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Solution Chemical Analyses

ASL has the following water/solution analysis

  1. AA3 OPERATING PROCEDURE: FOR NH4+- AND NO3- NITROGEN IN WATER, WASTEWATER, SOIL EXTRACTS AND OTHER AQUEOUS SAMPLES
  2. PHOSPHATE IN WATER, WASTE WATER AND SOIL EXTRACTS AND OTHER AQUEOUS SAMPLES
  3. Water analysis by ICP-OES - includes Na, K, Ca, Mg, Fe, Mn, Zn, Cu, P, S, Cr, Mo, Pb, B, Al




AA3 OPERATING PROCEDURE: FOR NH4+- AND NO3- NITROGEN IN WATER, WASTEWATER, SOIL EXTRACTS AND OTHER AQUEOUS SAMPLES

Ammonium nitrogen

The sample is reacted with salicylate and dichloroisocyanuric acid to produce a blue compound measured at 660 nm. Nitroprusside is used as a catalyst. Alternative reagents are given for the reaction with salicylate or phenate. A dialyzer for the high range on MT7 eliminates interference from colored samples and suspended solids.

Nitrate/nitrite nitrogen

Nitrate is reduced to nitrite by hydrazine in alkaline solution, with copper catalyst, after which it is, following the DIN 38405 and ISO/DIS 13359 standard methods, reacted with sulfanilamide and NEDD to form a pink compound measured at 520 nm. Phosphoric acid is added at the final stage to reduce the pH, thus avoiding precipitation of calcium and magnesium hydroxide. The addition of zinc to the reducing agent suppresses the complexing of copper by organic material. A dialyzer for the high range on MT7 eliminates interference from colored samples and suspended solids.

Reagents for NH4-N and NO3-N (simultaneous analysis)

  • Ammonium channel (1)
    • Buffer
      1. 40 g of Tri-sodium citrate
      2. 1000 ml of DI water
      3. 1 ml of Brij-35

      Dissolve 40 g of tri-sodium citrate in about 600 ml DI water. Dilute to 1 liter with DI water. Mix thoroughly and add 1 ml Brij-35 solution. Prepare fresh weekly.

    • Sodium salicylate
      1. 40 g of Sodium salicylate
      2. 1000 ml of DI water
      3. 1g of Sodium nitroprusside

      Dissolve 40 g of sodium salicylate in about 600 ml of DI water. Add 1 g sodium nitroprusside, dilute to 1 liter with DI water and mix thoroughly. Prepare fresh weekly.

    • Dichloro-isocyanuric acid (DCI)
      1. 20 g of Sodium hydroxide
      2. 1000 ml of DI water
      3. 3g of Dichloro-isocyanuric acid sodium salt dihydrate

      Dissolve 20 g sodium hydroxide and 3 g dichloro-isocyanuric acid in about 600 ml of DI water. Mix thoroughly and dilute to 1 liter with DI water.

    • Dilution water and System wash solution
    • If using a dilution loop, use degassed water containing 2 ml/L brij-35, Triton X-100. Aerosol 22, or 2 g/L sodium dodecyl sulfate.

      If this method is used together with a phosphate method, do not use Brij-35 or Triton X-100 in the dilution water, as these interfere with molybdate-based methods.

    • Sampler wash solution
    • Use pure water without surfactant. If analyzing soil extracts or other samples not dissolved in pure water use the sample matrix solution (e.g. 2N KCl, 0.01 M CaCl2) as the sampler wash solution.

    • Stock Ammonium standard, 1000 mg/L as N
      1. 4.717 g of Ammonium sulfate
      2. 1000 ml of DI water

      Dissolve 4.717 g potassium nitrate in about 600 ml DI water. Dilute to 1 liter with DI water.

      Prepare working standards as required. If analyzing soil extracts or other samples not dissolved in pure water, dilute the working standards with the sample matrix solution.

  • Nitrate/nitrite channel (2)
    • Dilution water and System wash solution
      1. 2ml of Brij-35
      2. 1000 ml of DI water

      Add 2 ml of Brij-35 to one liter of DI water and mix thoroughly.

    • Stock Copper sulfate
      1. 1g of Cupric sulfate
      2. 1000 ml of DI water

      Dissolve 1 g of cupric sulfate in about 600 ml of DI water. Dilute to one liter and mix thoroughly.

    • Stock Zinc sulfate
      1. 10g of Zinc sulfate
      2. 1000 ml of DI water

      Dissolve 10 g of Zinc sulfate in about 600 ml of DI water. Dilute to one liter and mix thoroughly.

    • Color Reagent
      1. 10g of Sulfanilamide
      2. 0.5g N-1-Naphthyethylenediamine di-HCl (NEDD)
      3. 100ml Ortho-phosphoric acid
      4. 1000 ml of DI water

      Dissolve 10 g of sulfanilamide in about 600 ml of DI water. Add 0.5 g of NEDD and mix thoroughly. Add the phosphoric acid. Dilute to 1 liter with DI water and store in a dark bottle. Prepare fresh weekly, or if reagent absorbance exceeds 0.1 AU.

    • Sodium Hydroxide (NaOH) - for water and waste water analysis
      1. 10g of Sodium hydroxide
      2. 3ml of Ortho-phosphoric acid
      3. 1ml of Brij-35 (30% solution)
      4. 1000 ml of DI water

      Dissolve 10 g of sodium hydroxide in about 600 ml of DI water. Cautiously add 3 ml of ortho-phosphoric acid and mix thoroughly. Dilute to one liter with DI water and add 1 ml of Brij-35 solution.

    • Hydrazine sulfate - for water and waste water analysis
      1. 10ml of Stock copper sulfate
      2. 10ml of Stock zinc sulfate
      3. 2g of Hydrazine sulfate
      4. 1000 ml of DI water

      Add 10 ml of stock copper sulfate, 10 ml of stock zinc sulfate and 2 g of hydrazine sulfate to 600 ml of DI water. Dilute to one with DI water and mix thoroughly.

    • Sodium Hydroxide (NaOH) - only for SOIL EXTRACTS
      1. 40g of Sodium hydroxide
      2. 1ml of Brij-35 (30% solution)
      3. 1000 ml of DI water

      Dissolve 40 g of sodium hydroxide in about 600 ml of DI water and mix thoroughly. Dilute to one liter with DI water and add 1 ml of Brij-35 solution.

    • Hydrazine sulfate - only for SOIL EXTRACTS
      1. 14ml of Stock copper sulfate
      2. 10ml of Stock zinc sulfate
      3. 6g of Hydrazine sulfate
      4. 1000 ml of DI water

      Add 14 ml of stock copper sulfate, 10 ml of stock zinc sulfate and 6 g of hydrazine sulfate to 600 ml of DI water. Dilute to one with DI water and mix thoroughly.

    • Phosphoric acid - only for SOIL EXTRACTS
      1. 3ml of Ortho-phosphoric acid
      2. 4g of Tetra-sodium-diphosphate x 10 H2O
      3. 1ml of Brij-35 (30% solution)
      4. 1000 ml of DI water

      Cautiously add 3 ml of ortho-phosphoric acid in about 600 ml of DI water and mix thoroughly. Dissolve 4 g of tetra-sodium-diphosphate decahydrate and mix thoroughly. Dilute to one liter with DI water and add 1 ml of Brij-35 solution.

    • Stock Nitrate Standard, 1000 mg/L N
      1. 7.218g of Potassium nitrate
      2. 1000 ml of DI water

      Dissolve 7.218 g potassium nitrate in about 600 ml DI water. Dilute to 1 liter with DI water.

      Prepare working standards as required. If analyzing soil extracts or other samples not dissolved in pure water, dilute the working standards with the sample matrix solution. Dilute to one liter with DI water and add 1 ml of Brij-35 solution.

    • Stock Nitrite Standard, 1000 mg/L N
      1. 4.930g of Sodium nitrite
      2. 1000 ml of DI water

      Dissolve 4.930 g sodium nitrite in about 600 ml DI water. Dilute to 1 liter with DI water.

      Prepare working standards as required. If analyzing soil extracts or other samples not dissolved in pure water, dilute the working standards with the sample matrix solution.

Interferences

Low-molecular amines react similarly to ammonia and will consequently lead to erroneously high results.

Interferences may occur if the reaction mixture after addition of all reagent solutions does not reach a pH of at least 12.6. This mainly happens with strong acidic and buffered samples. Strongly acidic or alkaline samples must be neutralized approximately prior to analysis.

Metal ions in high concentrations, which precipitate as hydroxides, may cause poor reproducibility.

For complete removal of the interfering organic matrix (compounds with high molecular weights) the sample may be dialyzed. Alternatively, the sample may be filtered through activated carbon, provided a change of the ammonium concentration in the sample can be ruled out when this approach is chosen.

Samples containing particles > 0.1 mm must be filtered.

For nitrates, samples with particulate matter > 1 mm must be removed by membrane filtration. The sample may be filtered through activated carbon, provided changes of the nitrate or nitrite concentration in the sample can be ruled out. Dilute samples with a total salt concentration of > 30 g/L prior to measurement.

Reference:

Bran + Luebbe. Auto Analyzer 3 Applications. Method nos. G-109-94 and G-102-93.


PHOSPHATE IN WATER, WASTE WATER AND SOIL EXTRACTS AND OTHER AQUEOUS SAMPLES

Ortho-phosphate reacts with molybdate and ascorbic acid to form a blue compound measured at 660 nm. Antimony potassium tartrate is used as a catalyst.
A dialyzer for the high range on MT7 eliminates interference from coloured samples and suspended solids.
This method is a multitest with alkalinity (methyl orange), ammonia (salicylate and phenate), boron, calcium, chloride, hydrogen sulfide, iron, nitrate, nitrite, TKN, TKP, potassium, sodium, silicate.




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