Solvent Trapping during Large Volume Injection with an Early Vapor Exit. Part 3: The Main Cause of Volatile Component Loss during Partially Concurrent Evaporation

Advanced GC/ICP-MS design for high-boiling analyte speciation and large volume solvent injection

“…A 20 ml injection was improvised with a standard injector by using a pressure pulse, an extra-large liner, extra-long pulse time and purge time, extra-long retention gap and solvent trapping. 16 The problems of using cold on-column injection 17 (contamination of the retention gap or GC column by nonvolatile sample matrix) and of the early vapor exit 18 technique (loss of low boiling analytes) were avoided.…”

Wax ester fraction of edible oils: Analysis by on‐line LC‐GC‐MS and GC×GC‐FID

“…In the meantime, on-line-coupled LC-GC evolved [11,12]. While the retention gap technique using the on-column interface remained the method of choice for the on-column transfer of fractions containing volatile components [13][14][15], concurrent eluent evaporation for fractions without volatile compounds, such as the wax esters, was increasingly performed also by the on-column interface [12,16]. This enabled to perform the two on-line LC-GC transfer techniques by a single interface and to use the same techniques as for largevolume on-column injection by syringe.…”

Investigations on analyte losses in systems suited for large-volume on-column injections

“…Figure 4 shows the relative areas of all solutes using a series of injections of the test mixture of n-alkanes (C8-C18) in n-hexane. The loss of volatiles will even increase when the evaporation process turns into fully concurrent evaporation, e. g. when injecting above the boiling point [11]. With the first set-up (no retaining precolumn) high losses were obtained with losses observed up to n-C 17 although a solvent film was formed which was as far as observed with fully concurrent solvent evaporation [17].…”

“…Recently, it has been demonstrated that the evaporation rate changes during injection and subsequent evaporation [7,9]. Although retaining precolums have been used since the introduction of the SVE [6,10], its role has not been investigated in much detail until recently [11]. There are several optimisation procedures.…”

“…Boselli et al [11] used thermocouples positioned on coils of the precolumn to determine the position of the front end of the flooded zone and to close the SVE. It was demonstrated that loss of volatile sample material during concurrent evaporation results from enrichment of the solute material at the front end of the flooded zone, which in turn is caused by a steep pressure drop over the most advanced plugs of sample liquid.…”