What the technique measures
ICP-MS means inductively coupled plasma mass spectrometry. A prepared sample enters a plasma that produces ions; the mass spectrometer distinguishes them by their mass-to-charge ratio. Several elements can be measured from one preparation. Spain’s National Institute of Silicosis describes its use for trace and ultratrace analysis in workplace-air samples. High sensitivity still requires a clearly defined target, a suitable method and adequate quality control throughout the analysis.
A method for workplace air
INSST method MTA/MA-073/A26 addresses filter collection followed by ICP-MS analysis of metals and their ionic compounds. Gases, vapours and organic metal compounds are outside its stated scope. Whether the inhalable, thoracic or respirable fraction is collected depends on the sampler. Changing the analytical technique afterwards cannot turn an unsuitable collection into a representative sample of a different aerosol fraction or recover material that never reached the sampling medium.
Why preparation matters
Collected particles must be brought into solution using a procedure compatible with the sample. Incomplete digestion may leave some metal unmeasured. INSST requires the effectiveness of preparation to be checked where suitability for a material is uncertain. Deposits on sampler walls must also be considered where they form part of the sample. Transport, material loss and contamination can affect the result before the instrument begins its measurement.
Interferences and quality controls
High sensitivity makes contamination from reagents, filters and containers important. Other ions may interfere with the signal of the target element. Blanks, internal standards, calibration checks and correction procedures are chosen according to the method and matrix. An instrument producing a number is not enough: the laboratory needs evidence that the result is usable within the analytical range and that the relevant quality controls have remained acceptable.
An element is not necessarily a chemical species
Ordinary elemental analysis does not automatically identify the original chemical form. Measuring total chromium, for example, does not replace a specific method for hexavalent chromium. Air results are also not equivalent to biological monitoring of blood or urine: the sample, meaning and interpretation differ. Decide beforehand whether the question concerns total metal, a soluble fraction or a particular species, then confirm that the procedure answers it.
Keep the sampling context with the report
Record the method, requested elements, collected fraction, air volume, task and duration. Check report units, quantification limits, uncertainty and comments on recovery or incidents. Measured mass needs the sampled volume before it can be expressed as an airborne concentration. A low result does not establish control throughout an entire shift: the sampling strategy must represent the exposures under evaluation, including relevant changes in work activity.
