ICP-MS analysis method: Methods of elemental analysis
How the elements we know occur and to what extent they are relevant to medicine has already been described in previous articles. After completing the pre-analytical process, which includes the selection of suitable test material, the next question is how the element analysis should be measured. Harald Hagendorfer, Deputy Managing Director and Head of “Special Analytics” at our partner laboratory Ortho-Analytic explains the complex ICP-MS procedure of the Aniveri Analysis.
In principle, there are three different methods of element analysis.
- Firstly there is photometry, which measures the absorption of light. This method is only applicable to elements in very high concentrations.
- With spectroscopy, electrons are excited by a flame or plasma, thus generating a measurable emission. Concentrations can be measured to the range of micrograms per litre.
- However, if you want to measure the whole spectrum of elements in different concentration ranges, from mg/L to ng/L, you need mass spectrometric methods. Inductively coupled plasma mass spectrometry, or ICP-MS for short, has become the gold standard in the field of element analysis.
ICP-MS: The Aniveri Analysis method in detail
How does the ICP-MS (inductively coupled plasma mass spectrometry) used for the Aniveri Analysis work? The solid sample, in our case the hair, must first be converted into liquid form. The first step is to prepare the samples for the analysis process by removing external contamination. We have developed a complex washing procedure and coordinated the standard values of the analysis to it. Next the sample must be converted from a solid to a liquid form. The Aniveri ICP-MS analysis uses a microwave decomposition technique to achieve fully mineralized samples. The hair is mineralized and dissolved with nitric acid under pressure and temperatures of up to 250°C.
The prepared samples are then fed into the ICP-MS using an autosampler. First the sample is atomized and droplets larger than 10 µm are separated using a spray chamber. The resulting homogeneous aerosol is then transported into the inductively coupled argon plasma. The temperatures generated by the plasma are comparable to those of the sun’s surface: between 6,000 and 8,000 degrees Celsius. A long scientific development process was required to ensure the process could be conducted in such a safe and controlled way. The first prototypes were created in the early 1980s, and the first routine measuring devices came onto the market at the end of the 1990s.
The droplets are immediately vaporized in the plasma itself and their molecules are atomized and positively ionized. The ions can then be extracted in a high vacuum, separated and detected by mass and charge. The ICP-MS method enables you to measure all elements of the periodic table with a few exceptions (oxygen, nitrogen, carbon and fluorine). Furthermore, the ICP-MS method also allows the total element analysis to be automated. 25 years ago this required equipment the size of an entire office room, but today it is about the size of an office desk.
Always under control: the ICP-MS measurement
To maintain the quality of the measurements, we have a complex quality assurance system that was developed over many years and is continually being improved. The entire procedure is validated according to the specifications of the ISO 15189 standard for medical diagnostics. Before each individual measurement, we check and calibrate the analysis device using NIST-certified standards. The US “National Institute of Standardization” is one of the few institutions to offer such stocks and all standards used in the process can be traced back to these stocks.
Before the actual samples are measured, quality control samples that have a certified content of elements undergo measurement. This material also goes through the entire sample preparation process to rule out any errors here as well. This is followed by the measurement of the prepared patient samples and a further check using the quality control samples. To avoid carryover between the samples, blank controls are also measured. As an integral part of the quality assurance system, our Ortho-Analytic laboratory analyses interlaboratory test samples three times a year. The Canadian “Institut national de santé publique du Québec” sends us unknown hair samples, which we measure using the method just described. Depending on the reported results, the laboratory receives an annual evaluation. To date we have passed all ring tests in the last six years.
What does modern element analysis enable?
In summary, by using the most modern analytical methods we gain deeper insights into the supply levels of trace elements and minerals, as well as the heavy metal load. Automated analysis with precisely defined processes and corresponding quality assurance makes this analysis affordable for end consumers. So it is no longer only accessible to larger research institutes and industry. There is another benefit to the multi-element capability of the ICP-MS method: We analyse 38 elements at the same time, so we can give a more comprehensive picture and determine correlations between trace element supply and heavy metal pollution.