Oct-2020

Optimise your workflow and improve lab efficiencies

XOS’ Sindie® series sulphur analysers offer a variety of features and capabilities aiming to improve your operational efficiencies. In addition, XOS’ applications scientists have worked with a wide range of customers to develop best practices and techniques that can further reduce measurement and calibration times while maintaining and improving precision and method compliance.

Satbir Nayar
XOS

Article Summary

XOS’ Sindie 2622 is renowned for its precision, accuracy, and ease of use. This analyser is available in a variety of configurations, such as Sindie 2622 Generation (Gen) 3, which has higher-performing optics and superior analytical performance in addition to a lower limit of detection (LOD) and better precision at low sulphur levels. It also offers significant time-saving capabilities, including enhanced optics to reduce background measurement time in 2622 measurement mode and the use of preassembled Accucell sample cups.

Challenge
Regardless of the instrument used, ASTM D2622 first requires that a background measurement be taken, followed by the sample measurement. When run in 2622 mode, Sindie 2622 performs a background measurement automatically – a feat accomplished through slight movement of the sample during the measurement. Per method requirements, the background measurement is taken first, followed by the sample cup being lowered into the basket for sulphur measurement. The analyser automatically subtracts the background measurement from the sulphur measurement, providing the net sulphur concentration of the sample.

Sindie 2622 Gen 2, when run in 2622 mode, requires the background measurement time to be equal to the sample measurement time. During the standard 300-second sulphur measurement time, an additional 300 seconds of background measurement time is required, for a total cycle time of 600 seconds per sample. Because ASTM D2622 requires duplicate measurements for samples with less than 100 ppm sulphur, the resultant total time to measure a typical finished product sample is 1200 seconds (20 minutes).

Solution
In comparison to Sindie 2622 Gen 2, Sindie 2622 Gen 3 offers a time-saving solution which reduces total cycle time in 2622 mode by 38%, or more than 7 minutes per sample. This is because Sindie 2622 Gen 3 has advanced optics and newly-updated software that allow the background measurement time to be reduced to only 20% of the total measurement time, with complete compliance with ASTM D2622 and no detrimental impact on analytical performance. For a typical 300-second sample measurement time, the background time can be reduced from 300 seconds to only 75 seconds. The resultant 375-second measurement time on Sindie 2622 Gen 3 is 225 seconds shorter than on Sindie 2622 Gen 2 — a 38% reduction. For samples below 100 ppm that require duplicate measurements, this feature results in a time savings of more than 7 minutes per sample! For a typical lab running 10 to 25 samples daily, this is a time savings of 1 to 3 hours per day, or 15 to 45 hours per week — while maintaining full compliance with ASTM D2622 and with no negative impact on precision or accuracy.

Utilising Sindie 2622 Gen 3 with XOS’ preassembled Accucell sample cups, regardless of running in 7039 or 2622 mode, provides additional time savings. These preassembled cups only need for the operator to pipette about 1 ml of sample into the measurement cup without needing to fumble with cup rings or sample film. The several seconds saved per sample may not seem like much, but over the course of a day or a week in a standard lab, this can result in significant time savings. With standard sample cups, even the best of operators will occasionally have cases where the ring does not seat properly on the cup, resulting in the waste of consumables and samples, as well as time, as they must start over. If not noticed, improper seating of the ring will also often result in leakage of the sample onto the instrument, leading to additional time lost to stop and clean up the analyser. This, in turn, increases the chances of cross- contamination of samples.

Conclusion
Sindie 2622 Gen 3 offers a time-saving solution with the option to reduce the background measurement time to 20% of the total measurement time.
Compared to Sindie 2622 Gen 2, Sindie 2622 Gen 3 offers:

- Reduced background measurement time in 2622 mode (shown in Figure 1), reducing cycle time by almost 4 minutes per single measurement and more than 7 minutes per sample for duplicate D2622 samples.
- Use of preassembled Accucell sample cups, saving time and waste in addition to minimising risk of contamination.

More About the Sindie Series
The entire Sindie 2622 product line offers several features, add-ons, and capabilities that further enhance the efficiency of your lab, including:

- Eliminating need for background measurement time by utilising 7039 mode
- Eliminating need for duplicate measurements for samples ≤100 ppm by utilising 7039 mode
- Saving time by preloading up to eight samples into the Sindie autosampler add-on feature
- Improving operational efficiencies by following the best practices developed through years of experience by the XOS Applications Team

In addition to the enhanced X-ray optics and software that allow for a reduction in background measurement time in 2622 mode, all Sindie 2622 analysers also offer a feature that allows the instrument to run in 7039 mode. ASTM D7039 is a more recent sulphur method that better represents the most current XRF technology. ASTM D7039 is a well-established method that provides equal, if not better* (see Figure 2 comparing real-world precision between D7039, D2622 and D5453) precision than ASTM D2622 for low levels of sulphur in hydrocarbons.

Figure 2: PTP Graph

Unlike ASTM D2622, ASTM D7039 does not require a background measurement cycle. This is because when ASTM D7039 was developed, X-ray Fluorescence (XRF) technology had advanced to the point where background measurements were no longer needed to provide high precision at low sulphur levels through the use of a monochromating excitation optic. ASTM D7039 makes use of a newer technology: Monochromatic Wavelength Dispersive XRF (MWDXRF), which provides a lower signal-to-background ratio, meaning background measurement is not necessary to achieve high precision at very low sulphur levels. The filtering and focusing capability of the excitation optic means that the background noise is removed from the incident X-rays prior to sample excitation, which results in a daily time savings that ultimately amounts to several hours per week.

ASTM D7039 does not require duplicate measurements on samples. This, combined with being able to measure without background measurement, results in a time savings of up to 15 minutes per sample (for ≤100 ppm samples). Over the course of a week in a typical lab, this reduces the time needed to measure samples by 10 to 25 hours per week.