HPLC Products

Autosampler Problems - Needle depth

too high or too low

It is necessary that the needle depth should be adjustable to accommodate different types of vials. So care must be taken when using a new type of vial to establish an appropriate needle depth.

If the needle depth is set too high, the last part of the sample cannot be drawn up and the needle may draw in air.

If the needle depth is set too low, it drives a hole through the bottom of the vials.

Establishing the appropriate needle depth is usually done using the autosampler in service mode, and driving the needle down one step at a time until the vial moves, indicating that the needle has made contact with the bottom. The depth actually used should be several steps higher than this to allow for variations in the vial base thickness.

Care should be taken with needle depth when changing from one type of vial to another, or when using low-volume inserts into standard vials.