Even though it is currently expensive, Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) is the predominant method now used in clinical reference labs that measure heavy metals. In the past, flame photometry and atomic absorption were used but these methods were more cumbersome, slower, and less sensitive than ICP-MS.
In ICP-MS, a small amount of the patient sample is introduced into a hot (6000–10,000 K) argon plasma. This atomizes the sample into individual ionized atoms. These atomic ions can then be separated by the quadrupole units in the MS and quantified based on their mass-to-charge (m/z) ratio. The more atoms of a specific m/z ratio there are, the greater the signal from the detector will be, and thus, atoms can be quantitated. Notice that this method will atomize all the elements in a sample. So when operating in this mode, it is not possible to discriminate different forms or compounds, for example, cadmium, only total cadmium concentration can be ascertained.
The most significant advantage of ICP-MS is its multi-element capability. One instrument can detect multiple elements simultaneously in a single analysis or one instrument can be used to measure multiple heavy metals, increasing the lab's test offerings. This is in contrast to the older methods of flame and graphite furnace atomic absorption where each metal tested had to have a specific lamp that could only be used for that particular element. ICP-MS has a short analysis time, requires little sample preparation, and offers a very high sample throughput for laboratories.
