A method for detecting cyanide based on intrinsic internal standard surface-enhanced raman scattering substrate

Abstract

The application belongs to the technical field of cyanide detection, and specifically relates to a method for detecting cyanide based on inherent internal standard surface-enhanced Raman scattering substrates, which comprises the following steps: S1. Preparing a cyanide standard curve: taking the cyanide concentration as the horizontal coordinate, the ratio of the peak intensity at the characteristic peak of cyanide with different concentrations to the peak intensity at the internal standard peak of a bare silver SERS chip as the vertical coordinate, establishing a linear regression equation, and obtaining the cyanide standard curve; S2. Detecting experimental precision; S3. Quantitatively detecting the cyanide content: detecting the SERS signals of the cyanide sample to be measured and the bare silver SERS chip, comparing the SERS signals with the cyanide standard curve in step S1, and obtaining the cyanide content to be measured. The inherent peak of the bare silver SERS chip is used as an internal standard reference, the curve equation of the ratio intensity of the characteristic peak of the sample to be measured to the internal standard peak of the substrate and the concentration is established, the determination coefficient R 2 Better, eliminate the deviation caused by certain systematic errors, more accurate quantification, combined with the characteristics of rapid detection of Raman spectrum, the cyanide is rapidly detected.

Description

Technical Field

[0001] This invention belongs to the field of cyanide detection technology, specifically to a method for detecting cyanide based on an intrinsic internal standard surface-enhanced Raman scattering substrate. Background Technology

[0002] Cyanide is a highly toxic substance. Common cyanides include inorganic cyanides such as sodium cyanide, potassium cyanide, and hydrogen cyanide. Ingestion of hydrogen cyanide at a dose of 0.7-3.5 mg / kg can be fatal to humans, while sodium cyanide and potassium cyanide can cause death at a dose of 1-2 mg / kg. These substances pose a significant threat to human health, making rapid quantitative calculation of cyanide levels of practical significance.

[0003] Existing methods for detecting cyanide mainly include liquid chromatography, headspace gas chromatography, flow injection analysis, spectrophotometry, and ion chromatography. The drawbacks of these mainstream methods—expensive equipment, complex operation, and long processing times—need to be addressed. Surface-enhanced Raman spectroscopy (SERS) offers advantages such as high substrate sensitivity and rapid, efficient detection. Traditional quantitative methods are mainly divided into external standard methods and internal standard methods. External standard methods, which generally use absolute intensity to establish the curve equation, have large deviations and inaccurate quantification. Traditional internal standard methods are difficult to select, have a certain impact on substrate sensitivity, and are rarely suitable as internal standards for most substances. Furthermore, the introduction of internal standards can lead to competitive adsorption between the internal standard and the target analyte on the enhanced substrate.

[0004] To address the aforementioned issues, the inventors adopted a stable and commercially available bare silver SERS chip produced by Sanhuan High-Tech Raman Chip Technology Co., Ltd. (manufacturing process reference CN114544585A), using the inherent peak (1605 cm⁻¹) of this bare silver SERS chip. -1 As an internal standard reference, the system contains its own internal standard, eliminating the need to find and add an internal standard. The coefficient of determination R is determined by establishing a curve equation based on the ratio of the characteristic peak of the analyte to the peak intensity and concentration of the base internal standard. 2 Better yet, it eliminates biases caused by certain systematic errors, resulting in more accurate quantification, and combines the rapid detection capabilities of Raman spectroscopy for the rapid detection of cyanide. No reports on this aspect have been found yet.

[0005] The information disclosed in this background section is intended only to enhance the understanding of the overall background of the invention and should not be construed as an admission or in any way implying that the information constitutes prior art known to those skilled in the art. Summary of the Invention

[0006] The purpose of this invention is to provide a method for detecting cyanide based on an intrinsic internal standard surface-enhanced Raman scattering substrate, so as to solve the problems existing in the prior art for cyanide detection.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] A method for detecting cyanide based on an intrinsic internal standard surface-enhanced Raman scattering substrate includes the following steps:

[0009] S1. Prepare the cyanide standard curve

[0010] Multiple cyanide standard solutions of different concentrations were added to a bare silver SERS chip and SERS detection was performed. A linear regression equation was established with cyanide concentration as the x-axis and the ratio of the peak intensity at the characteristic peak of different concentrations of cyanide to the peak intensity at the standard peak in the bare silver SERS chip as the y-axis, so as to obtain the cyanide standard curve.

[0011] S2. Precision of the detection experiment

[0012] The peak intensities at multiple points on the blank substrate of the bare silver SERS chip were detected, and the peak intensity Raman spectrum of the blank substrate of the bare silver SERS chip was plotted. The peak intensities at the internal peaks of multiple points on the bare silver SERS chip were compared, and their mean, standard deviation and relative standard deviation were calculated.

[0013] S3. Quantitative detection of cyanide content

[0014] The cyanide sample solution to be tested is added dropwise to the bare silver SERS chip, and the SERS signals of the cyanide sample to be tested and the bare silver SERS chip are detected. The detected signals are compared with the cyanide standard curve in step S1 to obtain the cyanide content in the cyanide sample to be tested.

[0015] More specifically, in step S1, the peak intensity of the cyanide characteristic peak is 2139±5 cm⁻¹. -1 The peak intensity; in steps S1-S2, the peak intensity of the bare silver SERS chip internal standard is the peak intensity of the internal standard at 1605 cm⁻¹. -1 Peak strength.

[0016] More specifically, in steps S1-3, the detection parameters are: 25 points are detected per bare silver SERS chip, laser wavelength is 785 nm, laser power is 200 mW, and integration time is 2000 ms.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] (1) The present invention uses pure silver to enhance the substrate. The bare silver chip itself has multiple peaks. These peaks are generated after silver combines with oxygen. When the silver of the enhanced substrate comes into contact with the target analyte, the chemical environment will change and the oxygen adsorbed by the silver will disappear. This accurately reflects the change in the chemical environment of the substrate and is very suitable as an internal standard peak. This is something that other Raman enhanced substrates do not have.

[0019] (2) This invention uses the self-calibrated intrinsic peak as an internal standard peak for reference. The peak intensity of the detected cyanide characteristic peak is compared with the peak intensity of the self-base peak, and a standard curve equation is established with the concentration. The concentration and peak intensity ratio show a good linear correlation, which can greatly eliminate the deviation and is more conducive to quantitative analysis.

[0020] (3) Traditional internal standard methods require finding suitable internal standards, which must meet various conditions such as not interfering with the detection of the target analyte. These methods are difficult to find and unsuitable for the detection of most substances. Existing enhanced Raman spectroscopy methods mostly use liquid-enhanced gold-silver sol substrates, and most employ the method of adding internal standards. This method, to some extent, occupies the substrate SERS hotspot. A few methods use the substrate peak in the Raman quiescent region as the internal standard, but this requires additional assembly of signal molecules in the quiescent region, which is different from the internal standard peak of this invention. This invention utilizes the 1605 cm⁻¹ peak unique to bare silver SERS chips. -1 The peak at the specified location is used as an internal standard peak. Since it is not in the Raman quiescent region, there is no need to add additional internal standards or assemble probe molecules in the quiescent region as internal standards. This results in small deviation and high accuracy, solving the problem of difficult quantitative detection of cyanide using solid-state enhanced Raman substrates. Compared with existing Raman techniques, the solid-state enhanced Raman substrate of this invention exhibits high uniformity, good reproducibility, and extremely small deviation, with a relative standard deviation of approximately 5%.

[0021] (4) The bare silver SERS chip used in this invention has a long shelf life of up to 3 months under sealed conditions, which is significantly different from other enhanced Raman substrates. Other enhanced Raman substrates, especially gold or silver sols, are prone to aging and need to be prepared and used immediately. The bare silver SERS chip used in this invention can be used for rapid detection without the need to make an additional enhanced substrate. The detection results can be obtained in just 5 minutes, which is of great significance for rapid qualitative and quantitative detection of cyanide. Attached Figure Description

[0022] Figure 1 This is a schematic diagram illustrating the operation of detecting cyanide using a bare silver SERS chip.

[0023] Figure 2 A cyanide-enhanced Raman spectrum;

[0024] Figure 3 The equation for the curve is established based on the intensity ratio and concentration;

[0025] Figure 4 The equation for the curve is established based on absolute intensity and concentration;

[0026] Figure 5 Raman spectra of 25 points on a blank substrate of a bare silver SERS chip;

[0027] Figure 6 Raman spectra were used for quantitative detection of cyanide at concentrations of 1 μg / mL and 15 μg / mL. Detailed Implementation

[0028] The technical solution of this invention patent will be clearly and completely described below. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this invention.

[0029] Example

[0030] A method for detecting cyanide based on an intrinsic internal standard surface-enhanced Raman scattering substrate includes the following steps:

[0031] S1. Prepare the cyanide standard curve

[0032] Sodium cyanide standard solution of 100 μg / mL was used to prepare sodium cyanide solutions of 0.25 μg / mL, 0.50 μg / mL, 0.75 μg / mL, 1.00 μg / mL, and 5.00 μg / mL, respectively, using 0.01 mol / L sodium hydroxide solution as the solvent. 70 μL of each solution was added dropwise to the surface of a bare silver SERS chip. After 5 minutes, the surface of the bare silver SERS chip was dried with a bulb syringe. The chip was then tested using the following parameters: laser wavelength 785 nm, laser power 200 mW, integration time 2000 ms. 25 points were measured on each chip, and the average value of the resulting spectrum was taken as the final result. The operation demonstration is as follows: Figure 1 As shown, the results are as follows Figure 2 .

[0033] As shown in Figure 2, cyanide exhibits only one Raman characteristic peak at 2139 cm⁻¹. -1 The base itself contains multiple peaks, including one at 853 cm⁻¹. -1 1605cm -1 and 1605cm -1 Any location is acceptable; this invention uses the highest strength 1605cm. -1 The peak is used as an internal standard peak.

[0034] The characteristic peak of cyanide is 2139±5 cm. -1 The basis for the qualitative detection of cyanide is shown on the x-axis, with cyanide concentration at 2139±5 cm⁻¹. -1 Peak intensity and base 1605cm -1 A linear regression equation was established using the peak intensity ratio as the ordinate, and the results are shown in [the table]. Figure 3 This equation serves as the standard curve equation for the quantitative analysis of cyanide. Additionally, cyanide concentration is calculated at 2139±5 cm⁻¹. -1 A curve equation was established directly between peak intensity and concentration, and the results are shown in [the table]. Figure 4 .

[0035] Depend on Figure 3We know that the equation of the curve is Y = 0.0996X - 0.0565, R 2 =0.996. Figure 3 and Figure 4 By comparing the equations in the two systems, it is clear that the curve equation established based on absolute intensity and concentration has a generally poor linearity and large data fluctuations. In contrast, the equation established using an internal standard reference can greatly eliminate the bias, making the equation more linear and more conducive to quantification.

[0036] S2. Precision of the detection experiment

[0037] The intensity of 25 peak points on a bare silver SERS chip blank substrate was measured using a laser wavelength of 785 nm, a laser power of 200 mW, and an integration time of 2000 ms. The mean, standard deviation, and relative standard deviation were calculated, and the results are shown below. Figure 5 .

[0038] Depend on Figure 5 It can be seen that the uniformity between different points on the reinforced substrate is good, and the self-calibrated internal standard peak is 1605 cm⁻¹. -1 The peak intensity remained highly consistent at this location. Additionally, the calculations were performed at 25 points on the substrate at 1605 cm⁻¹. -1 The peak intensity at the point was calculated to be 2528.90, with a standard deviation of 112.10 and a relative standard deviation (RSD) of 4.43%, indicating that the SERS chip has extremely small deviation, laying a stable foundation for quantitative calculation.

[0039] S3. Quantitative detection of cyanide content

[0040] 70 μL of sodium cyanide solutions with concentrations of 1 μg / mL and 15 μg / mL were respectively added to the surface of a bare silver SERS chip. After 5 min, the surface of the bare silver SERS chip was dried with a syringe rubber bulb, and then tested using the following parameters: laser wavelength 785 nm, laser power 200 mW, integration time 2000 ms. 25 points were measured on each chip, and the average value of the spectral data was taken as the final result. Three parallel experiments were conducted for each concentration. The results are shown below. Figure 6 .

[0041] After baseline subtraction, the characteristic peak of sodium cyanide was found at 2139±5 cm⁻¹. -1 The peak intensities are respectively compared with the 1605 cm⁻¹ self-calibrated value of the substrate. -1Substituting the peak intensities into the standard curve equation in step S1, the calculated ratios of the three groups at 1 μg / mL were 0.042, 0.046, and 0.045, corresponding to concentrations of 0.989 μg / mL, 1.031 μg / mL, and 1.019 μg / mL, with a mean of 1.013 and a deviation of 1.3%. The ratios of the three groups at 15 μg / mL were 1.483, 1.409, and 1.512, and substituting these into the curve equation yielded corresponding concentrations of 15.452 μg / mL, 14.713 μg / mL, and 15.749 μg / mL, with a mean of 15.305 and a deviation of 2.03%.

[0042] As can be seen from the above, the six concentration groups were detected using an enhanced substrate. Quantification was performed by constructing a ratio-intensity curve equation using the substrate's inherent peak as an internal standard reference. The obtained detected values ​​were very close to the true values ​​with minimal deviation, further improving the quantitative method for solid-state enhanced Raman spectroscopy, especially with a 1605 cm⁻¹ substrate. -1 Using the peak intensity at a certain point as an internal standard is of positive significance for the quantitative detection of cyanide.

[0043] The foregoing description of specific exemplary embodiments of the invention is for illustrative and explanatory purposes. These descriptions are not intended to limit the invention to the precise forms disclosed, and it will be apparent that many changes and variations can be made in accordance with the foregoing teachings. The exemplary embodiments were chosen and described in order to explain the specific principles of the invention and its practical application, thereby enabling those skilled in the art to implement and utilize various different exemplary embodiments of the invention, as well as various different choices and variations. The scope of the invention is intended to be defined by the claims and their equivalents.

Claims

1. A method for the detection of cyanide based on intrinsic internal standard surface enhanced Raman scattering substrates, characterized in that, Comprise the following steps: S1. Making cyanide standard curve A plurality of different concentrations of cyanide standard solution is respectively added to the bare silver SERS chip, and SERS detection is carried out respectively, the concentration of cyanide is taken as the abscissa, and the ratio of the peak intensity at the characteristic peak of different concentrations of cyanide to the peak intensity at the internal standard peak of the bare silver SERS chip is taken as the ordinate to establish a linear regression equation, and a cyanide standard curve is obtained; S2. Detection of experimental precision The peak intensity of the blank substrate peak of the bare silver SERS chip is detected, the Raman spectrum of the peak intensity of the blank substrate peak of the bare silver SERS chip is drawn, the peak intensity of the internal standard peak of the bare silver SERS chip is compared, and the mean value, standard deviation and relative standard deviation are calculated; S3. Quantitative detection of cyanide content The cyanide sample solution to be detected is added to the bare silver SERS chip, the SERS signals of the cyanide sample to be detected and the bare silver SERS chip are detected, the signals obtained are compared with the cyanide standard curve in step S1, and the cyanide content in the cyanide sample to be detected is obtained; Wherein, the cyanide characteristic peak peak intensity in step S1 is the peak intensity of cyanide at 2139±5 cm -1 -1; the internal standard peak peak intensity in the bare silver SERS chip in steps S1-S2 is the peak intensity of the internal standard at 1605 cm -1 -1. In steps S1-3, the detection parameters are: 25 points per bare silver SERS chip, laser wavelength 785, laser power 200 mW, integration time 2000 ms.

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