1. 012345 Time [minutes] H 2 S MeSH 50% propane matrix Column:Silica PLOT 30m*0.32mm Oven: 100 ° Cisotherm Flow: 2.0 ml/min He Inj: 100µl, split 1:40 Det:PFPD < 60% recovery of H 2 S COS Accurate trace level quantification of sulfur Unlike GC columns with silica stationary phases, the Agilent J&W Select Low Sulfur GC column is highly inert in the presence of sulfur components, drastically lowering detection limits. Conditions Column: Agilent J&W Select Low Sulfur 60 m × 0.32 mm (Agilent part #CP8575) Oven: 65 °C Isotherm Carrier gas: Helium, constant flow, 2.0 mL/min Injection volume: 1 mL Injection: Gas sampling valve Figure 2. 7890 GC-SCD Application of sulfur compounds in propylene The stationary phase shows good selectivity between H 2 S, COS, and low mercaptans in various C3 hydrocarbon matrices. Co-elution of the sulfur components and the matrix, which causes “quenching”, is avoided. 7890 GC-SCD The system was equipped with a gas sampling valve. The detector settings are shown in Table 1. Introduction Table 1. Detector SCD Settings Hydrogen sulfide (H 2 S), carbonyl sulfide (COS), and methyl mercaptan (MeSH) are common components in light hydrocarbon streams. They have corrosive and toxic properties, causing damage to pipes and equipment. The emission of undesired odors caused by volatile sulfur compounds in intermediates and final products have serious economic and environmental impact. In addition, the presence of sulfur can affect the performance of industrial processes, causing undesired chemical reactions, loss of catalyst activity (catalyst poisoning), and ultimately lower yield. These sulfur components must be quantified at low parts per billion (ppb) levels. They can be measured with sulfur specific detection devices such as the Sulfur Chemiluminescence Detector (SCD) and Pulsed Flame Photometric Detector (PFPD) but large sample volumes are needed to reach the desired low ppb detection limits. This creates matrix overload and quenching effects (decreased signal/sensitivity due to background interferences) on most sulfur specific detectors, limiting the detector’s sensitivity and linearity and raising quantification limits. The capillary PLOT column, Agilent J&W Select Low Sulfur column, with a novel stationary phase was developed for the analysis of sulfur species such as H 2 S, COS and MeSH in light hydrocarbon C3 matrices, with high loadability properties and unique selectivity giving baseline resolution for sulfur components and matrix components. GC Columns for ppb analysis of H 2 S and COS Capillary GC columns for the ppb analysis of H 2 S and COS in C3 matrices should ideally fulfill the following criteria: 1. Highly inert, providing good H 2 S response levels at < 100 ppb. 2. Good separation between H 2 S/COS and ethylene or propylene matrix avoiding detector quenching. 3. High sample capacity, catering for the larger injection volumes needed for low ppb level detection. Some advantages and limitations of commercially available columns used for H 2 S and COS detection: Non-Polar Liquid Phase, Thick film PDMS 3 - 5μm Highly inert phase with high H 2 S responses Not selective, H 2 S/ethylene, COS/propylene co-elution Porous polymer, DVB porous polymer Absorption of H 2 S already at low ppm levels H 2 S/COS and propylene well separated Porous Silica, COS/ethylene, propylene well separated H 2 S/ethylene, propylene well separated Absorption of H 2 S a low ppb levels Results and Discussion  The Agilent J&W Select Low Sulfur column used in a GC with a sulfur specific detector, such as an SCD or PFPD, can detect H 2 S, COS, and MeSH at trace levels in a propylene matrix as a result of excellent separation of the sulfur compounds and the matrix.  Separating the matrix from the sulfur components eliminates the “quenching” effects caused by the matrix. This provides a better response for the sulfur compounds. The column provides a good response for reactive sulfur compounds, such as H 2 S, making detections of 20 ppb possible.  Although this is a PLOT column, no spikes will be observed because the column does not shed particles. It can therefore be used safely in combination with switching valves.  H 2 S elutes together with ethylene this makes the column unsuitable for the ppb H 2 S detection in ethylene feeds. Results of the Agilent J&W Select Low Sulfur GC Column on a 7890-SCD system The Agilent J&W Select Low Sulfur column addresses the specific needs of petrochemical chemists who need lower detection limits for sulfur components in propylene. The unique selectivity and inertness offered by this new column provides significantly lower detection limits due to highest inertness towards volatile reactive sulfur components. The unique selectivity and no-particle shedding results in more reliable, higher-quality data. In Figure 5 the linearity of the sulfur compounds are shown using the column in combination with an SCD detector. A 24-hour sequence of programmed runs shows a nice reproducible signal for H 2 S, COS, and MeSH. Results are shown in Figure 6 and Table 3. Elution of Hydrocarbons on Select Low Sulfur GC Column Pittcon 2011 Poster # 940-12 P Results and Discussion Conclusions Results and Discussion PLOT Column Choices for ppb Level Detection of Sulfur Compounds PLOT Column Choices for ppb Level Detection of Sulfur Compounds Johan Kuipers, Helena Jacobse, Max B Erwine, Frans Biermans Agilent Technologies, Inc. These columns tend to exhibit adsorption of H 2 S and COS, limiting recoveries as shown on a porous silica PLOT. PFPD settings Air (1)17 mL/minTube voltage550 V H213 mL/minSampling delay6 ms Air (2)10 mL/minSampling width20 ms Trigger level250 mV SCD settings Burner temperature800°C Vacuum of burner370 torr Reactor hydrogen flow40 mL/min Reactor air flow65 ml/min Ozone air pressure5 psig Experimental and Results 7890 GC-SCD Injector: 200°C, split 1:10 Detector: SCD, 200°C Sample: Propylene matrix with ~300 ppb H 2 S and MeSH, ~500 ppb COS GC-PFPD Injector: 200°C, split 1:20 Detector: PFPD, 200°C Sample: Propylene matrix ~500 ppb H 2 S, COS and MeSH Conc [ppb] pg S on column Average area % RSD H2SH2S47561.634261.9% COS47161.136311.8% MM48362.731461.6% Mercaptans Natural gas Methyl mercaptan Ethyl mercaptan Propyl mercaptan Butyl mercaptan C2C1C3 Iso-C4C4 Iso-C5 C5 Figure 1. H 2 S and COS response on a silica PLOT Figure 4. Chromatogram of H 2 S, COS and MeSH in Propylene using the Agilent Select Low Sulfur with GC- PFPD. GC-PFPD The system was equipped with a gas sampling valve. The detector settings are shown in Table 2. Table 2. Detector PFPD Settings Figure 3. Chromatogram of H 2 S, COS and MeSH in Propylene using the Agilent Select Low Sulfur with 7890 GC-SCD. Table 3. Reproducibility during 24-hour sequence Figure 6. Reproducibility of programmed runs on a 7890-SCD Figure 5. Linearity of active sulfurs, 20 ppbv - 290 ppbv, SCD The figure below shows an mirror of natural gas and the elution of mercaptans. Figure 7. Analysis of H 2 S, COS and MeSH in N 2 approx. 20 bbpv. Figure 10. Mirror plot of natural gas and mercaptans, FID Chromatogram courtesy of R. Gras and J. Luong, Dow Chemical Canada, Analytical Technology Centre Figure 8. Natural gas, elution profile of methane Chromatogram courtesy of R. Gras and J. Luong, Dow Chemical Canada, Analytical Technology Centre The PLOT behavior of the Select Low Sulfur stationary phase is evident from the characteristic overload elution profile of adsorption gas chromatography. Conditions: Column: Select Low Sulfur, 60m*0.32mm Oven: 65°C (6.5) --> 185°C Flow: 2.0 ml/min, Helium Detector: PFPD Inj. volume: 1mL, split ratio 25:1 Sample: 75%propylene, 23%propane Figure 9. H 2 S and COS in propylene/propane on the Agilent J&W Select for Low Sulfur. Data courtesy of L. Chambers, OI Analytical, College Station, TX The column appears to be well suited for the accurate detection of ppb level H 2 S and COS in propylene/propane streams of variable concentrations without noticeable absorption of H 2 S. H 2 S, COS, and MeSH in 50% propane on a silica PLOT