Baseline Correction: What is the concept of a baseline shift and baseline correction? I have a laser induced fluorescence signal data-set. Currently the processing pipeline performs baseline correction by manually moving the signal so that the initial point is at the origin. Is this a right approach?

Is it to be done only if the shift is predetermined or known?
Does that mean baseline error signal has zero frequency?
Or can there be low frequency components which can be called baseline errors?

Edit:
Laser Induced Fluorescence signal is used to get relative quantities of collagen, NADH etc from the tissues. 

Raw signal:



I am from neither signal processing nor physics background. The requirement I have been given is to develop a software for analysing the preprocessed data. However, I observed that currently the preprocessing uses the above said manual method for baseline correction.
Baselines are visually simple, most of the time, but can be a pain to filter.
With your graph, for instance, what should happen between 380 and 400 is not clear.

With fluorescence, it is not sure you can get a fine model of the baseline. So effectively, in many analytical instruments, there are more or less automatic baseline fits: constant, linear, parabolic. 

Without hard models, it is common to use soft ones, but we need to know what you want to quantify in your data. If it looks like other analytical chemistry data, where you want to measure peaks above a baseline, you may try the technique given in Chromatography Baseline Placement, combining low-pass filtering and peak preservation.

Is there any chance you could share the dataset?