A rapid, sensitive and reproducible HPLC method has been developed for enantioseparation of six non-steroidal anti-inflammatory drugs, which are acidic compounds: carprofen, fenoprofen, flurbiprofen, ibuprofen, indoprofen and ketoprofen. The effects of the mobile PHASE composition on retention times and resolutions of the analytes were studied. A column based on vancomycin immobilized by reductive amination to aldehyde functionalised silica was prepared in house and used. The prepared sorbent shows a great stability and selectivity over a range of pH (4-6), and the separation was carried out using the mobile PHASE composed of a mixture of 40 % of methanol in ammonium nitrate buffer (50 mM) at pH 5.0. Another mobile PHASE consisted of 50 % of methanol in phosphate buffer (5 mM) at pH 5.0 was also prepared and tested. The two mobile PHASEs are the optimum conditions obtained. All experiments were conducted at flow rate 0.6 ml/min, using a UV detector wavelength at l=254 nm.

The high performance liquid chromatography (HPLC) enantioseparation of four b-blocking agents metoprolol, bisoprolol, propranolol and atenolol was performed on amylose tris- (3, 5- dimethylphenylcarbamate) chiral STATIONARY PHASE using n-hexane-ethanol-diethylamine (DEA) as the mobile PHASE and related chiral recognition mechanisms were discussed. Enantiomeric separation of the four b-blockers was a result of more than one type of interaction between solutes and CSP. Besides hydrogen bonding, there was another type interaction that was independent of solvent polarity and responsible for enantiomeric selectivity, such as p-p interactions. Both the groups close to the chiral centers and the substituent groups on the phenyl rings, which were far away from the chiral centers, could contribute to the good separation. The separations of the four b-blocker enantiomers were all enthalpy driven process. In the range of 293–308K (20–35 oC), as the temperature increased, the retention as well as the resolution decreased. The molecular size rather than concentration of the alcohol modifiers affected the resolution and retention.

The search for new STATIONARY PHASEs has been one of the predominant concerns in high performance liquid chromatography (HPLC) in order to achieve better resolutions, longer column lives, and reduce the time of analysis. A chromatographic packing for separation of underivatized amino acids (AAs) were prepared by dynamically coating 2-amino tetraphenylporphyrin (atpp) on a C-18 reversed-PHASE packing and its properties were examined. The retention characteristics of 20 AAs forming the building blocks of proteins were investigated on the atpp coated C-18 column at pH 7. Results obtained seem to confirm a mixed mechanism of retention involving the hydrophobic interaction between the aromatic porphyrin macrocycle and some of the AAs, pi-pi interaction between the IT-electrons of the porphyrin macrocycle and the;pi-electrons of analyte, and the hydrogen bonding interactions between AAs and the porphyrin nitrogens.

Grid-tied Neutral-Point-Clamped (NPC) inverters have been widely used in various applications recently. A superior control method is required to achieve the desired performance of a grid-connected NPC inverter. Accordingly, a second-order sliding mode control (SOSMC) method, which is designed in the STATIONARY frame, is utilized for achieving this aim in this paper. The super-twisting second-order sliding mode control is used for solving the chattering problem of conventional first-order sliding mode control (FOSMC). In comparison to control methods which are applied in rotation frame, this method is not required transformation from rotating frame to a-b-c frame and vice versa and decoupling of d and q components. The Lyapunov stability analysis is used for designing of this controller. The performance of proposed method is evaluated by simulation results implemented in MATLAB/Simulink software. The performance of the SOSMC is also compared with FOSMC. The results show that the incorporation of SOSMC can improve current reference tracking of the NPC inverter in different scenarios.