Determination of free and total acidity in small volumes ? development of a FIA-gradient mixing technique

Application of Flow Injection Gradient Titration Based on the Standard Addition and Dilution Procedure to the Determination of Total Acidity in Vinegars and Soft Drinks

“…Some authors have classified this titration as "pseudotitration". [5][6][7][8][9] Flow injection gradient titration has been exploited for various determinations, among them systems can be found for determination of: acids; [10][11][12] acidity in: vinegars, 12 raindrops, 13 oils 14,15 and fruit juice; 16 surfactants; 9,17 amines and their salts; 8 and phenothiazine derivatives. 18 The principles of various procedures dedicated to acidity determination using flow injection titration are similar; however, various instrumental solutions can be found.…”

“…18 The principles of various procedures dedicated to acidity determination using flow injection titration are similar; however, various instrumental solutions can be found. In the examples cited above, a small volume (between 4.5 13 and 500 12 mL) of undiluted sample or sample diluted by an organic solvent 15 is injected into a stream of titrant (usually a solution of sodium or potassium hydroxide). In the case of spectrophotometric detection, an indicator (phenolphthalein, 12,[14][15][16] m-cresol purple 13 ) is added to the titrant directly [12][13][14] or a stream of titrant is mixed with a stream of indicator.…”

“…In the examples cited above, a small volume (between 4.5 13 and 500 12 mL) of undiluted sample or sample diluted by an organic solvent 15 is injected into a stream of titrant (usually a solution of sodium or potassium hydroxide). In the case of spectrophotometric detection, an indicator (phenolphthalein, 12,[14][15][16] m-cresol purple 13 ) is added to the titrant directly [12][13][14] or a stream of titrant is mixed with a stream of indicator. 15,16 The linear correlation between analytical signals measured as widths 12,15 or areas 14,16 of the signals registered and the logarithm of sample acidity is observed over a relatively wide acidity range.…”