Potential use of/evaluation of laser-induced breakdown spectroscopy for in-line monitoring of cleaning-in-place processes

The present work illustrates a novel approach of the use of laser-induced breakdown spectroscopy (LIBS) for in-line monitoring of cleaning-in-place (CIP) processes. The aim was to develop an in-line setup for LIBS measurements in aqueous solutions and its demonstration on a pilot plant for industrial CIP processes. The experiments were conducted using a metal target inside the liquid. After initial measurements in NaCl and CaCl₂ solutions, a model system representing milk (containing a milk-like salt solution, simulated milk ultrafiltrate (SMUF)) was analysed. Sodium, calcium and potassium were detected with a signal-to-noise ratio of 16 for Na, 15 for Ca and 2 for K. Furthermore, the influence of the flow velocity inside the pilot plant on the LIBS signal was tested. It was observed that an increase in flow velocity led to a decrease in the line intensity. These results show the potential of LIBS for the monitoring of CIP processes and the in-line measurement of aqueous solutions in general.