Lactulose determination in UHT milk by CZE-UV with indirect detection.

Lactulose is not found naturally in milk, but it has been detected in small quantities in heated dairy products. It can therefore be used as an indicator of the severity of heat treatment for dairy products. This study proposes an alternative method for lactulose quantification in milk using capillary zone electrophoresis with ultraviolet detection (CZE-UV). The investigation used several Brazilian UHT milk samples, and various sample pretreatment methods and injection conditions were considered. Optimal separation results were achieved using Carrez clarification solutions. Low detection and quantification limits were obtained, and good precision and high recovery rates indicated the applicability of the method for analysis of milk. Due to matrix effects, single-point standard addition was used for lactulose quantification. High lactulose concentrations (>1000 mg L) suggested that recirculation may have occurred during milk processing. The findings demonstrate that the CZE-UV method is a viable alternative for quality process control.