Flame Photometry & Water Analysis
How Hazardous is our Environment?
Sodium and potassium salts occur everywhere on Earth. In most locales they are sufficiently dispersed that they present no health hazard. They are also present in the majority of water supplies, either natural or managed. The use of pesticides, potassium permanganate (WHO List of Essential Medicines), and water softeners has impacted the Water Quality Index (WQI) in many areas. Runoffs from farming, industrial processes, and household uses artificially increase the levels. Other factors such as people flushing unneeded or expired prescriptions down the toilet instead of taking them back to the pharmacy for proper disposal can also influence the water system. For example, this probably accounts for much of the increase in lithium levels in urban water supplies.
Humans in most settled areas treat water before use in a municipal system. This 1938 photo shows the future Bronx section of a New York water main (upper), and sewer lines (lower), during construction. These ducts are still in use today providing millions of litres of potable water to millions of people, every day, and then shunting away the grey or black water to treatment plants for reintroduction to the environment.
Since sodium and potassium occur in most water supplies, any chemical treatment process is likely to increase the ratio of sodium and potassium in relation to the dissolved solids in the water. Indeed, most water treatment uses potassium permanganate as a powerful oxidant (which has no toxic by-products) to precipitate excess iron and remove the “rotten eggs” smell of hydrogen sulphide. Contemporary practices, such as using boiler feed water prior to treatment, results in the concentration of practically all soluble constituents of the boiler water into both sodium and potassium salts. This can have a major impact on the WQI.
Flame Photometry to the Rescue!
The determination of alkali metal concentrations in water supplies for a number of industrial processes is useful, too. Companies like those big names producing fizzy cola are so intent of guaranteeing the precision and consistency of their flavours that even using municipal water in the bottling plants is deemed inadequate.
They filter the water through multiple massive sand filters before it even gets near their formulating process. Water for major brands of soda pop is so pure that it is completely tasteless, essentially nothing but H 2 + O. That is why travellers concerned with water quality at a foreign destination are advised to only drink major brands of soda pop (with no ice).
Water Quality Monitoring is also used in fields like aquaculture to make sure fish are growing well, and not accumulating toxins, so they can be safely released in depleted ponds, lakes, streams, and rivers. This is just as important in systems responsible for raising fish for direct human consumption.
Obviously we should also be careful about dumping toxins in the environment, or in water bodies such as rivers and ponds. We should curtail synthetic inputs into our planet’s food chain and improve the management of waste treatment to leave a liveable world to sustain future generations.
For industrial water monitoring, compound flame photometers have been developed, capable of giving simultaneous readings of multiple metals dissolved in water including the usual selection from Group I and II alkali/earth metals (Barium, Calcium, Lithium, Potassium and Sodium), plus, in some cases, more unusual elements like Caesium, Rubidium, and Strontium under specific controlled conditions.
Even the quantity of Lead in petrol/gasoline, or Calcium, Magnesium, Sodium, Potassium, and Iron oxides levels in Portland Cement can be determined. While not typical, it is useful to know that such testing is possible.
1949 was the year that flame photometry became the de facto standard for measuring Sodium and Potassium in aqueous solutions. Less than a decade later, in 1958, the Michigan Department of Highways was investigating how to accurately determine iron
concentrations (et al) in 17 samples of Portland Cement with flame photometry. The conventional methods were time consuming, expensive, complex, and subject to error. By doping standard solutions with known quantities of iron (and these other substances—see chart) in order to compensate for the interference in the flame, their results were consistent with the known formulations, expanding the range of things that could be successfully tested with flame photometry.
The field of analysis has grown since, of course, and new techniques are available for stunningly accurate determination of substances that are outside the range of FP’s capabilities. This has decreased the use of FP for these unusual investigations.
Nevertheless, the speed, efficiency, remarkably low operational costs, and the practicality of FP has kept it in the forefront of speedy assays for biochemistry, healthcare, water hardness assays, the food industry, soil science for farming, and much more.
Healthcare, for example, uses it for urinalysis, blood analysis, serum analysis, and more because a common medicine, Lithium Carbonate, is used to treat bipolar disorder, but if there is too much in the body, it can cause renal failures, Central Nervous System failures, and even trigger or exacerbate diabetes.
The food industry monitors salt levels in food much more intently nowadays because of health implications. Sugar is problematic, too, but since sugar is a hydrocarbon (C 12 H 22 O 11 ) composed of Carbon, Hydrogen, and Oxygen, none of which produce a colour change in an FP device, s a result, alternative methods have been developed as standard practice. The industry uses a known potassium standard solution mixed with the sample suspected to contain sugar, and if the potassium level rises, they know sugar is present. Although the method is an indirect test, it does accurately identify the presence of sugar in the solution in a qualitative way, but only hinting at a quantitative result. It’s best used when you need a simple yes/no answer.
As you can see, Flame Photometric Analysis still has a valuable place in many forms of analytical chemistry. The sheer economy, speed, and shallow learning curve will assure its future use for many more years.
Whether handled by a technician processing variegated samples, or whether the whole process is completely automated, continuous, and managed by Artificial Intelligence, Flame Photometry is not going away anytime soon.
If you need Flame Photometer equipment, we’ll be here for you, happy to answer any questions you may have!