Place 254.6 g of isopropyl alcohol and 7.9 g of water in a conical flask having a ground-glass joint. Add a quantity of Methacrylic Acid Copolymer, accurately weighed and equivalent to 37.5 g of solids on the dried basis, while stirring by means of a magnetic stirrer. Close the flask, and continue stirring until the polymer has dissolved completely. Adjust the temperature to 20 ± 0.1
. Equip a suitable rotational viscosimeter with a spindle having a cylinder 1.88 cm in diameter and 6.25 cm high attached to a shaft 0.32 cm in diameter, the distance from the top of the cylinder to the lower tip of the shaft being 0.75 cm, and the immersion depth being 8.15 cm (No. 1 spindle). With the spindle rotating at 30 rpm, immediately observe and record the scale reading. Convert the scale reading to centipoises by multiplying the reading by the constant for the viscosimeter spindle and speed employed.
Change to read:
Limit of monomers
pH 2.0 Phosphate buffer, 0.025 MNF24
Prepare an aqueous solution containing 3.550 g of
dibasic sodium phosphate (Na2
) and 3.400 g of monobasic potassium phosphate (KH2
) per L. Adjust with phosphoric acid to a pH of 2.0.
Prepare a solution in methanol to contain 700 mL of pH 2.0 Phosphate buffer, 0.025 MNF24
Prepare a solution in methanol to contain an accurately known concentration of about 2.4 µg per mL each of methacrylic acid and either methyl methacrylate (for Type A and Type B) or ethyl acrylate (for Type C). To 50.0 mL of this solution, add 25.0 mL of water, and mix.
Dissolve about 40 mg of Methacrylic Acid Copolymer, accurately weighed, in 50.0 mL of methanol, add 25.0 mL of water, and mix.
Chromatographic system (see Chromatography 621)
The liquid chromatograph is equipped with a 202-nm detector and a 4-mm × 12.5-cm column that contains 5-µm packing L1. The flow rate is about 2.5 mL per minute. Chromatograph the Standard solution
, and record the peak responses as directed for Procedure:
the resolution, R,
of each pair of analytes is not less than 2.0; the capacity factors, k¢,
for methacrylic acid, ethyl acrylate, and methyl methacrylate are 1.7, 4.3, and 4.8, respectively; and the relative standard deviation for replicate injections determined from each analyte is not more than 2%.
Separately inject equal volumes (about 50 µL) of the Standard solution
and the Test solution
into the chromatograph, record the chromatograms, and measure the responses for the major peaks. Calculate the quantity, in µg, of each monomer in the portion of Methacrylic Acid Copolymer taken by the formula:
75C(rU / rS)
in which C
is the concentration, in µg per mL, of the monomer in the Standard solution;
are the peak responses for the monomer obtained from the Test solution
and the Standard solution
, respectively. Not more than 0.05% of total monomers is found.