Action and use
Used in the treatment of hyperkalaemia.
DEFINITION
Calcium Polystyrene Sulfonate is a cation-exchange resin prepared in the calcium form containing not less than 6.5% w/w and not more than 9.5% w/w of calcium, calculated with reference to the dried substance. Each g exchanges not less than 1.3 mEq and not more than 2.0 mEq of potassium, calculated with reference to the dried substance.
CHARACTERISTICS
A cream to light brown, fine powder.
Practically insoluble in water and in ethanol (96%).
IDENTIFICATION
A. The infrared absorption spectrum, Appendix II A, is concordant with the reference spectrum of calcium polystyrene sulfonate (RS 037).
B. Yields reaction C characteristic of calcium salts, Appendix VI.
TESTS
Particle size
Not more than 1% w/w is retained on a 150-μm sieve, Appendix XVII B. Use 20 g and sieve for 5 minutes.
Potassium
Not more than 0.1% of K when determined by atomic emission spectrophotometry, Appendix II D, measuring at 766.5 nm and using a solution prepared in the following manner. To 1.1 g of the substance being examined add 5 mL of hydrochloric acid, heat to boiling, cool and add 10 mL of water. Filter, wash the filter and residue with water and dilute the filtrate and washings to 25 mL with water. Use potassium standard solution (100 ppm K), suitably diluted with water, to prepare the standard solutions.
Sodium
Not more than 0.1% of Na when determined by atomic emission spectrophotometry, Appendix II D, measuring at 589.0 nm and using a solution prepared in the following manner. To 1.1 g of the substance being examined add 5 mL of hydrochloric acid, heat to boiling, cool and add 10 mL of water. Filter, wash the filter and residue with water and dilute the filtrate and washings to 25 mL with water. Use sodium solution (200 ppm Na), suitably diluted with water, to prepare the standard solutions.
Arsenic
1 g dispersed in 25 mL of water complies with the limit test for arsenic, Appendix VII (1 ppm).
Styrene
Carry out the method for liquid chromatography, Appendix III D, using the following solutions.
(1) Shake 10 g of the substance being examined with 10 mL of acetone for 30 minutes, centrifuge and use the
supernatant liquid.
(2) 0.0001% w/v of styrene in acetone.
CHROMATOGRAPHIC CONDITIONS
(a) Use a stainless steel column (30 cm × 4 mm) packed with octadecylsilyl silica gel for chromatography (μBondapak C18 is suitable).
(b) Use isocratic elution and the mobile phase described below.
(c) Use a flow rate of 2 mL per minute.
(d) Use an ambient column temperature.
(e) Use a detection wavelength of 254 nm.
(f) Inject 20 μL of each solution.
MOBILE PHASE
Equal volumes of acetonitrile and water.
LIMITS
In the chromatogram obtained with solution (1):
the area of any peak corresponding to styrene is not greater than the area of the peak in the chromatogram obtained with solution (2) (1 ppm).
Potassium exchange capacity
To 3 g of the substance being examined in a dry 250 mL glass-stoppered flask add 100 mL of a solution containing 0.7455% w/v of potassium chloride and 0.4401% w/v of potassium hydrogen carbonate in water (solution A), stopper and shake for 15 minutes. Filter and dilute 2 mL of the filtrate to 1000 mL with water. Determine the concentration of unbound potassium in this solution by atomic emission spectrophotometry, Appendix II D, measuring at 766.5 nm and using solution A suitably diluted with water, to prepare the standard solutions. Calculate the potassium exchange capacity of the substance being examined in milliequivalents taking the concentration of potassium in solution A as 144 milliequivalents of K per litre.
Loss on drying
When dried at 70° at a pressure not exceeding 0.7 kPa for 16 hours, loses not more than 8.0% of its weight. Use 2 g.
Microbial contamination
Carry out a quantitative evaluation for Enterobacteria and certain other Gram-negative bacteria, Appendix XVI B1. 0.01 g of the substance being examined gives a negative result, Table I (most probable number of bacteria per gram fewer than 102 ).
ASSAY
For calcium
Carefully heat 1 g in a platinum crucible until a white ash is obtained and dissolve in 10 mL of 2M hydrochloric acid with the aid of heat. Transfer the resulting solution to a conical flask using 20 mL of water. Add 50 mL of 0.05M disodium edetate VS, 20 mL of ammonia buffer pH 10.9 and titrate the excess of disodium edetate with 0.02M zinc sulfate VS, using a 0.5% w/v solution of mordant black 11 in ethanol (96%) as indicator to a red purple end point. Each mL of 0.05M disodium edetate VS is equivalent to 2.004 mg of Ca.
STORAGE
Calcium Polystyrene Sulfonate should be kept in an airtight container.
