Seawater, brine, strongly sweetened fresh drinks: whenever you encounter concentrated samples there is the risk of the separating column becoming overloaded and adversely affecting the quality of the analysis. Previously such solutions had to be diluted, either manually, inline or with a special dilution sample changer. Now there is a new solution: the internal loop!
In ion chromatography 10, 20 or 100 µL of the sample is injected as standard; in contrast, the internal loop only injects either 1.0 or 0.25 µL. For example, if the 0.25 µL loop is used then the injected volume is smaller than that injected with the standard 20 µL loop by the factor 80. This means that samples in the g/L concentration range can be injected undiluted.
The internal loop or the so-called rotor can be ordered individually with sample volumes of 0.25 or 1.0 µL. In order to be able to use it, the rotor built into the standard six-way injection valve is simply exchanged, the six-way stator remains unchanged. As only four openings of the six-way stator are required for working with the internal loop, this means that two of its openings must be sealed. This is why a version with a special four-way stator is also available. In this case the rotor (0.25 µL) and stator (4-way) of the standard valve must be exchanged. The valve drive always remains unchanged.