Atomic absorption spectroscopy was used to determine the amount of aluminum in a

Question

Atomic absorption spectroscopy was used to determine the amount of aluminum in a sample of sunscreen. A standard solution of 1.00 ng Al/L was prepared and measured seven times to determine the detection and quantitation limits of the spectrometer. The standard measurements were as follows: 0.79, 0.85, 1.30, 1.17, 0.86, 1.15, and 0.96 ng Al/L. Use the equations provided in the "Hint" section below to calculate the detection and quantitation limits for this instrument.

Atomic absorption spectroscopy was used to determine the amount of aluminum in a sample of sunscreen. A standard solution of 1.00 ng Al/L was prepared and measured seven times to determine the detection and quantitation limits of the spectrometer. The standard measurements were as follows: 0.79, 0.85, 1.30, 1.17, 0.86, 1.15, and 0.96 ng Al/L. Use the equations provided in the "Hint" section below to calculate the detection and quantitation limits for this instrument. Number Detection Limit ng/L Quantitation Limit Limt Number ng/L

Explanation / Answer

Let us calculate the standard deviation from given data,

Mean = 0.79 + 0.85 + 1.30 + 1.17 + 0.86 + 1.15 + 0.96/7 = 1.01143

(Mean - value)^2

0.22143^2 = 0.0490312

0.16143^2 = 0.02606

-0.28857^2 = 0.0832726

-0.15857^2 = 0.0251444

0.15143^2 = 0.022931

-0.13857^2 = 0.0192016

0.05143^2 = 0.002645

variance = 0.0326122

standard deviation = 0.18059

So,

Detection limit = 3 x standard deviation = 3 x 0.18059 = 0.54177 ng/L

Quantitation limit = 10 x standard deviation = 10 x 0.18059 = 1.8059 ng/L

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