Troubleshooting and Maintenance of AA Systems: Part 1 - Hollow Cathode Lamps

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Agilent Support Insights

 

This Information Applies To: All Agilent AA systems: 55B, 240FS, 280FS, 240Z, 280Z

 

Issue:

It is important to maintain your atomic absorption system and troubleshoot when necessary, to keep your AA instrument in good working order. This practice will lead to the best results and reduce downtime.

 

Analysis: 

Agilent hollow cathode lamps are available as either coded or uncoded. Uncoded lamps provide the best cost value and fit most AA spectrometers. Coded lamps have extra pins in the base of the lamp, which provide an extra lamp recognition circuit. Once inserted into the spectrometer, the software automatically recognizes the type of lamp and its position.  

For better sensitivity, and lower detection limits, Agilent offers special boosted discharge lamps called UltrAA lamps. They use the standard lamp current but apply an extra boost discharge within the lamp to increase the emission intensity. The boost current is supplied from a secondary control module, either integrated into the instrument, or supplied from an external module. Agilent UltrAA lamps lower detection limits for the most demanding applications.

A unique, often misunderstood feature of Agilent hollow cathode lamps is the black getter patch near the cathode. It is a thin layer of zirconium deposited inside the lamp during purification and processing. This thin film is highly reactive, and acts as an efficient scavenger of impurity gases such as oxygen and hydrogen. The film ensures extended lamp life and spectral purity throughout the lifetime of the lamp. You may also see that a film of the cathode material deposited inside the glass envelope of the lamp. This is also a result of the lamp purification process. The amount of material deposited varies, depending on the volatility of the cathode.

 

Steps to Follow:

Optimizing the lamp

 

Before installing the lamp, check the recommended operating current and wavelength, which is conveniently located on the label near the base of the lamp. Verify that they match the default selections in the software. Once the method has been set up, simply click the "Optimize" button from the Analysis page, and then click "OK" to optimize the lamp. Slowly rotate the lamp adjustment screws at the base of the lamp, while watching the lamp optimization bar and numerical display, as shown in Figure 1. Maximize the value. Generally, only small adjustments will need to be made.

Adjustment of hollow cathode lamps

                                   Figure 1. Adjustment and Optimization of the Hollow Cathode Lamp

 

If the display goes off-scale, click "rescale" and continue optimizing, until the maximum value is obtained on the display.

If you have a flame instrument, and you enabled the background correction, you will see a second optimization bar for the deuterium background correction lamp. Simply rotate the deuterium lamp adjustment screws, located in the bottom left of the lamp compartment. Watch the optimization bar and numerical display and adjust the screws to achieve the maximum value, as shown in Figure 2.

Deuterium lamp adjustment

                                    Figure 2. Adjustment and Optimization of the deuterium lamp

 

Only minor adjustments will normally be required. Full realignment of the deuterium lamp is usually required when replacing the lamp only.

 

Helpful Tip: Make a note of the gain value the first time you optimize the lamp. Each time you use the lamp, the value should be close to the noted value. By monitoring the gain values, you can track the performance of the lamp. A significant change in the gain can indicate that the lamp is reaching the end of its operational life.

 

Learn more on how to effectively maintain and troubleshoot your Atomic Absorption Spectrometer:  Agilent 240/280 User's Guide 

For more information on Agilent lamps, see the video:   Troubleshooting and Maintenance of Hollow Cathode Lamps   

 

Keywords: atomic absorption, 55B, 240FS, 240Z, 280FS, 280Z, hollow cathode lamp, deuterium lamp, lamp adjustment

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