You can not run samples until your system has been fully equilibrated and stable. Please do not inject samples at this time. You must first address and solve the problem. Additionally, when asking chromatography questions, it helps all of us if you can include your actual chromatography conditions (e.g. make/model of HPLC, column dimensions and type, flow rate, exact mobile phase composition, detailed detector settings, injection volume, injection solution, sample concentration, Retention time...) in your initial post. These are critical to troubleshooting any problem(s).

The chromatogram you attached shows a wavelength of 280 nm (4) and pure noise, nothing else [signal noise at 280 nm averaging 50 to 100 mAU ! This is not an auto-scaling problem. Just look at the real time signal she provided ]. If you are really running a mobile phase of 100% pure ACN, as suggested, than you should be able to obtain a beautiful flat baseline (~0.5mAU) at 280nm with no trouble at all. There are hundreds of reasons why your baseline would show only noise (too many to list here) and to troubleshoot this issue you really need to get some local help from an experienced chromatographer. The most likely cause is a training issue. The true causes are most likely something very fundamental such as not degassing the mobile phase, a sticking check valve, air in the system, a leak and so on.

Perhaps this linked article will assist you in troubleshooting the problem? "Common Causes of Baseline Noise in HPLC, UHPLC"

http://hplctips.blogspot.com/2014/09/common-causes-of-baseline-noise.html

Signal is very low, and there is an autoscaled graph. why do you think that is wrong. is very stable. try with vit and you will see that the autoscalation show you a good peak 

Agreed with the above comment.  In addition what is your wavelength?  The UV cutoff for Acetonitrile is about 205 nm.  What is your detector? 

I see 280 nm detection. Is the lamp warmed up? No air in the system? Column not shedding particles?

Do you have an earlier chromatogram for comparison, or another similar system known to be working properly?

Just increase the Vitamin C concentration. Your S/N will improve.

Also ensure that there is no problem with UV lamp and the detection system.

You can not run samples until your system has been fully equilibrated and stable. Please do not inject samples at this time. You must first address and solve the problem. Additionally, when asking chromatography questions, it helps all of us if you can include your actual chromatography conditions (e.g. make/model of HPLC, column dimensions and type, flow rate, exact mobile phase composition, detailed detector settings, injection volume, injection solution, sample concentration, Retention time...) in your initial post. These are critical to troubleshooting any problem(s).

The chromatogram you attached shows a wavelength of 280 nm (4) and pure noise, nothing else [signal noise at 280 nm averaging 50 to 100 mAU ! This is not an auto-scaling problem. Just look at the real time signal she provided ]. If you are really running a mobile phase of 100% pure ACN, as suggested, than you should be able to obtain a beautiful flat baseline (~0.5mAU) at 280nm with no trouble at all. There are hundreds of reasons why your baseline would show only noise (too many to list here) and to troubleshoot this issue you really need to get some local help from an experienced chromatographer. The most likely cause is a training issue. The true causes are most likely something very fundamental such as not degassing the mobile phase, a sticking check valve, air in the system, a leak and so on.

Perhaps this linked article will assist you in troubleshooting the problem? "Common Causes of Baseline Noise in HPLC, UHPLC"

http://hplctips.blogspot.com/2014/09/common-causes-of-baseline-noise.html