Zetium Ultimate edition
The long-term durability of a vehicle’s exhaust catalyst is essential for emission control. Catalyst durability can be affected by a variety of factors including engine oil consumption. During normal engine operation, some of the lubricating oil is combusted. The deposition of combustion products from phosphorus containing lubricant additives on the catalyst can adversely affect catalyst efficiency and durability. Therefore, the phosphorus content in fuels like gasoline is limited by several regulations, like the US EPA limits P at 0.0013 g/l (0.0018 g/kg) gasoline. This report demonstrates that Zetium Ultimate edition can easily analyze phosphorus content in gasoline.
This study was performed using a Zetium wavelength dispersive XRF spectrometer. It was configured with a 4 kW Rh anode, SST R-mAX tube and is a fully integrated system with a X-Y sample handler and state-of-the-art SuperQ software, featuring an advanced Fundamental Parameters algorithm. Zetium is engineered for excellence in terms of both analytical accuracy, precision and operational performance.
Sample preparation and measurement details
Ten grams of commercially available phosphorus standards (VHG Labs Inc.) were poured into 38 mm disposable liquid cells, prepared with 3.5 µm polyester film (Hostaphan).
Precision and instrument stability
The precision and repeatability of the Zetium Ultimate edition is excellent. A summary of the test results are listed in Table 1.
Table 1. Analytical precision.
The repeatability of measurements of a gasoline sample containing 1.1 mg/kg phosphorus is illustrated in Figure 1.
Figure 1. Repeatability measurements of phosphorus in gasoline. Dashed lines indicate 3σ standard deviation of the mean value.
The accuracy of the calibration is illustrated in Figure 2. The calibration RMS value (0.2 mg/kg) corresponds to a comparison of the certified chemical concentrations of the standards with the concentrations calculated from the regression.
Figure 2. Calibration graph for phosphorus in gasoline fuel
The lower limits of detection (LLD) for phosphorus in gasoline are given in Table 2.
Table 2. Detection limits of phosphorus in gasoline fuel
Detection limits on mg/kg-level are possible for relatively short measurement times, for example an LLD of 1 mg/kg can be achieved in a measurement time of 12 s.
The analysis of phosphorus in gasoline fuel by WDXRF is a fast, relatively simple analytical technique. As demonstrated, Zetium Ultimate edition is capable of accurate and precise analysis of phosphorus in gasoline fuel. Sub-mg/kg detection limits ensure that the Zetium Ultimate edition is able to meet requirements of the industry and environmental regulations even as more stringent government regulations come into force.