Dr Hanif other methods

• Flow Injection Analysis (FIA)


  A well established technique that becomes the fastest growing concept in analytical chemistry
• FIA


  • It is one of the automated and continuous flow method of analyses
  • It is an extension of the segmented-flow procedures which were widely used in clinical laboratories in the 1960s & 1970s for automatic routine determination of a varieties of analytes in blood and urine samples
• FIA procedure


  1. Sample is injected using a valve and forms a zone which is then transported towards a detector that continuously records the absorbance, electrode potential, or other physical parameter

  2. In segmented-flow procedures, closely spaced air bubbles are used to prevent excess sample dispersion and to promote turbulent mixing of samples and reagents and prevent cross-contamination between successive samples

  
• Principle of FIA


  • FIA is based on the injection of a liquid sample into a moving, non-segmented, continuous flow stream of suitable liquid or reagent inside of a tubing
  • The colour product is produced which is then detected by the detector placed at the end of the tubing

  
• Dispersion of sample in FIA

  • Convection due to the laminar flow of the carrier stream
  • Diffusion due to concentration gradient between sample and carrier stream
• Effect of dispersion on the shape of a sample's flow profile at different times during a FIA

  • At injection

  Convection dominates dispersion

  Convection and diffusion contributes to dispersion (3-20s after injection)

  Diffusion dominates dispersion (after 25s after injection)
• Radial diffusion


  Important in FIA to help integrity of sample and preventing mixing with next sample on the line
• Parameters in FIA


  ta - travel time, from injection to detector

  T - residence time, the from injection to maximum peak

  t' = T-ta

  Δt - the baseline-to-baseline time, is the time between the arrival of the sample's leading edge to the departure of its trailing edge

  T' - The elapsed time between the maximum signal and its return to the baseline

  h - the sample's peak height

  
• FIA system for determination of Cl- ions


  • Flow diagram

  Recorder traces for standards 5 - 75 ppm Cl and fast scan of standards 30 & 75 ppm
• FIA system for determination of calcium in water


  • Flow injection system by formation of coloured complex with o-cresolphthalein complexone at pH 10

  Recorded output of triplicate determination of sample and duplicate determination of standards
• Instrumentation of FIA


  Reagent is pumped by a peristaltic pump directly into a valve that permits injection of samples into the flowing stream of reagent

  The sample and reagent are then passed through a reactor coil where the reagent diffuses into the sample 'plug' and produces a coloured product, which then flow into a detector

  The reactor coil is coiled section of tubing 1 cm or less diameter which enhance axial dispersion and increase radial mixing of sample and reagent and lead to symmetric peaks

  The results are recorded on a chart recorder

  
• Sample injector and detector in FIA

  • Injector and detector used in FIA are similar in kind and performance required to those in HPLC

  Typical sample of 10-30 l is injected rapidly as a plug of liquid and must not disturb the flow of the reagent stream

  Detectors: Atomic absorption, atomic emission, fluorometer, electrochemical system, spectrophotometer and photometer

  
• Diagram showing one channel of a peristaltic pump used in FIA
• Advantages of FIA


  • Higher analysis rate (100-300 sample/hr)

  Enhanced response time (less than 1 min between sample injection & detection)

  Low sample consumption: typically 50 to 200 microliters

  Low reagent consumption: typically 1ml per assay

  Much more rapid start-up and shut-down times (less than 5 min for each)

  Simpler and more flexible equipment
• Applications of FIA


  • Determination of Ca2+ in serum, milk and drinking water

  Determination of caffeine in drug preparation after extracting by chloroform and spectrophotometer as a detector

  Phosphate in waste water as well as in serum samples

  Blood profile in Biochemistry laboratory
• Application of FIA to determine PO4 in wastewater sample

  • Calibration graph and calculation of unknown sample concentration
• Application of analytical chemistry in medical laboratory
• Composition of blood
• Biochemistry laboratory
• Thermal Analysis or Thermal methods


  The physical property of a substance and or its reaction products is measured as a function of temperature

  The substance is subject to a controlled temperature programmed

  
• Application of Thermal Analysis

  • Polymers, pharmaceuticals, clays and mineral, metals and alloys
• Polymers


  Thermoplastics, elastomers (rubber) and thermosets (irreversible)
• Ceramic / Glass / Building Materials

  • Crystallized Glass Ceramic Panels - a unique glass building material, made by a highly sophisticated and specialized technique of crystallizing glass
• Thermal Analysis in Pharmaceutical and Cosmetic Industries


  • Thermal Analysis yields valuable information about the physical-chemical properties of materials
• Thermogravimetry (TG)


  The mass of a sample is measured as a function of temperature

  A plot of mass as a function of temperature is called a thermogram or a thermal decomposition curve

  
• Instrumentation of Thermogravimetry (TG)


  • Basic components: A sensitive analytical balance, a furnace, a purge gas system for inert or reactive atmosphere, a microcomputer for instrument control and data acquisition and display
• Thermobalance components
• The balance and furnace in TG

  • A small balance that can take up to 1 mg to 100 mg of sample (most common 5-20 mg)

  The furnace: Temperature range room temp. to 1600oC, Rate of heating 0.1 to 200 oC / min, Good insulation is essential to avoid heat transfer to sensitive balance, N2 or Ar is used to prevent oxidation of sample, Sometimes oxygen is applied to find oxidation reaction
• Thermogravimetry (TG) procedure


  The changes that occur to the weight of the sample as a function of temperature is recorded in a thermogram

  The temperature is carefully controlled using a computerized system

  
• Application of TG


  • Any process that undergoes decomposition and oxidation reaction

  Physical processes such as vaporizations, sublimation and desorption

  Most important application is the study of polymers where TG methods provide information about decomposition mechanisms for various polymeric pre
• Sample


  • Size range 5-20 mg
• Furnace


  • Isolated from other parts of the balance and the rest of the instrument
• Balance


  • Temperature range room temp. to 1600oC
  • Rate of heating 0.1 to 200 oC / min
  • Good insulation is essential to avoid heat transfer to sensitive balance
• Atmosphere


  • N2 or Ar is used to prevent oxidation of sample in some application
  • Sometimes oxygen is applied to find oxidation reaction
• Thermogravimetric analysis (TGA)


  1. Changes in weight of sample as a function of temperature are recorded in a thermogram

  2. Temperature is carefully controlled using a computerized system

  
• Thermogram


  Plot of the changes that occur to the weight of the sample as a function of temperature

  
• TGA method


  • Limited to any process that undergoes decomposition and oxidation reaction
  • Limited to physical processes such as vaporizations, sublimation and desorption
  • Most important application is the study of polymers
• Thermogram of polyethylene with carbon-black

  • 100-25=75%
• Thermogram of calcium oxalate decomposition

  1. CaC2O4.H2O(s) = CaC2O4(s) + H2O(v)

  2. CaC2O4(s) = CaCO3(s) + CO(g)

  3. CaCO3(s) = CaO(s) + CO2(g)
• Differential thermal analysis (DTA)


  Measures the difference in temperature between a substance and a reference material as a function of temperature