Um novo método para determinação simultânea de íons paládio, platina e ródio, como quelatos metal-DHBTR foi desenvolvido. Os íons paládio, platina e ródio foram derivatizados (pré-coluna) com 2,4-dihidroxibenzilidenotiorodanina (DHBTR) para formar quelatos coloridos. Os quelatos Pd-DHBTR, Pt-DHBTR e Rh-DHBTR são absorvidos na coluna de enriquecimento, quando injetados e transportados por uma fase móvel composta por solução tampão de ácido acético-acetato de sódio 0,05 mol L -1 (pH 3,5). Após o término do enriquecimento, ao acionar uma válvula de seis vias, os quelatos retidos foram carregados pela fase móvel, para a coluna analítica. A separação dos quelatos na coluna analítica foi satisfatória com acetonitrila 62% (v/ v) (contendo solução tampão de ácido acético-acetato de sódio (0,05 mol L -1 , pH 3,5) e 0,1% (m/v) de tritonX-100) como fase móvel. Os limites de detecção de paládio, platina e ródio são 3,6 ng L -1 , 3,2 ng L -1 e 4,5 ng L -1 , respectivamente. Este método foi aplicado para a determinação de paládio, platina e ródio em água, urina e amostras de solo, com bons resultados.A new method for the simultaneous determination of palladium, platinum and rhodium ions as metal-DHBTR chelates was developed. The palladium, platinum and rhodium ions were pre-column derivatized with 2,4-dihydroxybenzylidenethiorhodanine (DHBTR) to form colored chelates. The Pd-DHBTR, Pt-DHBTR and Rh-DHBTR chelates can be absorbed onto the front of the enrichment column when they were injected into the injector and sent to the enrichment column with a 0.05 mol L -1 sodium acetate-acetic acid buffer solution (pH 3.5) as mobile phase. After the enrichment had finished, by switching the six ports switching valve, the retained chelates were back-flushed by mobile phase and traveling towards the analytical column. These chelates separation on the analytical column was satisfactory with 62% (v/v) acetonitrile (containing 0.05 mol L -1 of pH 3.5 sodium acetate-acetic acid buffer salt and 0.1% (m/v) of tritonX-100) as mobile phase. The Limits of detection of palladium, platinum and rhodium are 3.6 ng L , respectively. This method was applied to the determination of palladium, platinum and rhodium in water, urine and soil samples with good results.Keywords: palladium, platinum, rhodium, 2,4-dihydroxybenzylidenethiorhodanine, high performance liquid chromatography, on-line enrichment IntroductionEnvironmental contamination by the platinum group elements (PGEs), mainly related to automotive catalytic converters, is exponentially increasing and reliable and accurate quantification is a mandatory task. [1][2][3][4] The wide use of palladium, platinum and rhodium not only in automotive catalytic converters but as a drug (Pt) and in food production (Pd) 5 has led to a more uncontrolled release of those metals in the environment, with respect to the one due to the traditional chemical industry. Moreover, the platinum group elements derived from automotive catalytic converters are released as nanocrystallites (particles with less than 3 mm in ...

A new stability-indicating RP-HPLC assay method was developed and validated for quantitative determination of loteprednol etabonate in bulk drugs and in ophthalmic suspensions in the presence of degradation products generated from forced degradation studies. The system consisted of Agilent Technologies Zorbax Eclipse XDB-Phenyl 5 µm 4.6 × 250 mm, and detection was performed at 244 nm. The mobile phase consisted of water-acetonitrile-acetic acid (34.5:65.0:0.5, v/v/v) run at a flow rate of 1 mL/min and maintained at room temperature. The calibration curve was linear from 30 to 70 µg/mL with r > 0.999. Accuracy (mean recovery 100.78%) and precision were found to be satisfactory. Stress conditions including acid and alkali hydrolysis, water stress, oxidation, photolysis and heat were applied. The degradation products did not interfere with the detection of loteprednol etabonate, thus the method can be considered as a stability-indicating method. The proposed method can be used for quality control assay of loteprednol etabonate in bulk drug and in ophthalmic suspensions and for stability studies as a result of the ability of the method to separate loteprednol etabonate from its degradation products and excipients.

Diclofenac potassium is an anti-inflammatory agent classified as a class II drug as per the biopharmaceutical classification system (BCS). The poor dissolution rate of water-insoluble drugs is still a major problem confronting the pharmaceutical industry. There are several techniques to enhance the dissolution of poorly soluble drugs. Methods available include salt formation, micronization and addition of solvent or surface active agents. The objective of the present work is to improve the dissolution profile of diclofenac potassium by formation of a physical mixture and a solid dispersion with mannitol. The solid dispersion was prepared by solvent method using ethanol/water. As diclofenac potassium melts with decomposition, the compatibility study with mannitol was done with the acid form by differential scanning calorimetry (DSC). The dissolution properties and physicochemical properties of diclofenac potassium:mannitol physical mixture and solid dispersion were investigated by Powder X-ray Diffraction (PXRD), Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM) and dissolution test. This study shows that the dissolution rate of diclofenac potassium can be enhanced considerably by formulating it with mannitol, as a physical mixture or as a solid dispersion although crystallinity was maintained.

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