NITRITE (NO2-), AS A INORGANIC CONTAMINANTS IN DRINKING WATER, HAVE PROVEN TO BE OF GREAT RISK TO HUMAN HEALTH [1]. THUS IT CAN BE ATTRACTIVE TOPIC FOR RESEARCH IN ANALYTICAL CHEMISTRY AND DEVELOPING A RAPID, HIGHLY SENSITIVE, AND SELECTIVE DETECTION OF NO2-IS EXTREMELY ESSENTIAL FOR HUMAN LIFE SAFETY. HERE, WE OFFER A SIMPLE METHOD TO NO2-RECOGNITION BASED ON ITS ABILITY TO ETCHING GOLD nanoparticle (AU NPS, SYNTHESIZED WITH CITRATE REDUCTION) SURFACE [1]. THIS EFFECT RESULTS IN A NOTABLE DECREASE IN NPS SURFACE PLASMON RESONANCE (SPR) WHICH IS LINEARLY PROPORTIONAL TO NO2-CONCENTRATION. ON THE OTHER HAND, NPS SIZE CAN HAVE A REMARKABLE EFFECT ON THIS PHENOMENON. BASED ON THIS EFFECT, NO2-DETERMINATION WAS TESTED BY USING DIFFERENT SIZES OF AU NPS AND IT WAS SHOWED THAT AU NPS WITH SIZE OF 8 NM IN DIAMETER CAUSED MORE SENSITIVE DETECTION COMPARED WITH OTHER SIZES. THE DIMINUTION EFFECT OF NO2-ON THESE NPS IS LINEARLY ALTERED OVER THE CONCENTRATION RANGES OF 8-120 MMOL L-1. THE LIMIT OF DETECTION WAS 2.4 MMOL L-1, AND OTHER COMMON ANIONS NEARLY HAVE NO NOTABLE INFLUENCE. THE METHOD WAS SUCCESSFULLY APPLIED TO THE DETERMINATION OF NO2-IN WATER SAMPLES.