Learn how to determine sodium by flame photometry. Explore what is flame photometry, determination of sodium with theory and procedure.
What is flame photometry?
Flame photometry is an analytical technique used to determine the concentration of specific chemical elements by measuring the emission of light.
This emission happened when a high temperature flame makes the chemical atoms excited. It is commonly using for alkali and alkaline earth metal analysis.
Determination of Sodium by flame photometry
Where the concentration of sodium in a sample is quantitatively measured using the principles of flame atomic emission spectroscopy. Here is the full laboratory guide for this:
Requirement
- Deionized water.
- Stock solutions of sodium chloride (C = 1 mg/ml.): Take 100 mg in 100 ml of deionized water.
- 100 ml volumetric flasks, Glass pipettes: 1ml, 2ml, 10 ml.
- Flame photometers.
Theory
Sodium (Na) is the major extracellular cation. It plays a role in body fluid distribution. Concentration of sodium ions inside the plasma (extracellular) is 130-145 mmol/l. Higher and lower concentrations are referred to as hypernatremia and hyponatremia, respectively.
When a solution containing cations of sodium and potassium is spayed into flame then the solvent evaporates and ions are converted into atomic state.
In the heat of the flame (temperature about 1800°C), small fraction of the atoms is excited. And relaxation of the excited atoms emitted light (photons) with characteristic wavelength (Na: 589 nm, K: 766 nm).
Procedure to determine sodium by flame photometry
Preparation of standard solutions:
Prepare standard solutions by dilution of stock solutions. Use different glass pipettes and numbered 100 ml volumetric flasks and prepare the solutions:
| Flask Number | Vol. of Pipette to Use (ml) | Vol. of Na Stock Solution to Pipette (ml) | Conc. of Solution Obtained (μg/ml) |
|---|---|---|---|
| 1 | 1 | 0.5 | 5 |
| 2 | 1 | 1 | 10 |
| 3 | 2 | 2 | 20 |
| 4 | 10 | 4 | 40 |
| 5 | 10 | 6 | 60 |
| 6 | 10 | 8 | 80 |
- Let the instrument warm up for 5-10 minutes.
- Feed distilled water to the instrument.
- Select the element sodium by turning the selector “Element Wahl”.
- Turn the outer knob “Messbereich” into position “100”.
- Pull the “Kompensaton I” knob slightly out and adjust readout to 0.
- Press the “Kompensation I” knob back.
- Readjust 0 reading with “Kompensation II” if necessary.
- Aspirate the most concentrated standard solution (solution number 6 and adjust readout to approximately 350 (on uppermost scale) using inner “Messbereich” knob.
- Aspirate distilled water – the instrument should read 0.
- Aspirate standard solutions no. 1, 2, 3, test solution, and then standards 4, 5, 6. Record the results.
- Take three readings.
- Aspirate distilled water for at least 5 minutes to clean the system.
Observation
| Sr. No. | Concentration (ppm) | Emission for Na+ (nm) |
|---|---|---|
Calculation
- Draw calibration curves for sodium on a sheet of millimeter-paper.
- Use concentrations as abscissa and instrument readouts as ordinate values.
- Find concentration of sodium ions in test solution from calibration curves.
Now write the report as the concentration of sodium is ……..ppm/ml.
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