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.

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