title: Determination of bis-carboxyethyl germanium sesquioxide by gas chromatography with microwave-induced plasma-atomic emission detection after derivatization with alkyl chloroformates.
abstract: Organic germanium compounds, especially Ge-132, more corrctly denoted as bis-beta-carboxyethyl germanium sesquioxide ([Ge(=O)CH2CH2CO2H]2O), are of continued interest as they are said to promote health and display anticancer activity. Although these beneficial effects have never been substantiated by comprehensive clinical studies, this drug can still be obtained through various sources and is usually marketed as a nutritional supplementation rather than an anticancer medication. As the quality standards under which this drug is produced are unknown, the need for an effective quality control of these products arises. To date, Ge-132 is considered generally as a safe compound for application in contrast to inorganic germanium which demonstrates severe renal toxicity. In this paper, a new approach to the determination of Ge-132, based on derivatization by ethyl chloroformate reagent (ECF), in the presence of ethanol and pyridine in the mixture, and subsequent analysis by gas chromatography coupled with microwave-induced plasma-atomic emission detection (GC-MIP-AED), is reported. Reaction conditions of the derivatization procedure were optimized with particular respect to the reagent (ECF) and catalyst (pyridine) concentrations. The proposed method is capable of distinguishing Ge-132 from inorganic germanium. The derivatization procedure was also tested with the use of methyl chloroformate (MCF) as alternative reagent, providing interesting additional information about the nature of the final product and the proposed reaction scheme. Among the two types of chloroformates, i.e., MCF and ECF, the latter proved to be more suitable for the proposed method, providing a calibration curve of superior sensitivity and linearity compared with the one obtained with MCF. The method was applied successfully in three real samples, two food supplements, and one commercially available fertilizer. The analysis of the Ge-132 derivative showed good linearity in the concentration of 1-250 mg L(-1) (r (2) = 0.9986) and a satisfactory precision (RSD = 6.8%), which qualifies the proposed method for the speciation analysis of Ge in various matrices.
authors.affiliation: Laboratory of Analytical Chemistry, Department of Chemistry, Aristotle University, 54124, Thessaloniki, Greece.
authors.forename: E
authors.initials: E
authors.lastname: Trikas
authors.forename: G A
authors.initials: GA
authors.lastname: Zachariadis
authors.forename: E
authors.initials: E
authors.lastname: Rosenberg