Isranalytica 2006
This presentation is the property of its rightful owner.
Sponsored Links
1 / 13

GCxGC – MS With Supersonic Molecular Beams PowerPoint PPT Presentation


  • 90 Views
  • Uploaded on
  • Presentation posted in: General

Isranalytica 2006. GCxGC – MS With Supersonic Molecular Beams. Maya Kochman and Aviv Amirav. School of Chemistry, Tel Aviv University, Israel. Email: [email protected], [email protected] What is GCxGC?

Download Presentation

GCxGC – MS With Supersonic Molecular Beams

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Presentation Transcript


Gcxgc ms with supersonic molecular beams

Isranalytica 2006

GCxGC – MS

With Supersonic Molecular Beams

Maya Kochman and Aviv Amirav

School of Chemistry, Tel Aviv University, Israel

Email: [email protected], [email protected]


Gcxgc ms with supersonic molecular beams

What is GCxGC?

GCxGC is a gas chromatographic technique which offers superior resolution and separation power compared to conventional gas chromatography (GC). Unlike GC, which consists of only one column, GCxGC consists of two columns, the first is typically non polar, separating the sample according to its volatility, while the second is a polar column for further orthogonal sample separation in time according to its polarity. These two columns are serially coupled, with a modulation mechanism at their junction (thermal or flow).

An important advantage of flow modulation is its ability to tune the second column injection bandwidth with the second column flow rate. As a result, one can choose ~0.3 sec second column injection bandwidth that enables (with a minor traded second GC column separation) the use of quadruple mass analyzer with its limited scan speed such as 10 Hz for 350 amu mass range .

Why Supersonic GCxGC-MS

Supersonic GC-MS provides enhanced molecular ion which is always present together with ultimate amount of mass spectral information. Consequently, Supersonic GCxGC-MS could serve for the provision of ultimate sample information through a combination of best GC separation and MS information techniques.


Gcxgc ms with supersonic molecular beams

Flow Modulation GCxGC Supersonic -MS

Originally developed by John Seeley (Oakland University, Rochester MI) as a low cost reliable GCxGC method.


Gcxgc ms with supersonic molecular beams

Rotary

200 l/min

Turbo

Make-up gas

70 l/s

Calibration

Cluster CI

Pulse

Generator

agent

agent

3-way

solenoid valve

Turbo

injector

250 l/s

EFC

Gas

Y-union

Mixing

1st col

1

2

3

Sample loop

Skimmer

SGE union

4

2nd col

Supersonic

Nozzle

Transfer Line

GC Temp.

GC oven

Fly-Through

Controlled

EI Ion Source

Y-Vu-union connector Restek (2)

Y-Vu-union connector Restek (1)

2nd col

GCxGC-SMB-MS System

EPC (in)

MS

HSI Surface

& Ion Mirror

Y-Vu-unionconnector Restek (3)

SGE Inlet Splitter(4)

1st col

Sample loop B

Sample loop A

0.5 m

megabore


Gcxgc ms with supersonic molecular beams

120

Diesel Fuel Analysis

100

80

A. GCxGC-SMB-MS

60

40

20

0

35

B. GC-SMB-MS

25

15

5

0

5

15

10.00

20.00

Time (min)


Gcxgc ms with supersonic molecular beams

161

176

160

GCxGC-SMB-MS OF DIESEL FUEL

147

104

117

133

91

190

131

300

100

200

100

200

300

154

142

212

182

127

300

226

115

m/z

300

100

200

100

200

Time (min)

4.86

4.90

4.94

4.98

Note the separation according to polarity - thus reduce mass over the time


Gcxgc ms with supersonic molecular beams

Isomers Distribution Information

30

RSIM 212

20

10

0

30

RSIM 226

20

10

30

RSIM 240

20

10

Time (min)

5.00

6.00

7.00

8.00

9.00

Branched hydrocarbons isomers elutes earlier due to their slightly increased volatility but significantly lower melting points hence providing valuable information concerning jet fuels analysis.


Gcxgc ms with supersonic molecular beams

304

179

A. GCxGC-SMB-MS

NIST Hit # 1

Match: 674

R.Match:714

Prob.:93.9

16

152

199

276

137

14

227

57

248

97

12

m/z

100

200

300

10

8

6

4

2

8.40

8.50

8.60

0

Time (min)

304

B. GC-SMB-MS

10

250

NIST Hit # 1

Match: 463

R.Match:551

Prob.:48.2

179

203

218

152

95

278

135

8

100

200

300

62

m/z

6

4

Time (min)

8.50

8.60

8.70

Diazinon 100 ng/g in Coriander

GCxGC helps to clean the mass spectra, and as a result, the chromatographic separation is superior.


Gcxgc ms with supersonic molecular beams

30

35

25

15

5

0

8.52

8.54

8.56

8.58

20

304.1

20

10

305.1

306.1

307.1

10

304.0

305.0

306.0

307.0

308.0

m/z

0

Time (min)

2.00

4.00

6.00

Zoomed Scan (304-308 amu) of Diazinon in

Coriander for Improved IAA

IAA confirmed

NIST identification

IAA Match = 981

Error = 0.149%

Zoomed scan of 100 ppb Diazinon in the narrow mass range of 304-8 amu provides clean baseline with high S/N and enables independent IAA identification of Diazinon plus the conformation of it NIST identification


Gcxgc ms with supersonic molecular beams

355

281

248

73

221

147

m/z

4-

6

1

5

3

107

3

143

4

128

224

175

193

68

2

0.5

3

m/z

2

2

1

1

1

0

0

100

200

300

400

100

200

300

400

0

200

300

400

100

0

Time (min)

248

11.30

11.00

11.20

11.10

355

73

107

281

143

192

3

226

175

m/z

2

1

0

Time (min)

11.10

11.20

11.30

Thionazin 500 ppb in Coriander

NIST-hit #1

Match-569

R.Match-734

Prob-47.8

Thionazin

NIST- no hit


Gcxgc ms with supersonic molecular beams

Pyrene 10 ppb SIM 202 amu

1700

A. GCxGC-SMB-MS

Intensity

100

B. GC-SMB-MS

Intensity

Time (min)

10.90

11.00

11.10

GCxGC provides better sensitivity. In this case the tailing pyrene (due to prolong pesticide analysis) sensitivity was improved by 17 times.


Gcxgc ms with supersonic molecular beams

Flow Modulation Supersonic GCxGC-MS versus Thermal Modulation GCxGC-TOF-MS

Supersonic GC- MS provides enhanced molecular ion and ultimate mass spectral information.

In contrast, GC- MS with Time of Flight MS provides reduced molecular ion and mass spectral information (in comparison with standard GC- MS) due to its use of an ion detector without high voltage conversion dynode, and especially since the fast ion source response time needed for the very narrow thermal modulation GCxGC peaks requires about 80ºC hotter ion source temperature (20ºC for each factor of two faster ion source response time).

As a result, the molecular ion is significantly reduced (in GCxGC-TOF) and is often absent, hence MS based sample identification is compromised.

Supersonic GCxGC- MS provides ultra-fast ion source response time regardless to sample volatility, combined with enhanced molecular ion and confidence level in sample identification.


Gcxgc ms with supersonic molecular beams

  • Flow modulation GCxGC – MS

  • Advantages

  • Unique compatibility with SMB-MS due to the need of high flow rate in the second column.

  • 2. Unique compatibility with quadruple SMB-MS in view of the ability to tune the second column injection bandwidth according to the first and second columns flow rates ratio.

  • 3. The GCxGC-SMB-MS combination benefits from the superior characteristics of SMB-MS:

  • a. Highest Level of Information -Enhanced molecular ion, extended isomer and structural information, exact isotope abundance and elemental information, tunable fragmentation and improved library identification.

  • b. Lowest Detection Limits -Enhanced molecular ion for minimal matrix interference and best RSIM sensitivity for difficult molecules, ion source tailing free peaks.

  • 4. The flow modulator is simple, inexpensive, durable, and has no inherent temperature limitations.

  • Disadvantages

  • Limited first column flow rate of about 1ml/min.

  • Reduced separation in the 2nd column (verses thermal modulation) due to high flow rate.

  • 3. Non-flexible flow modulator in terms of dimensions, flow rates and columns selection, thus tedious to optimize.

  • 4. The modulator, the main core of the system, is constructed from four unions that may generate problems of leaks and dead volume.

GCxGC-SMB-MS Ultimate sample information with 2DGC separation and improved MS


  • Login