TEORI_KROMATOGRAFI_MODRE dalam kimiaN.pptx

ppt

1. TEORI KROMATOGRAFI MODREN

2. Kromatografi modren berdasarkan fasa geraknya Cair Kromatografi Cair Kinerja Tinggi

3. KROMATOGRAM Kromatogram : grafik berupa kerucut-kerucut atau dalam istilah kromatografi modren disebut “ peak “, hasil rekaman yang menggambarkan urutan keluarnya komponen campuran dari kolom.

4. Dari kiri ke kanan dalam kromatogram menyatakan waktu, biasanya dalam menit. Sumbu vertikal menyatakan intensitas komponen. Jumlah peak yang muncul menyatakan jumlah komponen yang terdapat dalam campuran. Kuantitas tiap komponen dapat dihitung melalui peak, semakin besar luas peak semakin besar kuantitas komponen tersebut. Peak2 yang muncul diharapkan berbentuk simetri dan runcing sehingga tidak tumpang tindih satu dengan yang lainnya. Band Broadening

5. WAKTU RETENSI (t R ) Waktu retensi adalah ukuran waktu mulai injeksi cuplikan hingga suatu komponen campuran keluar kolom atau waktu yang diperlukan oleh suatu komponen campuran (solute) untuk keluar dari kolom. Waktu retensi diukur melalui kromatogram dari menit ke-0 hingga muncul puncak peak. Peak pertama (t ) yang muncul pada kromatogram disebabkan oleh komponen yang tidak berinteraksi dengan fasa diam, seperti udara dalam KG dan pelarut sampel dalam HPLC. T tidak dianggap sebagai komponen campuran yang sedang dipisahkan.

6. FAKTOR KAPASITAS Faktor kapasitas (k’) merupakan suatu ukuran kekuatan interaksi suatu komponen dengan fasa diam:

7. Senyawa-senyawa yang mempunyai harga faktor kapasitas tinggi menunjukkan komponen tersebut berinteraksi dengan fasa diam secara kuat. Komponen-komponen yang mempunyai harga faktor kapasitas rendah menunjukkan komponen tersebut beribteraksi dengan fasa diam secara lemah.

8. Selektivitas Selektivitas ( α ) : ukuran keterpilihan dua komponen campuran yang dipisahkan. k1’ dan k2’ masing2 adalah faktor kapasitas komponen pertama dan kedua. Bila harga α = 1 berarti senyawa 1 dan 2 keluar dari kolom bersama-sama (senyawa 1 tidak dapat dipisahkan dari senyawa 2). Bila harga α > 1, maka senyawa 1 keluar dari kolom lebih cepat dari pada senyawa 2. Semakin besar harga α semakin baik pemisahan.

9. EFISIENSI Ada dua parameter yang digunakan untuk menilai kualitas pemisahan kromatografi yakni ukuran banyaknya pelebaran puncak dari masing-masing puncak solut (efisiensi) dan tingkat pemisahan puncak-puncak yang berdekatan (resolusi). Semakin lebar suatu peak kromatogram maka dapat dikatakan pemisahan semakin kurang efesien. Secara kuantitatif, efisiensi dapat dijelaskan dengan plat number (N). Semakin besar harga N, semakin efisien pemisahan.

10. Peak (Puncak)

11. Perhitungan harga n

12. hetp Efisiensi pemisahan dapat juga dinyatakan dalam bentuk parameter lain yaitu HETP (Height Equivalent Theoritical Plate) yang diformulasikan sebagai berikut: L menyatakan panjang kolom dalam cm. Semakin kecil harga HETP semakin efisien.

13. RESOLUSI Derajat pemisahan dua komponen campuran dalam proses kromatografi. Berdasarkan persamaan terlihat bahwa resolusi dipengaruhi oleh 3 faktor yaitu efisiensi (N) rata-rata, selektivitas ( α ) dan faktor retensi (k’)

14. Semakin besar harga Rs, semakin baik pula pemisahan.

15. PELEBARAN PUNCAK (BAND BROADENING) A. DIFUSI EDDY Akibat perbedaan waktu kedatangan di detektor menyebabkan peak kromatogram melebar dan kurang efisien, untuk mencegah pelebaran puncak maka ukuran partikel fasa diam harus merata.

16. B. Difusi Longitudinal Molekul-molekul solut berkecendrungan berdifusi kesegala arah. Semakin lama solut berada dalam kolom maka semakin besar pula kecendrungan berdifusi yang mengakibatkan pelebaran puncak.

17. C. Tranfer massa Sebagian molekul solut berada dalam fasa gerak dan sebagian lagi berada dalam fasa diam. Bila fasa gerak mengalir secara cepat sementara sebagian molekul solut tidak dapat keluar dari fasa diam secara cepat maka sebagian solut terlambat meninggalkan kolom. Hal ini mengakibatkan melebarnya puncak kromatogram.

18. HPLC and FPLC KCKT (KROMATOGRAFI CAIR KINERJA TINGGI)/ HPLC

19. HPLC

20. PENDAHULUAN Kromatografi cair kinerja tinggi atau KCKT atau biasa juga disebut dengan HPLC (High Performance Liquid Chromatography) dikembangkan pada akhir tahun 1960-an dan awal tahun 1970-an. Kegunaan umum KCKT: - analisis asam nukleat - analisis protein - analisis karbohidrat - analisis senyawa-senyawa kiral - analisis senyawa-senyawa yg tidak mudah menguap - penentuan molekul-molekul netral, ionik maupun zwiter ion - Isolasi dan pemurnian senyawa, dll.

21. Fasa gerak : Berupa zat cair dan disebut juga eluen atau pelarut. Fasa gerak selain membawa komponen-komponen campuran menuju detektor, fasa gerak dapat berinteraksi dengan solut-solut. Keuntungan KCKT : -kemampuannya untuk menganalisis cuplikan yang tidak menguap dan labil pada suhu tinggi. -dapat menganalisis cuplikan yang mempunyai berat molekul tinggi atau titik didihnya sangat tinggi, seperti polimer.

22. CARA KERJA KCKT Instrumen KCKT pada dasarnya terdiri atas delapan komponen pokok yaitu: Wadah fasa gerak Sistem penghantaran fasa gerak Alat untuk memasukkan sampel Kolom Detektor Wadah penampung buangan fase gerak Tabung penghubung Suatu komputer atau integrator atau perekam.

23. BAGAN SISTEM HPLC

24. PRINSIP KERJA Dengan bantuan pompa fasa gerak cair dialirkan melalui kolom ke detektor. Cuplikan dimasukkan ke dalam aliran fasa gerak dengan cara penyuntikan. Di dalam kolom terjadi pemisahan komponen-komponen campuran. Karena perbedaan kekuatan interaksi antara solut-solut terhadap fasa diam, solut-solut yang kurang interaksinya dengan fasa diam akan keluar terlebih dahulu dan sebaliknya. Setiap komponen campuran yang keluar kolom dideteksi oleh detektor kemudian direkam dalam bentuk kromatogram.

25. WADAH FASE GERAK PADA KCKT Wadah fase gerak harus bersih dan lembam (inert). Wadah ini biasanya dapat menampung fasa gerak antara 1 sampai 2 l pelarut. Fase gerak sebelum digunakan harus dilakukan degassing (penghilangan gas) yang ada pada fase gerak, sebab adanya gas akan berkumpul dengan komponen lain terutama di pompa dan detektor sehingga akan mengacaukan analisis. Dianjurkan penggunaan pelarut dengan kemurnian yang sangat tinggi.

26. Fase gerak pada KCKT Fase gerak atau eluen biasanya terdiri atas campuran pelarut yang dapat bercampur yang secara keseluruhan berperan dalam daya elusi dan resolusi. Fase gerak yang paling sering digunakan untuk pemisahan dengan fase terbalik adalah campuran larutan buffer dengan metanol atau campuran air dengan asetonetril. Untuk pemisahan dengan fase normal, fase gerak yang sering digunakan adalah campuran pelarut2 hidrokarbon dengan pelarut yang terklorisasi atau menggunakan pelarut-pelarut jenis alkohol.

27. Column Column Pump [LOAD] [INJECT] Pump INJEKTOR: Alat untuk pemasukan sampel ke dalam sistem KCKT alat penyuntik yang terbuat dari tembaga tahan karat.

28. Untuk memasukkan cuplikan ke dalam aliran fasa gerak perlu 2 langkah: Sejumlah volume cuplikan disuntikkan ke dalam loop dalam posisi load , cuplikan masih berada dalam loop. Kran diputar untuk mengubah posisi load menjadi posisi injeksi dan fasa gerak membawa cuplikan ke dalam kolom.

29. HPLC and FPLC HPLC and FPLC By: Britney Sykes

30. Several chromatographic techniques Even though each method utilizes different techniques to separate compounds, the principles are the same. Common to all: Stationary phase- a solid or a liquid supported on a solid Mobile phase- A liquid or gas Chromatography Theory Review

31. As the mobile phases passes through the stationary phase, it carries the components of the sample mixture with it. The components of the sample will be attracted to the stationary phase, but there will also be a competing attraction for the mobile phase. Each component will have its own characteristic balance of attraction to the mobile/stationary phase. So the components will not move at the same speed and are separated. Chromatography Theory Review

32. Column Chromatography Similar to thin layer chromatography Stationary phase = silica gel on support Mobile phase = liquid solvent In column chromatography, this stationary phase is packed into a vertical glass column. Mobile phase moves down the column as a result of gravity.

33. Column Chromatography Blue compound = more polar Adsorb more to the silica gel Elutes slower Yellow compound = less polar Spends much of its time in the mobile phase Elutes faster Example of column chromatography separation:

34. HPLC Introduction: HPLC = improved form of column chromatography Instead of the mobile phase moving through the column as a result of gravity, it is forced through the column under high pressure. Typical operating pressures: 500-6000psi To get improved separation – smaller sized packing material is required (<10 µm) . Smaller packing = greater resistance to flow Low flow rate = solute diffusion Higher pressures needed to generate the needed solvent flow Gravity is too slow- high pressure greatly speeds up the procedure.

35. 1903: Russian botanist Mikhail Tswett Separated plant pigments through column adsorption chromatography Packed open glass column with particles Calcium carbonate and alumina Poured sample into column, along with pure solvent As the sample moved down the vertical column, different colored bands could be seen. Bands correlated to the sample components. Coined the term chromatography from the Latin word meaning “color writing”. HPLC History

36. Early 1950s: First appearance of GC Almost immediately became popular. Work began on improving LC 1964: J. Calvin Giddings Published a paper entitled “Comparison of the Theoretical Limit of Separating Ability in Gas and Liquid Chromatography” in the journal Analytical Chemistry. Outlined ways to improve LC: smaller packing size, increased pressure In theory, he demonstrated how LC could actually be more efficient than GC. Increased number of theoretical plates HPLC History

37. HPLC History 1966: Horváth Built the first HPLC instrument and gave it its name HPLC = High Pressure Liquid Chromatography. 1970’s: HPLC became popular with an increase in technology Improved columns and detectors Production of small silica packing material By 1972 particle sizes less than 10 µm were introduced This allowed for more precise and rapid separations. As new technology continued to develop, HPLC became more efficient. HPLC = High Performance Liquid Chromatography

38. Overview of the HPLC Process Mobile phase pumped through column at high pressure. Sample is injected into the system. Separation occurs as the mobile phase and sample are pumped through the column. Each sample component will elute from the column, one at a time, and will be detected by one of several possible detector types. The response of the detector to each component eluted will be displayed on a chart or computer screen. Known as a chromatogram. Each compound eluted will show up as a peak on this chromatogram. Data processing equipment are used to analyze the data generated. http://www.waters.com/WatersDivision/flash/hplc_primer/hplcsys_primer.html

39. Diagram of HPLC Apparatus: 1. http://www.cem.msu.edu/~cem333/Week16.pdf

40. Design & Operation of an HPLC Instrument 1) Mobile phase degassing: Dissolved gases in the mobile phase can come out of solution and form bubbles as the pressure changes from the column entrance to the exit. May block flow through the system Sparging is used to remove any dissolved gas from the mobile phase. An inert and virtually insoluble gas, such as helium, is forced into the mobile phase solution and drives out any dissolved gas. Degassing may also be achieved by filtering the mobile phase under a vacuum.

41. Design & Operation of an HPLC Instrument 2) Solvent reservoirs: Individual reservoirs store the mobile phase components until they are mixed and used. May also manually prepare the mobile phase mixture and store in a single reservoir. 2.

42. 3) Mobile phase mixing: Solvent proportioning valve can be programmed to mix specific amounts of solvent from the various reservoirs to produce the desired mobile phase composition. Design & Operation of an HPLC Instrument 3.

43. 3) Mobile phase mixing: Isocratic elution : operate at a single, constant mobile phase composition Gradient elution : Vary the mobile phase composition with time If there is a wide polarity range of components to be eluted. Allows for faster runs. Ex: mobile phase composition can be programmed to vary from 75% water: 25% acetonitrile at time zero to 25% water: 75% acetonitrile at the end of the run. More polar components will tend to elute first. More non-polar components will elute later in the gradient. Design & Operation of an HPLC Instrument

44. Design & Operation of an HPLC Instrument 4) HPLC pump: Fill stroke: mobile phase is pulled from the solvent side Exhaust stroke: the mobile phase is pushed from the injector to the column head. This is where the high pressure is generated 4.

45. 4) HPLC pump: Most common = reciprocating piston type Flow rates change during pumping cycle Want to minimize flow surges Pulse dampener Dual pistons While one piston fills, the other delivers Design & Operation of an HPLC Instrument http://www.lcresources.com/resources/getstart/2b01.htm

46. 5) Injector: Introduces the sample into the mobile phase stream to be carried into the column. Syringe = impractical for use in highly pressurized systems. Rotary injection valve is used. For more information visit: http://www.lcresources.com/resources/getstart/2c01.htm Design & Operation of an HPLC Instrument 5.

47. 6) Column: Usually constructed of stainless steel glass or Tygon may be used for lower pressure applications (<600 psi). Length: 5-100cm 10 to 20cm common Diameter: Typical: 2.1, 3.2, or 4.5mm Up to 30mm for preparative applications Design & Operation of an HPLC Instrument 6.

48. Column packing: Usually spherical silica particles of uniform diameter (2-10 µm) The smaller particles yield higher separation efficiencies. The silica particles are very porous Allows for greater surface area for interactions between the stationary phase and the analytes. Other packing materials may also be used: Zirconia (ZrO 2 ) http://www.lcresources.com/resources/getstart/3a01.htm Design & Operation of an HPLC Instrument http://hplc.chem.shu.edu/NEW/HP LC_Book/Adsorbents/ads_part.html

49. 6) Column: Guard column : Protects the analytical column Particles Interferences Prolongs the life of the analytical column Analytical column : Performs the separation Design & Operation of an HPLC Instrument

50. 7) Detector: The component that emits a response due to the eluting sample compound and subsequently signals a peak on the chromatogram. A wide variety of detectors exist. Must have high sensitivity- small sample sizes are used with most HPLC columns Design & Operation of an HPLC Instrument 7.

51. Detection in HPLC *There are six major HPLC detectors: Refractive Index (RI) Detector Evaporative Light Scattering Detector (ELSD) UV/VIS Absorption Detectors The Fluorescence Detector Electrochemical Detectors (ECDs) Conductivity Detector * The type of detector utilized depends on the characteristics of the analyte of interest. http://www.waters.com/WatersDivision/Contentd.asp?watersit=JDRS-6UXGZ4

52. Refractive Index Detector Based on the principle that every transparent substance will slow the speed of light passing through it. Results in the bending of light as it passes to another material of different density. Refractive index = how much the light is bent The presence of analyte molecules in the mobile phase will generally change its RI by an amount almost linearly proportional to its concentrations. http://farside.ph.utexas.edu/teaching/302l/ lectures/img1154.png

53. Refractive Index Detector Affected by slight changes in mobile phase composition and temperature. Universal-based on a property of the mobile phase It is used for analytes which give no response with other more sensitive and selective detectors. RI = general responds to the presence of all solutes in the mobile phase. Reference= mobile phase Sample= column effluent Detector measures the differences between the RI of the reference and the sample. http://hplc.chem.shu.edu/HPLC/index.html

54. Analyte particles don’t scatter light when dissolved in a liquid mobile phase. Three steps: 1) Nebulize the mobile phase effuent into droplets. Passes through a needle and mixes with hydrogen gas . 2) Evaporate each of these droplets. Leaves behind a small particle of nonvolatile analyte 3) Light scattering Sample particles pass through a cell and scatter light from a laser beam which is detected and generates a signal. Evaporative Light Scattering Detector (ELSD) http://www.sedere.com/WLD/whatis.html

55. UV/VIS Absorption Detectors Different compounds will absorb different amounts of light in the UV and visible regions. A beam of UV light is shined through the analyte after it is eluted from the column. A detector is positioned on the opposite side which can measure how much light is absorbed and transmitted. The amount of light absorbed will depend on the amount of the compound that is passing through the beam. http://www.chemguide.co.uk/analysis/chromatography/hplc.html

56. UV/VIS Absorption Detectors Beer-Lambert law: A= ε bc absorbance is proportional to the compound concentration. Fixed Wavelength: measures at one wavelength, usually 254 nm Variable Wavelength: measures at one wavelength at a time, but can detect over a wide range of wavelengths Diode Array Detector (DAD): measures a spectrum of wavelengths simultaneously

57. The Fluorescence Detector Measure the ability of a compound to absorb then re-emit light at given wavelengths Some compounds will absorb specific wavelengths of light which, raising it to a higher energy state. When the compound returns to its ground state, it will release a specific wavelength of light which can be detected. Not all compounds can fluoresce / more selective than UV/VIS detection. http://mekentosj.com/science/fret/images/ fluorescence.jpg

58. Electrochemical Detectors (ECDs): Electrochemical Detectors (ECDs): Used for compounds that undergo oxidation/reduction reactions. Detector measures the current resulting from an oxidation/reduction reaction of the analyte at a suitable electrode. Current level is directly proportional to the concentration of analyte present. Conductivity Detector: Records how the mobile phase conductivity changes as different sample components are eluted from the column. http://hplc.chem.shu.edu/HPLC/index.html http://hplc.chem.shu.edu/HPLC/index.html

59. Interfacing HPLC to Mass Spectrometry Mass Spectrometry = an analytical tool used to measure the molecular mass of a sample. Measures the mass to charge ratio Allows for the definitive identification of each sample component. Most selective HPLC detector, but also the most expensive. http://www.chem.queensu.ca/FACILI TIES/NMR/nmr/mass-spec/index.htm

60. Picture of a Typical HPLC System http://www.waters.com/WatersDivision/ContentD.asp?watersit=JDRS-6UXGYA&WT.svl=1

61. Retention Time- t R The elapsed time between the time of analyte injection and the time which the maximum peak height for that compound is detected. Different compounds will have different retention times. Each compound will have its own characteristic balance of attraction to the mobile/stationary phase. So they will not move at the same speed. Running conditions can also effect t R : Pressure used, nature of the stationary phase, mobile phase composition, temperature of the column

62. Retention Time- t R If you are careful to keep the conditions constant, you may use t R to help you identify compounds present. Must have measured t R for the pure compounds under identical conditions.

63. Determining Concentration In most cases, sample peaks on the chromatogram can be used to estimate the amount of a compound present. The more concentrated, the stronger the signal, the larger the peak. http://www.waters.com/WatersDivision/Contentd.asp?watersit=JDRS-6UXGZ4

64. t R : Retention time t’ R : Adjusted retention time = (t R - T m ) T m : Dead time W 0,5 : Peak width at half height h: Height of signal

65. Types of HPLC There are numerous types of HPLC which vary in their separation chemistry. All chromatographic modes are possible: Ion-exchange Size exclusion Also can vary the stationary & mobile phases: Normal phase HPLC Reverse phase HPLC

66. Chromatographic Modes of HPLC Ion exchange: Used with ionic or ionizable samples. Stationary phase has a charged surface. opposite charge to the sample ions The mobile phase = aqueous buffer The stronger the charge on the analyte, the more it will be attracted to the stationary phase, the slower it will elute. Size exclusion: Sample separated based on size. Stationary phase has specific pore sizes. Larger molecules elute quickly. Smaller molecules penetrate inside the pores of the stationary phase and elute later.

67. Normal Phase HPLC Stationary phase: polar, silica particles Mobile phase: non-polar solvent or mixture of solvents Polar compounds : Will have a higher affinity for the polar, stationary phase Will elute slower Non-polar compounds : Will have a higher affinity for the non-polar, mobile phase Will elute faster

68. Reverse Phase HPLC Stationary phase: non-polar Non-polar organic groups are covalently attached to the silica stationary particles. Most common attachment is a long-chain n-C18 hydrocarbon Octadecyl silyl group, ODS Mobile phase: polar liquid or mixture of liquids Polar analytes will spend more time in the polar mobile phase. Will elute quicker than non-polar analytes Most common type of HPLC used today. http://www.lcresources.com/ resources/getstart/3a01.htm

69. What is Ultra Performance Liquid Chromatography? 2004: Further advances in column technology and chromatography instrumentation Utilized even smaller packing particle sizes (1.7 µm) Higher pressures (15000psi) Allowed for significant increases in LC speed, reproducibility, and sensitivity. New research utilizing particle sizes as small as 1 µm and pressures up to 100,000psi! WHO KNOWS WHAT THE FUTURE MAY BRING!

70. HPLC Applications Can be used to isolated and purify compounds for further use. Can be used to identify the presence of specific compounds in a sample. Can be used to determine the concentration of a specific compound in a sample. Can be used to perform chemical separations Enantiomers Biomolecules

71. HPLC Applications *HPLC has an vast amount of current & future applications* Some uses include: Forensics: analysis of explosives, drugs, fibers, etc. Proteomics: can be used to separate and purify protein samples Can separate & purify other biomolecules such as: carbohydrates, lipids, nucleic acids, pigments, proteins, steroids Study of disease: can be used to measure the presence & abundance of specific biomolecules correlating to disease manifestation. Pharmaceutical Research: all areas including early identification of clinically relevant molecules to large-scale processing and purification.

72. FPLC- A Modification of HPLC In 1982 Pharmacia introduced a new chromatographic method called FPLC. FPLC = Fast Protein Liquid Chromatography FPLC is basically a “protein friendly” HPLC system. Stainless steel components replaced with glass and plastic. Stainless steel was thought to denature proteins Also many ion-exchange separations of proteins involve salt gradients; thought that these conditions could results in attack of stainless steel systems. FPLC can also be used to separate other biologically active molecules, such as nucleic acid.

73. FPLC- A Modification of HPLC FPLC is an intermediate between classical column chromatography and HPLC. FPLC pump delivers a solvent flow rate in the range of 1-499ml/hr HPLC pump= 0.010-10ml/min FPLC operating pressure: 0-40 bar HPLC= 1-400bar classic chromatography= atmospheric pressure Since lower pressures are used in FPLC than in HPLC, a wider range of column supports are possible.

74. Applications of FPLC/HPLC to Proteomics Protein characterization and measurement is essential to understanding life at the molecular level. The first step in protein analysis is isolation and purification. Proteins can be separated by FPLC/HPLC in various forms. Reversed phase Ion exchange Size exclusion Affinity Used to isolate/purify without loss of biological activity

75. Applications of FPLC/HPLC to Proteomics Not only can FPLC/HPLC systems be used to isolate and purify proteins, but they can be coupled to other instruments for further analysis. UV/VIS Mass Spectrometer This instrument interfacing can allow for the determination of: Protein amino acid sequence Structural information Functional information

76. http://www.msu.edu/~gallego7/MassSpect/MSandPMM.htm

77. The Impact of HPLC/FPLC HPLC/FPLC has such widespread application it is impossible to convey its extensive impact. Has many advantages in situations were a nonvolatile or thermally unstable sample must be separated. As with many biochemical samples Great speed and resolution Resolution = how well solutes are separated Columns don’t have to be repacked Adaptable to large-scale, preparative procedures.

78. References Ashcroft, A.E. An Introduction to Mass Spectrometry . URL: http://www.astbury.leeds.ac.uk/facil/MStut/mstutorial.htm . Accessed: July 1, 2007. Detectors and Detection Limits. URL: http://kerouac.pharm .uky.edu/ASRG/HPLC/detectors.html . Accessed: July 2, 2007. Filmore, David; Lesney, Mark S. Performing Under Pressure: The Rise of HPLC . URL: http://pubs.acs.org/jour nals/chromatography/chap4.html . Accessed: July 1, 2007. FPLC??. URL: http://www.lcresources.com/discus/messag es/5133/2395.html?TuesdayAugust520031156am . Accesed July2, 2007. Getting Started in HPLC. URL: http://www.lcresources.co m/resources/get start/ . Accessed: June 22, 2007.

79. References: High Performance Liquid Chromatography- HPLC. URL: http://www.chemguide.co.uk/analysis/chromatography/hplc.html#top . Accessed: June 15, 2007. High Performance Liquid Chromatography (HPLC) Primer.URL: http://www.waters.com/WatersDivision/Conten td.asp?Watersit =JDRS-6UXGZ4. Accessed: June 22, 2007. Kazakevich, Y; McNair, H.M. Basic Liquid Chromatography . URL: http://hplc.chem.shu.edu/HPLC/index.html . Accessed: June 22, 2007. Boyer, Rodney. Modern Experimental Biochemistry.3rd Ed. Addison Wesley Longman. San Frisco, CA. 2000. 87-100. Robertson, James W.; Frame, Eileen M.; Frame, George M. Undergraduate Instrumental Analysis . Marcel Dekker: New York, NY. 2005.797-836.