Detection and identification of medically important alkaloids using the surface-enhanced Raman scattering spectroscopy.

Currently, trace detection of drugs, medicinal products, psychoactive substances, poisons and other natural or synthetic compounds in the human body has become one of the most important areas of interest in medicine, toxicology and forensic research. Due to the rapid development of nanotechnology, applications in forensic and biological sciences, food industry and art preservation there is an increasing interest in surface-enhanced Raman scattering (SERS) spectroscopy as a technique capable of low detection limits in the analysis of small amounts of studied analytes. In this study, different excitation wavelengths (785 nm and 1064 nm) were used to find the appropriate experimental conditions for the detection and identification of medically significant alkaloids - atropine and pergolide - by means of surface-enhanced Raman scattering spectroscopy. SERS spectra of selected alkaloids were measured in the concentration range 10-3-10-9 mol∙L-1 using large-scaled platinum substrates coated with electrochemically prepared gold or silver SERS-active layers. Identification was based on the assignment of surface-enhanced characteristic vibrational bands using theoretical (DFT) calculations and comparing them with normal (non-enhanced) Raman spectra of pure compounds. All sets of spectral data were subjected to multivariate statistical approach (partial least squares regression) aiming at prediction of alkaloids concentration in developed models and its comparison with experimental results.

The analysis of pergolide residues in horse plasma by LC with fluorescence detection.

Pergolide is used to treat pituitary pars intermedia dysfunction (equine Cushing's Disease), a neurodegenerative condition associated with loss of dopaminergic inhibition of the pituitary in horses. After oral administration, only low concentrations of the drug are achieved in plasma, making drug detection and quantification difficult. While direct analysis of plasma using sensitive MS/MS techniques is possible, dirty plasma samples and mobile phase buffers can cause instrumentation to become rapidly incapacitated. A method using LC with fluorescence detection was developed for pergolide analysis. LOQ for the instrumentation was 2 ng/mL when using direct injection of horse plasma samples, while interferences from the matrix were nominal. The use of SPE provided cleaner extracts and increased the LOQ in plasma samples to 0.15 ng/mL. The LC method developed allowed high sample throughput before pre-columns required replacement, which was extended when SPE cleanup was used. The effectiveness of SPE for the cleanup and preconcentration of plasma samples containing pergolide was demonstrated with spiked and naturally incurred samples; LC-MS/MS was used to validate the SPE method against direct injection samples.

Improved photostability indicating ion-pair chromatography method for pergolide analysis in tablets and in the presence of cyclodextrins.

Pergolide (PG) a semi-synthetic ergot alkaloid derivative used mainly for the treatment of Parkinson's disease is known to be a photosensitive drug substance. The major photodegradation products are PG sulphoxide (SX) and PG sulphone (SN), which are also the main impurities of the bulk drug substance. It is widely metabolized to more than 10 metabolites including SX and SN. In this work an improved photostability indicating ion-pair chromatography method for PG mesilate was developed. The method can be applied in the determination of PG and impurities in aqueous solutions and in tablets for routine analysis. This new method is appropriate for the quantitative determination of PG in the presence of its impurities and photodegradation products and can also be used for PG complexes with cyclodextrins (commonly used as photostabilizing agents). Furthermore it is suitable for the quantitation of its impurities and its thermal or photo-induced decomposition products. Separation was achieved on a ThermoQuest C(18) BDS column and Sodium octanosulphonate was used as ion-pairing agent. Analysis was performed at 223 nm. Validation parameters included: specificity, linearity, precision and accuracy, limit of quantitation and suitability. The method was found to be specific and linear for PG, as well as for SX and, SN impurities. The recovery was 100.83+/-0.46% for PG, 99.86+/-0.33% for SX and 99.77+/-1.84% for SN. Finally the photodegradation profile of PG mesilate was studied in different initial sample concentration. The obtained result revealed that: PG photolysis is catalyzed by its degradation products and that decrease of initial sample concentration reduces the rate of PG photoinduced degradation.