Introduction - Agilent Technologies 8860 User Manual

2 Introduction

Introduction

Introduction
The Agilent GC gasifier is designed to enable flash vaporization of liquefied gases as a means of
sample pretreatment before the gas chromatographic analysis. When vaporizing liquefied
samples, it is important to understand the difference between evaporation and vaporization.
Evaporation occurs gradually with an increase in temperature, while vaporization occurs with a
pressure drop. For a mixed sample with low and high boiling points (bp), evaporation will allow low
bp molecules to gasify first and travel on toward the GC while the high bp molecules remain
behind in the liquid phase, resulting in fractionation. It will no longer accurately represent the
samples in the cylinder.
To preserve the sample's composition from liquid state to gasified state, the Agilent gasifier uses
a pressure reducing regulator that can create a severe and sudden pressure drop for
high-pressurized liquid passing its orifice to ensure all compounds vaporize at the same time. This
pressure reducing regulator can handle inlet pressures up to 1000 psi, and the outlet pressure is
factory set to 12 psi +/-2.5 psi (a safe pressure to protect the micro GC injector die). It enables to
provide a consistent pressure output for samples of different pressures, which is critical to
produce reproducible GC performance. At the same time, both the regulator and the transfer line
are heated to prevent condensation. The output flow can be adjusted via a needle valve. The
tubing in the flow path are deactivated to avoid adsorption of active components. Adjusting three
key variables – temperature, pressure, and flow – can help ensure proper vaporization and an
accurate analytical result.
The GC Gasifier is powered by an external power adapter, and it is controlled by the gas
chromatograph (GC) through a USB serial cable. Main components of GC Gasifier include:
• Two inlets for either gaseous or liquefied samples, switchable by a manual 2 position 3 way
valve
• A heated regulator (the vaporizer), with a temperature set and controlled by the GC and
displayed in GC software
• A heated transfer line, maintained at a constant 100 °C
• A mechanical needle valve for purging in the vent line. Users need to manually turn on/off the
valve to start and end the purging.
• A mechanical needle valve for gas flow adjustment in the sample line. Users need to manually
adjust the gas flow entering GC as needed.
Gasifier parameters are listed in the following table:
Table 1
Parameter
Vaporizer
Transfer Line
When used with the Agilent 990 Micro GC, the gasifier mounts to the side of the Micro GC and the
transfer line connects directly to the front inlet.
When used with the Agilent 8860 or 8890 GC, the GC Gasifier mounts adjacent to the back inlet.
14
Gasifier parameters
Status
ON
Temperature (in the range of 30 °C and 150 °C, default at 100 °C)
ON
Temperature (Fixed at 100 °C)
Agilent 8860, 8890, and 990 Micro GC Gasifier User Manual
OFF
OFF