A new borate ion selective electrode using solid salts of Ag3BO3, Ag2S and Cu2S has been developed. Detailed information is provided concerning the composition, working pH and conditioning of the electrode. An analytically useful potential change occurred from 1 x 10(-6) to 1 x 10(-1) M borate ion. The slope of the linear portion was 31 +/- 2 mV/10-fold changes in borate concentration. The measurements were made at constant ionic strength (0.1 M NaNO3) and at room temperature. The effect of Cl-, Br-, NO3-, SO4-, H2PO4- anions and K+, Na+, Cu2+, Ag+, Ca2+ cations on borate response is evaluated and it was found that only Ag+ had a small interference effect. The lifetime of the electrode was more than two years, when used at least 4-5 times a day, and the response time was about 20-30 s. Borate content in waste water of borax factory, tap water of a town situated near to the borax factory and city tap water far from these mines were also determined. The validation was made with differential pulse polarography for the same water sample, and high consistency was obtained. (C) 2011 Elsevier B.V. All rights reserved.