1000 ml of water is added to each vessel. INTRODUCTION It is useful to have preliminary information on the structural formula, the vapour pressure, the dissociation constant and the hydrolysis (as a function of pH) of the substance to perform this test. 1) Water Solubility Place approximately 0.1 g or 0.2 mL (2-3 drops) of compound in a small test tube, and add about 1 mL of water in small portions. 1.1. A soluble unknown will form a homogeneous solution with water, while an insoluble liquid will remain as a separate phase. o Solubility should ideally be measured at two temperatures: 4°c and 37°c. This method is based on the elution of a test substance with water from a microcolumn which is charged with an inert carrier material such as glass beads, silica gel, or sand, and an excess of test substance. METHOD The methods desctibed are based on the OECD Test Guideline (1). The goal was to develop HPLC methods for the analysis of all nine water-soluble vitamins using DAD-ELSD and LCMS. - 37°c to support biopharmaceutical evaluation. Also, it discusses the methods to empirically estimate the intrinsic solubility of compounds. Three samples of 10 g of particles of the test substance are weighed into each of three vessels fitted with glass stoppers. A.6 WATER SOLUBILITY 1. The second part of the project was expanded to include the other four water-soluble vitamins (niacinamide B3, pantothenic acid B5, biotin B7 and folic acid B9). This chapter provides an overview of the concepts and equations related to thermodynamic equilibrium and solubility. Procedure for Determining Solubility of Organic Compounds. Tap the tube with your finger to mix or stir gently with a glass stirring rod. dissolution or in vitro release testing. This Test Guideline describes a method to analyse the solution/extraction behaviour of polymers in water, which uses the flask method with modifications. - 4°c to ensure physical stability. The water solubility is determined when the mass concentration of the eluate is constant. This is shown by a concentration plateau as a function of time in the following figure 1: Keep away from flames or other heat sources. The U. S. Pharmacopeia is proposing the new General Chapter <1236> Solubility Measurements (2). SOLUBILITY o One way of measuring solubility is to determine the maximum mass of solute that can be dissolved in 100 ml of solvent at a particular temperature. Add 1 drops of a liquid sample or about 25 mg of a solid sample to 0.5 mL of distilled or deionized water in a test tube. Performing the Water Solubility Test CAUTION—Unknowns may be flammable, toxic, corrosive, or irritating. ELSD is a universal detector that responds more or less Shake test tube vigorously after the addition of each portion of solvent. 1) Water Solubility Add approximately 6 drops of water to the test tube containing your unknown. No single method is available to cover the whole range of solubilities in water. Shake the tube and/or stir with a glass stirring rod.