Burner heads alignment

Set up the atomic absorption spectrophotometer for the air/acetylene flame analysis of cadmium according to the SOP (5.8.) or the manufacturer s operational instructions. For the source lamp, use the cadmium hollow cathode or electrodeless discharge lamp operated at the manufacturer s recommended rating for continuous operation. Allow the lamp to warm up 10 to 20 min or until the energy output stabilizes. Optimize conditions such as lamp position, burner head alignment, fuel and oxidant flow rates, etc. See the SOP or specific instrument manuals for details. Instrumental parameters for the Perkin-Elmer Model 603 used in the validation of this method are given in Attachment 1. 

A number of instrument variables need to be set prior to making measurements. These include slit, wavelength, lamp current, lamp alignment, amplifier gain, aspiration rate, burner head position, acetylene pressure, air pressure, acetylene flow rate, and air flow rate. Some instruments are rather automated in the setup process, while others are not. Your instructor will provide detailed instructions for the particular instrument you are using. Be sure to turn on the fume hood above the flame. 

Controls that need to be optimized are wavelength, slit width, lamp current, lamp alignment, aspiration rate, burner head position, and fuel and oxidant flow rates. See Section 9.3.5 for details. 

A burner head, typically with a single slot (10 x 0.2 cm), is aligned along the axis of the optical beam from the radiation source. The nebuliser/burner assembly is mounted on a platform which provides for positional adjustment in both the vertical and horizontal planes. The optimal height of the optical beam above the burner slot varies with each analyte element (and somewhat with the sample composition) is established experimentally for each standard solution. An impressive graphic presentation of the spatial distribution of analyte atoms of sodium, calcium, or molybdenum in an air/C2H2 flame (under identical operating conditions) has been presented by Rann and Hambly Anal. Chem. 37, 880, 1965). 

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