Page 178 - An Introduction to Analytical Atomic Spectrometry - L. Ebdon

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B.3.3 Instrumentation and Reagents

1 Atomic absorption spectrometer with air-acetylene burner head. Pressurized acetylene cylinder. Air
compressor.

2 Magnesium stock solution—using distilled or deionized water prepare six magnesium standards in
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100 ml volumetric flasks of 0.1, 0.3, 0.4, 0.5, 0.6, and 0.8 µg ml concentration from the stock solution.
Also prepare 250 ml of a 0.2 µg ml magnesium standard.
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3 Synthetic human urine sample.

B.3.4 Procedure

NOTE: Solution (either water or sample) must be continuously aspirated into the flame. Therefore,
ensure that the sample delivery tube is immersed in solution at all times.

Ensure that you have prepared all of your standards before proceeding with the experiment.

1 Switch the spectrometer on and allow to warm up for 10 min.

2 Ensure that an air-acetylene burner head is fitted.

3 Insert a magnesium hollow-cathode lamp.

4 Set the lamp to the recommended value.

5 Turn the monochromator wavelength setting to 285 nm using the coarse adjustment, then use the
fine wavelength control to tune in to the line maximum at 285.2 nm.

6 Ensure that the light from the lamp passes over the slot of the burner, 1-2 cm above the burner top,
by placing a white card on the burner top.

7 Switch on the air compressor; ensure that the pressure and flow rate are correctly set.

8 Turn on the main valve on the acetylene cylinder and ensure that the cylinder and outlet pressures
and flow rate are correct. If the cylinder pressure is below the recommended value do not attempt to
ignite the flame, as this will result in acetone being ignited in the flame. (Acetylene when stored under
pressure is dissolved in acetone.)

9 Ignite the flame and ensure that it is blue with a very faint tinge of yellow above the primary cone. If
it appears to be too fuel lean or fuel rich, adjust the fuel flow rate control accordingly.