UV-Vis(Absorption)Spectrometry (Chapters 13,14) Beer's Law: A=ebc=-logT=-log=log Io Absorbance is additive Atotal =A1+A2. =E1bC+￡2bc2. in a 2 component mixture A%1=81,1bC1+82,1bc2 A2=81,2bC1+82,.2bC2 Limitations of Beer's Law (pp 303-311): (1)Chemical effects-analyte associates,dissociates or reacts to give molecule with different s 1.000 0.800 0.600 元=430nm .40 2=570nm 0.20 .00 4.00 8.00 12.00 16.00 Indicator concentration,Mx10 Fig 13-3 CEM 333 page 4.1
UV-Vis (Absorption) Spectrometry (Chapters 13, 14) Beer's Law: A = ebc = -logT = -log I I0 = log I0 I Absorbance is additive Atotal = A1 + A2 . = e1bc1 + e2bc2 . in a 2 component mixture Al1 = e1,l1 × b× c1 + e2,l1 × b× c2 Al2 = e1,l2 ×b ×c1 + e2,l2 × b ×c2 Limitations of Beer's Law (pp 303-311): (1) Chemical effects - analyte associates, dissociates or reacts to give molecule with different e Fig 13-3 CEM 333 page 4.1
(2)Physical effects-stray light,polychromatic radiation or noise Ax=-l0gT =x bc 1o =1og1) 11=l010ac 12=l021082c 104+l02 A1x+122 L01+02 (10210+10,10ag Az=loe0x1+102）1og0,10e+10,10e） CEM 333 page 4.2
(2) Physical effects - stray light, polychromatic radiation or noise Al1 = -logTl1 = el1 bc = log I0 I æ è ç ö ø ÷ l1 I l1 = I 0 l1 10-e l1 bc I l2 = I0 l2 10 -e l2 bc Al = I 0 l1 + I 0 l2 I l1 + Il 2 æ è ç ç ö ø ÷ ÷ = I 0 l1 + I 0 l2 I0 l1 10-e l1 bc + I0 l2 10-e l2 bc æ è ç ç ç ö ø ÷ ÷ ÷ Al = log I 0 l1 + I 0 l2 ( ) - log I 0 l1 10-e l1 bc + I 0 l2 10-e l2 bc ( ) CEM 333 page 4.2
>non-linear calibration curve (Fig 13-4,13-5) 1.00 0.80 410删 兰0.60 36捌 20.40 g2380 0.20 2.04.06.08.010.0 Concentration,Mx 104 Band A Band b -Band A Band B Wavelength Concentration CEM 333 page 4.3
® non-linear calibration curve (Fig 13-4, 13-5) CEM 333 page 4.3
Typical UV-Vis Spectrophotometers: (Fig13-12) includesλselection Filter or Amplifier Filter or monochromator Amplifier Filter or (a)single beam (SB)(b)double-beam (DB)-in-space (c)double- beam-in-time CEM 333 page 4.4
Typical UV-Vis Spectrophotometers: (Fig 13-12) includes l selection (a) single beam (SB) (b) double-beam (DB)-in-space (c) doublebeam-in-time CEM 333 page 4.4
Multichannel Spectrophotometer No monochromator,but disperses transmitted light and measures"all wavelengths at once"(Fig 13-13) Polychromatic sour 米 Lens Photodiode array No scanning-simple and fast More expensive Limited resolution CEM 333 page 4.5
Multichannel Spectrophotometer No monochromator, but disperses transmitted light and measures "all wavelengths at once" (Fig 13-13) No scanning - simple and fast More expensive Limited resolution CEM 333 page 4.5