ISSUE FOCUS 38 FEED & ADDITIVE MAGAZINE May 2023 where the sample weights are measured throughout the analysis sequence using an integrated 4 place balance. The carousel has a capacity of 19 samples plus one empty reference crucible for buoyancy correction. Weight loss is recorded for a fixed time or until weight constancy has been determined. When all samples show weight constancy for moisture, then the next step (e.g. ash at 550°C) can start and the instrument will automatically determine this parameter. If moisture only is needed as a parameter there is also a system with the same working principle but limited temperatures (up to 175°C) available, the TGM800. Typical results for moisture and ash analysis in feed samples are shown in Table 1. As seen, the results have a very high precision generally for homogenous samples an RSD of <0.5% can be expected. Most feed and food samples can be analyzed with the system using the same analytical setup. In comparison to the manual method, you will see an example in Table 2 that the results are perfectly matched for this specific sample. Moisture and ash values are precise and accurate, and the standard deviation is in most cases smaller compared to manual methods. The analysis time is normally significantly shorter with the TGA method compared to the manual measurements, since the desiccator step is not needed, and mass constancy is automatically determined during the run. Moisture and ash – determination with automated primary TGA methods is saving time and manual labor of the lab. The TGA and TGM systems are working simultaneously for multiple samples with full documentation of the sample results and all method steps. Generally, the critical requirements of analytical standard methods like temperature control, mass resolution and precision, furnace atmosphere and flow, analysis time or mass constancy criteria can be matched. Sample Type Initial weight Moisture Ash Ash Dry N Corn Silage Distillers Grain Alfalfa Wheat Flour ~1g ~1g ~1g ~1g 8.07 ± 0.05 6.92 ± 0.07 10.59 ± 0.15 7.52 ± 0.02 10.00 ± 0.02 5.49 ± 0.02 4.48 ± 0.07 1.49 ± 0.07 10.88 ± 0.02 5.90 ± 0.02 5.41 ± 0.08 1.62 ± 0.07 10 10 10 10 Table 1. Typical results for feeds or plant tissue TGM 800– Moisture only analyzer. About Michael Jakob Michael Jakob, European Field Product Manager at LECO Europe, studied material science at the FAU Erlangen-Nürnberg. Since 30 years Michael is working for LECO in different positions. He is responsible for technical information and communication of analytical methods and procedures. Name Manual Method TGA Method Initial Mass Moisture Moisture Ash Ash Initial Mass Alfalfa sample 1 Alfalfa sample 2 Alfalfa sample 3 Alfalfa sample 4 Alfalfa sample 5 1.0377 1.0395 1.0259 1.0068 1.0179 Average SD ± 6.56 6.60 6.51 6.51 6.52 6.54 0.04 9.91 9.92 9.98 9.92 9.91 9.93 0.03 1.0347 1.0039 1.0209 1.0110 1.0167 Average SD ± 9.95 9.99 9.98 9.97 10.01 9.98 0.02 6.45 6.46 6.46 6.46 6.46 6.46 0.01 Table 2. Comparison results Manual method – automated TGA method
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