cfa 原理.doc

CFA
Theory
System layout
BRAN+LUEBBE Continuous-Flow Systems are used to automate wet-chemistry methods. Most types of aqueous samples can be analyzed.
A simple CFA System:
Sampler
Pump
Detector
PC
Cartridge
Each module fulfils a particular function such as sampling, measuring reagents and samples, mixing, incubation and measuring. The output from the system is a series of peaks whose height is proportional to sample concentration.
The development of Continuous-Flow Analysis
1. A simple Continuous-Flow system
2. ... used to measure
absorbance
Reagent
3. ... and for chemical
reactions
Reagent
4. ... + mixing/delay
ð to be continued
The development of Continuous-Flow Analysis
Sample
5. ... + air segmentation to reduce dispersion
Reagent
Air
6. + debubbling to remove interference from the bubbles
plete CFA System
Sample
Reagent
Air
Analytical Manifold
Mixing
Heating up to 95°C
Delay to plete reaction
Dialysis to separate interfering material in samples
On-line Distillation
On-line UV-digestion for Total N, P, C, CN, I, Fe and other parameters
On-line solvent extraction
Cadmium reduction (coil or column)
Ion-exchange
Detectors
Photometer, 340 - 900 nm
UV-Spectrometer, 190 - 900 nm
Fluorometer
Flame photometer
Hydraulic Flow
LAMINAR FLOW
When liquid flows through tubing at low speeds, the fluid in the centre moves faster than the liquid around the outside.
This difference in concentration along the tube ("dispersion") results in a long time delay after a change in concentration (. a new sample) before the concentration at the end reaches a constant value. This reduces the analysis rate or causes carryover between essive samples.
Time
Input signal
Output signal
SEGMENTED FLOW
Segmenting the stream with air bubbles reduces the dispersion. The bubbles must be large enough to fill the tubing, so that they separate the liquid segments. Each segment reacts under identical conditions as it passes through the system. T