Native ethylene glycol in wine: Application of a dead volume free,very fast “deans heart-cut” system on-line with multi-chromatography

Data about the existence of native HO? CH₂? CH₂? OH (MEG) in natural wines and champagne has led to delicate questions because of legal decisions already made to declare wine or champagne illegal for sale if the MEG concentrations found are above 10 mg/liter. Action has been taken because of the DEG (diethylene glycol) disaster in European wines of 1985…86. An incorrect legal decision was made due to the belief that MEG cannot be produced biochemically by grape vines. A further reason may be lack of correct data on native MEG trace concentrations, as a result of the special behavior of this diol. As first member of a homologous series whose higher members (C₄) are normally found in all wines at quite high concentration levels, MEG shows extremely adsorptive behavior. The solution of the chromatographic problems is summarized in this paper. MEG concentrations in Riesling as example are in the range of 2 to 6 mg/liter and can easily be increased by biotechnological steps to a level of around 10 to 60 mg/liter. This is again due to the specific adsorptive behavior of MEG, which can be enriched on filter surfaces and displaced when the wine acidity changes with changing types. In order to control and guarantee the qualitative and quantitative results of MEG analyses we used a combination of Deans heart cutting on-line with Multi-Chromatography. It was easy to produce false data by many otherwise useful single column or two-dimensional separation processes, etc.     

Selectivity tuning of serially connected open-tubular (capillary) columns in gas chromatography. Part I: Fundamental relationships

Summary The evolution of the use of mixed phases or serial column combinations is outlined, leading to systems with fixed-length columns to be used in selectivity tuning (“multi-chromatography”). The difference between multi-chromatography and multi-dimensional gas chromatography is outlined. After discussing the system used in subsequent work, the fundamental relationships of multi-chromatography are detailed. Among the basic relationships the additivity of retention data, the relationship between the individual and composite capacity factors and the relative retentivity serving as the fundamental parameter of a multi-chromatography system are discussed. The relative retentivity is derived as a function of gas holdup times, pressures, and average velocities or flow rates. Finally, the relationships between individual vs. composite relative retention, efficiency, and resolution values are deduced. We dedicate this paper to the memory of our dear friend, Dr. S. R. Lipsky. Consolidated and enlarged text of part of the papers presented at the 37th Pittsburgh Conference on Analytical Chemistry and Applied Spectroscopy (Atlantic City, NJ, March 10–14, 1986) (92–94), and at the Seventh International Symposium on Capillary Chromatography (Gifu, Japan, May 11–14, 1986) [95]. Part II will follow in the December issue.     

Selectivity tuning of serially connected open-tubular (capillary) columns in gas chromatography. Part II. Implementation

Summary As a follow-up to our previous publication (see ref. [1]) dealing with the experimental system and the fundamental relationships of multi-chromatography („polarity tuning”), the present paper deals with the operation, characteristics and performance of the experimental set-up, and presents experimental verification on the validity of the basic relationships. The possibilities of influencing and adjusting the range in which the capacity factor is changed by the proper selection of column parameters are outlined and the observed changes in the retention index demonstrated. Ways to optimize the relative retentivity to achieve the best possible resolution of multi-component mixtures is illustrated. Finally, the possibility of combining temperature-programmed operation with selectivity tuning in a multi-chromatography system is demonstrated. Continuation of a report based on the papers presented at the 37th Pittsburgh Conference on Analytical Chemistry and Applied Spectroscopy (Atlantic City, NJ, March 10–14, 1986), and at the Seventh International Symposium on Capillary Chromatography (Gifu, Japan, May 11–14, 1986). Part I: ref. [1].