Dilute concentrated hydrochloric acid 1:4 with distilled water.
CAUTION: ALWAYS ADD ACID TO WATER WITH GREAT CARE. NEVER ADD WATER TO
CONCENTRATED ACID.
Blank Preparation:
2.5ml of diluted hydrochloric acid 2.0ml 10% lanthanum chloride Make up to 100ml with distilled water. This gives reagent blank.
Standard Preparation:
Take Sherwood part 00156623(1000 mg/l Ca)and dilute to give standards of 2.5, 5.0, 7.5 and 10 ppm
Ca,
Sample Preparation:
Place 4g (accurately weighed) of milk in a dry silica
crucible.
Ash sample at 500--525°C oven. When cool, dissolve ash in 5ml of 1:4 diluted concentrated hydrochloric acid.
Transfer to 100ml volumetric flask; make up to mark.
Filter through Whatman filter paper, pipette 25ml of filtrate into 100ml volumetric flask. Add 2ml of 10% lanthanum chloride. Make up to mark with distilled water.
Method:
Spray reagent blank - set zero.
Spray 10 ppm standard set Display to read 10.0.
Reset zero.
Spray intermediate standards, note readings to check linearity.
Spray test samples and note readings.
For percent calcium in original sample Multiply Ca ppm sample reading by 0.01 = percent Ca in milk. Normal level for
milk, approximately 0.11 %.
