Atomabsorption mit gesteuerter flüssigkeitszufuhr zum turbulenzbrenner

Abstract

The solution volume aspirated per unit time by a total consumption burner depends on various parameters and cannot be preselected at will. By means of external control of the solution uptake rate, the application range of total consumption burners can be extended considerably. Using a piston pump, the behaviour of the burner was investigated at solution uptake rates from 0.1 to 6.0 ml min . The flame parameters, hydrogen and air flow rates as well as the height of the light beam above the burner tip, were varied up to values of 30 and 8 l min respectively 8.2 cm. For the evaluation of the flame properties, the atomic absorption of potassium, magnesium and chromium was measured. Three total consumption burners with different diameters of the capillaries were tested. The results showed that these burners can be properly operated, even when sample flow rates were externally adjusted to higher or lower amounts as compared to free aspiration conditions. The accessible concentration range is thus extended by about one and a half order of magnitude. Best results are achieved with burners with narrow capillaries. The optimum values of the other flame parameters (gas flow rates, height of light beam) vary little with the solution uptake rate. The shape of the calibration curves and the efficiency of the apparatus are discussed in terms of the solution uptake rate. Operation of total consumption burners with externally controlled solution flow rates offers a number of advantages which can be used for routine work. With the aid of a peristaltic pump and an automatic sampler, the apparatus can be extended reliably for series analyses. The pulsation of the peristaltic pump was smoothed by a damping device. This system has proved its usefulness since more than three years.