8
Analytical Instrumentation
Total Sulfur at Ultra Trace Level with Nitrogen Oxide Elimination Technology (NO-ET)
When analyzing Total Sulfur in Petroleum Products and Derivatives at trace level (<1ppm), interference of high Nitrogen concentrations becomes signifi cant. TE Instruments developed Nitrogen Oxide Elimination Technology (NO-ET) in order to analyze the true amount of Total Sulfur at trace level in samples that contain high quantities of Nitrogen.
During combustion, the amount of Nitrogen present in the sample is converted into Nitrogen Oxide molecules (NO2
light at the same wavelength as SO2
). The NO-molecules interfere by emitting during the absorption and excitation
stage of UV-Fluorescence detection technique. Resulting in a false (positive) contribution of 0.4% Nitrogen to the measured amount of Total Sulfur.
The innovative XPLORER-S and, in particular, its UV-Fluorescence detector has reduced sensitivity to the false contribution of NO. When absolute elimination is required, the XPLORER-S will be tailored with NO-ET. The NO-molecules are destructed which prevents incorrect measuring of ultra- low (<1 ppm) Total Sulfur concentrations.
Cumene is the common name for Isopropyl benzene, an organic compound which is an aromatic hydrocarbon present in Crude Oil and Refi nery Fuels. During the production process wherein Benzene is converted to Cumene, expensive zeolite-based catalysts are used. The catalyst material is affected by Sulfur compounds present in Benzene. By measuring Total Sulfur in the fi nal product, determination whether and when the catalyst require replacement can be achieved more accurately.
To demonstrate the effect of TE Instruments’ solution against Nitrogen Oxide interference, a Cumene sample was measured on a XPLORER-NS and a XPLORER-S equipped with NO-ET, introduced by the ARCHIE liquids auto sampler:
The mathematical approach containing typical correction of 0.4% for NO matches.
The results with interference are 295.52 µg/L for Total Sulfur and 22.79 mg/L for Total Nitrogen.
• 22.79 : 100 x 0.4 = 91.16 µg/L
• 295.52 – 91.16 = 204.36 µg/L Sulfur as corrected concentration
The XPLORER-S equipped with NO-ET provides 199.87 µg/L as a result which demonstrates that the interference is almost completely eliminated.
To demonstrate the ultimate sensitivity of the XPLORER-S equipped with NO-ET, the Cumene sample was diluted and measured under the same conditions:
The XPLORER-S provides a repeatability (%) lower than 5% at trace level in a high Nitrogen containing Cumene sample. The above shown data clearly proves the effectiveness of the NO-ET for this application. Note: All solvents and gases (Ar/O2
) must be of high purity to accurately measure Total Sulfur at trace level.
For more information regarding TE Instruments’ solution against Nitrogen Oxide Interference, contact our Sales Team (
sales@teinstruments.com).
41294pr@reply-direct.com
For More Info, email: email:
For More Info, email: email:
Matrix effects, or differences between the elemental composition of test samples and the calibration standards, can often result in biased chlorine measurements. These effects can be compensated for with the utilization of one of two methods. First, the selection of calibrants that match—as closely as possible—the test sample matrix. This is especially true for materials containing oxygen, for instance E85 (85% ethanol in gasoline). The closer the calibration matrix refl ects the actual test samplers, the better the results will be. Secondly, one can employ the use of a matrix correction factor. Commonly used in the refi ning industry, users will typically apply a matrix correction factor for measurement of aqueous samples on a hydrocarbon based calibration curve.
In this procedure, the analyst will pipette 5-8 ml of sample into a sample cup and test in the XOS Clora using Etnom XRF fi lm. The standard analysis time for samples containing >1 ppm chlorine is 300 seconds. If the sample contains <1 ppm chlorine, a 600 sec measurement time is suggested for optimal results. In addition, if the sample contains >1 wt% sulphur, use of a sulphur correction table is recommended help improve results. If a water-based calibration curve is used when measuring aqueous samples, a matrix correction factor is not needed. When the aqueous sample is measured on a hydrocarbon curve, high oxygen content, when not accounted for, will result in reduced counts and a falsely low chlorine value. If a dedicated water curve has not been developed, multiply the results obtained using a hydrocarbon calibration curve by 250% (or 2.50).
Total chlorine of aqueous samples measured on water based calibration curve: Total chlorine (ppm) = measured chlorine
Total chlorine of aqueous samples measured on hydrocarbon based curve: Total chlorine (ppm) = 2.5 * measured chlorine
For More Info, email: email:
For More Info, email: email:
For More Info, email: email:
For More Info, email: email:
37144pr@reply-direct.com
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Measurement of Aqueous Samples on a Clora Hydrocarbon Calibration Curve
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