In this study, four electrodes based on unmodified graphite (G) and graphite modified with iron (II) phthalocyanine (Fe(II) Pc), nickel (II) phthalolocyanine (Ni(II) Pc) and Chitosan from crab shells (Ch) were compared and evaluated for determination of nitrites in different types of water samples using differential pulse anodic voltammetry. For the Ni(II) Pc modified graphite sensor, a high sensitivity (6.62 x 10(-8) A mg L-1) and a lower quantification limit (0.0014 mg L-1) were obtained in comparison with G (sensitivity of 3.23 x 10(-8) A mg L-1; LOD of 0.0040 mg L-1 and LOQ of 0.0046 mg L-1) and Fe(II) Pc/G (sensitivity of 3.13 x 10(-8) A mg L-1; LOD of 0.0032 mg L-1 and LOQ of 0.0460 mg L-1). For the modified graphite microsensor based on Chitosan from crab shells a lower limit of detection (0.0002 mg L-1) and a lower limit of quantification (0.0005 mg L-1) were obtained. The unmodified graphite microsensor has a detection limit of 0.0040 mg L-1 for nitrite. These microsensors are indeed all suitable and reliable to employ for the assay of nitrite in different types of water samples from aquatic ecosystems in Romania with an RSD less that 0.11%. (C) 2018 The Electrochemical Society.