Rapid determination of corticosteroids in urine by combined solid phase microextraction/liquid chromatography/mass spectrometry

Abstract

Solid-phase microextraction combined with fast short-column liquid chromatography/mass spectrometry (SPME/LC/MS) was used for isolating and analysing 11 corticosteroids and 2 steroid conjugates from urine samples. Several SPME parameters such as polarity of fibres, extraction time and effect of ionic strength, were investigated, and their impact on the SPME/LC/MS technique was studied. To demonstrate the potential of the SPME/LC/MS method, its application to the determination of steroids in human urine was investigated. The method was shown to be sensitive with detection limits between 4 and 30 ng/mL and precision between 4.9 and 11.1% RSD through the use of an internal standard technique. The versatility of the method was also exhibited by its excellent linearity in the concentration range of 20 to 20,000 ng/mL in urine for all investigated compounds. A comparison of the SPME/LC/MS method with LC/MS methods utilizing traditional sample preparation techniques, shows that the former offers similar performance in terms of precision, linearity and detection limits, but is clearly easier to use and faster to perform.

In vitro liver metabolism of aclidinium bromide in preclinical animal species and humans: Identification of the human enzymes involved in its oxidative metabolism

“…Previous data using diagnostic substrates have shown that P450 activities in rat, dog, monkey, and human hepatocyte suspensions are not significantly decreased by cryopreservation [6]. 10 and FMO3 at 0.2 mg of protein/ml. Protein concentration in recombinant human P450 incubations was normalized (0.25 mg/ml) using insect control protein, without esterase and P450 activity.…”

Mass spectrometric assay and physiological–pharmacological activity of androgenic neurosteroids

“…Steroids have been commonly analyzed using liquidliquid extraction and either ECNCI-LC/MS/MS or APCI-LC/MS/MS modes (Griffiths et al, 1999;Kim et al, 2000;Kobayashi et al, 1993;Fredline et al, 1997;Vallee et al, 2000). Influence of eluent composition on ionization efficiency has been extensively studied (Volmer and Hui, 1997).…”

Adduct formation of steroids in APCI and its relation to structure identification

“…Adduct ions of acetic or formic acid with analyte present in the negative ion mass spectra have been reported before [8,9]. Although the DE have been calculated for positive charged adduct ions [6], it can be argued that the abundance of acetate adduct ions, -is also related to the dissociation bond energy, and thus the proton affinity, of the bonded molecules [10].…”

“…1 for a general structure and the numbering of the C atoms) in the negative ion mode. Abundant adduct ions for these type of molecules have been reported both with the thermospray [7] as with the HN [8,9] interface. These types of compounds are chosen because the MSMS data are considered hard to interpret [15].…”