Problem: Moisture analysis is normally done using a precision balance with an incorporated heater. Ash analysis is done using a furnace or oven at a fixed temperature, requiring initial sample and crucible weighing, burning the sample in the furnace, cooling crucibles, and weighing again in a precision balance for final weight and calculation. Single-sample and multi-sample instruments exist to perform these analyses.

The major limitation of the singlesample balance method is that it is labor intensive. In addition to the operator involvement and possible errors made during manipulation, a large amount of bench space is needed for multiple balances.

The primary limitation of the multiplesample TGA batch method is the long batch processing time. With samples of varying size and composition, the cycle time is determined by the processing of the slowest sample. In addition, much time is wasted while waiting for the furnace to cool after analysis. This is because of the danger of burns, as well as the fact that no new samples can be loaded until the furnace cools to room temperature since the moisture lost by loading samples into a hot furnace will affect the final results of the analysis.

Solution: A new multiple sample TGA method developed by Navas Instruments allows samples of different composition, size, and/or weight to be analyzed while eliminating all of the previous limitations. The MMS-4000 will save laboratories money by reducing energy consumption, increasing productivity, and improving the accuracy and reliability of the results. In addition, the MMS reduces the likelihood of operator injury, since users will not have to work with tongs or high temperatures.

Principle of Operation:

1. Crucibles and samples are weighed on an external balance. The system has 2 balances that are calibrated to provide identical weight results.
2. Weighed crucibles with samples are then positioned by the operator in a fixed position in the external carousel auto-loader that will accommodate up to 83 crucibles.
3. Crucibles with samples are automatically introduced into the furnace with constant temperature (always hot); the furnace will accommodate 15 crucibles at any given time.
4. Multiple samples of various compositions and weights can be analyzed. Samples are processed individually for constant weight and are automatically removed when a specified number (1 – 15) of samples have reached constant weight. New samples are then automatically introduced. Slower or larger samples simply stay longer in the furnace, but do not delay the whole batch.
5. The system does not require constant operator attendance; therefore, it can work at night, or any time. The instrument can be programmed to perform different cycles sequentially; for instance, complete the analysis of moisture in all samples and then start the ash analysis cycle. The samples are automatically reloaded into the furnace, which then ramps to the ash temperature.
6. For labs with an even larger volume of samples, a system with 2 furnaces can be supplied to analyze moisture and ash simultaneously. Each furnace maintains a constant temperature; for instance, 130 and 600 degrees centigrade. The carousel auto-loader stays between the 2 furnaces and transfers crucibles from one furnace to the other.

This new patented instrument will considerably reduce analysis time and cost by eliminating previous macro batch TGA limitations and provide the food, minerals, environmental, and fertilizer industries, as well as many other fields, with a valuable tool previously unavailable.

For more information, visit www.navas-instruments.com.