low RNA A260/280 - (Oct/29/2013 )

I use spectrophotometer to quantify my RNA as well as looking into the purity,

I got a concentration in the range of 40 to 50 ng/ microL. however, my A260/280 were low, in the range of 1.3 to 1.5. 

Would the low RNA concentration leads to a low A260/A280 reading? 

No. On a A260/280, pure RNA is close to 2.0 while pure DNA is close to 1.8. Your reading indicates the presence of a contaminant. Probably protein, salt or a buffer left over from your RNA purification.

Depending on the downstream application of your RNA, you should consider doing an isopropanol purification.

Edit - Depending on how you spec your sample, (nanodrop, cuvette, etc.) make sure that the utensil is clean. I have been in labs that dishwash cuvettes. Soap scum on the cuvette will interfere with your reading.

Also note that the 260:280 ratio is dependent on what you dissolved your sample in, different buffers will give different readings for "purity".