Increased concern about the growing sensitivity of 193 nm optics to airborne molecular contaminant has led to the determination of trace levels of NH3 in photolithography cleanrooms become increasingly concerned.In this study, the cleanroom air (~ 216 1) was collected into a teflon glass impinger containing DI water with a battery-operated personal sampler.An ion chromatograph-based method for determining trace NH3 as NH+4 was developed.The method minimized the background contamination from analytical system and procedure, aiming to reduce false positive detection as the background NH3 in cleanroom was ultra low.