Optimization of leakage detection system for vials based on two-line tunable diode laser absorption spectroscopy

The leakage detection system of vials based on two-line water-vapor tunable diode laser absorption spectroscopy (TDLAS) developed in our previous work was first employed to investigate the instantaneous leakage processes of sealed vials. It showed that the leakage states of the vials with medicines cannot be accurately determined in a short time after the opening. Therefore, an optimized system was developed with two-line oxygen TDLAS method by the measurement of defined oxygen leakage coefficient, and it was then utilized to study the instantaneous leakage processes of sealed vials. It revealed that when the stoppers of the sealed vials were opened, the oxygen leakage coefficients increased immediately and then reach stable. It indicated that the optimized system was not affected by the water absorption of medicines. Furthermore, 15 vials with known leakage states were measured. It showed that the oxygen leakage coefficients of fully-open vials were obviously larger than that of sealed vials, and the maximum standard deviation of oxygen leakage coefficients for ten measurements of a single vial was 0.03%. The sealed vials with different leakage degrees were then investigated by inserting the needles with different sizes (0.5/1/2/3.5 mm) into the vials. It revealed that the time required for the oxygen leakage coefficients to reach stable was shorter for the vials with larger leakage degree, i.e., larger needle size inserted. It showed that non-invasive, fast response and high-accuracy leakage detection of vials can be realized by the optimized system.