The use of 2,3-dichloro-5,6-dicyano-p-benzoquinone for the spectrophotometric determination of some cardiovascular drugs

Determination of hydralazine with flow injection chemiluminescence sensor using molecularly imprinted polymer as recognition element

A novel flow injection chemiluminescence (CL) sensor for hydralazine determination using molecularly imprinted polymer (MIP) as recognition element is reported. Hydralazine-MIP was prepared through non-covalent copolymerization using methacrylic acid (MAA) monomer, hydralazine template and ethylene glycol dimethacrylate (EGDMA) cross-linker. Particles of the MIP were packed into a v-shape glass tube for on-line adsorption of the analyte of hydralazine. The adsorbed hydralazine could be sensed by its great enhancing effect on the CL reaction between luminol and periodate. The CL intensity is linear to hydralazine concentration in the range from 2x10(-9) to 8x10(-7) g/mL. The detection limit is 6x10(-10) g/mL (3sigma) and the relative standard deviation is 2.8% (n=7) for 8x10(-9) g/mL hydralazine. The selective experiment showed that the selectivity and sensitivity of the CL method could be greatly improved when MIP was used as recognition element in the flow-injection CL sensor. The sensor was reversible and reusable. It could be used for more than 100 times. It has been used directly to determine the hydralazine in human urine.

Time-resolved chemiluminescent analysis of hydralazine in pharmaceuticals

A new analytical method is proposed for determination of hydralazine (HZ) in pharmaceuticals--measurement of the chemiluminescence (CL) emitted after reaction with phosphoric-acidified KMnO4. The novelty of this method is the recording of the whole CL-time profile. Such a recording is possible by use of a CL-detector operating in tandem which enables the reactants to be mixed in the measurement cell only and, therefore, the CL is reaction monitored from beginning. At the precise time the pump is stopped signal recording is triggered and so CL evolution is recorded completely. The optimum chemical conditions for the determination were 0.8 mol L(-1) formaldehyde, 0.3 mmol L(-1) KMnO4, 4.0 mol L(-1) H3PO4, and a total flow of 0.37 mL s(-1). Two calibration graphs were plotted, CL intensity and area under the profile curve against HZ concentration. Exhaustive statistical analysis provided very interesting results, for example, accordance with Clayton's theory, detection limit below 0.2 microg mL(-1), and linear calibration ranges from 0.2 to 5.0 microg mL(-1). This method was successfully applied to the determination of HZ in pharmaceuticals. Because they are usually formulated in association with diuretics and beta-blockers, the method was used for analysis of HZ in pharmaceuticals that contained either HZ only or HZ with other hypotensive substances. Obtained and nominal content were approximately the same and experimental Student t values indicated there were no significant differences between the values.

Determination of dipyridamole in pharmaceutical preparations using square wave voltammetry

An analytical methodology using square wave voltammetry (SWV) at a hanging mercury drop electrode (HMDE) was developed for the quantitative determination of dipyridamole (DIP), a drug used for the treatment of several cardiovascular diseases, in pharmaceutical tablets and injections of Persantin in phosphate buffer (pH 3.0; 0.1M). After optimization of the parameters for SWV, analytical curves were obtained for application in the range of 1.28 x 10(-6)M to 7.02 x 10(-6)M. It was found a detection limit (DL) of 1.88 x 10(-8)M (9.50 ng/ml). The repeatability and the reproducibility of the method were determinated by successive measurements of DIP solutions on the range of the analytical curve with a coefficient variation of 0.97% (n=5) and 1.15%, respectively. The apparent recoveries were obtained by the IUPAC recommended procedure using the second reduction peak. Recoveries obtained by SWV were compared with the UV-vis spectrophotometric method. It was found that the determination of DIP in Persantin tablets gave a mean value of 75.6+/-0.4 mg (100.8%) and 68.9+/-0.3 mg (91.8%) for SWV and UV-vis spectrophotometry, respectively. In the case of injections, it was found 10.4+/-0.1 mg (103.4%) and 9.9+/-0.2 mg (99.9%) for SWV and UV-vis spectrophotometry. Both apparent recoveries for the two types of formulations are in good accordance with the declared value of 75 mg (tablets) and 10 mg (injections).

Fluorescence spectroscopic determination of dipyridamole binding on pancreas-1 tumor cell membrane

BACKGROUND

The traditional method to determine the binding sites of inhibitors bound to nucleoside transporters on cell membrane is the radioactive assay. This method suffers from radiolabel instability and the need to dispose of reactive materials. Fluorescence spectroscopy has been increasingly applied to biochemical analysis due to its high sensitivity and selectivity. We describe fluorescence spectroscopy for the determination of the binding sites of dipyridamole bound to nucleoside transporters on pancreas-1 tumor cell membrane.

METHODS

Pancreas-1 tumor cell was cultured in Dulbecco's modified Eagle medium under appropriate conditions. The cell plasma membrane was separated from the ultrasonically dissolved cell mixture by gradient centrifugation. After dipyridamole was bound to the cell membrane, the test sample was obtained by ultrasonically dissolving the labeled membrane in 10 mmol/l tris-HCl membrane lysis solution. Under selected experimental conditions, the fluorescence intensity of dipyridamole was determined.

RESULTS

At lambda em of 295 nm and lambda em of 485 nm, dipyridamole was proportional to its concentration ranging from 1.0 x 10(-12) to 5.0 x 10(-11) mol/l with a detection limit of 2.8 x 10(-13) mol/l (0.14 pg/ml) at 3sigma. The value of affinity constant of the cell membrane to dipyridamole was 4.7(+/-0.5) x 10(10) l/mol and the average total number of binding sites of a pancreas-1 tumor cell was 1.9(+/-0.2) x 10(6).

CONCLUSIONS

The proposed method can be used in the study of binding characters of dipyridamole on the cell membrane.