.