Browsing by Author "Saarelainen, Taija"

Steroid hormones are involved in many physiological functions such as stress response and the maintenance of salt-water balance and pregnancy. Concentrations of steroids in the body fluids are generally very low (below ng/ml). Steroid hormones are metabolically associated and changes in mutual concentration levels of different steroids may signify a disease. Methods that allow the measurement of various steroids simultaneously are of great importance in investigating the role of steroid metabolism for example in formation of cancer. The aim of this work was to develop a sensitive and selective method for simultaneous quantification of 16 steroids in plasma. Nano liguid chromatography-microchip electrospray ionization-tandem mass spectrometry (nanoLC-µESI-MS/MS) was used in order to achieve good sensitivity. C18 enrichment column and separation column, and an electrospray tip were integrated onto the chip that was used in this work. Mass spectrometric parameters were optimized by using a MS calibration and diagnostic chip. It was noticed that the structure of steroids plays an important role on how the compound behave in electrospray ionization. Steroids with 4,5-ene-3-one-structure had much lower limits of detection than steroids without conjugated double bonds (0,075-0,5 ng/ml and 5-25 ng/ml respectively). The chosen sample pretreatment method to extract the steroids from plasma did not work properly, because it was able to extract only a third of the compound's real concentration. Analysis of some compounds was also difficult because of the background noise coming from plasma. The method development was therefore decided to continue with eight steroids that were well detectable and had 4,5-ene-3-one-structure. The limits of detection were 0,075-0,5 ng/ml in biological matrix for these compounds. Eight knock out and seven wild type mouse plasma samples were analyzed using the validated method. The method was able to quantify aldosterone, corticosterone and androstenedione. Developed method did not meet all the aims of this work. Derivatizated compounds, different equipment or totally new method should be used in order to accomplish the aims.