When the sodium alginate is dissolved into water, the sodium ions are separated from the carboxyl groups. When calcium ions are introduced into solutions, these ions associate with the carboxyl groups and form a precipitate. The long alginate chains are bound together by calcium and form a cross-linking matrix. This is a hydrogel.
Dye
The dye used in this project represents a substitute of the drug that would be held in the hydrogel. Once the hydrogel beads are formed and are dissolving in distilled water, the concentration of the dye released into the distilled water is measured to determine the release rate of the dye.
The two main factors that need to considered when deciding on a dye include:
- Molecular weight of the dye - Higher molecular weight is preferred because a dye that is too light would release too quickly.
- Color of the dye - Choose a dye that would appear well in the spectrum data.
Absorbance and Beer's Law
Absorbance:
Absorbance is a derived measure of the amount of light that is not permitted through a substance. A UV/vis spectrophotmeter measures the light sent through a sample and compares it to a reference to find the absorbance. UV and visible light are the most commonly used wavelengths because absorbances in other ranges are affected by structural properties of the solute.
Beer's Law:
Absorbance is directly proportional to concentration. A = e*L*c
Where L is length, a constant; e is a molar absorbance constant, a constant; and c is concentration.
L and e can be absorbed into a single constant.
Where L is length, a constant; e is a molar absorbance constant, a constant; and c is concentration.
L and e can be absorbed into a single constant.