Columns, Supplies, and Standards Knowledgebase

If you are using another manufacturer s GC column and would like to upgrade to an Agilent J&W column, this GC column cross-reference guide will make your conversion easy. Each section of this guide lists, by phase selection, the suggested Agilent J&W upgrade from other GC manufacturers columns. This is not, however, a complete listing, but represents only the most frequently used columns. If you do not find the column you are currently using and would like to upgrade to an Agilent J&W column, contact our Technical Support staff or if you are located in North America call us at 1-800-227-9770. Click on the manufacturer below to find your Agilent J&W upgrade.

Quadrex: https://www.chem.agilent.com/cag/cabu/qdrxcref.htm 
Restek: https://www.chem.agilent.com/cag/cabu/rstkcref.htm
SGE: https://www.chem.agilent.com/cag/cabu/sgecref.htm
Supelco: https://www.chem.agilent.com/cag/cabu/splcocref.htm
Chrompack/Varian: https://www.chem.agilent.com/cag/cabu/crmpkcref.htm

Baseline problems arise from many causes. Some of these are: • Electronic or mechanical failure • Contamination in critical areas, such as detectors • Incorrect or inappropriate setpoints • Leaks, column or septum bleed, or other chromatographic difficulties These problems may interact to a certain degree and or arise from any of the above areas. Baseline Symptoms: Position 1. Baseline not at left (lower) part of chart: -Check the zero of your recording device: An attenuation or range change during the run may be responsible. -Check the TCD polarity. 2. Baseline position changes suddenly during the run: -This usually results from a range or attenuation change. -It can also result from valve operations: If valves are being switched during the run. -Septum leak Wander and Drift Baseline wander and drift may occur when a flow or temperature setting is changed. If the system is not stabilized at the new conditions before starting a run, some baseline changes are to be expected. (The following assumes that sufficient time has elapsed for stabilization.)

1. Baseline moves steadily upscale or downscale (drift) during the run: -This is most frequently seen during temperature programming: Operation with asingle column (no column compensation) at moderate to low attenuation causes this. If dual columns are used, check that the signal mode is correct for column compensation. -It is also possible that the compensation is insufficient or too great. Thorough column conditioning minimizes (this cause of drift).

2. Baseline erratic, moves up and down (wander): - Suspect a leak in the system: Check septum condition and replace if necessary. Check column connections. - If there is a leak at the detector end of the system then retention times should be stable and only sensitivity is reduced. A leak at the inlet end of the column will result in decreased sensitivity and delayed retention times. Noise Noise is rapid vertical baseline fluctuations, broadening the baseline and giving it a hairy appearance. Noise is different from spiking; spikes are isolated events, rather than almost continuous.

Some noise is inevitable with any detector. At high attenuation it is invisible but appears as attenuation is decreased.

1. Noise appears suddenly on a previously clean baseline: -Consider all changes made recently to the system: Reduced attenuation for example. -New septa may contribute noise from bleed of low molecular weight material. If noise decrease when inlet temperature is lowered, this is the likely cause. -Contaminated carrier gas: Check to see if a new tank was replaced recently,replace with a different lot number. If the new gas was badly contaminated it may have contaminated the traps and changing the tank may not show any improvement until the traps are regenerated. -Contaminated detector gases (hydrogen or air) -Air currents from a fan or air conditioner blowing across the top of the instrument may interfere with gas exiting from the detector. -A contaminated detector results in noise.

2. Noise increases gradually to an unacceptable level: -This indicates a gradual build up of the noise source, rather than an abrupt change as discussed above. Flame ionization detectors are susceptible to build up of deposits in the collector. In extreme cases spiking occurs along with increased noise level. -Silicon dioxide deposits are formed when bleed from a silicone column is burned in the flame. This material is removed mechanically. Preventative measures include use of low column loadings, stationary phases with high temperature limit, thorough column conditioning before use, and the lowest possible oven temperatures for the analysis. -Carbon deposits may form from solvents that burn poorly (chlorinated and aromatics). If possible, avoid such solvents. If they are necessary, periodic cleaning of the collector is required. -Gradual noise increase may occur from saturated carrier gas drier or chemical traps. When these approach their capacities, contaminants begin to pass through and create noise. Trap and drier regeneration or replacement eliminates this source of noise.

Spiking Spikes are isolated baseline disturbances, usually as sudden and large upscale movements. If accompanied by noise, the noise problem should be solved first, since spiking may disappear at the same time.

1. Spikes appear whenever the chart is running: -The cause is almost always electronic in origin: Loose connections are likely. Check signal cable connections at the detector and controller ends. -Loose or dirty contacts between printed circuit boards and their connectors may be responsible.

2. Spikes appear on chromatograms but not when the recorder is isolated, (no input signal): -This could be indicative of a detector problem: For example, an extremely dirty FID collector. -If a metal or glass packed column is being used column material could have been blown into the detector: FID and NPD are more susceptible due to the narrow bore of the jet. Systematically troubleshooting the GC is key to understanding and diagnosing the cause of baseline problems. Isolating the problem can usually be accomplished by simply identifying what was changed last. If problems still occur after stepping through the suggestions in this document please call for Agilent Technical Assistance.

Place samples for headspace extraction in glass vials. Place the glass vials in the Headspace Sampler tray. In general, fill sample vials about half way (although vials can be filled to the 3/4 level). This ensures that the sampling probe will not come into contact with the solid or liquid phase during the sampling step. The G1888 Network Headspace Sampler accepts either 10-mL or 20-mL sample vials. The Headspace Sampler can only run one vial size at a time. The vial must be sealed properly to insure that the headspace gases do not escape prematurely. For crimp top vials, use a crimper (Agilent part no. 9301–0720) designed for headspace vials with 20-mm caps to seal the vials. Screw caps (Agilent part no. 5188–2759) and screw top vials (Agilent part no. 5188–2753) are also available. See Headspace Consumables FAQ for more information. Sampling from an incorrectly capped vial may cause the Headspace Sampler to jam during septum puncture. Do the following to prepare a vial for sampling:

1. Place a septum in a vial cap with the PTFE side facing the vial. Take care not to contaminate the septum.

2. Place the cap upside down on a table.

3. Place the sample in the vial. Most vial should not be more than 50% full, but some vials can reach 75% full.

4. Place the septum and cap together over the vial opening.

5. Place the crimper over the cap and vial. See Figure14.

6. With slow and steady pressure, squeeze the crimper handles to seal the vial.

7. Remove the crimper.

8. Turn the vial and cap 90° and crimp a second time.

9. Check that the seal is adequate by trying to twist the cap on the vial. It should be difficult or impossible to turn the cap. If the cap turns easily, recrimp the cap. The crimping tool may need adjustment.

10. To decap vials, use a decapper for vials with 20-mm caps (part no. 5181–1214). Vials will contain laboratory air, which may be contaminated with things such as solvents or freon leaking from air conditioners. If contaminants will adversely affect your results, use argon to purge the vials just before capping and sealing.