Ranitidine (RNT) has been an important tertiary amine precursor of N-nitrosodimethylamine (NDMA) in chlorine-based water treatment, due to reaction with monochloramine (NH₂Cl) with exceptionally high molar yields up to 90%. This study examined the effects of nitrite ions (NO₂⁻) on the kinetics of NDMA formation during the chloramination of RNT under variable concentrations of dissolved oxygen (DO, 0.7–7.5 mg/L), RNT (5–30 μM), NH₂Cl (5–20 mM), NO₂⁻ or NO₃⁻ (0–2 mM) and pH (5.6–8.6). In the absence of the NO₂⁻, the ultimate molar yield of NDMA after 6 h of reaction was primarily influenced by [DO] and pH, while marginally affected by initial [RNT] and [NH₂Cl]. A kinetic model, prepared in accordance with the reaction sequence of NDMA formation, suggested that the rate determining step was accelerated with increasing [NH₂Cl]₀, [DO], and pH. A Kinetic study together with ultra-performance liquid chromatography-quadrupole-time of flight mass spectrometer (UPLC-Q-TOF MS) and gas chromatography (GC)/TOF MS analyses in parallel demonstrated that the nitrite ion inhibited the nucleophilic substitution of the terminal amine on NH₂Cl, and reduced the pseudo-steady state concentration of N-peroxyl radicals, significantly decreasing the ultimate yields of NDMA.

雷尼替丁（RNT）在氯基水处理中一直是N-亚硝基二甲胺（NDMA）的重要叔胺前体，这是因为它与一氯胺（NH ₂ Cl）反应的摩尔产率高达90％，异常高。本研究亚硝酸根离子的效果（NO ₂ ^- RNT的溶解氧的浓度可变（DO，0.7-7.5毫克/升），RNT（5-30μM），NH下氯胺期间的NDMA形成的动力学）₂氯（5-20毫米），NO ₂ ^-或NO ₃ ^-（0-2毫米）和pH值（5.6-8.6）。在没有NO ₂的情况下^-，反应6小时后NDMA的最终摩尔产率主要受[DO]和pH的影响，而受起始[RNT]和[NH ₂ Cl]的影响很小。根据NDMA形成的反应顺序制备的动力学模型表明，速率确定步骤随着[NH ₂ Cl] ₀，[DO]和pH的增加而加速。动力学研究与超高效液相色谱-四极杆飞行时间质谱仪（UPLC-Q-TOF MS）和气相色谱仪（GC）/ TOF MS并行分析表明，亚硝酸根离子抑制了末端的亲核取代胺在NH ₂ Cl上，降低了N的拟稳态浓度-过氧自由基，大大降低了NDMA的最终收率。