Uma abordagem simples e abrangente para dominar as variáveis que afetam a injeção em cromatografia gasosa de alta resolução
Aquino Neto, Francisco Radler de
Palavras-chave: Split injection, splitless injection, on-column injection, retention gap, band broadening, cold trap, solvent effect, peak focusing, peak distortion.
Resumo: Three decades have elapsed after the thorough clarification of the behavior of the molecules during injection in HRGC. The high resolution associated with the technique is only achieved if the injection variables are strictly controlled and their synergy guaranteed in order to generate an extremely narrow distribution of analytes in the beginning of the chromatographic separation column (i.e., beginning of the stationary phase film). Surprisingly enough most chromatographers do not master this knowledge and simply operate the injection systems in a standard way. Thus, the present review aims to define in a thorough, but straightforward, manner, the variables involved in the injection process and their interrelationship. To do so, an extended concept of the injection in GC is forwarded, where the “injection” is considered to encompass the processes occurring from the syringe up to the beginning of the stationary phase film, passing through the vaporizing chamber, capillary column entrance and retention gap if purposely present. Main variables affecting the distribution of analytes in the beginning of the stationary phase are the chemical nature and amount of solvent, analytes and sample matrix; solvent and analyte boiling points; dimensions, constitution and operation of the syringe needle, vaporizing chamber, capillary column, retention gap and stationary phase; temperatures of the vaporizing chamber, capillary column and retention gap; as well as, type of carrier gas (H2 or helium), inlet pressure (and pressure or flow control system), septum purge, split purge, and column flows.
1. Grob, K.; Grob, G. (1976) A new, generally applicable procedure for the preparation of glass capillary columns. J. Chromatogr. A 125(3): 471-485.
2. K. Grob, G. Grob, G. (1986) Making and manipulating capillary columns for gas chromatography. Dr. Alfred Huethig Verlag, Heidelberg.
3. Desty, D.H., editor (1958) Gas chromatography 1958 proceedings of the second symposium organized by the Gas Chromatography Discussion Group under the auspices of the Hydrocarbon Research Group of the Institute of Petroleum and the Koninklijke Nederlandse Chemische Vereniging held at the Royal Tropical Institute, Amsterdam, 19-23May 1958.
4. Grob, K.; Grob, G (1969) Splitless injection in capillary columns. J. Chromatogr. Sci. 7 584-587.
5. Grob, K.; Grob, G (1978) Splitless injection and the solvent effect. J. HRC&CC 1: 57-64.
6. Grob, K.; Grob Jr., K. (1978) On-column injection on to capillary columns. J. Cromatogr. 151(3): 311-320.
7. Grob Jr., K. (1981) Peak broadening or splitting caused by solvent flooding after splitless or cold on-column injection in capillary gas chromatography. Journal of Chromatography A, Volume 213, Issue 1, 21 August 1981, Pages 3-14.
8. Grob Jr., K. (1983) Solvent effects in capillary gas chromatography. J. Chromatogr. A, 279, 25: 225-232.
9. Grob Jr., K. (1985) Band broadening in space in splitless injection. J. Chromatography A 324: 251-259.
10. Grob Jr., K (1982) Band broadening in space and the retention gap in capillary gas chromatography. J. Chromatogr. 237 (1): 15-23.
11. Aquino Neto, F.R.; Cardoso, J.N. (1992) CGAR.9. Lacunas de retenção em cromatografia gasosa de alta resolução. Química Nova 15(3): 224-227.
12. Grob Jr., K. (2000) On-Column Injection in Capillary Gas Chromatography Basic Technique, Retention Gaps, Solvent Effects 3ed. John Wiley & Sons , 591 p.
13. Grob Jr., K. (2001) Split and Splitless Injection for Quantitative Gas Chromatography: Concepts, Processes, Practical Guidelines, Sources of Error, 4th edition, 480 p. Released online for download: 11-21-2008.
14. Cardoso, J.N.; Aquino Neto, F.R. (1989) CGAR.8. Seleção da técnica de injeção de amostra em CGAR. Química Nova 12(1): 13-18.
15. Furtado, E.G.; Cardoso, J.N. (1984) Simple conversion of a Perkin Elmer model 900 GC for capillary work. J. Chromatogr. Science 22: 87-88.
16. Grob Jr., K.; Neukom, N.P. (1979) The influence of the syringe needle on the precision and accuracy of vaporizing GC injectors. JHRC&CC (1): 15-21.
17. Grob Jr., K; Schilling, B. (1987) Uncoated capillary column inlets (retention gaps) in gas chromatography. J. Chromatogr. 391: 3-18.
18. Grob Jr., K.; Neukom, H.P. (1982) Dependence of the splitting ratio on column temperature in split injection capillary gas chromatography. J. Chromatogr. 236(2): 297-306.
19. Grob Jr., K.; B. Schilling, B.(1983) Observation of a peak under the action of “phase soaking”, a gas chromatographic solvent effect, during passage through a capillary column. J. Chromatogr. A 259: 37-48.
20. Grob Jr., K.; Schilling, B. (1983) Solvent effects in capillary GC; determination of trace amounts of chloroform as an example. J. Chromatogr. 264: 7.
21. Aquino Neto, F.R. (1996) CGAR.12. Deformações de picos em CGAR.1. Principais causas. Química Nova 19(1): 73-75. 22.Stuckenbruck, P.; Aquino Neto, F.R. (1989) Behaviour of phenolic compounds related to wood tar in quantitative HRGC with on-column injection. Proceedings of the 10th International Symposium on Capillary Chromatography p. 805-811. HRC 13 (3): 210-212. (1990).
23. Grob Jr. (1984) Effect of “dirt” injected on-column in capillary gas chromatography; analysis of the sterol fraction of oils as an example. J. chromatogr. 287: 1-14.
24. Grob Jr., K.; Bossard, M. (1984) Effect of dirt on quantitative analyses by capillary gas chromatography with splitless injection. J. Chromatogr. A 294: 65-75.
25. Grob, K.; Laubli, Th.; Brechbuhler (1988) Splitless injection – development and state of the art. Including a comparison of matrix (“dirt”) effects in conventional and PTV splitless injection. J. HRGC&CC 10(2): 462- 470.
26. Castro, I.M.; Aquino Neto, F.R. (1989) The role of retention gaps in routine whole oil biomarker analyses with cold on-column injection. Proceedings of the 10th International Symposium on Capillary Chromatography p. 320-327. HRC 13 (4) 302-304 (1990)