Passivation of injection needle

[Mattias]

Do you perform passivation of injection needle when you passivate the rest of the LC?

is it possible to inject 30% HNO3, or will it damage the seals?

[rhaefe]

depends on the material of the seal but I would say they can handle 30%nitric acid. I have passivated needles and injectors in the past on following instruments:
HP1090, Agilent 1100, Hitachi/Merck La Chrom. In at least one case I had a stubborn contamination. I removed the injection needle from the system and cleaned it in 69%nitric acid for about 30 minute using an ultrasonic bath. Worked really well.

Make sure that the parts are free from any organic solvent (especially alcohols) and use a separated waste container to catch the nitric acid.

Robert