Determination of alcohols in alcoholic beverages by micro high-performance liquid chromatography with indirect photometric detection

Direct Methanol Catalytic Fuel Cell, for Measuring Ethanol Contents in Pharmaceutical Tinctures

Background:

In order to test real direct applicability for analytical purposes, a small and simple direct methanol (or ethanol) catalytic, enzymatic or non-enzymatic fuel cell (DMFC) was used for the analysis of ethanol-based pharmaceutical tinctures; a detailed experimental study was conducted on five different pharmaceutical tinctures available at drugstores.

Results:

The results obtained using both enzymatic and non-enzymatic devices were compared with those obtained by analyzing the same pharmaceutical samples with a conventional catalase biosensor. Finally, the results were compared with the nominal values provided by manufacturing firms.

Conclusion:

The correlations between the different experimental and nominal values considered were good in general or satisfactory and the applied statistical tests (f-test and t-test) were also very comforting. At the end of the study, the use of enzymatic DMFC proved to be better than non- enzymatic DMFC devices, because it requires shorter analysis times.

On the Accuracy of In Vivo Ethanol and Acetaldehyde Monitoring, a Key Tile in the Puzzle of Acetaldehyde as a Neuroactive Agent

Over the last 20 years researchers have explored the postulated role of acetaldehyde (ACD) as a mediator of some of the actions of ethanol (EtOH) in the central nervous system (CNS). However, efforts have been hampered mainly by the difficulty of directly measuring in vivo EtOH and ACD levels in the CNS and thus, our knowledge is based on indirect evidences. Although technically challenging, the development of reliable methods for in vivo measurement of ACD and EtOH is of paramount importance to solve the “puzzle of acetaldehyde as a neuroactive agent.” In this short review we discuss the recent advances on brain EtOH pharmacokinetic and state-of-the-art available techniques that could be used for in vivo detect EtOH and ACD both non-invasively (magnetic resonance spectroscopy), and invasively (microdialysis and biosensors). Among the different in vivo sampling techniques described, particular emphasis is paid to the field of enzyme-based amperometric biosensors. Biosensors have gained much attention in recent years for their ability to online monitor biological signals in vivo, and several micro- and nano-structured devices have been successfully used for in vivo studies. Owing to their high temporal and spatial resolution, biosensors could provide the adequate technology for studying in vivo EtOH pharmacokinetic.

Application of indirect detection methods in biomedical analysis

Indirect detection is a technically simple method to follow and quantify compounds without inherent detector response in high-performance liquid chromatography. A detectable component is added to the mobile phase and peaks are obtained for injected solutes as well as for mobile phase additives (system peaks). The underlying principle can be expressed by simple equations which show how the detection sensitivity can be optimized. The detection technique can be applied to uncharged as well as charged compounds, but the sensitivity is considerably higher for ionic solutes. The response is unspecific and the technique should preferably be applied to samples with a limited number of components. Determinations in pharmaceutical products and quantification of impurities in substances are typical fields of application. Different detection principles can be used but UV absorbance is so far the dominant technique. The chromatographic system must be stable, and efficient thermostatting is essential. Indirect response effects can give rise to disturbances when the presence of a detectable component in the mobile phase is unknown or overlooked. The understanding of the underlying principle for the indirect detection is essential for tracing or preventing such disturbances.