Application of the HPLC method for benzalkonium chloride determination in aerosol preparations.

Benzalkonium chloride (BAC) is a bacteriostatic agent used in the pharmaceutical industry as a preservative. BAC is a mixture of alkylbenzyldimethylammonium chlorides, the three most important of which being those with alkyl substituents C12, C14, C16 at the quaternary ammonium salt. The purpose of this study was to develop a method for determining benzalkonium chloride identity and content in aerosol preparations in which protein or steroid hormones are the active components. The high performance liquid chromatography (HPLC) method was used for this purpose. In the performed comparison of the influence of selected factors on the process of the separation of BAC homologues, a column with packing modified with cyan groups and mobile phase containing 0.075 M acetate buffer with acetonitrile (45:55), in an isocratic elution, was used for qualitative and quantitative determinations and for method validation. The developed method may be used for the assessment of the identity and content of BAC homologues in various pharmaceutical preparations. It is simple and it does not require particular sample preparation for the tests. It is characterized by good selectivity and high precision of the determinations.

Application of high-performance size exclusion chromatography to the determination of erythropoietin in pharmaceutical preparations.

High performance size exclusion chromatography with fluorimetric detection for the determination of erythropoietin in pharmaceutical preparations has been developed. The applied chromatographic system has been enabled a quick estimation of the identity and contents of the studied compound. The method was validated and showed good validation data in terms of linearity, precision and repeatability. The validated method was successfully applied to the determination of erythropoietin content in commercially available preparations.

Determination of the content of desmopressin in pharmaceutical preparations by HPLC and validation of the method.

The aim of this study was to apply high performance liquid chromatography to the determination of content of desmopressin in pharmaceutical preparations and validation of the method. The satisfactory results have been obtained using a column Luna C 8.5 microm, 100 x 4.6 mm and a mobile phase containing 0.067 M phosphate buffer of pH = 7 and acetonitrile in the proportion 83:17. It has been shown that the elaborated method shows good precision and accuracy and can be applied to the qualitative and quantitative analysis of pharmaceutical preparations containing desmopressin.

New renin inhibitors with pseudodipeptidic units in P(1)-P(1') and P(2')-P(3') positions.

A series of four new potential renin inhibitors has been synthesized. The structure of the compounds was designed in such a way as to produce agents resistant to enzymatic degradation, metabolically stable, possibly potent and with improved oral absorption. All positions of the 8-13 fragment of the human angiotensinogen were occupied by unnatural units (two unnatural amino acids in positions P(3) and P(2) and two pseudodipeptides in positions P(1)-P(1') and P(2')-P(3')). Both N- and C-terminal functions of the inhibitors were blocked with tert-Boc and ethyl ester groups. Their hydrophobicity evaluated as a log P value, calculated by a computer method, was 6.57 and 6.08 respectively. All peptides were obtained by the carbodiimide method in solution and purified by chromatography on the SiO(2) column. Their resistance to enzymatic degradation was assayed by determination of stability against chymotrypsin activity. The potency was measured in vitro by a spectrofluorimetric method (assay of Leu-Val-Tyr-Ser released from the N-acetyltetradecapeptide substrate by renin in the presence of the inhibitor). All inhibitors were stable to chymotrypsin. Their IC(50) (M/l) values were: 9.6 x 10(-4) (12), 1.6 x 10(-5) (17), 1.0 x 10(-5) (22) and 1.0 x 10(-5) (23) respectively.