Extract from Manual:
U. S. Environmental Protection Agency. 1983.
Calcium: Method 215.1 (atomic absorption, direct aspiration). pp.
215.1-215.2. In Methods for Chemical Analysis of Water and
Wastes, EPA-600/4-79-020. U.S.E.P.A., Cincinnati, Ohio, USA.
Method 215.1 (Atomic Absorption, direct aspiration)
STORET NO. Total 00916
Optimum Concentration Range: 0.2-7 mg/l using a wavelength of 422.7 nm
Sensitivity: 0.08 mg/l
Detection Limit: 0.01 mg/l
Preparation of Standard Solution
1. Stock Solution: Suspend 1.250 g of CaCO3 (analytical reagent grade),
dried at 180 degrees C for 1 hour before weighing, in deionized
distilled water and dissolve cautiously with a minimum of dilute HCI.
Dilute to 1000 ml with deionized distilled water. 1 ml = 0.5 mg Ca (500
2. Lanthanum chloride solution: Dissolve 29 g of La203, slowly and in
small portions, in 250 ml conc. HCI (caution: reaction is violent) and
dilute to 500 ml with deionized distilled water.
3. Prepare dilutions of the stock calcium solutions to be used as
calibration standards at the time of analysis. To each 10 ml volume of
calibration standard and sample alike add 1.0 ml of the lanthanum
chloride solution, i.e., 20 ml of standard or sample + 2 ml LaCI3 = 22
1. For sample handling and preservation, see
[part 4.1] of the Atomic Absorption Methods section of this manual.
1. For the analysis of total calcium in domestic and industrial
effluents, the procedures for the determination of total metals as given
in [parts 4.1.3 and 4.1.4] of the Atomic
Absorption Methods section of fthis manual have been found to be satisfactory.
2. For ambient waters, a representative aliquot of a well-mixed sample
may be used directly for analysis. If suspended solids are present in
sufficient amounts to clog the nebulizer, the sample may be allowed to
settle and the supernatant liquid analyzed directly.
Instrumental Parameters (General)
1. Calcium hollow cathode lamp
2. Wavelength: 422.7 nm
3. Fuel: Acetylene
4. Oxidant: Air
5. Type of flame: Reducing
1. For analysis procedure and calculation, see "Direct Aspiration", [part 9.1] of the Atomic Absorption Methods
section of this manual.
1. Phosphate, sulfate and aluminum interfere but are masked by the
addition of lanthanum. Since low calcium values result if the pH of the
sample is above 7, both standards and samples are prepared in dilute
hydrochloric acid solution. Concentrations of magnesium greater than
1000 mg/1 also cause low calcium values. Concentrations of up to 500
mg/1 each of sodium, potassium and nitrate cause no interference.
2. Anionic chemical interferences can be expected if lanthanum is not
used in samples and standards.
3. The nitrous oxide-acetylene flame will provide two to five times
greater sensitivity and freedom from chemical interferences. Ionization
interferences should be controlled by adding a large amount of alkali to
the sample and standards. The analysis appears to be free from chemical
suppressions in the nitrous oxide-acetylene flame. (Atomic Absorption
Newsletter 14, 29 ).
4. The 239.9 nm line may also be used. This line has a relative
sensitivity of 120.
5. Data to be entered into STORET must be reported as mg/l.
6. The EDTA titrimetric method may also be used (Standard Methods, 14th
Edition, p. 189).
Precision and Accuracy
1. In a single laboratory (EMSL), using distilled water spiked at
concentrations of 9.0 and 36 mg Ca per l, the standard deviations were
+/- 0.3 and +/- 0.6, respectively. Recoveries at both these levels were