Chemical Interference
Concentrated electrolyte environments dominated by sodium ions alter the ion-selective behavior of standard glass pH electrodes during alkaline textile wet processing. A high sodium background occurs in reactive dye baths where sodium sulfate or sodium chloride is added to force dye exhaustion onto cotton fibres. Glass membranes respond to sodium ions as if they were hydronium ions when hydrogen ion activity is extremely low.
This ion exchange phenomenon creates a false low hydrogen activity signal in heavily salted process baths above nine pH. The resulting deviation creates errors in chemical dosing calculations for soda ash additions during reactive fixation stages.
Measurement Distortion
Electrochemical potential measurements read falsely low under high alkali salt conditions. The glass membrane exchanges sodium ions across its outer hydrated gel layer, generating a secondary potential that depresses the apparent pH reading. Uncorrected errors lead operators to add excess alkali, damaging cotton fibres through hydrolysis.
Tailored Calibration
Tailored sodium-resistant glass formulations reduce ion interference in concentrated dye liquors. Laboratories calibrate sensors using multi-point buffer solutions containing matching background salt concentrations. Matrix-matched calibration aligns probe response with true hydronium ion activity.
Application Limit
Conventional glass pH electrodes fail to deliver reliable measurements once sodium ion concentration exceeds one mole per litre in hot dye liquors. A high sodium background mandates the use of specialized glass membranes or ISFET sensors in concentrated reactive dye baths. Standard glass electrodes produce uncorrectable drift under these conditions.
