Disinfection by-products (
DBPs) in
drinking water have caused worldwide concern due to their potential carcinogenic effects. The formation of
phenazine from
diphenylamine (
DPhA) chloramination was studied and its cytotoxicities for two human
cancer cells were also investigated.
Phenazine was detected synchronously with the consumption of
DPhA by chloramination, which further confirmed that the new DBP
phenazine can be produced along with
N-nitrosodiphenylamine (NDPhA) from
DPhA chloramination. The formation of
phenazine had a maximum molar yield with
solution pH increasing from 5.0 to 9.0, with
phenazine as the main product for
DPhA chloramination at lower pH, but higher pH favored the formation of NDPhA. Thus,
solution pH is the key factor in controlling the formation of
phenazine and NDPhA. Both the initial
DPhA and
chloramine concentrations did not show a significant effect on the molar yields of
phenazine, although increasing the
chloramine concentration could speed up the reaction rate of
DPhA with
chloramines. The cytotoxicity assays showed that
phenazine had significant cell-specific toxicity towards T24 (
bladder cancer cell lines) and HepG2 (hepatic tumor cell lines) cells with IC50 values of 0.50 and 2.04 mmol/L, respectively, and T24 cells being more sensitive to
phenazine than HepG2 cells. The IC50 values of
phenazine,
DPhA, and NDPhA for T24 cells were of the same order of magnitude and the cytotoxicity of
phenazine for T24 cells was slightly lower than that of NDPhA (IC50, 0.16 mmol/L), suggesting that
phenazine in
drinking water may have an adverse effect on human health.