None of the three methods used in the MPFREE Standard measures the same thing. Here's the actual difference.
Micro-Fourier-transform infrared spectroscopy (µFTIR) shines infrared light through a particle and matches the absorption spectrum against a reference library to identify the polymer. Its conventional practical size floor is around 20 µm [1]; below that, particle-to-noise ratio degrades and confident identification gets difficult. Newer variants like large-area ATR-FTIR have pushed detection down to roughly 1.3 µm in research settings [2], but that isn't yet the routine floor most accredited labs run at scale.
Raman microspectroscopy uses a different physical mechanism (inelastic light scattering rather than absorption) but produces a similar output: particle count plus polymer identity via spectral matching. Its finer laser spot size gets it down to about 1 µm in practice [3] — an order of magnitude below conventional µFTIR. The tradeoff is analysis speed and, historically, the cost of comprehensive reference libraries, though open-access libraries have started closing that gap [4].
Pyrolysis-gas chromatography–mass spectrometry (Py-GC-MS) works completely differently: it thermally decomposes the entire sample and identifies polymers from their breakdown products. It reports mass, not particle count — commonly down to nanogram levels across a dozen common polymers [5] — and because it destroys the sample, it produces no data on particle size, shape, or count [6].
That's precisely why it matters for the sub-1-µm range neither optical method can resolve: Py-GC-MS doesn't have a size floor at all, because it isn't sizing anything — it's measuring total polymer mass, including whatever nanoplastic fraction is present. A standard built on only the two optical methods would have a structural blind spot below about 1 µm; that's the specific gap this third method is there to close.