Automated sample preparation zone - 7.2 Dispenser



The instrument is fitted with a picolitre piezo-electric dispenser that is used to dispense the sample onto the grid.


general warning

The dispenser tip is sharp and delicate, take care during manual intervention to avoid physical injury.


The dispenser requires a constant fluidic pressure head in order to operate and this is provided by connecting the dispenser to a height-adjustable reservoir containing high purity water (HPLC grade).

IMPORTANT: The dispenser outlet is approximately 40μm min diameter and can become blocked without proper care. Take care to ensure that dirt, dust and debris of any kind are not introduced to the dispenser fluid reservoir.

7.2.1 - Dispenser fluid degassing

If there are air bubbles in the dispenser or connecting tubing, dispense performance can be adversely affected. To minimize the risk of bubble formation, the dispenser fluid must be degassed before the instrument is used. chameleon is fitted with an online degassing system that operates by sparging helium through the fluid in the reservoir.  

If you cannot make a helium supply available, offline degassing can be carried out using a vacuum pump and sonicator. Contact reliance for additional information if you want to use this option.  

IMPORTANT: You must follow protocols for carrying out offline degassing. Particular attention is drawn to the cleanliness required for the successful operation of the dispenser head. Additionally, take care not to re-aerate the water when pouring it between vessels.

7.2.2 - Dispenser working height fluid adjustment

The hydro-dynamic pressure head is critical to the operation of the dispenser head. This is automatically set by the instrument.  

Fill the 250mL bottle so that the level is within the vertical line provided on the side and place it into the bottle rest. The stage then moves the bottle to a position where the fluid level is determined by means of a camera. The system then positions the bottle to the required height.

working fluid assembly

Next Article - Automated sample preparation zone - 7.3 Grid Handling