Determination of phosphate in water samples of Saudi Arabia

A new method has been adopted for determination of phosphate in water samples of Saudi Arabia by potentiometric technique using lead ion selective electrode. Phosphate was precipitated in nitric acid medium as phosphomolybdate complex and the excess st and ard molybdate solution was determined with st and ard lead nitrate solution in the presence of lead ion-selective electrode. Phosphate was also determined by a new spectrophotometric method, which measured the chloroformic extract obtained from the conjugate molybdenum blue complex with rosaniline at 540 nm. Beer's law was obeyed in the concentration range of 5.6 to 56.2 mug phosphate per 25 ml with molar absorptivity of 89954.3 L Mol -1 cm -1. These procedures were compared statistically with the method, which uses anion exchange resin in the molybdate form

Determination of some catecholamines in pharmaceutical forms

Periodic acid oxidized catecholamines to the corresponding aminochrome derivatives which could be measured spectrophotometrically in acetate buffer [pH 4.7] at 485 nm in the range of 2.4 to 28 mug per ml catecholamines. Catecholamines were also determined amperometrically after their oxidation with periodic acid. In addition, a fluorometric method for the determination of primary amine, e.g. catecholamines, noradrenaline and methyldopa was established. O-phthalaldehyde reacts with these amines in the presence of certain thiol [2-mercaptoethanol] and 50% ammonium acetate to give fluorescent adducts with excitation at 340 nm and emission at 455 nm. Beer's law was obeyed in the concentration range of 1.0 to 12.0 mug per ml catecholamines