Issues with retaining samples for industrial analysis
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Recently, our Quality Inspection Department plans to carry out random inspections of coal and coke. The inspections will be completed on the same day for the samples collected the previous day; the main task is to conduct industrial analysis on those small samples of coal and coke (samples with a size of <0.2 mm) that were prepared and stored the previous day. I would like to ask how your laboratories handle the sample storage Are there two situations? 1. After putting the samples into bags, place them in the drying tower; during sampling, take them directly from the drying tower, weigh them, and then burn them ； 2. Should the sample retention bag be kept indoors, and only placed in the drying oven for drying when sampling is required later? Would a second drying cycle have a significant impact on the internal moisture? How are the time and temperature for the second drying step controlled?
I feel that whether it is kept dry or dried later, different testing methods should use data obtained from experiments to prove whether there is an impact. One should not rely solely on what others do; after all, the coal used by each manufacturer is different, as are the environmental conditions.
Reply to 1# happyzojn: In our company, the retained samples must be properly sealed and signed. Moreover, no matter how the samples are prepared, the analysts still need to dry them before conducting the analysis, mainly to remove moisture
Reply to 3# Farmer: How does your company handle sample retention? Are large samples left, or are small samples <0.2 prepared? We are currently testing a large number of batches; to simplify things, we use samples with a size of less than 0.2. However, the humidity here is high, and several comparison tests conducted today showed that it has a significant impact on the internal moisture content of these samples. Why does GB/T212 specify repeatability only for Mad, but not reproducibility? Why does Vad only show repeatability when determining volatiles, while only Vd shows reproducibility?
Large samples are stored for 7 days, while small samples are stored for 1 month. As an analysis laboratory, only small samples are retained – why is the moisture content high? Our samples have been dried during production; otherwise, how could 0.2 be achieved?