1. Chemical Analysis Qualitative Analysis Quantitative Analysis Determination “Analyze” a paint sample for lead “Determine” lead in a paint sample

2. Bulk Material ↓ Sample ↓ Analytical Sample ↓ Analytical Matrix ↓ Analyte + Concomitants

3. BLANK Same concomitants No analyte Difficult if not impossible to acquire a true blank

4. INSTRUMENTAL ANALYSIS 1) Electroanalytical Chemistry 2) Spectrochemical Analysis 3) Chromatographic Separations

5. A Typical Instrument Analytical Sample Signal Generator Signal Transducer Signal Processor i Output V

6. Types of Signals 1.Emission of Radiation 2.Absorption of Radiation 3.Scattering of Radiation 4.Refraction of Radiation 5.Diffraction of Radiation 6.Rotation of Radiation 7.Electrical Potential 8.Electrical Current 9.Electrical Resistance 10.Mass-to-charge Ratio 11.Reaction Rate 12.Thermal Properties 13.Mass

7. Signal Sources 1)Analytical Signal 2)Blank Signal 3)Background Signal 4)Dark Signal Measured Signal:A combination of these

8. Analytical Figures of Merit “Indicate a characteristic of an instrumental technique for a given analyte” “7” Accuracy, Precision, Signal-to-Noise Ratio Sensitivity, Limit of Detection Linearity, Linear Dynamic Range

9. Accuracy Indicates how close the measured value is to the true analytical concentration Requires a Standard Reference Material (SRM) of other official measure NIST: National Institute of Standards and Technology

12. Accuracy Most commonly reported as percent error │C m - C t │ C t where: C m = measured concentration C t = true concentration x 100%

13. Precision Indicates the reproducibility of repetitive measurements of equivalent samples May be expressed as: 1.Standard Deviation (s or σ) 2.Relative Standard Deviation (RSD) 3.Confidence Limits

14. Precision

15. Standard Deviation For an infinite number of measurements (σ) For a finite number of measurements (s)

16. Standard Deviation Note that both s and σ have the same units as the original values How many values should be obtained? Rule of thumb: 16

18. How far is the measured mean from the true value?

19. How far is s from σ?

20. Short Cut: σ ≈ 1/5 (peak-to-peak noise)

21. Relative Standard Deviation RSD = σ/mean Where the mean may be the signal or the analyte concentration. RSD is a unit-less value, so σ must have the same units as the mean. RSD is often reported as %RSD, and may be used to compare different techniques.

22. Confidence Limits Define an interval that encloses the true value (C t ) with a specified level of confidence. 1. C m ± σ66.7% Confidence Level 2. C m ± 2σ95% Confidence Level 3. C m ± 3σ99.0% Confidence Level

23. Signal to noise Ratio (S/N) S/N = S m /σ = 1/RSD Notes: 1.N = noise (σ) 2.S/N is unitless 3.Always try top maximize S/N 4.S/N is used to compare instruments 5.A plot of S/N versus an instrumental parameter reaches a maximum at the optimum value for that parameter

24. Sensitivity Experimental slope of a calibration curve m = ΔS/ΔC Sensitivity is almost always specific for one particular instrument.

26. Limit of Detection The analyte concentration yielding an analytical signal equal to 3 times the standard deviation in the blank signal. LOD = 3 x σ bl / m By definition, the LOD has just one significant figure!!

27. Linearity Measure of how well the observed data follows a straight line. S A = mC S A = Analytical Signal m = calibration sensitivity Remember S A = S tot - S bl

28. Linearity Plot log(S) versus log(C) log(S A) = log(m) + log(C) The slope of this plot should be 1.00 A calibration curve is defined as linear if the log-log plot has a slope in the range 0.95-1.05

29. Linear Dynamic Range The concentration range over which the calibration curve is linear Lower End → LOD Upper End Analyte Concentration where the observed signal falls 5% below the extrapolated line

30. LDR Units are “orders of magnitude” or “decades” of analyte concentration LDR is easiest to observe on log-log plot If linearity is poor, define an analytically useful range (AUR)

31. Other figures of merit may be calculated, but these 7 are sufficient. Selectivity and Resolution may be useful in cases where more than one analyte is determined in the same sample.