New batch of flow-through capillary holders: interested?

2025-09-09 Brian Pauw Blog posts 0

For the last years, we’ve been enjoying our PEEK capillary holders. These are vacuum-tight holders with two HPLC fittings (1/4″ – 28 UNF threads) to allow us to easily measure in flow-through. If a capillary gets irreparably fouled, we can dissolve the old glue by immersion overnight in a DMF bath and some scraping, after which we can put a new capillary in (there’s a YouTube video on that process here). Glen and I now thought it would be time to make an improved iteration of this holder…

The new version is considerably smaller so you can stack more in a rack or flow-through capillary ladder, and has significantly more mounting options. These include:

  1. two bottom blind M4 holes at 25mm distance for optical post mounts, and
  2. three counter-sunk M3 holes in the front for mounting to a plate at the back (in the current design (Figure 3) these are spaced further apart than those shown in the photos for better alignment reproducibility).
  3. There are two threaded M3 holes on the front for mounting accessories such as, perhaps, small capillary heater shrouds.
  4. Lastly, three divots are included on the bottom for drilling out in case you want to mount using a different method, or if you want to glue a fiber in place for e.g. simultaneous UV-VIS spectroscopy. Check the design for the detailed locations.

Best of all, these are machined on a CNC by our wonderful workshop staff, who indicated they can easily make many more of these (e.g. making a batch of 50 or 100 would take a bit of time but is not hard). While we don’t need this many ourselves, we can make them available as standardised flow-through cells at production cost if there are interested people out there.

Figure 1: Three early prototypes, one of which has the 1.2 mm O.D. capillary through it. Note that the hole patterns on the current design is different.

We could supply some batches with a mounted capillary at additional cost, but we are not in the business of reselling (or indeed gluing) the recommended extruded Hilgenberg capillaries. We’re also looking into alternative glues to use, perhaps some UV-curable glue would look nicer and can be applied more easily than the current Araldite 2014 epoxy.

Figure 2: All glued up and ready to go with a 1.2 mm O.D. capillary.

So, do let us know (e.g. via the community telegraph or by sending me an email) if there’s any interest in obtaining these, and how many you would like, and then we can use that information to decide how large a batch to manufacture.

Figure 3: Screenshot of the current design. This may still be changed slightly if needed. The final design will be made available on Zenodo under a CC-BY or CC-BY-SA license.