Table 1.

A vaccine sample concentration (ng/ml) obtained from calibration curve

Optical density (450 nm)					Vaccine sample conc (ng/ml)
Std Conc (ng/ml)	Values	Mean	SD	CV%	Values	Mean	SD	CV%
5	0.413 0.352	0.3825	0.043134	11.31	2039 2350	2194	219	10
50	0.441 0.426	0.4335	0.010607	2.44
500	0.638 0.635	0.6365	0.002121	0.31
5000	1.459 1.471	1.465	0.008485	0.54
50,000	1.806 1.699	1.7525	0.07566	4.28

Standard curve was based on five serial dilutions of ETX with a concentration range of 5 to 50,000 ng/ml.

CV%: Coefficient of variation expressed as percentage; Std conc Standard concentration; SD Standard deviation.