L. Han et al., Enhancing IR detection limits for trace polar organics in aqueous solutions with surface-modified sol-gel-coated ATR sensors, APPL SPECTR, 53(4), 1999, pp. 381-389
An experimental investigation into the use of surface-modified solgel-coate
d Si attenuated total reflectance (ATR) mid-infrared sensors was completed
to determine the detection limits for trace amounts of polar organic molecu
les in aqueous solutions. The surfaces of porous sol-gel films were modifie
d to be mostly hydrophobic in order to concentrate the polar organic analyt
es in the film while largely excluding the water solvent. This modification
of the Si ATR sensor coupled with multivariate partial least-squares calib
ration methods allowed approximately three orders of magnitude improvement
in detection limits for acetone when compared to detection limits from univ
ariate analysis of spectra obtained on uncoated Si ATR sensors. The compara
ble improvement for isopropanol in aqueous solution was over two orders of
magnitude, Studies performed on mixtures of acetone and isopropanol in wate
r confirmed that quantitative analyses could be performed on these mixture
systems with cross-validated standard errors of prediction (CVSEP) of 0.5 a
nd 8.7 ppm, respectively. Using three times the CVSEP as an estimate of the
detection limit translates to detection limits of 1.5 and 26 ppm for aceto
ne and isopropanol, respectively.