Instrumental Analysis ACS Exam 2026 Questions with Answers

Instrumental Analysis ACS Exam 2026
Questions with Answers

How to calculate signal to noise - ANSWER-S/N = mean/STDEV


-inverse of RSD
-STDEV: 5 (#STDEV gaussian curve)
-STDEV: peak-to-peak noise/5


S/N relationships - ANSWER--increase S/N, increase run time
-decrease noise, increase S/N


Beer's Law - ANSWER-


Beer's Law Calculations - ANSWER-


Hard ionization vs soft ionization - ANSWER--hard: no M+ peak (or small)
-soft: M+ peak is visible


MS: hard ionization sources - ANSWER--impart high quantities of residual energy
in the subject molecule invoking large degrees of fragmentation


MS: hard ionization sources examples - ANSWER--electron impact

, Electron Impact (EI) - ANSWER--Uses electron impact to ionize a molecule
-gas phase
-energetic electrons
-possibility of over fragmentation
-hard
-most common


EI advantages - ANSWER--good stability
-universal ionization
-reproducible spectra


EI disadvantages - ANSWER--MW can be hard to determine
-compatible only with volatiles (GCMS)
-Hard to make negative ions


MS: soft ionization sources - ANSWER--processes which impart little residual
energy onto the subject molecule and as such result in little fragmentation


MS: soft ionization sources examples - ANSWER--CI
-ESI
-MALDI