Transcript PowerPoint 簡報

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.
3. selection of analytical methods
Criteria for selection
a. Precision:
Absolute standard deviation, s =
∑(xi -x)2
n -1
Variance = s2
Relative standard deviation (also called coefficient of variation), RSD
RSD =
s
x 100%
X
where X = ∑xi / n
i
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
Signal
analytical sensitivity = m/ss
standard deviation
concentration
d. dynamic range
Linear range, dynamic range, or expressed as decade of DL
Signal, y
y'
y"
y"-y' = 0.03 y'
Dy
Slope = m = D y/Dx = dy/ dx
Dx
10 sblank
3 sblank
concentration, x
Limit of detection
Up Limit of quantification
Limit of quantification
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.
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
4. Calibration methods,
a. Calibration curves (working curve, analytical curve)
Signal
concentration
b. standard addition method
To eliminate the effect of matrix
CX
CS
S = unknown + standard solution
= k(Cx Vx/Vt + Cs Vs/Vt)
= k1 + k2Vs
Analytical signal
VX
VS
Vt
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
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
Signal
CA1
CA2
concentration
CA3
SA/SB
CB
internal standard
CA4
CA5
concentration
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
b. Shot noise
Caused by electron or other charged particles cross a junction
i rms = (2 Ie Df)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.)