why potassium stock with 10000mg/L is added to the sodium standard solution with 20mg/L during the preparation for aas?

The addition of potassium stock solution with 10000mg/L to the sodium standard solution with 20mg/L during the preparation for atomic absorption spectroscopy (AAS) is done to create a mixed standard solution containing both sodium and potassium. This is done for a few reasons:

1. Analysis of Sample Matrix: AAS is a common analytical technique used to determine the concentration of specific elements in a sample. However, the accuracy and reliability of the analysis can be affected by the matrix of the sample, which includes all the other elements present in the sample. By adding a known concentration of a standard solution to the sample, we can account for any interference caused by these other elements. In this case, by adding potassium to the sodium standard solution, both sodium and potassium can be measured accurately.

2. Wavelength Calibration: AAS works by shining a light through the sample and measuring the absorption of light by the target element. The absorption of light is highly dependent on the wavelength of the light. By adding a mixture of sodium and potassium, we can calibrate the AAS instrument to measure the absorption at specific wavelengths for both elements. This ensures accurate and consistent measurements during the analysis.

3. Linearity Range: AAS instruments have a certain linear range over which accurate measurements can be obtained. By adding a higher concentration of potassium to the sodium standard solution, we can extend the linearity range of the instrument. This allows for a wider range of concentrations to be accurately measured.

To prepare the mixed standard solution, the following steps can be followed:

Step 1: Determine the desired concentration of each element in the mixed standard solution. For example, if you want a concentration of 10mg/L for sodium and 5000mg/L for potassium, adjust the volumes accordingly.

Step 2: Calculate the required volumes of the sodium standard solution and potassium stock solution to achieve the desired concentrations. Use the formula:

(Volume of Sodium Standard Solution x Concentration of Sodium) + (Volume of Potassium Stock Solution x Concentration of Potassium) = (Final Volume of Mixed Standard Solution x Desired Concentration of Sodium) + (Final Volume of Mixed Standard Solution x Desired Concentration of Potassium)

Solve this equation for the volume of each solution.

Step 3: Measure the calculated volumes of the sodium standard solution and potassium stock solution using appropriate glassware (e.g., pipettes or volumetric flasks).

Step 4: Combine the measured volumes in a clean container, then dilute with a suitable solvent to reach the desired final volume.

Step 5: Mix well to ensure homogeneity of the mixed standard solution.

By following these steps, you can prepare a mixed standard solution containing both sodium and potassium to be used in AAS analysis.