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.
X = ∑x i / n i 3. selection of analytical methods Criteria for selection a. Precision: Absolute standard deviation, s = Variance = s 2 Relative standard deviation (also called coefficient of variation), RSD RSD = ∑(x i -x) 2 n -1 s X x 100% where
Bias = - x b. accuracy: c. sensitivity: true value slope = m, an indicator of the sensitivity S = m C + S blank the signal when C=0 Signal concentration analytical sensitivity = m/s s standard deviation
Signal, y concentration, x y' y" y"-y' = 0.03 y' Slope = m = y/ x = dy/ dx yy xx 3 s blank Limit of detection Up Limit of quantification 10 s blank Limit of quantification Linear range, dynamic range, or expressed as decade of DL d. dynamic range
e. detection limit The signal from analyte can be distinguished from noise level of the blank. S m = S blank + k S blank average blank signal (n =20 ~ 30) standard deviation of blank Detection limit: expressed as the concentration, C L, or the quantity, q L, is derived from the smallest measure, x L, that can be detected with reasonable certainty for a given analytical procedure. Fro detection limit, k is around 3.
f. selectivity Free from interference by other species contained in the sample matrix. S = m A C A + m B C B + m C C C + S blank Selectivity coefficient for A with respect to B, k B,A = m B /m A Selectivity coefficient for A with respect to C, k C,A = m C /m A
4. Calibration methods, a. Calibration curves (working curve, analytical curve) Signal concentration
b. standard addition method To eliminate the effect of matrix CXCX CSCS VSVS VXVX Vt S = unknown + standard solution = k(C x V x /V t + C s V s /V t ) = k 1 + k 2 V s Analytical signal S = m V s + b where b = k 1 = k V x C x /V t m = k 2 = k C s /V t m = k 2 = k C s /V t So, b/m = V x C x /C s So, C x = b C s / m V x
c. internal standard method A Inj. larger amount Inj. smaller amount A, B Inj. larger amount Inj. smaller amount Ratio value will be the same
C A1 C A2 C A3 C A4 C A5 Signal concentration S A /S B concentration C B internal standard
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. rms = (4 KTR f) 1/2 K is Boltzman constant, T is temperature in (K), R is resistance and f is frequency bandwidth
b. Shot noise Caused by electron or other charged particles cross a junction i rms = (2 I e f) 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.)