Name: mass analyzers and ion separation
Uploaded: 2024-04-04T10:51:34.000Z
Duration: 1 min 13 s
Channel: JoVE

일반적인 질량 분석기에는 자기 섹터(magnetic sector), 이중 초점(double-focusing), 사중극자(quadrupole), 비행 시간(time-of-flight) 및 이온 트랩 분석기가 포함됩니다.
모든 질량분석기의 성능은 분해능으로 평가할 수 있으며, 이는 유사한 질량 대 전하 비율로 이온을 구별하는 능력을 설명합니다.
분리능은 피크의 공칭 m/z 값과 피크와 인접한 피크 사이의 가장 작은 분해능 차이의 비율로 표현됩니다. 분석기 분해능에 대한 제한 요소는 분석기 유형에 따라 다릅니다.
예를 들어, 간단한 자기 섹터 분석기는 이온이 자기장에 들어갈 때 거의 동일한 운동 에너지를 가져야 m/z 값이 다른 이온이 다른 궤적으로 안정적으로 편향될 수 있습니다.
따라서 단편화와 가속 중에 발생하는 사소한 운동 에너지 변화조차도 이러한 분리를 덜 효과적으로 만듭니다.
그러나 이중 초점 분석기는 운동 에너지 차이를 보정하기 위해 추가로 적용된 전기장 섹터를 사용하며, 이는 분해능을 최대 10배 증가시킬 수 있습니다.

질량 분석기: 개요

Mass Analyzers: Overview

질량 분석기는 질량 분석의 중요한 구성 요소입니다. 이온화 방에서 기화된 표본은 고에너지 전자빔으로 충격을 받아 라디칼 양이온을 생성하고 추가로 중성 분자, 라디칼 및 양이온으로 조각화됩니다. 일련의 음전하 가속기 접시는 양이온을 질량 분석기로 가속합니다. 질량 분석기는 질량 대 전하(m/z) 비율에 따라 이온을 분리한 다음 이를 검출기로 보냅니다. 일반적인 유형의 질량 분석기에는 자기 섹터, 이중 초점, 사중극자, 비행 시간 및 이온 트랩이 포함됩니다.

자기 섹터 분석기에 자기장이 적용되고 이동하는 전하가 곡선 경로로 편향됩니다. 주어진 자기장의 경우 곡률 반경은 m/z 값에 따라 달라지며 특정 m/z 값의 이온은 검출기로 전달됩니다. 결과적으로 장비의 자기장은 더 넓은 m/z 범위의 이온을 순차적으로 검출기로 전달하기 위해 지속적으로 변화됩니다.

이중 초점 질량 분석기는 정전기 부문과 자기 부문을 조합하여 사용합니다. 이온이 소스에서 빠져나오면 정전기장은 이온 빔을 집중시켜 운동 에너지 확산을 최소화한 다음 이온을 자기 구역으로 유도합니다. 자기 섹터는 편향을 기준으로 이온을 분류합니다. 이러한 빔의 이중 초점은 고해상도를 달성하는 데 도움이 됩니다.

질량 분석기의 분해능은 밀접하게 간격을 둔 두 개의 질량 스펙트럼을 구별하는 능력으로 정의됩니다. 단위 분해능은 하나의 정수 단위의 차이로 질량을 구별하는 기기의 능력을 나타냅니다. 예를 들어, 단위 분해능을 갖춘 기기는 m/z 50과 m/z 51, m/z 100과 m/z 101, m/z 500과 m/z 501을 구별할 수 있습니다. 일반적으로 상업용 분광계의 분해능은 500~500,000 범위입니다.

일반적인 질량 분석기에는 자기 섹터(magnetic sector), 이중 초점(double-focusing), 사중극자(quadrupole), 비행 시간(time-of-flight) 및 이온 트랩 분석기가 포함됩니다.
모든 질량 분석기의 기능 ...

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

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, double-focusing, quadrupole, time-of-flight, and ion trap analyzers. In a magnetic sector analyzer, a magnetic field bends the moving ions into a curved path. The radius of that curve depends on the ion's m/z value. By changing the magnetic field, the instrument can pass ions with different m/z values to the detector one after another.

A double-focusing mass analyzer combines an electrostatic sector and a magnetic sector. As ions leave the source, the electrostatic field focuses the beam and reduces the spread in kinetic energy. The beam then enters the magnetic sector, which separates the ions by deflection. This double-focusing design helps the instrument achieve high resolution.

Resolution describes how well a mass spectrometer can tell apart two closely spaced mass spectra. Unit resolution means the instrument can distinguish masses that differ by one integer unit, such as m/z 50 and 51, or 100 and 101, or 500 and 501. In commercial spectrometers, resolution is generally in the range of 500 to 500,000.

Mass Analyzers and Ion Separation

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 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, 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...

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

See how mass analyzers separate ions by m/z, how magnetic sector and double-focusing designs work, and what resolution means in mass spectrometry.

Mass Analyzers and Ion Separation | 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.

Mass Analyzers and Ion Separation

Description

Transcript