Abstract

The coupling of gel-electrophoresis (GE) with laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) has been used to measure the binding of lead to various molecular size fractions of humic and fulvic acids. Stable isotopic tracers were utilised to separate the metals bound initially to the acids from those bound experimentally. Ultimately, this technique will allow the determination of the binding capacity of the acids for trace metals. Humic or fulvic acids were equilibrated with a stable isotopic metal tracer (²⁰⁶Pb). Sodium dodecyl sulfate polyacrylamide gel electrophoresis was used to separate humic and fulvic acids as a function of size. Gel plates containing the separated acids were dried and mounted on a microscope slide. Laser ablation was used to sample the plates at 50–100 µm intervals with the ablated material being analyzed by inductively coupled plasma mass spectrometry. Added metal and carbon concentrations were measured simultaneously. The results can be used to determine variation in metal binding as a function of organic acid size and for fingerprinting organic acids from natural systems.