8. The following data are for a series of external standards ofCd2+ 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 equationfor the calibration curve and report confidence intervals for theslope and the y-intercept.
(b) Construct a plot of the residuals and comment on theirsignificance.
At a pH of 3.7 the following data were recorded for the same setof 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 lowerpH?
(d) A single sample is buffered to a pH of 3.7 and analyzed forcadmium, yielding a signal of 66.3 nA. Report the concentration ofCd2+ in the sample and its 95% confidenceinterval.
