GC Solution for the Automated Analysis of Benzene in Air

To reduce exposure to air pollution several limits and target values for air quality have been set. The maximum value for benzene exposure is currently set at 0.7 mg/m3 (0.2 ppm). To determine Benzene in air Da Vinci Laboratory Solutions developed an automated GC solution equipped with a special gas sampling unit that allows the sampling up to 8 gaseous samples. This proven sampling technique has been used for the analysis of VOC in air.

GC Configuration

The Benzene in Air application (Figure 1) is based on an Agilent Technologies 7890B GC configured with a FID or TCD and a custom programmed temperature vaporization (PTV) injector. The application is equipped with an analytical column and pre-column to backflush the hydrocarbon matrix.

The sampling unit uses a sampling pump, a mass flow controller and a multi-positioning valve. The multi positioning valve allows to collect samples from e.g. a Tedlar bag or taking sample directly from outside air. Up to 8 samples or standards can be automatically selected and sampled as shown in Figure 2.

Automated Analysis

Collect the samples in Tedlar bags and use the stream selection valve to select either standards, samples and/or multiple samples for an automated analysis. The system’s PTV injection port is modified to contain a sorbent tube as injection port liner which ensures a rapid absorption and desorption of Benzene.

Alternatively collect the sample on a sorbent trap using a programmable sampling pump. The sorbent trap is placed in the PTV inlet and automatically purged prior to thermal desorption and subsequent analysis.

The gas sampling unit automates the process of sampling, absorbing and desorbing. After benzene has eluted from the precolumn to the polar column, the remainder of the matrix is backflushed to vent. The Benzene in Air analysis requires 25 minutes as shown in Figure 3.

To extend the analysis to C6-C8 aromatic compounds (BTEX Analysis) just switch the backflush after elution of o-Xylene.

Excellent Repeatability

The Benzene in Air application shows an excellent performance using a custom calibration standard. Figure Three displays the analysis of 1.1 mg/m3 Benzene in Air Standard containing 0.1% VOC’s

Features of the Benzene in Air Application

• Automated gas sampling, absorbing and desorbing
• Based on proven sampling technique for VOC in Air
• Various options for sample collection possible
• Up to 8 samples or standards can be selected and sampled
• Analysis can be extended to BTEX in Air
• Excellent performance specifications

For more information on the DVLS Benzene in Air analyser please contact Da Vinci Laboratory Solutions.