Cheers. I wanted to know how much Mg, Ca, K and Na a specific Salt had. So I weighted 1g of the material, left it 24h to dry remeasured its mass, and then another 24h at 500ºC. After that the sample was measured once again, and final mass after the 500ºC registered. Final mass 0.9921 mg It was digested with 3x 10 mL HCL 3N, which I supposed doesn't matter as it fully evaporates every time. Now the problematic part. The sample was filtered with water and made a solution of 100mL. From this 100 mL solution, after some attempts to fit the calibration curves for each element, the following amounts of the solution were added to 50 mL flask according to the element being analysed together with 1mL of inferent(CsCl2 for Na and K, SrCl2 for Mg and Ca) and completed with water.: 5mL for Mg 2.5 mL for K 20 ml for Ca 250 ul for Na(this was harder to measure) the diluted results were Mg: 0.2757 mg/L K: 0.4712 mg/L Ca: 0.9684 mg/L Na: 2.8579 mg/L How do i account with all of the dilutions to obtain a value in mg/g? does it matter which dilution I start with? the first to 100mL or the second to 50 mL? My guess Is I am missing something pretty obvious.
Draw a schematic diagram showing the dilutions and keep track of initial and final volumes on a piece of paper. Simply use the dilution formula and calculate backwards from the most dilute solution towards the most concentrated one. Suppose we dissolved 2 g sample in 100 mL flask A, you took a 10 mL portion of this sample and transferred to a 50 mL flask B. The conc. of Na in flask B was found to be 70 mg/L.
Ci Vi= Cf Vf ( i - initial, f=final)
Flask B had a final conc. of 70 mg/L= Cf
Initial volume in flask B = 10 mL = Vi from flask A
Final volume of flask B = 50 mL
What was the initial conc. in flask A, solve for Ci (mg/L)
Do these steps and see if that makes sense.
The second part will be, from Ci to actual mass of Na in the 2g sample. Note that this conc. Ci was meant for a liter. You actual sample is not present in 1 L. Scale the amount for 100 mL- the original flask A using simple ratio and proportion.
Draw a schematic diagram showing the dilutions and keep track of initial and final volumes on a piece of paper. Simply use the dilution formula and calculate backwards from the most dilute solution towards the most concentrated one. Suppose we dissolved 2 g sample in 100 mL flask A, you took a 10 mL portion of this sample and transferred to a 50 mL flask B. The conc. of Na in flask B was found to be 70 mg/L.
Ci Vi= Cf Vf ( i - initial, f=final)
Flask B had a final conc. of 70 mg/L= Cf
Initial volume in flask B = 10 mL = Vi from flask A
Final volume of flask B = 50 mL
What was the initial conc. in flask A, solve for Ci (mg/L)
Do these steps and see if that makes sense.
The second part will be, from Ci to actual mass of Na in the 2g sample. Note that this conc. Ci was meant for a liter. You actual sample is not present in 1 L. Scale the amount for 100 mL- the original flask A using simple ratio and proportion.
Dear ,
It is recommended to reduce steps of analytical procedures because each step goes with errors and contribute to uncertainty of the results.
As per your objective of knowing concentration of Na,K,Ca,Mg in a salt by AAS, I will suggest just dissolve your salt in acqeous solution slightly acidified and test the absorbance for each parameter. You take a tube with your dissolved sample and suck it with the nebulizer tube and see how absorbance is. If it is high (>3abs for e.g) then decide for dilution factor. I do not think your salt sample needs to undergo all of the aforementioned steps. I would rather optimize mass of sample (0.2-1.0), and proceed with digestion if necessary then conduct flame spectrometric analysis. Otherwise, make schematic diagram of dilution steps for comparison.
I ask you to confirm if the value of the mass at the end is 0.9921mg because the sum of mass K, Na, Mg, Ca for 1 gram of sample should give values less than or equal to 0.9921mg. However, when applying dilution factor, this value is not verified
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