Introduction[edit | edit source]
The metals content in a sample of water (for instance, Mg, Na, Pb, Fe, Zn, etc.) is a significant determinant of the quality of the water and its suitability for drinking purposes. This page outlines the protocol that can be followed to determine metals content, with a focus on the preparation required in order to run the test and how it is done at Analytical Services Unit (ASU) at Queen's University in Kingston, Ontario.
Analyses performed[edit | edit source]
- Total metals digest - at the ASU, this will analyse the "30 Element Suite" of the following metals:
Ag, Al, As, B, Ba, Be, Ca, Cd, Co, Cr, Cu, Fe, K, Mg, Mn, Mo, Na, Ni, P, Pb, S, Sb, Se, Sn, Sr, Ti, Tl, U, V, Zn
Instruments and materials[edit | edit source]
- Total digest performed at the ASU with a DigiPrep digestion block with a digital controller
- Samples are then analyzed at the ASU with a Varian Vista AX CCD Simultaneous ICP-AES
- 50 mL inert polymeric containers - one per sample
- 1.0M nitric acid
Note: The above materials are those that a student might have to work with at the ASU. For a complete list of materials used in the method suggested by the Environmental Protection Agency, see EPA Method 3052.
Procedure[edit | edit source]
Calibrating pipettes[edit | edit source]
- Set the pipette volume to 1500
- Place a small container at the center of the analytical balance and press "TARE"
- Withdraw a sample of deionized water with the pipette
- Add the water to the small container on the analytical balance
- If the mass displayed is within the defined boundaries of 0.1489g and 0.1510g, the pipette is sufficiently calibrated
Preparing samples for digest[edit | edit source]
- In case the metal has not completely dissolved in the solution, the sample must first be mixed with concentrated nitric acid (1.0M):
- Add 25 mL of completely mixed sample to an inert container
- Add 2 mL of acid to the sample
- Repeat for all samples
- Place all the samples, without a cap, inside an incubator set at 90 degrees Centigrade and heat for 300 minutes.
- After the samples have been heated, they will need to be diluted again. Add enough deionized water to each sample to bring the volume to 25 mL.
- Place a cap on each sample and submit the set to the lab technician at the ASU.
Digesting the metals[edit | edit source]
Results[edit | edit source]
At Queen's, the results will be provided in table form with control values provided. Concentrations will be provided in parts per million (ppm).