Low cost, robust, in‐house hardware for heart cutting two‐dimensional gas chromatography

Abstract

Natural materials are so complex that no single column can separate all of the components. Heart cutting 2-D GC (GC-GC) using a Deans switch provides maximum separation, but the requisite gas flow configurations have earned a reputation for being fiddly and time consuming to set up and tune, unless electronic gas controls and costly software are employed. A design for a vented Deans switch is presented that can be assembled in-house from standard commercial components. A vent to atmosphere replaces the balancing resistor, which solves the problem of balancing the pressures and flows, and requires no compensation for changes in gas viscosity and back-pressure during temperature programming. First and second dimension columns can both be run at optimum flow rates, even if they are of different diameters. Analyte detectability is preserved by cutting only the target fraction from the first column and transferring the whole of it to the second column. Cryotrapping the selected fraction allows cuts of any width, and transfer of analytes to the second column as sharp bands. I have applied the vented Deans switch-cold trap to the identification of flavour and fragrance compounds from South African plants and foods; cuts are very repeatable, and the detectability of trace components is enhanced. Its capabilities are demonstrated by examples from analyses of essential oils and flavour extracts.

Comprehensive Theory of the Deans’ Switch As a Variable Flow Splitter: Fluid Mechanics, Mass Balance, and System Behavior

“…A simple realization is done by three Y-type press-fit connectors. 3 The two outer connectors (1 and 3) are connected to makeup lines from a 3-way solenoid valve. The carrier gas supplied here is directed to one of the two Y-connectors; the other is shut off (in Figure 1 the connector 1 is supplied with carrier gas).…”

“…In Figure the basic setup of a Deans’ switch is depicted. A simple realization is done by three Y-type press-fit connectors . The two outer connectors (1 and 3) are connected to makeup lines from a 3-way solenoid valve.…”

Desenvolvimento de método analítico para determinação isotópica de nitrogênio empregando Espectroscopia de Emissão Molecular Induzida por Laser (LAMIS) e Espectroscopia no Infravermelho Próximo (NIRS)

“…Na GC-GC, a coluna secundária normalmente possui dimensões similares à de colunas utilizadas em análises 1D-GC -isto é, mesmo comprimento e diâmetroe desta forma, normalmente são operadas nas mesmas condições de temperatura e vazão de análises 1D-GC [2]. Como ambas colunas 1 D e 2 D possuem geometriase capacidade de picosimilares, o tempo de análise necessário em cada dimensão é um fator importante a ser considerado em GC-GC.…”

“…1,50 mL min -1 durante 1 min e depois 1,00 mL min -1 a 1 mL min 2 5,00 mL min -1 por 1 min e depois 12,80 mL min -1 a 8 mL min -1 De acordo com a Tabela 2.1, a vazão de gás de arraste na 1 D segue a seguinte ordem: método CC < método CP < método PP. Como observado na Figura 2.9, a mesma ordem foi encontrada em relação aos volumes de pico para todos os analitos, indicando uma melhora na transferência de massa.…”