Total Organic Carbon Content in Aqueous Samples Determined by Near-IR Spectroscopy

We describe the application of near-infrared spectroscopy with partial least-squares (PLS) multivariate calibration to determine the total organic carbon (TOC) content of aqueous organic samples. We demonstrate a standard error of precision of approximately 0.50 mg/mL for the TOC content in aqueous organic mixtures of Na3HEDTA, Na4EDTA, and acetone. The precision of the simultaneous determination of each component in these samples is 1.66 mg/mL (0.0044 M) for Na3HEDTA, 2.62 mg/mL (0.0063 M) for Na4EDTA, and 0.38 mg/mL (0.0065 M) for acetone. Transmission spectra were collected by using a 1 mm pathlength and approximately 1 min collection time in the 6250–5450 cm−1 (1.60–1.83 μm) region, corresponding to the first C–H overtone band. This analysis procedure was developed to ease TOC determination for hazardous aqueous wastes such as those found at the DOE Hanford site.