There are a few options for testing lead in water that can be used with Vernier products. Please pay close attention to the chemicals required and use appropriate caution.
One option for testing lead uses a colorimetric method based on a lead-dithizone complex. In a weak alkaline solution, dithizone can form a stable complex with lead in a 2:1 ratio . This complex has a maximum absorbance at 520 nm. This option uses Chloroform and Potassium Cyanide. The Lead Reagent Set (Dithizone Method) can be purchased from Hach (Product Number 2243100).
The following spectrophotometers can be used. A Vernier Colorimeter can’t be used with this test.
Go Direct® SpectroVis® Plus Spectrophotometer (GDX-SVISPL) *Glass cuvettes are required.
Vernier Spectrometer (V-SPEC)
Vernier UV-VIS Spectrophotometer (VSP-UV)
Vernier Fluorescence/UV-VIS Spectrophotometer (VSP-FUV)
LaMotte also has a Lead Screening Test Kit for Drinking Water (Order Code 5-0140) that detects lead levels above 15 ppb which is the EPA action level.
The Go Direct® Cyclic Voltammetry System (GDX-CVS) can measure lead in water. However, the only fairly reliable way to do it uses mercury. This can be a problem for some schools, so we haven’t written a formal experiment around it. It’s also important to note that the GDX-CVS doesn’t do DPV (differential pulse voltammetry), but it can perform ASV (anodic stripping voltammetry) by performing two experiments in sequence.
After preparing the SPE with a thin layer of mercury (by bulk electrolysis), ASV is just:
- A bulk electrolysis while stirring solution, such that lead ion amalgamates with the Hg layer by a reduction process (Pb2+ + 2e → Pb (amalgam)) – known as the “concentration” phase; then
- A linear sweep voltammetry experiment (i.e., cyclic voltammetry with n = 1 segment) to oxidize Pb (amalgam) to Pb2+ (i.e. sweep from – potential to +potential), which is what is measured and compared to a calibration curve to find unknown Pb2+ concentration.
So, if you aren’t scared of using mercury acetate to form a thin film of mercury on the SPE, then you should look at Pine’s lab exercise and adapt it to using the GDX-CVS. You can review that lab here.
Vernier does not offer a lead ISE.
A Lead Ion-Selective Electrode with a BNC connector is commercially available but can’t be used with our Electrode Amplifier (EA-BTA) or the Go Direct® Electrode Amplifier (GDX-EA). The amplifier can accommodate electrode outputs from -80 mV to 300 mV. Typically Lead ISEs fall outside of this range (-100 to -240 mV). See Can I use my third-party ISE with my Vernier equipment?