CN105758930A - Gas heat assisting surface desorption normal-pressure chemical ionization source and mass spectrometry method - Google Patents
Gas heat assisting surface desorption normal-pressure chemical ionization source and mass spectrometry method Download PDFInfo
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- H—ELECTRICITY
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- G01N27/68—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating the ionisation of gases, e.g. aerosols; by investigating electric discharges, e.g. emission of cathode using electric discharge to ionise a gas
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Abstract
The invention provides a gas heat assisting surface desorption normal-pressure chemical ionization source and a mass spectrometry method.The ionization source comprises a heat part, a body part and a tail part which are sequentially connected.A communicated closed cavity is formed in the ionization source.The head part and the tail pat are each provided with a through hole communicated with the cavity.A discharge needle is put in the cavity, and the point of the needle extends out of the head part through the through hole of the head part and faces towards the surface of a sample on a sample plate.The tail part is connected with an assisting gas channel which introduces assisting gas into the cavity through the through hole of the tail part.By arranging a pipeline connector and an assisting agent connector, selected assisting gas and assisting reagent can be conveniently and reliably introduced; due to a built-in heating wire, assisting gas in the closed cavity can be heated, assisting reagent is atomized by heated assisting gas and ionized into high-energy and high-density primary ions in a brush discharge area of the discharge needle, the reaction activity of target sample molecules is enhanced, and analysis sensitivity is improved.
Description
Technical field
The invention belongs to analytical chemistry field, be specifically related to a kind of by introducing assist gas and auxiliary reagent to improve sample molecule desorbing, to strengthen the gas hot auxiliary surface desorption atmospheric chemical ionization source of molecular ion reactivity and adopt the mass spectrometric analysis method of this ionization source.
Background technology
Analytical technique of mass spectrum is mass-to-charge ratio and signal response intensity and then the method determining determinand structure and content of detecting through mass spectrograph after testing sample ionizing.Due to advantages such as mass-spectrometric technique are highly sensitive, it is fast to analyze speed, consumption sample amount is few, and it is widely used in the fields such as petrochemical industry, food and drug safety, public safety, metabolism group, geological sciences.
Ionization source, as one very important part of mass spectrograph, is mainly used in by molecular conformation, test substance is converted into ionic forms, is thought the heart of mass spectrometer by mass spectrum great master professor R.G.Cooks.nullMass-spectrometric technique traditional in mass spectrum evolution includes: inductivity coupled plasma mass spectrometry (Inducedcoupledplasmamassspectrometry,ICP-MS)，Chemi-ionization technology (ChemicalIonizationSource,CI)，Desorption ionization techniques (DesorptionIonSource,DI)，Electron impact ionization technology (ElectronImpactIonSource,EI)，Spraying ionization technique (SprayIonization,SI)，And later based on this electron spray ionisation technology (ESI) grown up、Substance assistant laser desorpted ionized (MALDI) and atmospheric chemical ionization technology (APCI) etc..In high flux, the lossless and analysis process of reaction monitoring, these atmospheric ionization sources have been used to the various compound analysis analyzed from little molecule to macromolecular substances.
Surface desorption atmospheric chemical ionization mass spectrum method (DAPCI-MS) is that one does not need or only needs little sample pretreatment, and the determinand in complex sample can directly carry out the quick mass spectrometric analysis method of selective chemical ionization and detection.The various fields such as food quality detection, pharmaceutical analysis, explosive detection, forest-science, medical test and handwriting verification have been arrived in DAPCI-MS successful application.The mass spectrograph of the surface desorption atmospheric chemical ionization source (DAPCI) LTQ-XL linear ion trap mass spectrometer and other companies through matching Mo Feishier company with the U.S. couples coupling and all obtains good test result, and has carried out substantial amounts of applied research.But, the introduction of method of above-mentioned standard surface desorption atmospheric chemical ionization source assist gas in actual use and auxiliary reagent is loaded down with trivial details, regulative mode bothers, and assist gas can not be directly heated, directly analyzed area can not be heated, have impact on the rapidity of sample analysis, susceptiveness and effectiveness.
Summary of the invention
In order to solve the problems referred to above, the present invention provides a kind of can strengthen that desorbing and ionizing power, analysis speed is fast, simple in construction, easy to operate gas hot auxiliary surface desorption atmospheric chemical ionization source.
The above-mentioned purpose of the present invention is realized by techniques below scheme:
A kind of gas hot auxiliary surface desorption atmospheric chemical ionization source, including the head being sequentially connected with, main part and afterbody, it is internally formed the airtight chamber of connection, head and afterbody are communicated with the through hole of chamber respectively, one spray point is placed in described chamber and its needle point through hole extended tips by head, and towards the sample surfaces on specimen disc；Afterbody connects assist gas passage, and assist gas passage introduces assist gas through the through hole of afterbody in described chamber.
In above-mentioned gas hot auxiliary surface desorption atmospheric chemical ionization source, described head sets the structure of the cavity with described chamber in being, described structure side is provided with auxiliary reagent interface, and described interface connects with cavity, connects the microsyringe for introducing auxiliary reagent by pipeline.
In above-mentioned gas hot auxiliary surface desorption atmospheric chemical ionization source, described head side wall being relatively set with two countersunk head screwed holes (32,33), two bolts are screwed into described countersunk screw holes respectively, and afterbody is relative；Described spray point one end is by described two bolt clampings, and the other end stretches out through the through hole (34) of head from the end of described head；The head of bolt is provided with the high voltage power supply joint for connecting the high voltage power supply being applied to spray point.
In above-mentioned gas hot auxiliary surface desorption atmospheric chemical ionization source, the structure that described head is the cylinder being relatively large in diameter and the less cone of diameter is formed, the through hole (34) of head extends to the cone tip part of cone, and described spray point stretches out from described cone tip part；Described cylindrical sidewall is provided with the temperature thermocouple interface for connecting thermocouple.
In above-mentioned gas hot auxiliary surface desorption atmospheric chemical ionization source, described main part includes shell, thermal insulation layer, pushing out ring and heater strip, shell is cylinder shell, enclosure interior installs a pushing out ring, thermal insulation layer and heater strip from outside to inside successively, the both ends of shell are respectively provided with tapped through hole (112), respectively being provided with the first fixing bolt and the second fixing bolt in described tapped through hole (112), two bolts grip heater strip；The one end of the first fixing bolt and the second fixing bolt is respectively provided with the low-tension supply joint for connecting the low-tension supply being applied to heater strip.
In above-mentioned gas hot auxiliary surface desorption atmospheric chemical ionization source, described thermal insulation layer has three layers, is followed successively by fiberglass pipe from outside to inside, has the aluminum foil pipe of asbestos interlayer and high temperature resistant quartz ampoule.
Above-mentioned gas hot auxiliary surface desorption atmospheric chemical ionization source also includes a temperature controller, and it is connected in the circuit loop at heater strip place, and electrically connects with the thermocouple being connected to temperature thermocouple interface.
In above-mentioned gas hot auxiliary surface desorption atmospheric chemical ionization source, described afterbody includes tail-hood and pipe joint, tail-hood is the cylinder that the outer sheath diameters with described main part matches, being provided with the screwed hole (211) for connecting line joint in the middle part of it, the bottom of this screwed hole is provided with the through hole (212) being connected with described chamber；Pipe joint is the stud that middle part is provided with through hole, and one end is connected to the screwed hole (211) of tail-hood, and the other end connects assist gas passage and introduces assist gas, and the through hole of pipe joint connects with the through hole (212) of tail-hood.
A kind of hot auxiliary surface desorption atmospheric chemical ionization mass spectrometric apparatus of gas, including ionization source, the specimen disc being placed with sample and mass spectrograph, described ionization source is placed on the side of specimen disc at an angle, the spray point of ionization source is towards sample surfaces, and the needle point of spray point and solid sample have certain horizontal range；The mass spectrometric transfer tube mouth of pipe is placed on the opposite side of specimen disc at an angle, has certain horizontal range with solid sample, and described ionization source is above-mentioned gas hot auxiliary surface desorption atmospheric chemical ionization source.
The present invention also provides for a kind of hot auxiliary surface desorption atmospheric chemical ionization mass spectrum method of gas, and the method utilizes above-mentioned gas hot auxiliary surface desorption atmospheric chemical ionization source to coordinate scanning of the mass spectrum instrument to carry out mass spectral analysis, comprises the following steps:
(1) assist gas passage is connected on the pipe joint of afterbody, microsyringe is connected to the auxiliary reagent seam of head, the temperature controlling value of temperature controller is arranged design temperature, and sets mass spectrograph.
(2) pass into selected assist gas from pipe joint, and the low-tension supply connecting heater strip is heated, after the temperature of the assist gas within described ionization source arrives the temperature set, pass into selected auxiliary reagent from auxiliary reagent seam.
(3) auxiliary reagent is atomized by the assist gas of high temperature, and under high temperature gas flow drives, the auxiliary reagent of atomization is ionized as primary ion in the needle-tip corona region of discharge of spray point.
(4) high-temperature gas carrying primary ion brushes sample surfaces, target molecule is being heated and is desorbing from sample matrices under the shock of primary ion, being shifted by ionic reaction or energy charge, target molecule is ionized, and enters in mass spectrograph and be analyzed.
(5) regulate the position relationship between specimen disc and ion source, mass spectrograph, make mass spectrometric signal intensity reach maximum, obtain mass spectrometric data.
The present invention adopts technique scheme, obtains techniques below effect: (1), by arranging pipe joint and auxiliary reagent interface, introduces assist gas and auxiliary reagent easily and reliably；Assist gas in airtight chamber can be heated by built-in heater strip, auxiliary reagent is atomized by the assist gas after heating, and be ionized in the corona discharge region of spray point there is high-energy, highdensity primary ion, enhance the reactivity of target sample molecule；(2) in conjunction with the characteristic of sample and target sample molecule, by selecting different auxiliary reagents, it is possible to increase the desorption performance of target sample molecule and rate of ionization, and then the sensitivity analyzed is improved.
Accompanying drawing explanation
Fig. 1 is perspective view and the front view thereof in the gas hot auxiliary surface desorption atmospheric chemical ionization source that the embodiment of the present invention provides；
Fig. 2 is front view and the left view of the shell of main part；
Fig. 3 be afterbody axonometric chart and along line A-A intercept sectional view；
Fig. 4 is the axonometric chart of head；
Fig. 5 is the sectional view that line B-B intercepts along Fig. 4；
Fig. 6 is that line C-C intercepts to obtain sectional view along Fig. 1；
Fig. 7 is the operation principle schematic diagram of the hot auxiliary surface desorption atmospheric chemical ionization mass spectrum method of gas；
The primary ion mass spectrum that Fig. 8 produces when being the use difference auxiliary reagent adopting apparatus of the present invention and method to measure；
Fig. 9 is the mass spectrum of the tripolycyanamide milk soln adopting apparatus of the present invention and method to measure；
Figure 10 is the working curve of milk intermediate ion concentration and the melamine concentration adopting apparatus of the present invention and method to measure；
Figure 11 is the mass spectrum of the isoniazid tablet adopting apparatus of the present invention and method to measure；
Figure 12 is that protonation isoniazid is at heating and the variation trends figure under not heating condition.
In figure, accompanying drawing labelling is expressed as:
1: main part；11: shell, 111: strip flat bottomed recess, 112: tapped through hole, 113: screwed hole；12: thermal insulation layer；13: a pushing out ring；14: heater strip；
2: afterbody, 21: tail-hood, 211: screwed hole, 212: through hole, 213: countersunk head screwed hole；22: pipe joint；
3: head, 31: cavity, 32/33: countersunk head screwed hole, 34: through hole, 35: auxiliary reagent interface, 36: temperature thermocouple interface；
4: the first fixing bolts, 41: low-tension supply joint；
5: the second fixing bolts, 51: low-tension supply joint；
6: the three fixing bolts, 61: high voltage power supply joint；
7: spray point；
8: temperature controller；
9: mass spectrograph.
100: microsyringe；101: thermocouple；102: gas cylinder, 103: specimen disc.
Detailed description of the invention
Surface desorption atmospheric chemical ionization source (DAPCI) is a kind of not need sample pretreatment, have good chemical selectivity, highly sensitive novel ionization source, its adopt corona discharge produce primary ion and with solid or fluid sample surface action, there is desorption ionization, thus obtaining the ion of sample surfaces determinand.DAPCI works at ambient pressure, and different reagent or sample can be replaced easily at ambient pressure, are suitable for high throughput analysis.
The introduction of method of existing standard surface desorption atmospheric chemical ionization source assist gas in actual use and auxiliary reagent is loaded down with trivial details, regulative mode bothers, assist gas can not be heated, and directly analyzed area can not be heated, have impact on that this technology is quick, sensitive and effective to be analyzed sample.Therefore, the present invention proposes a kind of can introduce assist gas and reagent, the gas hot auxiliary surface desorption atmospheric chemical ionization source that can directly heat assist gas and reagent and mass spectrometric analysis method easily.
Below in conjunction with the drawings and specific embodiments, gas hot auxiliary surface desorption atmospheric chemical ionization source and mass spectrometric analysis method to the present invention are described in detail, the parts of 26S Proteasome Structure and Function identical in figure mark with identical accompanying drawing labelling, accompanying drawing is only intended to help explain the present invention, it is not offered as limiting the scope of the invention, accompanying drawing is only for illustrating simultaneously, is not drawn to scale.
Referring to Fig. 1, for the gas hot auxiliary surface desorption atmospheric chemical ionization source that the embodiment of the present invention provides, including the head 3 being sequentially connected with from right to left, main part 1 and afterbody 2, it is internally formed the airtight chamber of connection, head 3 is respectively provided with, with in the middle part of afterbody 2, the through hole connecting chamber, one spray point 7 is placed in internal chamber and the needle point through hole extended tips 3 by head 3, and towards the sample surfaces (referring to Fig. 7) on specimen disc 103；Afterbody 2 connects assist gas passage, and this assist gas passage can be produced by gas cylinder 102 (referring to Fig. 7), and this assist gas passage introduces assist gas by the through hole of afterbody 2 in chamber, wherein:
Referring to Fig. 1, Fig. 2 and Fig. 6, main part 1 includes shell 11, thermal insulation layer 12, pushing out ring 13 and heater strip 14, shell 11 is cylinder shell, top offers strip flat bottomed recess 111, the two ends of bottom portion of groove are provided with tapped through hole 112, this through hole is connected with the counter sink of respective side, for connecting the first fixing bolt 4 and the second fixing bolt 5 respectively；Referring to the left view on right side in Fig. 2, the both ends of the surface of the barrel of shell 11 separate and is provided with screwed hole 113, be used for connecting head 3 and afterbody 2.
As shown in Figure 6, a pushing out ring 13 (such as aluminum annulus) is placed in the internal diameter of the inside of shell 11, its external diameter and shell 11 and matches, and is used for fixing thermal insulation layer 12；Thermal insulation layer 12 is set in a pushing out ring 13, and it is combined by three-decker, and internal layer is high temperature resistant quartz ampoule；Middle level is the aluminum foil pipe with asbestos interlayer, has heat insulation and insulation effect；Outer layer is fiberglass pipe, for isolation heat protection ionization source shell 11 further.Heater strip 14 can be diameter nichrome wire between 0.25mm-0.35mm, makes in the quartz ampoule that helical form is placed in thermal insulation layer 12.First fixing bolt 4 and the second fixing bolt 5 are installed in the two ends tapped through hole 112 of shell 11, and grip heater strip 14, the two ends of heater strip 14 are stretched out the quartz ampoule of thermal insulation layer 12 and reserve certain length, facilitate the first fixing bolt 4 and the second fixing bolt 5 to grip heater strip 14；First fixing bolt 4 and the second fixing bolt 5 are positioned at the two ends of strip flat bottomed recess 111, are respectively provided with low-tension supply joint 41 and 51, are used for connecting low-tension supply, make heater strip 14 electrified regulation.
As shown in Figure 3 and Figure 6, afterbody 2 includes tail-hood 21 and pipe joint 22, tail-hood 21 is the cylinder matched with shell 11 overall diameter, the middle part of tail-hood 21 is provided with screwed hole 211, for connecting line joint 22, the bottom center of this screwed hole is provided with through hole 212, the chamber of this through hole and main part 1；The outer face of tail-hood 21 separates countersunk head screwed hole 213 is set, for connecting the shell 11 of main part 1.Pipe joint 22 is provided with the stud of through hole for middle part, and one end is connected to the screwed hole 211 of tail-hood 21, and the other end is used for connecting assist gas passage (such as, gas cylinder 102) and introduces assist gas, and assist gas is generally nitrogen or noble gas.
Referring to Fig. 4 and Fig. 5, head 3 is the structure formed by the cone that the cylinder being relatively large in diameter and diameter are less, this construction inner is provided with the cavity 31 that the cavity with main part 1 and tail-hood 2 is connected, this cavity is away from the one end open of cone, offering a through hole 34 in the middle part of the other end, this through hole extends to the cone tip part of cone；The cylindrical circumference side of this structure is provided with the countersunk head screwed hole 32 being connected relatively, for connecting the 3rd fixing bolt 6, two bolts are screwed into the countersunk head screwed hole 32 of both sides respectively, afterbody forms the 3rd fixing bolt 6 relatively, one metal discharge pin 7 one end is clamped by two bolts, the other end leans out through through hole 34 from cone tip part, general 50 μm of the tip diameter of spray point 7；Two bolt heads are respectively equipped with high voltage power supply joint 61, are used for connecting high-voltage power supply, thus spray point 7 is applied ionization voltage；On rear side of the cylindrical periphery of head 3, (referring to Fig. 4) is provided with auxiliary reagent interface 35, this interface connects microsyringe 100 (referring to Fig. 7) by pipeline, for introducing auxiliary reagent, can selecting according to different testing goals and ionize auxiliary reagent accordingly, conventional auxiliary reagent has water, methanol, acetone, acetic acid etc.；It is provided with temperature thermocouple interface 36 on front side of the cylinder periphery of head 3, for connecting temperature thermocouple 101 (referring to Fig. 7), thus measuring the heating-up temperature of assist gas, this temperature thermocouple can use K type thermocouple, and its maximum measured temperature is 600 DEG C；Near the side of cone, separation is provided with countersunk head screwed hole 33 to the cylinder of head 3, for connecting the shell 11 of main part 1.
Referring to Fig. 7, temperature controller 8 is connected in the electric loop at heater strip 14 place, and electrically connect with the thermocouple being connected to temperature thermocouple interface, temperature controller 8 arranges predetermined heating-up temperature, compared with the temperature value preset by the temperature value of thermocouple measurement, control the break-make of low-tension supply, thus controlling the heat time heating time of heater strip 14, it is ensured that gas temperature fluctuation is for ± 1 DEG C.
The gas hot auxiliary surface desorption atmospheric chemical ionization source that above-mentioned each parts are invented according to the connections above relation assembly cost, wherein, the structure of shell 11, tail-hood 21 and head 3 all adopts resistant to elevated temperatures Peek material to make, each parts junction all uses the O that nitrile rubber is made to carry out compressing sealing, it is to avoid internal gas leakage during the work of this ionization source.
During the work of above-mentioned ionization source, the heated silk 14 of assist gas quickly heats, the trace auxiliary reagent atomization that then will be introduced by auxiliary reagent interface 35, and in atomization process, auxiliary reagent molecular kinetic energy and interior can all be increased；Assist gas carries the needle point of the auxiliary reagent arrival spray point 7 of atomization, in spray point corona region, the interior reagent molecule reactivity that can increase increases, therefore more easily ionizable produce high density precursor reagent ion, and Contrast agent molecular reaction is active and in conjunction with corona discharge, have also been enlarged the range of choice of auxiliary reagent.Desorption under high temperature gas is when blowing over solid sample surface, and heat transmission contributes to the desorbing of volatilization or half volatile target molecule, and specific precursor reagent ion also is able to target molecule is carried out selectivity desorbing.It addition, sample substrate weakens with the binding ability of target molecule after being heated, it is also beneficial to obtain more target molecule；Target molecule obtains energy in desorption process and causes that reactivity increases, and during with the precursor reagent contacted with ions of kinetic energy increase, strong collision makes energy charge transfer be more easy to generation, thus improves the Ionization Efficiency of target molecule.Further, for structural unstable sample molecule, when molecular ion reaction occurs, instantaneous high intensity collision and the transfer of substantial amounts of energy make it possible to sample molecule cracking, and then obtain its patch information.
The gas hot auxiliary surface desorption atmospheric chemical ionization source of the present invention coordinates mass spectrograph 100 to use, as shown in Figure 7, ionization source is the side that α angle is placed on specimen disc 103, the spray point 7 of this ionization source is towards solid sample surface, and the horizontal range of the sample on the needle point of spray point 7 and specimen disc 103 is sized to a；The transfer tube mouth of pipe 3 of mass spectrograph 100 is placed on the opposite side of specimen disc 103 in β angle, is sized to b with the horizontal range of sample.The precursor reagent ion that this ionization source produces brushes solid sample surface under the carrying of high temperature assist gas, precursor reagent ion is by the target molecule ionizing of desorbing, object ion enters in mass spectrograph 100 and is analyzed mass spectral analysis, in detection process, specimen disc 103 and ion source can be regulated, position relationship (i.e. placed angle α between the needle point of described ionization source spray point 7 and the transfer tube mouth of pipe of mass spectrograph 100 and specimen disc 103 between mass spectrograph 100, β and horizontal range a, the size of b), the signal intensity making mass spectrograph 100 reaches maximum, this ionization mass spectrometry method is called the hot auxiliary surface desorption atmospheric chemical ionization mass spectrum method of gas.Specifically, the method comprises the following steps:
(1) assist gas passage is connected on the pipe joint 22 of afterbody 2, microsyringe 100 is connected to auxiliary reagent interface 35 place of head 3, the temperature controlling value of temperature controller 8 is arranged design temperature, and sets mass spectrograph 100.
(2) pass into selected assist gas from pipe joint 22, and the power supply connecting heater strip 14 is heated, after the temperature of the assist gas within described ionization source arrives the temperature set, auxiliary reagent interface 35 pass into selected auxiliary reagent.
(3) auxiliary reagent is atomized by the assist gas of high temperature, and under high temperature gas flow drives, the auxiliary reagent of atomization is ionized as primary ion in the needle-tip corona region of discharge of spray point 7.
(4) high-temperature gas carrying primary ion brushes sample surfaces, target molecule is being heated and is desorbing from sample matrices under the shock of primary ion, being shifted by ionic reaction or energy charge, target molecule is ionized, and enters in mass spectrograph 100 and be analyzed.
(5) position relationship between specimen disc 103 and ion source, mass spectrograph 100 (i.e. the size of placed angle α, β between the needle point of described ionization source spray point 7 and the transfer tube mouth of pipe of mass spectrograph 100 and specimen disc 103 and horizontal range a, b) is regulated, the signal intensity making mass spectrograph 100 reaches maximum, obtains mass spectrometric data.
Test case 1:
Usual high reaction activity, kind single and highdensity primary ion degree testing result ratio is advantageous, now with nitrogen as assist gas, using water, methanol, acetone and acetic acid as auxiliary reagent, assist gas being heated to 80 DEG C, the primary ion situation of generation is as shown in Figure 8.
(1) deionized water: shown in the figure (a) in Fig. 8, inside ion source, deionized water is injected by sentencing the speed of 3 μ L/min at the auxiliary reagent interface 35 of the ion source head 3 of the present invention, in the corona discharging area of spray point 7, existence due to assist gas nitrogen atmosphere, the material being mainly ionized is the water vapour entrained by assist gas, mainly obtain m/z36,37,55, the ion of the water of 73 and 91, wherein m/z36 is the radical cation of water, and all the other are all the cluster ions of water, are followed successively by: (H2O)H3O+,(H2O)2H3O+,(H2O)3H3O+(H2O)4H3O+。
(2) methanol/water: shown in the figure (b) in Fig. 8, using volume ratio be 1:1 methanol/water mixed solution as auxiliary reagent, m/z33 is the protonation signal [CH of methanol3OH+H]+, and m/z65 diplontic the ion signal [(CH that is methanol3OH)2+H]+.Owing to gas phase proton affinity (184.9kcal/mol) of methanol is more than gas phase proton affinity (173.0kcal/mol) of water, therefore methanol molecules is easier to be formed the methanol ion of protonation in conjunction with proton, therefore observes the ion signal of very weak water.
(3) acetone: shown in the figure (c) in Fig. 8, uses acetone to do auxiliary reagent, the protonation of the acetone that is easy to get and dimer signal m/z59, and 117, its structure respectively [C3H6O+H]+[C3H6O)2+H]+。
(4) acetic acid/water: shown in the figure (d) in Fig. 8, uses second aqueous acid as auxiliary reagent, in the negative ion mode, mainly obtains m/z59, and the signal of 92 and 119, m/z59 is the signal [M-H] of acetic acid deprotonation-, m/z92 derives from the combination of methanol in acetic acid and air, and m/z119 is [2M-H]-Signal.
Test case 2:
Milk substrate is complicated, and tripolycyanamide Stability Analysis of Structures, in milk, tripolycyanamide is easily and protein binding, more difficult being analyzed directly detection, choosing tripolycyanamide in milk is object to be measured, and the hot auxiliary surface desorption atmospheric chemical ionization mass spectrum method of gas of the present invention is tested.
Compound concentration is the tripolycyanamide milk soln of 1,10,100,1000,10000 μ g/L, ionization source assist gas (nitrogen) air pressure of the present invention is controlled at 0.13Mpa (250～450mL/min), connect the power supply of this ionization source heater strip 14, assist gas temperature is set to 150 DEG C, use the deionized water of 3.5 μ L/min as auxiliary reagent, spray point ionization voltage is 3.5kv, and after reaching design temperature, ionization source gets final product work.Mass spectrograph 100 adopts cation detection pattern, and sweep limits is 30～200Da, and transfer tube temperature is 170 DEG C, and transfer tube voltage is 7V, and lens voltage is 20V, and maximum ion injection length is 100ms, other mass spectrometer parameters system Automatic Optimal.
Bamboo toothpick is used to dip tripolycyanamide milk soln hand sampling, first mass spectrometric obtains tripolycyanamide characteristic signal m/z127 ((a) referring in Fig. 9), for avoiding false positive to disturb, to guarantee the reliability analyzing result, carry out Tandem Mass Spectrometry Analysis, namely tripolycyanamide protonation signal m/z127 is selected to carry out second mass analysis (CID collision energy is 28%) as parent ion, obtain the fragments characteristic signal m/z110 of melamine molecule, 85, 60 and 43 ((b) referring in Fig. 9), second order ms spectrogram and document spectrogram are contrasted, prove to analyze reliable results.
Test by previous experiments method, the tripolycyanamide milk soln sample of 1,10,100,1000,10000 μ g/L is detected, the sample determination of each concentration 6 times, it is thus achieved that two-stage tandem mass spectrometric data.After the signal background correction obtained in second order ms, measure the clean response signal average strength of m/z85.The signal intensity of fragment m/z85 and sample concentration are taken the logarithm respectively, drawing curve, within the scope of 1～10000 μ g/L, the logarithm (Y) of ionic strength and the logarithm (X) of concentration have good linear relationship (with reference to Figure 10), equation of linear regression Y=0.139x (logC, μ g/L)+1.673 (R=0.994), the relative standard deviation of single sample is between 3.7～7.6%；The tripolycyanamide milk soln of 10 μ g/L is measured, recording the clean response signal average strength of m/z85 is 66.3 (n=12), and to record three times of standard deviations be 6.3 (n=12, S/N=3), it can thus be appreciated that tripolycyanamide detection in milk is limited to 0.95 μ g/L by this method.
During response rate test, in 7 portions of 1mL plain chocolates, the water of 10 μ L is added in 1 part of sample, being separately added into 10 μ L concentration in another 3 parts of samples is 1mg/L tripolycyanamide milk soln, in remaining 3 parts of samples, it is separately added into the tripolycyanamide milk soln that 10 μ L concentration are 10mg/L, is measured according to the method for the present invention.Experimental result is as follows:
As shown in table 1, recovery of standard addition is at 84.6%-109.2%, and relative standard deviation (RSD) is between 4.5%～8.6%.
The tripolycyanamide detection response rate in table 1. milk
In milk, the testing result of tripolycyanamide proves the ionization source working stability of the present invention, there is good selectivity desorbing and ionizability, extremely low detection limit then shows that the mass spectrometric analysis method of the present invention has high sensitivity, the good response rate demonstrates the reliability analyzing result, and the fluctuation analyzing result is likely due to what the reasons such as unstability and the air-flow shakiness of hand sampling caused.
Test case 3:
Isoniazid in tablet and the material such as supplementary product starch, polysaccharide are tightly combined, this test case uses the gas hot auxiliary surface desorption atmospheric chemical ionization source of the present invention that isoniazid tablets is not heated and thermal analysis, investigate this ionization source to the desorption ability of target molecule in solid sample, using the characteristic signal intensity of isoniazid as main comparative feature.
During thermal analysis, ionization source assist gas (nitrogen) air pressure is set to 0.1Mpa, the temperature of assist gas is set to 170 DEG C；Auxiliary reagent is deionized water, flow velocity 3～5 μ L/min；Spray point 7 ionization voltage is 3.5KV.Mass spectrograph 100 adopts cation detection pattern, and sweep limits is 50～400Da, and transfer tube temperature is 150～170 DEG C, and transfer tube voltage is 7V, and lens voltage is 20V, and maximum ion injection length is 100ms, other mass spectrometry parameters system Automatic Optimal.During experiment except adding water-wet coat tablets, not doing other any pretreatment, experimental result is as shown in figure 11.
Shown in (a) in Figure 11, conventional analyzes constantly without heat auxiliary DAPCI, obtain the protonation peak m/z138 of isoniazid, and the protonation signal m/z138 intensity increase about 30% of isoniazid during thermal analysis, and signal m/z121 ((b) referring in Figure 11) be can be observed.Carry out Tandem Mass Spectrometry Analysis ((b) referring in Figure 11) in a heated condition, m/z138 produces the fragment peak m/z121 of isoniazid, in conjunction with first mass spectrometric, the fragment signal using the ionization source of this heating to be likely to obtain isoniazid in first mass spectrometric is described.It addition, isoniazid is measured according to analysis time in the intensity of heating with the protonation signal m/z138 under not heating condition, experimental result is as shown in figure 12.
The change in signal strength of protonation isoniazid (m/z138) shows, isoniazid can quickly desorbing and ionizing in a heated condition, therefore analyze and produce very strong signal (less than 10s) when starting, subsequently owing to fast desorption causes surface isoniazid to reduce and causes signal rapid decrease (10s～20s).Then, along with thermal diffusion gradually and the surface adjuvant of coat tablets and deep layer expand, profound and periphery isoniazid obtains desorbing, and signal strengthens again and gradually to the desorbing limit, and signal produces to reach the strongest at about 40s in this process.Under not heating condition, the desorption ability of desorption gas is more weak, and therefore the desorbing of isoniazid is comparatively slow, and the change in signal strength causing isoniazid is comparatively mild.By analyzing isoniazid signal Strength Changes under two kinds of analysis conditions, it is believed that directly heat analyzed area can make determinand fast desorption and ionizing, and due to the existence of heat transmission, profound and larger surface can obtain desorbing and then obtain more rich sample message.
The gas hot auxiliary surface desorption atmospheric chemical ionization source of the present invention can conveniently obtain the primary ion meeting different analysis demands, the character according to target molecule and sample substrate, it is possible to is effectively improved desorbing and the selectivity of molecular ion reaction.To tripolycyanamide in milk and in isoniazid tablets the analysis of active component show, this ionization source has higher analysis speed, desorbing and ionizing can be improved, and there is sensitive, quick and easy advantage, in carrying out complex sample, in the quick mass spectral analysis of not easily desorbed species, there is certain application prospect.It addition, by producing high-octane primary ion and improving the reactivity of target molecule, improve the cracking probability of structural instability material, for just can obtain the structural information of molecule with the test of less time, it is provided that a kind of new resolving ideas.
It will be appreciated by those skilled in the art that these embodiments are merely to illustrate the present invention and do not limit the scope of the invention, the various equivalent variations that the present invention is made and amendment belong to disclosure scope.
Claims (10)
1. a gas hot auxiliary surface desorption atmospheric chemical ionization source, it is characterized in that, including the head being sequentially connected with, main part and afterbody, it is internally formed the airtight chamber of connection, head and afterbody are communicated with the through hole of chamber respectively, one spray point is placed in described chamber and its needle point through hole extended tips by head, and towards the sample surfaces on specimen disc；Afterbody connects assist gas passage, and assist gas passage introduces assist gas through the through hole of afterbody in described chamber.
2. gas according to claim 1 hot auxiliary surface desorption atmospheric chemical ionization source, it is characterized in that, described head sets the structure of the cavity with described chamber in being, described structure side is provided with auxiliary reagent interface, described interface connects with cavity, connects the microsyringe for introducing auxiliary reagent by pipeline.
3. gas according to claim 1 and 2 hot auxiliary surface desorption atmospheric chemical ionization source, it is characterised in that be relatively set with two countersunk head screwed holes (32 in described head side wall, 33), two bolts are screwed into described countersunk screw holes (32,33) respectively, and afterbody is relative；Described spray point one end is by described two bolt clampings, and the other end stretches out through the through hole (34) of head from the end of described head；The head of bolt is provided with the high voltage power supply joint for connecting the high voltage power supply being applied to spray point.
4. gas according to claim 3 hot auxiliary surface desorption atmospheric chemical ionization source, it is characterized in that, the structure that described head is the cylinder being relatively large in diameter and the less cone of diameter is formed, the through hole (34) of head extends to the cone tip part of cone, and described spray point stretches out from described cone tip part；Described cylindrical sidewall is provided with the temperature thermocouple interface for connecting thermocouple.
5. gas according to claim 4 hot auxiliary surface desorption atmospheric chemical ionization source, it is characterized in that, described main part includes shell, thermal insulation layer, pushing out ring and heater strip, shell is cylinder shell, enclosure interior installs a pushing out ring, thermal insulation layer and heater strip from outside to inside successively, the both ends of shell are respectively provided with tapped through hole (112), are respectively provided with the first fixing bolt and the second fixing bolt in described tapped through hole (112), and two bolts grip heater strip；The one end of the first fixing bolt and the second fixing bolt is respectively provided with the low-tension supply joint for connecting the low-tension supply being applied to heater strip.
6. gas according to claim 5 hot auxiliary surface desorption atmospheric chemical ionization source, it is characterised in that described thermal insulation layer has three layers, is followed successively by fiberglass pipe from outside to inside, has the aluminum foil pipe of asbestos interlayer and high temperature resistant quartz ampoule.
7. the gas hot auxiliary surface desorption atmospheric chemical ionization source according to claim 5 or 6, it is characterised in that also including a temperature controller, it is connected in the circuit loop at heater strip place, and electrically connects with the thermocouple being connected to temperature thermocouple interface.
8. the gas hot auxiliary surface desorption atmospheric chemical ionization source according to any one of claim 1 to 7, it is characterized in that, described afterbody includes tail-hood and pipe joint, tail-hood is the cylinder that the outer sheath diameters with described main part matches, being provided with the screwed hole (211) for connecting line joint in the middle part of it, the bottom of this screwed hole is provided with the through hole (212) being connected with described chamber；Pipe joint is the stud that middle part is provided with through hole, and one end is connected to the screwed hole (211) of tail-hood, and the other end connects assist gas passage and introduces assist gas, and the through hole of pipe joint connects with the through hole (212) of tail-hood.
9. the hot auxiliary surface desorption atmospheric chemical ionization mass spectrometric apparatus of gas, including ionization source, the specimen disc being placed with sample and mass spectrograph, described ionization source is placed on the side of specimen disc at an angle, the spray point of ionization source is towards sample surfaces, and the needle point of spray point and solid sample have certain horizontal range；The mass spectrometric transfer tube mouth of pipe is placed on the opposite side of specimen disc at an angle, has certain horizontal range with solid sample, it is characterised in that described ionization source is the hot auxiliary surface desorption atmospheric chemical ionization of the gas described in any one of claim 1 to 8 source.
10. a mass spectrometric analysis method, it adopts the hot auxiliary surface desorption atmospheric chemical ionization mass spectrometric apparatus of the gas described in claim 9 to carry out mass spectral analysis, comprises the following steps:
(1) assist gas passage is connected on the pipe joint of afterbody, microsyringe is connected to the auxiliary reagent seam of head, the temperature controlling value of temperature controller is arranged design temperature, and sets mass spectrograph.
(2) pass into selected assist gas from pipe joint, and the low-tension supply connecting heater strip is heated, after the temperature of the assist gas within described ionization source arrives the temperature set, pass into selected auxiliary reagent from auxiliary reagent seam.
(3) auxiliary reagent is atomized by the assist gas of high temperature, and under high temperature gas flow drives, the auxiliary reagent of atomization is ionized as primary ion in the needle-tip corona region of discharge of spray point.
(4) high-temperature gas carrying primary ion brushes sample surfaces, target molecule is being heated and is desorbing from sample matrices under the shock of primary ion, being shifted by ionic reaction or energy charge, target molecule is ionized, and enters in mass spectrograph and be analyzed.
(5) regulate the position relationship between specimen disc and ion source, mass spectrograph, make mass spectrometric signal intensity reach maximum, obtain mass spectrometric data.
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