CN112444582B - Mass spectrometry method based on droplet extraction - Google Patents

Mass spectrometry method based on droplet extraction Download PDF

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CN112444582B
CN112444582B CN202110134059.XA CN202110134059A CN112444582B CN 112444582 B CN112444582 B CN 112444582B CN 202110134059 A CN202110134059 A CN 202110134059A CN 112444582 B CN112444582 B CN 112444582B
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liquid
capillary
capillary tube
bottom end
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CN112444582A (en
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闻路红
甘剑勤
刘云
余晓梅
陈安琪
洪欢欢
李文
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China Innovation Instrument Co ltd
Ningbo University
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Ningbo University
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    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
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Abstract

The invention provides a mass spectrometry method based on droplet extraction, which comprises the following steps: (A1) obtaining a mass spectrum signal output by a mass spectrometer as a background signal when no sample is fed; (A2) generating a single liquid drop and applying the single liquid drop on a sample to be detected; the sample to be detected is extracted by the single liquid drop; (A3) sampling an extraction substance of the sample to be detected; (A4) the sampled extract is ionized and sent to a mass spectrometer for analysis; (A5) removing the background signal from the mass spectrum signal output by the mass spectrometer to obtain a difference signal; if the intensity of the characteristic peak in the difference signal exceeds a threshold value, the mass spectrometer is injecting a sample and enters the step (A6); if the intensity of the characteristic peak in the difference signal does not exceed the threshold value, the mass spectrometer is not injected, and the step (A7) is carried out; (A6) analyzing the difference signal to identify a sample to be tested; (A7) the ionization is stopped. The invention has the advantages of high precision, high analysis efficiency and the like.

Description

Mass spectrometry method based on droplet extraction
Technical Field
The invention relates to cell analysis, in particular to a mass spectrometry method based on droplet extraction.
Background
Trace samples, including but not limited to single cells, tiny areas in tissue sections, planar deposits, etc., are of great interest for research into analytical chemistry itself. Analytical chemistry by itself has helped people recognize the mission of the micro world. From organ tissue imaging, to single cell imaging and even single molecule detection, samples for analytical chemistry research are getting smaller and smaller, the sensitivity of analytical methods is getting higher and higher, and people have more and more deep knowledge on the micro world. Therefore, the realization of analytical detection for smaller volume samples is a constant pursuit of analytical chemistry research.
The mass spectrum is a method for simultaneously analyzing multiple components, and can form spectral peaks arranged according to mass numbers in the mass spectrum according to different molecular weights of various components in cells, and further obtain molecular information of various components in the cells through multi-stage mass spectrum analysis. The mass spectrometry does not need to be marked and does not need to know the information of the molecules to be detected in advance, so that various unknown components in the sample can be rapidly identified, and the omics information of the protein and even the micromolecular metabolites can be obtained. In addition, the mass spectrum can easily obtain isotope information of each component molecule, and accurate quantification of various molecules to be detected can be realized by adopting isotope internal standards and dilution technology. Therefore, mass spectrometry trace sample analysis has recently received high attention and is considered to play an important role in single cell omics analysis research.
At present, the detection of the mass spectrum of the trace sample is manually operated, the efficiency is extremely low, the number of samples is large, the requirements of scientific research and application are difficult to meet, and a set of method capable of releasing both hands, improving the working efficiency and carrying out intelligent analysis is urgently needed.
Disclosure of Invention
In order to overcome the defects in the prior art, the invention provides the mass spectrometry method based on the liquid drop extraction, which has high analysis efficiency and high precision.
The purpose of the invention is realized by the following technical scheme:
a droplet extraction based mass spectrometry method, comprising the steps of:
(A1) obtaining a mass spectrum signal output by a mass spectrometer as a background signal when no sample is fed;
(A2) generating a single liquid drop and applying the single liquid drop on a sample to be detected; the sample to be detected is extracted by the single liquid drop;
(A3) sampling an extraction substance of the sample to be detected;
(A4) the sampled extract is ionized and sent to a mass spectrometer for analysis;
(A5) removing the background signal from the mass spectrum signal output by the mass spectrometer to obtain a difference signal;
if the intensity of the characteristic peak in the difference signal exceeds a threshold value, indicating that the mass spectrometer is injecting a sample, and entering the step (A6);
if the intensity of the characteristic peak in the difference signal does not exceed the threshold value, indicating that the mass spectrometer has no sample injection, and entering the step (A7);
(A6) analyzing the difference signal to identify a sample to be tested;
(A7) the ionization is stopped.
Compared with the prior art, the invention has the beneficial effects that:
1. the analysis precision and the analysis efficiency are high;
in order to adapt to the detection of a small volume of trace sample, a small volume of extraction liquid is required to cover the trace sample, so that the trace sample is extracted; based on the method, the generation of the single-droplet-picoliter extraction liquid is provided, the trace sample is effectively covered, but the excessive extraction liquid is not needed, the problem that the extraction substance is difficult to sample when the extraction liquid is excessive is solved, and the analysis precision and the sensitivity are correspondingly improved;
the small-volume extraction liquid is used for extracting trace samples, so that the extraction speed is improved, the extraction time is shortened, and the overall analysis efficiency is improved;
a method for deducting air interference in mass spectrum sample injection signals is established, the problem of mixing of mass spectrum signal peaks and air impurity peaks is solved, and the analysis precision is improved;
the method for identifying the molecular information of the specific detection sample is provided, the mass spectrum signal graph closest to the graph is obtained by using an optimization method, and key information such as a target sample, target molecules, difference mass spectrum signals and the like corresponding to a mass spectrum is obtained, so that the subsequent analysis is facilitated, and the analysis precision and the analysis efficiency are improved;
2. the analysis result is reliable;
before formal mass spectrum signals are obtained, whether the mass spectrometer is really sample-fed is firstly confirmed, so that the reliability of an analysis result is ensured;
3. the operation cost is low;
in the analysis process, before formalizing a mass spectrum signal, the sampling problem is found in time by confirming whether the sampling is real or not, so that the high pressure and the gas are closed in time, and the operation cost is reduced.
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The disclosure of the present invention will become more readily understood with reference to the accompanying drawings. As is readily understood by those skilled in the art: these drawings are only for illustrating the technical solutions of the present invention and are not intended to limit the scope of the present invention. In the figure:
FIG. 1 is a flow chart of a method of mass spectrometry based on droplet extraction according to an embodiment of the present invention.
Detailed Description
Fig. 1 and the following description depict alternative embodiments of the invention to teach those skilled in the art how to make and reproduce the invention. Some conventional aspects have been simplified or omitted for the purpose of explaining the technical solution of the present invention. Those skilled in the art will appreciate that variations or substitutions from these embodiments will be within the scope of the invention. Those skilled in the art will appreciate that the features described below can be combined in various ways to form multiple variations of the invention. Thus, the present invention is not limited to the following alternative embodiments, but is only limited by the claims and their equivalents.
Example 1:
fig. 1 is a flow chart of a mass spectrometry method based on droplet extraction according to an embodiment of the present invention, and as shown in fig. 1, the mass spectrometry method based on droplet extraction includes the following steps:
(A1) obtaining a mass spectrum signal output by a mass spectrometer as a background signal when no sample is fed;
(A2) generating a single liquid drop and applying the single liquid drop on a sample to be detected; the sample to be detected is extracted by the single liquid drop;
(A3) sampling an extraction substance of the sample to be detected;
(A4) the sampled extract is ionized and sent to a mass spectrometer for analysis;
(A5) removing the background signal from the mass spectrum signal output by the mass spectrometer to obtain a difference signal;
if the intensity of the characteristic peak in the difference signal exceeds a threshold value, indicating that the mass spectrometer is injecting a sample, and entering the step (A6);
if the intensity of the characteristic peak in the difference signal does not exceed the threshold value, indicating that the mass spectrometer has no sample injection, and entering the step (A7);
(A6) analyzing the difference signal to identify a sample to be tested;
(A7) the ionization is stopped.
In order to quickly and accurately identify the sample to be detected, further, in the step (a 6), the manner of identifying the sample to be detected is:
establishing a mapping relation between a mass spectrogram and different standard samples, wherein the different standard samples comprise different types and/or different contents;
searching a first mass spectrum in the mapping relation closest to the difference signal, and obtaining a difference mass spectrum signal between the difference signal and the first mass spectrum;
and obtaining first standard sample information corresponding to the first mass spectrogram according to the mapping relation.
In order to more accurately obtain the information of the sample to be detected, further searching a second mass spectrum in the mapping relation closest to the difference mass spectrum signal;
and obtaining second standard sample information corresponding to the second mass spectrogram according to the mapping relation.
In order to improve the mapping relationship, further, manually confirming the mapping relationship between the identified first standard sample information, second standard sample information and the difference mass spectrum signal;
if no error exists, supplementing the mapping relation;
and if the error exists, obtaining the information of the sample to be detected, establishing a corresponding relation between the difference signal and the information of the sample to be detected, and supplementing the corresponding relation into the mapping relation.
To generate a single droplet of accurate volume, further, in step (a 2), the single droplet is generated by:
(B1) obtaining an initial parameter of the capillary, the initial parameter comprising an angle of inclination of the capillary relative to the sample carrier;
(B2) obtaining a target parameter corresponding to the radius of the target liquid drop by utilizing a mapping relation, wherein the mapping relation is the corresponding relation between the radius of the liquid drop and the control parameter; the control parameters include an angle of inclination of the capillary relative to the sample carrier and a flow rate of the liquid within the capillary;
(B3) adjusting an initial parameter of the capillary to the target parameter;
(B4) the liquid at the bottom end of the capillary contacts the sample carrier, the liquid within the capillary flowing downward;
(B5) the bottom end of the capillary moves up to disengage the sample carrier, and a droplet is formed on the sample carrier and covers the sample to be measured.
To produce a single drop of accurate volume, further, the mapping relationship is:
Figure 523159DEST_PATH_IMAGE001
，
Figure 174720DEST_PATH_IMAGE002
the radius of the dropping liquid is the radius of the dropping liquid,
Figure 423299DEST_PATH_IMAGE003
is the slide coefficient of the sample carrier,
Figure 677563DEST_PATH_IMAGE004
in order to be a flow velocity coefficient,
Figure 226356DEST_PATH_IMAGE005
is the surface tension coefficient of the liquid,
Figure 783239DEST_PATH_IMAGE006
is the inner diameter of the bottom end of the capillary tube,
Figure 637888DEST_PATH_IMAGE007
is the density of the liquid in question,
Figure 305630DEST_PATH_IMAGE008
in order to be the acceleration of the gravity,
Figure 708930DEST_PATH_IMAGE009
is the internal diameter of the capillary at the internal liquid level,
Figure 561348DEST_PATH_IMAGE010
the distance from the liquid level to the bottom end of the capillary tube,
Figure 50098DEST_PATH_IMAGE011
is the pressure of the atmosphere,
Figure 255952DEST_PATH_IMAGE012
is the included angle between the central axis of the capillary tube and the generatrix of the inner surface,
Figure 638391DEST_PATH_IMAGE013
is the maximum value of the included angle between the generatrix and the liquid level in the capillary tube.
To ensure that a single droplet of accurate volume is generated, further, the droplet generation method further comprises the steps of:
(B6) detecting the liquid on the sample bearing member and judging whether the radius of the target liquid drop is met;
if not, return to step (B2).
In order to correct the deviation of the volume of the generated single droplet in time, further, when returning from step (B6) to step (B4), the mapping relationship is adjusted to:
Figure 537077DEST_PATH_IMAGE014
，
Figure 513124DEST_PATH_IMAGE015
is the radius of the liquid droplet and,
Figure 381722DEST_PATH_IMAGE016
，
Figure 759614DEST_PATH_IMAGE017
the internal diameter of the capillary at the internal initial level,
Figure 688256DEST_PATH_IMAGE018
is the distance between the initial liquid level in the capillary and the bottom end.
To generate a single droplet of accurate volume, further, in step (a 2), the single droplet is generated by:
(C1) establishing a mapping relation between the volume of a single liquid drop and parameters of a capillary tube, the gas pressure for pushing liquid in the capillary tube and the lifting speed of the capillary tube;
(C2) obtaining a target value of a control parameter corresponding to a target volume of liquid drop by using a mapping relation, wherein the control parameter comprises the gas pressure and the lifting speed;
(C3) adjusting the gas pressure to a target value of gas pressure;
(C4) the liquid at the bottom end of the capillary contacts the sample carrier, the liquid within the capillary flowing downward;
(C5) the bottom end of the capillary moves upwards to be separated from the sample bearing piece, the upward moving speed is a target value of the lifting speed, and the single liquid drop is formed on the sample bearing piece and covers the sample to be detected.
To produce a single drop of accurate volume, further, the mapping relationship is:
Figure 151598DEST_PATH_IMAGE019
v is the dropping volume, R is the inner diameter of the bottom end of the capillary tube,
Figure 964833DEST_PATH_IMAGE020
is the taper of the bottom end of the capillary tube,
Figure 197232DEST_PATH_IMAGE021
is the viscosity of the liquid and is,
Figure 827933DEST_PATH_IMAGE022
is the density of the liquid in question,
Figure 247413DEST_PATH_IMAGE023
in order to be the acceleration of the gravity,
Figure 864339DEST_PATH_IMAGE024
is the surface tension of the liquid in question,
Figure 75878DEST_PATH_IMAGE025
as the lifting speed of the capillary tube, is,
Figure 487268DEST_PATH_IMAGE026
the distance from the liquid level in the capillary tube to the bottom end of the capillary tube,
Figure 659623DEST_PATH_IMAGE027
is the gas pressure that pushes the liquid in the capillary,
Figure 939295DEST_PATH_IMAGE028
is the maximum value of the included angle between the generatrix of the inner surface of the capillary tube and the liquid level in the capillary tube.
Example 2:
an application example of the mass spectrometry method based on droplet extraction according to example 1 of the present invention in single cell analysis.
In this application example, the inner wall and the outer wall of the capillary tube are processed in the following way: soaking the capillary tube in 8% -12% NaOH solution and Piranha solution for 2-10 minutes respectively, then soaking the capillary tube in 18% -22% dichlorodimethylsilane ethanol solution for 1-2 hours, cleaning with clear water, then removing stress, and placing the capillary tube in an oven at 100-150 ℃ for baking for 30-60 minutes.
The cell carrier surface treatment method comprises the following steps:
uniformly mixing silica sol and a sulfonic group modified nano-silica solution according to a certain proportion (preferably 1: 16), coating the mixture on the surface of a cell carrier, and baking the cell carrier for 30 to 60 minutes in an oven at the temperature of 100 to 150 ℃; slide coefficient of cell carrier surface
Figure 146285DEST_PATH_IMAGE029
。
Obtaining initial parameters of the capillary by using a laser holographic detector, wherein the initial parameters comprise: inner diameter of capillary bottom
Figure 994155DEST_PATH_IMAGE030
Inner diameter of capillary at initial liquid level
Figure 512861DEST_PATH_IMAGE031
Distance between initial liquid level in capillary and bottom end of capillary
Figure 471590DEST_PATH_IMAGE032
The inclination angle of the capillary relative to the cell carrier;
the sensor uses a pressure sensor, and detects pressure to obtain the mass of the liquid drop, and converts the mass into the volume (radius) of the liquid drop, thereby judging whether the liquid drop meets the expectation (target liquid drop).
The mass spectrometry method based on the droplet extraction comprises the following steps:
(A1) obtaining a mass spectrum signal output by a mass spectrometer as a background signal when no sample introduction is carried out, namely no sample introduction is carried out but air introduction is carried out;
more than 10 groups of mass spectrum signals without sample injection are obtained, the peak height of each peak in each mass spectrum signal is obtained, each group of data is filtered, and the average value of the peak heights of the same mass-to-charge ratio in each mass spectrum signal is taken as a background signal;
(A2) generating single droplets and applying the single droplets to the single cells on the cell support; the sample to be detected is extracted by the single liquid drop;
(A3) sampling an extraction substance of the sample to be detected;
(A4) the sampled extract is ionized and sent to a mass spectrometer for analysis;
(A5) removing the background signal from the mass spectrum signal output by the mass spectrometer to obtain a difference signal;
if the intensity of the characteristic peak in the difference signal exceeds a threshold value, indicating that the mass spectrometer is injecting a sample, and entering the step (A6);
if the intensity of the characteristic peak in the difference signal does not exceed the threshold value, indicating that the mass spectrometer has no sample injection, and entering the step (A7);
(A6) analyzing the difference signal to identify a sample to be tested; the mode of identifying the sample to be detected is as follows:
establishing a mapping relation between the mass spectrogram and different standard samples, wherein the different standard samples comprise different types and/or different contents, such as different cells and different molecules;
searching a first mass spectrogram in the mapping relation closest to the difference signal by using an optimal algorithm, and obtaining a difference mass spectrum signal between the difference signal and the first mass spectrogram;
obtaining first standard sample information corresponding to the first mass spectrogram according to the mapping relation, wherein the first standard sample information comprises cell types and molecular information;
searching a second mass spectrum in the mapping relation closest to the difference mass spectrum signal by using an optimal algorithm;
obtaining second standard sample information corresponding to the second mass spectrogram according to the mapping relation, wherein the second standard sample information comprises cell types and molecular information;
manually confirming the corresponding relation between the identified first and second standard sample information and the difference signal, and the corresponding relation between the second standard sample information and the difference mass spectrum signal;
if no error exists, supplementing the mapping relation;
if the error exists, obtaining the information of the sample to be detected by using other analysis technologies, establishing a corresponding relation between the difference signal and the information of the sample to be detected, and supplementing the corresponding relation into the mapping relation;
(A7) stopping ionization;
in the above step (a 2), the manner of generating a single droplet includes the steps of:
(B1) obtaining initial parameters of the capillary tube using a holographic detector, the initial parameters comprising: inner diameter of capillary bottom
Figure 267508DEST_PATH_IMAGE033
Inner diameter of capillary at initial liquid level
Figure 286279DEST_PATH_IMAGE034
Distance between initial liquid level in capillary and bottom end of capillary
Figure 292281DEST_PATH_IMAGE035
The inclination angle of the capillary relative to the sample carrier is 48 degrees;
Figure 54701DEST_PATH_IMAGE036
is 3.6 degrees;
(B2) the following mapping relationship was used to obtain the target droplet radius (target droplet volume 300pL, diameter)
Figure 970704DEST_PATH_IMAGE037
) The corresponding target parameters are as follows: coefficient of flow velocity
Figure 19432DEST_PATH_IMAGE038
、
Figure 653676DEST_PATH_IMAGE039
Is 120 degrees;
Figure 954207DEST_PATH_IMAGE001
；
(B3) adjusting the initial parameter of the capillary to the target parameter, e.g. adjusting the tilt angle of the capillary relative to the sample carrierSo that
Figure 849351DEST_PATH_IMAGE039
Is 120 degrees; adjusting the driving force of the liquid in the capillary tube to make the flow rate coefficient
Figure 944346DEST_PATH_IMAGE040
；
(B4) Translating the capillary horizontally (capillary non-horizontally disposed) to a target area, then moving the capillary downward such that liquid at the bottom end of the capillary contacts the sample carrier, the liquid within the capillary flowing downward under external force drive (corresponding to a flow rate coefficient);
(B5) rotating the capillary tube and moving the capillary tube upward so that the bottom end of the capillary tube moves upward to be detached from the sample carrier, and a liquid drop is formed on the sample carrier and covers the sample-single cell to be detected;
in the steps (B4) and (B5), the inclination angle of the capillary with respect to the sample carrier is not changed during the horizontal translation and up and down movement of the capillary;
(B6) detecting the liquid on the sample bearing member by using a pressure sensor, and judging whether the radius of the target liquid drop is met;
if not, if the mass deviates from the target drop, returning to step (B2) until meeting expectations;
if yes, entering the next step;
in this application, the primary single drop is 319.172pL measured by the sensor, i.e.
Figure 65885DEST_PATH_IMAGE041
(ii) a The second single drop size was 322.264pL, diameter
Figure 170108DEST_PATH_IMAGE042
(ii) a The third single droplet size was 329.224pL, diameter
Figure 654179DEST_PATH_IMAGE043
(ii) a The deviation threshold was set to 20pL, and it was found that the first droplet satisfied the expectation, and the second and third did not satisfy the expectation, and the process had to return to step (B2), and the mapping was adjusted to:
Figure 185654DEST_PATH_IMAGE045
and adjusting parameters by utilizing the mapping relation to obtain target parameters: coefficient of flow velocity
Figure 528911DEST_PATH_IMAGE046
，
Figure 561458DEST_PATH_IMAGE047
Is 118 degrees;
the droplets obtained with the adjusted parameters were as follows: the fourth single droplet size is 302.247pL, the diameter
Figure 306560DEST_PATH_IMAGE048
(ii) a The fifth single drop size was 297.008pL, i.e.
Figure 743357DEST_PATH_IMAGE049
(ii) a The sixth single droplet size was 288.673pL, i.e.
Figure 698544DEST_PATH_IMAGE050
(ii) a The seventh single droplet size was 297.676pL, i.e.
Figure DEST_PATH_IMAGE051
(ii) a Obviously, these droplets are satisfactory.
Example 3:
the application example of the mass spectrometry method based on droplet extraction in the embodiment 1 of the present invention in single cell analysis is different from the application example 2 in that:
the manner in which the single droplets are generated is:
(C1) establishing a mapping relation between the volume of a single liquid drop and parameters of a capillary tube, the gas pressure for pushing liquid in the capillary tube and the lifting speed of the capillary tube:
Figure 878989DEST_PATH_IMAGE019
v is the dropping volume, R is the inner diameter of the bottom end of the capillary tube,
Figure 337653DEST_PATH_IMAGE020
is the taper of the bottom end of the capillary tube,
Figure 210931DEST_PATH_IMAGE021
is the viscosity of the liquid and is,
Figure 528780DEST_PATH_IMAGE022
is the density of the liquid in question,
Figure 512916DEST_PATH_IMAGE023
in order to be the acceleration of the gravity,
Figure 363104DEST_PATH_IMAGE024
is the surface tension of the liquid in question,
Figure 407283DEST_PATH_IMAGE025
as the lifting speed of the capillary tube, is,
Figure 946849DEST_PATH_IMAGE026
the distance from the liquid level in the capillary tube to the bottom end of the capillary tube,
Figure 859310DEST_PATH_IMAGE027
is the gas pressure that pushes the liquid in the capillary,
Figure 433511DEST_PATH_IMAGE028
is the maximum value of an included angle between a generatrix of the inner surface of the capillary tube and the liquid level in the capillary tube;
the capillary tube is made of borosilicate glass, one end of the capillary tube is opened and communicated with an air source, and the inner diameter of the bottom end of the capillary tube is 20 micrometers;
the pressure control unit is arranged between the capillary tube and the gas source and is used for adjusting the pressure of gas entering the capillary tube;
(C2) obtaining a target value of a control parameter corresponding to a target volume of 300pL of droplets using a mapping relation, the control parameter including the gas pressureP=500mbarLifting speedV tip =300um/s；
(C3) Adjusting the gas pressure to a target valueP=500mbar；
(C4) Translating the capillary horizontally (capillary non-horizontally disposed) to a target area, followed by moving the capillary downward such that liquid at the bottom end of the capillary contacts the sample carrier, the capillary bottom end contacting sample carrier (PDMS) to a depth of less than 100 μm;
the liquid in the capillary tube flows downwards under the driving of gas;
(C5) rotating the capillary tube and moving the capillary tube upwards to make the bottom end of the capillary tube move upwards to be separated from the sample bearing piece, wherein the upward moving speed is a lifting speed target valueV tip =500um/sAnd the picoliter single liquid drop is formed on the sample bearing member and covers the single cell to be detected.
Experimental results show that 313pL micro-droplets are finally formed on the sample bearing member, the volume deviation of the micro-droplets and the target droplets is 13pL, and the requirements of single-cell mass spectrum detection are completely met.
Example 4:
the application example of the mass spectrometry method based on droplet extraction in the embodiment 1 of the present invention in single cell analysis is different from the application example 2 in that:
the single droplet is generated in the following way:
(C1) establishing a mapping relation between the volume of a single liquid drop and parameters of a capillary tube, the gas pressure for pushing liquid in the capillary tube and the lifting speed of the capillary tube:
Figure 648591DEST_PATH_IMAGE019
v is the dropping volume, R is the inner diameter of the bottom end of the capillary tube,
Figure 675453DEST_PATH_IMAGE020
is the taper of the bottom end of the capillary tube,
Figure 126026DEST_PATH_IMAGE021
is the viscosity of the liquid and is,
Figure 554733DEST_PATH_IMAGE022
is the density of the liquid in question,
Figure 940715DEST_PATH_IMAGE023
in order to be the acceleration of the gravity,
Figure 845086DEST_PATH_IMAGE024
is the surface tension of the liquid in question,
Figure 709137DEST_PATH_IMAGE025
as the lifting speed of the capillary tube, is,
Figure 992351DEST_PATH_IMAGE026
the distance from the liquid level in the capillary tube to the bottom end of the capillary tube,
Figure 939447DEST_PATH_IMAGE027
is the gas pressure that pushes the liquid in the capillary,
Figure 940901DEST_PATH_IMAGE028
is the maximum value of an included angle between a generatrix of the inner surface of the capillary tube and the liquid level in the capillary tube;
the capillary tube is made of borosilicate glass, one end of the capillary tube is opened and communicated with an air source, and the inner diameter of the bottom end of the capillary tube is 15 micrometers;
the pressure control unit is arranged between the capillary tube and the gas source and is used for adjusting the pressure of gas entering the capillary tube;
(C2) obtaining a target value of a control parameter corresponding to a target volume of 300pL of droplets using a mapping relation, the control parameter including the gas pressureP=700mbarLifting speedV tip =500um/s；
(C3) Adjusting the gas pressure to a target valueP=700mbar；
(C4) Translating the capillary horizontally (capillary non-horizontally disposed) to a target area, followed by moving the capillary downward such that liquid at the bottom end of the capillary contacts the sample carrier, the capillary bottom end contacting sample carrier (PDMS) to a depth of less than 100 μm;
the liquid in the capillary tube flows downwards under the driving of gas;
(C5) rotating the capillary tube and moving the capillary tube upwards to make the bottom end of the capillary tube move upwards to be separated from the sample bearing piece, wherein the upward moving speed is a lifting speed target valueV tip =500um/sAnd the picoliter single liquid drop is formed on the sample bearing member and covers the single cell to be detected.
Experimental results show that 306pL micro-droplets are finally formed on the sample bearing member, the volume deviation of the micro-droplets and the target droplets is 6pL, and the requirements of single-cell mass spectrum detection are completely met.
Example 5:
the application example of the mass spectrometry method based on droplet extraction in the embodiment 1 of the present invention in single cell analysis is different from the application example 2 in that:
the single droplet is generated in the following way:
(C1) establishing a mapping relation between the volume of a single liquid drop and parameters of a capillary tube, the gas pressure for pushing liquid in the capillary tube and the lifting speed of the capillary tube:
Figure 874222DEST_PATH_IMAGE019
v is the dropping volume, R is the inner diameter of the bottom end of the capillary tube,
Figure 870997DEST_PATH_IMAGE020
is the taper of the bottom end of the capillary tube,
Figure 864361DEST_PATH_IMAGE021
is the viscosity of the liquid and is,
Figure 353111DEST_PATH_IMAGE022
is the density of the liquid in question,
Figure 683598DEST_PATH_IMAGE023
in order to be the acceleration of the gravity,
Figure 941404DEST_PATH_IMAGE024
is the surface tension of the liquid in question,
Figure 105669DEST_PATH_IMAGE025
as the lifting speed of the capillary tube, is,
Figure 816136DEST_PATH_IMAGE026
the distance from the liquid level in the capillary tube to the bottom end of the capillary tube,
Figure 215894DEST_PATH_IMAGE027
is the gas pressure that pushes the liquid in the capillary,
Figure 328206DEST_PATH_IMAGE028
is the maximum value of an included angle between a generatrix of the inner surface of the capillary tube and the liquid level in the capillary tube;
the capillary tube is made of borosilicate glass, one end of the capillary tube is opened and communicated with an air source, and the inner diameter of the bottom end of the capillary tube is 10 mu m;
the pressure control unit is arranged between the capillary tube and the gas source and is used for adjusting the pressure of gas entering the capillary tube;
(C2) obtaining a target value of a control parameter corresponding to a target volume of 300pL of droplets using a mapping relation, the control parameter including the gas pressureP=600mbarLifting speedV tip =400um/s；
(C3) Adjusting the gas pressure to a target valueP=600mbar；
(C4) Translating the capillary horizontally (capillary non-horizontally disposed) to a target area, followed by moving the capillary downward such that liquid at the bottom end of the capillary contacts the sample carrier, the capillary bottom end contacting sample carrier (PDMS) to a depth of less than 100 μm;
the liquid in the capillary tube flows downwards under the driving of gas;
(C5) rotating the capillary tube and moving the capillary tube upwards to make the bottom end of the capillary tube move upwards to be separated from the sample bearing piece, wherein the upward moving speed is a lifting speed target valueV tip =400um/sAnd the picoliter single liquid drop is formed on the sample bearing member and covers the single cell to be detected.
Experimental results show that 290pL of micro-droplets are finally formed on the sample bearing member, the volume deviation of the micro-droplets and the target droplets is 10pL, and the requirement of single-cell mass spectrum detection is completely met.
The above embodiment shows an example that the trace sample to be detected is a single cell, and may be other trace samples, such as a micro region in a tissue slice, a planar deposited substance, and the like, and the specific analysis method is the same as the above embodiment.

Claims (7)

1. A droplet extraction based mass spectrometry method, comprising the steps of:
(A1) obtaining a mass spectrum signal output by a mass spectrometer as a background signal when no sample is fed;
(A2) generating a single liquid drop and applying the single liquid drop on a sample to be detected; the sample to be detected is extracted by the single liquid drop;
(A3) sampling an extraction substance of the sample to be detected;
(A4) the sampled extract is ionized and sent to a mass spectrometer for analysis;
(A5) removing the background signal from the mass spectrum signal output by the mass spectrometer to obtain a difference signal;
if the intensity of the characteristic peak in the difference signal exceeds a threshold value, indicating that the mass spectrometer is injecting a sample, and entering the step (A6);
if the intensity of the characteristic peak in the difference signal does not exceed the threshold value, indicating that the mass spectrometer has no sample injection, and entering the step (A7);
(A6) analyzing the difference signal to identify a sample to be tested; the mode of identifying the sample to be detected is as follows:
establishing a mapping relation between a mass spectrogram and different standard samples, wherein the different standard samples comprise different types and/or different contents;
searching a first mass spectrum in the mapping relation closest to the difference signal, and obtaining a difference mass spectrum signal between the difference signal and the first mass spectrum;
obtaining first standard sample information corresponding to the first mass spectrogram according to the mapping relation;
finding a second mass spectrum in the mapping relationship closest to the difference mass spectrum signal;
obtaining second standard sample information corresponding to the second mass spectrogram according to the mapping relation;
manually confirming the corresponding relationship between the identified first standard sample information and second standard sample information and the difference signal, and the corresponding relationship between the second standard sample information and the difference mass spectrum signal;
if no error exists, supplementing the mapping relation;
if the error exists, obtaining the information of the sample to be detected, establishing a corresponding relation between the difference signal and the information of the sample to be detected, and supplementing the corresponding relation into the mapping relation;
(A7) the ionization is stopped.
2. The method of droplet extraction based mass spectrometry of claim 1, wherein in step (a 2), the single droplets are generated by:
(B1) obtaining an initial parameter of the capillary, the initial parameter comprising an angle of inclination of the capillary relative to the sample carrier;
(B2) obtaining a target parameter corresponding to the radius of the target liquid drop by utilizing a mapping relation, wherein the mapping relation is the corresponding relation between the radius of the liquid drop and the control parameter; the control parameters include an angle of inclination of the capillary relative to the sample carrier and a flow rate of the liquid within the capillary;
(B3) adjusting an initial parameter of the capillary to the target parameter;
(B4) the liquid at the bottom end of the capillary contacts the sample carrier, the liquid within the capillary flowing downward;
(B5) the bottom end of the capillary moves up to disengage the sample carrier, and a droplet is formed on the sample carrier and covers the sample to be measured.
3. The method of droplet extraction based mass spectrometry of claim 2, wherein the mapping relationship is:
Figure 464108DEST_PATH_IMAGE001
r is the dropping radius, k1Is the slide coefficient, k, of the sample carrier2Is the flow rate coefficient, is the surface tension coefficient of the liquid, r0Is the inner diameter of the bottom end of the capillary tube,
Figure 912407DEST_PATH_IMAGE002
is the density of the liquid, g is the acceleration of gravity, r is the internal diameter of the capillary at the internal liquid level, h is the distance from the liquid level to the bottom end of the capillary, p0Is the pressure of the atmosphere,
Figure 426565DEST_PATH_IMAGE003
is the included angle between the central axis of the capillary tube and the generatrix of the inner surface,
Figure 228298DEST_PATH_IMAGE004
is the maximum value of the included angle between the generatrix and the liquid level in the capillary tube.
4. The method of droplet extraction based mass spectrometry of claim 3, wherein the means for generating single droplets further comprises the steps of:
(B6) detecting the liquid on the sample bearing member and judging whether the radius of the target liquid drop is met;
if not, return to step (B2).
5. The method of droplet extraction based mass spectrometry of claim 4, wherein the mapping relationship is adjusted from step (B6) back to step (B2) as:
Figure DEST_PATH_IMAGE006AAA
，
Figure 26359DEST_PATH_IMAGE007
is the radius of the liquid droplet and,
Figure 583242DEST_PATH_IMAGE008
，
Figure 256800DEST_PATH_IMAGE009
the internal diameter of the capillary at the internal initial level,
Figure 252438DEST_PATH_IMAGE010
is the distance between the initial liquid level in the capillary and the bottom end.
6. The method of droplet extraction based mass spectrometry of claim 1, wherein in step (a 2), the single droplets are generated by:
(C1) establishing a mapping relation between the volume of a single liquid drop and parameters of a capillary tube, the gas pressure for pushing liquid in the capillary tube and the lifting speed of the capillary tube;
(C2) obtaining a target value of a control parameter corresponding to a target volume of liquid drop by using a mapping relation, wherein the control parameter comprises the gas pressure and the lifting speed;
(C3) adjusting the gas pressure to a target value of gas pressure;
(C4) the liquid at the bottom end of the capillary contacts the sample carrier, the liquid within the capillary flowing downward;
(C5) the bottom end of the capillary moves upwards to be separated from the sample bearing piece, the upward moving speed is a target value of the lifting speed, and the single liquid drop is formed on the sample bearing piece and covers the sample to be detected.
7. The method of droplet extraction based mass spectrometry of claim 6, wherein the mapping relationship is:
Figure 75644DEST_PATH_IMAGE011
v is the drop volume, R is the inner diameter of the bottom end of the capillary tube,
Figure 803429DEST_PATH_IMAGE012
is the taper of the bottom end of the capillary tube,
Figure 88917DEST_PATH_IMAGE013
is the viscosity of the liquid and is,
Figure 498032DEST_PATH_IMAGE014
is the density of the liquid, g is the acceleration of gravity,
Figure 552576DEST_PATH_IMAGE015
is the surface tension of the liquid in question,
Figure 716841DEST_PATH_IMAGE016
h is the distance from the liquid level in the capillary tube to the bottom end of the capillary tube, P is the gas pressure for pushing the liquid in the capillary tube,
Figure 614259DEST_PATH_IMAGE017
is the maximum value of the included angle between the generatrix of the inner surface of the capillary tube and the liquid level in the capillary tube.
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