right now our lab have systronics pc based double beam spectroscopy

Dear Sir. Concerning your issue about the soil dilution procedure for nitrogen analysis by uv vis spectrophotometer. Shirato et al. (1989) described different FIA systems with UV/Vis spectrophotometric detection for determination of N in several forms. For the determination of NO2, 40 uL of N-(l-naphthyl) ethylenediamine reagent was injected into a water carrier solution on either end of the sample solution by using a 16-port valve. This stream then passed along a reaction coil towards the detector and absorbance was measured at 520 nm. Nitrate was determined similarly after reduction to NO2 on a 30-cm Cu-Cd-glass column. For NH4 determination, NH3 was liberated by 200 uL of a 1M NaOH solution injected in both sides of the sample solution, separated with a dialysis membrane and determined by the indophenol method in the acceptor stream. Absorbance was measured at 630 nm. These systems allowed the determination of NO2, NO3, and NH4 in the range of 0.1 to 7 mg I/1 , 1 to 20 mg I/1 , and 1 to 150 mg L1 , respectively. I think the following below link and the attached file may help you in your analysis:

http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.454.173&rep=rep1&type=pdf

Thanks

@ Isam Eldin Hussein Elgailani : Thank you sir