Xác Định Photphat Bằng Phép Đo Màu

Đo hàm lượng photphat trong nước bằng phương pháp xanh molybden

Colorimetry Advanced (University) 90 phút ~$15,00

Mục tiêu

Xác định nồng độ photphat trong mẫu nước bằng phương pháp đo màu amoni molybdat.

Bối cảnh

The molybdenum blue method is the standard technique for phosphate determination in environmental water analysis. Phosphate ions react with ammonium molybdate in acidic solution to form a phosphomolybdate complex, which is then reduced by ascorbic acid to form an intensely blue colored complex (molybdenum blue). The intensity of the blue color is proportional to phosphate concentration. This method can detect phosphate at concentrations as low as 0.01 mg/L.

Cảnh báo an toàn

  • Ammonium molybdate solution contains sulfuric acid — corrosive
  • Antimony compounds are toxic
  • Use pipette fillers — never mouth-pipette
  • Dispose of molybdate waste in heavy metal waste container

PPE cần thiết

goggles gloves lab_coat

Vật liệu

  • Potassium dihydrogen phosphate (KH₂PO₄) (1 g)
    For stock standard
  • Ammonium molybdate solution (100 mL)
    2.5% in 5M H₂SO₄
  • Ascorbic acid solution (50 mL)
    1% freshly prepared
  • Antimony potassium tartrate (10 mL)
    Catalyst solution
  • Environmental water sample (100 mL)
    Pond, river, or tap water
  • Distilled water (500 mL)

Thiết bị

Spectrophotometer Cuvettes (1 cm path length) Volumetric flasks (50 mL, 8 total) Pipettes (1 mL, 5 mL, 10 mL) Water bath (37°C)

Quy trình

1

Prepare a 100 ppm phosphate stock solution by dissolving 0.1433 g KH₂PO₄ in distilled water and making up to 1 L. Then prepare working standards: 0, 0.1, 0.2, 0.5, 1.0, 2.0 ppm.

15 phút
2

Prepare the combined reagent: mix 50 mL ammonium molybdate solution, 5 mL antimony potassium tartrate solution, and 30 mL ascorbic acid solution. Use within 4 hours.

10 phút Handle acid carefully
3

To each 50 mL standard flask and the water sample, add 8 mL of combined reagent. Mix well.

10 phút
4

Allow color development for 10 minutes at room temperature (or 5 minutes in 37°C water bath).

10 phút
5

Measure absorbance at 880 nm (or 710 nm if 880 nm is not available). Zero with the blank.

15 phút
6

Plot the calibration curve. Determine the phosphate concentration of the water sample.

15 phút
7

Evaluate the result against environmental standards. Phosphate above 0.02 mg/L may indicate eutrophication risk.

15 phút

Kết quả dự kiến

The calibration curve should be linear in the 0–2 ppm range. The blue color deepens with increasing phosphate. Environmental samples typically show 0.01–0.5 ppm in clean water, higher in agricultural runoff areas.

Dọn dẹp

Collect all molybdate-containing solutions in labeled waste. Rinse all volumetric glassware. Clean cuvettes immediately.

Chi tiết

Danh mục
Colorimetry
Độ khó
Advanced (University)
Thời gian
90 phút
Chi phí ước tính
$15,00
Số bước
7
Vật liệu
6

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Frequently Asked Questions

What is the objective of Xác Định Photphat Bằng Phép Đo Màu?
Xác định nồng độ photphat trong mẫu nước bằng phương pháp đo màu amoni molybdat.
How difficult is Xác Định Photphat Bằng Phép Đo Màu?
This experiment is rated as Advanced (University). It takes approximately 90 minutes to complete.
What safety precautions are needed for Xác Định Photphat Bằng Phép Đo Màu?
Key safety precautions include: Ammonium molybdate solution contains sulfuric acid — corrosive; Antimony compounds are toxic; Use pipette fillers — never mouth-pipette.
What materials are needed for Xác Định Photphat Bằng Phép Đo Màu?
The main materials required are: Potassium dihydrogen phosphate (KH₂PO₄), Ammonium molybdate solution, Ascorbic acid solution, Antimony potassium tartrate, Environmental water sample.
What results should I expect from Xác Định Photphat Bằng Phép Đo Màu?
The calibration curve should be linear in the 0–2 ppm range. The blue color deepens with increasing phosphate. Environmental samples typically show 0.01–0.5 ppm in clean water, higher in agricultural runoff areas.