Extended use of solvent venting injection techniques for large sample volumes and coupled capillary columns in SFC

Berg, B. E.; Flaaten, Anne M.; Paus, J.; Greibrokk, Tyge

doi:10.1002/mcs.1220040308

Cited by 16 publications

(10 citation statements)

References 9 publications

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“…The SFC instrument consisted of one ISCO 260 D pump (Lincoln, Nebraska, USA) and two SFC/GC ovens [8] The solvent was vented via the 6-port valve with helium gas. Gas purging of the solvent, which utilized 100 pm i.…”

Section: Methodsmentioning

confidence: 99%

“…The sample is injected several times and the solvent is purged from the retention gap with helium gas each time [8]. This technique is illustrated in Figure 6.…”

Section: Detailsmentioning

confidence: 99%

“…Solvent evaporation can be aided by the use of an expanding fluid [7] or by the addition of an inert gas as in solvent venting with a gas purge [8]. Solvent evaporation is expected to be under better control with an inert gas than with an expanding fluid because the solubility in the gas is lower than in the fluid.…”

Section: Introductionmentioning

confidence: 99%

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Evaluation of solvent venting with a gas purge for the introduction of microliter sample volumes in supercritical fluid chromatography

Berg¹,

Hansen

Flaaten

et al. 1993

J Microcolumn Separations

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Abstract. Peak broadening and sample recovery are important considerations when working with large sample volume injections in capillary SFC. To measure possible contribution to peak broadening in the venting valve, a tee coupling was inserted between the retention gap and the column. A standard sample containing glyceryl esters was injected. Based on time variance measurements, the venting valve did not lead to measurable band broadening. Recovery was found to be dependent on the length of the retention gap, the C02/He ratio in the purge gas, and the temperature of the retention gap. Cryofocusing was needed to increase the recoveries of volatile n-alkanes. To increase the recoveries of glyceryl esters, an enhanced C02/He ratio was needed.

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Section: Methodsmentioning

confidence: 99%

“…The sample is injected several times and the solvent is purged from the retention gap with helium gas each time [8]. This technique is illustrated in Figure 6.…”

Section: Detailsmentioning

confidence: 99%

See 1 more Smart Citation

Evaluation of solvent venting with a gas purge for the introduction of microliter sample volumes in supercritical fluid chromatography

Berg¹,

Hansen

Flaaten

et al. 1993

J Microcolumn Separations

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“…Sample recovery can be quite acceptable with this technique. For example, Berg et al [24] reported 100 % recovery of diglycerides. They used a 7-m × 50-µm-ID precolumn to introduce 1µl samples onto 50-µm-ID columns.…”

Section: Solvent Venting Under Supercritical Conditionsmentioning

confidence: 99%

“…Another gas-purging method, with helium, made use of a 1.5-m × 100-µm-ID uncoated retention gap [24]. By injecting 1 µl samples of glycerides, triglycerides were completely recovered, while diglycerides suffered a 30 % loss.…”

Section: Solvent Venting Under Reduced Pressurementioning

confidence: 99%

Injection techniques in SFC

Greibrokk¹,

Chester²

1999

Analusis

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The objective of the injector is to transfer the whole sample or a predetermined fraction of the sample quantitatively to the column in the narrowest possible band. The first part of this objective, a quantitative transfer of all components, is not always obtained since sample discrimination occurs in some injection techniques in SFC as well as in GC. The second part of the objective, transfer in a narrow band, is a process which is affected by numerous factors, such as diffusion, linear velocity, temperature, solvents, loading and mixing efficiency, as well as phase transitions. Some of these factors also influence the first part of the objective, the yield of the transfer process. Injector temperatures exceeding room temperature are only used with solutes which need higher temperature to stay in solution, such as some polymers. Injection at high temperature should be performed with caution, since a solvent which starts to evaporate from a hot injector, before the valve is actuated, may result in sample loss and poor reproducibility.In most applications the sample is introduced as a relatively large (depending on the analyte concentration) liquid plug into the stream of mobile phase. Due to limited mixing, the major part of the sample often arrives at the column inlet dissolved in a liquid composed of the solvent partially mixed with the mobile phase. Thus, the transient elution strength of the sample may often be considerably higher than the elution strength of the mobile phase, and can adversely affect the peak shapes by flooding and dispersing the sample over the column inlet.It is well known that an exponential decay injection profile is obtained because of the laminar flow of the displacing mobile phase [1]. By moving the valve back to the load position from the inject position after a predetermined time, the solvent tail can be removed. The injection syringe should be removed first, since the pressure in the sample loop is released through the injection and waste ports when the valve is returned to the load position. With large sample loops the syringe might be pushed out of the port, or the plunger pushed out of the barrel, if the syringe is left in the injection port.By injecting very small volumes, using splitting or small sample loops, a more thorough mixing with the mobile phase can be achieved prior to the column. Currently the nominal volume of the smallest commercially available sample loop is 60 nl. However, small volume (< 100 nl) internal sample loops are difficult to manufacture with high accuracy, and the small volumes are difficult to maintain without changes, particularly with loops made from polymeric materials.Column overload is rarely caused by the mass of the solutes, but almost always by the amount of solvent. With a retention factor k = 1, the injected volume that produces 10 % peak broadening has been calculated to be 24 nl on a 50-µm-ID open-tubular column, and with a retention factor of 10, the volume was calculated to be 130 nl [2]. With an actual injection of 223 nl, 10 % loss of...

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Preliminary study of specific migration of polymer additives from polypropylene to an acid‐based food simulant. SFC coupled to FID and GC‐MS for characterization and identification of migrants

Berg¹,

Hegna

Orlien

et al. 1992

J. High Resol. Chromatogr.

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Extended use of solvent venting injection techniques for large sample volumes and coupled capillary columns in SFC

Cited by 16 publications

References 9 publications

Evaluation of solvent venting with a gas purge for the introduction of microliter sample volumes in supercritical fluid chromatography

Evaluation of solvent venting with a gas purge for the introduction of microliter sample volumes in supercritical fluid chromatography

Injection techniques in SFC

Preliminary study of specific migration of polymer additives from polypropylene to an acid‐based food simulant. SFC coupled to FID and GC‐MS for characterization and identification of migrants

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