Digestion is the process of breaking down substances into their basic constituents, typically by using reagents such as strong acids, alkalis, or enzymes. It causes the complex matrices of compounds to gradually decompose and separate into distinct elements of interest which can be further refined to be used as intermediate goods or purified for study. But how do digesters work?
In this article, we won’t cover the large-scale industrial digesters used for agricultural waste and sewage treatment. We will instead focus on benchtop and lab-scale digesters used in analytical sample preparation.
Two Types of Digesters: HotBlock & Microwave Digestion
Acid digestion is the most common technique used to decompose samples prior to lab-based elemental analysis. This technique is widely used in combination with different types of digesters, such as HotBlocks, ColdBlocks, and microwaves. Each type of digester has its merits, though microwave digesters are typically faster and can dissolve virtually any matrix. Here is a brief overview of each digester type:
- Hotblock acid digestion uses strong acids (nitric, perchloric, hydrofluoric, etc.) at elevated temperature to break sample materials down in a flask or test tube. In this case conduction heating is used to accelerate chemical decomposition, yet this can prove to be an inefficient and slow process;
- Microwave digesters likewise use strong acids but also rely on microwaves to heat the solution to accelerate the digestion process. The microwave digestion vessels are capped and can therefore operate at higher pressures which allows the reagent sample mixtures to reach higher temperatures culminating in a rapid digestion.
In short both HotBlock and microwave digesters perform digestions by using temperature to increase throughput. This increase in temperature is what shortens digestion times, and the closed vessels of the microwave systems prevents the loss of volatile elements contained in the sample. However, there are limits to the speed of digestion because of the boiling point temperature of the reagents or the maximum pressure that a vessel can handle. These two factors lead to a cap in overall throughput.
ColdBlock™ Digestion: A Revolutionary Digester
At ColdBlock Technologies, it is our mission to offer an unrivalled solution in optimising laboratory efficiency and productivity. We believe we have achieved that in our revolutionary ColdBlock™ digester which introduces the concept of focussed short-wave infrared (FSWIR) radiative heating coupled with active cooling.
Test tubes are inserted into the block where FSWIR lamps excite the sample particles and accelerate digestion. Vapours escaping this heating zone rise to the built-in condenser where condensation occurs and the loss of material from the process is minimised. The combination of heating and cooling results is a fast and precise digestion process.