In The Method Of Standard Addition Several Identical Samples Of The Unknown Are Mixed With Known Additional Amounts Of 1 (56.94 KiB) Viewed 35 times
In The Method Of Standard Addition Several Identical Samples Of The Unknown Are Mixed With Known Additional Amounts Of 2 (68.19 KiB) Viewed 35 times
In The Method Of Standard Addition Several Identical Samples Of The Unknown Are Mixed With Known Additional Amounts Of 3 (68.19 KiB) Viewed 35 times
In the method of Standard Addition, several identical samples of the unknown are mixed with known additional amounts of analyte. The signal for the resulting series of solutions is plotted versus the known standard concentration. A linear relation should be observed in which the concentration of the unknown will correspond to the negative of the x-intercept. Suppose we have a solution containing an unknown concentration of the ion Ca²+, and a standard Ca²+ solution of concentration [S]i = 10.0 µg/mL. Into each of five volumetric flasks (V₁ = 50.0 mL) we pipette V₁ -5.00 mL of unknown solution plus the various volumes of standard solution, indicated by V, below. The solution in each flask is diluted to the mark. Each resulting solution is subjected to an analytical technique which produces the signals shown in the following table: Sample Vs (ml) Signal 2 345 lo 1.00 2.00 3.00 4.00 0.182 0.241 0.300 0.357 0.413 Use linear regression analysis to determine the concentration of Ca²+ in the unknown solution as follows: a) The slope b) The y-intercept c) The standard deviation about regression d) Calculate the original (undiluted) concentration for this unknown - i.e. the negative of the x- intercept times the concentration factor. e) Calculate the standard deviation of the original (undiluted) unknown concentration.
In the method of Standard Addition, several identical samples of the unknown are mixed with known additional amounts of analyte. The signal for the resulting series of solutions is plotted versus the known standard concentration. A linear relation should be observed in which the concentration of the unknown will correspond to the negative of the x-intercept. Suppose we have a solution containing an unknown concentration of the ion Ca²+, and a standard Ca2+ solution of concentration [S]i= 10.0 µg/mL. Into each of five volumetric flasks (Vo = 50.0 mL) we pipette V₁=5.00 mL of unknown solution plus the various volumes of standard solution, indicated by V, below. The solution in each flask is diluted to the mark. Each resulting solution is subjected to an analytical technique which produces the signals shown in the following table: Sample Vs (ml) Signal 3 4 5 0 1.00 2.00 3.00 4.00 0.182 0.241 0.300 0.357 0.413 Use linear regression analysis to determine the concentration of Ca2* in the unknown solution as follows: a) The slope b) The y-intercept c) The standard deviation about regression d) Calculate the original (undiluted) concentration for this unknown - i.e. the negative of the x- intercept times the concentration factor. e) Calculate the standard deviation of the original (undiluted) unknown concentration.
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