Applied_Spectroscopy_Practica_01_01 - 31

Kara Ali et al.
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Table II. Determination of the Cy and H content in PS samples
collected at specific steps of the recycling process as determined
using the combined PLS model.
Sample
Precipitated paste
Cy (wt%) H (wt%) Spectrum fit (%)
11.4 ± 0.2 15.7 ± 0.4 99.2
Washed paste (W1) 3.1 ± 0.2 20.2 ± 0.6 98.8
Washed paste (W2) 2.5 ± 0.1 21.8 ± 0.1 98.8
Pellet (W1)
Pellet (W2)
1.6 ± 0.3 0.5 ± 0.5 99.8
0.8 ± 0.4 0 ± 2
99.8
of the single-solvent models. The Cy content decreases from
a large value of 11.4% in the precipitated pastes to 3.1% or
2.5% after washing the paste with H. Meanwhile, the H content
increases up to ∼22% for the washed paste W2, slightly
more than for W1. The results obtained for the pellets are
consistent, within quantification error, between the Cy-only
model (Table I) and the Cy + H model (Table II). This is
understood when noting that the H content in the pellets
is indeed within the determination uncertainty of the Cy +
H model, so the Cy-only model was indeed applicable.
When considering the propagation of the errors on all components
of the system, the limit of detection of the model is
estimated to be 0.5% for Cy and 1% for H, even though the
sample-to-sample replicability is better. These limits of detection
are not competitive with mass spectrometry for an accurate
determination of the residual solvent content in pellets.
Nevertheless, IR spectroscopy allows quantification of large
solvent contents, up to 60% for H and 20% for Cy, with relative
errors on the order of 2-3% and reproducibility on the

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