Flame Photometry – Analysis of Alkali and Alkaline Earth Metals
With testing costs of only about 1 cent per analysis, flame photometry (AES) is currently the most cost‑effective method for determining alkali and alkaline earth metals. Modern flame photometers are increasingly replacing expensive and time-consuming elemental analysis techniques such as AAS, ICP-OES, conventional titrations, and measurements using ion-selective electrodes.
Thanks to technical advancements and improved safety concepts, the KRÜSS Optronic FP8000 Series opens up new applications for cost-conscious users—from automated incoming goods inspection to the qualification of FFP masks in accordance with DIN 149.
AES relative measurement reliably detects very low concentrations: the presentation of results in precise units such as ppm and ppb is a key advantage for analytical accuracy and informed decision-making.
Contents
parts per billion
ppb is a dimensionless unit of concentration and the abbreviation for “parts per billion.” It is used, for example, in residue analysis and indicates how many units of weight or volume of one substance are contained in one billion units of another substance. Example: To produce microchips, the semiconductor industry requires silicon that contains less than 1 ppb of contamination atoms—that is, silicon that is more than 99.9999999% pure.
Atomic emission spectrometry
Atomic emission spectrometry (AES) is an analytical method used primarily to determine the concentration of alkali and alkaline earth metals in aqueous solutions in a cost-effective, precise, and rapid manner. It is a relative measurement in which the unknown concentration of a sample is determined by comparison with a concentration known as a standard.
parts per million
The concentration ppm is the abbreviation for “parts per million” and means parts per million. A value of 10 ppm therefore means that, for example, there are 10 milligrams of one substance in one kilogram of another substance. As water at room temperature has a density of approximately 1 L per kilogram, ppm is often equated with mg/L in analysis. Example: Mineral water may only be labelled as “low in sodium” if the sodium content of the water is below 20 ppm.
How does a flame photometer work?
What is being measured?
We are familiar with the principle of flame photometry from the chemistry lab: When potassium or other alkali metals are introduced into a very hot flame, a flame color characteristic of the respective element appears. In AES laboratory measurement, the analysis substance is sucked in as an aqueous solution at the push of a button and atomised using compressed air as a carrier gas (aerosol). After that, it is sprayed into a dimly lit flame. The thermal excitation of the flame causes the atoms to glow – each with its own characteristic wavelength.
Principles of elemental analysis of Na, K, Ca, and Li
The emitted radiation is selected by a suitable optical filter for each element, so that only the light of one wavelength reaches the corresponding photodetector. Several detectors are used simultaneously as standard, allowing the simultaneous determination of several elements.
The higher the concentration of an element, the more intense the emitted light is. The concentration of the measurement solution is determined via the luminance. Modern flame photometers automatically calculate the necessary curve adjustments, which compensate for non-linear effects and enable high quantitative precision.
Measurement process and safety features
Atomic emission spectrometry (AES) provides a concentration result with accuracy of eight decimal places in just 30 seconds, while meeting all relevant industry standards. With a sample throughput of up to 120 measurements per hour and the capability for fully automated 24-hour operation, the FP8000 series offers highly efficient technology. Here is a detailed look at the flame photometer setup and its complex measurement process.
Optimal mixture, accuracy in measurement
A perfectly matching mixture of sample, gas, and air ensures the highest precision. The analytical solution is automatically diluted and finely atomized using the Venturi effect. Drops that are too large are separated in the Nebulizer Chamber and monitored by a droplet sensor. This ensures that the sample flow and nebulizer are optimally controlled during the measurement.
Controlled flame for consistent results
The finely atomized sample is combined with propane or acetylene in the gas mixing chamber to form an ideal mixture of sample, gas, and air. For maximum stability, a system of 12 gas outlets creates a perfectly defined flame. Precise airflows and a protective glass cylinder ensure a steady flame—the foundation for consistently reliable measurements.
Analysis with precision photosensors
Elements such as sodium, potassium, calcium, and lithium emit light at characteristic wavelengths when thermally excited. The high-precision photosensors detect these signals and enable the simultaneous measurement of up to five elements. Alternatively, it is also possible to reliably determine different concentration ranges for a single element.
Safety thanks to efficient cooling and monitoring
An integrated cooling airflow lowers the exhaust air temperature to below 50°C, thereby increasing user safety. At the same time, the device continuously monitors the flame and automatically closes the safety valves if any abnormalities are detected. With up to 120 measurements per hour and fully automated 24/7 operation, the system delivers highly precise, eight-digit measurement results that meet industry standards in just 30 seconds.
Flame photometers provide highly accurate and cost-effective measurements. A comparison of different measurement methods illustrates just how significant this gain in efficiency is.
Flame Photometry – Comparison with other measurement methods
KRÜSS Optronic flame photometers are very cost-effective: Operating costs per measurement are in the single-digit cent range. This is due to the low consumption of standard gases and Combustion gases, as well as the low-wear, straightforward measurement mode.
- In comparison, alternative absorption methods such as AAS (atomic absorption spectroscopy) incur significantly higher costs—replacing a hollow-cathode lamp for a single element alone can cost several hundred euros.
- Combustion gases used in the AES measurement method, such as propane or acetylene, are cost-effective and easy to handle. Another advantage of the FP8000 series: Applications can prepare calibration solutions not only from commercial standards but also from inexpensive salts.
- In addition, flame photometers eliminate the need for the costly disposal of hazardous reagents and reaction products, which is often required in other analytical methods.
| Flame photometer |
AAS (Alternative method) |
ICP-OES (Alternative method) | Electrodes (Alternative method) | Mass Spectrometer (Alternative method) | |
|---|---|---|---|---|---|
| Measurable elements | Alkali and alkaline earth metal | MANY | MANY | One element per electrode | ALL |
| Accuracy | HIGH | MEDIUM | MEDIUM | MEDIUM | VERY HIGH |
| Detection limits | ppb to ppm | ppb to ppm | ppb to ppm | ppb to ppm | ppt and below |
| Cost per measurement | LOW | MEDIUM | HIGH | LOW | VERY HIGH |
| Measuring rate | VERY FAST | MEDIUM | MEDIUM | SLOW | MEDIUM |
| Multi-element measurements | YES | CONDITIONAL | YES | NO | YES |
| Device operation | SIMPLE | ADVANCED | ADVANCED | SIMPLE | VERY ADVANCED |
| Method creation | VERY SIMPLE | SIMPLE | COMPLEX | SIMPLE | COMPLEX |
| 24/7 – Measurement mode | YES | YES | YES | CONDITIONAL | CONDITIONAL |
An article on element analysis with flame photometers (AES) was also published in the journal LABO. PDF-download LABO August- edition or you can read the online article right on the LABO website.
A.KRÜSS article element analysis with flame photometer
Areas of application
Atomic emission spectrometry complies with all major international norms and standards, such as GMP/GLP, 21 CFR Part 11, and EU Annex 11. The technology is cutting-edge, fast, powerful and highly accurate.
Thanks to numerous technical improvements, the range of applications is now very broad: The FP8000 series is particularly well-suited for industrial processes that demand a high level of reliability or require uninterrupted continuous operation. The measurement devices offer very safe remote control options.
Thanks to the modular design of the analyzers, their functionality can be expanded at any time using retrofit kits. This makes it possible to react immediately to changes in application requirements, e.g. with an autosampler or an automatic dilution device (diluter).
Determining the concentration of alkali metal and flkaline earth metal, then flame photometer are essential measurement instruments in many laboratories. We have created an overview of the most important Applications and the recommended device models.
How to Use – Practical videos by experts
Buy a Flame Photometer—See All the Benefits in This Video
Complex laboratory analysis typically requires costly and time-consuming employee training and the careful development of methods. The Operation of our flame photometer requires little training, as the measurement technology is uncomplicated and the FP8000 series devices in particular have automated safety mechanisms and intelligent measurement data evaluation. Our customers appreciate the simple, intuitive operation of the user-friendly software.
The FP8000 series allows the use of user-prepared Calibration standards with freely selectable concentrations.
https://www.youtube.com/watch?v=7Nb0XcodewU&list=PLpOJLUHTZNMFKsyEoOa5pu6gAq5XuVBbP&index=2
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