Novel microsampling system for automated spectrophotometry

Abstract

To enhance the performance of a conventional pulse width modulation (PWM)-based microsampling system, a novel system was developed by bifurcating a fluidic path and by reusing the conventional components. A micro-metering valve was newly equipped to control the speed of the sample introduction, and a reflective optical sensor was used to detect the arrival of a sample. In addition, an analog logic circuit was designed to minimize the response time of the control system. This approach features precise microsampling, rapid response, and stable operation. To verify the volumetric sampling performance and to understand the operational characteristics, a series of experiments were performed. The results show that the aspirated volume was maintained at about 2.8 microliters and that the aspiration requires less than 0.3 seconds. Moreover, the sample removal operation was performed identical to a conventional PWM-based microsampling system. Because our spectrophotometer is operated automatically, the reduction of the sampling time is highly advantageous to measure many samples. Therefore, the total measurement time may be reduced proportional to the number of samples to be analyzed.