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Instrumental Analysis for Salts

  • Instruments like colorimeters and UV-visible spectrophotometers provide modern methods to analyze salts, offering speed and accuracy.

Spectroscopy

  • Light is electromagnetic radiation, with visible light being a part of the electromagnetic spectrum (400 to 700 nm).

  • Spectroscopy uses light to interact with materials for analytical purposes.

  • Absorbed visible light results in observed colors that represent complementary colors.

Colorimeters and UV-Visible Spectrophotometers

  • Colorimeters measure color intensity to determine concentration using absorbance.

  • UV-visible spectrophotometers use monochromators to select precise wavelengths and also measure absorbance across UV/visible range.

Colorimetry Technique

  1. Measure absorbance of standard solutions.

  2. Prepare calibration curves (absorbance vs. concentration).

  3. Determine unknown concentration from standard curve.

  4. Account for any dilutions made during preparation.

Calibration Curve

  • Plotting standard solution absorbances allows determination of unknown concentrations.

  • Absorbance values range from 0.00 to 1.00.

Salt Extraction from Soil

  • Soil analysis includes:

    1. Weigh dried soil sample.

    2. Use liquid to extract salts.

    3. Filter solids and dilute the extract.

    4. Analyze using spectroscopy.

    5. Calculate concentration per gram of soil using:
      \text{Concentration} = \frac{\text{Concentration of salt in extract} \times \text{Volume of extract}}{\text{Mass of dried soil}}.

Applications of Colorimetry and UV-Visible Spectroscopy

  • Used for measuring various substances such as blood sugar, cholesterol, heavy metals, etc.

  • Portable options are available for field testing, while laboratory models offer higher sensitivity.

Flow Injection Analysis (FIA)

  • FIA is suitable for large sample volumes and multiple analyses.

  • Procedure involves:

    1. Pumping standards/samples into an injection port.

    2. Mixing with reagents to create colored solutions.

    3. Recording absorbances at specific wavelengths.

Conclusion

  • Colorimetric and UV-visible techniques are vital in quantitative analysis in environmental science and health monitoring.