Annali di Chimica, 97, 2007, by Società Chimica Italiana 213 POTENTIOMETRIC BATCH AND FLOW INJECTION ANALYSIS OF BETAINE HYDROCHLORIDE Sayed S. BADAWY 1 , Ahmed F. A.YOUSSEF (°)1 , and Ali A. MUTAIR 2 1, Chemistry Department, Faculty of Science, Cairo University, Giza, Egypt. 2, Chemistry Department, Faculty of Science, Taiz University, Taiz, Yemen Summary - Novel PVC membrane electrodes for the determination of betaine ion based on the formation of betaine-tetraphenylborate (Be-TPB) and betaine- phosphotungstate (Be-PT) ion-exchangers as electroactive materials are described. The sensors show a fast, stable, near Nernstian response for 6.92 × 10 -6 to 7.94 × 10 -3 M and 1.0 × 10 -4 to 1.0 × 10 -2 M betaine hydrochloride (Be.Cl) in case of Be-TPB electrode applying batch and flow injection analysis (FIA), respectively, and 2.95 × 10 -5 to 2.26 × 10 -3 M and 3.16 × 10 -5 to 1.0 × 10 -2 M in case of Be-PT electrode for batch and FIA electrodes, respectively, at 25 °C over the pH range of 3.5-10 with a cationic slope of 60.2 and 59.1 mV decade -1 and a fast potential response of ≤ 15 s. The lower detection limits are 7.94 × 10 -6 and 3.18 × 10 -5 M Be.Cl for Be-TPB and Be-PT electrodes, respectively. Selectivity coefficient data for some common inorganic cations, sugars, amino acids and the components other than betaine, of the mixed drug investigated show negligible interference. The electrodes have been applied to the direct potentiometric determination of betaine hydrochloride in water and in a pharmaceutical preparation under batch and FIA conditions. Potentiometric titrations of Be.Cl with NaTPB and PTA as titrants were monitored with the developed betaine electrodes as an end point indicator electrode. The determination of Be.Cl shows an average recovery of 100.8 % with mean relative standard deviation of 0.61 %. The effect of temperature on the electrodes was also studied. INTRODUCTION Betaine is used as a methyl donor to remethylate homocysteine to methionine in the treatment of patients with homocystinuria. It has also been used as a variety of salts in preparations for liver and gastrointestinal disorders. The hydrochloride has been given as a source of hydrochloric acid in the treatment of hypochlorhydria. 1 Several analytical techniques have been reported for the quantitative determination of Be.Cl in pure solutions and pharmaceutical preparations. Among these are HPLC, 2-7 TLC, 8 capillary electrophoresis, 9 spectrophotometry, 10-12 MS, 13 NMR 14,15 and titration methods. 16-18 Potentiometric methods with ion selective electrodes (ISE's) can provide valuable and straightforward means of assaying drugs in complex mixtures, as they make possible the direct (°) Corresponding author; Fax: +20-2-5728843; E-mail address: ayoussef@chem-sci.cu.edu.eg ; hmdyssf@yahoo.com