Explore how to control the poor reproducibility in the determination of K content in compound fertilizers!
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Colleagues, when testing the potassium content in compound fertilizers, it is common for the obtained K content values to not be consistent. Let’s discuss what the main issues are
It doesn’t make any sense to say that. If the measurement data are not parallel, it is best to express them in terms of deviation; if the measurement data fall within the allowable deviation range specified by the analytical method, then the data can be considered reliable. There is no data; it is only a qualitative indication that the data are not parallel, so it has little practical value.
Well, it was my mistake in phrasing things; 90% of the deviations that occur are still within the limits set by the national standards. But this remains a significant issue for our laboratory technicians – when different technicians carry out the tests, the deviations become relatively larger, around 0.5 units. This level of deviation is still within the acceptable range. I’ve also checked the national standards; let’s discuss and learn from this together.
For the same sample, the differences in measurement results obtained by different people are referred to as reproducibility; in other words, such variations arise from different people using different analyzers or in different analysis environments. This is actually a difference between individual testers, and the allowable deviation for reproducibility is generally larger than that for repeatability. By training the testers in basic operations and sample analysis in accordance with standards, their technical skills can be improved, as well as their ability to determine the end points and interpret the analysis results; this leads to better reproducibility when measuring actual samples.
In fact, the real reasons include not only errors in the laboratory’s own testing methods but also the individual shortcomings of the testers. Fertilizers themselves do not have evenly distributed nutrients during the production process; they are of the blended type (tower-type fertilizers are somewhat better in this regard). So it’s not that perfect.
For potassium determination by gravimetric method, the following points should be noted during analysis: 1. Add a precipitant and control the pH value. 2. Precipitate transfer operation. 3. Precipitate washing. 4. Are the constant weight conditions before and after in the crucible the same?
Well, I’ve taken note of all that. Thank you for the explanation.