The flame assembly can be considered as the heart of the AAS. It comprises of three main comments : the nebulizer, spray chamber and the burner head. Regular upkeep and maintenance of the component parts can provide a long service life span of the instrument, minimum breakdowns and a higher reliability on results. The article provides some useful tips to help you achieve these goals and make most effective use of your AAS system.
The nebulizer plays the important role of converting the sample into a fine aerosol or spray which is then led to the flame. The body of the nebulizer is made corrosion resistant by using stainless steel, Pt/Ir or Pt/Rh alloys for its construction.
- Visually inspect the plastic capillary tubing conveying the sample to the nebulizer. It should be free of any kinks or bends,clog free and fixed tightly to nebulizer to prevent air leaks.
- To remove any nebulizer capillary blockages remove the nebulizer and sonicate in a 0.5% soap solution such as Triton X –100 for about 10 minutes. In case the blockage persists use the nebulizer cleaning wire and then again repeat the sonication
- Refix the nebulizer and aspirate with about 500 ml of distilled water. It is advisable to aspirate the nebulizer with distilled water before shutting down the instrument each day
The spray chamber is a zone where the sample aerosol gets mixed with the fuel and oxidant gases is and let to the burner.It is lined with a corrosion resistant polymer coating to increase its life. An impact device such as a flow spoiler or impact bead in the path of the aerosol spray from the nebulizer prevents large droplets of the spray from being carried to the flame.The earlier article on flow spoiler and impact bead will help you decide which option to select for getting best results for the analysis in hand.
- Visually inspect the bead for cracks, pitting or solid deposits. The bead can be replaced if found necessary or cleaned by adopting the sonication procedure in soap solution followed by distilled water.
- Check O-rings of the spray chamber. Replace any damaged rings if found necessary
- Check for any blockages in the drain pipe and empty out the waste drain receptacle regularly
A burner is made from a material such as titanium so that it is both corrosion and heat resistant. However, over a period of time salts or carbon begin to accumulate along the length of the burner slits leading to changes in the flame profile
It is important to ensure that the burner is at room temperature before an attempt is made to clean it. Try removing the solid residues with the brass cleaning strip. Use of blades or knives is not recommended as they can cause damage to the slit edges through fine nicks. Final cleaning can be carried out by aspirating with 0.5% nitric acid followed with a detergent solution and finally with distilled water. Remember to dry the burner properly before assembling for next use.
It is further advised to aspirate the system with about 100 ml distilled water at the end of analysis to maintain the efficient working of all component parts, namely, tubing, nebulizer, spray chamber and burner.