ICP-MS (Inductively Coupled Plasma Mass Spectrometry) detection method for 39 trace metal elements in 1, 4-butanediol

Abstract

The invention discloses an ICP-MS (Inductively Coupled Plasma Mass Spectrometry) detection method for 39 trace metal elements in 1, 4-butanediol, and relates to the technical field of analysis and detection. When inductively coupled plasma mass spectrometry is adopted for detection, oxygen is added to reduce carbon deposition, flameout is avoided, the temperature of an atomizing chamber is set to be 2 DEG C so as to stabilize the sample introduction environment, 1, 4-butanediol is mixed with N-methyl pyrrolidone to be directly introduced according to the characteristics that 1, 4-butanediol is sticky and the freezing point is 20.1 DEG C, and pretreatment errors are reduced. Experimental results show that the adding standard recovery rate is 92.21%-105.96%, and the method is good in accuracy and has the advantages of being efficient, small in interference, little in pollution and high in sensitivity.

Description

Technical Field

[0001] The present invention relates to the technical field of analysis and detection, and in particular to an ICP-MS detection method for 39 trace metal elements in 1,4-butanediol. Background Art

[0002] 1,4-Butanediol (BDO), molecular formula is C4H 10 O2, with a molecular weight of 90.12, appears as a colorless or pale yellow viscous liquid with a freezing point of 20.1°C. BDO is an important raw material for fine chemicals, widely used in the pharmaceutical, chemical, textile, papermaking, automotive, and daily chemical industries. Its downstream products include γ-butyrolactone, tetrahydrofuran, polyurethane resins, and plasticizers. It is also used as a brightener in the solvent and electroplating industries.

[0003] As BDO applications continue to expand, the demand for accurate and efficient quantitative analysis of metal elements in its production process is increasing. Currently, the detection technologies for metal elements mainly include the following four categories: atomic absorption spectrometry (AAS), atomic fluorescence spectrometry (AFS), inductively coupled plasma optical emission spectrometry (ICP-OES), and inductively coupled plasma mass spectrometry (ICP-MS). Specifically:

[0004] (1) Atomic absorption spectrometry (AAS) uses light with a characteristic wavelength that matches the target element to cause electrons to transition from the ground state to a higher energy state. The absorbance is positively correlated with the concentration of the target element. However, this method has a limited scope of application. The light source lamp needs to be replaced when detecting different elements, and the sample pretreatment process is relatively cumbersome. The detection limit is usually around 10 -6 mg / L level.

[0005] (2) Atomic fluorescence spectrometry (AFS) is susceptible to fluorescence quenching and scattered light interference, and it is difficult to achieve simultaneous detection of multiple elements.

[0006] (3) Inductively coupled plasma optical emission spectrometry (ICP-OES) is considered to be an early technical version of ICP-MS. It has the ability to analyze multiple elements simultaneously and is particularly suitable for the determination of low-concentration metal elements.

[0007] (4) Inductively coupled plasma mass spectrometry (ICP-MS) is widely used for the quantitative analysis of metal elements in organic matter due to its high efficiency, high stability, and low chemical interference. With the deepening of scientific research and the development of analytical instrument technology, ICP-MS has become an important tool for determining the content of metal elements in many fields such as semiconductors, alloys, ores, water resources, food, daily chemical products, and pharmaceuticals.

[0008] Currently, the detection of metal elements in liquid organic matter typically involves removing organic matter through wet digestion, microwave digestion, or dilution, followed by ICP-MS analysis. However, reports on the determination of metal element content in BDO using ICP-MS are limited. Due to the low metal content in BDO, the complex sample digestion process, and the potential interference introduced by pure water dilution, these results can easily lead to significant errors.

[0009] In view of this, the present invention is proposed. Summary of the Invention

[0010] The purpose of the present invention is to provide an ICP-MS detection method for 39 trace metal elements in 1,4-butanediol to solve the problems existing in the above-mentioned prior art.

[0011] To achieve the above object, the present invention provides the following solutions:

[0012] The present invention provides an ICP-MS detection method for 39 trace metal elements in 1,4-butanediol, comprising the following steps:

[0013] (1) mixing 1,4-butanediol and N-methylpyrrolidone to obtain a sample to be tested;

[0014] (2) Prepare multi-element standard solutions with a concentration of 0.5-10 μg / L and draw a standard curve using the standard addition method;

[0015] (3) The sample to be tested was directly injected into the ICP-MS, wherein the temperature of the nebulizer chamber was 2°C and the auxiliary gas was an argon-oxygen mixture; the metal element content was calculated using the standard curve;

[0016] The multi-element standard solution includes 39 trace metal elements to be tested.

[0017] As a further preference of the present invention, the mass ratio of 1,4-butanediol to N-methylpyrrolidone is (0.8-1.6):1.

[0018] As a further preferred embodiment of the present invention, the volume fraction of oxygen in the argon-oxygen mixed gas accounts for 20%.

[0019] As a further preference of the present invention, the 39 trace metal elements include: lithium, beryllium, boron, sodium, magnesium, aluminum, potassium, calcium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, germanium, arsenic, rubidium, strontium, zirconium, niobium, rhodium, silver, palladium, cadmium, indium, tin, antimony, cesium, barium, tantalum, tungsten, platinum, gold, thallium, lead and bismuth.

[0020] As a further preferred embodiment of the present invention, the radio frequency power of the ICP-MS is 1550 W, the carrier gas argon flow rate is 0.5 L / min, the collision gas helium flow rate is 2 L / min, the sampling depth is 8 mm, and the sampling cone and the skimmer cone are made of platinum.

[0021] As a further preferred embodiment of the present invention, the detection is carried out in a Class 100 clean room.

[0022] BDO is a colorless, viscous, oily liquid with a freezing point of 20.1°C. Direct injection at low temperatures can easily cause BDO to solidify, leading to clogging of tubing and atomizers. The present invention uses N-methylpyrrolidone (NMP) to dilute BDO before injection. NMP has a freezing point of -24.4°C and is highly polar, making it completely miscible with BDO and effectively reducing its viscosity. A 1:1 mass ratio of BDO and NMP showed no solidification at 2°C, allowing for normal injection and analysis.

[0023] The present invention uses an organic solvent, N-methylpyrrolidone, to dilute a BDO sample, and directly injects the sample for detection and analysis through ICP-MS. This analysis method provides a scientific basis for the quality control and application of BDO.

[0024] The present invention discloses the following technical effects:

[0025] This study established a rapid method for the determination of 39 trace metal elements in 1,4-butanediol. Using inductively coupled plasma-mass spectrometry (ICP-MS), oxygen was added to reduce carbon deposition and prevent flameout. The atomization chamber temperature was set at 2°C to stabilize the sample injection environment. Furthermore, given the viscosity of 1,4-butanediol and its freezing point of 20.1°C, it was mixed with N-methylpyrrolidone and injected directly into the sample to reduce pretreatment errors. Experimental results showed spiked recoveries ranging from 92.21% to 105.96%, demonstrating good accuracy and the advantages of high efficiency, minimal interference, low contamination, and high sensitivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0027] Figure 1 This is the carbon deposition condition of the cone before and after oxygen addition in Example 1 of the present invention. DETAILED DESCRIPTION

[0028] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0029] It should be understood that the terms described herein are intended only to describe particular embodiments and are not intended to limit the present invention. In addition, for numerical ranges herein, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. The intermediate value within any stated value or stated range, and each smaller range between any other stated value or intermediate value within the stated range, is also encompassed within the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded within the scope.

[0030] Unless otherwise indicated, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of any conflict with any incorporated document, the contents of this specification shall prevail.

[0031] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments described herein without departing from the scope or spirit of the invention. Other embodiments will be apparent to those skilled in the art from the description of the invention. The description and examples are intended to be illustrative only.

[0032] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0033] One of the objects of the present invention is to provide an ICP-MS detection method for 39 trace metal elements in 1,4-butanediol, comprising the following steps:

[0034] (1) mixing 1,4-butanediol and N-methylpyrrolidone to obtain a sample to be tested;

[0035] (2) Prepare multi-element standard solutions with a concentration of 0.5-10 μg / L and draw a standard curve using the standard addition method;

[0036] (3) The sample to be tested was directly injected into the ICP-MS, wherein the temperature of the nebulizer chamber was 2°C and the auxiliary gas was an argon-oxygen mixture; the metal element content was calculated using the standard curve;

[0037] The multi-element standard solution includes 39 trace metal elements to be tested.

[0038] Furthermore, the mass ratio of the 1,4-butanediol to N-methylpyrrolidone is (0.8-1.6):1.

[0039] Furthermore, in the argon-oxygen mixed gas, the volume fraction of oxygen accounts for 20%.

[0040] Furthermore, the 39 trace metal elements include: lithium, beryllium, boron, sodium, magnesium, aluminum, potassium, calcium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, germanium, arsenic, rubidium, strontium, zirconium, niobium, rhodium, silver, palladium, cadmium, indium, tin, antimony, cesium, barium, tantalum, tungsten, platinum, gold, thallium, lead and bismuth.

[0041] Furthermore, the radio frequency power of the ICP-MS is 1550 W, the carrier gas argon flow rate is 0.5 L / min, the collision gas helium flow rate is 2 L / min, the sampling depth is 8 mm, and the sampling cone and the skimmer cone are made of platinum.

[0042] Furthermore, the detection is carried out in a Class 100 clean room.

[0043] The present invention will be further described in detail below with reference to the examples. It should be noted that the parts not described in detail in the present invention are conventional operating methods in the art and are not the focus of the present invention.

[0044] Example 1

[0045] 1. Instruments and Reagents

[0046] Inductively coupled plasma mass spectrometer 7800 (Agilent Technologies, USA); Water Maker Pro (Sartorius, Germany); Pipette E4XLS (Mettler Toledo, Switzerland); Pipette tip BioClean Ultra (Mettler Toledo, Switzerland); 1 / 100,000 electronic balance (Mettler Toledo, Switzerland); Reagent bottles (PFA material, Azovon, Japan);

[0047] Multi-element mixed standard solution 8500-6940 (10 μg / L, Agilent Technologies, USA); nitric acid (65%, Merck, Germany); argon (99.999%), helium (99.999%), and argon-oxygen mixture (20% O2, 80% Ar), all from Puyang Xinyuan Chemical Equipment Co., Ltd.; N-methylpyrrolidone (99.92%, Xinmaiqi Materials Co., Ltd.); and 1,4-butanediol (99.71%, Shaanxi Yanchang Petroleum Group).

[0048] 2. Testing environment

[0049] Because the test results are at the trace level, it is easy to cause contamination of certain metal elements in an ordinary environment. To avoid detection errors, the dilution of samples, preparation of standard solutions, and detection and analysis are all carried out in a Class 100 clean room, and nitrile gloves are worn.

[0050] 3. Oxygenation detection

[0051] When ICP-MS analyzes organic samples, the spray chamber is cooled to 2°C to reduce the entry of solvent vapor into the plasma, provide a stable environment for the aerosol, ensure the uniformity of the aerosol, improve the stability of the plasma and ionization efficiency, and improve the sensitivity and stability of the analysis results. During the detection process, it is necessary to add auxiliary gas argon-oxygen mixture to reduce carbon deposition in the cone hole and avoid flameout. The carbon deposition situation of the cone before and after oxygen addition is as follows Figure 1 shown.

[0052] 4. NMP dilution of BDO

[0053] BDO is a colorless, viscous, oily liquid with a freezing point of 20.1°C. Direct injection at low temperatures can easily cause BDO to solidify, leading to clogging of tubing and atomizers. The present invention uses N-methylpyrrolidone (NMP) to dilute BDO before injection. NMP has a freezing point of -24.4°C and is highly polar, making it completely miscible with BDO and effectively reducing its viscosity. A 1:1 mass ratio of BDO and NMP to each other showed no solidification at 2°C, allowing for normal injection and analysis.

[0054] If BDO is diluted with water, due to the presence of H2O in the sample being tested, a small amount of water may enter the plasma center during the aerosol formation process, causing interference with certain metal ions and causing simple chemical reactions, such as 35Cl and 16O = 51ClO (51ClO = 51V signal superposition). After water dilution, the detection value of alum is high, and the spiked recovery rate is about 690%, resulting in a detection error of alum (V). The results are shown in Table 1.

[0055] Table 1 Detection error of alum

[0056]

[0057] 5. Drawing of the standard curve

[0058] The standard addition method was used to add a multi-element mixed standard solution (including 39 trace metal elements to be measured) to a mixture of BDO and NMP (mass ratio 1:1) at concentrations of 0.5 μg / L, 1 μg / L, 5 μg / L, and 10 μg / L. The calibration curve was prepared by plotting the response count value (cps) of the original sample and each sample after adding the multi-element standard solution against the sample concentration. The concentration of the unknown sample was obtained by reversely extending the calibration curve to obtain the X-axis intercept.

[0059] 6. Instrument working conditions

[0060] When using ICP-MS to detect organic compounds, direct injection requires an organic sample introduction system and an oxygen introduction device. Oxygen reacts with carbon in the organic compound to produce carbon dioxide, which is then expelled. This effectively reduces carbon interference errors in the test results. Furthermore, using dry, pure He collision mode removes potential interferences, significantly improving the measurement accuracy of Cr52, Fe56, Cu63, and As75. Furthermore, a 1.0 mm inner diameter center tube reduces the possibility of organic volatiles entering the plasma; a platinum cone is used to minimize cone loss; a PFA nebulizer and an organic solvent-resistant piping system are used. Specific operating parameters are shown in Table 2.

[0061] Table 2 Inductively coupled plasma mass spectrometer operating parameters

[0062]

[0063] 7. Linear Relationship and Detection Limit

[0064] A 1:1 mixture of BDO and NMP was added to a 100 mL perfluoroalkoxy resin (PFA) bottle as 0 μg / L. Then, a mixed standard solution was added with concentrations of 0.5 μg / L, 1 μg / L, 5 μg / L, and 10 μg / L, respectively. A standard curve was drawn with the concentration of each element as the horizontal axis and the cps count value of the element to be measured as the vertical axis. The results showed that the 39 metal elements had a good linear relationship within their concentration range. The specific results are shown in Tables 3 and 4.

[0065] Table 3 cps count values ​​of each element at different concentrations

[0066]

[0067] Using a 1:1 mixture of BDO and NMP in a PFA vial as a blank sample, each of the 39 target metal elements was scanned 11 times. The instrument workstation automatically calculated the standard deviation (S). The method detection limit (MDL) for each element was determined using the formula "MDL = 3S / k" (where k is the slope of the calibration curve). The results are shown in Table 4.

[0068] Table 4 Standard curve relationship, detection limit, and precision

[0069]

[0070]

[0071] The above results show good linear relationships for each element, with correlation coefficients ranging from 0.9990 to 1.0000 and a detection limit of less than 0.001 μg / L. After repeated testing, the data showed that the instrument precision RSD value was less than 5. According to the requirements of GB / T39486-2020, General Rules for Inductively Coupled Plasma-Mass Spectrometry, when the content of the detected element is less than 1 μg / L, the precision RSD value is less than 15, and the selected method meets the detection requirements.

[0072] 8. Spike recovery

[0073] A mixed standard solution of each metal element with a concentration of 1 μg / L was added to a PFA bottle containing a mixture of BDO and NMP. Each element was scanned 11 times and the obtained value was used as the spiked recovery rate. The results are shown in Table 5.

[0074] Table 5 Spiked recovery of each element

[0075]

[0076]

[0077] From the above results, it can be seen that the spiked recovery rate is between 92.21% and 105.96%, which is in line with the accuracy range corresponding to the content of the elements to be measured in GB39480-2020.

[0078] 9. Effect of solvent on BDO analysis

[0079] The physicochemical properties of the solvent directly affect injection stability, anti-interference ability, and detection accuracy. Under the same injection conditions as in Table 2 (nebulizer chamber 2°C, argon flow rate 0.5 L / min), the effects of different organic solvents diluted at a 1:1 ratio of BDO were compared, using NMP as the benchmark.

[0080] Table 6 Comparison of performance of BDO diluted with different organic solvents

[0081]

[0082]

[0083] As can be seen, matching the freezing point is crucial. DMSO (freezing point 18.4°C) precipitates solids at 2°C, leading to blockage. Ethylene glycol (-13°C) is close to its precipitation point, resulting in poor fluidity and unstable injection. While ethanol does not solidify, its polarity is weaker than BDO, leading to inadequate dissolution of metal complexes (significantly lower Al recovery). Ethylene glycol's insufficient viscosity reduction leads to poor atomization efficiency (RSD >12%). NMP and DMF offer the best overall performance, both achieving low-temperature fluidity, complete miscibility, and low carbon deposition. However, DMF is more toxic than NMP, making it the optimal choice.

[0084] 10. Influence of atomization chamber temperature

[0085] The NMP dilution (1:1) and argon flow rate (0.5 L / min) were fixed and the nebulizer chamber temperature was changed to investigate the detection performance.

[0086] Table 7 Effect of atomization chamber temperature on detection performance

[0087]

[0088] It can be seen that when the temperature is ≥10°C, the volatilization of organic matter intensifies and carbon deposition increases significantly, resulting in unstable signals and a sharp reduction in torch life. When the temperature is ≤0°C, crystals precipitate from the diluent and clog the pipeline. 2°C is the equilibrium point, which can minimize carbon deposition while avoiding solidification, ensuring long-term stable analysis (the torch connection working time in Table 7 refers to the time of continuous operation without clogging).

[0089] 11. Plasma gas impact

[0090] The NMP dilution (1:1) and the atomization chamber temperature (2°C) were kept constant, and the oxygen inlet velocity in the argon-oxygen mixture was changed to explore the effect on the plasma.

[0091] Table 8 Effect of gas conditions on plasma stability

[0092]

[0093] It can be seen that both pure Ar and air modes suffer from rapid carbon deposition, leading to flameout and failing to meet continuous detection requirements. When the oxygen flow rate is precisely controlled at 0.5 L / min, carbon deposition is controllable and the signal-to-noise ratio is optimal (carbon is effectively burned into CO2, reducing background interference). When the oxygen flow rate is ≥1.0 L / min, excess oxygen cools the plasma, resulting in a decrease in sensitivity (the signal-to-noise ratio decreases by 38%).

[0094] In summary, the freezing point of 1,4-butanediol (BDO) significantly increases when mixed with N-methylpyrrolidone (NMP) in a 1:1 mass ratio, enabling the direct determination of 39 trace metal elements, including lithium, beryllium, and boron, in BDO using inductively coupled plasma mass spectrometry (ICP-MS). Experimental data demonstrated linear correlation coefficients ranging from 0.9990 to 1.0000 for each element, spiked recoveries ranging from 92.21% to 105.96%, a limit of detection below 0.001 μg / L, and precision relative standard deviations (RSDs) less than 5%.

[0095] The detection method of the present invention achieves efficient, low-error, and interference-resistant multi-element simultaneous analysis through NMP dilution to eliminate aqueous phase interference, oxygenation to assist in reducing carbon deposition in the cone hole, and a 2°C atomization chamber to stabilize the sample injection environment. It provides a reliable solution for the trace detection of metal elements in low-freezing-point and viscous organic matter, and has important application value for the quality control of chemical raw materials and the development of analytical technologies in related fields.

[0096] The embodiments described above are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by persons skilled in the art should fall within the scope of protection defined by the claims of the present invention.

Claims

1. An ICP-MS detection method for 39 trace metal elements in 1,4-butanediol, characterized in that: The following steps are involved: (1) mixing 1,4-butanediol and N-methylpyrrolidone to obtain a sample to be tested; (2) Prepare multi-element standard solutions with a concentration of 0.5-10 μg / L and draw a standard curve using the standard addition method; (3) The sample to be tested was directly injected into the ICP-MS, wherein the temperature of the nebulizer chamber was 2°C and the auxiliary gas was an argon-oxygen mixture; the metal element content was calculated using the standard curve; The multi-element standard solution includes 39 trace metal elements to be tested.

2. The ICP-MS detection method according to claim 1, wherein The mass ratio of the 1,4-butanediol to N-methylpyrrolidone is (0.8-1.6):

1.

3. The ICP-MS detection method according to claim 1, wherein In the argon-oxygen mixed gas, the volume fraction of oxygen accounts for 20%.

4. The ICP-MS detection method according to claim 1, wherein The 39 trace metal elements include: lithium, beryllium, boron, sodium, magnesium, aluminum, potassium, calcium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, germanium, arsenic, rubidium, strontium, zirconium, niobium, rhodium, silver, palladium, cadmium, indium, tin, antimony, cesium, barium, tantalum, tungsten, platinum, gold, thallium, lead and bismuth.

5. The ICP-MS detection method according to claim 1, wherein The radio frequency power of the ICP-MS was 1550 W, and the carrier gas argon flow rate was 0.5 L / min.

6. The ICP-MS detection method according to claim 1, wherein The test is carried out in a Class 100 clean room.

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