Injection capillary columns

Each laboratory was given a free choice of extraction, clean-up and conditions for the final determination. The latter, gas chromatography with high-resolution mass spectrometry, included choice of injection, capillary columns, ion masses monitored etc. [34]. In addition to the CRM, the participants received a calibrant solution containing the PCDDs/PCDFs of interest for this project as a control for their calibration procedure. 

The column is swept continuously by a carrier gas such as helium, hydrogen, nitrogen or argon. The sample is injected into the head of the column where it is vaporized and picked up by the carrier gas. In packed columns, the injected volume is on the order of a microliter, whereas in a capillary column a flow divider (split) is installed at the head of the column and only a tiny fraction of the volume injected, about one per cent, is carried into the column. The different components migrate through the length of the column by a continuous succession of equilibria between the stationary and mobile phases. The components are held up by their attraction for the stationary phase and their vaporization temperatures. 

In gas chromatography (GC) the sample, which may be a gas or liquid, is injected into a stream of an inert gaseous mobile phase (often called the carrier gas). The sample is carried through a packed or capillary column where the sample s components separate based on their ability to distribute themselves between the mobile and stationary phases. A schematic diagram of a typical gas chromatograph is shown in Figure 12.16. 

A technique for injecting samples onto a capillary column in which only a small portion of the sample enters the column. 

A technique for injecting a sample onto a capillary column that allows a higher percentage of the sample to enter the column. 

The direct injection of thermally unstable samples onto a capillary column. 

Time, Cost, and Equipment Analysis time can vary from several minutes for samples containing only a few constituents to more than an hour for more complex samples. Preliminary sample preparation may substantially increase the analysis time. Instrumentation for gas chromatography ranges in price from inexpensive (a few thousand dollars) to expensive (more than 50,000). The more expensive models are equipped for capillary columns and include a variety of injection options and more sophisticated detectors, such as a mass spectrometer. Packed columns typically cost 50- 200, and the cost of a capillary column is typically 200- 1000. 

An injection technique in capillary electrophoresis in which pressure is used to inject sample into the capillary column. 

A means of concentrating solutes in capillary electrophoresis after their injection onto the capillary column. 

This somewhat lengthy experiment provides a thorough introduction to the use of GG for the analysis of trace-level environmental pollutants. Sediment samples are extracted by sonicating with 3 X 100-mL portions of 1 1 acetone hexane. The extracts are then filtered and concentrated before bringing to a final volume of 10 mL. Samples are analyzed with a capillary column using a stationary phase of 5% phenylmethyl silicone, a splitless injection, and an EGD detector. 

Ohm s law the statement that the current moving through a circuit is proportional to the applied potential and inversely proportional to the circuit s resistance (E = iR). (p. 463) on-column injection the direct injection of thermally unstable samples onto a capillary column, (p. 568) one-taUed significance test significance test in which the null hypothesis is rejected for values at only one end of the normal distribution, (p. 84)... 

Heart-cutting, with trapping and re-injection, using isothermal dual capillary column chromatography for separation of the UV photolysis products of methyl... 

Figure 14.4 Schematic diagram of the cliromatographic system used for the analysis of very low concentrations of sulfur compounds in ethene and propene CP, pressure regulator CF, flow regulator SL, sanrple loop R, restriction to replace column 2 VI, injection valve V2, tliree-way valve to direct the effluent of column 1 to either column 2 or the restriction column 1, non-polar- capillary column column 2, tliick-film capillary column SCD, sulfur chemiluminescence detector FID, flanre-ionization detector.

SFC has been performed with either open capillary columns similar to those used in GC or packed columns transferred from LC, and the instrumentation requirements differ for these two approaches [12]. This chapter will focus on the use of packed column technology because of its dominance in the area of pharmaceutical compound separations. Current commercial instrumentation for packed column SFC utilizes many of the same components as traditional LC instruments, including pumps, injection valves, and detectors. In fact, most modem packed column SFC instm-ments can also be used to perform LC separations, and many of the same stationary phases can be used in both LC and SFC [9]. 

Always adjust the carrier gas linear velocity to 20-40 cm/sec before heating the capillary column. Neglecting to supply carrier gas while heating a capillary column will destroy it. Avoid injecting samples containing inor-... 

Frequently, column problems are caused by the samples that are being analyzed. This type of problem is more likely to occur on capillary columns because of their low capacity for contamination. Contamination results when the sample contains nonvolatile or even semivolatile materials such as salts, sugars, proteins, and so on. Column contamination is more frequently observed with splitless injection because larger amounts of material are being injected on the column. 

The use of a fused silica capillary column for the GC analysis of the neutral oil extract has provided the means for improving the resolution of components in a more inert system. The sultones are determined by temperature-programmed GC over CP-Sil-5 CB (methyl silicone fluid) in a 25 m x 0.2 mm fused silica capillary column using nonadecane as internal standard. A sample split ratio of 1 100 is recommended for a 3-pl injection. 

The products resulting from the reaction were injected vrith an automatic sampling valve into a GIRA GC 181 gas phase chromatograph and analyzed with a flame ionization detector. The separation was carried out in a capillary column DB5 (J and W Scientific). 

Oxyfluorfen column, fused-silica capillary column coated with cross-linked methyl silicone (25 m x 0.3-mm i.d., 0.52- am film thickness) temperature, column 200 °C (1 min), 10°Cmin to 250 °C (5 min), inlet and detector 250 and 300 °C, respectively gas flow rates, N2 carrier gas 30mLmin , N2 makeup gas 30mLmin H2 3.5mLmin" air llOmLmin injection volume, 2 p.L. ... 

The determination of acifluorfen in soybean was performed using CE," under the following conditions capillary column (total length 83 cm, 65 cm to the detector, with a 3-mm pathlength, 75-p.m i.d.) absorbance detector, 240 nm capillary oven temperature, 20 °C mnning buffer, 50 mM ammonium acetate buffer (pH, 4.75) applied voltage, 17 kV injection, 0.4 min at 4 mbar migration time, 20 min. 

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