New ionophores for vitamin B1 and vitamin B6 potentiometric sensors for multivitaminic control.

The construction, evaluation and analytical application of potentiometric sensors sensitive to vitamin B1 and vitamin B6 are reported. The solid contact electrodes were produced using beta-cyclodextrins as ionophores in a carboxylated poly(vinyl chloride) support matrix. Near Nernstian slopes (mV/decade) of 51.7+/-0.8, 60.6+/-0.6 and 61.1+/-1.4, within the intervals (M) of 1.0 x 10(-4) to 1.0 x 10(-1), 5.8 x 10(-5) to 1.0 x 10(-1) and 4.3 x 10(-5) to 1.0 x 10(-1) were obtained, for thiamine and pyridoxine I and II prepared membranes, respectively. A pH operational range of 6.5-8.5 for thiamine and 2-4.5 for pyridoxine electrodes was found. Assessment of selectivity coefficients toward a large number of inorganic cations and organic cations usually present in multivitamin formulations revealed good performance. Analysis of vitamins B1 and B6 in complex multivitamin drugs was achieved with recoveries within the intervals of 95.1-99.6% for thiamine and 95.1-102% for pyridoxine. Furthermore, the results enabled by the proposed procedure revealed good agreement with those provided by HPLC.