Some GC Procedural Comments on the HP 5880A

1. Enter you name and professors name in the GC log book along with the data and use. Note any problems or low levels of compressed gases. Example:

2. Turn on the three gas supplies. There are three tanks of compressed gases fixed to the GC table: hydrogen, nitrogen and air. The tanks are changed when their pressure are approaching 50 psig the pressure of new tanks on the primary gauge is shown below. Take special care to prevent the accumulation of gaseous hydrogen in the laboratory but insuring the gases are either turned off at the chromatography or burning.

3. The GC with two integrators and an auto sampler has three toggle switches (connected to the copper gas lines) which turn the three gases on or off for this instrument. This instrument was setup to act as a backup. This instrument is named GC-2 and the other instrument called GC-1.

The gases are turned off with two valves on GC-1 and at the toggle switches on GC-2. The valves are turned full on or off, in the direction indicated by the arrow on the control panel. GC-2 is shown at the right.

4. The igniter for the hydrogen-air flame in the flame ionization detector (FID) is located in right hand door of the instrument. Turn the three way switch from off to down to light the flame. A small pop will be observed when the flame ignites.

Hints

A. Place a mirror over the top of the FID if there is a doubt about the flame being lit.  A burning flame will show a small spot of moisture condensed on the mirror. If you do not obtain a solvent peak 3 to 4 minutes after injection of a sample it may be the flame has gone out, the syringe is bad, or the septum need to be replaced.

B. Never to open the oven door to the chromatographic column unless it is at room temperature.

5. Check the integrator to determine if the proper levels are present for the temperature of the igniter and detector and other requisite parameters. The following are suggested levels. The instruments are capable of a much wider range.

6. The GC integrator is shown at the left. The version with the GC-2 also has an alpha numeric keyboard below the standard keys. The main keys needed for normal operation are: Start Run and below that key Stop Run. The Start Run key is activated when the sample is injected. If chromatograms are to be reproducible within the sequence of injection and beginning the run must be the same. The Stop Run key allows the operator to terminate the run at any point. Some sequences require the operator to terminate the analysis with this key.

Hints -- A. Always begin a series of run with a solvent blank. This shows the solvent elution time and cleans the column from the last series of injections. B. The key to success is a good microliter syringe. Many of the syringes used in the laboratory have been bent, left uncleaned, become clogged and do not deliver sample. Look at the amount of sample being delivered from the tip of a syringe during the cleaning process and determine if the flow is smooth. C. Insert the needle into the injection port, almost to the hilt before quickly injecting the sample. D. Remember the injection port is at a temperature near the boiling point of the solvent.

7. The integrator has a special key sequence that must be used to either determine the current value or to set a new value into the system. For instance, to determine the current temperature of oven the key strokes would be: List, Oven Temp, Enter. Commands must be activated with the Enter key. In order to set the initial oven temperature: Oven Temp, Initial Value, Enter. Note the key Oven Temp is required before setting or determining the values for Final Time, Final Value, etc. There is a shifted of list of key that are activated with the Orange Key, e.g. hit the orange key before these keys: Equlib Time, Post Value, Post Time

Key Stroke Example -- To enter the final oven temperature: Oven Temp, Final Value, 150, Enter. To advance the paper press the Enter key twice or as required to move the chart paper forward. Pleas do not waste chart paper. The following error message will appear if the incorrect key strokes have been entered: "ERROR: INVALID FILE NAME" or "ERROR: UNSTABLE SET POINT".

8. The injection port septum is hot and must be changed periodically. There is a special tool to help in the opening of the injection port to replace the septum.

9. Leave the instrument unattended during the day without turning off the gas flows or changing the oven temperatures. If the instrument is going to be off overnight or longer:

• first reduce the oven temperature to around room temperature or about 30° C.
• When the oven has reached near room temperature turn off the gas flow at the three cylinders, the toggle valves, and at the hydrogen and air valve for GC-1. This procedure protects the column and does not waste gases.