CN107589098B - A method for fluorescent detection of trace uranyl ions - Google Patents

Abstract

The invention relates to a method for fluorescence detection of trace uranyl ions, which comprises the following steps: (a) adding escin and mesoporous molecular sieves to an aqueous solution containing uranyl ions, performing fluorescence detection to obtain the fluorescence of the aqueous solution Intensity; (b) Prepare a solution that does not contain uranyl ions, and measure its fluorescence intensity as F ₀ ; (c) Prepare solutions containing different concentrations of uranyl ions, and measure the fluorescence intensity as F _n ; (d) Measure the fluorescence intensity as F ₀ /F _n ‑1 is the ordinate, and the concentration of uranyl ions is the abscissa to draw the curve; (e) the aqueous solution described in step (a) is diluted in proportion until the fluorescence intensity measured by it is based on that in step (d) The concentration corresponding to the curve falls within the range of 0.001-0.05 μmol/L; it can be multiplied by the corresponding concentration according to the multiple of dilution. This enables precise determination of the concentration of uranyl ions in aqueous solution with a detection limit as low as 6nM.

Description

A method for fluorescent detection of trace uranyl ions

technical field

The invention relates to the field of radioactive substance detection, in particular to a method for fluorescence detection of trace uranyl ions.

Background technique

With the depletion of traditional non-renewable energy such as coal and oil, clean energy represented by nuclear energy is becoming more and more popular and used more and more worldwide. One of the main raw materials of nuclear energy is uranium, so the probability of human beings being exposed to the threat of uranium is increasing. The threat of uranium comes from its own radioactive toxicity and chemical toxicity. Once it touches or enters the human body, it will cause serious damage to human organs and bodies. High doses of uranium are also harmful to the environment. Under aerobic or hypoxic conditions, the most stable form of uranium in aqueous solution is uranyl ion UO ₂ ²⁺ , which has certain solubility in water, so it can migrate freely in the environment. Therefore, the detection and monitoring of uranyl has certain strategic significance and is very necessary.

Prior to this, there were many reports on uranyl ion monitoring. Some of these methods are based on complex or expensive instruments. The cost of using these methods is usually relatively high, and the requirements for sample preparation and instrument operation are relatively strict. These characteristics make on-site monitoring difficult to achieve, so these methods are destined not to be accepted by the general public. On the other hand, the materials of the probe itself have also been developed, and some new nanomaterials and media have been reported. Recently, Chen et al. reported the mesoporous silicon/carbon dot composite CDs/SBA-NH ₂ material, which can not only adsorb uranyl ions, but also monitor the adsorption process (Z.Wang, C.Xu, Y.Lu , F. Wu, G. Ye, G. Wei, T. Sun and J. Chen, ACS Appl. Mater. Interfaces, 2017, 9, 7392.). Lu Yi's team at the University of Illinois reported in 2007 an in vitro screened DNA enzyme that specifically coordinates uranyl ions, which has almost perfect detection results for uranyl ions, with a detection limit of 45pM. Also reported the first case of intracellular uranyl ion detection (J. Liu, AKBrown, X. Meng, DMCropek, JDI Stok, DB Watson and Y. Lu, Proc. Natl. Acad. Sci. USA, 2007, 104, 2056; P. Wu, K. Hwang, T. Lan and Y. Lu, J. Am. Chem. Soc., 2013, 135, 5254.). DNase has a promising application prospect in the field of metal ion detection, so it has received extensive attention, and it has also been used in various techniques to detect trace amounts of uranyl ions. However, the screening process for this metal ion-specific DNase is complex and time-consuming, so this method is inconvenient and not economical.

Among the different technical approaches, fluorescence is clearly a powerful, cost-effective, and easy-to-operate tool. However, there are not many reports on the detection of uranyl ions using fluorescence, and even fewer using fluorescent small molecules, which is quite different from the situation of other metal ions. The reason for this may be that it is difficult to achieve satisfactory detection limits using fluorescent small molecule detection. The limit of detection is one of the main obstacles in the detection of trace amounts of uranyl ions by fluorescence techniques. Therefore, how to improve the sensitivity of the probe is a very important link. At present, there are few reports on improving the sensitivity of probes.

Contents of the invention

The purpose of the present invention is to provide a method for fluorescence detection of trace uranyl ions in order to overcome the deficiencies of the prior art.

In order to achieve the above object, the technical solution adopted in the present invention is: a method for fluorescence detection of trace uranyl ions, which comprises the following steps:

(a) adding escin and mesoporous molecular sieve to the aqueous solution containing uranyl ions, and performing fluorescence detection to obtain the fluorescence intensity of the aqueous solution; the ratio of the escin and the mesoporous molecular sieve is 5-15 μmol/L : 0.05～0.2mg/mL;

(b) Prepare a solution that does not contain uranyl ions, and measure its fluorescence intensity as F ₀ ; the solution that does not contain uranyl ions contains aescin and mesoporous molecular sieves at the same concentration as in step (a);

(c) preparing solutions containing different concentrations of uranyl ions, and the measured fluorescence intensity is _Fn ; the solutions containing different concentrations of uranyl ions contain the same concentration of escin and mesoporous molecular sieves as in step (a);

(d) draw a curve with F ₀ /F _n -1 as the ordinate and the concentration of uranyl ions as the abscissa;

(e) Dilute the aqueous solution described in step (a) in proportion until the measured fluorescence intensity falls within the range of 0.001 to 0.05 μmol/L according to the concentration corresponding to the curve described in step (d); according to the diluted The multiple can be multiplied by the corresponding concentration.

Optimally, the ratio of the escin and the mesoporous molecular sieve is 10 μmol/L:0.1 mg/mL.

Optimally, the mesoporous molecular sieve is SBA-15, SBA-1 or MCM-48.

Optimally, in step (b) and step (c), the solvents used in the solution not containing uranyl ions and the solutions containing uranyl ions in different concentrations are all mixed with methanol and water at a volume ratio of 1:1. to make.

Due to the application of the above-mentioned technical scheme, the present invention has the following advantages compared with the prior art: the present invention detects the fluorescence of trace uranyl ions by measuring the concentration of solutions with different concentrations of uranyl ions and solutions that do not contain uranyl ions. Fluorescence intensity, and draw a standard curve; if necessary, the aqueous solution to be tested can be diluted until the corresponding concentration falls within the range of 0.001-0.05μmol/L, and the concentration can be multiplied by the dilution multiple, so that the uranium in the aqueous solution can be accurately determined For the concentration of acyl ions, the detection limit can be as low as 6nM.

Description of drawings

Fig. 1 is the standard curve drawn in the present invention to trace uranyl ion fluorescence detection method;

Fig. 2 is the low concentration standard curve drawn in the present invention to trace uranyl ion fluorescence detection method;

Fig. 3 is a schematic diagram of the present invention's fluorescence detection method for trace uranyl ions.

Detailed ways

The present invention will be further described below in conjunction with examples.

The method for fluorescent detection of trace uranyl ions of the present invention comprises the following steps:

(a) Add esculin and mesoporous molecular sieves (usually SBA-15, but other types of products, such as SBA-1 or MCM-48, etc.) to the aqueous solution containing uranyl ions for fluorescence detection Obtain the fluorescence intensity of the aqueous solution at a wavelength of 455nm; the ratio of aescin and the mesoporous molecular sieve is 5-15 μmol/L: 0.05-0.2 mg/mL; when the ratio of aescin and the mesoporous molecular sieve is 10 μmol/L respectively When L and 0.1mg/mL, the fluorescence detection effect is the best, and the detection limit is as low as 6nM (ie 6nmol/L; the same below);

(b) prepare a solution (blank sample) that does not contain uranyl ions, and measure its fluorescence intensity as F ₀ ; the solution that does not contain uranyl ions contains escin and mesoporous molecular sieves at the same concentration as in step (a) , and their specific ratios are: 5-15 μmol/L: 0.05-0.2 mg/mL;

(c) Prepare solutions containing different concentrations of uranyl ions (specifically 0.001, 0.002, 0.005, 0.01, 0.02, 0.03, 0.04, 0.05, 0.1, 0.2, 0.5, 1, 2, 3, 4, 5, 6, 7 _{. _ _ _ _ _ _ _ _ _ _} F ₁₁ , F ₁₂ , F ₁₃ , F ₁₄ , F ₁₅ , F ₁₆ , F ₁₇ , F ₁₈ , F ₁₉ , F ₂₀ and F ₂₁ ); solutions containing different concentrations of uranyl ions contained the same concentration of escin and mesoporous molecular sieve; the solvent in step (b) and step (c) is usually mixed with methanol and water in a volume ratio of 1:1;

(d) Draw a curve with F ₀ /F _n -1 as the ordinate and the concentration of uranyl ions as the abscissa (the above 22 data points are drawn as a standard curve, as shown in Figure 1); it can be found that when uranyl ions When the concentration is within 0.05μmol/L (that is, when the concentration is 0.001～0.05μmol/L), the standard difference is basically a straight line; the curve at this time (as shown in Figure 2) can be expressed as F ₀ /F _n - 1 = K _SV [Q], K _SV is Stern – coefficient (K _SV is 8.69×10 ⁶ mol ^-1 ·L, R ² =0.994), Q is the concentration of uranyl ions;

(e) Substituting the fluorescence intensity measured in step (a) into the curve in step (d) first, and preliminarily judging the concentration of the aqueous solution in step (a); if the concentration of the aqueous solution is greater than 0.05 μmol/L at this time, step The aqueous solution in (a) is diluted proportionally until the measured fluorescence intensity falls within the range of 0.001 to 0.05 μmol/L according to the concentration corresponding to the curve in step (d); then multiplied by the corresponding concentration according to the multiple of dilution That's it. As shown in Figure 3, this is because SBA-15 has a certain adsorption effect on escin, and a local high-concentration area is formed around SBA-15; however, when uranyl ions are added, the fluorescence intensity decreases more than that in the blank is still high, so the corresponding F ₀ /F-1 value is higher, which can easily distinguish uranyl ions from other ions; Has very good selectivity. The detection performance of fluorescent small molecules for uranyl ions (in terms of sensitivity and selectivity) has been greatly improved in the presence of SBA-15; It has a certain adsorption effect. When SBA-15 exists, aescin and uranyl ions are partially adsorbed to the surface of SBA-15, so from a microscopic point of view, the concentration of uranyl ions around SBA-15 increases; therefore its The detection effect has improved. More importantly, uranyl ions and aescin may have a certain complexation effect, and the presence of escin has a certain auxiliary effect on the adsorption of uranyl ions.

Two samples as shown in Table 1 were selected for detection, and the results are listed in Table 1. It can be seen that the error rate measured by this method is very small, less than 5%.

Table 1 Test data table of actual samples

The above-mentioned embodiments are only to illustrate the technical concept and characteristics of the present invention. Equivalent changes or modifications made in the spirit shall fall within the protection scope of the present invention.

Claims (4)

1. a method for fluorescence detection of trace uranyl ions is characterized by comprising the following steps:

(a) Adding esculin and a mesoporous molecular sieve into a water solution containing uranyl ions, and performing fluorescence detection to obtain the fluorescence intensity of the water solution; the ratio of esculin to the mesoporous molecular sieve is 5-15 mu mol/L: 0.05-0.2 mg/mL;

(b) Preparing a solution without uranyl ions, and measuring the fluorescence intensity of the solution to be F0; the solution which does not contain uranyl ions contains esculin and a mesoporous molecular sieve with the same concentration as that in the step (a);

(c) Preparing solutions containing uranyl ions with different concentrations, and measuring the fluorescence intensity to be Fn; said solutions containing different concentrations of uranyl ions contain the same concentrations of esculin and mesoporous molecular sieve as in step (a);

(d) F0/Fn-1 is used as an ordinate, and the concentration of uranyl ions is used as an abscissa to draw a curve;

(e) Diluting the aqueous solution in the step (a) in proportion until the measured fluorescence intensity falls in the range of 0.001-0.05 [ mu ] mol/L according to the concentration corresponding to the curve in the step (d); multiplying the corresponding concentration by the dilution factor.

2. The method for fluorescence detection of trace uranyl ions according to claim 1, wherein: the ratio of the esculin to the mesoporous molecular sieve is 10 mu mol/L: 0.1 mg/mL.

3. The method for fluorescence detection of trace uranyl ions according to claim 1, wherein: the mesoporous molecular sieve is SBA-15, SBA-1 or MCM-48.

4. the method for fluorescence detection of trace uranyl ions according to claim 1, wherein: in the step (b) and the step (c), the solution not containing the uranyl ions and the solution containing the uranyl ions with different concentrations are prepared by mixing methanol and water in a volume ratio of 1: 1.