A: Infrared Absorption 197K.

B: A solution (1 in 10) responds to the tests for Chloride 191.

Test solution: 100 mg per mL, in water.

Borate buffer— Transfer about 1.24 g of boric acid to a 100-mL volumetric flask, dissolve in 90 mL of water, and adjust with 5 N sodium hydroxide to a pH of 9.0, dilute with water to volume, and mix.

Standard solution— Dissolve an accurately weighed quantity of USP Aminobutanol RS in water, and dilute quantitatively, and stepwise if necessary, to obtain a solution having a known concentration of about 5 µg per mL.

Fluorescamine solution— Dissolve 5 mg of fluorescamine in 50 mL of acetone in a glass-stoppered, graduated cylinder.

Test solution— Transfer about 50 mg of Ethambutol Hydrochloride, accurately weighed, to a 100-mL volumetric flask, dissolve in and dilute with water to volume, and mix.

Procedure— Pipet a 10-mL portion of Test solution into a glass-stoppered, 100-mL conical flask, and add 10 mL of water and 20 mL of Borate buffer. To another 100-mL flask add 10.0 mL of Test solution, 10.0 mL of Standard solution, and 20 mL of Borate buffer. Place the flasks on a magnetic stirrer, and while the contents are being stirred rapidly, add 10 mL of Fluorescamine solution rapidly. Insert the stoppers in the flasks, invert, and shake briefly. After 1 minute, accurately timed, determine the relative fluorescence intensities of both solutions in 1-cm cells, with a suitable fluorometer, at about 485 nm, with the excitation wavelength at about 385 nm. The fluorescence intensity of the solution obtained from the Test solution is not greater than the difference between the intensities of the two solutions (not more than 1.0%).

Test solution: methanol.

Standard solution: methanol.

Eluant: a mixture of methanol and ammonium hydroxide (18:1).

Visualization: 16.

(Official January 1, 2007)