Method Scope: This method is used to determine low levels of calcium and magnesium, down to parts per billion (ppb) concentrations. Tetramethylammonium chloride salt solution is diluted to achieve a dissolved solid content of less than 5%.
Instruments:
1. Teledyne Leeman ICP
2. Standard laboratory glassware
Instrument Conditions: set the instrument conditions as follows:
· Plasma Observation: Axial mode
· RF Power: 1.2 kW
· Plasma Gas Flow: 20 LPM
· Auxiliary Gas Flow: 0.4 LPM
· Nebulizer Flow: 40 PSI
· Pump Flow: 1.2 ml/min
· Calcium Analytical Line: 317.933
· Magnesium Analytical Line: 279.553
Reagents/Chemicals:
1. Deionized water/Type 1 water for diluting samples for calcium content testing (<5 ppb calcium and magnesium).
2. 1000 ppm certified calcium standard solution.
3. 1000 ppm certified magnesium standard solution.
Precautions:♥ Maintain good personal hygiene while handling samples.♥ Keep the sample preparation and sample tray area clean and tidy.♥ Ensure a clean and organized space during the analysis.♥ Avoid gathering around the machine when analyzing calcium and magnesium in the ppb range.
Procedure:♠Note: If the dissolved solid content is less than 5%, water samples from various industrial processes can be directly aspirated into the ICP.
For tetramethylammonium chloride salt water samples, weigh approximately 10 g of the sample and dilute it to 50 ml mark in polycarbonate centrifuge tubes using tested deionized or calcium-free water. These tubes should be single-use only.
Calibration:Mixed standard solutions can be used to prepare calibration curves.
1. Pipette 5 ml of the calcium and magnesium standard solution (1000 ppm) from the 50 ml polycarbonate centrifuge tube and top up the volume with deionized or calcium-free water to obtain a 100 ppm equivalent calcium and magnesium standard solution.
2. Pipette 5 ml from the 100 ppm calcium and magnesium standard solution into a 50 ml polycarbonate centrifuge tube and top up the volume with distilled water or calcium-free water to obtain a 10 ppm stock-1 solution of calcium and magnesium.
3. Pipette 5 ml from the 10 ppm stock-1 solution into a 50 ml polycarbonate centrifuge tube and top up the volume with distilled water or calcium-free water to obtain a 1.0 ppm (1000 ppb) equivalent stock-2 solution of calcium and magnesium.
4. Now, pipette 0.5 ml, 1.0 ml, 2.5 ml, and 5 ml aliquots from the 1.0 ppm stock-2 solution into separate polycarbonate centrifuge tubes and top up the volume with deionized or calcium-free water to obtain 10 ppb, 20 ppb, 50 ppb, and 100 ppb equivalent calcium and magnesium standard solutions.
5. Use these standards to draw calibration curves by loading the appropriate method file from the instrument software.
6. Run the standards using the calibration curve method to obtain a linear graph.
7. Adjust the sample concentration to fall within the calibration graph.
8. Input the sample dilution factor and sample weight into the sample introduction window of the software to obtain the calcium and magnesium content directly from the tetramethylammonium chloride sample.
9. Perform calculations according to the following method:
concentration in ICP(ppb)x 50
metal content(ppb)= ----------------------------------------------
Sample weight (g)
