Research on dual-wavelength photometric method for micro liquid volume measurement

In order to overcome the shortcoming of significant influence of evaporation capacity on gravimetric method and meet the requirement of online measurement, dual-wavelength photometric method is introduced for measuring microliquid volume. Based on Lambert-Beer law, this paper introduces the dual-wavelength photometric method (DWP method) at 520 nm and 730 nm, which can measure the microliquid volume through the linear relation between the concentration of dilute solution and the absorbance. Comparing to gravimetric method, an experimental system for dual-wavelength photometric method was designed. Experimental results indicate that the test result obtained by using DWP method was better than obtained by using gravimetric method, and met the technical requirement of ISO 8655. Compared with the gravimetric method, the non-gravimetric methods can provide a better solution for microliquid volume measurement, which was less stringent for measurement environment, easy to realize the online calibration and capable of reducing the influence of liquid evaporation.