Lipid model systems consisting of the major components of the stratum corneum intercellular lipid matrix were studied to investigate the ultraviolet-radiation-mediated damage of these biomolecules. Pure lipids and liposomes were irradiated using a lamp emitting a solar radiation spectrum. The influences of the irradiation and the effects of added iron ions were studied by electrospray ionization mass spectrometry (MS) with an ion trap analyser. Exact mass measurements were carried out using a time-of-flight mass spectrometer. Only linolenic acid and cholesterol were found to be subject to oxidative changes caused by UV irradiation whereas the other lipids examined (dipalmitoylphosphatidylcholine, ceramide III and cholesterol sulphate) were stable to oxidative stress. Several lipid adducts were observed upon analysis of the liposomes. The composition of these adducts was identified by MS/MS experiments.

A sensitive and selective method for the quantification of mycophenolate mofetil and its active metabolite mycophenolic acid in different human skin layers after dermal administration is presented. The skin layers were separated after in vitro penetration experiments and a methanolic extraction was performed. Positive ion electrospray HPLC-MS in selected ion monitoring mode was used to quantify the substances after isocratic separation by a C18 analytical column. The minimum detectable concentrations were 850 pg/ml for MMF and 1 ng/ml for MPA. The peak areas depended linearly on the concentration of both drugs over the range of 25-1,000 ng/ml (r2 > or = 0.996) with accuracy < or =9.8% and precision < or = 13.2%. Total imprecision at quantification limits was 15.2% at 10 ng/ml and 16.3% at 1,500 ng/ml for MMF and 15.1% at 21.0 ng/ml and 17.5% at 1,300 ng/ml for MPA. This HPLC-MS method will be applicable to the profiling of MMF amounts in skin and its conversion to MPA after application of different formulations.

The amount of hyaluronan (HA) in pharmaceutical formulations was determined by high-performance capillary electrophoresis (HPCE) and the results were compared with the carbazole reaction established by Bitter and Muir (T. Bitter, H.M. Muir, Anal. Biochem. 4 (1962) 330-334), HA analysis was performed in less than 10 min by using an untreated fused silica capillary with bubble detection cell. The influence of several buffers and pH values was examined. Calibration curve shows good linearity from 0.01 to 5.0 mg/ml. The lower limit of detection by monitoring the absorbance at 195 nm was 10 microg/ml at a signal to noise ratio of 5.