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  • The BWB Team

Flame Photometer Samples: Preparing for efficiency and speed

It would be nice if body scanners and handheld medical tricorders from Star Trek existed.  Indeed, something similar is already in limited use, with an equally competent real life tricorder-like device possible within the decade.  However, since the beloved Dr. Leonard McCoy isn’t due to be born until the year 2227, we’re going to have to make do with what we have now. 

Luckily, for primitive 21st century humans, BWB Flame Photometers are among the most advanced analysis equipment available for vital detection of alkali and alkali earth metals.  They crank out fast, reliable results at a rate up to 120 per hour or more, detailing all the metal ions at once, instead of requiring a complete test for each individual sample.

To attain that speed, samples must be prepared beforehand.  The most basic requirement is that the sample be a solution, completely without solids.  It must be aspirated through a very fine needle into a flame to release the ions so they can produce the light we need for analysis.

Bodily Fluids

Blood, plasma, red cells, urine, etc., are best diluted (proportionally) to make sure when you’re testing for sodium and potassium (for example) that they will fall in the 100 ppm range whereas the Flame photometer offers its greatest accuracy for those substances.

Calcium and Barium, on the other hand, are most accurately quantified closer to 300 ppm, though they can be detected at much lower levels.  If your sample is likely to fall in the 100 ppm range, you can vacuum evaporate it to one-third volume (to triple the concentration) and the flame photometer readout can be divided by three to give you a much more precise result than if you simply tested the 100 ppm solution.

This is not strictly necessary, but rather entirely dependent on what your customer specifies as the required accuracy.  If you charge “X” for 3% accuracy, it makes sense to charge “X + x%” for higher levels like 1% or 0.5% accuracy because of the additional prep-work involved.

Testing Solids

 For the testing of organic solids, the samples of known mass are burnt to ash, typically in a ceramic bowl, in a lab oven (furnace).  Once water loss is no longer detected it is removed from the oven, allowed to cool, and then treated with small quantities of Nitric acid, Perchloric Acid, Hydrochloric Acid (et al), which is all fine since hydrogen, oxygen, chlorine, nitrogen, and sulphur are not reactive enough to colour the low temperature flame of a photometer.

Once the solids are “digested” the test solution can be strained through filter paper to remove any remaining bits that could clog the aspirator.  Add enough deionised water to make 100ml.  This is now your testing solution.

Blank Solutions

Generally, you’ll need to make a “blank” solution for calibration purposes.  If during processing of your sample you added 10 ml of Perchloric Acid, and 20 ml of Nitric Acid, those will have to be added to your blank solution, too.  This eliminates crosstalk (ionic interference), keeping the results accurate.

Using a 100 ml flask, pour in 50 ml of deionised water (Safety tip: always add acid to water, and never add water to acid).  Now add precisely the same quantity of any acids used to prepare your test solution to the water, and then fill the flask to the 100 ml mark.  Label this “Blank Solution”.

Standard Solutions

Standard solutions can be purchased in high or very high concentrations to simply your work.  High (1,000 ppm) or very high (10,000 ppm) solutions are handy, inexpensive and increase efficiency.  Very High PPM solutions are quite durable when stored in glass containers that are well sealed.  Low PPM solutions (< 100 PPM) deionise quickly and render inaccurate results so should not be stored.

You can make Standard Solutions, particularly if you use a lot of them very quickly and shipping in your country is sometimes unreliable.  Let’s quickly look at a Calcium Stock solution at 1,000 PPM.

Weigh 2.498 grams of calcium carbonate and place in a 1,000 ml flask.  Add 100 ml of deionised water.  While stirring or agitating, add up to 20 ml of hydrochloric acid drop-by-drop until all the solids are dissolved.  Add more deionised water up to the 1,000 ml line and you now have your 1,000 PPM Calcium Stock Solution.

Knowing how much calcium carbonate is needed to obtain the calcium concentration you require is a simple look-up online if you don’t have a chart in front of you.  Many people have done this before, so there is no need to reinvent the wheel!

Set up as many 100 ml flasks as needed.  In the first flask place 0.5 ml of the Stock solution, in the second 1.0 ml, in the third 1.5 ml, and 2.0 ml in the fourth (continuing or altering until your requirements are met).

When each flask is then filled with deionised water to the 100 ml line, these examples will render 5 PPM, 7.5 PPM, 10.0 PPM, 12.5 PPM, and so on (respectively).  Any concentration you need for calibrating is just a simple mathematical calculation away.

The Takeaway

One could invest in pricey high tech equipment such as a Gas Chromatograph or full-fledged Mass Spectrometer, but unless there is a clear need for such devices, it is definitely overkill.  They take time, report on a single sample element being investigated, they take time, require large amounts of consumables for each test, and they take time!

Training time for those complex machines is much longer than on a Flame Photometer, particularly one from BWB Technologies, which is automated and computerised to make the whole process easier.  A new employee can be running tests and generating results and income in less than a day!

If you need to be running tests for customers in medicine or bio-medicine, pharmacology, water treatment, agriculture, commercial food packaging, or innumerable other fields, BWB Tech is here to help you be the dependable, cost effective service provider that customers come to rely on every day!  Our people are always ready to help you to become that vital in-demand service that powers so many labs around the world.  Call us…we’d love to hear from you!


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