Determination of copper in silicate rock by graphite furnace AAS with direct introduction of suspended sample

A simple method is investigated for direct determination of copper in silicate rocks by graphite furnace AAS. The method is based on the atomization of copper by the introduction of powdered rock samples suspended in 10% glycerin solution into a furnace. The sample (less than 10 μm in particle diameter) of 110 mg containing less than 1.0 μg of copper is placed in a polystyrene test tube fitted with a stopper (15 ml). 5.0 ml of 10% glycerin solution are added to the tube, and the sample is dispersed into solution by an ultrasonic agitator for 1 min. Then, 10 μl of the suspension, which has been mixed thoroughly to make a uniform suspension, are injected into a graphite furnace. The sample is initially dried at 400°C for 15 s, subsequently heated at 1200°C for 30 s, and copper is atomized at 2600°C for 10 s in an argon atmosphere (argon flow rate: 31/min). Peak areas of the copper signal at 324.7 nm are measured under background correction with the neon line at 320.8 nm. The relative standard deviation is 2.7% on 7 repeated measurements for the determination of 56 ppm copper in a standard silicate rock sample (JB-1).