Intro
This method is used for the determination of ammonia nitrogen in drinking water, ground water, surface water, and domestic and industrial wastes according to USEPA Method 350.1 and Standard Methods 4500–NH3 H.
Prior to analysis, ammonia is buffered to pH 9.5 and distilled into a solution of boric acid.
Cyanate, which may be encountered in certain industrial effluents, hydrolyzes to some extent, even at the pH of 9.5 at which distillation is carried out.

#Distillation - adding excess base to the acid digestion mixture to convert NH4+ to NH3, followed by boiling and condensation of the NH3 gas in a receiving solution.
#Titration - to quantify the amount of ammonia in the receiving solution.
#The amount of nitrogen in a sample can be calculated from the quantified amount of ammonia ions in the receiving solution.

The DistillationProcess
The acid digestion mixture is diluted and made strongly alkaline with NaOH, liberating NH3 as follows: (NH4)2SO4 + 2NaOH ➝ 2NH3↑ + Na2SO4 + 2H2O Ammonium sulphate heat gas ammonia The Kjeldahl flask is attached to a water condenser and is heated to boil off the NH3 gas from the digest. The tip of the condenser is submerged in a flask of acidic receiving solution, either standard acid or boric acid solution, to again trap the distilled NH3 in receiving solution. NaOH Addition Concentrated NaOH (usually 50% solution) is added slowly down the neck of the flask. Being heavier, it forms a layer underneath the diluted acid digestion mixture. Generally, for each 5 ml of concentrated sulfuric acid used in the digestion, 20 ml of 50% sodium hydroxide is required to make the digest strongly alkaline (pH of >11). The flask is connected to the condenser and mixed before heating and distillation begins. For samples not requiring a digestion step, such as direct ammonia determinations in water, the sample is buffered to a pH of 9.5 with a solution of sodium tetraborate and sodium hydroxide, to decrease hydrolysis of any complex organic nitrogen compounds present. Distillation The majority of the NH3 is distilled and trapped in the receiving acid solution within the first 5 or 10 minutes of boiling. But depending on the volume of the digestion mixture and the method being followed, 15 to 150 ml of condensate should be collected in the receiving flask to ensure complete recovery of nitrogen. Further extension of the distillation times and volumes collected simply results in more water being carried over to the receiving solution. Excess water does not change the titration results. Receiving solutions By using boric acid, the titration directly measures the amount of ammonia in the distillate by neutralizing the 1:1 complex formed by ammonia and boric acid. Large quantities of boric acid may be added to the receiving solution so complete absorption of the ammonia is assured. Receiving solution volumes may be increased by the addition of ammonia-free water so that the tip of the delivery tube is immersed. Delivery tubes should always be allowed to drain momentarily into the receiving flask before removal from the distillation apparatus. The receiving solution should remain below 45° C during distillation to prevent loss of ammonia. Titration process If boric acid is used as the receiving solution instead of a standardized mineral acid, the chemical reaction is: The boric acid captures the ammonia gas, forming an ammonium-borate complex. As the ammonia collects, the color of the receiving solution changes. The addition of sulfuric acid exactly neutralizes the ammonium borate complex, and a reverse color change is produced. The boric acid method has two advantages: only one standard solution is necessary for the determination and the solution has a long shelf life. Indicator Solutions Many different indicators have been used to provide a “sharp end point” color change. The analyst’s use of specific types of indicators can be a personal choice. The combination of methyl red and methylene blue indicators is frequently used in many methods. The color change of the indicator must fall within the equivalent point of the reaction. For standard acid/base titrations, methyl orange is usually the preferred indicator. If color change end points are difficult to detect, reference solutions made from a blank with an indicator can be very helpful.

Ammonia Nitrogen - Tim Loftus Nitrogen is an essential ingredient in the formation of proteins for cell growth. From complex organisms like animals to the simple bacteria used to treat wastes in an activated sludge treatment facility, every living thing needs some form of nitrogen to survive. But too much nitrogen freely available in the environment can be a bad thing. Excess nitrogen discharged into our waterways can contribute to eutrophication, the gradual change of water bodies into marshes, meadows, then forests. It can also contribute to massive algae blooms leading to oxygen depletion in water and its associated problems. Certain forms of nitrogen can cause specific problems too. Ammonia is toxic to fish, and nitrates at high enough dosages in the drinking water cause methemoglobinemia in infants (Nitrates convert to nitrites in the stomach. These nitrites then interfere with the oxygen-carrying capacity of the hemoglobin in blood). Prior to ammonia analysis a sample must first be distilled to remove anything that may interfere with the test method. The sample’s pH is adjusted to pH 9.5 using a borate buffer. This solution is then distilled into a receiving solution of either boric acid (for the nesslerization and titration test methods). In the titration procedure, a color indicator is added to a sample. This sample is titrated using 0.02N sulfuric acid until the indicator turns to a pale lavender color. The amount of acid used to the color change is proportional to the ammonia present.