7 Top Mistakes in Car Catalyst Analysis
The analysis of automotive catalysts for further recycling is one of the most common tasks in today’s XRF industry. The need to analyze the chemical composition of automotive catalysts is due to the content of valuable platinum group metals – platinum, palladium and rhodium. Their content, and therefore the price of the catalyst, can vary greatly depending on the manufacturer.
Portable XRF spectrometers are very popular in the field of catalyst analysis. They provide results on the elemental composition of the sample with an accuracy comparable to laboratory analysis, while remaining compact and self-contained devices that can be easily carried everywhere. However, like any high-tech instrument, XRF analyzers require proper handling since measurement errors are likely to affect the accuracy of the results, which may result in incorrect catalyst value estimates. Among the major errors made when analyzing autocatalysts are the following:
Incorrect sample preparation.
This is the most common error in analysis, which will almost certainly lead to incorrect measurement results. Since autocatalysts are quite heterogeneous, meaning that different points in the sample may contain different amounts of valuable metals, in order to obtain information on the composition of the entire catalyst, it is usually crushed before the measurement is made. This is a very important step because the local concentration of valuable metals in a certain area of the catalyst may differ significantly from their concentration in the whole mass of the sample.
If for some reasons it is not possible to carry out grinding, it is necessary to use function of averaging of results of several measurements in different points of the catalyst. Such function is implemented in the software of all Elvatech XRF spectrometers. Although it cannot 100% replace proper sample preparation, it will make the analysis results much more reliable.
Insufficient measurement time
By its physical nature, the fluorescence spectrum has a statistical nature; therefore, if the measurement time is short, the contribution of fluctuations and noise to the acquired spectrum increases dramatically, which in turn leads to an increase in measurement errors. As a rule, for modern XRF spectrometers with PIN diode detectors the measurement time required to obtain reliable results is somewhat less than a minute. SDD-based analyzers are faster and give good results in less than 10 seconds. The ProSpector 3 ultra-high-speed XRF gun does the job in 1 to 2 seconds. It is easy to check for accuracy by doing one more measurement to see if the results are within the margin of error.
Use of a wrong calibration
The calibrations of a particular XRF analyzer are determined by the calibrations it is equipped with. Each calibration is made for a specific class of material. Analyzing autocatalysts with a spectrometer calibrated to analyze ores or precious metals, for example, will always give incorrect results.
Elvatech spectrometers and analyzers have a special calibration for the analysis of autocatalysts, which ensures high accuracy of the results obtained.
Measurement with unheated instrument
As a rule XRF spectrometers have a period of time required for the stable operation of the XRF tube. Measurements during this time can be unreliable, so it is advisable to let the device warm up for 5-10 minutes before analysis.
If you use Elvatech spectrometers, which have built-in temperature correction, the analysis can be carried out immediately after turning on the device.
The energy scale is shifted
When measuring XRF, the analyzer registers incoming radiation quanta and, based on their energy distribution, constructs a fluorescence spectrum. The instrument must correctly match the detector’s response to the energy of the detected quantum. For this purpose, an energy calibration is carried out, but over time the energy scale can fluctuate, which will affect the measurement results. Therefore, it is important to periodically check the energy scale of the instrument, and a standard sample is usually provided with the spectrometer for this purpose.
The Elvatech analyzers use an automatic energy calibration correction for each measurement, so you don’t have to worry about fluctuations in the energy scale.
Use of dirty film
All XRF analyzers use a special removable film to protect the detector. Over time, it becomes dirty, and particles of dirt or previous samples, will register in the measurements, distorting the results. Therefore, it is important to periodically change the protective film. At the same time it is worth watching the type of film, because they vary, and you should use the film with which the instrument was calibrated.
The ability to change the film without using tools in Elvatech spectrometers makes this procedure easy and fast.
Neglect of X-ray safety rules
Although it won’t ruin your measurements, you shouldn’t neglect radiation safety because regular exposure to ionizing radiation, even in low doses, can have serious health consequences. Use, if possible, a laboratory stand that is completely free of scattered radiation. The ProSpector 2 and ProSpector 3 handheld analyzers do not require a PC connection when operating in the lab stand, making them much easier to operate in this mode.
Thus, XRF spectrometers, although extremely easy to use, still require a responsible approach to analysis and sample preparation in order to obtain reliable results.