Spectrophotometric Determination of N-Acetyl-L-Cysteine and N-(2-Mercaptopropionyl)-Glycine in Pharmaceutical Preparations

Table 1

Spectral characteristics and analytical parameters of the method for NAC and MPG under optimum reaction conditions.

Analytical parameter	NAC	MPG
𝜆max (nm)	593	593
ε (M^−1 cm^−1)^(a)	2.2 × 10^4	2.2 × 10^4
Sandell's sensitivity (μg cm^−2)^(a)	7.5 × 10^−3	7.6 × 10^−3
𝑚 (slope) ± SD	2.14 × 10^4 ± 0.0077	2.15 × 10^4 ± 0.0074
𝑧 (intercept) ± SD	0.0025 ± 0.0026	0.0036 ± 0.0033
Linear regression coefficient (𝑅^2)	0.9999	0.9999
Beer's law range (μM)	1.0 to 100.0	1.0 to 100.0
Number of points/replicates	11/3	11/3
Detection limit (μM)^(b)	0.14	0.13
Quantitation limit (μM)^(c)	1.0	1.0

^(a)Average of eleven determinations.
^(b)Detection limit = 3 s_b/m (three standard deviations for a blank divided by the slope of the calibration curve).
^(c)Quantitation limit = at least 10 s_b/m (ten standard deviations for a blank divided by the slope of the calibration curve).