Determination of boron concentration in oilfield water with a microfluidic ion exchange resin instrument

We developed and validated a microfluidic instrument for interference-free determination of boron in produced water. The instrument uses a boron-specific chelating resin to separate the analyte from its complex matrix. Ten produced water samples were analyzed with the instrument and the results were successfully validated against ICP-MS measurements. Removing interference effects enables precise boron measurement for wastewater even with high total dissolved solid (TDS) levels. 1,4-Piperazinediethanesulfonic acid conditions the resin and maintains the optimum pH for boron adsorption from the sample. Boron is then eluted from the resin using a 10% sulfuric acid solution and its concentration measured with the colorimetric carminic acid assay in 95% sulfuric acid. The use of a microfluidic mixer greatly enhances the sensitivity and kinetics of the carminic acid assay, by factors of 2 and 7.5, respectively, when compared against the same assay performed manually. A maximum sensitivity of 2.5mg−1L, a precision of 4.2% over the 0–40.0mgL−1 measuring range, a 0.3mgL−1 limit of detection, and a sampling rate of up to four samples per hour were achieved. Automation and microfluidics reduce the operator workload and fluid manipulation errors, translating into safer and higher-quality measurements in the field. [Display omitted] •We developed a ion exchange resin instrument to measure boron in water.•PIPES buffer was used to condition the sample to the optimum resin pH.•With microfluidics, we greatly improved the performance of the carminic acid assay.•We validated the instrument on 10 produced water samples.