What is the size of the capillary?

The standard Fida capillary has an inner diameter of 75 µm and a length of 100 cm, with 84 cm of that length sitting before the detector. Capillaries of other lengths and diameters can be supplied on request.

Why do the capillary dimensions matter?

They set the conditions the measurement runs under. The inner diameter, the total length and the length to the detector all go into Taylor's dispersion law alongside the running pressure, the temperature and the viscosity of the sample, and it is that calculation that turns the width of the measured peak into a diffusion coefficient and then into a hydrodynamic radius. A standard run uses 750 mbar at 25 °C, and the software's experimental evaluation tool takes these values and tells you whether the conditions are valid for the size you expect to measure.

Does a thinner capillary use less sample?

Yes. A measurement on the standard capillary consumes about 8 µL from a minimum of 10 µL loaded, and a thinner capillary reduces that further. The injected plug itself is only 40 nL; the rest is what it takes to load and flush the line.

Is there more than one type of capillary?

There is. Capillaries come uncoated and permanently coated, and the two can be exchanged freely between assays, with dynamic coating also possible on an uncoated capillary. A separate kinetics capillary is available for interactions too fast to resolve on the standard one, because it mixes faster. The capillary types page covers the coating options, and consumables are ordered through shop.fidabio.com.

Frequently asked questions

What is the inner diameter of a Fida capillary?

75 µm on the standard capillary. Other diameters are available on request.

How long is the capillary?

100 cm in total, with 84 cm to the detector, on the standard capillary.

Can I get a capillary in a different size?

Yes. Other lengths and diameters are supplied on request. Ask through shop.fidabio.com or your regional representative.