Name: quadrupole, tof, and ion trap analyzers
Uploaded: 2024-04-04T10:51:34.000Z
Duration: 1 min 19 s
Channel: JoVE

사중극자 질량 분석기는 4개의 병렬 로드로 구성되며, 이 막대에는 DC 전압과 무선 주파수 AC 전압이 적용됩니다.
여기서 자기장 강도는 특정 m/z 값을 가진 이온만 자기장과 공명하고 검출기에 부딪히게 합니다. 이 분석기는 낮은 해상도를 제공합니다.
또 다른 일반적인 분석기는 ToF(Time-of-Flight) 분석기로, 여기서 이온 비행 시간은 소스에서 선형 자기장이 없는 튜브를 통해 검출기까지 측정됩니다.
모든 이온은 거의 동일한 운동 에너지를 가지므로 가벼운 이온은 속도가 더 빠르기 때문에 비행 시간이 짧아집니다.
해상도를 향상시키기 위해 반사판 또는 이온 반사체가 사용됩니다. 그들은 더 에너지가 많은 이온의 속도를 늦추고 동일한 질량의 이온 간의 운동 에너지 차이를 수정합니다.
또 다른 대안은 링 전극과 한 쌍의 엔드캡 전극으로 구성된 3차원 사중극자 이온 트랩입니다. 무선 주파수 전압은 고리에서 진동하는 이온을 가둡니다.
무선 주파수 전압을 높이면 점진적으로 더 무거운 이온이 안정화되어 검출기로 선택적으로 방출됩니다.

질량 분석기: 일반적인 유형

Mass Analyzers: Common Types

사중극자 질량 분석기는 DC 전압과 무선 주파수 AC 전압을 전달하는 다이아몬드에 배열된 4개의 원통형 금속 막대로 구성됩니다. 사중극자를 통과하는 이온의 움직임은 전계 강도에 따라 달라지며 특정 m/z의 이온만 성공적으로 공명하여 주어진 전계 강도에서 검출기에 도달하게 됩니다. 이러한 분석기의 전송 속도는 높지만 분해능이 낮기 때문에 샘플의 정확한 원소 구성이 결정되지 않습니다. 그러나 비용 효율적입니다. 사중극자 분석기의 일반적인 분해능은 1 Da(또는 1 u)입니다.

TOF(Time-of-Flight) 분석기에서는 소스에서 선형 무장 드리프트 튜브를 통해 검출기까지 이온의 비행 시간을 마이크로초 단위로 측정하고 이 시간을 m/z 값으로 변환합니다. 이온은 거의 동일한 양의 운동 에너지를 가지고 드리프트 튜브로 들어갑니다. 따라서 m/z 값이 서로 다른 이온은 서로 다른 속도로 이동하고 서로 다른 시간에 검출기에 도달합니다. 가벼운 이온은 더 빠른 속도로 이동하므로 비행 시간이 더 짧아지고 분해능도 상대적으로 떨어집니다. 이온에 전달되는 운동 에너지 양의 차이로 인해 분리능이 손상될 수도 있으며, 이로 인해 동일한 m/z의 이온이 서로 다른 속도를 갖게 됩니다. 이 때문에 검출기까지의 이동 거리를 늘리고 이온의 속도를 늦추기 위해 반사체(또는 이온 거울)가 사용됩니다. 이온의 에너지가 높을수록 속도가 느려지므로 반사체가 운동 에너지 확산을 수정하고 전반적으로 더 나은 분해능을 제공합니다. 또한 TOF 분석기는 높은 감도를 제공합니다.

3차원 사중극자 이온 트랩 분석기는 링 전극과 두 개의 엔드캡 전극으로 구성됩니다. 무선 주파수 전압은 링에서 진동하는 이온을 포착합니다. 무선 주파수 전압을 높이면 무거운 이온이 안정화되고 선택적으로 엔드캡의 구멍을 통해 검출기로 방출됩니다. 다른 질량 분석기는 작은 부분의 이온만 검출기에 도달하도록 허용하는 반면, 3차원 사중극자 이온 트랩은 이온의 절반이 검출기에 도달할 수 있도록 하여 이러한 분석기를 더욱 민감하게 만듭니다. 그러나 이온 트랩에 많은 수의 이온이 저장되면 공간 전하 효과로 인해 분해능이 저하됩니다.

사중극자 질량 분석기는 4개의 병렬 로드로 구성되며, 이 막대에는 DC 전압과 무선 주파수 AC 전압이 적용됩니다.
여기, 필드 ...

Education

교육

JoVE Core

Analytical Chemistry

분석 화학

Unit 1

제1단원

Principles of Mass Spectrometry

질량 분석법의 원리

KEY TERMS AND CONCEPTS

주요 용어 및 개념

quadrupole, tof, and ion trap analyzers

Quadrupole, time-of-flight, and ion trap mass analyzers each separate ions in a different way. They are common tools in mass spectrometry and help sort ions by their mass-to-charge ratio, or m/z.

A quadrupole mass analyzer uses four cylindrical metal rods arranged in a diamond shape. The rods carry a direct current, or DC, voltage and a radio-frequency AC voltage. Ion motion depends on the field strength, so only ions with a certain m/z resonate and reach the detector at that setting. This analyzer has a high transmission rate and is cost-effective, but its low resolution means it does not determine the exact elemental composition of a sample. Its typical resolution is about 1 Da, or 1 u.

A time-of-flight, or TOF, analyzer measures how long ions take to travel from the source through a field-free drift tube to the detector. The flight time is measured in microseconds and converted to an m/z value. Ions enter the tube with about the same kinetic energy, so lighter ions move faster and arrive sooner. That shorter flight time can limit resolution. Resolution can also drop if ions with the same m/z start with different kinetic energies and travel at different speeds.

To improve TOF performance, a reflectron, or ion mirror, can be used. It increases the distance to the detector and slows the ions down. More energetic ions experience a greater slowdown, so the reflectron corrects kinetic energy spread and improves resolution overall. TOF analyzers also offer high sensitivity.

Three-dimensional quadrupole ion-trap analyzers use a ring electrode and two endcap electrodes. A radio-frequency voltage traps the ions so they oscillate in the ring. When the radio-frequency voltage increases, heavier ions become stabilized and are selectively ejected through apertures in the endcaps to the detector. Compared with other mass analyzers that allow only a small fraction of ions to reach the detector, the three-dimensional quadrupole ion trap can send about half of the ions to the detector, which makes it more sensitive. If too many ions are stored, space-charge effects reduce resolution.

Quadrupole, TOF, and Ion Trap Analyzers

mass spectrometry: overview

Mass Spectrometry and Molecular Identity

Mass spectrometry helps identify a compound by measuring its molecular mass and molecular formula. It does this by turning the analyte molecule into ions and then comparing ion abundance with mass-to-charge ratio. One common ionization method is electron ionization, or EI. In EI, high-energy electron beams strike analyte molecules in the gas phase. The beam removes an electron and leaves a molecular ion behind. A molecular ion is a radical cation, so it has a positive charge and an unpaired...

mass spectrometry: isotope effect

Isotope Peaks in Mass Spectra

Isotope peaks in mass spectra show how natural isotope mixtures change the signal of a molecule. Most elements occur as a mix of isotopes, which are atoms of the same element with different numbers of neutrons. Because isotopes have different masses, the same fragment can appear at more than one position in a spectrum. The mass of a molecule depends on which isotopes are present in its atoms. The size of each isotope peak also depends on how common those isotopes are in nature. Carbon is a...

mass spectrometry: molecular fragmentation overview

mass-spectrometry-molecular-fragmentation-overview

Mass Spectrometry Fragmentation Patterns

Mass spectrometry fragmentation patterns show how a molecular ion breaks apart after ionization. When a molecule loses an electron inside the mass spectrometer, its structure becomes unstable. The ion then fragments at bonds that often produce the most stable pieces. One common pattern is cleavage of a single bond in the molecular ion. This break forms a radical and a cation. The bond can split in more than one way, but the favored path is the one that gives the more stable carbocation rather...

mass spectrometers

How Mass Spectrometers Sort Ions

A mass spectrometer sorts charged ions by their mass-to-charge ratio and records their relative abundance. It turns vaporized analyte molecules into ions, separates them, and then measures the signal from each type of ion. The process begins in the ionization chamber. The analyte is in the gas phase inside a vacuum, and it is struck by high-energy electrons. The electrons have about 70 eV of energy, which is enough to remove an electron from the analyte and form a molecular ion. After...

mass spectrum

Reading Peaks in a Mass Spectrum

A mass spectrum shows the charged fragments in an analyte as peaks plotted by mass-to-charge ratio, or m/z. The x-axis gives the mass of each charged fragment divided by the number of charges it carries. The y-axis shows the relative abundance of each charged species based on the signal intensity recorded at the detector. The tallest peak is called the base peak. It is assigned an abundance of 100%, and the other peaks are scaled against it. The peak from the molecular ion is called the parent...

mass spectrum: interpretation

Decoding Molecular Ions in Mass Spectra

Mass spectra help scientists identify an unknown compound by finding the molecular ion peak. The molecular ion peak shows the mass of the intact molecule, but it is often weak or missing because high-energy electron beams cause strong fragmentation. When that happens, a soft-energy electron beam can be used to scan the spectrum and improve the molecular ion signal. Other ionization methods can also give a stronger molecular ion peak. Chemical ionization, field ionization, and desorption...

mass analyzers: overview

Mass Analyzers and Ion Separation

Mass analyzers separate ions by their mass-to-charge ratio, or m/z, in a mass spectrometer. After a sample is vaporized in the ionization chamber, it is hit with a high-energy electron beam. This creates a radical cation and also produces neutral molecules, radicals, and cations. Negatively charged accelerator plates then push the cations into the mass analyzer, where they are sent on to the detector. Several mass analyzer designs are commonly used. These include magnetic sector,...

mass analyzers: common types

Quadrupole, time-of-flight, and ion trap mass analyzers each separate ions in a different way. They are common tools in mass spectrometry and help sort ions by their mass-to-charge ratio, or m/z. A quadrupole mass analyzer uses four cylindrical metal rods arranged in a diamond shape. The rods carry a direct current, or DC, voltage and a radio-frequency AC voltage. Ion motion depends on the field strength, so only ions with a certain m/z resonate and reach the detector at that setting. This...

high-resolution mass spectrometry (hrms)

Mass Accuracy in HRMS Analysis

High-resolution mass spectrometry separates ions by very small differences in mass. This matters because atomic masses are not always exact whole numbers, even though they are often rounded for simple calculations. Atomic mass is usually estimated by adding the masses of protons and neutrons. In reality, the proton and neutron do not have exactly the same mass. That creates small differences when atomic masses are compared to the simplest hydrogen atom. Helium, for example, is made of 2...

mass spectrometry: complex analysis

Hyphenated Mass Spectrometry Methods

Mass spectrometry can be paired with separation methods to study complex mixtures. This combination is called a hyphenated method. It helps when a pure mass spectrum is too hard to read because a mixture causes too much fragmentation and too many overlapping signals. GC-MS is one common hyphenated method. GC stands for gas chromatography, which separates volatile, thermally stable compounds in narrow capillary columns before they enter the mass spectrometer. This approach is widely used in...

tandem mass spectrometry

MS/MS Scan Modes and Fragment Ions

Tandem mass spectrometry uses two or more mass analyzers in series to improve selectivity and lower chemical noise during analyte detection. A set of analyzers separated by an interaction cell lets the instrument break ions apart and study the fragment ions that form. Fragmentation happens in the interaction cell and can be caused in several ways. Collision-induced dissociation, or CID, uses inert gases such as nitrogen, argon, or helium. Other methods include surface-induced dissociation...

gas chromatography&ndash;mass spectrometry (gc&ndash;ms)

How GC-MS Separates and Identifies Compounds

Gas chromatography-mass spectrometry (GC-MS) separates compounds in a mixture and then identifies them. A gas chromatograph first splits the mixture into its parts. A mass spectrometer then analyzes each part on its own to determine molecular masses and molecular structures. The gas chromatograph uses a long, narrow capillary column. The inner wall of the column has a polysiloxane coating. This coating serves as the stationary phase. It has a high boiling point, low viscosity, and low polarity.

inductively coupled plasma&#8211;mass spectrometry (icp&#8211;ms): overview

inductively-coupled-plasmamass-spectrometry-icpms-overview

ICP-MS Sample Ionization and Detection

ICP-MS uses an inductively coupled plasma torch to turn samples into ions for mass analysis. Solid samples are first dissolved and volatilized before they enter the hot argon plasma. Solution samples are nebulized, which means they are converted into a fine spray, and then passed through the same plasma. Inside the plasma, the analytes break apart. Their atoms become positively charged ions, along with some molecular species. These positive ions are sent to the mass spectrometer, where they...

inductively coupled plasma-mass spectrometry (icp-ms): interferences

inductively-coupled-plasma-mass-spectrometry-icp-ms-interferences

ICP-MS Signal Interference Sources and Fixes

Inductively coupled plasma-mass spectrometry (ICP-MS) is a sensitive method for elemental analysis, but its spectra can be affected by interferences. These interferences can make the mass signal less accurate, even when the instrument is working well. Spectroscopic interferences happen when ions in the plasma have the same mass-to-charge ratio, or m/z, as the analyte ion. This group includes isobaric interferences, polyatomic ion interferences, and refractory oxide ion interferences. Isobaric...

key terms and concepts

Learn how quadrupole, TOF, and ion trap mass analyzers separate ions by m/z, and compare their resolution, sensitivity, and detection methods.

Quadrupole, TOF, and Ion Trap Analyzers | JoVE K12

analytical chemistry

JoVE Core Analytical Chemistry simplifies complex chemical principles by breaking them down into clear, engaging animations, making topics from SI Units to NMR spectroscopy more accessible and straightforward. Additionally, the scientist-in-action videos highlight the application of these concepts in real-world research conducted in laboratories globally.

Quadrupole, TOF, and Ion Trap Analyzers

Description

Transcript