Elemental Analysis Using the Spectroil Q100 Spectrometer

Using the time-tested technology of rotating disc electrode (RDE) atomic emission spectroscopy, the Spectroil RDE spectrometer performs wear debris analysis, a key analytical process of any oil analysis program. There are two models of the Spectroil RDE spectrometer available, namely the Spectroil M and the Spectroil Q100.

The Spectroil M is a portable version used in military applications as outlined by the DoD JOAP program (Figure 1). The Spectroil Q100 is a compact, benchtop system employed in commercial applications (Figure 2). Both variants are user-friendly and rapidly yield reliable results for additives, impurities and wear metals present in lubricants.

Figure 1. Spectroil M

The Spectroil series is a proven technology for lubricant condition monitoring. The Spectroil series spectrometers have improved in terms of reliability and performance over the years, thanks to the advances in the optics and software algorithms.

Figure 2. Spectroil Q100

Redesigned Optics

The optics are the heart of any optical emission spectrometer and play a key role in the limits of the sensitivity, repeatability and reproducibility of the instrument. The in-house fabrication of all the Spectroil optics enables Spectro Scientific to get complete control over the products and capabilities, thereby improving the performance and quality of the system.

Tables 1 and 2 summarize the repeatability and sensitivity of the new Spectroil optics calibrated using the commercial CS-24 program. The repeatability of the Spectroil optics at 10ppm surpasses the requirements of the ASTM D6595 standard.

The reasons behind this superior performance of the Spectroil optics include the design of the optics, the in-house, reliable fabrication of the optics and the software employed for interpretation of results.

Table 1. Repeatability (typical) of 10ppm listed by element

Table 2. Typical LODs (ppm, 3σ) listed by element for the commercial program

Redesigned Data Processing

The Spectroil is a smarter instrument, thanks to the use of a peak search algorithm. Since the Spectroil is generally used in non-ideal laboratory environments, the changes in conditions such as altitude, humidity and temperature can cause the analytical peaks of each element to shift slightly on the CCD array.

This shifting of the peaks from their expected location leads to a "drift" of the standardization of the device (Figure 3). As a result, customers using the transportable Spectroil M under dynamic operating conditions have to run multiple profiles in a day.

Figure 3. Raw Spectroil data for Na line 588.995 at several operating temperatures.

For this reason, the instrument drift needs to be compensated for obtaining accurate results. At the analytical line, the intensity of the line is quantified and is varied with the concentration of a specific element. The analytical line remains unchanged in the case of a routine measurement, but its position is adjusted by an instrument profile.

Users will get erroneous results if they fail to run an instrument profile subsequent to the changes in the changes in the environmental conditions. This issue can be addressed with a peak searching algorithm by enabling the software to locate the peak position automatically during a measurement even if there is a peak shift caused by environmental changes.

The effectiveness of the new peak searching capability of the Spectroil is demonstrated by analyzing a sample under different operating conditions without running an instrument profile (Figure 4). In Case A, the peak is slightly shifted to about 2 pixels due to changes in the operating temperature (Condition 1 to Condition 2, difference of 4°C). If the user neglects to run an instrument profile to compensate for this change, this could lead to erroneous results (could be up to 70%).

Figure 4. Demonstration of how peak searching compensates for instrument drift.

Case B demonstrates the advantage of the peak searching algorithm of the Spectroil, by which the measurement accuracy is retained by automatically aligning the analytical line with the new position of the peak prior to reporting the results.

Figure clearly shows the advantage of the new peak searching algorithm. The consistent results are obtained over the entire temperature range through the implementation of the peak searching algorithm.

Figure 5. The peak searching capability is a powerful tool to help the user obtain the most reliable results

Conclusion

The advances in the production and data processing techniques have enabled improvements in the sensitivity and performance of the Spectroil M and Q100. Since Spectro Scientific fabricates the optics in house, it can optimize the flexibility and quality of the platform for future improvements in RDE technology.

The Spectroil instruments have become smarter with the new peak searching capability in the signal processing, making them more adaptable to dynamic operating environment without any user assistance.

This information has been sourced, reviewed and adapted from materials provided by AMETEK Spectro Scientific.

For more information on this source, please visit AMETEK Spectro Scientific.