Column chromatography effluent collection

A similar ion-exchange resin method was used by Ling in 1955 (LI) for the examination of combined amino acids in urine. According to this procedure urine was desalted and simultaneously freed from amino acids by using Amberlite IR-112, H+-form resin. The effluent collected from the column was then fractionated on Amberlite IRA, OH--form resin, by successive elution with 0.16 N acetic acid, 0.08 N formic acid, 0.25 N formic acid, 0.08 N hydrochloric acid, and finally with 0.16 N formic acid. The solutions of all acids contained 10% of acetone. The collected fractions were hydrolyzed with hydrochloric acid and the liberated amino acids identified by means of paper chromatography. 

Most of the above methods of column chromatography have been, or can be, automated. Devices are available for the automated application of samples to columns which are useful for analytical evaluation of samples, or for repeated analysis or separations to obtain larger amounts of material. The specific fractions of the effluent can be collected. Equipment for these purposes can be obtained from several of the supplier listed at the end of the HPLC section above with the corresponding websites. GC systems coupled with mass spectrometers (GC-MS) and HPLC systems coupled to mass spectrometers (LC-MS) are extremely important methods for the separation and identification of substances. These are invariably linked to a computer with internal libraries which can identify the peaks, and the libraries can be continually updated (see above). With more elaborate equipment LC-MS-MS where the peaks from the first spectrometer are further analysed by a second mass spectrometer provide a wealth of information. If not for the costs involved in GC-MS, GC-MS-MS, LC-MS and LC-MS-MS equipment, these systems would be more commonly found in analytical and research laboratories. [For further reading see Bibliography.]... 

As regards monitoring of the separated components emerging in the column effluent, it is carried out by means of a physical measurement, for example, UV or visible absorbance, refractive index or conductivity, as is routinely done in liquid column chromatography. Alternatively, separate fractions can be collected automatically and subjected to further analysis. 

Accepting that the cryofocussing/remobilization process is both effective in the collection of discrete sections of the effluent from column 1, and very rapid in reinjection to column 2, we can now propose a number of ways of using the LMCS device in multidimensional gas chromatography modes. 

There are two general types of multidimensional chromatography separation schemes those in which the effluent from one column flows directly on to a second column at some time during the experiment, and those in which some type of trap exists between the two columns to decouple them (off-line mode). The purpose of a trap is often to allow collection of a fixed eluate volume to reconcentrate the analyte zone prior to the second separation step, or to allow a changeover from one solvent system to another. The use of offline multidimensional techniques (conventional sample cleanup) with incompatible mobile phases, is common in the literature, and replacing these procedures with automated on-line multidimensional separations will require continuous development efforts. 

Principles and Characteristics Multidimensional gas chromatography (MDGC) is widely used, due to the mobile-phase compatibility between the primary and secondary separating systems, which allows relatively simple coupling with less-complicated interfaces. In its simplest form, 2DGC can be carried out in the off-line mode. The most elementary procedure involves manual collection of effluent from a column, followed by reinjection into another column of a different selectivity (e.g. from an apolar to a polar column). Selecting proper GC-column combinations is critical. In on-line mode, the interface in MDGC must provide for the quantitative transfer of the effluent from one column... 

DA, MEK, methyl vinyl ketone (MVK), propionaldehyde (PrH), and acetaldehyde (AcH) were analysed by on-line gas chromatography using a Varian 3400 GC equipped with a thermal conductivity detector and a 2m column containing 25% w/w B.B -oxydipropionitrile on Chromosorb W (80-100 mesh) operated at 60°C He was used as the carrier gas. Acetic acid (AcOH) was collected in 2ml of water from the effluent stream over a period of 1 hour and later analysed on a Porapak QS column at 150°C. CO2 was tested by removal of 2ml samples from the exit of the reactor with a gas syringe and injecting them onto a Porapak QS column operated at 60°C. 

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