In-Line Concentration Measurement of Nanoliter Liquid Sample Using Low-Coherence Spectral Interferometry

A method for in-line measurement of the refraction index and the concentration of binary liquid mixture in a nanoliter volume is presented. Low-coherence spectral interferometric technique, based on fiber optic Mach-Zehnder interferometer, is applied for measuring the liquid refraction index, from which its volume fractions are found. The accuracy of volume fractions measurement, of about plusmn0.2%, was predominantly determined by the accuracy and resolution of reading the light spectrum. The data rate has been limited to 40 Hz by the time of the light spectrum capturing