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質譜儀簡介(Translated by ABDC)
http://en.wikipedia.org/wiki/Mass_spectrometry
Mass spectrometry (MS) is an analytical technique that
produces spectra (singular spectrum) of the masses of the molecules comprising a
sample of material.
The spectra are used to determine
the elemental composition of a sample, the masses of particles and of molecules,
and to elucidate the chemical structures of molecules, such as peptides and
other chemical compounds.
Mass spectrometry
works by ionizing chemical compounds to generate charged molecules or molecule
fragments and measuring their mass-to-charge ratios.[1]
質譜是一個用來得出組成樣品材料分子物質譜圖的一種分析技術.
此種譜圖用來測定樣品的基本組成, 粒子以及分子的質量, 以及印證分子的化學結構, 例如肽及其他化合物. 四極桿離子阱的一個衍生型態質譜法(MS)是以使化合物離子化以產生代電荷的粒子或分子的片段, 以及量測它們的質量/電荷 比值, 的方式進行其工作.
In a typical MS procedure, a sample,
which may be solid, liquid, or gas, is ionized. The ions are separated according
to their mass-to-charge ratio.[1] The ions are detected by a mechanism capable
of detecting charged particles.
Signal processing results are displayed as spectra of the relative abundance of
ions as a function of the mass-to-charge ratio. The atoms or molecules can be
identified by correlating known masses to the identified masses or through a
characteristic fragmentation pattern.
在一個典型的質譜程序, 一個樣品, 它可能是固體, 液體或氣體, 被離子化.
這些離子是依據它們的質量/電荷 比值的差異被分離的. 這些離子是是以一種能夠檢測代電荷粒子的機制被檢測.
訊號處理結果是以各離子之間的相對含量與質量/電荷 比值的函數關係的譜圖被展示出來.
這些原子或分子能以與已知物質做相關程度作比對, 或則經由特定的碎片形態特徵的方式被確認出來.
A mass spectrometer consists of three components: an ion
source, a mass analyzer, and a detector.[2] The ionizer converts a portion of
the sample into ions. There is a wide variety of ionization techniques,
depending on the phase (solid, liquid, gas) of the sample and the efficiency of
various ionization mechanisms for the unknown species.
An extraction system removes ions from the sample, which are then trajected
through the mass analyzer and onto the detector. The differences in masses of
the fragments allows the mass analyzer to sort the ions by their mass-to-charge
ratio. The detector measures the value of an indicator quantity and thus
provides data for calculating the abundances of each ion present. Some detectors
also give spatial information, e.g. a multichannel plate.
一個取出系統從樣品裏移出了離子, 然後被投射到質量分析器, 以及到達偵檢器.
碎片之間的質量差異, 使得質量分析器能夠依據這些離子的質量/電荷 比值來排序. 偵檢器量測指標的數值, 如此便可提供計算所存在離子的含量計算所需的數據.
某些偵檢器也可得到空間的資訊, 例如多通道檢測盤.
Mass spectrometry has both qualitative and quantitative uses.
These include identifying unknown compounds, determining the isotopic
composition of elements in a molecule, and determining the structure of a
compound by observing its fragmentation.
Other uses include quantifying the amount of a compound in a sample or studying
the fundamentals of gas phase ion chemistry (the chemistry of ions and neutrals
in a vacuum).
質譜同時具有定性及定量用途. 包括確認出未知化合物, 決定一個分子裏的元素的同位素組成,
以及以觀察其碎片的方式來測定化合物的結構.
其他用途包括定量樣品中的某個化合物的含量,
或是氣相離子化學的基礎研究(真空中的離子或中性物質的化學).
MS is now in very common use in analytical laboratories that
study physical, chemical, or biological properties of a great variety of
compounds.
As an analytical technique it possesses distinct advantages such as:
1. Increased sensitivity over most other analytical techniques because the
analyzer, as a mass-charge filter, reduces background interference
2. Excellent specificity from characteristic fragmentation patterns to identify
unknowns or confirm the presence of suspected compounds.
3. Information about molecular weight.
4. Information about the isotopic abundance of elements. 5. Temporally resolved
chemical data.
質譜在現今非常多的各種化合物的物理, 化學, 及生物學性質研究的分析化學實驗室,
是非常通用的.
作為一種分析技術, 它擁有不同的優點如:
1.比幾乎是大部份其他分析技術更靈敏, 因為其分析器, 作為一種質量-電荷的過濾器,
減少了背景干擾.
2.經由碎片型態的特徵來確定未知成份或是確認疑似化合物的存在等, 所具有的優異的專一性.
3.分子量的資訊.
4.元素同為素含量的資訊.
5.暫時得到的化學數據.
A few of the disadvantages of the method is that often fails
to distinguish between optical and geometrical isomers and the positions of
substituent in o-, m- and p- positions in an aromatic ring. Also, its scope is
limited in identifying hydrocarbons that produce similar fragmented ions.[3]
這個方法的少數缺點是, 它經常無法區分出光學以幾何異構物,
以及的芳香環上的取代基在臨位-, 間位-,及對位-位置. 而且, 在會產生相似碎片的碳水化合物的辯識上, 其應用範圍是受限的.
Etymology(辭源)
The word spectrograph had become part of the international scientific vocabulary
by 1884.[4][5] The linguistic roots are a combination and removal of bound
morphemes and free morphemes which relate to the terms spectr-um and
phot-ograph-ic plate.[6] Early spectrometry devices that measured the
mass-to-charge ratio of ions were called mass spectrographs which consisted of
instruments that recorded a spectrum of mass values on a photographic
plate.[7][8]
spectrograph(攝譜儀)這個字在1884年時就已經成為國技科學字彙的一部份了.
其語言學的根源是與 spectr-um 以及 phot-ograph-ic plate 兩個術語有關的 結合語素和自由語素 的結合與移除.
早期用來量測離子的質量/電荷 比值的光譜儀設備稱為質量攝譜儀, 它是由把質量譜圖記錄在照相版上的一些儀器所組成的.
A mass spectroscope is similar to a mass spectrograph except
that the beam of ions is directed onto a phosphor screen.[9] A mass spectroscope
configuration was used in early instruments when it was desired that the effects
of adjustments be quickly observed. Once the instrument was properly adjusted, a
photographic plate was inserted and exposed.
除了離子束是被引導到螢光屏之外, mass
spectroscope(質量分光鏡)與mass spectrograph(質量攝譜儀)類似. 在早期使用的儀器裏 , 當要能夠很快地觀察調整所產生的效應時,
就會用到質量分光鏡(mass spectroscope)的組態.
The term mass spectroscope continued to be used even though
the direct illumination of a phosphor screen was replaced by indirect
measurements with an oscilloscope.[10] The use of the term mass spectroscopy is
now discouraged due to the possibility of confusion with light
spectroscopy.[1][11] Mass spectrometry is often abbreviated as mass-spec or
simply as MS.[1]
甚至到了直接 照射到到螢光屏的方式已被示波器的非直接量測方式取代之後,
質量攝譜儀(mass spectrograph)的術語仍繼續被使用. 由於有與光學上的光譜儀(ligh spectroscopy)混淆,
使用質量光譜儀(mass spectroscopy)這個術語, 現今不被鼓勵的. 質譜(Mass spectrometry) 經常縮寫成 mass-spec
或簡化為 MS.[1]
History 歷史
For more details on this topic, see History
of mass spectrometry. 有關此主題的更多詳細內容, 請閱質譜的歷史.
Replica of an early mass spectrometer
早期質譜儀的複製品
In 1886, Eugen Goldstein observed rays in gas discharges under
low pressure that traveled away from the anode and through channels in a
perforated cathode,opposite to the direction of negatively charged cathode rays
(which travel from cathode to anode). Goldstein called these positively charged
anode rays "Kanalstrahlen"; the standard translation of this term into English
is "canal rays".
在 1886年, Eugen Goldstein觀察到, 在低壓氣體放電中,
由陽極出來並經過穿孔的陰極通道的射線, 與帶負電的陰極射線方向是相反的(它是由陰極到陽極的).
Goldstein稱這些帶正電的陽極射線為"Kanalstrahlen", 此術語的英文標準翻譯為"canal rays"
Wilhelm Wien found that strong electric or magnetic fields
deflected the canal rays and, in 1899, constructed a device with parallel
electric and magnetic fields that separated the positive rays according to their
charge-to-mass ratio (Q/m). Wien found that the charge-to-mass ratio depended on
the nature of the gas in the discharge tube. English scientist J.J. Thomson
later improved on the work of Wien by reducing the pressure to create the mass
spectrograph.
在1899年, Wilhelm Wien 發現強電或磁場會區折流道中的射線,
同時也建構了一個具有平行電及磁場的設備, 可依據它們的 電荷/質量(Q/m) 比值來分開這些正射線. Wien 發現電荷/質量比 是依放電管裏的氣體的本質而定.
英國學家English scientist J.J. Thomson 之後增進了Wien的工作, 他減少了氣體壓力, 製造出了質譜.
The first application of mass spectrometry to the analysis of
amino acids and peptides was reported in 1958.[12] Carl-Ove Andersson
highlighted the main fragment ions observed in the ionization of methyl
esters.[13] Some of the modern techniques of mass spectrometry were devised by
Arthur Jeffrey Dempster and F.W. Aston in 1918 and 1919 respectively.
質譜最早被應用到胺基酸及舦的分析的報告在1958. Carl-Ove Andersson
突顯出在 methyl esters 離子化所觀察到的主要碎片離子. 一些現代的質譜技術分別是由 Arthur Jeffrey Dempster and
F.W. Aston在 1918 及 1919所設計出來的.
In 1989, half of the Nobel Prize in Physics was awarded to
Hans Dehmelt and Wolfgang Paul for the development of the ion trap technique in
the 1950s and 1960s. In 2002, the Nobel Prize in Chemistry was awarded to John
Bennett Fenn for the development of electrospray ionization (ESI) and Koichi
Tanaka for the development of soft laser desorption (SLD) and their application
to the ionization of biological macromolecules, especially proteins.[14]
在 1989, 有一半的諾貝爾物理獎頒給了Hans Dehmelt and
Wolfgang Paul, 表彰其在1950年代及1960年代的離子捕集技術的發展. 在 2002, 諾貝爾化學獎頒給了John Bennett Fenn,
表彰其在電噴灑離子化(ESI)的發展, 以及頒給了Koichi Tanaka, 表彰其在軟性雷射去吸附(SLD)的發展及其在生物高分子, 尤其是蛋白質的應用.
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Simplified example 簡化的範例
Schematics of
a simple mass spectrometer with sector type mass analyzer. This one is for the
measurement of carbon dioxide isotope ratios (IRMS) as in the carbon-13 urea
breath test
一個具有扇型質量分析器的簡單的質譜儀的示意圖.
這個是用於測量碳13尿素呼氣試驗中的二氧化碳同位素比率(IRMS).
The following
example describes the operation of a spectrometer mass analyzer, which is of the
sector type. (Other analyzer types are treated below.)
以下的範例描述一個質譜的扇型質量分析器的運作
(其他分析器型態在之後處理)
Consider a
sample of sodium chloride (table salt). In the ion source, the sample is
vaporized (turned into gas) and ionized (transformed into electrically charged
particles) into sodium (Na+) and chloride (Cl-) ions. Sodium atoms and ions are
monoisotopic, with a mass of about 23 amu.
考慮一個氯化鈉的樣品(食鹽). 在離子源的地方,
樣品被汽化(成為氣體), 且被離子化(轉為帶電粒子的形態)為鈉離子(Na+)及氯離子(Cl-). 鈉原子及離子是單一同位素的,
其質量約為23原子質量單位(amu).
Chloride
atoms and ions come in two isotopes with masses of approximately 35 amu (at a
natural abundance of about 75 percent) and approximately 37 amu (at a natural
abundance of about 25 percent).
氯原子及離子有2個同位素,
其質量約為35amu(自然界含量約百分之75), 以及約為37amu(自然界含量約百分之25).
The analyzer part of the
spectrometer contains electric and magnetic fields, which exert forces on ions
traveling through these fields. The speed of a charged particle may be increased
or decreased while passing through the electric field, and its direction may be
altered by the magnetic field.
質譜儀的分析器的含有電及磁場, 施加力量給經過這些力場的離子.
在通過電場時, 帶電粒子的速度可被增加或減少, 而其方向可被磁場改變.
The magnitude
of the deflection of the moving ion's trajectory depends on its mass-to-charge
ratio. Lighter ions get deflected by the magnetic force more than heavier ions
(based on Newton's second law of motion, F = ma). The streams of sorted ions
pass from the analyzer to the detector, which records the relative abundance of
each ion type. This information is used to determine the chemical element
composition of the original sample (i.e. that both sodium and chlorine are
present in the sample) and the isotopic composition of its constituents (the
ratio of 35Cl to 37Cl).
運動中離子的軌跡偏折的程度大小是依據它的質量/電荷
比值而定. 比較輕的離子被磁力偏折的程度, 比較重的離子多(基於牛頓第二運動定律 F=ma). 此經過排序的離子串流通過分析器到偵檢器,
它記錄了每一個離子型態的相對含量. 此資訊用來決定原始樣品中的化學元素的組成(也就是說, 鈉及氯市存在於樣品中的), 以及組成(元素)的同位素組成(Cl35 與
Cl37 的比例)
Creating ions 產生離子
Main article: Ion source 離子源
The ion source is the part of the
mass spectrometer that ionizes the material under analysis (the analyte). The
ions are then transported by magnetic or electric fields to the mass analyzer.
Techniques for ionization have been key to determining what types of samples can
be analyzed by mass spectrometry. Electron ionization and chemical ionization
are used for gases and vapors. In chemical ionization sources, the analyte is
ionized by chemical ion-molecule reactions during collisions in the source. Two
techniques often used with liquid and solid biological samples include
electrospray ionization (invented by John Fenn[15]) and matrix-assisted laser
desorption/ionization (MALDI, initially developed as a similar technique "Soft
Laser Desorption (SLD)" by K. Tanaka[16] for which a Nobel Prize was awarded and
as MALDI by M. Karas and F. Hillenkamp[17]).
離子源是質譜儀裏用來使待分析物(樣品)離子化的部份. 然後,
離子會被磁場或電場輸送到質量分析器. 離子化的技術是決定那些型態的樣品能夠被質譜儀分析的關鍵. 電離子化及化學離子化用於氣體及蒸氣. 在化學離子化離子源的,
待分析物是在來源的地方, 經由碰撞的化學離子反應而被離子化的. 有兩項技術經常用於液體及固體生物分子, 包括電噴灑離子化(John Fenn所發明),
以及基質輔助雷射去吸附離子化(MALDI, 起先是由 K. Tanaka 發展的一個類似的技術 "Soft Laser Desorption (SLD)" ,
為此給了諾貝爾頒, 以及由 M. Karas and F. Hillenkamp[17] 的MALDI)
Inductively coupled plasma
電感耦合電漿(即等離子體)
Inductively
coupled plasma (ICP) sources are used primarily for cation analysis of a wide
array of sample types. In this type of Ion Source Technology, a 'flame' of
plasma that is electrically neutral overall, but that has had a substantial
fraction of its atoms ionized by high temperature, is used to atomize introduced
sample molecules and to further strip the outer electrons from those atoms.
電感耦合電漿(ICP)來源主要用於很廣的系列的樣品型態的陽離子的分析.
在這個型態的離子源技術中, 電漿的"火焰"是整體電中性的, 但有很大的一部份是被高溫所離子化的. 此電漿用來將導入的樣品原子化,
且更進一步地將這些原子的外層電子剝離了.
The plasma is
usually generated from argon gas, since the first ionization energy of argon
atoms is higher than the first of any other elements except He, O, F and Ne, but
lower than the second ionization energy of all except the most electropositive
metals. The heating is achieved by a radio-frequency current passed through a
coil surrounding the plasma.
電漿通常用氬氣製造(Ar), 因為氬原子的第一離子化能,
比任何其他原素的第一(離子化能)還高, 除了He, O, F and Ne 以外, 但比所有(原素)的第二(離子化能)還低, 除了最電陽性的金屬之外.
加熱的方式是以一個射頻電流通過一個環繞電漿的線圈.
Other ionization
techniques(其它離子化的技術) Others include glow discharge, field desorption (FD), fast
atom bombardment (FAB), thermospray, desorption/ionization on silicon (DIOS),
Direct Analysis in Real Time (DART), atmospheric pressure chemical ionization
(APCI), secondary ion mass spectrometry (SIMS), spark ionization and thermal
ionization (TIMS).[18] Ion attachment ionization is an ionization technique that
allows for fragmentation free analysis.
其它包括輝光放電, 場效應去吸附, 快原子轟擊(FAB), 熱噴灑,
在silicon上的去吸附或離子化(DIOS), 真時直接分析(DART), 大氣壓化學離子化(APCI), 二度離子質譜(SIMS),
火花離子化及熱離子化(TIMS). 離子附著離子化是一種可以達到無碎片產生的離子化技術. |
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Hard Ionisation & Soft Ionisation 硬離子化與軟離子化
In mass
spectrometry (MS), ionisation (or ionization) refers to the production of gas
phase ions suitable for resolution in the mass analyser or mass filter.
Ionisation occurs in the instrument ion source.
There are a plethora of ion sources
available, each has advantages and disadvantages for particular applications.
For example, Electron Impact (EI) ionisation gives a high degree of
fragmentation, yielding highly detailed mass spectra which when skilfully
analysed can provide important information for structural
eluciation/characterisation and facilitate identification of unknown compounds
by comparison to mass spectral libraries obtained under identical operating
conditions.
在質譜(MS)裏,
離子化指的是適用於以質量分析器及質量過濾器解析的氣相離子的製造. 離子化發生在儀器的離子源.
有太多的離子源可以取得, 每一種都有特定應用方面的優缺點. 例如,
電子碰撞(EI)離子化得到高程度的碎片, 產出很詳細的質譜, 經過很有技巧地分析後, 能提供用於辨識結構特徵的重要訊息,
經由比較相同操作條件下所得到的質普資料庫, 得到未知化合物的確認.
However, EI is not suitable for
coupling to HPLC, i.e. LC-MS, since at atmospheric pressure, the filaments used
to generate electrons burn out rapidly. Thus EI is coupled predominantly with
GC, i.e. GC-MS, where the entire system is under high vacuum.
無論如何, 電子碰撞(EI)不適合聯結到HPLC,
即LC-MS,因為在大氣壓下, 產生電子的燈絲很快就燒掉了. 因此, EI 主要是聯結GC, 即GC-MS, 因其整個系統是處於高度真空的中.
Ionisation
techniques can be described as belonging to one of the following categories:
Hard Ionisation Soft Ionisation Hard Ionisation Hard ionisation techniques are
processes which impart high quantities of residual energy in the subject
molecule invoking large degrees of fragmentation (i.e. the systematic rupturing
of bonds acts to remove the excess energy, restoring stability to the resulting
ion). Resultant ions tend to have m/z lower than the molecular mass (other than
in the case of proton transfer and not including isotope peaks). The most common
example of hard ionisation is Electron Impact Ionisation (EI).
離子化技術能以屬於以下的類型之一來描述: 硬離子化 軟離子化
硬離子化技術是置入大量殘留能量在目標分子, 使能夠達到很大程度的碎片化的程序. (也就是說, 鍵結的系統性裂解, 用以移除過多的能量,
使產生的離子保持在穩定的狀態). 使產生的離子傾向於具有比分子質量還低的質量/電荷比, m/z. (質子轉移的營情況除外, 以及不包括同為素成份峰).
硬離子化最常見的例子是電子碰撞離子化(EI).
Soft
Ionisation Soft ionisation refers to the processes which impart very little
residual energy onto the subject molecule and as such result in very little
fragmentation. Examples include: Fast atom bombardment (FAB) Chemical ionisation
(CI) Atmospheric Pressure Chemical Ionisation (APCI) Electrospray Ionisation
(ESI) Matrix Assisted Laser Desorption Ionisation (MALDI)
軟離子化硬離子化技術指的是置入很少過剩的能量在目標分子,
使能產生很小的碎片化的程序. 範例包括: 快原子轟擊(FAB) 化學離子化(CI) 大氣壓化學離子化(APCI) 電噴灑離子化(ESI)
基質輔助雷射去吸附離子化(MALDI) |
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Mass selection 質量的選擇
Mass
analyzers separate the ions according to their mass-to-charge ratio. The
following two laws govern the dynamics of charged particles in electric and
magnetic fields in vacuum:
F = Q (E + v x B) (Lorentz force
law);
F=ma (Newton's second law of motion
in non-relativistic case, i.e. valid only at ion velocity much lower than the
speed of light).
Here F is the force applied to the
ion, m is the mass of the ion, a is the acceleration, Q is the ion charge, E is
the electric field, and v × B is the vector cross product of the ion velocity
and the magnetic field.
質量分析器根據離子的質量/電荷 比值來進行分離.
以下兩個定律主窄了帶電粒子在真空電場內的動力學.
F = Q (E + v x B) (洛倫茲力學定律);
F=ma (定律第二運動定律在非相對論的情況,
有就是只有在離子速度遠低於光速時才成立).
將上述2兩施力表述式連接取代得出:
(m/Q)a = E+ v x B.
在此, F是加在離子的力, m 是離子的質量, a 是加速度,
Q是電荷, E 是電場, 以及 v x B 是離子速度與磁場的向量外積.
This
differential equation is the classic equation of motion for charged particles.
Together with the particle's initial
conditions, it completely determines the particle's motion in space and time in
terms of m/Q.
Thus mass spectrometers could be
thought of as "mass-to-charge spectrometers".
When presenting data, it is common
to use the (officially) dimensionless m/z, where z is the number of elementary
charges (e) on the ion (z=Q/e). This quantity, although it is informally called
the mass-to-charge ratio, more accurately speaking represents the ratio of the
mass number and the charge number, z.
這個微分方程式是帶電粒子運動的古電方程式. 加上了粒子的初始化條件,
它以質量/電荷比值的項目, 完全地決定了粒子在空間及時間中的運動. 質量儀可以被想成像是"質量 對電荷 的光譜儀".
在作數據的表達時, 它常用到(官方的)無因次的單位 m/z,
其中z是離子的基本電荷(e)的數目(z=Q/e). 這個數量, 雖然非正式地被稱為 質量/電荷 比質, 更準確地說, 是代表質量/基本電荷數目 比值.
There are many types of mass
analyzers, using either static or dynamic fields, and magnetic or electric
fields, but all operate according to the above differential equation.
Each analyzer type has its strengths
and weaknesses. Many mass spectrometers use two or more mass analyzers for
tandem mass spectrometry (MS/MS).
In addition to the more common mass
analyzers listed below, there are others designed for special situations.
質量分析器的型式很多, 使用靜態的或動態的力場, 及磁場或電場,
但都是依照上述的微分方程式運作.
每個質量分析器有其強項與入弱點.
很多質譜儀使用2個或更多質量分析器做為串連質譜(MS/MS).
除了以下列出的常見質量分析器以外, 有其他用於特別情境的設計.
There are
several important analyser characteristics.
The mass resolving power is the
measure of the ability to distinguish two peaks of slightly different m/z.
The mass accuracy is the ratio of
the m/z measurement error to the true m/z.
Mass accuracy is usually measured in
ppm or milli mass units.
The mass range is the range of m/z
amenable to analysis by a given analyzer.
The linear dynamic range is the
range over which ion signal is linear with analyte concentration.
Speed refers to the time frame of
the experiment and ultimately is used to determine the number of spectra per
unit time that can be generated.
質量分析器有幾個重要特徵.
質量解析的能力的量測,
是以能夠辨別出只有輕微質量/電荷比值(m/z)差異的2個成份峰的能力.
質量測量的準確度是量測所得的m/z與真實的m/z 的比值.
質量測量的準確度通常是以ppm 或是milli mass
units作為其量測單位.
質量的範圍是適合某一個質量分析器分析的 m/z 的範圍.
線性範圍是離子(強度)訊號與分析物濃度程線性關係的範圍.
速度指的是實驗過程的時間框架,
終極目的是用來測定單為時間所能產生的譜圖數.
Sector
instruments
For more details on this topic, see
sector instrument.
A sector field mass analyzer uses an
electric and/or magnetic field to affect the path and/or velocity of the charged
particles in some way.
As shown above, sector instruments
bend the trajectories of the ions as they pass through the mass analyzer,
according to their mass-to-charge ratios, deflecting the more charged and
faster-moving, lighter ions more. The analyzer can be used to select a narrow
range of m/z or to scan through a range of m/z to catalog the ions present.[19]
扇型儀器
更多主題的詳細內容, 請見 扇型儀器
一個扇型力場的質量分析器以電場或磁場的某種方式的來影響帶電粒子的路徑或速度.
如上所示, 當離子通過質量分析器時, 扇型儀依據質量/電荷 比值,
彎曲了離子的軌跡, 使帶電較多的, 輕些的離子偏折更多. 此質量分析器能用於選別一個狹窄m/z範圍或掃描過一個m/z範圍以得出存在離子的目錄.
Time-of-flight
For more details on this topic, see
time-of-flight mass spectrometry.
The time-of-flight (TOF) analyzer
uses an electric field to accelerate the ions through the same potential, and
then measures the time they take to reach the detector.
If the particles all have the same
charge, the kinetic energies will be identical, and their velocities will depend
only on their masses.
Lighter ions will reach the detector
first.[20]
時間飛行
更多主題的詳細內容, 請見 時間飛行
時間飛行(TOF)質量分析器用電場及相同的電壓以加速離子,
然後量測它們到達偵檢器的時間. 如果全部的粒子有同樣的電荷, 其動能將是相同的, 而且它們的速度將取決於它們的質量. 較輕的離子會先到達偵檢器.
Quadrupole
mass filter
For more details on this topic, see
Quadrupole mass analyzer.
Quadrupole mass analyzers use
oscillating electrical fields to selectively stabilize or destabilize the paths
of ions passing through a radio frequency (RF) quadrupole field created between
4 parallel rods.
Only the ions in a certain range of
mass/charge ratio are passed through the system at any time, but changes to the
potentials on the rods allow a wide range of m/z values to be swept rapidly,
either continuously or in a succession of discrete hops.
A quadrupole mass analyzer acts as a
mass-selective filter and is closely related to the quadrupole ion trap,
particularly the linear quadrupole ion trap except that it is designed to pass
the untrapped ions rather than collect the trapped ones, and is for that reason
referred to as a transmission quadrupole.
四極桿質量過濾器
更多主題的詳細內容, 請見 四極桿質量過濾器
四極桿質量分析器 使用震盪電場以選擇性地穩定或去穩定離子通過的路徑,
此路徑是在4根平行棒之間產生的射頻(RF)四極場.
在任何時間裏,
只有在一定質量/電荷比值(m/z)範圍內的離子通過這個系統, 而改變極桿之間的電位可允許很寬廣的(m/z)範圍值被快速掃過, 連續地或不連續地接續跳躍均可.
做為一種質量選擇過濾器, 四極桿質量分析器 與
四極桿離子阱有很近相關性, 特別是線性四極桿離子阱. 差別在於的是它是設計要讓為被捕捉住的離子通過, 而不是要收集被捕捉住的, 也因此, 被指稱為穿透式四極桿.
A common
variation of the transmission quadrupole is the triple quadrupole mass
spectrometer.
The “triple quad” has three
consecutive quadrupole stages, the first acting as a mass filter to transmit a
particular incoming ion to the second quadrupole, a collision chamber, wherein
that ion can be broken into fragments.
The third quadrupole also acts as a
mass filter, to transmit a particular fragment ion to the detector.
If a quadrupole is made to rapidly
and repetitively cycle through a range of mass filter settings, full spectra can
be reported.
Likewise, a triple quad can be made
to perform various scan types characteristic of tandem mass spectrometry.
穿透式四極桿常見的變異體為三重四極桿質譜儀.
triple quad”有三個接續的四極桿階段.
第一個當做質量過濾器使某個特定的來源離子穿過到第二個四極桿(一個碰撞室, 在這裏面離子能被破碎成碎片), 第三個四極桿也是質量過濾器的作用,
用以通過特定的離子碎片到偵檢器.
如果一個四極桿被做成要快速且重複地在一個範圍的質量分析設定循環操作,
即能得到全部的譜圖.
類似相同地,
三重四極桿質譜儀也能被製成能夠進行串連質譜儀的不同的掃描型態特徵.
Ion traps
Three-dimensional quadrupole ion
trap
For more details on this topic, see
quadrupole ion trap.
The quadrupole ion trap works on the
same physical principles as the quadrupole mass analyzer, but the ions are
trapped and sequentially ejected.
Ions are trapped in a mainly
quadrupole RF field, in a space defined by a ring electrode (usually connected
to the main RF potential) between two endcap electrodes (typically connected to
DC or auxiliary AC potentials). The sample is ionized either internally (e.g.
with an electron or laser beam), or externally, in which case the ions are often
introduced through an aperture in an endcap electrode.
離子阱
三維四極桿離子阱
更多主題的詳細內容, 請見 四極桿離子阱
四極桿離子阱工作方式與四極桿質量分析器是相同的,
但離子是被捕捉住且依續被噴出.
離子主要是被捕集在四極桿的射頻場域內,
此場域空間是由一個介於兩端蓋電極的環狀電極所定出. (環狀電極通常連接到主FR電位, 兩端蓋電極通常連接到 DC 或 府助AC 電位).
樣品在內部離子化(例如用一個電子束或雷射光束) 或在外部,
在這情況下(在外部) 離子經常是經由端蓋電極的一個針孔導入的.
There are
many mass/charge separation and isolation methods but the most commonly used is
the mass instability mode in which the RF potential is ramped so that the orbit
of ions with a mass a > b are stable while ions with mass b become unstable and
are ejected on the z-axis onto a detector.
There are also non-destructive
analysis methods. Ions may also be ejected by the resonance excitation method,
whereby a supplemental oscillatory excitation voltage is applied to the endcap
electrodes, and the trapping voltage amplitude and/or excitation voltage
frequency is varied to bring ions into a resonance condition in order of their
mass/charge ratio.[21][22]
The cylindrical ion trap mass
spectrometer is a derivative of the quadrupole ion trap mass spectrometer.
有許多質量/電荷分離和隔離的方法, 但最通常的是質量不穩定模式,
在這模式裏, 電位被進行斜坡式的改變, 以使在軌道內質量a(較b大)的離子是穩定的, 而質量b的離子變成不穩定, 因而被自Z軸噴出到偵檢器上.
另也有非破壞式的分析方法. 離子也能以共振激發的方法被噴出, 在此,
一個補充的振盪激發電位被施加到端蓋電極, 且依據離子的質量/電荷比值順序, 變動捕捉電位/或激發電位頻率, 依序將離子帶入一共振條件.
氣缸式離子阱質譜儀是四極桿離子阱質譜儀的一個衍生.
Linear
quadrupole ion trap
A linear quadrupole ion trap is
similar to a quadrupole ion trap, but it traps ions in a two dimensional
quadrupole field, instead of a three-dimensional quadrupole field as in a 3D
quadrupole ion trap.
Thermo Fisher's LTQ ("linear trap
quadrupole") is an example of the linear ion trap.[23]
A toroidal ion trap can be
visualized as a linear quadrupole curved around and connected at the ends or as
a cross section of a 3D ion trap rotated on edge to form the toroid, donut
shaped trap.
The trap can store large volumes of
ions by distributing them throughout the ring-like trap structure.
This toroidal shaped trap is a
configuration that allows the increased miniaturization of an ion trap mass
analyzer.
Additionally all ions are stored in
the same trapping field and ejected together simplifying detection that can be
complicated with array configurations due to variations in detector alignment
and machining of the arrays.[24]
線性四極桿離子阱
線性四極桿離子阱類似於四極桿離子阱, 但它把離子補捉在二維的四極桿場域,
而不是像是3D四極桿離子阱的三維的四極桿場域.
Thermo Fisher's LTQ ("linear trap
quadrupole") 就是一個線性四極桿離子阱的範例.
環形的離子阱能被視為 灣曲且兩端連接的 線性四極桿,
或是是選旋轉3D離子阱的邊緣, 形成一磁環, 甜甜全圈形狀的補捉器. 此補捉器將離子遍佈到環狀補捉結構, 能儲存大量的離子.
此外, 非本方式設計的偵檢器對準及陣列的機械加工的變異,
使得陣列的組態讓偵檢器設計複雜化, 而本方式設計, 全部的離子是被儲存在相同的補捉場域內且被一起噴出, 因而簡化偵檢器.
Orbitrap
For more details on this topic, see
Orbitrap.
These are similar to Fourier
transform ion cyclotron resonance mass spectrometers (see text below).
Ions are electrostatically trapped
in an orbit around a central, spindle shaped electrode.
The electrode confines the ions so
that they both orbit around the central electrode and oscillate back and forth
along the central electrode's long axis.
This oscillation generates an image
current in the detector plates which is recorded by the instrument.
The frequencies of these image
currents depend on the mass to charge ratios of the ions.
Mass spectra are obtained by Fourier
transformation of the recorded image currents.
Orbitraps have a high mass accuracy,
high sensitivity and a good dynamic range.[25]
軌道補捉器(阱)
更多主題的詳細內容, 請見 軌道補捉器(阱)
這些類似於 傅利葉轉換離子迴旋加速共振質譜儀(見後文).
離子是靜態地被補捉在一個軌道, 圍繞在一個中間的, 槳葉形狀的電極.
此電極圍住了離子, 使它們圍繞著中間電極運行, 且延著中間電極長軸方向來回振盪.
此振盪在偵檢器的偵測板上產生一個被儀器記錄下來的鏡像電流.
此鏡像電流的頻率相依於離子的質量/電荷 比值.
質譜圖是由所記錄的鏡像電流經過傅利葉轉換所得到.
Fourier
transform ion cyclotron resonance
For more details on this topic, see
Fourier transform mass spectrometry.
Fourier transform mass spectrometry
(FTMS), or more precisely Fourier transform ion cyclotron resonance MS, measures
mass by detecting the image current produced by ions cyclotroning in the
presence of a magnetic field.
Instead of measuring the deflection
of ions with a detector such as an electron multiplier, the ions are injected
into a Penning trap (a static electric/magnetic ion trap) where they effectively
form part of a circuit.
Detectors at fixed positions in
space measure the electrical signal of ions which pass near them over time,
producing a periodic signal.
Since the frequency of an ion's
cycling is determined by its mass to charge ratio, this can be deconvoluted by
performing a Fourier transform on the signal.
FTMS has the advantage of high
sensitivity (since each ion is "counted" more than once) and much higher
resolution and thus precision.[26][27]
Ion cyclotron resonance (ICR) is an
older mass analysis technique similar to FTMS except that ions are detected with
a traditional detector. Ions trapped in a Penning trap are excited by an RF
electric field until they impact the wall of the trap, where the detector is
located.
Ions of different mass are resolved
according to impact time.
傅利葉轉換離子迴旋加速共振
更多主題的詳細內容, 請見 傅利葉轉換質譜儀
傅利葉轉換質譜儀(FTMS), 或更精準地,
傅利葉轉換離子迴旋加速共振MS, 以偵測離子在磁場存在下的迴旋加速所產生的鏡像電流來量測質量.
不是以像電子倍增器的偵測去量測離子的偏折, 而是離子被噴入個"潘寧陷井"
(一個靜態的電/磁離子阱), 在此它們很有效地形成電路的一部份.
在空間中固定位置的偵檢器, 長時間量測通過他附近的離子的電訊號,
產生了一種週期性的訊號. 由於離子的迴旋加速的頻率是有由其質量/電荷 比值所決定, 因此可經由進行訊號的傅利葉轉換作解卷積.
FTMS 具有高靈敏度(因為離子是被重複"計算"一次以上),
及更高的解析度精確度.
離子迴旋加速共振(ICR) 是一種舊一些的質譜分析技術,
除了離子是用傳統的偵檢器檢測以外, 相似於FTMS. 被補捉在"潘寧陷井"的離子, 被以射頻電場激發, 直到它們撞擊到補捉器的器壁, 偵檢器在這裏.
不同質量的離子是依據撞擊時間被解析.
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Detectors
Tandem mass spectrometry
Common mass spectrometer configurations and techniques Chromatographic
techniques combined with mass spectrometry
LC/MS or LC-MS, GC/MS or GC-MS
Data and analysis Applications |
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