Detectin' so you can go Fishin' Seminar. The Purgin ... · The...

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OPTIMIZING FOR VOLATILES ANALYSIS:The Purgin'-Trappin'-Desorbin'-Resolvin'-Detectin' so you can go Fishin' Seminar.


VOC ANALYSIS BY PURGE AND TRAP IS A COMPROMISE


EPA METHOD 502/524 COMPOUNDS1. Dichlorodifluoromethane 21. 1,2-Dichloropropane 41. 1,1,2,2-Tetrachloroethane

2. Chloromethane 22. Dibromomethane 42. Brombenzene

3. Vinyl chloride 23. Bromodichloromethane 43. 1,2,3-Trichloropropane

4. Bromomethane 24. cis-1,3-Dichloropropene 44. n-Propylbenzene

5. Chloroethane 25. Toluene 45. 2-Chlorotoluene

6. Trichlorofluoromethane 26. trans-1,3-Dichloropropene 46. 1,3,5-Trimethylbenzene

7. 1,1-Dichloroethene 27. 1,1,2-Trichloroethane 47. 4-Chlorotoluene

8. Methylene chloride 28. Tetrachloroethene 48. tert-Butylbenzene

9. trans-1,2-Dichloroethene 29. 1,3-Dichloropropane 49. 1,2,4-Trimethylbenzene

10. 1,1-Dichloroethane 30. Dibromochloromethane 50. sec-Butylbenzene

11. cis-1,2-Dichloroethene 31. 1,2-Dibromomethane 51. 1,3-Dichlorobenzene

12. 2,2-Dichloropropane 32. Chlorobenzene 52. p-Isopropyltoluene

13. Bromochloromethane 33. 1,1,1,2-Tetrachloroethane 53. 1,4-Dichlorobenzene

14. Chloroform 34. Ethylebenzene 54. n-Butylbenzene

15. 1,1,1-Trichloroethane 35. m-Xylene 55. 1,2-Dichlorobenzene

16. Carbon tetrachloride 36. p-Xylene 56. 1,2-Dibromo-3-chloropropane

17. 1,1-Dichloropropene 37. o-Xylene 57. 1,2,4-Trichlorobenzene

18. Benzene 38. Styrene 58. Hexachlorobutadiene

19. 1,2-Dichloroethane 39. Bromoform 59. Naphthalene

20. Trichloroethene 40. Isopropylbenzene 60. 1,2,3-Trichlorobenzene


ANALYTES ADDED TO EPA METHOD 524.2

61. Acetone 73. 1-Chlorbutane

62. Diethyl ether 74. Chloroacetonitrile

63. Methyl iodide 75. 2-Nitropropane

64. Acrylonitrile 76. Methylmethacrylate

65. Allyl Chloride 77. 1,1-Dichloro-2-propanone

66. Carbon disulfide 78. 4-Methyl-2-pentanone (MIBK)

67. Methyl-tert-butyl ether 79. Ethylmethacrylate

68. Propionitrile 80. 2-Hexanone

69. 2-Butanone 81. trans-1,4-Dichloropropanone

70. Methacrylonitrile 82. Pentachloroethane

71. Methyl acrylate 83. Hexachloroethane

72. Tetrahydrofuran 84. Nitrobenzene


VOC ANALYSIS SYSTEM

TRAPPURGE

GAS

VENT

DETECTOR

GCCARRIER

GC

PURGE STATE


VOC ANALYSIS SYSTEM

GC

DRAIN

TRAP

PURGEGAS

DETECTOR

GCCARRIER

DESORPTION & DRAIN


PARAMETERS THAT AFFECT PURGE AND TRAP RESULTS

• Purge Flow

• Traps

• Desorb

• Bake


PURGE FLOW

• High

• Low

• Time

• Sparger


SPARGER

PURGEGAS

TO TRAP

PURGEGAS

TO TRAP


GENERAL RECOVERY PATTERNS FOR VOCFor EPA Methods 502\524

3 6 9 1512 18PURGE TIME (min)

20

21

40

60

80

100

COMPOUNDS 8-38

COMPOUNDS 39-55

COMPOUNDS 56-60

COMPOUNDS 61-84

%RECOVERY

GASES 1-7


TRAPSSpecified in EPA Methods

PURGEFLOW TENAX SILICA GEL CHARCOAL

OV1

FREON 12GASES

PURGEFLOW

PURGEFLOW

PURGEFLOW TENAX

VOLATILES &SEMIVOLATILES

TENAX SILICA GEL CHARCOAL

TENAX SILICA GEL


TRAPSSpecified in EPA Methods

DESORBFLOW

DESORBFLOW

DESORBFLOW

PURGEFLOW

PURGEFLOW

PURGEFLOW

PURGEFLOW

DESORBFLOWTENAX SILICA GEL CHARCOAL

OV1

FREON 12GASES

TENAX

VOLATILES &SEMIVOLATILES

TENAX SILICA GEL CHARCOAL

TENAX SILICA GEL


TRAPSSynthetic Charcoal Traps

PURGEFLOW

PURGEFLOW

PURGEFLOW

CARBOPAK C

CARBOPAK B

CARBOXEN 1000

CARBOXEN 1001

C B 1000 1001

B 1000 1001

C B


TRAPS

• Substrates

• Age

• Temperature


TRAPSAge

PURGEFLOW TENAX SILICA GEL CHARCOAL

PURGEFLOW


TRAPSTemperature

SYNTHETIC CHARCOAL TRAPS

MAX 280°C

TENAX TRAPS

MAX 220°C


DESORB

• Carrier Flow

• Water Management

• Time

• Temperature


BAKE

• Time

• Temperature

• Purge Flow


BAKETime Optimization

SAMPLECONCENTRATOR

CYCLE

TIME

Start

Start Start

Start

GC Analysis GC Stop Oven Cool Eqil

Desorb Bake TrapCooling/Stby

Purge

Ti

Tf

GC CYCLE

TEMPERATURE


DETECTORPhotoionization Detector (PID)

• Flow

• Leak Check

• Window


DETECTORElectrolytic Conductivity Detector (ELCD)

• Interface to PID

• Reaction Tube

• Reaction Temperature

• Transfer line to cell


Rinsing the ELCD Transfer Line

0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30

BEFORE

allenv,hp5.0126950a,4,1,0;0

Ti me( minutes)

0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30

AFTER


DETECTORMass Selective Detector (MSD)

What interfaces are being used?


INTERFACES NEEDED FOR THE PURGE AND TRAP SYSTEM

PURGE AND TRAP

COLUMN

COLUMN

DETECTOR


GAS FLOWSOptimal Helium Gas Flows

•Trap Desorb

•Megabore Columns

•Capillary Columns

30-40 mL/min

4-5 mL/min

2 mL/min


MASS SPECTROMETER DETECTORSpecial Questions

• Is cryo being used?

• Is jet separator being utilized?

• Is the column directly interfaced to the MSD?

• Would you like to use the split injector interface?


SPLIT INJECTOR INTERFACEPurge State

Capillary Inlet

Low Dead VolumeUnion

Purge ControlValve

Column HeadPressure ControlTo Detector

1mL/min

SplitVent

Off

Septum PurgeControl

HeCarrier

Vent

Trap25°C

Sample ConcentratorValve Oven

Purge Gas

Total (mass)Flow Controller


SPLIT INJECTOR INTERFACEDesorb State

HeCarrier

Trap180°C

Sample ConcentratorValve Oven

Low Dead VolumeUnion

Capillary Inlet

1 mL\min

To Detector

Purge ControlValve

Column HeadPressureControl

SplitVent

Off

Total (mass)Flow Controller

Septom PurgeControl


PURGEABLES ANALYSIS WITH DB-VRX

1

23

4

5 6

7

8 910,11

12

13

14

15 1617,18

19

20

2122

23

24

26

2728

29,30

31

32

33

34

3536

37

3839

40,41

42

43,44

45

4647

48

49

50

51

52

53

54

55

56

57

58

59,60

61

62

63,64

65 66

67

68

69

70

71

7273

74

7576

77

78

79

80

81

82

83

84

85

86

87

88

89

25

0.00 5.00 10.00 15.00 20.00 25.00

OI Model 4560Purge: 11 min @ 35 ml/min (Helium)Desorb: 1.0 min @ 220° CTrap: (Tenax, Silica Gel, CMS)

Column: 60m x 0.25mm x 1.4 µm, DB-VRXHP 5890 GC Conditions

Oven: 40°C for 3min8°C/min to 90°C, hold 4 min6°C/min to 200°C hold 5 minCarrier: Helium total flow 30 ml/min,septum purge offcolumn 1.0 ml/min (@ 40°C )HP5971A Mass Selective DetectorScan: 35-300 amu (m/z 44 subtracted)Sample: 40 ppb each analyte in 5 ml water


Obstacles To Further Advancement Toward Smaller I.D. Columns

• General dislike for using cryogenic cooling

• Sensitivity

• Sensitivity

• Sensitivity


Sensitivity Limitations Using A Split Injector

Smaller diameter columns require higher split ratios in order to maintain efficient trap desorption

60:1 to 300:1 not uncommon

Higher split ratios give reduced sensitivity


Sensitivity Limitations Using Split Injector High Split Ratio

Older MSD systems were simply not equipped to handle these high split ratios (i.e. - low sample-to-detector quantities)

The Agilent 5973 and 5973N have opened the door for further advancements toward using small diameter columns with Purge and Trap introduction


Improved Sensitivity Of 5973 MSDCompared To 5970, 5971 And 5972

• Reduced source volume

• Improved electron multiplier design

• Optimized quadrapoles


Considerations For Optimum Performance Using 5973 MSD For Volatiles

• The smallest I.D. column possible, within reason: - 20m x 0.18 mm I.D., 1.0 um film

• Use as high of a split as possible

• Use Standard Autotune, not BFB Autotune- Set Entrance Lens to zero- Lower the Repeller slightly


EPA 8260B Using DB-VRXExcellent Resolution Of 114 VOCs In Under 8 Minutes

7.6 Minutes!


Why Would Anyone Want A Volatiles Analysis That Is This Fast?

The Next Advancement In Purge And Trap Analysis• Dual Purge and Trap injection into a single GC/MS instrument

- PT2 from EST- Duet Dual Sampling System from Tekmar

• Allows laboratories to double sample throughput


Break Number 1

For Questions and Answers

Press *1 on Your Phone to

Ask a Question


COLUMN SELECTION

What are my options when choosing the best column for purge and trap analysis?


3 PRIMARY COLUMN CONSIDERATIONS

• Stationary Phase

• Film Thickness

• Length


WHAT ARE WE CHROMATOGRAPHING?

• Polars

• Halogenated

• Gases

• Solids


CHROMATOGRAPHIC RESOLUTION

= 1/4 -1 k

k +1 n

= relative retention

n = theoretical platesk = partition ratio

αααααααα

αααα


RELATIVE RETENTION

Highly selective phase requiredto resolve 60+ analytes

How far apart 2 peaks are

T, phase=ƒα


PARTITION RATIO

Thick films needed to obtain adequateretention of most volatile compounds

Decreasing column diameter increasesefficiency but limits capacity andflow rate

d f , r Tc ,= ƒ


THEORETICAL PLATES

Column length provides high columnhead pressures for dense desorb band

Column length increases run time

, rcn L= ƒ


COLUMN LENGTH

= 1/4 -1 k

k +1Lh

LSince n =

To double resolution you must increase length by 4

h

αα


GC ANALYSIS OF EPA METHOD 502.2 ANALYTES

1. Dichlorodifluromethane2. Chloromethane3. Vinyle Chloride4. Bromomethane5. Chloroethane6. Trichlorofluoromethane7. 1,1-Dichloroethene8. Methylene chloride9. trans-1,2-Dichloroethane

10. 1,1-Dichloroethane11. cis-1,2-Dichloropropane12. 2,2-Dichloropropane13. Bromochloromethane14. Chloroform15. 1,1,1,-Trichloroethane16. Carbon tetrachloride17. 1,1-Dichloropropene

35. m-Xylene36. p-Xylene37. o-Xylene38. Styrene39. Bromoform40. Isopropylbenzene41. 1,1,2,2-Tetrachloroethane42. Bromobenzene43. 1,2,3-Trichloropropane44. n-Propylbenzene45. 2-Chlorotoluene46. 1,3,5-Trimethylbenzene47. 4-Chlorotoluene48. tert-Butylbenzene49. 1,2,4-Trimethylbenzene50. sec-Butylbenzene51. 1,3-Dichlorobenzene

52. p-Isopropyltoluene53. 1,4-Dichlorobenzene54. n-Butylbenzene55. 1,2-Dichlorobenzene56. 1,2-Dibromo-3-chloropropane57. 1,2,4-Trichlorobenzene58. Hexachlorobutadiene59. Naphthalene60. 1,2,3-Trichlorobenzene

18. Benzene19. 1,2-Dichloroethane20. Trichloroethene21. 1,2-Dichloropropane22. Dibromomethane23. Bromodichloromethane24. cis-1,3-Dichloropropene25. Toluene26. trans-1,3-Dichloropropane27. 1,1,2-Trichloroethane28. Tetrachloroethene29. 1,3-Dichloropropane30. Dibromoethane31. 1,2-Dibromethane32. Chlorobenzene33. 1,1,1,2-Tetrachloroethane34. Ethylbenzene


PURGEABLES ANALYSIS WITH DB-502.2Column: 105m x 0.53mm x 3.0 µm, DB-502.2

GC ConditionsOven: 35°C for 10 min,35-200°C at 4°C/min200°C for 5 minCarrier: Helium at 10 ml/minInjector: Purge and trap (O.I.A 4560)Trap: Tenax/Silica gel/CMSDesorb: 200°C for 0.6 minDetector B: ELCD (O.I.A 4420)

ELCD

1

2 3

4

56

7

8

9 10

11,12

14

1315171619

20

2123

22

2426

27

28

29

30

31

32

33

39

41

43

42

4547

5153

55

56

57

58

60


PURGEABLES ANALYSIS WITH DB-624

Column: 75m x 0.53mm x 3.0 µm, DB-624GC Conditions

Oven: 35°C for 8 min35-200°C at 10°C/minCarrier: Helium at 10 ml/minInjector: Purge and trap (O. I. A. 4560)20 ppb per compound in 5 ml waterTrap: Tenax/Silica gel/CMSDesorb: 200°C for 2 minDetector B: ELCD (O.I.A 4420)

ELCD

1

2

3

45

6

7

89 10

11, 12

13

14

15

16, 17

19

20

21

22

23

24

26

27

28, 29

30

3132

33

39

4142, 43

4547

515355

56

57

58

60


PURGEABLES ANALYSIS WITH DB-VRXColumn: 75m x 0.45mm x 2.55 µm, DB-VRXGC Conditions

Oven: 35°C for 12 min, 35-60°C at 5°C/min60°C for 1 min, 60-200° at 17°C/min200°C for 3 minCarrier: Helium at 10 ml/min,measured at 35°CInjector: Purge and trap (LSC 2000)20 ppb per compound in 5 ml water

Trap: VOCARB 4000Preheat: 240°CDesorb: 245°CHelium makeup gas at 30 ml/minDetector B: ELCD (O.I.A 4420)

ELCD1

2 3

4

5

67

8

910

11

13

14

121915

17

16

22

21

20

23

24

26

27

29

30

31

2833

32

39

41

43

42

46

47

51

53

55

56

57

58

60


COLUMNS OF CHOICE FOR VOC METHODS

• VOC Methods using 5970,71 & 72 MSD detectors and split injector interface

DB-VRX, 60m x 0.25mm ID x 1.4um film

• VOC Methods using 5973 MSD and split injector interface

DB-624, 20m x 0.18mm ID x 1.0um film


• VOC Methods using standard detectors


DB-624, 75m x 0.45mm ID x 2.55um film

• Contact Technical Support for complete column recommendation


BASICS OF PURGE AND TRAP TROUBLESHOOTING

Divide and conquer by elimination

Take nothing for granted-CHECK EVERYTHING


BASICS OF PURGE AND TRAP TROUBLESHOOTING

•Begin with "high" concentration standard

•If two detectors are being used, compare same run results

•Discern between chemical and electromechanical problems by turning things off


CONCLUSIONSPURGE AND TRAP CONCENTRATOR

• Purge Flow

• Desorb

• Bake

• Trap


CONCLUSIONSCOLUMN SELECTION

•Stationary Phase Selectivity

•Film Thickness

•Column Dimensions


J&W Scientific Technical Support

800-227-9770 (phone: US & Canada)*

302-993-5304 (phone)*

* Select option 4, then option 2.

916-608-1964 (fax)

www.agilent.com/chem


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