Rapid, accurate, and precise concentration measurements of a methanol-water mixture using Raman spectroscopy

TL;DR

This paper presents a compact Raman spectroscopy sensor capable of measuring methanol-water mixture concentrations with high accuracy and precision within seconds, suitable for harsh environments and adaptable to other liquids.

Contribution

The authors design and validate a portable Raman sensor that achieves sub-percent accuracy and sub-0.01% precision in liquid concentration measurements.

Findings

Accuracy of 0.5% in concentration measurement

Precision as low as 0.006% with longer measurements

Stable performance over 11 days with minimal drift

Abstract

Here we design, construct, and characterize a compact Raman-spectroscopy-based sensor that measures the concentration of a water-methanol mixture. The sensor measures the concentration with an accuracy of 0.5% and a precision of 0.2% with a 1 second measuring time. With longer measurement times, the precision reaches as low as 0.006%. We characterize the long-term stability of the instrument over an 11-day period of constant measurement, and confirm that systematic drifts are on the level of 0.02%. We describe methods to improve the sensor performance, providing a path towards accurate, precise, and reliable concentration measurements in harsh environments. This sensor should be adaptable to other water-alcohol mixtures, or other small-molecule liquid mixtures.