Split/splitless injection

Split/splitless injection. When capillary columns are used with small flow rates, even the smallest of injection volumes can saturate the column. Injectors that can operate in two modes, with or without flow splitting, are used (called split/... 

U Flow On Column Split Splitless Injection D Ratio Hole Time... 

There are several types of capillary inlets in use today which can be divided into two categories direct on-column injection and split/splitless injection techniques. 

When the extracted analytes are to be retained directly on the chromatographic column or at the retention interface, their insertion can be accomplished in various ways, namely (a) by injection into the column, whether directly (SFC, GC) or with the aid of a cooling system (GC, HPLC) (b) by split-splitless injection (SFC, GC) (c) by using a programmed temperature vaporizer (GC) or (d) by injection into a cold trap and subsequent thermal desorption (GC) or elution (HPLC). 

S. B. Hawthorne. D. J. Miller, J. J. Langenfeld. Quantitative analysis using directly coupled supercritical fluid extraction-capillary gas chromatography (EFE-GC) with a conventional split/splitless injection port, J. Chromat. Sci., 28 (1990), 2. 

Sample extracts were analysed by capillary gas chromatography with electron capture detection using either Perkin-Elmer series 8310 or 8510 instruments. One microlitre aliquots were injected via a split/splitless injection system operated in the splitless mode. The components were separated on a 25 m WCOT fused silica capillary column (CP-Sil-5, internal diameter 0.22 pm, Chrompack, UK). The stationary phase was non-polar 100% dimethylpolysiloxane. The temperature program for the separation of chlorobenzenes was based upon the work of Lee et al (1986). Quantification was based on the method of internal or external standard. 

A Carlo Erba Model 4160 gas chromatograph equipped with split/splitless injection systems and a flame ionization detector was employed throughout this work. Chromatograms were recorded with a Linear Model 55 strip-chart recorder. Hydrogen was the carrier gas in all instances. 

Separation and identification of the BTEX mixture was carried out on a Carlo Erba HRGC 5300 Mega Series gas chromatograph, with split/splitless injection... 

Separation and identification of the BTEX mixture was carried out on a Carlo Erba HRGC 5300 Mega Series gas chromatograph, with split/splitless injection and flame ionization detection. A 30 m x 0.25 mm id x 0.1 im film thickness DB-5 capillary column was used, with temperature programming from an initial temperature held at 50°C for 3 min before commencing a 16°Cmin 1 rise to 120°C, with a final hold time of 7 min. The detector temperature was set at 250°C. 

This injector, named PTV programmed temperature vaporizer), is conceptually similar to the split/splitless model. The temperature of the injection chamber can be programmed to effect a gradient, e.g. from 20 up to 300 °C, in a few tens of seconds (Figure 2.6). So, the advantages of the split/splitless injection are combined with those of the cold injection onto the column. 

A polar chromatogram of the extract was also obtained by injecting onto an HPS890 gas chromatograph with split/splitless injection and a flame ionization detector (FID) fitted with a Carbowax capillary column (SOm x 0.32mm i.d.,... 

Figure 4. Glass capillary gas chromatograms of aromatic hydrocarbons in New York Bight surface sediments. Analysis conditions 20 m X 0.32-mm i.d. Jaeggi SE-54 column installed in a Carlo Erba Model 2150 gas chromatograph equipped with split/splitless injection helium carrier gas at 0.55 kg/cm2 injection at room temperature, program 80°-240°C at 3°/minute injector and detector at 250°C. Numbered peaks are identified in Table V.

After having dissolved the substance containing the RS to be looked for in an appropriate solvent, it is possible to directly inject into the system 100% of an aliquot of the solution (if packed columns are used) or partially through a split system (if capillary, narrow-bore and wide-bore columns are used). It is simple, accurate and repeatable (with an internal standard). The main drawback is that samples very often contain non-volatile substances which are retained by the column, leading rapidly to a loss of efficiency and a dramatic decrease in sensitivity. In the current literature dealing with the RS, the direct injection process is less frequently used. Nevertheless, publications have appeared until recently using split/ splitless injection. ... 

On-column injection is another admission mode, which prevents component discrimination due to volatility or molecular weight. The sample is applied directly into the column head. This might be seen as an ideal injection, but with a large number of samples there is the risk of severe column contamination. This is caused by non-volatile sample components which deposit inside the column and eventually clog it. Split/splitless injection ports include a liner just before the column, to act as a filter for these interfering substances. In the case of on-column injection, a pre-column, or retention gap, which is a short capillary with no timer coating, is used for this purpose. 

Rgure 5 Programmed temperature vaporizer injector. (From Hinshaw JV and Seferovic W (1986) Programmed-temperature split-splitless injection of triglycerides comparison to cold on-column injection. Journal of High Resolution Chromatography 9 69-77.)... 

While samples may be directly injected onto a packed column, the small diameter of the capillary column presents a problem. In addition, it is easy to overload the capillary column with sample (Table 8.35). Two techniques for getting the sample into the column are split and split/splitless injection. 

Figure 8.52 Schematic diagram showing the operation of a split/splitless injection port.

Response factors of individual chlorobiphenyls on ECDs depend on the number and the positions of the chlorine atoms in the molecule, and also on the analytical instrument Frame, 1997). The BCD response is affected in particular by characteristics of the detection and injection systems, such as temperature, state of contamination and geometry. Considerable differences exist between detector responses of on-colunm and split/splitless injection, in particular the dependence on the amounts injected (i.e., the degree of linearity). It is not surprising, therefore, that apparently conflicting data are cited in the literature Mullin et at., 1984) and also that significant differences have been found for response factors even between carefully prepared standards. 

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