Improving splitless injection with electronic pressure programming

Abstract

An experimental injection port has been designed for split or splitless sample introduction in capillary gas chromatography; the inlet uses electronic pressure control, in order that the column head pressure may be set from the GC keyboard, and the inlet may be used in the constant flow or constant pressure modes. Alternatively, the column head pressure may be programmed up or down during a GC run in a manner analogous to even temperature programming. Using electronic pressure control, a method was developed which used high column head pressures (high column flow rates) at the time of injection, followed by rapid reduction of the pressure to that required for optimum GC separation. In this way, high flow rates could be used at the time of splitless injection to reduce sample discrimination, while lower flow rates could be used for the separation. Using this method, up to 5 μl of a test sample could be injected in the splitless mode with no discrimination; in another experiment, 2.3 times as much sample was introduced into the column by using electronic pressure programming. Some GC peak broadening was observed in the first experiment.

Pulsed Splitless Injection and the Extent of Matrix Effects in the Analysis of Pesticides

“…Using common splitless injection, typically only a small volume of sample can be injected (up to 1 lL) employing conventional types of liners (glass deactivated liners, volumes 800 -990 lL). A pressure pulse applied to the column head during injection permits injection of larger sample volumes (up to 5 lL) [11,[15][16][17][18]. A higher amount of sample introduced under these conditions is assumed to swamp out active sites in the liner, thus allowing a larger portion of analytes to pass to the column.…”

“…Recently, the use of pulsed splitless injection for the analysis of organic contaminants has been reported [10,11,[14][15][16][17][18][19]. These techniques involve an increase of column head pressure for a short time period during sample injection (usually for 1 or 2 min).…”

“…In addition, due to the increased pressure higher volumes of sample can be injected (up to 5 ll) without the risk of backflash. Consequently lower detection limits can be achieved [11,[15][16][17][18].…”

Evaluation of Solid-Phase Microextraction Desorption Parameters for Fast GC Analysis of Cocaine in Coca Leaves

“…An interesting approach is the application of a pressure pulse during splitless injection, which permits the increase in flow rate in the injector and, therefore, accelerates the sample transfer rate. This technique, called pressure pulsed splitless (PPS) (10), also allows the introduction of higher solvent amounts and minimizes degradation problems during conventional GC analysis (11)(12)(13).…”

Determination of 4-nonylphenol—part 1: Optimization of the gas chromatographic determination of 4-nonylphenol by orthogonal array design and electronic pressure programming

“…In addition to temperature programming, pressure programming can be used to vary flows during different parts of an analysis to help improve conditions for both injection and detection. Large volume injection is also allowed during EPP as the high flow rates at the time of splitless injection can reduce sample discrimination [32]. Some detectors are flow-sensitive, and EPP can optimize the detector performance (sensitivity, selectivity, and baseline stability) by maintaining a constant flow of carrier gases to the detector 1331.…”