A New Spectrophotometric Method for Determination of Selenium in Cosmetic and Pharmaceutical Preparations after Preconcentration with Cloud Point Extraction

Table 1

Analytical parameters for determination of the selenium dithizonate complex.

Parameters	Se(HDZ)4 complex
𝜆max (nm)	424
Beer’s law range (ng mL^−1)	5–100
Molar absorptivity (l mol^−1 cm^−1)	7.98×10^3
LOD (ng mL^−1)	4.4
LOQ (ng mL^−1)	14.65
RSD (%)^a	2.18
Linear regression equation (𝑦)^b
Slop (𝑏)	0.0095
Intercept (𝑎)	0.0133
Correlation coefficient (𝑟)	0.9981
𝑆𝑦/𝑥	0.0146
𝑆𝑎	0.0098
𝑆𝑏	0.00017

^a𝑛=6.
^b𝑦=𝑏𝑥+𝑎, where 𝑥 is the concentration in ng mL⁻¹; 𝑆_𝑎: standard deviation of intercept.
𝑆_𝑏: standard deviation of slop; 𝑆_𝑦/𝑥: standard deviation of residuals.