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Chapter 1: Introduction 1. Type of instrumental methods Radiation Electrical method

Chapter 1: Introduction 1. Type of instrumental methods Radiation Electrical method Thermal properties Others 2. Instruments for analysis Non-electrical domain: density, length, mass, intensity of radiations, etc. electrical domain: current, voltage, frequency, etc. s. x 100%.

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Chapter 1: Introduction 1. Type of instrumental methods Radiation Electrical method

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  1. Chapter 1: Introduction 1. Type of instrumental methods Radiation Electrical method Thermal properties Others 2. Instruments for analysis Non-electrical domain: density, length, mass, intensity of radiations, etc. electrical domain: current, voltage, frequency, etc.

  2. s x 100% ∑(xi -x)2 n -1 = ∑xi / n i X X 3. selection of analytical methods Criteria for selection a. Precision: Absolute standard deviation, s = Variance = s2 Relative standard deviation (also called coefficient of variation), RSD RSD = where

  3. Signal concentration b. accuracy: Bias = m - x true value c. sensitivity: the signal when C=0 S = m C + Sblank slope = m, an indicator of the sensitivity analytical sensitivity = m/ss standard deviation

  4. d. dynamic range Linear range, dynamic range, or expressed as decade of DL Signal, y y"-y' = 0.03 y' y' y" Slope = m = D y/Dx = dy/ dx Dy Dx 10 sblank 3 sblank concentration, x Up Limit of quantification Limit of detection Limit of quantification

  5. e. detection limit The signal from analyte can be distinguished from noise level of the blank. Sm = Sblank + k Sblank standard deviation of blank average blank signal (n =20 ~ 30) Detection limit: expressed as the concentration, CL, or the quantity, qL, is derived from the smallest measure, xL, that can be detected with reasonable certainty for a given analytical procedure. Fro detection limit, k is around 3.

  6. f. selectivity Free from interference by other species contained in the sample matrix. S = mACA + mB CB + mCCC + Sblank Selectivity coefficient for A with respect to B, kB,A = mB/mA Selectivity coefficient for A with respect to C, kC,A = mC/mA

  7. Signal concentration 4. Calibration methods, a. Calibration curves (working curve, analytical curve)

  8. b. standard addition method To eliminate the effect of matrix CS CX S = unknown + standard solution = k(Cx Vx/Vt + Cs Vs/Vt) = k1 + k2Vs Analytical signal S = m Vs + b where b = k1 = k VxCx/Vtm = k2 = k Cs/Vt m = k2 = k Cs/Vt So, b/m = VxCx/Cs So, Cx = b Cs/ m Vx VX VS Vt

  9. c. internal standard method Inj. larger amount A Inj. smaller amount Inj. larger amount A, B Inj. smaller amount Ratio value will be the same

  10. Signal concentration CA1 CA2 CA3 SA/SB CB internal standard CA4 CA5 concentration

  11. Chapter 5: Signals and Noise 1. Definition of signal-to-noise ratio S/N ratio = mean/standard deviation = x/s = 1/RSD 2. Source of Noise i. Chemical noise Fluctuation from variation of temperature, pressure, chemical equilibrium, moisture, etc. ii. Instrumental Noise a. Thermal Noise (Johnson noise) It is caused by the thermal agitation of electrons or charge carries. This agitation of charged particles is random and periodically creates charge inhomogeneities. nrms = (4 KTR Df)1/2 K is Boltzman constant, T is temperature in (K), R is resistance and Df is frequency bandwidth

  12. b. Shot noise Caused by electron or other charged particles cross a junction irms= (2 IeDf)1/2 c. flicker noise The causes of it are unknown It is proportional to 1/f d. Environmental noise i.e. temperature, shaking of building, electromagnetic from any where (TV, radio, etc.)

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