1. GC Column and Mode operation

2. temperature controlled oven, door opened to show column
from
injector
exit to
detector
Kolom dala GC merupaka salah satu komponen utama dalam pemisahan. Kolom berada setelah injektor dan sebelum detektor, dimana terjadi proses pemisahan. Kolom terdapata di dalam oven dengan suhu yang bisa diatur. Besar suhu di dalam kolom ini diatur sedemikian rupa sehingga wujud fasa dalam kolom tetap sesuai dengan ang diinginkan
capillary
column
temperature controlled oven,
door opened to show column

3. Types of GC Column Packed Column Capillary Column
Secra umum, didalam GC ada dua jenis kolom yaitu kolom packed dan kapiler

4. Packed Column stainless steel, nickel, glass, plastics, aluminium.
Internal diameter 1.6 to 9.5 mm
Length is often 1-3 m
Limited Resolution (N< 8,000)
Internal column diameter should be at least eight times the diameter of the support particles
Densely packed with packing materials or solid support coated with thin layer of stationary liquid phase
Diatomaceous earth
Size: mesh ( m) or mesh ( m)
Kolom packed merupakan kolom yang biasanya terbuat dari stanless, nikel, kaca, plastik dan aluminium dengan dimeter 1,6 sampai 9 mm dan panjang 1-3 M. Kolom ini memiliki resolusi yang tidak terlalu besar, dimana didalamnya sp alan berada dalam pacekd dengan supproting material, yang biasany a terbuat dai tanah diatomae ( nama dagang: diatoport, celite atao chromosorb,komposisis: silika, al2o3, fe2o3, cao, dll). Chromosorb ini telah dinonaktifkan sehingga mencegah kemungkinan reaksinya dnegan Sp atau MP, dengan melindungi gugus hidroksil dari pendukung, yang sering dipakai dimetilklorosilan dan heksamet

5. Packed Column
Pada packed colomun, Sp memenuhi rongga dari kolom, dan melapisi supporting material.

6. Capillary Column Internal diameter 1 mm or less. typically <500 μm
Usually constructed of fused silica, metal, plastic, glass (fragile)
Two kinds of capillarly columns are: packed columns with solid particles over the hole diameter of the column (micropacked) and open tubular columns with an open and unrestricted flow
Kolom kapiler biasanya diameternya lbih kecil, 1 mm atau kuran.ada dua macam: packed dengan solid artikel diseluruh diameter kolom atau open tubular

7. Types of Capillary column
Solid support coated with liquid phase
Porous Adsorbent
Liquid phase
Wall coated dibuat dengan memasukkan fasa diam ke dalam kolom sampai terbentuk suatu lapisan yang setimbang pada dinding kolom atau dengan measukkan suatu plug yang rapi ke dalam kolom dengan tekanan, sehingga didapatkan lapisan pada dinding yangs eragam. SCOT dibuat dengan kapastas besar, dimana dengan mendepositkan suatu lapisan tipis diatomite yang sudah dilapisi oleh fasa diam, untuk memberikan suatu ruangan yang luas untuk proses pemisahan. Metode ini sekarang sudah digantikan oleh wcot.fasa diamyang melapisi supporting material mudah menhabiskan kolom dan rusak oleh pelarut dan kontaminan. PLOT dengan alumnia, molekular sieve dan coplymer surface coating untuk pemisana alkana C1-C6, alkena dan gas atmosfer yang memiliki retensi rendah, yang ditingkatkan dengan mengganti lapisan film fasa diam dengan adsorbent fasa diam untuk meningkatkan mekanisme retensi
Wall-coated Open Tubular
(WCOT)
Support-coated Open Tubular
(SCOT)
Porous Layer Open Tubular
(PLOT)
FSOT: Fused-silica open tubular column

8. Characteristics Type of Column PLOT WCOT SCOT Packed Length (m) 10-100
1-6
ID (mm)
, 0.53*
0.5
2-4
Efficiency (Plate/m)
Sample size (ng)
10-75
10-106
Relative pressure
Low
High
Relative speed
Fast
Slow
Flexible
Yes No
Chemical inertness
Best
Poor
*Megabore column

9. For capillary GC columns….
Increased length = greater N, therefore a greater R
expense is possible band broadening if analytes are on the column too long!
Increased length leads to longer separations. Do you have the time?
Increased stationary phase thickness and column diameter provides increased sample capacity and can provide increased resolution
tradeoffs are a longer analysis time and more column bleed with thicker stationary phases
Is the column compatible with the detector?
Thick stationary phases bleed more and will contaminate a mass spectrometer.
For most analytical work, a best “compromise” column is chosen and other variables (temp, etc.) are altered to optimize the separation.
Dalam kolom kapiler, kenaikan anjang kolom jug meningkatkan nilai N, sehingga nilai resolusi juga akan naik.kelemhahan: kemungkinan besar ada pelebaran puncak jika analit terlalu lama dalam kolom dan waktu analisis lama
Kenaikan ketebalan fasa diam dan diameter kolom -- kenaikan kapasitas dan kenaikan resolusi . Kelemahan: semakin tebal, smakin lama dan kemungkinan kolom bleeding

10. Stationary Phases
Low volatility, thermal stability, chemical inertness
Provide k and  within a suitable range
consider the polar characteristics of the analytes and select SP of similar polarity
‘Like dissolves like’

11. Column Dimensions Column Length: 10 – 60 m
Column Internal Diameter: 0.10 – 0.53 mm
Stationary Phase Film Thickness: 0.10 – 0.25 mm

12. Stationary Phases Solid phase Liquid phase
Most uses for separation of low MW compounds and gases
Common SP: silica, alumina, molecular sieves such as zeolites, cabosieves, carbon blacks
Liquid phase
Over 300 different phases are widely available
grouped liquid phases
Non-polar, polar, intermediate and special phases
Polymer liquid phase

13. Stationary Phase Polymers
Siloxane
Arylene
Polyethylene glycol

14. Liquid phases Non-polar phase Polar phase Intermediate phase
Primarily separated according to their volatilities
Elution order varies as the boiling points of analytes
Common phases: dimethylpolysiloxane, dimethylphenylpolysiloxane
Polar phase
Contain polar functional groups
Separation based on their volatilities and polar-polar interaction
Common phases: polyethyleneglycol
Intermediate phase

15. Bonded and Cross-linked SP
Polymer chains
Cross-linking
Bonding
Fused silica tubing surface
Bonded and cross-linked SP provides long term stability, better reproducibility and performance.

16. Common stationary phase coating for capillary column
Composition
Polarity
Applicaitons
Temp limits
100% dimethyl polysiloxane (Gum)
Nonpolar
Phenols, Hydrocarbons, Amines, Sulfur compounds, Pesticides, PCBs
-60oC to 325oC
100% dimethyl polysiloxane (Fluid)
Amino acid derivatives, Essential oils
0oC to 280oC
5% diphenyl 95% dimethyl polysiloxane
Fatty acids, Methyl esters, Alkaloids, Drugs, Halogenated compounds
14% cyanopropyl phenyl polysiloxane
Immediate
Drugs, Steroids, Pesticides
-20oC to 280oC
50% phenyl, 50% methyl polysiloxane
Drugs, Steroids, Pesticides, Glycols
60oC to 240oC
50% cyanopropylmethyl, 50% phenylmethyl polysiloxane
Fatty acids, Methyl esters, Alditol acetates
50% trifluoropropyl polysiloxane
Halogenated compounds, +Aromatics
45oC to 240oC
Polyethylene glycol – TPA modified
Polar
Acids, Alcohols, Aldehydes acrylates, Nitriles, Ketones
Polyethylene glycol
Free acids, Alcohols, Ethers, Essential oils, Glycols, Solvents
60oC to 220oC

19. Stationary Phase CHEMICALLY STABIL AND INERT
DISPERSED ON THE SOLID SUPPORT
LOW VISCOSITY (FOR FAST MASS TRANSFER)
SOLUBLE IN ORGANIC SOLVENTS
THERMALLY STABIL
LOW VAPOUR PRESSURE
HIGH SELECTIVITY FOR COMPOPUNDS OF INTEREST

21. Stationary Phase

22. Comparison between packed and WCOT

23. Choosing a GC Column… Is the column compatible with your analytes
polar analytes require polar stationary phases so they will spend some of their “time” in the stationary phase
non-polar analytes require non-polar stationary phases
You usually have to compromise on the stationary phase to get a good column for your analytes (which are probably a mix of polar and non-polar)
DB-5, HP-5, EC-5, RTX-5 (5% dimethyl, 95% diphenyl polysiloxane) most common general use column.
Temperature range, solvent and carrier gas compatibility
Sample capacity versus resolution
usually determines packed vs.. capillary
GC’s usually setup for either packed or capillary
Let’s say you choose a capillary column, there’s more to think about!

24. Chromatogram

25. Column performance B A B A
Concentration
Broadening
Distance migrated

26. If the length of the column is L, then the HETP is
column efficiency
Theoretical Plate Model of Chromatography
theoretical plates is a number of a separate layers, where separate equilibrations of the
sample between the stationary and mobile phase occur in
Plates are a figment of the imagination that helps us understand the processes at work in the column.They also serve as a way of measuring column efficiency, either by stating the number of theoretical plates in a column, N (the more plates the better), or by stating the plate height; the Height Equivalent to a Theoretical Plate (the smaller the better).
If the length of the column is L, then the HETP is
HETP = L / N

27. Van Deemter equation for plate height;
The number of theoretical plates that a real column possesses can be found by examining a chromatographic peak after elution;
where w1/2 is the peak width at half-height
Van Deemter equation for plate height;
HETP = A + B / u + C u
where u is the average velocity of the mobile phase. A, B, and C are factors which contribute to band broadening

29. A - Eddy diffusion The mobile phase moves through the column which is packed with stationary phase. Solute molecules will take different paths through the stationary phase at random. This will cause broadening of the solute band, because different paths are of different lengths.
B - Longitudinal diffusion The concentration of analyte is less at the edges of the band than at the center. Analyte diffuses out from the center to the edges. This causes band broadening. If the velocity of the mobile phase is high then the analyte spends less time on the column, which decreases the effects of longitudinal diffusion.
C - Resistance to mass transfer The analyte takes a certain amount of time to equilibrate between the stationary and mobile phase. If the velocity of the mobile phase is high, and the analyte has a strong affinity for the stationary phase, then the analyte in the mobile phase will move ahead of the analyte in the stationary phase. The band of analyte is broadened. The higher the velocity of mobile phase, the worse the broadening becomes.

34. LONGITUDINAL DIFFUSION

37. MASS TRANSPORT

39. RESOLUTION
Another measure of how well species have been separated is provided by measurement of the resolution. The resolution of two species, A and B, is defined as
Baseline resolution is achieved when R = 1.5

40. EFFICIENCY SEPARATION

41. EFFICIENCY OF SEPARATION: PEAK RESOLUTION

42. GAUSSIAN PEAKS

45. PEAK RESOLUTION

47. Column Preparation
A known weight of support is mixed with 3 to 4 times its volume of a volatile solvent containing a weight of the support particles. the solvent is then evaporated, often in a rotary stripper. To give a dry, free flowing solid, which is slowly poured in to the column with gentle trapping

48. Temperature Programming in GC
The “simplest” way to alter the separation in GC is to alter the temperature program in the oven. You can also alter the pressure of the carrier gas, but this is less common (much).
Isothermal = constant temperature
Gradient = varied temperature
By altering the temperature, you vary the rate of the reaction for any analyte:
they spend more or less time in the stationary phase
the greater the difference in the times between analytes, the better the separation!

50. The traps of temperature…
If your temperature at a given time is too high, you can cause the peaks to co-elute
poor resolution vs but a faster separation
If your temperature at a given time is too low, you can get still get a good separation
adequate resolution, but a separation that takes very long
You have to choose a compromise temperature program

52. Temperature program oven or run isothermally

53. Control Panel sets Separation Method

54. Column Temperature
Diatas titik lebur liquid phase, dibawah suhu maksimum yang diperbolehkan dari fasa cair
Suhu kolom berdasarkan kompromi, suhu rendah, pemisahan lebih baik, waktu retensi lama. Kompromi= rata-rata titik didih cuplikan
Penurunan suhu kolom 30˚c, waktu retensi 2 kali lipat

59. Soal 1
Dapatkah saudara meramalkan urutan elusi pada apiezon, OV-17 dan carbowax dari senyawa-senyawa dalam cuplikan berikut:
1-butil bromida
Dietil keton
Metil sikloheksana

60. Jawab
Apiezon: dietil keton-> 1-butil bromida -> metil sikloheksana (kenapa 1-butil bromida keluar setelah dietil keton?)
OV-17: metil sikloheksana -> dietil keton -> 1-butil bromida
Carbowax: metil sikloheksana -> 1-butil bromida -> dietil keton (kenapa dietil keton keluar lebih lama dibandingkan 1-butil bromida?)

61. Soal 2
Urutan elusi propanol, 1-propil asetat dan 1-heptana pada kolom apiezon, ov-17 dan carbowax

62. Jawab Apiezon: propanol -> 1-propil asetat -> 1-heptana
OV-17: propanol -> 1-heptana -> 1-propil asetat (kenapa 1-heptana keluar lebih dulu daripada 1-propil asetat?)
Carbowax: 1-heptana -> 1-propil asetat -> propanol

63. Soal 3 Mengapa resolusi yang baik dengan nilai Rs minimal 1,5?
Mengapa dalam GC tekanan sangat penting dan tekanan gas pembawa harus konstan?