Off-line CE/MALDI MS: Sampling and deposition techniques to incorporate complementary analyses for cellular assays

An on-going request, or demand, on analytical chemists is to get more information from less and less sample. This need for improved instrumentation is observed in the research on the central nervous system (CNS). Here, many cells have discrete identities and functions, and this requires analytical techniques that are capable of chemically identifying the contents of single neurons. By detecting what neurotransmitters individual neurons use in cellular communication, a better understanding of the origins of thought, learning, and behavior is achieved. New coupling and sampling techniques are developed that efficiently combine capillary electrophoresis (CE) and matrix-assisted laser desorption/ionization mass spectrometry (MALDI MS) and enable nanovial injections. These techniques facilitate sensitive detection, provide for the incorporation of complementary detections, and allow mass-limited analyses on the neuropeptides contained in single cells.; As single analytical techniques can be incapable of completely profiling a sample, it is advantageous to combine complementary methods to increase the amount of information obtained. The coupling of the microseparation ability of CE with the information-rich detection of MALDI MS provides for a powerful, two-dimensional analytical method capable of assaying the neuropeptides expressed by single neurons. Central to this technique is the designing of a nanoliter volume fraction collection system and the engineering of a nanovial injection apparatus. These two techniques allow for mass-limited analyses by (1) introducing a large portion of the limited sample into the instrument for analysis and (2) depositing the separated analytes directly onto a MALDI target in nanoliters of matrix solution improving the sensitivity of MS detection.; The viability of this CE/MS method is demonstrated by the chemical profiling of tissues and single cells from the marine mollusc, Aplysia californica , assaying neuronal release, analyzing cone snail venoms, and incorporating radionuclide detection with CE/MALDI MS. The application of the CE/MS technique toward the analysis of these samples shows that this method is capable of analyzing the neuropeptides in single neurons, and it is also amendable to a wide variety of other areas where there is need to get more information from mass-limited samples.