Fluoroborate-selective electrode

Analysis. Fluoroboric acid solutions and fluoroborates are analyzed gravimetricaHy using nitron or tetraphenylarsonsium chloride. A fluoroborate ion-selective electrode has been developed (21). 

Fluoride. A fluoride concentration of ca 1 mg/L is helpful in preventing dental caries. Eluoride is deterrnined potentiometrically with an ion-selective electrode. A buffer solution of high total ionic strength is added to the solution to eliminate variations in sample ionic strength and to maintain the sample at pH 5—8, the optimum range for measurement. (Cyclohexylenedinitrilo)tetraacetic acid (CDTA) is usually added to the buffer solution to complex aluminum and thereby prevent its interference. If fluoroborate ion is present, the sample should be distilled from a concentrated sulfuric acid solution to hydrolyze the fluoroborate to free fluoride prior to the electrode measurement (26,27). 

Ion-selective electrode -determination of silver [SILVER COMPOUNDS] (Vol 22) -for fluoride analysis pLUORINE COMPOUNDS, INORGANIC - INTRODUCTION] (Vol 11) -for fluoroborates pLUORINE COMPOUNDS, INORGANIC - BORON - FLUQROBORIC ACID] (Vol 11) -for hydrogen ion activity [HYDROGEN-LON ACTIVITY] (Vol 13)... 

Certain positively charged ion-exchangers can be used for anion-selective electrodes. Charged metal salts of appropriately substituted orthophenanthrolines— M(o-phen)3 —result in good electrodes for nitrate, fluoroborate, or perchlorate by forming ion-association complexes with these anions. The CIO " electrode, in particular, has few interferences and perchlorate is a difficult ion to measure by almost any other method. A dimethyl-distearyl-ammonium ion, R N, can be used as an ion-exchanger in an electrode that has fair selectivity for chloride. 

A commercially available fluoroborate ion-selective indicator electrode was used for the potentiometric titration of surfactants and soaps.The titrants were HDTAC, hexadecylpyridinium chloride (HDPC), and diisobutylphenoxy-ethoxyethyI-(dimethyI)benzyIammonium chloride (DIPEBC). Similarly, Benoit et al. " titrated CTAB with sodium tetraphenylborate potentiometrically using a commercial CI04 selective electrode. The method proved to be precise exhibiting a relative standard deviation of 1.1 %. 

The use of polymer electrodes is much more convenient compared to liquid electrodes. Also, their parameters are often better, e.g., their longer lifetime. Since the first use of polymer electrodes, many sensors of this type have been constructed. They can be selective towards alkaline metals, the metals of alkaline soils, heavy metals, non-organic anions, nitrates, chlorides, carbonates, phosphates or anionic and cationic organic compounds. There are also Ion-selective polymer electrodes available on the market. They include, among others, nitrate, chloride, fluoroboric, potassium, and calcium electrodes (Table 8.1). 

Jezkova J, Musilova J, Vytfas K (1997) Potentiometry with perchlorate and fluoroborate ion-selective carbon paste electrodes. Electroanalysis 9 1433-1436... 

Concerning the determination of surfactants, in 1997 Vytras s group demrai-strated that carbon paste-based electrodes could also be used as potentiometric sensors to monitor titrations of surfactants.When compared to PVC and CW electrodes, CPEs had the advantages of very low Ohmic resistance, very short response time in addition to the ease of fabrication and regeneration as well as long functional lifetime. Jezkova et al. used perchlorate and fluoroborate ion-selective carbon paste electrodes for both direct potentiometric measurements and potentiometric titration of perchlorate or fluoroborate with 0.1 M CPC. The electrodes had a rapid response, low Ohmic resistance, and limits of detections and selectivity similar to the limits of commercial membrane electrodes. A carbon paste electrode incorporated with the ion association of CPC-thallium halo complexes was applied as indicator electrode with the potentiometric titration of surfactants. ... 

---