Table 2.

Precision data for the determination of methocarbamol and guaifenesin applying the proposed method

Drug	Intra-day precision		Inter-day precision
	Conc. taken (µg/mL)	Mean* %found ± SD	Conc. taken (µg/mL)	Mean* %found ± SD
Methocarbamol	20.0	98.65 ± 0.05	20.0	98.88 ± 0.29
	40.0	97.86 ± 0.15	40.0	98.06 ± 0.41
	100.0	98.41 ± 0.08	100.0	98.75 ± 0.36
Guaifenesin	10.0	98.34 ± 0.23	10.0	99.07 ± 0.21
	40.0	99.71 ± 0.59	40.0	99.39 ± 0.09
	90.0	99.23 ± 0.67	90.0	99.44 ± 0.15

^*Each result is the average of three separate determinations