Loop-type interfaces evaporation

LOOP-TYPE INTERFACES (CONCURRENT ELUENT EVAPORATION)... 

Coupled liquid chromatography-gas chromatography is an excellent on-line method for sample enrichment and sample clean-up. Recently, many authors have reviewed in some detail the various LC-GC transfer methods that are now available (1, 43-52). For the analysis of normal phase eluents, the main transfer technique used is, without doubt, concurrent eluent evaporation employing a loop-type interface. The main disadvantage of this technique is co-evaporation of the solute with the solvent. 

The analysis of sterols, sterols esters, erythrodiol and uvaol, and other minor components of oils and fats, is usually carried out by normal-phase HPLC-HRGC by using a loop-type interface and the concurrent eluent evaporation technique, as reported in the papers cited by Mondello et al. (48) (up to 1995) and in more recent papers (49, 50). More recently, reversed-phase LC-GC methods have been... 

In order to achieve the widest application range, partially concurrent solvent evaporation (PCSE) with an on-column interface is normally used during the transfer of analytes from the LC-type precolumn to the GC system. Eully concurrent solvent evaporation (ESCE), with a loop-type interface, is used in some cases, although the... 

Figure 8.20 Scheaatic representation of process of (A) pairtial concurrent evaporation and (B) concurrent evaporation using a loop-type interface for the transfer of eluent fron an VC colunn to a 6C column. (Reproduced with permission from ref. 224. Copyright Elsevier Scientific Publishers).

K. Grob and J. M. Stoll, Loop-type interface for concurrent solvent evaporation in coupled HPLC-GC. Analysis of raspberry ketone in a raspberry sauce as an example , J. High Resolut. Chromatogr. Chromatogr. Commun. 9 518 -523 (1986). 

Figure 3.11. Schematic diagram of a loop type interface with concurrent eluent evaporation for LC-GC. (From ref. [100] Elsevier).

Concurrent eluent evaporation is most commonly performed with the loop-type interface (Figure 4) the liquid is pushed into the oven-thermostatted precolumn by the carrier gas and stopped there by its... 

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