Rf 5001 pc spectrofluorophotometer

The concentration of selenium was measured according to the Watkinson method, modified by Grzebuła and Witkowski (1977 ). The samples of liver (~ 1 g) and kidney (~ 0.5 g) were digested in HNO₃ at 230 °C for 180 min and in HClO₄ at 310 °C for 20 min. Then, 9% HCl was added to the mineralized samples to reduce selenates (Se VI) to selenites (Se IV). Selenium was derivatized with 2,3-diaminonaphthalene (DAN) under controlled pH (pH 1–2) until the formation of selenodiazole complex. This complex was extracted into cyclohexane. Se concentration was determined fluorometrically using a Shimadzu RF-5001 PC spectrofluorophotometer. Fluorescence was measured using an emission wavelength of 518 nm and an excitation wavelength of 378 nm. Concentration of selenium was calculated into 1 g of wet and dry matter. Dry matter was measured for each sample.
The accuracy of the analytical procedure was verified by measuring the level of selenium in a reference material: NCS ZC 71001 (Beef Liver) (China National Analysis Center for Iron and Steel Beijing China). Mean recovery was 91.1% of the reference value.

Selenium concentrations were determined using the spectrofluorometric method [28 (link)]. The samples (0.5–1.5 g) were digested in HNO₃ at 230 °C for 180 min and in HClO₄ at 310 °C for 20 min. Then 3 ml 9 % HCl was added to reduce Se⁶⁺ to Se⁴⁺. Selenium was derivatized with 2,3-diaminonaphthalene (Sigma-Aldrich), under controlled pH conditions (pH 1–2), with the formation of selenodiazole complex. This complex was extracted into cyclohexane. EDTA and hydroxylamine hydrochlorine were used as masking agents. Se concentration was determined fluorometrically using a Shimadzu RF-5001 PC spectrofluorophotometer and expressed in mg kg⁻¹ of wet weight. The excitation wavelength was 376 nm, and the fluorescence emission wavelength was 518 nm. All chemicals used were of analytical reagent grade. The accuracy of the method was verified using the certified reference material BCR-185R (bovine liver) with Se concentration 1.68 mg kg⁻¹ ww. A reference sample was analyzed in triplicate. The mean Se concentration was 95.8 ± 3.3 % of the reference values. The detection limit was 0.004 mg kg⁻¹ wet weight.