Ion-pair extraction and precipitation methods for ethambutol determination

Determination of ethambutol by a sensitive fluorescent probe

The competitive reaction between ethambutol and two fluorescent probes (i.e., berberine and palmatine) for occupancy of the cucurbit[7]uril (CB[7]) cavity was studied by spectrofluorometry. The CB[7] reacts with these probes to form stable complexes, and the fluorescence intensity of the complexes is greatly enhanced. In addition, the excitation and emission wavelengths of their complexes moved to wavelengths of 343 nm and 495 nm, respectively. However, the addition of ethambutol dramatically quenches the fluorescence intensity of the two complexes. Accordingly, a couple of new fluorescence quenching methods for the determination of ethambutol were established. The methods can be applied for quantifying ethambutol. A linear relationship between the fluorescence quenching values (ΔF) and ethambutol concentration exists in the range of 5.0-1000.0 ng mL(-1), with a correlation coefficient (r) of 0.9997. The detection limit is 1.7 ng mL(-1). The fluorescent probe of berberine has higher sensitivity than palmatine. This paper also discusses the mechanism of fluorescence indicator probes.

Spectrophotometric determination of some pharmaceutical amides through charge-transfer complexation reactions

A spectrophotometric method is described for the assay of fenpipramide hydrochloride, isopropamide iodide, trimethobenzamide hydrochloride, morphazinamide hydrochloride and tolazamide. The method is based on the formation of a charge-transfer complex between the drug as n-donor and iodine, a sigma-acceptor. The product exhibits absorption maxima at 295 and 365 nm; measurements are made at 365 nm for fenpipramide and at 295 nm for the other compounds. Beer's law is obeyed in a concentration range of 1-120 micrograms ml-1. The method is rapid, simple and sensitive and can be applied to the analysis of some commercial and laboratory prepared tablets without interference. A more detailed investigation of the complex was made with respect to its composition, association constant and free energy change.

Chromatographic analysis of antituberculosis drugs in biological samples

Numerous chromatographic and non-chromatographic methods of analysis for anti-tuberculosis drugs and metabolites in biological tissues have been discussed in this review. Depending upon the analytical methodology selected, limits of detection range from microgram to picogram levels. A number of examples have been given of the correlation between different types of assay procedures. The metabolism and pharmacokinetics have been described along with some of the commonly associated problems of sample collection and storage.

Determination of hematoporphyrin and protoporphyrin by ion-pair extraction with chlorpromazine

A sensitive method based on ion-pair extraction is described for the quantification of hematoporphyrin and protoporphyrin using chlorpromazine as an ion-pair-forming agent. Extraction of the ion-pair in chloroform is obtained quickly at an optimum pH of 6.5 for hematoporphyrin and 6.5-6.8 for protoporphyrin, giving an excellent recovery of the porphyrin. A stoichiometric relationship of 1:2 between porphyrin and chlorpromazine is proved. Cyanocobalamin and liver extract do not interfere with the assay.

Sensitive assay procedure for ethambutol hydrochloride via charge transfer complex formation

The charge transfer complex formation between ethambutol and iodine was investigated and utilized as the basis for a sensitive spectrophotometric procedure for ethambutol and its dosage forms. The solutions exhibited blue-shifted iodine bands at 293 and 360 nm. A Job's plot of corrected absorbance against the mole ratio of ethambutol to iodine indicated a 1:2 drug-iodine ratio. At 293 nm, the absorbance was linear (r=0.9998) over the 0.25-15-microgram/ml concentration range, but the concentration range for best accuracy is 1.6-5.8 microgram/ml. The method can be applied successfully to the analysis of commercially available ethambutol tablets.