Lithium Brine Testing- Methods for Analysis
In part one of this two part series, we provided an overview of WETLAB’s industry leading practices for Lithium Brine Testing. In part two, we will explore the strengths and limitations associated with each of the four testing methods, including ICP-OES- the preferred method of brine characterization.
WETLAB is an industry leader for lithium brine testing, and has excelled at characterization using ICP-OES. The four main methods of lithium brine testing each have its own strengths and limitations, which we explore below.
FAAS (Flame Atomic Absorption Spectroscopy) involves a nebulized sample being passed through an acetylene flame and the light absorbance of a specific wavelength is then measured. Some of the potential limitations involved with FAAS characterization include low sensitivity, relatively low ionization temperature (3000°C), and only one analyte can be run at a time. Phosphates and Sulfates can also form flame-stable metal salts, which can complicate analysis.
GFAAS (Graphite Furnace Atomic Absorption Spectroscopy) involves the sample being heated in a graphite tube, and then atomized light is passed through the tube and measured at a specific wavelength. Due to heating programming and specificity, GFAAS analyses are typically done for one element at a time. GFAAS also has long sampling times, low temperature, and a limited dynamic range.
ICP-MS (Inductively Coupled Plasma – Mass Spectrometry) involves a nebulized sample being passed through high temperature plasma to ionize atoms, which are then isolated by their mass/charge ratio and detected directly. ICP-MS can be an excellent option for some clients, but some of the limitations for lithium analysis are that lithium is very light and can be excluded by heavier atoms, and analysis is typically limited to <0.2% dissolved solids, which means that it is not great for brines. Equipment and technician training costs are also very high with this method.
ICP-OES (Inductively Coupled Plasma – Optical Emission Spectroscopy) involves a nebulized sample being passed through high temperature plasma to ionize atoms, which release light at specific wavelengths. This is the preferred analytical technique for most metals in any matrix, and all metals in a complex matrix such as brine solutions. ICP-OES can handle a high amount of dissolved solids, has little chemical interference, and has robust sample introduction with high-energy plasma (~10,000°C) plasma. ICP-OES can also perform multi-element analysis, easily determining concentrations of other metals (K, Mg, B, etc). Although ICP-OES is the preferred technique, it does have some limitations. These include moderate detection limits, typically lower than FAAS but higher than GFAAS and ICP-MS in a clean matrix. Complex matrices (such as brine) can often require dilutions from the other methods that may raise the overall Detection Limit. Also, spectral Interferences are common, but can typically be easily compensated to eliminate.
To determine how WETLAB can help you get the data you need with our industry leading practices, call WETLAB at (775) 355-0202 and speak with someone from our highly skilled customer and sample management team.