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Flow injection Batch analysis
Experiments Overview

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FIA peristaltic pump, Injection valve, 1 ml grad. syringes, Eppendorf pipette, Flow-cell, UV-VIS spectrophotometer, recorder.


Pump tubing 2.75 mm id, PTFE tubing 0.8 mm id, test tubes 10 ml, test tube rack, 50 ml volumetric flasks.


Potassium dihydrogen orthophosphate, (KH2PO4) FW = 136.09
Di sodium hydrogen phosphate (Na2 HPO4) FW = 141.96
Potassium antimony tartrate, FW = 324.92
Ammonium molybdate, (ammonium molybdate(V1)tetrahydrate, FW = 1235.86
Ascorbic acid, FW = 176.12
Sulphuric acid.

1.0g of a phosphate salt sample: disodium hydrogen phosphate (Na2HPO4 FW = 141.96)  or
Fertilizer sample (0.1 g)

Solutions Preparation

  • 50 ppm stock phosphate solution: dilute from 1000 ppm stock prepared as follows: weigh out accurately 1.43 g of dried KH2PO4 and dissolve in one liter distilled water. Pipette 2.5 mls into a 50 ml volumetric flask and make up to the mark with distilled water.
  • Soln. A = potassium antimony tartrate: 1.3715 g in 50ml distilled water.
  • Soln. B = ammonium molybdate: 10 g in 250 ml distilled water.
  • Soln. C = ascorbic acid: 1.76 g in 100 ml distilled water (prepare fresh daily)
  • Soln. D = 5N sulphuric acid: 35 ml to 250 ml distilled water.
Mixed reagent (mix fresh daily):

50ml D + 5ml A + 15ml B + 30ml C

Analytical notes:

  • All glassware used in this experiment must be acid washed (1 % nitric acid bath) and dried throughly (glassware oven) before use!
  • Use eppendorf pipette with plastic tips to measure exactly 0.8 mls of mixed reagent.
  • Color development: color develops fully within an hour. There is no need to leave samples and standards overnight for color development.
  • 50 ppm phosphate standard: dry salt in oven @ 80°C, cool in desiccator and then weigh out the required amount.
  • Sample: weigh out 1.00g of salt in triplicate in 100 ml volume solutions. Dilution is x 100 ( dilute 0.50ml in 50ml volumetric flask)
  • Measure @ 830 nm or 825 nm.
  • Blank: 5ml distilled water and 0.8ml mixed reagent.
  • Pump: flow rate of distilled water = 5ml per minute (Pump setting = 500)
  • Tubing: single piece pump tubing = 2.75 mm id. for distilled water.
    Injector loop: 60cm x 0.8mm id PTFE tubing.
    Manifold loop: 30cm x 0.8 mm id PTFE tubing from injector to flow cell.
Operation of instrument:

Follow User guide or get help from Technician or Demonstrator

delloyd infolab