Large-Volume Injection PTV-GC-MS Analysis of Polycyclic Aromatic Hydrocarbons in Air and Sediment Samples

Abstract

For the analysis of trace organic pollutants in environmental samples using a gas chromatographic (GC) instrument, large-volume injection using the programmable temperature vaporization (PTV) technique has many advantages over the traditional split/splitless injection. By increasing the injection volume from 1 or 2 microL with a split/splitless inlet to 60 microL or higher with the PTV inlet, analytical sensitivity is greatly enhanced for analytes with low concentrations. Results obtained from optimization of instrument operational parameters for analyzing polycyclic aromatic hydrocarbons (PAHs) are reported in this paper. The laboratory method detection limits for 16 PAHs and six deuterated PAH surrogates were determined using seven replicate spike samples. The initial temperature of the inlet was found to be critical in determining the analytical sensitivity of PAHs with two or three rings due to loss of these relatively highly volatile compounds during solvent vaporization. For most PAHs, the response of the mass spectrometry detector increased proportionally as the total injected volume was increased up to 150 microL. Significant interference from rubber material of the sample vial septa was observed.

Comprehensive two-dimensional gas chromatography using large sample volume injection for the determination of polynuclear aromatic hydrocarbons in complex matrices

“…Within the conventional one dimensional GC, PTV solvent split technique is the most common approach to large sample volumes injection for the determination of semi-volatile compounds as PAHs, especially if contained in complex or dirty matrices [4,5]. This technique is actually robust towards contaminants and to be preferred in respect to large volume on-column techniques which are more suitable for relatively clean samples and for volatile and/or thermally labile compounds.…”

Analysis of Polycyclic Aromatic Hydrocarbon Using Programmable Temperature Vaporization Inlet Couple with Gas Chromatography Mass Spectrometry (PTV-GC-MS)

“…When total injection volume increased to 200 μL, peaks shown in the chromatogram become distorted and peak tailing is observed as shown in Figure 2(B) when compared to the peaks in chromatogram (Figure 2(A)), which is obtained from 10 μL injection volume. According to Norlock et al [15], this is due to overloaded solvent that is injected into the inlet and subsequently flooding is occurred in the inlet liner. However, increasing the injection volume of PAHs solution into inlet produces more satisfactory RSD values (Figure 1(A)).…”

“…This is because for most PAHs, the response of the mass spectrometric detector increases proportionally to the total injection volume. Besides that, by eliminating or shortening the solvent evaporation step, which is time consuming and subject to loss of chemicals due to elevated high temperature or in vacuum condition, tedious sample pre-treatment procedures can be simplified [15]. The aim of this study was to optimize the conditions of PTV solvent vent injection mode in order that the sensitivity of the analysis of five PAHs can be enhanced.…”

“…Such low concentration levels are impossible to make in-depth investigation of PAHs becomes successful due to insufficient amount of the collected samples for instrumental analysis even though large volume of sample is used. Most of the times, instruments do not have the capability to detect the PAHs and not detected results are reported quite often [15]. Because of this, a new pre-concentration methodology is necessary to be developed for investigation of trace amount of PAHs in environmental samples such as air, water, soil and etc.…”

“…split, pulsed split, splitless, pulsed splitless and solvent vent modes [23]. Due to its complexity compared to traditional splitless inlet, optimization of the PTV inlet conditions is necessary in order that it can handle sample with wide range of concentrations [15]. PTV may transfer maximum of 500 μL of a liquid sample to the GC inlet through multiple injection using a typical 50-µL syringe, which can inject up to 25 µL for each injection [24].…”