Capillary electroseparations with mass spectrometric detection Nanoparticle-based continuous full filling and applications for complex sample matrices

Sammanfattning: One of the major challenges in analytical chemistry is to find techniques and methods for determinations of low abundance compounds in complex sample matrices. This thesis describes the development of new miniaturised analytical techniques comprising capillary electroseparation combined with mass spectrometric detection. The techniques are rapid, sensitive, efficient, and suitable even for analytes appearing in complex matrices. In the work described, all aspects of analysis, from sample work-up to separation to detection, have been investigated. A novel capillary electrochromatographic technique, the continuous full filling technique, was developed. In continuous full filling capillary electrochromatography (CFF-CEC), a suspension of polymeric nanoparticles in electrolyte is employed as a pseudostationary phase (a moving interaction phase). Excellent electrochromatographic performance and stable suspensions of nanoparticles were obtained over a wide range of electrolyte compositions and properties, and over time. This makes the technique general, robust and useful for reversed phase and ion-exchange chromatographic applications. Good repeatability (between consecutive runs), good reproducibility (between nanoparticle batches) and excellent separation efficiencies with more than one million theoretical plates per meter, were achieved for reversed phase separations. The continuous replacement of the nanoparticles throughout the CFF-CEC separation minimises memory effects and strongly reduces the risk of clogging the separation capillary. As a result, the CFF-CEC technique has high potential in analyses involving complex sample matrices. Due to the continuous elution of nanoparticles from the separation capillary, an orthogonal electrospray ionisation interface to the mass spectrometer was employed. This was an efficient means of allowing analyte ions to be accelerated into the mass spectrometer for detection, while the much more massive nanoparticles go to waste. Thus, sensitive detection with no suppression of the analyte signals or instrument contamination from the nanoparticles was achieved, which is another major advantage of the CFF-CEC technique. A different technique was developed comprising on-line coupling of in-capillary micro solid-phase extraction, capillary electrophoresis and nanoelectrospray tandem mass spectrometric detection. This capillary-based technique was employed for quantification of a carcinogenic food-derived heterocyclic aromatic amine (PhIP) at low concentrations in human urine. Despite the complex nature of the urine matrix, PhIP was quantified with high repeatability, both between consecutive analyses and between analyses carried out on different days. To obtain stable and sensitive nanoelectrospray mass spectrometric detection, a durable and inexpensive device was prepared for (i) attaching the nanospray emitter to the separation capillary and (ii) connecting the spray-voltage. The combination of short analysis times, automated procedures, and high durability of the capillary-based system should make the described analysis system very useful for reliable daily screening of numerous samples with complex matrices.