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8. The following data are for a series of external standards of Cd2+ buffered to a...

8. The following data are for a series of external standards of Cd2+ buffered to a pH of 4.6.14

[Cd2+] (nM) 15.4 30.4 44.9 59.0 72.7 86.0

Sspike (nA)    4.8 11.4 18.2    26.6    32.3    37.7

(a) Use a linear regression analysis to determine the equation for the calibration curve and report confidence intervals for the slope and the y-intercept.

(b) Construct a plot of the residuals and comment on their significance.

At a pH of 3.7 the following data were recorded for the same set of external standards.

[Cd2+] (nM) 15.4 30.4 44.9 59.0 72.7 86.0

Sspike (nA) 15.0    42.7 58.5 77.0 101    118

(c) How much more or less sensitive is this method at the lower pH?

(d) A single sample is buffered to a pH of 3.7 and analyzed for cadmium, yielding a signal of 66.3 nA. Report the concentration of Cd2+ in the sample and its 95% confidence interval.

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milcah answered 1 year ago
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