An analytical method for determining titanium in contrast agents by inductively coupled plasma tandem mass spectrometry

Abstract

The invention discloses an analytical method for determining titanium in a contrast agent by inductively coupled plasma tandem mass spectrometry, which is characterized by comprising the following steps: (1) preparing a calibration solution: diluting a Ti standard solution with a nitric acid solution to prepare a series of concentration calibration solutions; (2) preparing an internal standard solution: preparing a Sc internal standard solution with a nitric acid solution; (3) processing a sample: diluting the sample with a nitric acid solution to obtain a sample solution; (4) performing an on-machine detection: mixing the internal standard solution into a sample solution, a calibration solution and a blank solution online with a standard T-type internal standard mixing joint; in an MS / MS mode, selecting N2O as a reaction gas, and using a mass transfer method in an ORS to mix Ti + Transfer to TiN + The determination was performed to eliminate all mass spectral interferences; N2O was used as a reaction gas to eliminate mass spectral interferences through a mass transfer reaction, providing a new method for the interference-free determination of ultra-trace Ti in contrast agents.

Description

Technical Field

[0001] The invention relates to the technical field of biological detection, and in particular to an analytical method for determining titanium in a contrast agent by inductively coupled plasma tandem mass spectrometry. Background Art

[0002] As a necessary tool for imaging diagnosis, contrast agents are mostly packaged in pharmaceutical glass containers. Metal oxides are added to pharmaceutical glass during production to improve the performance of the glass. When the interaction between the contrast agent and the inner surface of the glass causes the structure of the inner surface of the glass to be destroyed, these metal oxide components can easily migrate into the contrast agent in the form of metal ions. In order to improve the water resistance and other properties of the inner surface of the glass container, the inner surface of the glass container is usually chemically treated. Although this treatment process can improve the water resistance of the glass, it may make the structure of some glass fragile. There are also a small number of glass containers that use inner surface coating treatment. The film material may be corroded by the drug, and both the film material and the glass components may migrate into the drug. For this reason, the "Technical Guidelines for Compatibility Research of Chemical Drug Injections and Pharmaceutical Glass Packaging Containers (Trial)" proposes to conduct quantitative inspections of metal ions that migrate into injections and conduct safety assessments. Among them, Ti is a common element that migrates into the injection solution. Establishing an analytical method suitable for the rapid and accurate determination of the impurity element Ti in contrast agents is of great significance for correctly evaluating the quality of contrast agents and ensuring drug safety.

[0003] For the determination of ultra-trace Ti in complex samples, atomic analysis techniques are currently mainly used, including electrothermal atomic absorption spectroscopy (ETAAS), inductively coupled plasma optical emission spectroscopy (ICP-OES) and inductively coupled plasma mass spectrometry (ICP-MS). However, due to the refractory nature of Ti, the determination of Ti by ETAAS requires a higher atomization temperature, which shortens the service life of the graphite tube (about 50 times). The carbon slag residues formed by the sample in the graphite tube must be regularly removed to ensure the reproducibility of the analysis, and it does not have high-throughput analysis characteristics; the concentration of Ti in normal contrast agents is usually lower than the detection limit of ICP-OES, and ICP-OES cannot accurately quantify ultra-trace Ti in contrast agents; ICP-MS has the analytical characteristics of high sensitivity, high throughput and extremely low detection limit, and is usually the preferred analytical technology for ultra-trace elements, but when used for the precise determination of ultra-trace Ti in contrast agents, all Ti isotopes will face complex mass spectral interference formed by high-concentration matrix elements. The most common method to eliminate mass spectrometry interference is the collision / reaction cell (CRC) technology. However, even when ICP-MS equipped with an octopole collision / reaction cell (ORS) is used to measure ultra-trace Ti in contrast agents, it is not possible to eliminate all interferences in He collision mode or H2 reaction mode. Ultra-trace Ti is measured using sector magnetic field inductively coupled plasma mass spectrometry (SF-ICP-MS). The detection limit of Ti can reach ng / L level in high-resolution mode, but the sensitivity of Ti is seriously impaired in high-resolution mode. Summary of the invention

[0004] In view of the shortcomings of the prior art, the present invention aims to provide an analytical method for determining titanium in contrast agents by inductively coupled plasma tandem mass spectrometry. N2O is used as a reaction gas to eliminate mass spectrometry interference, and mass transfer reaction is used to eliminate mass spectrometry interference, providing a new method for interference-free determination of ultra-trace Ti in contrast agents.

[0005] To achieve the above object, the present invention adopts the following technical solution: an analytical method for determining titanium in a contrast agent by inductively coupled plasma tandem mass spectrometry, characterized in that it comprises the following steps:

[0006] (1) Preparation of calibration solution: Dilute the Ti standard solution with nitric acid solution to prepare a series of concentration calibration solutions;

[0007] (2) Preparation of internal standard solution: Prepare Sc internal standard solution using nitric acid solution;

[0008] (3) sample treatment, diluting the sample with a nitric acid solution to obtain a sample solution;

[0009] (4) On-machine testing: Use a standard T-type internal standard mixing joint to mix the internal standard solution into the sample solution, calibration solution, and blank solution online; In the MS / MS mode, select N2O as the reaction gas and use the mass transfer method in the ORS to mix Ti + Transfer to TiN + The assay was performed eliminating all mass spectral interferences;

[0010] The ICP-QQQ operating parameters were:

[0011] RF power, 1500W; sampling depth, 8mm; nebulizer gas flow rate, 0.70L / min; compensation gas flow rate, 0.45L / min; extraction voltage 1, 0V; extraction voltage 2, -70V; reaction gas:

[0012] N2O; Reagent gas flow rate, 0.40 mL / min; Octopole bias voltage, -10 V; Kinetic energy discrimination voltage, 10 V; Analytical isotope, 48 Ti.

[0013] In the above scheme: the mass concentration of the nitric acid solution is 2%.

[0014] In the above scheme: the concentrations of the series of concentration calibration solutions are Ti series calibration solutions with concentrations of 0, 0.5, 2.5, 10, and 50 μg / L, respectively.

[0015] In the above scheme: the concentration of the internal standard solution is 1 mg / L.

[0016] In the above scheme: the sample is diluted 100 times with nitric acid with a mass concentration of 2% to obtain a sample solution. The mass-to-charge ratio m / z of the first-stage quadrupole filter Q1 is 48, and the m / z of the second-stage quadrupole filter Q2 is 62.

[0017] Beneficial effect: The present invention proposes a new strategy for accurately determining ultra-trace Ti in contrast agents using ICP-MS / MS. In MS / MS mode, N2O is selected as the reaction gas, and Ti is transferred to the ORS using mass transfer method. + Transfer to TiN + The determination was carried out to eliminate all mass spectrometry interferences, and the method was verified to be accurate and reliable through spike recovery experiments of contrast agent samples and comparative analysis using SF-ICP-MS. The accurate determination of ultra-trace Ti in contrast agents was achieved, and the analysis effect was significantly better than the currently common NH3 / He reaction mode and O2 reaction mode, providing technical support for the detection of ultra-trace Ti in contrast agents. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 Mass spectrum of Ti at 1 μg / L using N2O as the reaction gas in MS / MS mode.

[0019] Figure 2 Optimization results of N2O flow rate. DETAILED DESCRIPTION

[0020] The present invention is further described in detail below through specific embodiments:

[0021] Example 1

[0022] 1. Instruments and reagents

[0023] Agilent 8800 inductively coupled plasma tandem mass spectrometer (ICP-MS / MS, Agilent, USA) was equipped with a MicroMist nebulizer, a Peltier-cooled Scott-type spray chamber, an octopole collision reaction cell (ORS) located between two quadrupole filters, and a Milli-Q ultrapure water machine (Millipore, USA). The optimized ICP-MS / MS operating conditions were as follows: scan mode, MS / MS; RF power, 1500W; sampling depth, 8mm; nebulizer gas flow rate, 0.70L / min; compensation gas flow rate, 0.45L / min; extraction voltage 1, 0V; extraction voltage 2, -70V; reaction gas: N2O; reaction gas flow rate, 0.40mL / min; octopole bias voltage, -10V; kinetic energy discrimination voltage, 10V; analysis isotope, 48 Ti.

[0024] 1000 mg / L Ti single element standard solution (Merck, Germany); 1000 mg / L Sc internal standard element standard solution (Merck, Germany); 65% (w / w) ultrapure HNO3 (Merck, Germany), sub-boiling distillation; ultrapure water (resistivity greater than 18.2 MΩ·cm).

[0025] 2. Sample solution: The contrast agent samples were gadoterate meglumine injection (specification: 15 mL) and gadopentetate meglumine injection (specification: 12 mL) produced by 4 different domestic manufacturers. The contrast agent samples were diluted 100 times with nitric acid having a mass concentration of 2% to obtain sample solutions.

[0026] 3. Accelerated test sample solution: Take an appropriate amount of sample and place it at a temperature of (40±2)℃ and a relative humidity of (75±5)% for 1 month and 3 months respectively to obtain the accelerated test sample.

[0027] 4. Experimental methods

[0028] A series of Ti mixed standard solutions with mass concentrations of 0, 0.5, 2.5, 10, and 50 μg / L were prepared using 2% nitric acid, and analyzed with sample solutions and blank solutions using ICP-MS / MS. In MS / MS mode, the mixed reaction gas N2O was selected to eliminate mass spectrometry interference. A 1 mg / L Sc internal standard solution was added online to all test solutions through a standard T-type internal standard mixing joint, and the determination was completed within 24 hours.

[0029] 5. Results and Discussion

[0030] 5.1 Reagent Gas Selection in MS / MS Mode

[0031] Ti has five isotopes 46 Ti, 47 Ti, 48 Ti, 49 Ti, 50 Ti, where 48 The abundance of Ti is the highest (73.72%), and the abundance of the other four isotopes is less than 10%. 48 Ti is the analytical isotope. In the contrast agent sample, the isotope of Ca 48 Ca + and polyatomic ions ( 32 S 16 O + , 34 S 14 N + , 33 S 15 N + , 31 P 17 O + , 14 N 16 O 18 O + , 14 N 17 O2 + , 12 C4 + , 36 Ar 12 C + ) Serious interference 48 For the determination of Ti, even using ICP-MS with CRC in He collision mode or H2 reaction mode, it is not possible to eliminate interference. Therefore, low-abundance isotopes are usually selected. 47Ti was determined in He collision mode, and the analytical sensitivity was low. ICP-MS / MS uses a dual quadrupole filter to select ions from ICP and ORS respectively. By setting the mass-to-charge ratio (m / z) of the first-stage quadrupole filter (Q1) between ICP and ORS, a large amount of interference from ICP is eliminated, and the types and number of ions entering ORS are reduced. After leaving ORS, the reaction products enter the second-stage quadrupole filter (Q2) between ORS and the detector. Q2 is used to set the m / z to eliminate interference. Compared with ICP-MS, ICP-MS / MS eliminates interference more thoroughly. In the MS / MS mode of ICP-MS / MS, NH3 / He, O2, and N2O were used as reaction gases to eliminate interference, and the results were investigated. 48 The sensitivity and background equivalent concentration (BEC) of Ti are shown in Table 1.

[0032] Table 1 Determination of different reaction gases in MS / MS mode 48 Sensitivity and Background Equivalent Concentration (BEC) of Ti

[0033]

[0034] In MS / MS mode, O2 was used as the reaction gas and Ti + Exothermic reaction with O2 (Ti + +O2→TiO + +O+1.96eV,△H r <0), spontaneously generates a large amount of TiO + , while Ti + The main interfering ion is Ca + ,PO + The reaction with O2 is an endothermic process. Usually, Ca + ,PO + It is difficult to react with O2, while SO + Exothermic reaction with O2 to generate SO2 + After that, it will quickly undergo a charge transfer reaction with O2 without interfering with TiO + Other interfering ions ( 34 S 14 N + , 33 S 15 N + , 14 N 16 O 18 O + , 14 N 17 O2 + , 12 C4 + , 36 Ar12 C + ) does not react with O2. However, when Ca migration in the pharmaceutical glass in the contrast agent and S and P residues in the synthesis of drug raw materials are high, even a very limited O atom transfer reaction will react with Ti + Similarly, the corresponding oxide ions are formed to interfere with the determination, making it impossible to accurately determine the ultra-trace Ti in the contrast agent. Therefore, the interference is not completely eliminated in the O2 reaction mode. Using NH3 / He as the reaction gas, Ti and NH3 form a large number of complex ions or cluster ions, and the high-abundance cluster ion TiNH2(NH3)4 is selected. + Ultra-trace Ti in contrast agents can be accurately determined, but the sensitivity is low. As can be seen from Table 1, in the NH3 / He reaction mode, although the BEC of Ti is lower than that in the O2 reaction mode, the sensitivity is much lower than that in the O2 reaction mode. In the N2O reaction mode, N2O and Ti undergo primary O atom, secondary O atom, and N atom transfer reactions, respectively. The N atom transfer reaction generates 48 Ti 14 The BEC obtained by N is extremely low, the interference is eliminated most thoroughly, and the sensitivity is higher than that of the NH3 / He reaction mode. This shows that the analysis effect of using N2O as the reaction gas and the product ions transferred by N atoms is significantly better than the currently common NH3 / He reaction mode and O2 reaction mode.

[0035] 5.2 Elimination of mass spectrometry interference

[0036] In order to evaluate the ability of using N2O as a reaction gas to eliminate mass spectrometric interference in MS / MS mode, a 1 μg / L Ti standard solution (2% (v / v) HNO3 medium) was prepared, and 10 mg / L Ca, 10 mg / L S and 10 mg / L P were added as interfering elements. The determination was carried out in MS / MS mode using N2O as a reaction gas. 48 The mass spectrometric behavior of Ti is shown in Figure 1 Since N2O has a much higher ability to undergo O atom transfer reaction than O2, 48 Ti + Reacting with N2O, a large amount of 48 Ti 16 O + , interfering ions 48 Ca + , 32 S 16 O + , 31 P 17 O + Can react with N2O to produce a small amount of 48 Ca 16 O + , 32 S 16O2 + and 31 P 17 O 16 O + interference 48 Ti 16 O + Determination of 48 Ti + The secondary O atom transfer reaction with N2O can generate 48 Ti 16 O2 + The obtained BEC is comparable to the NH3 / He reaction mode, but is still nearly an order of magnitude higher than the BEC of the N atom transfer reaction, indicating that, like NH3 / He, there are still potential interferences that have not been completely eliminated. Figure 1 It can be seen that all interfering ions did not undergo N atom transfer reaction with N2O (no interfering peak was observed at m / z=62). 48 Ti + N atom transfer reaction with N2O generates 48 Ti 14 N + ( 48 Ti + +N2O→ 48 Ti 14 N + +NO), thus verifying the use of 48 Ti 14 N + The interference-free determination of Ti was achieved for the product ions, and the sensitivity was higher than the currently common NH3 / He reaction mode, and the interference elimination capability was also better than the NH3 / He reaction mode and the O2 reaction mode.

[0037] 5.3 Optimization of the reaction gas N2O flow rate

[0038] The N2O flow rate was optimized by examining the change in the signal-to-background ratio (S / B) of a 1 μg / L Ti standard solution at different N2O flow rates. Figure 2 It can be seen that as the N2O flow rate increases, the generated 48 Ti 14 N + Gradually increase, when the N2O flow rate reaches 0.4mL / min, 48 Ti 14 N + The signal intensity reaches the maximum value, while the background signal intensity hardly changes. At this time, the S / B of Ti is the largest. Then, the N2O flow rate is increased. 48 Ti 14 N +The signal intensity began to decrease. Therefore, the N2O flow rate was selected to be 0.4 mL / min, which resulted in the maximum S / B of Ti and the best analysis effect.

[0039] 5.4 Evaluation of analytical performance of the method

[0040] Prepare a series of Ti standard solutions of 0, 0.5, 2.5, 10, and 50 μg / L respectively, and select 48 Ti is the analytical isotope, and the established analytical method was used for determination. The detection limit (LOD) of the method was investigated. The results showed that the linear correlation coefficient of Ti in the range of 0-50μg / L was ≥0.9999, showing a good linear relationship. The LOD of Ti was as low as 0.19μg / L.

[0041] To evaluate the accuracy of the method, a contrast agent sample was added with 5, 10, and 20 μg / L Ti standard solution. 48 Ti is the analytical isotope. The spiked sample was determined 6 times according to the experimental method, and the three-level spiked recovery of Ti was calculated. The spiked sample was determined 6 times by SF-ICP-MS for comparative analysis, and the t-test method was used to perform statistical analysis on the determination results of the two analytical methods. It can be seen from Table 2 that the spiked recovery of Ti is between 94.4% and 104%, and the relative standard deviation (RSD) is 1.8% to 2.4%. Statistical analysis shows that at a confidence level of 95%, there is no significant difference (p>0.05) between the determination results of the established method and the SF-ICP-MS method, which verifies that the method has good accuracy and high precision.

[0042] Table 2 Accuracy and precision of the method

[0043]

[0044] 5.5 Sample analysis and risk assessment

[0045] The established analytical method was used to analyze gadoterate dimeglumine injection (specification of 15 mL, sample numbers A and B) and gadopentetate dimeglumine injection (specification of 12 mL, sample numbers C and D) produced by four different domestic manufacturers. The accelerated test samples were also analyzed, and the results are shown in Table 3. The Ti content in the four contrast agents was extremely low, and there was no significant change in the Ti content under the accelerated test conditions, indicating that Ti migration due to the interaction between the contrast agent and the glass packaging container did not occur.

[0046] Table 3 Contrast agent sample analysis results

[0047]

[0048] Since Ti has good inertness and biocompatibility, and almost no physiological toxicity, there is no recommended daily exposure (PDE) in ICH Q3D and other principles. In this study, the initial risk assessment was conducted according to the PDE limit of 1500 μg / d in ICH Q3D. According to the FDA's maximum allowable dose of contrast agents of 0.3 mmol / kg, the maximum daily dosage is converted to 42 mL (based on 70 kg), and the maximum possible daily intake of Ti is calculated based on this. According to the PDE limit of 1500 μg / day, it can be seen that the Ti content in the four contrast agents meets the limit requirements, indicating that the Ti impurity residues introduced during the production process of the contrast agents are basically controllable and there is no migration risk.

[0049] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution of the present invention, which should be included in the scope of the claims of the present invention.

Claims

1. An analytical method for determining titanium in a contrast agent by inductively coupled plasma tandem mass spectrometry, characterized in that: The following steps are involved: (1) Preparation of calibration solution: Dilute the Ti standard solution with nitric acid solution to prepare a series of concentration calibration solutions; (2) Preparation of internal standard solution: Prepare Sc internal standard solution using nitric acid solution; (3) sample treatment, diluting the sample with a nitric acid solution to obtain a sample solution; (4) On-line testing: using a standard T-type internal standard mixing joint to mix the internal standard solution into the sample solution, calibration solution, and blank solution; In MS / MS mode, N2O was selected as the reaction gas and Ti was concentrated by mass shift in ORS. + Transfer to TiN + The assay was performed eliminating all mass spectral interferences; The ICP-QQQ operating parameters were: RF power, 1500W; sampling depth, 8mm; nebulizing gas flow rate, 0.70L / min; compensation gas flow rate, 0.45L / min; extraction voltage 1, 0V; extraction voltage 2, -70V; Reagent gas: N2O; Reagent gas flow rate, 0.40 mL / min; Octopole bias voltage, -10 V; Kinetic energy discrimination voltage, 10 V; Analytical isotope, 48 Ti.

2. The method for determining the calcium content in a gadolinium-based contrast agent by inductively coupled plasma tandem mass spectrometry according to claim 1, characterized in that: The mass concentration of the nitric acid solution is 2%.

3. The method for determining the calcium content in a gadolinium-based contrast agent by inductively coupled plasma tandem mass spectrometry according to claim 2, characterized in that: The concentrations of the series of concentration calibration solutions are 0, 0.5, 2.5, 10, and 50 μg / L Ti series calibration solutions, respectively.

4. The method for determining the calcium content in a gadolinium-based contrast agent by inductively coupled plasma tandem mass spectrometry according to claim 3, characterized in that: The concentration of the internal standard solution was 1 mg / L.

5. The method for determining the calcium content in a gadolinium-based contrast agent by inductively coupled plasma tandem mass spectrometry according to claim 4, characterized in that: The sample was diluted 100 times with nitric acid having a mass concentration of 2% to obtain a sample solution.

6. The method for determining the calcium content in a gadolinium-based contrast agent by inductively coupled plasma tandem mass spectrometry according to any one of claims 1 to 5, characterized in that: The mass-to-charge ratio of the first-stage quadrupole filter Q1 is m / z 48, and the mass-to-charge ratio of the second-stage quadrupole filter Q2 is m / z 62.

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