1

Ionic Liquids in

Separations & Mass Spectrometry

Zachary BreitbachUniversity of Texas at Arlington

AZYP, LLC

May 2011

2

RTIL Structures

Common Cations

Anions

BMIM Bm4IM

•PF6‐

•BF4‐

•Cl‐

•CF3SO3‐ (TFO)

•N(CF3SO3)2‐ (NTf2)

3

RTILs as GC Stationary Phases

RequirementsHigh thermal stability (250°C and above)High viscosityHigh wetability on fused silica capillary columnsProduces symmetrical, efficient peaks

Note that the ILs on the previous slide do not meet all these requirements!

4

IL 19

IL 18 (IL 76)

N

HNHN

NH

O

O

O

C5H10

C5H10

C5H10

N

N

N

N

NN

3NTf2-

N

HNHN

NH

O

O

O

C5H10

C5H10

C5H10

P

P

P

3NTf2-

IL 100

IL 15

IL 4

N N(CH2)12 N N

2NTf2-

N N(CH2)5 N N

2NTf2-

P(CH2)13

NTf2-

5

IL 82

IL 59

MIM‐PEG

N N(CH2)12 N N

2NTf2-

P(CH2)12

P

2NTf2-

N N

2TfO2-

O O O N N

MIM‐PEG

salt treated, 15 m

IL 94

IL 126

N N

2TfO2-

O O O N N

N N

2TfO2-

O O O N N

N

HNHN

NH

O

O

O

C5H10

C5H10

C5H10

P

P

P

3TfO2-

6

Figure 2‐Thermal stability diagram for four of the ILs tested in this analysis.  The plot shows the bleeding temperatures for the IL stationary phases, which corresponds to their decomposition or volatilization temperatures.  The thermal stability test was done with 1 ml/min He flow, a temperature ramp of 3°C/min, and FID detection.  Compounds A1, A4, A3, and D3 represent ILs trihexyl(tetradecyl) phosphonium chloride, trihexyl(tetradecyl) NTf2, trihexyl(tetradecyl) TfO, and 1,12‐Di(tripropyl‐phosphonium)dodecane 2NTf2, respectively.

77

Incremental Max Temperature Studies, 

Supelcowax 10 vs IL‐36k' (Nap) vs Temperature

5.00

7.00

9.00

11.00

13.00

Initial ru

n 200210220230240250260270280290300310320330340350

Temperature (for 4 hours)

k' (N

ap)

k' (IL-36)k' (Wax-10)

88

Air Carrier Gas Experiment (needed for field instruments, but O2 & H2O are problematic)

• SLB‐IL59 column: 30m x 0.25mm x 0.20m, df• Carbowax column: 30m x 0.25mm x 0.25m, df

Oven:• Programmed Test Mix:: 50 oC(2 min) to 200 oC (15 min) at 4 

oC/min• Injector Temp: 250 oC• Detector Temp: 250 oC• Column Dimension: • Split: 50:1 • Injection volume: 1l• Air: constant air pressure 16psi

9

9

Air as a Carrier Gas 

• Programmed Test Mix (Carbowax Column)

0 10 20 30Time (min)

•1st injection

•After 100 injections

•After 200 injections

10

Air as a Carrier Gas with IL Column 

• Programmed Test Mix (SLB‐IL59 Column)

•After 100 injections

•After 200 injections

0 10 20 30Time (min)

11

Air as a Carrier Gas, cont. 

• Programmed Test Mix (SLB‐IL59 Column)

•After 200 injections

•After 300 injections

0 10 20 30 40 50Time (min)

1212

GC Polarity Scale

•GC column polarity scale•0 = squalane (considered the least polar GC stationary phase)•100 = TCEP (considered the most polar GC stationary phase)

0 50 100

280°CWax (PEG)

310°C‐20  ‐1701  ‐35  ‐50

360°C‐1  ‐5

275°C  250°C  140°C‐2331  ‐2560  TCEP

Non‐Polar Intermediate Polar Polar Highly Polar

2515

Range of Alternative Polarities possible from Ionic Liquid GC

Where do current ILs fit on this scale?

13

Figure 6.  GC x GC separation of diesel fuel on the (a) IL x HP‐5 column combination, (b) the DB‐Wax x HP‐5 column combination, and (c) the HP‐50+ x HP‐5 column combination.  Both the IL x HP‐5 and DB‐Wax x HP‐5 configurations generated distinct chromatographic regions for the saturated hydrocarbons, monoaromatics, and diaromatics.  The HP‐50+ x HP‐5 configuration had nearly complete separation of the saturated hydrocarbons from the aromatics, but no clear separation of the aromatics into monoaromatic and diaromaticregions.

Anal. Bioanal. Chem. 390 (2008) 323‐332.

IL columns are  the most orthogonal known

14

Water Analysis Methods

1. Karl Fischer methods

2. Near IR

3. GC  (packed column, molecular sieve)

4. Solvatochromic

5. 19F‐NMR

15

Water detection by GC1. Water cannot degrade the stationary phase

2. Water must produce a reasonably sharp, efficient peak

3. Water must be well separated from all solvents (matricies)

4. Analysis times should be short

5. Results must be highly accurate and reproducible

6. Effective for any concentration from <1ppm to >99%

16

MIM‐PEG

IL 942700

IL 107

Stationary phase Efficiency / mShape of Water peakAt 70 0C

N N

2TfO2-

O O O N N

N N

2TfO2-

O O O N NHOOH

(Dibutylphthalate, 150 C)

1200

N

HNHN

NH

O

O

O

C5H10

C5H10

C5H10

P

P

P

3TfO2-

2300

(Dibutylphthalate, 185 C)

(Dibutylphthalate, 150 C)

17Figure 2: Separation of water from CH2Cl2 in examined columns at 80 0C.

HMIM‐PEG TPT

COMMERCIAL

CH2Cl2

H2O

CH2Cl2

H2O

H2O

CH2Cl2

DMIM‐PEG

H2O

CH2Cl2

2 4 6

Time (min)

2 4

Time (min)

2 4 6

Time (min)

2 4 6

Time (min)

18

Limits of detection (DL) and limits of quantitation (QL) of water in the evaluated columns.

Solvent HMIM-PEG TPT DMIM-PEG

DL/ng QL/ng DL/ng QL/ng DL/ng QL/ng

MeOH/A1 3.6 10.9 4.0 12.0 4.1 12.4

THF/C2 2.1 6.3 5.6 16.9 3.0 9.0

1”A” indicates that acetone was used as the internal standard. 2“C” indicates that acetonitrile was used as the internal standard.

These  DLs are 5,000 times lower than the same samples done by Karl FischerTitration.Also the KFT takes as much as 5 ml of sample.

19

SampleHMIM-PEG TPT DiMIM-PEG

Water

(ppm) RSD%

Water

(ppm) RSD%

Water

(ppm) RSD%

Acetic acid 420 1.0 410 5.9 440 5.0

Acetone 2380 3.8 2380 6.1 2520 0.3

Acetonitrile 103 3.0 98 6.9 103 2.7

Anisole 990 2.6 990 3.5

Benzene 18 2.4 17 8.4 21 9.5

1-Butanol 1190 3.6 1150 5.8

2-Butanol3530 2.6 3380 2.3

2-Butanone 730 3.7 760 1.2 710 5.8

t-Butyl alcohol 2130 1.9 2010 6.2 1950 4.0

Carbon tetrachloride36 3.7 38 4.4 36 5.7

Chlorobenzene38 9.6 42 8.9 39 3.1

1-Chlorobutane27 5.5 23 5.0 28 3.7

Chloroform 155 2.3 153 5.1 162 6.3

2-Chloropropane120 4.0 113 5.3 125 4.2

Cyclohexane18 9.7 21 7 20 3.5

Cyclohexanone

20

1,2-Dichloroethane160 6.9 150 13.7 140 2.4

Diethyl ether400 7.6 420 1.6 390 6.4

Di(ethylene glycol) ethyl

ether 950 4.3 970 9.5 930 2.1

Dimethyl- formamide (DMF) 594 4.0 606 4.9 614 6.2

Dimethyl sulfoxide (DMSO) 773 2.9 800 4.4 820 5.0

Dioxane3800 4.0 3700 3.5 3900 2.3

Ethanol890 2.0 880 3.8 880 2.2

Ethyl acetate370 2.8 365 3.9 370 1.4

Heptane18 6.3 17 8.7 16 8.7

Hexane14 5.3 17 9.5 16 9.0

Methanol209 7.1 198 4.6 203 5.0

Methyl t-butyl ether (MTBE)1900 1.1 1800 6.1 1900 6.6

Methylene chloride48 8.2 52 6.3 47 7.3

Nitrobenzene119 2.5 109 8.5 117 3.9

21

Octane13 8.0 17 10.0 14 5.1

1-Octanol190 4.6 210 7.0 190 5.6

Pentane16 3.4 18 9.6 15 4.8

Petroleum ether (ligroine)

16 3.9 19 6.1 17 4.6

1-Propanol308 4.0 285 3.2

2-Propanol180 3.9 171 2.4 162 3.0

Pyridine 910 4.6

Tetrahydrofuran (THF)110 6.0 108 5.8 117 8.1

Toluene31 4.2 29 5.0 32 4.6

Triethyl amine56 0.3 57 0.2 57 6.7

o-Xylene74 7.7 76 4.9

m-Xylene22 7.9 24 0.6

p-Xylene23 9.2 26 0.2

22

Time (min)2.5 5 7.5 10 12.5 15 17.5 20

THF ACNIPA

EtOHPrOH

Acetone

BuOH

Unknown impurityin H2O H2O

BuOHACN

PrOH

EtOHAcetone

IPATHF

Unknown impurityin H2O

A)

B)

Fig. 6

Example of the separation of organic solvents in water using ionic liquid based stationary phase. Chromatogram A: DMIM‐PEG; 40°C; 0.2ml injection; thermal conductivity detector (all solvents: 100mg/kg)Chromatogram B: DMIM‐PEG; 40°C; 0.2ml injection; flame ionization detector (all solvents: 5mg/kg)

23

GENERAL  PROPERTIES  of  MALDI  MATRICES

a) They must dissolve (liquid matrix) or co‐crystallize (solid matrix) with the sample.

b) They must strongly absorb the laser light (e.g., 337 nm).

c) They must remain in the condensed phase under high vacuum conditions.

d) They must stifle both chemical and thermal degradation of the sample.

e) They must promote the ionization of the sample via any number of mechanisms.  

IONIC  LIQUIDS  FOR  MALDI‐MS

24

25

MALDI mass spectra of the three oligonucleotides (d(pT)10, d(pC)11, and d(pC)12) in different matrixes: (a) 3‐HPA + 10% ammonium citrate, (b) ionic solid 21, and (c) ionic solid 26.  Spectra obtained cumulating 100 UV 237 nm laser shots.  For the three experiments, the oligonucleotide‐to‐matrix molar ratio was 1:500000 and the laser fluence was the same (attenuation 10).  The signal strength is expressed in arbitrary units corresponding to the accumulation of 100 shots on a good spot.  The 3‐HPA scale (top spectrum) differs 8 times from that for the two salts (bottom spectra). 

26

Detection of Catalase (Monomer=60,000 Da)

0 0

0.5

1.0

1.5

2.0

4x10

Inte

ns. [

a.u.

]

0 0

0.5

1.0

1.5

2.0

4x10

Inte

ns. [

a.u.

]

0 0

0.5

1.0

1.5

2.0

4x10

Inte

ns. [

a.u.

]

50000 100000 150000 200000 250000 300000

[M + H]+

[M + H]+

[M + H]+[2M + H ]+

[3M + H]+[4M + H]+

[5M + 2H]2+

NOH

O-

O

IMTBA CHCA

H N+

NOH

OH

O

α‐cyano‐4‐hydroxycinnamic acid: CHCA

Sinapinic acid

O

OH

O

OH

O

2727

28

Corona discharge more prevalent in negative mode Leads to less stable Taylor cone and unstable signal Higher background noise Increased chance for arcing Electron scavenging gases and/or halogenated solvents

used to inhibit corona discharge

28

29

Using cationic additives as ion-pairing agents for MS First application was performed to detect trace amounts of

perchlorate. Expand to additional ions.

1+2++ ClO4

-

m/z +145

(MW 290)

m/z +389

m/z - 99

ClO4-

NNN

N 9

 

NNN

N 9

29

30

Can select cation to place complex in a higher mass region, where there is less noise.

Can bring smaller ions out of low mass cutoff (LMCO=50 for LXQ)

May help distinguish between ions of same M/Z (35ClO4

- vs. H34SO4-)

30

31

Three different ways to detect ions1) Full Scan2) Selective-Ion Monitoring3) Use MS/MS

- Trap m/z of complex- Excite this m/z to break complex- Monitor m/z of fragment of dication

1+N

NNN 9

1+

ClO4-

 

NNN

N 9

31

32

ESI‐MS Analysis 

Sample Sol’n

[Dication]2+

[Anion]-

[Dicat+Anion]+

MS

LC PumpH20/MeOH

LC Pump40 uM Additive in H20

LC ColumnFinnigan LXQ

33Soukup-Hein et al. Anal. Chem. 2007, 79, 7346-7352.33

34

RT: 0.00 - 18.00 SM: 15G

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17Time (min)

0

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Rel

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unda

nce

NL:0m/z= 57.50-58.50 MS AnionmixtureMS_040207dNL:2.46E3m/z= 148.50-149.50 MS Genesis AnionmixtureMS_040307eNL:1.11E4m/z= 156.50-157.50 MS Genesis AnionmixtureMS_040307eNL:1.51E4m/z= 279.50-280.50 MS Genesis AnionmixtureMS_040307eNL:2.01E3m/z= 412.50-413.50 MS Genesis AnionmixtureMS_040307e

RT: 0.00 - 17.99 SM: 15G

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17Time (min)

0

5

10

15

20

25

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Rel

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bund

ance

NL:4.62E3m/z= 347.50-348.50 MS Genesis AnionmixtureMS_040307cNL:4.60E3m/z= 438.50-439.50 MS Genesis AnionmixtureMS_040307cNL:1.15E4m/z= 446.50-447.50 MS Genesis AnionmixtureMS_040307cNL:9.83E3m/z= 569.50-570.50 MS Genesis AnionmixtureMS_040307cNL:7.46E3m/z= 702.50-703.50 MS Genesis AnionmixtureMS_040307c

0 3 6 9 12 15Time (min)

100

80

60

40

20

00 3 6 9 12 15Time (min)

100

80

60

40

20

0R

elat

ive

Abu

ndan

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Rel

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bund

ance

SCNArea: 7.3 E5S/N: 138

TFOArea: 8.9E5S/N: 88

BZSNArea: 2.9E6S/N: 204

NTF2Area: 1.4E5S/N: 30

PFOAArea: 1.0E5S/N: 162

TFOArea: 4.9E5S/N: 67

BZSNArea: 3.6E5S/N: 31

NTF2Area: 2.5E5S/N: 32

PFOAArea: 4.0E4S/N: 26

SCN

(B)(A)

Figure 2: A comparison of the chromatographic separation and sensitivity of 5 anions on a Cyclobond I column detected in the (A) positive and (B) negative SIM modes. The mass injected in (B) is 10x that of (A) for SCN, TFO, and BZSN, 5x for PFOA, and the same for NTF2. The mass injected in (A) is :1.43 ng SCN, 9.92 ng TFO, 1.16ng BZSN, 0.68 ng NTF2, and 1.30 ng PFOA. The column was equilibrated for 15 minutes with 100% Water with a linear gradient to 100 % MeOH beginning at 3 minutes and complete at 9 minutes. Flow rate was 300 μL/min. In (A) the dicationic salt solution (40 μM in MeOH) was added post-column at 100 μL/min where as in (B) it is methanol only. SCN: thiocyanate; TFO: triflate; BZSN: benzenesulfonate; PFOA: perfluorooctanoic acid; NTF2: trifluoromethanesulfonimide.

Positive ion mode Negative ion mode

Soukup-Hein, et.al. Anal. Chem. 2007, 79, 7346-52

10x the mass

injected in

positive mode

34

35

Terminal Charge Group Linkage Chain Length Linkage Chain Type Different Structures

35

36

N+

N+

OH

N+

N+

N+

N+

O

O

OH

OH

CH3CH3

CH3 H

OMe

MeO 

N+

NOH N

+N OHO O O

  N+

N CH2CH2(C F2)4CH 2CH2 N+N

 N

+N N

+N

 

P+

P+

P+

P+

O O O

N+

N(CH2)5N+

P+

(CH2)5N+

  N+

N(CH) 9N+N

 

(CH2)3 P+

P+

 

(CH2)5 P+

P+

 

(CH2)9 P+

P+

  N+

N(CH2)3N+N

  N+

N(CH2)5N

+N N

+(CH2)5N+

N+(CH 2)5N

+

(CH2)5 N+

N+

(CH2)12 N+

N+

N+

N( CH2)5N+

N

 N

+N

(CH2)5N+

N

 N+

N(CH2)5 OHN+

NOH

36

J Am Soc Mass Spectrom 2008, 19, 261–269

37

 RR

R

RR

R

 

NRR

R

A B

CR=

 NN

+2)

R= 

NN+1)

R= 

NN+

OH3)

R= P+6)

R= N+5)

C1C2C3C4C5C6C7

A1A2A5A6

B1B2B4B6

Trications Core Charged Groups

 N

NNR R

OO

N

R

O

5

5

5

D

D2D6

R=4) N N

NH+

NR=7)

37Anal. Chem. 2008, 80, 2612-2616

38

 RT: 0 .00 - 5 .01 SM : 7G

0.0 0.5 1.0 1 .5 2.0 2.5 3.0 3.5 4 .0 4.5 5.0

Tim e (m in)

0

5

10

15

20

25

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anc

e

AA: 387S N: 6

N L:1 .02E 2TIC MS G enes is

N egH exC lP d_102607b

Time (min)

100

80

60

40

20

0

Relative Abundance

0 1 2 3 4 5

5 ngS/N: 6

RT: 0.00 - 5. 02 SM: 7G

0.0 0.5 1.0 1. 5 2.0 2.5 3.0 3.5 4.0 4 .5 5.0Tim e (m in)

0

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AA: 7969S N: 35

NL:1.45E3TIC MS Gen esi s TricatL_HCP_102607

0 1 2 3 4 5Time (min)

100

80

60

40

20

0

Relative Abundance

500 pgS/N: 35

RT: 0.00 - 5.01 SM: 7G

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4 .5 5.0Tim e (m in)

0

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AA: 13 2SN: 3

NL:2.71E1TIC MS Gen esi s Neg OBDSA_102 607c

0 1 2 3 4 5Time (min)

100

80

60

40

20

0

Relative Abundance

5 ngS/N: 3

RT: 0 .00 - 5 .02 SM : 7G

0.0 0.5 1.0 1 .5 2.0 2.5 3.0 3 .5 4 .0 4 .5 5 .0Tim e (m in)

0

5

10

15

20

25

30

35

40

45

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tive

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nda

nce

AA: 20004S N: 56

N L:2 .74E3TIC M S G enes is TriC atB _12907

0 1 2 3 4 5Time (min)

100

80

60

40

20

0

Relative Abundance

500 pgS/N: 56

Hexachloroplatinate

(Trication A6)

o-Benzenedisulfonate

(Trication B1)

Positive Negative

2-

S

SO

OO-

O-

OO

38Anal. Chem. 2008, 80, 2612-2616

39

nn

N+

CH2NN N

+ CH2 NN

+CH3CH3

nn

N+

CH2NN N

+ CH2 NN

+CH3 CH3

nn

N+

CH2NN N

+ CH2 NN

+

nCH2P

+

CH3

CH3

CH3

N N+ CH2 P

+

CH3

CH3

CH3

n

Linear Tricationic Reagents

39Anal. Chem. 2008, 80, 8828–8834

40

Figure 2. Comparison of the detection of sulfate in the positive mode using tricationic ion-paring reagents D3 (I) and E2 (II). Note, Sulfate has a M/Z of -48 and is completely undetectable in the negative ion mode.

I

II

500 pgS/N: 21

500 pgS/N: 3

nCH2P

+

CH3

CH3

CH3

N N+ CH2 P

+

CH3

CH3

CH3

n

n=10

R

R

R

R= tripropylphosphonium

40

41

N+N

N+

N+

N

N

LTC 1

LTC 2

TTC 1 TTC 2

41

42

S/N=5

500pg

N+

N

N+

NN

+

N

N+

N

43