Browsing by Subject "bioanalysis"

Sort by: Order: Results:

Now showing items 1-3 of 3
  • Lindfors, Pia (Helsingfors universitet, 2010)
    The most important part in bioanalysis is the sample cleanup process which is usually the most laborious and time consuming part of the analysis and very susceptible to errors. A functional bioanalysis has to be quick, easily automated, sensitive, selective and stable. It also needs to be suitable for high throughput analysis. Desorption atmospheric pressure photoionization (DAPPI) is a novel direct desorption/ionization technique for mass spectrometry that enables direct analysis of solids from surfaces or liquid samples from a suitable sample plate often without any sample preparation. The suitability of DAPPI-MS for biological samples was investigated by measuring the limits of detection for selected opioids and benzodiazepines and screening them from authentic urine samples. Limits of detection were measured for standard solutions and spiked urine. Opioids and benzodiazepines were analyzed from post mortem urine samples with an optimized DAPPI-MS method. Post mortem urine samples were analyzed with and without sample preparation. Sample preparation improved the sensitivity of the method remarkably. About 50 % of the analytes were detected without sample preparation and almost 100 % after sample cleanup. It is however difficult to estimate the suitability of DAPPI-MS as a screening method because not all analyte concentrations of the urine samples were known. Therefore we cannot be certain weither the results obtained without sample preparation are caused by the suppression of the urine matrix or if the concentrations of the analytes are below the limits of detection. The reliability of the method can further be improved by investigating the metabolites of the analytes and improving the system towards automation. On grounds of this research DAPPI-MS should be used cautiously as a screening method for urine samples without sample preparation and with only high enough analyte concentrations. DAPPI-MS shows promise as a screening method for opioids and benzodiazepines from urine when the sample cleanup is used before the analysis.
  • Turunen, Anna (University of Helsinki, 1995)
  • Mäntylä, Natalia (Helsingin yliopisto, 2021)
    The literature part of the thesis focused on reviewing published LC–MS/MS methods for cardiovascular drugs in biological matrices. Emphasis was given to the used sample preparation procedures and usability in different types of analyses, and their effects to the performances of the whole methods. Published methods for cardiovascular drugs in biological matrixes from the last decade were reviewed and presented. Insight into the challenges biological matrixes present was given, as well as a short overview of cardiovascular drugs. Plasma and urine were the most common sample matrixes, but some methods have also been published for serum and whole blood, and one even for fat tissue. Development and basic principles of liquid chromatography and mass spectrometry were presented, focusing on high and ultra-high performance liquid chromatography (HPLC and UHPLC) and triple quadrupole tandem mass spectrometry (QqQ–MS), as these seemed to be prevalent industry standard. Of sample preparation techniques, protein precipitation, direct dilution, liquid–liquid extraction (LLE), solid-phase extraction (SPE) and turbulent flow chromatography (TFC) were covered, with additions of some miniaturized versions. Some newer miniaturized online techniques have successfully been utilized for cardiovascular drug analysis, and their popularity will likely increase as the hardware in laboratories gets more and more modern. Advances in sample preparation techniques were relatively mild during the decade covered in this review, despite the significant proportion cardiovascular drugs hold in used medications. Newly published methods were either quantitative for a handful of analytes, or qualitative screenings for several analytes, some of which are cardiovascular drugs. Plasma and urine samples were used almost exclusively. In addition to the literary review, an experimental study was done at THL, where a LC–MS/MS method was successfully developed and validated during 2018–2019. The method has been used since 2019 as the primary qualitative method in cause–of–death investigations for 55 cardiovascular drugs analysed from post-mortem whole blood samples. In light of the done review, this method is exceptionally comprehensive regarding included analytes, and could potentially be at least partially automated with suitable instruments