The absorbance
of TPPO in the resulting spectra, which paralleled the response
illustrated in Fig. 3,was measured at 542 cm−1 relative to a baseline
point at 530 cm−1 and plotted against the concentration of
TPPO, expressed in units of equivalent PV. Fig. 4 illustrates a
typical standard curve obtained using a 540 m cell, and the
corresponding linear regression equation is presented below.