Abstract: Selenium is widely found in marine organisms, water, food, and animal feed, and there are numerous methods for determining its concentration. Among these, fluorescence spectrophotometry is an effective method for the qualitative and quantitative analysis of fluorescent substances, and it is a commonly used technique for determining selenium concentration.
Taking the determination of selenium content in marine organisms as an example, this paper describes the use of a Gangdong F-380 fluorescence spectrophotometer to measure selenium content in accordance with GB 17378.6-2007 “Marine Monitoring Specifications: Part 6—Analysis of Organisms,” Section 12.1 “Selenium: Fluorescence Spectrophotometric Method (Arbitration Method).” The results demonstrate that this method is simple to operate and exhibits good linearity, making it an ideal method for determining selenium content.
Keywords: Fluorescence spectrophotometry, Selenium, Marine organisms, Water, Food, Feed
Principle
After digestion of biological samples with sulfuric acid–perchloric acid–sodium molybdate, tetravalent selenium reacts with 2,3-diaminonaphthalene (DAN) in an acidic medium to form 4,5-benzoxanthen, which emits green fluorescence. The sample is extracted with cyclohexane, and fluorescence spectrophotometric measurements are performed at an excitation wavelength of 376 nm, emission wavelength of 520 nm.
Experimental Conditions
Instruments and Accessories:
Tianjin Port East F-380 Fluorescence Spectrophotometer
Fluorescent quartz cuvettes
Analysis conditions:
Excitation wavelength: 376 nm
Emission wavelength: 520 nm
Medications:
Nitric acid (analytical grade), perchloric acid (analytical grade), hydrochloric acid (analytical grade), ammonia solution (analytical grade), methyl red solution, disodium ethylenediaminetetraacetate (EDTA-2Na), hydroxylamine hydrochloride, 2,3-diaminonaphthalene, selenium standard solution, etc.
Other:
Precision pH test strips, hot plates, analytical balances (0.0001 g), grinders, drying ovens, water baths, stoppered colorimetric tubes, separatory funnels, lens paper, volumetric flasks, conical flasks, pipettes, etc.
Sample and Reference Sample Preparation
1. Sample preparation
Dry the samples, grind them in an agate mortar, and sieve the entire mixture through a nylon sieve with a mesh size of 80–100 mesh (180 μm–154 μm).
2. Sample digestion
(1) Flowchart of the Sample Preparation Process
(2) Blank preparation solution
Prepare the blank solution by following the steps in the sample preparation flowchart above; that is, do not add the sample to be tested, but proceed directly to the “Add water to moisten” step.
(3) Samples and blank test solutions
3. Sample solution for the standard curve
Take six 250 mL conical flasks and add 0.00 mL, 1.00 mL, 2.00 mL, 3.00 mL, 4.00 mL, and 5.00 mL of selenium standard working solution (0.1 μg/mL) to each, respectively. Add approximately 10 mL of water to each and mix thoroughly. Digest the standards according to the sample digestion procedure, then prepare the test solution by preparing a selenium standard calibration solution.
Test results
Use the “Photometric Analysis” module of the Hongdong F-380 fluorescence spectrophotometer to establish a standard calibration curve for selenium and perform sample analysis.
Conclusion
Fluorescence spectrophotometry is an ideal method for determining selenium content, as it is simple to perform and highly accurate.
Because the selenium-containing sample solution is unstable when exposed to light, and background subtraction is required during the measurement process, the experiment places higher demands on the instrument’s capabilities. The Gangdong F-380 Fluorescence Spectrophotometer is the first to incorporate an excitation-side light-blocking shutter in its hardware design, thereby preventing direct exposure of the sample to intense light. On the software side, it features a unique dual-background subtraction function that automatically calculates selenium concentration, making the entire experimental procedure simple and ensuring excellent result reproducibility.
This information is subject to change without notice.
© Tianjin Gangdong Sci&Tech.Development Co., 2011
Printed in CHINA, September 1, 2011
Tianjin Port East Technology Co., Ltd.
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