significance And Use:

scope:

1.1 This practice covers the installation and maintenance of fused silica capillary columns in gas chromatographs that are already retrofitted for their use. This practice excludes information on:

1.1.1 Injection techniques.

1.1.2 Column selection.

1.1.3 Data acquisition.

1.1.4 System troubleshooting and maintenance.

1.2 For additional information on gas chromatography, please refer to Practice E260. For specific precautions, see 7.2.2.2(1), 7.2.2.2(2), 7.2.7, and 7.2.7.2.

1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.

1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. For specific safety information, see Section 6, 7.2.2.2(1), 7.2.2.2(2), 7.2.7, and 7.2.7.2.²

TABLE 1 Typical Splitter Vent Flow Rates (50 to 1 split ratio) (at optimum linear velocity)

Note 1-The curves were generated by plotting the height equivalent to a theoretical plate (length of column divided by the total number of theoretical plates, H.E.T.P.) against the column's average linear velocity. The lowest point on the curve indicates the carrier gas velocity in which the highest column efficiency is reached.Note 2-Gases information available from Compressed Gas Association (CGA), 4221 Walney Rd., 5th Floor, Chantilly, VA 20151-2923, http://www.cganet.com.FIG. 1 Van Deemter Profile for Hydrogen, Helium, and Nitrogen Carrier Gases

Note 1-Fig. 2 shows that the resolution is similar but the analysis time is reduced by 50 % when comparing hydrogen to helium in an isothermal analysis using optimum flow velocities.Note 2-Hydrogen provides similar resolution in one-half the analysis time of helium for an isothermal analysis.Note 3-

Note 4-30 m, 0.25-mm ID, 0.25 μm 5 % diphenyl − 95 % dimethyl polysiloxane 0.1-μL split injection of chlorinated pesticides.

FIG. 2 Hydrogen Versus Helium (Isothermal Analysis)
FIG. 3 Capping Silanol Groups with Dimethyl Dichlorosilane (DMDCS)
Note 1-Septum bleed can obscure or co-elute with compounds of interest, thus decreasing the analytical accuracy.Note 2-

Note 3-30 m, 0.53-mm ID, 0.50 μm 5 % diphenyl − 95 % dimethyl polysiloxane 0.1 μL direct injection of 50 pg pesticide standard.

FIG. 4 ECD Septum Bleed