The history of the flame photometer – from invention to modern-day use
It has been nearly 150 years since Paul Champion, Henri Pellet and Charles Grenier developed a method of analysing the concentration of sodium in plant ash.
Today, flame photometry is used around the world every day in a range of industries.
However, during the 19th century, the methods for the chemical analysis of concentration were limited.
One of the standard methods at the time would have been titration.
Titrating metal ions poses difficulties though, which cannot be overcome in some cases, including with sodium.
How did Champion, Pellet and Grenier overcome these difficulties?
In 1873, the trio developed a method by having two ethanol lamps parallel to each other.
Next, they introduced a sample of sodium plant ash dissolved in water and nitric acid, after being filtered into one lamp.
Then, with the second lamp, a series of calibration standards were produced by dissolving solid sodium into water and the flames compared.
What are the problems with this method?
Using this method, there is no way to accurately collect the intensity of the light emitted, apart from using the naked eye to make a comparison.
As noted in further work by Gouy in 1877, there was no realisation the quantity of sample introduced to the flame had a large influence in the same manor the concentration had.
Finding a solution to the problem
Just four years later, Gouy designed a pneumatic atomiser to introduce a set quantity of sample and standard into the flames at the same time.
Upon removing the vital flaw from the method, the very first instrument for the quantitative analysis of sodium in water samples had been developed.
Gouy also developed a starting mathematical analysis of how the intensity of the radiation given off from a flame is directly proportional to the size and concentration of the sample.
How accurate was Gouy’s method?
The final accuracy and precision of Gouy’s method, after the sample size addition was brought from two to five per cent in the first method, was consistently less than two per cent margins.
However, as it was still being done by eye, the method was very tedious due to having to remake a lot of standards every time.
This was also the best way to increase the accuracy of the method.
How has that method changed?
Fast-forward to today, and it’s interesting to note that a lot of the early developments in chemical analysis were mainly done with at least some footing in biology.
Early pioneers would have measured plant ash in photometry, or colorimetry which was designed by a biologist to analyse coloured chemicals present in flowers.
This invention is still being developed further, and here at BWB Technologies we are still pushing the boundaries almost 150 years later.