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Reference Material

USE OF REFERENCE MATERIAL AND CONTROL CHARTS
Control samples are typically analysed in duplicate and the average value plotted on a control chart. The average value is only calculated if the difference between the duplicate analyses is acceptable. As an example, the acceptable difference for ISO ash is usually 0.20%. A control chart must have the following lines drawn on it as guides when plotting the daily values: the average value line, warning limit lines (above and below the average line), the upper control limit, lower control limit and the range. It is imperative that the control sample used is stable as degradation can result in a bias on the control chart. The bias can then be incorrectly assigned to faulty equipment, incompetent analyst, flawed technique or unknown discrepancy during analysis. If the average result of the control sample is found to be out of the upper or lower control limits, the analytical results of the batch of samples analysed should be treated as suspect. Further testing should stop and the root cause of the problem ascertained. Once the root cause has been identified and eliminated, work may commence and the control sample re-analysed.

Coal Certified Reference Material

ASH Certified Reference Material

HGI Standard Reference Material

Benzoic Acid Reference Material

Abrasion Index Reference Material

Coke Reference Material