Magnesium (Mg 2+): Perkin Elmer AAnalyst 100 Atomic Absorption Spectrometer

I) Principle

The ground state magnesium atom absorbs light energy at 285.2 nm as it enters the excited state.  As the number of magnesium atoms in the light path increases, the amount of light absorbed also increases.  By measuring the amount of light absorbed, a quantitative determination of the amount of magnesium present can be made.  0.5 % lanthanum solution is added to each standard and sample to prevent chemical and ionization interference.

 

II) Preparation of Stock Standard

In a 1000-mL volumetric flask, dissolve 8.3632 g magnesium chloride (MgCl₂.6H₂O) to the mark with deionized water. This standard stock solution is

1000 mg Mg²⁺/L.

 

III) Preparation of Reagents

0.5 % Lanthanum Solution

In a 1000-mL volumetric flask, dissolve 13.37 g lanthanum chloride (LaCl₃.7H₂O) to the mark with deionized water.

 

IV) Analysis Procedure

A) Dilute each standard and sample 9:10 with 0.5 % Lanthanum Solution (1 part 0.5 % Lanthanum Solution and 9 parts standard or sample).

B) Install a Ca-Mg hollow cathode lamp. Perkin-Elmer part #N305-0202.

C) Ensure that the correct Default Conditions are entered.

1) Recall Method=4

2) Lamp Current=15

3) Slit=0.7

4) Full Height=Y(Yes)

5) Wavelength(nm)=285.2

6) Int. Time=5.0

7) Replicates=5

8) Cal=1(Nonlinear)

9) Cal=1(Hold)

10) STD1____

11) Read Delay(sec)=3

D) Use an oxidizing (lean, blue)air-acetylene flame.

E) Calibrate with standards that bracket the sample concentration.  Correlation coefficient should be greater than or equal to 0.990.  Check the calibration curve for drift, accuracy and precision with standards and controls every 20 samples.