Table 2.

Mean residual concentration (%), color changes, and final pH values of apomorphine HCl sample solutions (which were colorless initially) after 336 hours

Apomorphine HCl in different solutions	Experimental temperature (°C)	Mean residual concentration at 336 hours (%)*	Color of solution at 336 hours	Time (day) when color change was first observed	Period of time where mean residual concentration was within 95%–105% (hours)	pH at 336 hours#
0.1% AA	25	50.02	Copper	2	10	3.88
	32	50.98	Copper	1	10	3.93
	37	43.69	Copper	1	5	3.93
0.1% SMB	25	0.53	Very light yellow	11	<5	3.84
	32	0.05	Very light yellow	5	<5	3.63
	37	0.06	Light yellow	3	<3	3.45
0.1% EDTA	25	99.20	Light blue	4	>336	4.02
	32	90.17	Light blue	2	200	3.98
	37	84.58	Emerald	0	120	3.92
0.1% AA +0.1% SMB	25	99.73	Colorless	–	>336	3.94
	32	98.66	Colorless	–	>336	3.81
	37	95.86	Colorless	–	>336	3.64
0.1% AA +0.1% EDTA	25	85.26	Colorless	–	130	3.91
	32	70.12	Yellow	4	45	3.98
	37	74.51	Yellow	4	50	3.91
0.1% SMB +0.1% EDTA	25	88.37	Colorless	–	95	4.02
	32	77.53	Colorless	–	70	3.90
	37	70.72	Colorless	–	50	3.91
Water (without antioxidant)	25	94.68	Light blue	2	310	4.08
	32	81.23	Light blue	1	100	3.87
	37	56.84	Emerald	0	25	3.96

Notes: Apomorphine HCl sample solutions for each assay were prepared in duplicate (n=2). The initial concentration of sample solutions was 50 μg/mL.

^*The acceptable limit of mean residual concentration at the end of period of stability study is between 95% to 105%.

^#Initial pH was buffered by acetate buffer to pH 4.

Abbreviations: AA, L-ascorbic acid; SMB, sodium metabisulfite.