Identification and prevention of Staphylococcus aureus-caused infections may benefit from a fast and dependable method to distinguish between the methicillin-resistant (MRSA) and methicillin-susceptible (MSSA) S. aureus strains. The current methods involving polymerase chain reaction and/or other molecular tests are usually laborious and time-consuming. We describe here a fast and low-cost method employing capillary zone electrophoresis (CZE) to distinguish between MRSA and MSSA. The method makes use of a supercritical water-treated fused silica capillary, the inner surface of which has subsequently been modified with (3-glycidyloxypropyl)trimethoxysilane. With optimized proportions of suitable additives to the background electrolyte, a CZE separation of MRSA from MSSA may be completed within 12 min. The cells were baseline-resolved, and resolution was determined to be 3.61. The isoelectric points of MSSA and MRSA were found to be the same for both groups of these strains, pI = 3.4.
Pressurised fluid extraction using water or methanol was employed for the extraction of stevioside from Stevia rebaudiana Bertoni. The extraction method was optimised in terms of temperature and duration of the static or the dynamic step. Extracts were analysed by liquid chromatography followed by UV and mass-spectrometric (MS) detections. Thermal degradation of stevioside was the same in both solvents within the range 70-160 degrees C. Methanol showed better extraction ability for isolation of stevioside from Stevia rebaudiana leaves than water within the range 110-160 degrees C. However, water represents the green alternative to methanol. The limit of detection of stevioside in the extract analysed was 30 ng for UV detection and 2 ng for MS detection.
