Basic Information

Abstract Number: 1260-10     Author Name: Scott Tucker Affiliation: Hach Company Session Title: Chemical Methods Event Type: Poster Event Title: Determination of Ammonia by Flow Injection Analysis Utilizing In-Line Distillation Presider(s):   Start Time: ( Slot # 10 ) Date: Tuesday, March 10th, 2009 Location: Keywords: Automation, Environmental Analysis, Flow Injection Analysis, Sample Preparation

Abstract Content

Summary of In-line Distillation of Ammonia by Flow Injection Analysis The sample is distilled in-line by mixing the sample with a borate buffer, adjusting the sample pH to 9.5 decreasing the hydrolysis of cyanates and organic nitrogen compounds. The sample is heated to 120°C by traveling across 850 cm of 0.04 mm diameter Tefzel tubing. The sample is then distilled across a hydrophobic semipermeable membrane into a stream of dilute sulfuric acid. The distilled ammonia sample is then heated with salicylate and hypochlorite in an alkaline phosphate buffer to produce an emerald green color, which is proportional to the ammonia concentration. The color is intensified by the addition of sodium nitroprusside. The in-line distillation is beneficial for laboratories because it eliminates time and extra money. The complete analysis for one with the in-line distillation and the colorimetric determination is 3 minutes. Using the in-line distillation will also greatly decrease laboratory costs with the elimination of the distillation apparatus and its accompanying glassware or other consumables. The applicable range is 0.25 to 20 mg N/L as NH3. The statistically calculated method detection limit is 0.018 mg N/L as NH3. The precision of a mid range calibration standard of 10 mg N/L as NH3 resulted in a %RSD of 0.88%. This method can be used for acid preserved and non acid preserved samples by switching the concentration of the borate distillation buffer.