When performing the ion-selective electrode test for fluoride, it is essential to add a substance known as TISAB, which stands for Total Ionic Strength Adjusting Buffer. TISAB is specifically formulated to maintain a consistent ionic strength and pH level, which is crucial for accurate and reliable measurements when using ion-selective electrodes.
The primary purpose of TISAB is to minimize interference from other ions present in the sample that could potentially affect fluoride ion measurements. It also helps to complex other anions, such as hydroxide or carbonate, that might otherwise react with fluoride, ensuring that only the fluoride concentration is being measured. By stabilizing the sample conditions, TISAB enhances the selectivity of the fluoride ion electrode and provides a more precise reading of fluoride levels in the sample being tested.
This context emphasizes the importance of standard practices in analytical chemistry, particularly in methods used for measuring specific ions in complex mixtures.