A new chromium carbon paste electrode sensor based on a carbon paste electrode containing 1-[(2-hydroxy ethyl) amino]-4-methyl-9H-thioxanthen-9-one (AMTX) as new carrier has been prepared. The influence of carbon paste ingredients including sodium tetraphenylborate (NaTPB), ionophore, Nujol and graphite powder on the electrode response has been investigated. The best performance characteristics for the electrode was obtained with a carbon:NaTPB:Nujol:AMTX in the mass ratio of (400:1.43:57.2:3 mg) (86.65:0.31:12.39:0.65%). At the optimum value of all variables, the response of electrode is linear in range of 3.2 x 10(-7) to 1.0 x 10(-1) mol L-1 with a Nernstian slope of 20.51 mV decade(-1) of Cr3+ ion concentration with detection limit of 1.6 x 10(-7) mol L-1. The electrode response is independent of pH in the range of 4.8-6.3, while the response time of the electrode was similar to 8 s. The potentiometric selectivity coefficients of proposed chromium-selective electrode towards various interfering ions were determined by fixed interference method (FIM), separate solution method (SSM) and matched potential method (MPM). (C) 2010 Published by Elsevier B.V.