problem with nitric acid in the sample

[galadriel]

hi everybody,
i think it´s an easy question for you, but i can´t find the right answer. during my bsc-thesis i analysed some solutions with hplc. at first we took nitric acid to get fluoride out of the samples, afterwards we took just water.
now the problem. my bosses told me, that there are problems with my first water samples (including nitric acid). something about a peak below the baseline. but i`m not shure. it this possible, that the acid pushes the peaks below zero? and how this works? maybe you can give me some hints to solve it.
thank you and kind regards,
D.R.

[rhaefe]

http://chromforum.org/viewtopic.php?f=1&t=4621

See point (5) in above link from "the management".
What we need is more information: what system, what separation chemistry, columns and mobile phases used. What is the sample, sample matrix, how was the injection being done (partial, full loop, autosampler or manual etc) and what exactly is the problem?

Thanks.