Sample treatment method based on digestion technology

Abstract

The invention relates to a pretreatment technology, and particularly provides a sample treatment method based on a digestion technology, the sample treatment method comprises a heating stage and an adjusting stage, in the heating stage, a carrier liquid and a sample in a water load and a resonant cavity are respectively heated by microwaves; the adjusting stage comprises the following steps that (A1) after heating for the time delta t, the temperature T11 of the carrier liquid and the temperature T21 of the water load at the same moment are obtained; (A2) obtaining A according to the temperature T11 and the temperature T21; (A3) judging whether A is within a set range or not; if the result is yes, the input impedance is matched with the load impedance in the resonant cavity; if not, entering the step (A4); and (A4) adjusting the position of the pin, and returning to the step (A1). The device has the advantages of convenience in adjustment and the like, and is applied to microwave digestion.

Description

Technical Field

[0001] The present invention relates to microwave digestion technology, and particularly to a sample processing method based on digestion technology. Background Art

[0002] Microwave digestion systems have been widely used and have outstanding performance in the fields of AAS, ICP-OES, ICP-MS, and electrochemical analysis, especially in trace element analysis, and are widely used in the fields of materials, geology, environment, energy, food and medicine, etc. Using microwaves to digest or extract analytical samples is a chemical analysis sample pretreatment technology that has developed rapidly in China in recent years.

[0003] As Figure 1 shown, a microwave digestion system mainly consists of components such as a magnetron 11, a waveguide, a coupling antenna 41, and a resonant cavity 42. The microwave energy output by the magnetron 11 is transmitted to the coupling antenna 41 through the waveguide, and is emitted by the coupling antenna 41 into the resonant cavity 42. The microwaves are reflected back and forth in the resonant cavity 42 to heat the carrier liquid 44 and the sample 43 load in the resonant cavity 42, causing the sample 43 to rapidly increase in temperature.

[0004] Due to factors such as changes in the sample 43 to be digested in the resonant cavity 42 and instrument assembly errors, the input impedance of the microwave digestion system will be mismatched with the load impedance. Therefore, the microwave power absorbed by the sample load will decrease, and most of the microwave power will be reflected back to the magnetron 11, ultimately resulting in a decrease in the temperature rise efficiency of the sample load, waveguide heating, and magnetron 11 arcing, which degrades the instrument performance. To address this problem, the existing solutions are as follows: 1. Solve the mismatch caused by installation problems by reinstalling the instrument.

[0005] 2. Make the impedance match by changing the load carrier liquid volume, sample tube rack, etc.

[0006] 3. Detect the reflection coefficient through external devices such as microwave network analyzer method, six-port detection technology, four-probe method, and additional phase bridge method to judge the change of the load, and then adjust the impedance of the waveguide.

[0007] The deficiencies of the above solutions are as follows: For the first and second methods, the operations are cumbersome and lack a scientific and effective judgment basis, unable to judge the impedance matching state of the system, and cannot fundamentally solve the problem.

[0008] For the third method, detecting the system matching state is only applicable to the product R & D experimental stage, and the external devices are expensive and complex, not suitable for engineering instruments in harsh working environments. Summary of the Invention

[0009] To solve the deficiencies in the above-mentioned existing technical solutions, the present invention provides a sample processing method based on digestion technology.

[0010] The object of the present invention is achieved through the following technical solutions: A sample processing method based on digestion technology, including a heating stage and an adjustment stage. In the heating stage, the water load, the liquid carrier, and the sample in the resonant cavity are respectively heated by microwaves; the adjustment stage includes the following steps: (A1) After heating for a time Δt, the temperature T of the liquid carrier at the same moment is obtained 11 and the temperature T of the water load 21 ; (A2) According to the temperature T 11 and the temperature T 21 A is obtained; A = 1 + 2D + 2·SQRT(D 2 + D), D = c 2 m 2 (T 21 - T 20 ) / [c 1 m 1 (T 11 - T 10 )]; c 2 and c 1 are the specific heat capacities of the water load and the liquid carrier respectively, m 2 and m 1 are the masses of the water load and the liquid carrier respectively, T 20 and T 10 are the initial temperatures of the water load and the liquid carrier respectively; (A3) Determine whether A is within the set range; If the result is yes, the input impedance matches the load impedance in the resonant cavity; If the result is no, go to step (A4); (A4) Adjust the position of the pin and return to step (A1).

[0011] Compared with the prior art, the beneficial effects of the present invention are as follows: By monitoring the temperatures of the liquid carrier in the resonant cavity and the water load in the circulator, A is obtained, thereby judging the change of the load in the resonant cavity and accurately determining the impedance matching effect of the microwave transmission system.

[0012] Using the obtained A, control driving units such as a stepping motor to adjust the position of the waveguide pin to achieve the impedance matching of the microwave transmission system and improve the performance of the system.

[0013] By improving the effect of impedance matching, overheating or even arcing at the transmitting end of the magnetron in the microwave transmission system is avoided, and the service life of the magnetron is prolonged. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] With reference to the accompanying drawings, the disclosure of the present invention will become more readily understood. It is readily understood by those skilled in the art that these drawings are merely for illustrating the technical solutions of the present invention and are not intended to limit the protection scope of the present invention. In the figures: Figure 1 is a schematic structural diagram of a microwave digestion system; Figure 2 is a schematic flow chart of a sample processing method based on digestion technology according to the present invention.

[0015] In the drawings, 11 - magnetron, 12 - transmitting waveguide, 21 - circulator, 22 - water load, 31 - pin, 32 - stepper motor, 41 - coupling antenna, 42 - resonant cavity, 43 - sample, 44 - carrier liquid, 51 - temperature detection module. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0016] Figure 1 - Figure 2 The following description and illustrations describe alternative specific embodiments of the present invention to teach those skilled in the art how to implement and reproduce the present invention. To teach the technical solutions of the present invention, some conventional aspects have been simplified or omitted. Those skilled in the art should understand that variations or substitutions derived from these specific embodiments will fall within the scope of the present invention. Those skilled in the art should understand that the following features can be combined in various ways to form multiple variations of the present invention. Thus, the present invention is not limited to the following alternative specific embodiments but is defined only by the claims and their equivalents.

[0017] Example 1.

[0018] A sample processing method based on digestion technology in this embodiment includes a heating stage and an adjustment stage. In the heating stage, the water load 22 and the carrier liquid 44 and the sample 43 in the resonant cavity 42 are respectively heated by microwaves.

[0019] As Figure 2 shown, the adjustment stage includes the following steps: (A1) After heating for a time Δt, the temperature T of the carrier liquid 44 at the same moment is obtained 11 and the temperature T of the water load 22 21 .

[0020] (A2) According to the temperature T 11 and the temperature T 21 A is obtained.

[0021] A = 1 + 2D + 2·SQRT(D 2 + D), D = c2 m 2 (T 21 -T 20 ) / [c 1 m 1 (T 11 - T 10 )].

[0022] c 2 and c 1 are the specific heat capacities of the water load 22 and the liquid carrier 44 respectively, and m 2 and m 1 are the masses of the water load 22 and the liquid carrier 44 respectively, and T 20 and T 10 are the initial temperatures of the water load 22 and the liquid carrier 44 respectively.

[0023] (A3) Determine whether A is within the set range.

[0024] If the result is yes, the input impedance matches the load impedance in the resonator 42.

[0025] If the result is no, go to step (A4).

[0026] (A4) Adjust the position of the pin 31 and return to step (A1).

[0027] To improve the heating efficiency and stability, further, the heating stage is: As Figure 1 shown, the magnetron 11 outputs microwave energy through the transmitting waveguide 12, and then transmits it to the coupling antenna 41 through the waveguide. The coupling antenna 41 emits it into the resonator 42, and the microwave reflects back and forth in the resonator 42, thereby heating the liquid carrier 44 and the sample 43 (in the container) in the resonator 42.

[0028] The microwave returned from the resonator 42 to the waveguide enters the water load 22 through the circulator 21 to heat the water load 22.

[0029] To achieve impedance matching, further, the adjustment method is: Adjust the insertion depth of the pin 31 in step of ΔH until the obtained A is within the set range.

[0030] To obtain a better impedance matching effect, further, the adjustment method is: Adjust the insertion depth of the pin 31 in step of ΔH to obtain A corresponding to the insertion depth H i respectively, where i = 1, 2 ··· N, and N is an integer greater than 2. i

[0031] Adjust the insertion depth of the pin 31 to be the same as (Ai ) Insertion depth corresponding to min.

[0032] Example 2.

[0033] Application example of the sample processing method based on digestion technology in Example 1 of the present invention in the pretreatment of water samples.

[0034] In this application example, the sample processing method based on digestion technology includes a heating stage and an adjustment stage.

[0035] As Figure 1 shown, in the heating stage, a microwave digestion instrument is used, and the microwave energy output by the magnetron 11 is transmitted to the coupling antenna 41 through the transmitting waveguide 12, and is emitted into the resonant cavity 42 by the coupling antenna 41. The microwave reflects back and forth in the resonant cavity 42, thereby heating the carrier liquid 44 and the water sample 43 in the resonant cavity 42. The carrier liquid 44 is a mixed solution of 65% concentrated nitric acid and ultrapure water, with a mass of 155 g and a specific heat capacity of 2.56×10 3 J / (kg·℃).

[0036] The microwave returned from the resonant cavity 42 to the waveguide enters the water load 22 through the circulator 21, heating the water load 22. The mass of the water load 22 is 150 g and the specific heat capacity is 4.2×10 3 J / (kg·℃).

[0037] As Figure 2 shown, the adjustment stage includes the following steps: (A1) After heating for a time Δt = 300 s, the temperature detection module 51 obtains the temperature T of the carrier liquid 44 at the same moment 11 = 120 °C and the temperature T of the water load 22 21 = 30 °C.

[0038] (A2) Obtain A according to the temperature T 11 and the temperature T 21 .

[0039] A = 1 + 2D + 2·SQRT(D 2 + D) ≈ 2.18, D = c 2 m 2 (T 21 - T 20 ) / [c 1 m 1 (T 11 - T 10 )] = 0.1588.

[0040] c 2 and c 1 are the specific heat capacities of the water load 22 and the carrier liquid 44 respectively, m 2 and m1 are the masses of the water load 22 and the carrier liquid 44, respectively, T 20 , T 10 The initial temperatures of the water load 22 and the carrier liquid 44 are 20 °C, respectively.

[0041] (A3) Determine whether A is within the set range [1, 1.5].

[0042] If the result is yes, the input impedance is matched with the load impedance in the resonator 42, and the adjustment is completed.

[0043] If the result is no, go to step (A4).

[0044] (A4) The stepping motor 32 adjusts the insertion depth of the pin 31 by a step size of ΔH = 2 mm, thereby adjusting the position of the pin 31, and returns to step (A1).

[0045] Example 3.

[0046] An application example of the sample processing method based on the digestion technology in the pretreatment of heavy metal detection in the food field according to Embodiment 1 of the present invention is different from Embodiment 2 in that: Step (A4), adjust the insertion depth of the pin 31 by a step size of ΔH = 1 mm, traverse all the insertion depths of the pin 31, and respectively obtain A corresponding to the insertion depth H i corresponding i , i = 1, 2 ··· N, where N is an integer greater than 2, and the specific data are shown in the following table.

[0047] .

[0048] Finally, adjust the insertion depth of the pin 31 to the insertion depth H = 4 mm corresponding to (A i )min = 1.27, so as to obtain the best impedance matching effect.

Claims

1. A sample processing method based on digestion technology, comprising a heating stage and an adjustment stage, wherein in the heating stage, the water load and the carrier liquid and the sample in the resonant cavity are heated by microwaves respectively; characterized in that: The adjustment phase includes the following steps: (A1) After heating for a time Δt, the temperature T of the carrier liquid at the same time is obtained 11 and the temperature of the water load T 21 ; (A2) According to the temperature T 11 and temperature T 21 Get an A; A=1+2D+2·SQRT(D 2 +D),D=c2m2(T 21 -T 20 ) / [c1m1(T 11 - T 10 )]; c2 and c1 are the specific heat capacities of the water load and carrier fluid, respectively; m2 and m1 are the masses of the water load and carrier fluid, respectively; T 20 、T 10 are the initial temperatures of the water load and carrier fluid, respectively; (A3) Determine whether A is within the set range; If the result is yes, the input impedance matches the load impedance in the resonant cavity; If the answer is no, go to step (A4); (A4) Adjust the position of the pin and return to step (A1).

2. The sample processing method based on digestion technology according to claim 1, characterized in that: The heating stage is: The microwave energy output by the magnetron is transmitted to the coupling antenna through the waveguide, and then emitted into the resonant cavity by the coupling antenna. The microwave is reflected back and forth in the resonant cavity, thereby heating the carrier liquid and sample in the resonant cavity. The microwaves returning from the resonant cavity to the waveguide enter the water load through the circulator and heat the water load.

3. The sample processing method based on digestion technology according to claim 1, characterized in that: The range is set to [1,1.5].

4. The sample processing method based on digestion technology according to claim 3, characterized in that: The adjustment method is: The insertion depth of the pin is adjusted according to a step size ΔH until the obtained A is within the set range.

5. The sample processing method based on digestion technology according to claim 1, characterized in that: The adjustment method is: The insertion depth of the pin is adjusted according to the step length ΔH, and the insertion depth H is obtained respectively. i The corresponding A i , i=1,2···N, N is an integer greater than 2; Adjust the insertion depth of the pin to (A i )min corresponding insertion depth.

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