Solid phase Fourier transform near infrared spectroscopy

Abstract

A novel flow methodology, integrating continuous solid phase spectroscopy with measurements in the near infrared region (NIR) has been developed, the NIR absorbance measurement being carried out on a C₁₈ solid phase located inside a flow-through cell. In this way, a simple and straightforward procedure has been developed for the determination of trace amounts of α-naphthylamine, used as a test molecule, in water samples. The method, based on peak area measurements between 5800 and 6060 cm^–1 of the coadded spectra obtained between 4 and 8 min after sample injection, is suitable for α-naphthylamine concentrations from 4 to 30 µg mL^–1 with a limit of quantification of 2 µg mL^–1. Recovery studies, carried out on natural samples spiked with known concentrations of amine, provided an average recovery value of between 92 and 106% and the relative standard deviation of three independent analyses of a seawater sample spiked at a concentration level of 16 µg mL^–1 of α-naphthylamine was 6.4%. The sampling frequency of the method corresponds to 6 h^–1.