《仪器分析 Instrumental Analysis》课程教学资源（教材讲义）13 Flow Injection Analysis

Flow Injection Analysis (Chapter 33) Automatic no feedback to control Automated-feedback to control Advantages of Automation (1)Economic operator costs reduced waste human errors (2)Speed (3)Precision Disadvantages of Automation: (1)Cost Initial purchase Setup cost (2)Inflexible Two types of auto analysis (A)Discrete/batch-sample remains isolated throughout (robot,no cross-contamination problem) (B)Continuous-sample introduced into stream(simpler instrumentation,more efficient) CEM 333 page 13.1

Flow Injection Analysis (Chapter 33) Automatic - no feedback to control Automated - feedback to control Advantages of Automation: (1) Economic operator costs reduced waste human errors (2) Speed (3) Precision Disadvantages of Automation: (1) Cost Initial purchase Setup cost (2) Inflexible Two types of auto analysis (A) Discrete/batch - sample remains isolated throughout (robot, no cross-contamination problem) (B) Continuous - sample introduced into stream (simpler instrumentation, more efficient) CEM 333 page 13.1

Flow Injection Analysis (FIA)developed in response to need for automated analysis -especially in clinical field Fig 33-1 Peristaltic pump Reactor Sample Photometer nL/mir coil 50cm W ⊙+To Fe3+ 0.50mm waste (a) A 08 (b) K75 (c) 6 6 min 30 15s 0 0.0 Time (b) CEM 333 page 13.2

Flow Injection Analysis (FIA) developed in response to need for automated analysis - especially in clinical field Fig 33-1 CEM 333 page 13.2

In first instruments,regular air bubbles introduced to (i)reduce dispersion(diffusion along tube) (ii)improve mixing Air-segmented continuous flow analysis (ASCFA) Mixing Air Bubbles Detector A Reagent AO Reagent B Reaction Net Flow Bolus Flow Profile But.bubbles (i)increase analysis time (ii)require bubble introduction/removal (bubble gate) (iii)increase startup/settle time CEM 333 page 13.3

In first instruments, regular air bubbles introduced to (i) reduce dispersion (diffusion along tube) (ii) improve mixing Air-segmented continuous flow analysis (ASCFA) Reagent A Reagent B Air Mixing Bubbles Net Flow Bolus Flow Profile Reaction Detector But, bubbles (i) increase analysis time (ii) require bubble introduction/removal (bubble gate) (iii) increase startup/settle time CEM 333 page 13.3

However,in FIA system with narrow id tubing and low flow rates no need for bubbles At injection,sample zone (plug)concentration profile is rectangular Profile changes downstream (i)Laminar flow profile develops due to friction with walls Net Flow Laminar Flow Profile (ii)Radial diffusion from center to walls of tube (iii)Longitudinal diffusion in forward and backward flow directions CEM 333 page 13.4

However, in FIA system with narrow id tubing and low flow rates no need for bubbles At injection, sample zone (plug) concentration profile is rectangular Profile changes downstream (i) Laminar flow profile develops due to friction with walls Net Flow Laminar Flow Profile (ii) Radial diffusion from center to walls of tube (iii) Longitudinal diffusion in forward and backward flow directions CEM 333 page 13.4

Direction of flow Time Time Time Time (a ) (c) (d) Fig 33-5 When flow rate/tube id is small (d)is approached-no need for bubbles！ Radial diffusion from walls to center helps minimize cross- contamination between sample plugs CEM333 page 13.5

Fig 33-5 When flow rate/tube id is small (d) is approached - no need for bubbles! Radial diffusion from walls to center helps minimize cross￾contamination between sample plugs CEM 333 page 13.5

Sample Introduction Injection valve:(Fig 28-7) Load sample Inject sample Loop To To column column From pump From pump Ven ent (① allows loading of specified volume of analyte(5-200 uL) (ii)rapid injection of sample plug into flow without disturbing tube flow Pumps:(Fig 33-2) (i)Variable speed peristaltic pump (ii)Flow rate(0.0005 to 40 mL/min)controlled by pump speed and tube id CEM 333 page 13.6

Sample Introduction Injection valve: (Fig 28-7) (i) allows loading of specified volume of analyte (5-200 µL) (ii) rapid injection of sample plug into flow without disturbing tube flow Pumps: (Fig 33-2) (i) Variable speed peristaltic pump (ii) Flow rate (0.0005 to 40 mL/min) controlled by pump speed and tube id CEM 333 page 13.6

Tubes and Reactors: (i)Small tube diameters (<0.1-1 mm id) (ii)Reactor coil (<50 cm long)tightly wound to increase mixing Detection: (i)Photometer(singleA) (ii)UV-vis spectrophotometer(multichannel detection) To waste UV sourc To wast (iii)Electrochemical(potentiometry) (iv)Atomic spectroscopy(AES or AAS) CEM333 page 13.7

Tubes and Reactors: (i) Small tube diameters (<0.1-1 mm id) (ii) Reactor coil (<50 cm long) tightly wound to increase mixing Detection: (i) Photometer (single l) (ii) UV-vis spectrophotometer (multichannel detection) (iii) Electrochemical (potentiometry) (iv) Atomic spectroscopy (AES or AAS) CEM 333 page 13.7

Instrumentation can be quite complex: Example:phase mixing NaOH Phase separation Aqueous samples Peristaltic 25-or 12-uL pump Sample 0.16 M NaOH 2.2 mL/min 0.8mm p Wa ① w ○ Ice bath】 0.8mm 0.7 mL/min 275nm Photometer Waste ste aOH phase mixing Fig 33-8 CEM 333 page 13.8

Instrumentation can be quite complex: Example: phase mixing Fig 33-8 CEM 333 page 13.8

Quantifying Diffusional Processes in FIA Dispersion: concentration in injection volume D=Co c peak concentration at detector Calibration needed to find D D affected by (i)sample volume (ii)tube length (ii)）flow rate (iv)tube id CEM 333 page 13.9

Quantifying Diffusional Processes in FIA Dispersion: concentration in injection volume D = c0 c peak concentration at detector Calibration needed to find D D affected by (i) sample volume (ii) tube length (iii) flow rate (iv) tube id CEM 333 page 13.9

Fig 33-6 D: Co 40800 Steady state 10 0.5 20 cm 0 2.0 200 10 )cm -208 -Time- 0 60 12 Time,s (a) 6) Large injection volume:D 1.0 (no analyte dilution by carrier) Low volume:D>1.0 (analyte dilution) Short tubes:less time for diffusion low dispersion Long tubes:long time for diffusion high dispersion CEM 333 page 13.10

Fig 33-6 Large injection volume: D = 1.0 (no analyte dilution by carrier) Low volume: D > 1.0 (analyte dilution) Short tubes: less time for diffusion = low dispersion Long tubes: long time for diffusion = high dispersion CEM 333 page 13.10