All detector cells require enough back pressure to prevent eluent in the cell from out-gassing due to abrupt volume changes between the small inner diameter of the connecting tube and the relatively larger volume of the cell; out-gassing creates bubbles in the cell and disrupts detector responsiveness.
For example, carbonate eluent is suppressed to carbonic acid, which is CO2 gas in equilibrium with DI water, and CO2 gas can come out of solution if adequate pressure is not applied. The above outgassing can trap bubbles in the cell causing high noise. Therefore, Thermo Scientific recommends the addition of 30-40 psi of backpressure after the cell for carbonate eluents.
For RFIC hydroxide or MSA applications, it may be possible to operate the cell without backpressure. However, for carbonate and/or bicarbonate applications, it is highly recommended to install backpressure coils.
Back pressure coil components are shipped with your system:
- For 4 mm systems, locate assembly Item # 045877.
- For 2 mm systems, locate assembly Item # 045878 (for 2 mm systems, the backpressure coils are available in the microbore tubing kit, Item # 052324).
See the following table for lengths and diameters of tubing necessary for proper back pressure. Adjust the tubing length to achieve a backpressure of approximately 40 psi.
Suppressor Type | Flow Rate | I.D. of Tubing | Length of Each Coil | Number of Coils (Carbonate) | Number of Coils (KOH/MSA) |
|---|---|---|---|---|---|
4 mm | 0.5–1.5 mL/min | 0.010” (Black) | 2.5 ft. | 2 | 1 |
4 mm | 1.5–3.0 mL/min | 0.010” (Black) | 2.5 ft. | 1 | 0 |
2 mm | 0.12–0.25 mL/min | 0.005” (Red) | 1.0 ft. | 2 | 1 |
2 mm | 0.25–0.75 mL/min | 0.005” (Red) | 1.0 ft. | 1 | 0 |
CAUTION
If back pressure coils become damaged or plugged, they may cause irreversible damage to the suppressor.
Procedure
- Slip PEEK liquid line bolts and ferrules onto the ends of the tubing.
- Determine the correct number of coils required for your application based on the eluent flow rate.
- Assemble the coils, then see the following figure for the proper placement of the completed coils and couplers between the suppressor and the gas separator waste tube.
System with back coils
CAUTION
The correct amount of back pressure for optimum operation is 40 psi for carbonate eluents. Back pressure over 450 psi after the Dionex DRS 600, Dionex ERS 500e or Dionex AERS 500 Carbonate can cause irreversible damage.
NOTE
RFIC hydroxide and MSA applications may be operated with as little as 10 psi of backpressure, or even without any backpressure coils.