The special closing plugs for the SDT capillaries play an important role in the patented drop positioning process. The drop is dispensed into the cavity of the plug and, when the plug is closed, introduced into the capillary filled with the heavy phase. This method avoids the conventional, cumbersome dispensing via a septum.
The PTFE plugs are available for two different capillary diameters and two different drop volumes. The choice of drop volume depends on the desired measuring range.
The following closing plugs are available:
| Name | Drop volume | Measuring range (recommended) | For capillary (diameter) |
| SV1631 | 2 µL | < 2 mN/m | SV1601 (3.25 mm) |
| SV1632 | 2 µL | < 2 mN/m | SV1602 (4.6 mm) |
| SV1633 | 4 µL | > 2 mN/m | SV1601 (3.25 mm) |
|
SV1634 |
4 µL | > 2 mN/m | SV1602 (4.6 mm) |
The closing plugs are supplied in sets of 100. One set of 25 SV1633 plugs is included with the measuring instrument.