Separation and determination of metallocyanide complexes of Fe(II), Ni(II) and Co(III) by ion-interaction chromatography with membrane suppressed conductivity detection applied to analysis of oil refinery streams (sour water)

A separation and determination method for the analysis of cyanometallic complexes of Fe(II), Ni(II) and Co(III) was developed to be applied to the analysis of petroleum refinery streams (sour water). Ion-interaction chromatography was used employing an analytical column IonPac NS1 10 μm and a chromatographic system ICS 2500 equipped with a membrane conductivity suppression ASRS ultra 4 mm, both supplied by Dionex Corporation. The mobile phase was composed of 2 mmol l−1 TBAOH, 1 mmol l−1 Na2CO3, 0.1 mol l−1 NaCN and ACN (77:23, v/v), flowing at 0.7 ml min−1. At the optimized conditions, detection limits estimated by the calibration curve parameters and relative standard deviation were: 0.002 mg CN l−1 and 3.1% for Fe(CN)64−; 0.003 mg CN l−1 and 2.5% for Ni(CN)42− and 0.003 mg CN l−1 and 2.8% for Co(CN)63−. Sour water samples without any pretreatment (except membrane filtration) from a petroleum refinery in Brazil were analyzed successfully by external calibration method.