Combination of sequential injection analysis with an integrated [BF4]-potentiometric sensor for the kinetic determination of boron

Abstract This work deals with the development of a kinetic technique for boron determination based on the monitoring of a tetrafluoroborate-formation reaction carried out in a potentiometric cell integrated with a sequential injection system. A previously elaborated PVC-membrane electrode based on the active substance formed by the ion pair of 2-[3-(5,6-dimethyl-3-nonyl-1,3-benzothiazol-2(3 H )-ylidene)propenyl]-5,6-dimethyl-3-nonyl-1,3-benzothiazolium (DMNBT) with tetrafluoroborate ion was used. The metrological characteristics of the proposed sensor were tested in the presence and absence of F - in a concentration range of phosphoric acid from 0.1 to 7.0 M. The sensor is sensitive to tetrafluoroborate, with a slope of −56.5 ± 1.0  mV/pC and a LOD near pC min  = 6.7 , and can be applied for the monitoring of the tetrafluoroborate-formation reaction in acidified fluoride solutions containing up to 7.0 M H 3 P O 4 . The optimal reaction media that ensured sufficient difference in the response time of the sensor and the rate of [ B F 4 ] - appearance in the reaction media was 4.0 M H 3 P O 4 and 0.2 M N H 4 F . The H-point standard addition method (HPSAM) was applied for the evaluation of selectivity. Its application was based on the fact that the response time of the sensor to the appearance of tetrafluoroborate and interferents in the reaction media was totally different. The proposed method was successfully applied for the determination of boron in unmineralised honey samples. Reliability of the results was tested using the ICP-MS method.