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

Abstract

The application belongs to the technical field of thiocyanate detection, and specifically relates to a method for detecting thiocyanate based on inherent internal standard surface-enhanced Raman scattering substrate, which comprises the following steps: S1. Preparing a thiocyanate standard curve: taking the thiocyanate concentration as the horizontal coordinate, and the ratio of the peak intensity at the characteristic peak of thiocyanate with different concentrations to the peak intensity at the internal standard peak of a bare silver SERS chip as the vertical coordinate to establish a linear regression equation, thereby obtaining the thiocyanate standard curve; S2. Detecting experimental precision; S3. Quantitatively detecting the thiocyanate content: detecting the SERS signals of the thiocyanate sample to be measured and the bare silver SERS chip, and comparing the SERS signals with the thiocyanate standard curve in step S1 to obtain the thiocyanate content to be measured. In the application, the inherent peak generated by the substrate silver oxide in the bare silver SERS chip is used as an internal standard reference, no additional internal standard substance is added, the substrate detection performance is not affected, the linear fitting of the standard curve equation is better, the influence of errors is greatly reduced, the quantification is more accurate, and the thiocyanate can be rapidly detected.

Description

Technical Field

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

[0002] Thiocyanates commonly include potassium thiocyanate and sodium thiocyanate. Current methods for detecting cyanides mainly include liquid chromatography, headspace gas chromatography, flow injection analysis, spectrophotometry, and ion chromatography. The drawbacks of mainstream detection 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. However, the external standard method, which uses absolute intensity to establish a curve equation, suffers from drawbacks: large deviations and inaccurate quantification. The addition of an internal standard can sacrifice the sensitivity of the enhanced substrate to some extent. Furthermore, traditional internal standard methods, which eliminate errors by introducing an internal standard, can interfere with the detection of the target analyte to some extent, leading to inaccurate quantification.

[0003] 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 peak generated by silver oxide on the substrate in this bare silver SERS chip as the intrinsic peak (1605 cm⁻¹). -1 This method uses an internal standard as a reference, without adding any additional internal standard, thus not affecting the substrate detection performance. The standard curve equation exhibits better linearity, significantly reducing the impact of errors and resulting in more accurate quantification. It enables rapid detection of thiocyanates. No reports on this method have been found to date.

[0004] 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

[0005] The purpose of this invention is to provide a method for detecting thiocyanates based on an intrinsic internal standard surface-enhanced Raman scattering substrate, so as to solve the problems existing in the prior art for the detection of thiocyanates.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A method for detecting thiocyanate based on an intrinsic internal standard surface-enhanced Raman scattering substrate, characterized by comprising the following steps:

[0008] S1. Prepare the thiocyanate standard curve

[0009] Multiple thiocyanate 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 thiocyanate concentration as the x-axis and the ratio of the peak intensity at the characteristic peak of different concentrations of thiocyanate to the peak intensity at the standard peak in the bare silver SERS chip as the y-axis, so as to obtain the thiocyanate standard curve.

[0010] S2. Precision of the detection experiment

[0011] 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.

[0012] S3. Quantitative determination of thiocyanate content

[0013] The thiocyanate sample solution to be tested is added dropwise to the bare silver SERS chip, and the SERS signals of the thiocyanate sample to be tested and the bare silver SERS chip are detected. The detected signals are compared with the thiocyanate standard curve in step S1 to obtain the thiocyanate content in the thiocyanate sample to be tested.

[0014] More specifically, in step S1, the peak intensity of the characteristic peak of thiocyanate is 2110±5 cm⁻¹. -1 The peak intensity at 1605 cm⁻¹; the peak intensity of the internal standard peak of the bare silver SERS chip in steps S1-S2 is the internal standard at 1605 cm⁻¹. -1 Peak strength at that location.

[0015] 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.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] (1) The surface enhancement substrate of the bare silver SERS chip of this invention is composed of silver nanoparticles attached to a silicon wafer and is fabricated using a variety of techniques such as atomic layer deposition and tilted growth. The substrate is a 0.5×0.5cm square solid substrate attached to a glass slide. When the analyte is adsorbed on the silver rods of the substrate, a local electromagnetic field enhancement effect is formed between the silver rods, which greatly enhances the Raman signal of the target molecule. Electromagnetic enhancement is the most important enhancement mechanism, which is 3-6 orders of magnitude higher than conventional Raman. In addition, the bare silver SERS chip of this invention has multiple impurity peaks. These impurity peaks do not interfere with or overlap with thiocyanate. The impurity peaks are stable, have minimal deviation, and good uniformity. They can be used as internal standard peaks for reference.

[0018] (2) The linear R curve equation obtained by this invention 2Both methods achieve a value above 0.995, significantly improving the accuracy of quantification. Existing enhanced Raman internal standard methods either add internal standards to the detection solution or attach probe molecules as substrate internal standards. However, methods that add additional internal standards tend to interfere with the detection of the analyte or the enhanced substrate to some extent. In contrast, this invention does not require the addition of internal standards or probe molecules. It relies solely on the peaks generated by the chip substrate itself as reference internal standards, eliminating interference from internal standards and resulting in more accurate detection results.

[0019] (3) The internal standard method for quantitative detection of thiocyanate in this invention uses the chip-specific internal standard peak at 1605 cm⁻¹. -1 The peaks are far from the characteristic peaks of thiocyanate, with no overlap and no interference, making them effective as internal standards. Furthermore, the enhanced substrate exhibits excellent uniformity and stability, resulting in very good reproducibility of both the internal standard peak and the characteristic peaks of the detected target analyte. A relative standard deviation of less than 5% provides a solid foundation for accurate quantification, which is one of its advantages over other enhanced Raman substrates.

[0020] (4) Most existing enhanced Raman detection methods use silver sol or gold sol to enhance the substrate. The sol substrate needs to be prepared and used immediately, which is not conducive to carrying and has a short shelf life, making it unsuitable for long-term storage. However, the bare silver SERS chip used in this invention has a long shelf life, up to 3 months under sealed conditions, which is significantly different from other enhanced Raman substrates and is of great significance for rapid qualitative and quantitative detection of thiocyanate. Attached Figure Description

[0021] Figure 1 A schematic diagram illustrating the operation of detecting thiocyanate using a bare silver SERS chip;

[0022] Figure 2 For thiocyanate-enhanced Raman spectra;

[0023] Figure 3 The equation for the curve is established based on the intensity ratio and concentration;

[0024] Figure 4 The equation for the curve is established based on absolute intensity and concentration;

[0025] Figure 5 Raman spectra of 25 points on a blank substrate of a bare silver SERS chip;

[0026] Figure 6 Raman spectra were used for quantitative detection of thiocyanate at concentrations of 1 μg / mL and 15 μg / mL. Detailed Implementation

[0027] 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.

[0028] Example

[0029] A method for detecting thiocyanate based on an intrinsic internal standard surface-enhanced Raman scattering substrate includes the following steps:

[0030] S1. Prepare the thiocyanate standard curve

[0031] Sodium thiocyanate standard solution of 10 μg / mL was prepared into solutions of 0.25 μg / mL, 0.50 μg / mL, 0.75 μg / mL, 1.00 μg / mL, and 5.00 μg / mL using deionized water. 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 .

[0032] As shown in Figure 2, there are two Raman characteristic peaks for thiocyanate, one at 440 cm⁻¹. -1 and 2110cm -1 The substrate itself has multiple peaks; this invention uses the peak with the highest intensity, 1605 cm⁻¹. -1 The peak is used as an internal standard peak.

[0033] The characteristic peak of thiocyanate is 2113±5 cm. -1 The basis for the qualitative detection of thiocyanate is shown on the x-axis, with thiocyanate concentration as the horizontal axis. (Thiocyanate 2113±5cm) -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 thiocyanate. Additionally, thiocyanate 2113±5cm -1 A curve equation was established directly between peak intensity and concentration, and the results are shown in [the table]. Figure 4 .

[0034] Depend on Figure 3 It can be seen that, with 2110±5cm -1 Peak intensity and substrate self-calibration at 1605 cm⁻¹ -1 The linear determination coefficient of the intensity ratio curve equation for the peak-to-peak intensity ratio is 0.99617; (The rest of the text appears to be a fragment and requires further context for accurate translation.) Figure 4 It can be seen that, with 2110±5cm -1 The curve equation established by peak absolute intensity and concentration is as follows: Figure 3 As shown, the coefficient of determination is 0.97398. This demonstrates that the equation established using an internal standard reference significantly reduces bias, resulting in better linearity and facilitating quantitative analysis.

[0035] S2. Precision of the detection experiment

[0036] 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 .

[0037] Depend on Figure 5 It can be seen that the uniformity among different points on the reinforced substrate is good, and the peak intensities of the internal standard peaks on the substrate are not significantly different. Furthermore, calculations were performed at 25 points on the substrate at 1605 cm⁻¹. -1 The peak intensity at the point was calculated to be 4327, with a standard deviation of 136 and a relative standard deviation (RSD) of 3.15%. The high precision and small deviation reflect the high uniformity of the SERS chip and the stability of the instrument.

[0038] S3. Quantitative determination of thiocyanate content

[0039] 70 μL of sodium cyanide solutions with concentrations of 5 μg / mL and 10 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 resulting spectrum was used as the final result. Three parallel experiments were conducted for each concentration. The results are shown below. Figure 6 .

[0040] The characteristic peak of sodium cyanide is 2113±5 cm. -1 The peak intensity and the self-calibrated 1605 cm⁻¹ of the substrate -1 Substituting the peak intensity ratio into the standard curve equation in step S1, and after subtracting the baseline from the three sets of spectral data at 5 μg / mL, the characteristic peak of thiocyanate at 2110 cm⁻¹ was taken. -1 The peak intensity at 1605 cm⁻¹ is higher than that of the standard peak in the matrix. -1The peak intensities at the specified values ​​yielded intensity ratios of 8.87, 8.24, and 8.37, respectively. Substituting these values ​​into the standard curve equation in S1, the corresponding concentrations were calculated to be 5.10 μg / mL, 4.75 μg / mL, and 4.83 μg / mL, with a mean of 4.89 and a deviation of 2.1%. For the 10 μg / mL group, the calculated ratio intensities were 19.23, 16.92, and 18.25. Substituting these values ​​into the standard curve equation in S1, the corresponding concentrations were calculated to be 10.81 μg / mL, 9.54 μg / mL, and 10.26 μg / mL, with a mean of 10.2 and a deviation of 2%.

[0041] As can be seen above, using the internal standard peak as a reference significantly improves the linearity of the working curve, with very small quantitative deviation, closely approximating the true value. This was achieved using a bare silver SERS chip at 1605 cm⁻¹. -1 Using its own impurity peaks as internal standards for quantification can meet the requirements of Raman quantitative detection of thiocyanate.

[0042] 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 detecting thiocyanate based on an intrinsic internal standard surface-enhanced Raman scattering substrate, characterized in that, Includes the following steps: S1. Prepare a standard curve for thiocyanate. Multiple thiocyanate 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 thiocyanate concentration as the x-axis and the ratio of the peak intensity at the characteristic peak of different concentrations of thiocyanate to the peak intensity at the standard peak in the bare silver SERS chip as the y-axis, so as to obtain the thiocyanate standard curve. S2. Precision of the detection experiment 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. S3. Quantitative detection of thiocyanate content The thiocyanate sample solution to be tested is added dropwise to a bare silver SERS chip. The SERS signals of the thiocyanate sample and the bare silver SERS chip are detected. The detected signals are compared with the thiocyanate standard curve in step S1 to obtain the thiocyanate content in the thiocyanate sample. Step S1: The peak intensity of the characteristic peak of thiocyanate is 2110±5 cm⁻¹. -1 The peak intensity at 1605 cm⁻¹; the peak intensity of the internal standard peak of the bare silver SERS chip in steps S1-S2 is the internal standard at 1605 cm⁻¹. -1 Peak intensity at the point; In steps S1-3, the detection parameters are: 25 points are detected per bare silver SERS chip, laser wavelength 785, laser power 200mW, integration time 2000ms.

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