Calcium Standards

Reagents

• Calcium Hardness solutions CH1 and CH2, LaMotte # 7042-G and 7041-G

• Calcium Reference Standard Solution, 1000 ppb, Hach part # 2240349

• Distilled water

Equipment

List of vendors and prices: https://sites.google.com/iorodeo.com/colorimeter/equipment

• Colorimeter with custom 575 nm board

• Cuvettes

• 1 x 50 mL capped tubes

• 9 x 10 mL capped tubes

• Pippete pump

• 5 mL, 10 mL pipettes

Prepare Calibration Solutions

• Prepare 20 mL of a 250 ppm working stock from the 1,000 ppm calcium standard: add 5 mL of standard to 15 mL of distilled water. Mix.

• Dilute the working stock as outlined in the Table below

Method

• To each 5 mL sample, add 5 drops of CH1, mix then add 5 drops of CH2. An image of all of the calibration solutions after the reagents is shown above (to be added).

• Transfer approx. 1mL of each calibration solution to a cuvette.

• In the colorimeter plotting program, select the 575 nm LED and ppm as units. Calibrate the colorimeter with the 0 ppm calcium solution and measure absorbance of all of the solutions in duplicate.

Sample calibration data

• To view/use: Download the file and open in the colorimeter plotting software as described here.