 정성 및 정량분석

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9장 Mass Spectrometry

based on ionization of gas phase molecule

followed by analysis of the masses of the ions produced

 일반 특성

 정성 및 정량분석

 유기 및 무기물

 can measure ~ 75 elements

 rapidly evolving technology

 expensive and complex

 질량분광법  질량분석법

사용되는 분야?

 Biotechnology:

analysis of proteins, peptides, oligonucleotides

 Pharmaceutical:

drugs discovery, combinatorial chemistry, pharmokinetics, drug metabolism

 Clinical:

neonatal screening, haemoglobin analysis, drug testing

 Environmental:

water, food, air quality (PCBs etc)

 Geological:

oil composition

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정성확인 – basic principles

 Samples are ionized

some fragmentation usually occurs

 Sample components (and fragments) are separated based on mass-to-

charge ratio (m/z)

 Output is a mass spectrum

Relative abundance of the natural isotopes

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스펙트럼:

y축 (ion intensity), x축 (m/z)

 molecular ion peak (M⁺): MW of singly charged molecules

 fragment peak: less than MW of singly-charged molecules

 base peak: most intense m/z

질량분석법 적용

1. 정성 확인

- identify organic compounds

2. 정량 분석

- elemental analysis

- molecular compounds (GC-MS)

3. Isotope ratio

- 206Pb/²⁰⁸Pb

4. Detector in “hyphenated” systems

- GC-MS - LC-MS

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정량적 확인

 Two main peaks are observed

Masses 12 and 16

 The mass 16 peak is twice the size of the mass 12 peak

There are two oxygen atoms for every carbon atom in CO₂

 Several minor peaks are observed at masses of 13, 17, and 18

Minor isotopes of C and O

Mass Spectrum of CO₂ (g)

Relative Abundance (%)

100

50

0

12 14 16 18

Mass-to-charge ratio (m/e^-) 12-C

16-O

13-C 17-O 18-O

Relative abundance of the natural isotopes

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 중요한 특징중의 하나는 다른 기기와 다르게 isotopes 를 파악할 수 있다 (neutron/중성자 다른 것)

 질량이 다르고 대부분 화학적 성질 같은 것

 Chlorine 35와 37 은 3:1 정도 존재

 단백질이나 고분자의 경우에는 탄소가 많기 때문에 점차적으로 차이가 많이 남

 초기 탄소 12.. 점차 탄소13을 함유하고 있는 피크 (특히 생체고분자 분자량 5000일지라도 굉장히 다양한 복잡한 피크가 나타남)

 Carbon 13 on the other hand, is present at only 1.1% of the abundance of carbon 12.

 However, in organic molecules there may be large numbers of carbon atoms present in the molecule. As the molecule increases in mass and possibilities arising from the different isotopes of the

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Qualitative Identification

 가장 큰 피크:

base peak

 The base peak is used to set 100%

relative abundance

 Ions created out of the unfragmented compound are

called the parent ion

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기기 장치

Sample

Introduction System

Ion Source

Mass

Separator Detector

Signal Processor

Computer Interface (Readout) Vacuum System

Volatilize sample

(g, l, s)

Sample ions + fragments

(m/e^-)_i

current

DC Voltage

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기기 기본 구성

1. sample introduction system (시료주입)

volatilizes the sample and introduces it to the ionization chamber under high vacuum

2. ion source (이온화 장치)

ionizes the sample (fragmentation may occur) and accelerates the particles into the mass analyzer

3. mass analyzer (or mass separator)(질량분리)

separates ionized particles based on their mass-to- charge ratio (m/e^-)

4. detector - ion collector

monitors the number of ions reaching detector per unit time as a current flow

5. signal processor

amplifies the current signal and converts it to a DC voltage

6. vacuum pump system

a very high vacuum is required so that the generated ions are not deflected by

collisions with internal gases