Quantitative X-ray photoelectron spectrometry has become more popular inrecent years

Chapter 21, Problem 21-14

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Quantitative X-ray photoelectron spectrometry has become more popular inrecent years. The factors relating the intensity of emission to atomic concentration(density) are given in Equation 21-3.(a) Of the factors influencing the emission intensity, identify those related to theanalyte.(b) Identify the factors influencing the emission intensity related to the spectrometer.(c) The measured quantity in quantitative XPS is usually liS, where I is the peakarea and S is the sensitivity factor for the element of interest. If this quantityis measured for the analyte (liS), and the corresponding value measured foran internal standard with a different transition (liS)" show by means of anequation how the ratio (/S),/(/S), is related to the atomic concentrationratio of the analyte to the internal standard.(d) If all the elements on a surface arc measured by XPS, show that the fractionalatomic concentration fA of element A is given by where In is the measured peak area for element n, Sn is the atomic sensitivityfactor for that peak, and the summation is carried out over all n.(e) For a polyurethane samplc in which carbon, nitrogen, and oxygen were detectedby XPS, the sensitivity factor for C was 0.25 on the spectrometerused. The sensitivity factor for N was 0.42 and that for 0 was 0.66 on thesame spectrometer. If the peak areas were C(ls) = 26,550, N(Is) = 4475,and O( Is) = 13,222, what were the atomic concentrations of the threeelements')(f) What are the limitations of quantitative analysis with XPS" Why might theatomic concentrations measured not correspond to the bulk composition"(g) For polyurethane, the stoichiometric atomic concentrations are C = 76.0%,N = 8.0%, and 0 = 16.0%. Calculate the percentage error in the valuesobtained in part (e) for each element.