Detection of chlorine and chloramines in dialysis water

Objective Exceeding chlorine and chloramines in dialysis water is harmful to human body, but most dialysis centers in China can only measure chlorine content. The aim of the current study was to evaluate the safety only based on chlorine content, as well as the accuracy of TMB visual colorimetry. Methods Levels of chlorine and chloramines in dialysis water and tap water were measured using both TMB visual colorimetry and DPD spectrophotometry, and values from DPD spectrophotometric method were used as the golden standards. Dialysis water and tap water from 9 dialysis centers were assayed every hour and ten times per day for two days. Linear regression was used to explore the relationship between chlorine and chloramines in dialysis water, and P 0.05 was considered statistically significant. Kappa test was used to compare the difference between the values from DPD spectrophotometry and those from TMB visual colorimetry. Results Concentrations of chlorine and chloramines in dialysis water were below the standards recommended by AAMI at every time point. There was no linear relationship between chlorine and chloramines contents in dialysis water (r =0.14, P =0.1460). TMB visual colorimetry gave a false negative rate of 100% with kappa=0 for free chlorine measurement, and a false negative rate of 10.67% with kappa=0.88 for total chlorine measurement as compared with the values from DPD spectrophotometry, Conclusion For dialysis water, monitoring free chlorine alone is probably unsafe, and chloramines or total chlorine should also be measured. Compared to DPD spectrophotometry, TMB visual colorimetry gives a remarkable false negative rate, suggesting the preferential use of DPD spectrophotometry method if possible.