A Complete Guide to Ammonia Monitoring

While ammonia is easily identifiable by its distinctive odour, sophisticated instruments are critical to measuring and monitoring concentrations of the nitrogen/hydrogen compound. Without the right calibration methods in place, manufacturing industries risk the quality of finished products as well as the health and safety of employees. Atmospheric ammonia can also have damaging environmental implications, making monitoring an important part of air quality and emissions regulations.

Want to know more about how advanced scientific instruments are used to monitor temporal and spatial patterns in atmospheric ammonia? Below, we explore the different methods and techniques used to monitor ammonia.

Ammonia: 101

Before we dive in, let’s take a moment to define ammonia. Made up of nitrogen and hydrogen, the compound is a colourless gas with a distinct smell that’s often compared to sweat or urine. The molecular formula NH3 is used to denote ammonia, which consists of a single nitrogen atom chemically bonded to three hydrogen atoms.

While ammonia is a naturally occurring compound produced through bacterial processes, it’s also manufactured through human activity. The United States alone produces more than 17 million metric tons of packaged ammonia per year, according to a recent report issued by the United States Geological Survey (USGS). The UK is also an ammonia manufacturing giant, with companies like CF Fertilisers operating plants dedicated exclusively to the compound.

Ammonia applications

Ammonia is one of the most widely used High Production Volume (HPV) industrial chemicals in the country, with around 80% of commercially manufactured ammonia channelled into the agriculture industry and used to make fertilisers.  

In the oil and gas industry, ammonia is used to neutralise the harsh acidic compounds that are often found in crude oil. The mining sector uses “cracked” NH3 to extract copper, nickel and other metals, while coal and oil fired power plants add ammonia to reactors to purify smoke and convert toxic nitrogen oxides into water and nitrogen.

As well as fertilisers, ammonia is used as a refrigerant gas and a component for manufacturing pharmaceuticals, plastics, textiles, dyes, pesticides, explosives and industrial chemicals. Ammonia also supports the chloramine disinfectants used to purify drinking water and prevents the formation of carcinogenic by-products. This makes ammonia a valuable compound for water treatment applications.

The dangers of ammonia

Despite its usefulness across a wide range of industries, ammonia is a highly toxic substance that should be treated with caution. Exposure to low concentrations of ammonia can quickly irritate the eyes, nose and throat. This occurs when ammonia interacts with moisture and mucous surfaces to form ammonium hydroxide, a highly caustic substance that disrupts cell membrane lipids, kills tissues and destroys cells. Water is sucked out as cell proteins break down, which triggers a severe inflammatory response. High concentrations of ammonia can cause serious burns to these areas, as well as irritate the respiratory tract and lungs. Hospitalisation is not uncommon, with extreme cases leading to blindness, lung damage and even death.

Detecting atmospheric ammonia

Thankfully, ammonia is detectable by the nose at concentrations of more than 5 ppm, a relatively low amount that won’t cause serious health issues. When concentrations climb above 300 ppm the consequences can be serious and pose an immediate threat to life. Just a few inhalations can be fatal, with ammonia infiltrating the central nervous system and triggering a dangerous molecular reaction. Ideally, humans should be able to smell ammonia before it increases to a harmful concentration. However, if the gas is not detected in time the results can be dire. This is why ammonia monitoring instruments are so important, with a variety of methods used to monitor NH3 levels.

Choosing the right ammonia monitoring method

Ultimately, choosing the right ammonia monitoring method will depend on a variety of factors. This includes environmental conditions, safety concerns, budget and the limitations of certain sensors. The new automated systems outlined below have set a new standard for ammonia detection, offering real-time data and lighting fast response times. 

• Chemiluminescence

Chemiluminescence analysers employ light-based technology to detect and measure ammonia. A thermally stabilised photodiode is used to measure the intensity of light produced during a chemical reaction. Data is used to measure ammonia concentrations and monitor air quality. Chemiluminescence instruments are commonly used to monitor atmospheric air quality and ensure ammonia levels don’t creep dangerously high. Models like the 17i Ammonia Analyser from Thermo Fisher Scientific set a new standard for precision and accuracy.

• Photo Acoustic Spectroscopy (PAS)

Photoacoustic spectroscopy (PAS) analysers use electromagnetic radiation absorption levels to detect trace levels of ammonia. The instruments combine technologies used in both ultrasonic tomography and optical spectroscopy, with acoustic pressure waves used to detect ammonia in both industrial and environmental applications.

The Chillgard 5000 Refrigerant Leak Monitor from US-based company MSA Safety is a best-in-class PAS ammonia monitoring solution. It uses photoacoustic spectroscopy to detect early refrigerant gas leaks in industrial plants and equipment rooms, with the capacity to measure concentrations as low as 10 ppm. PAS instruments are easy to maintain and favoured for their lower cost of ownership.

• Fourier Transform Infrared Spectroscopy (FTIR)

FTIR analysers use wavelength range variations in the infrared region to detect trace levels of ammonia. An interferometer is used to measure how much infrared light a sample absorbs, then uses this data to determine how much ammonia is present. Fourier Transform Infrared Spectroscopy is an effective way to measure raw ammonia emissions in engine exhaust.

• Tuneable Diode Laser Absorption (TDLA)

Tuneable diode laser absorption is an accurate and reliable method for detecting and measuring ammonia concentrations. A wavelength of near-infrared (NIR) light is emitted by a tuneable diode laser and directed into a sample cell. After passing through the gas the NIR is bounced back by a mirror to a solid state detector.

Fast, accurate and low maintenance, TDLAs have made it easier than ever to detect ammonia. As well as NH3, tuneable diode laser absorption technology is also used to detect oxygen, hydrogen chloride, carbon monoxide, methane and other compounds. 

• Dry Colorimetric Method

The development of the Dry Colorimetric Method revolutionised ammonia detection. It offered the scope to monitor ammonia to levels as low as 32ppb and slashed analysis times to just seconds. Detectors are purpose-built to detect impurities in samples, with an impinger used to collect gas and convert it into liquid form. Chemical reagents are then added to the liquid and trigger a colour change based on the concentrations of ammonia present. Results are reliable and proof-positive, making the Dry Colorimetric Method a popular choice across a wide range of industries. Common applications for the Dry Colorimetric Method include the detection of ammonia in drinking water and dairy products.

• Electrochemical (EC)

Simple and affordable, Electrochemical (EC) sensors are a reliable ammonia monitoring solution. The sensors detect NH3 by producing a chemical reaction between ammonia concentrations and oxygen stored in the instrument. The reaction creates a low-voltage current, with intensity used to measure ammonia concentrations. EC sensors can be used to detect a variety of chemicals, though voltage, electrode material and electrolytes will vary depending on the compound being monitored.

• Active Diffusion Denuder

In the United Kingdom, the Active Diffusion Denuder method is used to map spatial and temporal ammonia emissions across the country. The UKEAP: National Ammonia Monitoring Network champions the CEH DELTA system at more than 80 sites across the country, with monthly measurements used to track agricultural emissions and adhere to international regulations.

• Adapted Low-Cost Passive High-Absorption (ALPHA)

As well as the CEH DELTA system, UKEAP: National Ammonia Monitoring Network employs the use of ALPHA at dozens of sites. Adapted Low-cost Passive High-Absorption is used to assess NH3 concentrations in the air, with results calibrated against CEH DELTA data to increase reliability.

• Portable Gas Detection

While most high-performance ammonia detection instruments are permanent additions, portable gas detectors offer the scope to measure hazardous gas concentrations anywhere, anytime. Personal gas detection devices like the Dräger Pac® 8000 are common in industrial applications like mining and manufacturing, where exposure to toxic gases makes personal air monitoring a valuable health and safety tool. Most portable gas detection instruments are built to withstand the tough conditions of these environments, with chemical-resistant housing, shock-proof features and built-in membrane filters to protect against dust and liquids,

• Laser-Based Analysers

Purpose built for precision and accuracy, laser-based analysers have the capacity to detect trace gases at extremely low ppm and ppb levels. The sophisticated analytical instruments are highly sensitive and selective, making them ideal for ammonia detection in laboratories and manufacturing plants, as well as emissions monitoring applications. In just a few seconds, advanced laser technology from CI Analytics can detect and measure ammonia levels as low as LDL 6ppb vol.

Want to know more about these next-generation instruments? Commentating on behalf of CI Analytics, L. Lorena Torres and Babacar Diop explore the use of laser analysers to detect ultralow levels of ammonia in ‘New perspectives in ammonia monitoring.’