双波长分光光度法测定大蒜中硒含量

Determination of Selenium Content in Garlicby Dual-wavelength Spectrophotometry

在0.16mol/L硫酸中,硒(Ⅳ)与过量的碘化钾反应生成I3-,I3-进一步与番红花红T(ST)形成稳定的离子缔合物ST.I3,使ST褪色,405nm处出现正吸收峰,521nm处出现负吸收峰。选定测量波长为405nm,参比波长为521nm,建立了双波长分光光度法测定硒的新方法。硒(Ⅳ)浓度在0～0.6μg/mL范围内服从比尔定律,表观摩尔吸光系数ε为1.05×105 L/mol.cm,检出限为1.42μg/L。方法用于测定大蒜中硒,结果与荧光法一致。相对标准偏差0.6%～1.0%(n=5),平均回收率为97.4%～98.6%。

A new method for determination of selenium was developed by dual-wavelength spectropho- tometry using 405 nm as the measurement wavelength and 521 nm as the reference wavelength. The method is based on the reaction of Se（1V） with excess potassium iodide in 0.16 mol/L HzSO4 to produce I3^-, and it further reacts with safranine T （ST） to form a stable ion-association complex ST · I3, which leads to the fading of ST. As a result, there were a positive absorption peak at 405 nm and a negative absorption peak at 521 nm. Beer＇s law was obeyed in the range of 0-0.6μg/mL for Se（IV）. The apparent molar absorption coefficient was 1.05 × 10^5 L/mol · cm, and the limit of detection was 1.43μg/L. The method was applied to determine selenium in garlic. The results showed good agreement with those obtained by fluorimetric method. The relative standard deviation was 0.6 %-1.0 （n=5）, and the average recovery was 97.4%-98.6%.