Determination of 6-amino-2,2-dimethyl-1,3-dioxepan-5-ol by postcolumn derivatization witho-phthalaldehyde/2-mercapto-ethanol after ion-pair chromatography

Summary A high-performance liquid chromatographic method is discribed for the determination of 6-amino-2,2-dimethyl-1,3-dioxepan-5-ol using Spherisorb ODS II stationary phase and mobile phase 30:70 (v/v) methanol: aqueous 1-octane sulfonic acid. Detection was fluorimetric following postcolumn derivatization with o-phthaladehyde/2-mercaptoethanol. The procedure was applied to the analysis of aqueous solutions and microcrystalline suspensions in liquid paraffin, prepared for investigation of the toxicological profile. The method was validated for selectivity, linearity of detector response, repeatability, limit of detection and quantitation. The HPLC method was selective. The instrumental limit of detection was 0.5 ng per injection (0.05 g mL^–1). The method detection limits were 0.5 g mL^–1 aqueous solution and 5 g mL^–1 liquid paraffin suspension, the quantitation limit 0.05 mg mL^–1 aqueous solution and 1.0 mg mL^–1 liquid paraffin. Linearity was within 0.94–47.1 g mL^–1. Intra-assay accuracy accounted for 99–100% in the range 0.05–226 mg mL^–1 aqueous solution, intra-assay precision for 2% (C.V.). For microcrystalline liquid paraffin suspensions with 1 and 250 mg mL^–1 99 and 109% was found for intra-assay accuracy. Intra-assay precision was 5% (C.V.). Reliable results over a wide concentration range can be obtained. The procedure is considered valid for determination of the analyte in aqueous solution or microcrystalline paraffin oil suspensions.     

Sensitive fluorescence labelling for analysis of organotin compounds with morin

Summary Analytical procedures based on reversed-phase high-performance liquid chromatography combined with post-column derivatization with morin for the determination of organotin compounds in peanut oil, water samples or diet mixtures are described. A mixture of the isooctylesters of monooctyl tin and dioctyl tin thioglycolic acid (ZK 30 434), a mixture of the isooctylesters of monododecyl tin and didodecyl tin thioglycolic acid (ZK 32 283) or dibutyl tin difluoride (ZK 38 068) had to be analysed. The data obtained from validation and during routine analysis show that the post-column derivatization with morin is a powerful tool for the selective and sensitive detection of organotin compounds in complicated matrices. Interferences of peaks related to the organotins and the matrix constituents were not found. The values of the limit of detection were 10 g ZK 30 434 or ZK 32 283/ml peanut oil, 60 ng ZK 38 068/ml water and 2.5 mg ZK 30 434/kg rodent diet mixture. Regarding to the repeatability, the methods described are characterized by values of the relative standard deviation of mostly less than 5%. In case of the determination of ZK 30 434 dissolved in peanut oil atomic absorption spectrometry was used to investigate the accuracy of the HPLC method. A good correlation between the HPLC and AAS data was found. The limits of quantitation were 0.25 mg ZK 30 434/ml peanut oil, 0.22 mg ZK 32 283/ml peanut oil and 1.0 g ZK 38 068/ml water. The analytical procedures were applied within the framework of the analytical service for validation of toxicological studies according to the guidelines of good laboratory practices (G.L.P.). Both the correct preparation of the formulations and the homogeneity or stability could be checked.