A method for determining the content of a mixture of different forms of sulfate

Abstract

The application aims to provide a content determination method of a mixture containing different morphological sulfate salts. The method comprises the following steps: obtaining a to-be-tested solution which may contain sulfite, sulfate, thiosulfate and persulfate; determining the to-be-tested solution by using an electrospray high-resolution mass spectrometry to obtain characteristic ion intensity in the to-be-tested solution; and calculating the concentration of various morphological sulfate salts in the to-be-tested solution according to the characteristic ion intensity. The method is simple in operation, short in analysis time, convenient and fast. The method can qualitatively and quantitatively analyze different morphological sulfate salts without chromatographic separation.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of chemical detection and analysis, and particularly relates to a content detection technology for a mixture containing various sulfate salts. BACKGROUND

[0002] Sulfate compounds belong to inorganic compounds, which are widely used in various fields such as food, chemical industry, environment, material, geology and mineral resources. Depending on different purposes, the analysis methods of sulfate are also different. The qualitative and quantitative analysis methods of sulfate include volumetric method, gravimetric method, spectrophotometry, ion chromatography (IC), inductively coupled plasma emission spectrometry (ICP) and the like. For example, the determination methods of sulfite include potassium iodide-potassium iodate titration method and hydrochloric acid pararosaniline spectrophotometry, the determination method of sulfate includes barium sulfate gravimetric method, the determination method of thiosulfate includes iodine titration method, and the like. The determination of sulfate compounds by volumetric method, gravimetric method and spectrophotometry is easily interfered by coexisting substances, the operation is complicated, the sensitivity and accuracy are limited, and various different forms of sulfate cannot be determined simultaneously. IC has separation function, and different forms of sulfate can be separated by optimizing appropriate chromatographic conditions. The qualitative and quantitative analysis is performed according to the retention time and peak area of the standard substance of different forms of sulfate. The principle of ICP for determining the content of sulfate is to determine the content of sulfur element, and then to convert the content of different forms of sulfate according to different coefficients. ICP cannot distinguish the content of different forms of sulfate. If the content of different forms of sulfate is to be determined, the different forms of sulfate need to be separated by separation technology, and then determined respectively. Or, ICP is combined with IC to determine the content of different forms of sulfate on line, and the qualitative and quantitative analysis is the same as IC. The characteristic spectral line of ICP for determining sulfur element is 180 nm, which is in the ultraviolet region. Therefore, the light path needs to be swept by inert gas for a long time to eliminate the influence of air.

[0003] In summary, most of the analysis methods of sulfate are based on the analysis of sulfur element. The gravimetric method and volumetric method belong to conventional physicochemical analysis methods, the operation of which is complicated, the sensitivity and accuracy are poor, and the forms of phosphorus cannot be distinguished. ICP can accurately quantify the sulfur element, but the form information of phosphorus cannot be obtained. The chromatography and combined method such as IC and IC-ICP can qualitatively and quantitatively analyze the form of sulfur, but the qualitative analysis needs to be compared with the standard substance of the corresponding form of sulfur compound. SUMMARY

[0004] The purpose of the present application is to provide a content determination method for a mixture containing different forms of sulfate:

[0005] (1) obtaining a to-be-measured solution which may contain sulfite, sulfate, thiosulfate and persulfate;

[0006] (2) The to-be-tested solution is determined by using an electrospray high-resolution mass spectrometry:

[0007] (2-1) Instrument: high-resolution liquid chromatograph-mass spectrometer, equipped with an ESI electrospray ion source; ultrapure water instrument; electronic balance;

[0008] (2-2) Reagent: ultrapure water

[0009] (2-3) In an embodiment, the instrument conditions are as follows: ESI source negative ion mode, Gas Temp: 100℃, Drying Gas: 13L / min, Nebulizer: 35psi, Sheath Gas Temp: 100℃, Sheath Gas Flow: 3L / min; Vcap: 700V, Nozzle Voltage: 1500V; Fragmentor: -150V, Skimmer-65V, Oct 1RF Vpp: 750V; sample flow rate: 0.2mL / min;

[0010] (3) Obtain the response intensity of the characteristic ions of various forms of sulfate in the to-be-tested solution;

[0011] Among them, the characteristic ions and mass-to-charge ratios (m / z) corresponding to different forms of sulfate are as follows:

[0012] The characteristic ion of sulfite is HSO3 - , m / z is 80.9656;

[0013] The characteristic ion of sulfate is HSO4 - , m / z is 96.9613;

[0014] The characteristic ion of thiosulfate is HS2O3 - , m / z is 112.9389;

[0015] The characteristic ion of persulfate is S2O8 2- , m / z is 95.9534;

[0016] The above characteristic ions may not be unique, other characteristic ions are related to the types of cations and other coexisting ions, and all contain SO3 2- , SO4 2- , S2O3 2- , S2O8 2- , etc. Oxygen-containing anion groups.

[0017] (4) According to the response intensity of the characteristic ions, the concentrations of various forms of sulfate in the to-be-tested solution are calculated:

[0018] (4-1) In the concentration range of 0.01-1mmol / L:

[0019] The linear relationship between the sulfite concentration x and the corresponding characteristic ion (m / z 80.9656) response intensity y is: y=191741x+8834.7;

[0020] The linear relationship between the sulfate concentration x and the corresponding characteristic ion (m / z 96.9613) response intensity y is: y=809435x+16664;

[0021] The linear relationship between the thiosulfate concentration x and the corresponding characteristic ion (m / z 112.9389) response intensity y is: y=831060x+7196.6;

[0022] (4-2) In the concentration range of 0.01-0.2 mmol / L:

[0023] The linear relationship between the persulfate concentration x and the corresponding characteristic ion (m / z 95.9534) response intensity y is: y=21882745x+238192;

[0024] Wherein, the unit of concentration x is mmol / L;

[0025] Further, the expression of the sulfite is X m H n SO3, the expression of the sulfate is X m H n SO4, the expression of the thiosulfate is X m H n S2O3, the expression of the persulfate is X m H n S2O8; wherein, X is a cation that can be Na, K, Mg, NH4, etc., wherein m≥1, n≥0.

[0026] Further, the ion source ionization is electrospray ionization (ESI).

[0027] Further, the ionization is detected in negative ion mode.

[0028] Further, the mass analyzer can be a time-of-flight mass analyzer (TOF), an electrostatic field orbitrap mass analyzer (Obitrap), a Fourier transform ion cyclotron resonance mass analyzer (FTICR), and a tandem mass analyzer of the above mass analyzers.

[0029] Compared with the prior art, the beneficial effects of the present application are:

[0030] 1) The method of the present application is simple to operate, short in analysis time, and convenient and fast;

[0031] 2) This invention enables qualitative and quantitative analysis of different sulfate forms without separation;

[0032] 3) This invention has strong reference value for the detection of other inorganic compounds. Attached Figure Description

[0033] Figure 1 ESI-mode mass spectrum and characteristic ions of Na2SO3;

[0034] Figure 2 ESI-mode mass spectrum and characteristic ions of Na2SO4;

[0035] Figure 3 ESI-mode mass spectrum and characteristic ions of Na2S2O3;

[0036] Figure 4 ESI-mode mass spectrum and characteristic ions of Na2S2O8. Detailed Implementation

[0037] The present invention will be further described below with reference to embodiments, but it should not be construed that the scope of the present invention is limited to the following embodiments. Various substitutions and modifications made based on ordinary technical knowledge and common practices in the art without departing from the above-described technical concept of the present invention should be included within the scope of protection of the present invention.

[0038] Example 1:

[0039] In this embodiment, the contents of sodium sulfite, sodium sulfate, sodium thiosulfate, and sodium persulfate in a sodium sulfate simulated mixture were determined by electrospray time-of-flight high-resolution mass spectrometry.

[0040] Specifically, the steps include the following:

[0041] 1. Instruments and reagents:

[0042] (1) Instruments: QTOF 6545XT high-resolution liquid chromatography-mass spectrometry system (Agilent Technologies, USA), equipped with ESI electrospray source and syringe pump; Ellga Chorus 1 Complete ultrapure water system; Sartorious Quintix 213 electronic balance.

[0043] (2) Reagents: Sodium sulfite (Na2SO3), sodium sulfate (Na2SO4), sodium thiosulfate (Na2S2O3), and sodium persulfate (Na2S2O8), all of analytical grade, were obtained from Sigma-Aldrich. The above reagents were mixed in a certain mass ratio of 4:3:2:1 to prepare a simulated test sample.

[0044] 2. Methods and Results

[0045] (1) Solution preparation

[0046] a. Preparation of standard solutions: Accurately weigh the corresponding masses of Na2SO3, Na2SO4, Na2S2O3, and Na2S2O8, and prepare standard stock solutions with a concentration of 10 mmol / L using ultrapure water. Take the corresponding volumes of each standard stock solution and prepare mixed standard solutions with concentrations of 0.001, 0.002, 0.005, 0.01, 0.02, 0.05, 0.1, 0.2, 0.5, 1, and 2 mmol / L, respectively.

[0047] b. Preparation of sample solution for the test sample: Weigh 0.1000g of the simulated mixture sample, dissolve it in ultrapure water and make up to 100mL in a volumetric flask. It can be further diluted with ultrapure water to a suitable concentration according to the response intensity.

[0048] (2) Instrument conditions

[0049] Mass spectrometry conditions: ESI source negative ion mode, Gas Temp: 100℃, Drying Gas: 13L / min, Nebulizer: 35psi, Sheath Gas Temp: 100℃, Sheath Gas Flow: 3L / min; Vcap: 700V, Nozzle Voltage: 1500V; Fragmentor: -150V, Skimmer: -65V, Oct 1RF Vpp: 750V; Injection flow rate: 0.2mL / min;

[0050] (3) Characteristic ions

[0051] Based on the mass spectrometry response of each standard solution, the characteristic ion m / z values ​​for Na₂SO₃, Na₂SO₄, Na₂S₂O₃, and Na₂S₂O₈ were determined to be 80.9656 and 102.9467, 96.9613 and 118.9425, 112.9389 and 134.9187, and 95.9534 and 214.8956, respectively, corresponding to the molecular formulas HSO₃. - and NaSO3 - HSO4 - and NaSO4 - HS2O3 - and NaS2O3 - S2O8 2- and NaS2O8 - .

[0052] (4) Standard Curve

[0053] Within the concentration range of 0.001–2 mg / L, the concentrations of the four substances showed a linear relationship with the sum of their characteristic ion strengths. The fitting parameters of the relevant standard curves are shown in Table 1.

[0054] Table 1 Linear Relationship

[0055]

[0056] (5) Measurement results

[0057] Based on the sum of the characteristic ionic strengths of each substance in the test sample, and referring to the standard curve, the concentrations of each substance in the solution were calculated. The content of different forms of sodium sulfate in the sample was then calculated based on the dilution factor and the molecular weight of each sodium sulfate. The results are as follows:

[0058] The sodium sulfite (calculated as Na2SO3) content is 39.8%, the sodium sulfate (calculated as Na2SO4) content is 30.2%, the sodium thiosulfate (calculated as Na2S2O3) content is 19.6%, and the sodium persulfate (calculated as Na2S2O8) content is 10.2%.

Claims

1. A method for determining the content of a mixture containing different forms of sulfate, characterized in that... : (1) Obtain the test solution that may contain Na2SO3, Na2SO4, Na2S2O3, or Na2S2O8; (2) Electrospray high-resolution mass spectrometry was used to determine the test solution: (2-1) Instruments: High-resolution liquid chromatography-mass spectrometry system, equipped with ESI electrospray ionization source; ultrapure water system; Electronic balance; Instrument conditions were as follows: ESI source negative ion mode, Gas Temp: 100℃, Drying Gas: 13 L / min, Nebulizer: 35 psi, Sheath Gas Temp: 100℃, Sheath Gas Flow: 3 L / min; Vcap: 700V, NozzleVoltage: 1500V; Fragmentor: -150V, Skimmer: -65V, Oct 1 RF Vpp: 750V; Injection flow rate: 0.2 mL / min. (2-2) Reagent: Ultrapure water (3) Obtain the response intensity of characteristic ions of various forms of sulfate in the test solution; The characteristic ions and mass-to-charge ratios (m / z) corresponding to different forms of sulfate are as follows: The characteristic ion corresponding to sodium sulfite is HSO3. - The m / z value is 80.9656. The characteristic ion corresponding to sodium sulfate is HSO4. - The m / z value is 96.9613. The characteristic ion corresponding to sodium thiosulfate is HS₂O₃. - The m / z value is 112.9389. The characteristic ion corresponding to sodium persulfate is S2O8. 2- The m / z value is 95.9534. (4) Calculate the concentrations of various forms of sulfate in the test solution based on the response intensity of the characteristic ions: (4-1) Within the concentration range of 0.01~1 mmol / L: The linear relationship between sulfite concentration x and the response intensity y of the corresponding characteristic ion (m / z 80.9656) is: y = 191741x + 8834.7; The linear relationship between sulfate concentration x and the response intensity y of the corresponding characteristic ion (m / z 96.9613) is: y = 809435x + 16664; The linear relationship between the concentration x of thiosulfate and the response intensity y of the corresponding characteristic ion (m / z 112.9389) is: y = 831060x + 7196.6; (4-2) Within the concentration range of 0.01~0.2 mmol / L: The linear relationship between persulfate concentration x and the response intensity y of the corresponding characteristic ion (m / z 95.9534) is: y = 21882745x + 238192; The unit of concentration x is mmol / L.

2. The method for determining the content of a mixture containing different forms of sulfate according to claim 1, characterized in that... The ion source ionization mentioned is electrospray ionization (ESI).

3. The method for determining the content of a mixture containing different forms of sulfate according to claim 2, characterized in that... The ion source ionization is detected in negative ion mode.

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