GC/MS 의 원리 및 이론

Cryo system with GC/MS for ppt level Analysis

GC/MS 의 원리 및 이론

부경대공실관 VOCs/ 냄새분석실

부경대학교 공동실험실습관 VOCs/ 냄새분석실

Gas Chromatograph/Mass Spectrometer

Source

Measure the masses of individual molecules & atomswhich are converted into gas phase ions in terms of their mass to charge ratios

Inlet Analyzer Detector Data System

solidliquidgas

ionization sort ions by m/z

convert into gas(chromatographic separation)

mass spectrum

What is Mass Spectrometry?



▣ ▣ GCGC 의 기본 구성과 기능의 기본 구성과 기능



▣ ▣ 시료주입기와 주입방법시료주입기와 주입방법

1. 섬광기화 직접법

2. 섬광기화 분할법 (split)

3. 섬광기화 비분할법 (splitless)

4. 섬광기화 냉각법

5. 온도프로그래밍 기화법 (PTV)

6. 냉각 온 - 컬럼 주입법 (OCI)

7. 기타



▣ ▣ 컬럼오븐컬럼오븐

분리도와 머무름 재현성 향상을 위해서

1. 설정온도와 실제온도의 일치

2. 최저 및 최고 작동 온도의 범위의 확장

3. 오븐의 가온 · 냉각 속도가 정확

4. 오븐 온도의 평형 시간의 단축

5. 설정된 온도가 주기적인 변동없이 안정



▣ ▣ 컬럼온도에 따른 분리도 컬럼온도에 따른 분리도

30℃ 등온분석

100℃ 등온분석

30~200℃승온분석



▣ ▣ 검출기의 종류검출기의 종류

1. 이온화 검출기 (ionization detector) 불꽃이온화 검출기 (flame ionization detector;FID) 열이온화 검출기 (thermionic ionization detector;TID) 광이온화 검출기 (photo ionization detector;PID) 전자포획 검출기 (electron capture detector;ECD)

2. 물리적 성질 검출기 (bulk physical detector) 열전도도 검출기 (thermal conductivity detector;TCD)

3. 광학 검출기 (optical detector) 불꽃광도 검출기 (flame photometric detector;FPD) 원자방출 분광 검출기 (atomic emission detector;AED)



What is the Mass Spectrum?

mass to charge ratio

# o

f io

ns



Inlet + Source : 시료도입 및 이온화 방법에 따라

EI, EI/DIP, CI, DCI, FD, FI, TI, FAB(LSIMS), LD, ESI, APCI, MALDI,GC-MS, LC-MS, CE-MS, etc.

Analyzer : 질량분석관에 따라

Sector, TOF, Q(quadrupole mass filter, 2D-Q)Quadrupole IT(ion trap, 3D-Q), ICR (FTMS)Hybrid MSs (Sector-TOF, QqTOF, TOF-TOF, QqQ, IT-TOF, etc)

Diverse Mass Spectrometric Systems



Reservoir Inlet

DIP

FAB, LD, MALDI

Non-volatileVolatile

GC/MS

Thermally Stable Thermally labile

GC/MS

ESI, MALDI

Choice of MS Method I

ESI/APCI (but should be soluble in ESI/APCI compatible solvents)

FAB, APCI



Choice of MS Method II



Quantitation

InformationfromMS

Molecular Weight& Elemental Composition

molecular ion → molecular mass (M+Na)+=897 → M=874accurate mass → elemental composition 897.4976 → C48H74O14Naisotopic distrib’n → elemental composition

source of the sample

Molecular StructureFrom fragmentation

Non-covalent InteractionNon-covalent adduct(Ab-Ag, host-guest)

Information from Mass Spectrometry



Advantage of MS detector

Information of chemical structure Identification of target compound Determination of molecular weight High sensitive and rapid analysis



Identification

m/z

Retention time

Chromatogram

MS

Spec

trum



Configuration of GCMS Configuration of GCMS

Mass Spectrometer

Gas Chromatograph

Interface

Ion source box

Data Store



Flow Chart of GC-MS

Sample

Inlet System

Ion Source

Vacuum System

Mass Analyzer

Detector

Signal Processor

Print Out

GC Direct



MS analyzer

Magnetic sector type (sector type) Quadrupole type Time of flight type (TOF type) Ion Trap type

Quadrupole type of GCMS is very popular.



Schematic of a Quadrupole MS systemSchematic of a Quadrupole MS system

Generation

Introduction

Selection

Detection



Hardware structure of QP/MS



Ion Source Box- Increased ionization efficacy -

Ion Source Box- Increased ionization efficacy -

Interface

Filament

Ion source box

Conventional ion source

QP2010 ion source High luminosity ion source



Ion Source Box Ion Source Box

Extractor : This device can draw ion generated into the ion source box.

from GC

To QP

QP2010



Optimum adjustment of the Lens system

QP

Software can optimize lens voltage in order to introduce more ions to Quadrupole.

X



Quadrupole Rod - Minimize losses in transit to the Quadrupole -

Quadrupole Rod - Minimize losses in transit to the Quadrupole -

Main RodSpecific ion only can be passed by the electronic field into Quadrupole Rod which is controlled by PC.

Pre Rod

From ion sourceTo detector



rotary pump

Vacuum systemVacuum system- Minimize losses in transit to the Quadrupole -

turbo molecular pump [260 L/sec X 65 L/sec]

Dual turbo pumping system



Low-noise Dynode multiplier - Increased detection of created ions -

EMDetector

Conversion dynode

Low noise detector unit



High Sensitivity High Sensitivity

Octaflouronaphthalene, 1pg : S/N > 60

Octafluoronaphthalene, 1pg : S/N > 30

QP-2010

QP-5050



Modes of Ionization

EI : Electron Impact Hard Ionization, High Energy Structural information

CI : Chemical Ionization Soft Ionization, Low Energy Molecular weight information



Ionization techniques available for GC/MS

Electron Impact Ionization (EI)

Positive Chemical Ionization

(PCI)

Negative Chemical Ionization

(NCI)



Electron Impact Ionization (EI)Electron Impact Ionization (EI)

e-e-Sample

from GC

filament

++

+ +

Fragment ion

QPe-e-e-


Gas Chromatograph/Mass SpectrometerElectron Impact Ionization

(EI)

Thermal electrons (ca. 70 eV) hit molecules and ionize them. Ample fragment ions = ample structural information “finger print”

EI spectrumMethylstearate M.W. 298



Positive Chemical Ionization (PCI)


from gas cylinder

filament

e-e-

e- e-e-

QP

CH4 CH5

+

C2H5+

Sample from GC

H+

-CH4

[M+1]-C2H4




Reagent gas molecules are ionized first. Sample molecules are ionized mainly by “proton

transfer”. Quasi molecular ions easily produced useful for

molecular weight verification.

+

PCI spectrumMethylstearate M.W. 298



Comparison of EI and PCIComparison of EI and PCI

EI mode

PCI mode

Fragment

Molecular weight



Negative Chemical Ionization - NCI -Negative Chemical Ionization - NCI -

filament

e-e- e-e-

Reagent Gas

Sample

NCI for highest sensitivity for electrophilic compounds

Sample



Negative ion formation by electron capture (associative resonance capture)

MX + e- (~0 eV) MX-.

X: positive electron affinity part

CH4

e-

MX

CH4+

CH3

+H

CH4

CH4

CH4

e-

MX-



Advantages of negative chemical ionization

Ion formation by electron capture

High sensitivity Close to GC-ECD sensitivity

High selectivity



Application fieldfor negative chemical ionization

Environmental chlorinated pesticides phosphorus pesticides PCB etc.

Life science Drugs, steroids, bile acids



Measurement Mode

Scan Mode SIM Mode (Selected Ion Monitoring)

mas

s n

um

ber

mas

s n

um

ber

Time Time[Scan] [SIM]

(Qualitative)(Qualitative) (Quantitative)(Quantitative)



Scan Mode

m/z

Retention time

TIC : Scan Mode

72

54

152



SIM Mode

Retention time

m/z=72 m/z=152 m/z=54

Higher Sensitivity than Scan Mode.For quantitation purpose



Adjustment of MS

All adjustment of the instrument can be carried out by Windows Software.

Sensitivity adjustment Resolution adjustment Correction of mass number Correction of relative intensity



MS TuningMS Tuning

PFTBA(perfluorotributylamine) is use for MS tuning.



PFTBAPFTBA

relative

m/z intensity

69 100.0131 26.0219 32.0414 2.0502 2.0614 0.4

CF3 -CF2 -CF2 -CF2 -N -C4F9

C4F9



Direct Injection Mode (DIP)



Operational Precaution Operational Precaution for GCMSfor GCMS



Operation Precautions

• Sample• Pretreated sample• Know amount of components in the sample• Used the smallest appropriate sample volume• For unknown, screen on GC first

• Tools• Wear sanitary gloves when performing any work on IS or analyzer housing• Wipe/clean all the tools with acetone to minimize the background noise



Operation Precautions

•Column• Avoid wide bore, thick film & dirty column.

•Use the recommended standard sample and column to evaluate the system performance.

•Perform preventive maintenance frequently to minimize problems.



Sample Pretreatment

• Filtration• Centrifuge• Extraction

• HSG• Dynamic HS (Purge & Trap)• Static HS



Extraction• LLE

• isolating organic compounds from aqueous samples

• SPE• isolating organic compounds from aqueous samples

• Soxhlet• extracting nonvolatiles and semivolatiles from solid samples

• Sonication• extracting nonvolatiles and semivolatiles from solid samples



Sample Clean-up

• Acid-base partition • Sulfur clean-up• Adsorption column chromatography

• Alumina clean-up• Silica gel clean-up• Florisil clean-up

• GPC



Typical GCMS Problem

•Poor sensitivity•Contamination•Vacuum leak•Dirty ion source•Untrained operator



Troubleshooting for Poor Sensitivity

• Sample • Active• Thermal decomposition

• Injector• Septum leak• Seal rings/graphite damage• Glass insert broken

• GC parameters• Injection parameter

• MS parameters



• Possible Source• Carrier Gas• Injector - Dirty glass insert

- Septum bleed - Graphite bleed• Cleaning solvents• Fingerprints• Plasticizers

• Verify the source by isolating MS from GC• Identify the source

Troubleshooting for Troubleshooting for ContaminationContamination



Typical Contaminants

Mass (M/Z) Compound Classification Potential Source------------------------------------------------------------------------------------------------------------------18, 28, 32, 40, 44 Air H2O, N2, O2, Ar, CO231 Solvent Primary alcohol (MeOH)43, 58 Solvent Acetone77 Bz, Xyl85 Freons91, 92 Tol105, 106 Xyl22, 73, 147, 207, 281, 295, 355, 429 Dimethylpolysiloxane Septum/column41, 45, 55, 57, 71, 85, 99 Hydrocarbon Fingerprint/pump oil149 Phthalates Plasticizers

Documents

GC/MS 의 원리 및 이론