2.6 Determination of Calcium in mineral water by AAS

The amount of calcium in a water sample has to be determined quantitatively by AAS

utilizing external calibration method.

Standard solutions with a concentration of 1, 2, 3, 4 und 5 mg/L are prepared by

appropriate dilution of a stock solution (c = 1000 mg/L) with 18 MΩ water in 100mL

volumetric flasks. 1 mL buffer solution (10 g/L CsCl / 100 g/L LaCl3-buffer) is added to

each standard before the flask is filled up with distilled water

The water sample is degassed in an ultrasonic bath 1 mL Cs/La-chlorid-buffer is

added before the flask is filled up with distilled water.

18 MΩ water is used to establish zero absorbance. The five calibration standards are

analyzed starting with the lowest concentration followed by the sample prepared for

external calibration. Each solution is measured at least three times. The samples of

the standard addition methode are analyzed in the same way starting with the lowest

concentration.

Instrument Set-up:

Ca-Lamp, 20 mA current, wavelength 422.7 nm, slit 0.7 nm; integration time 3s

The results have to be calculated using linear regression of the average absorption

values.

Result: Mean (g in 250 ml solution) confidence interval (standard

deviation, number of measurements, 95%). Take care of significant digits!

Rounding is only applied to the final result!