Analytical Laboratory Techniques and Instrumentation
Overview
Analytical laboratory techniques and instrumentation are essential tools for chemists to identify, quantify, and characterize chemical substances. These techniques enable researchers to gain insights into the composition, structure, and properties of materials.
Key Concepts
Spectroscopy: Techniques that analyze the interaction of electromagnetic radiation with matter. Examples include UV-Vis spectroscopy, IR spectroscopy, and atomic spectroscopy. Chromatography: Techniques that separate components of a mixture based on their physical or chemical properties. Examples include gas chromatography (GC) and liquid chromatography (LC).
Electrochemical Methods: Techniques that measure electrical properties of solutions. Examples include potentiometry, voltammetry, and amperometry. Thermal Analysis: Techniques that investigate the thermal properties of materials. Examples include thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC).
* Microscopy: Techniques that visualize the structure and morphology of materials at various magnifications. Examples include light microscopy, electron microscopy, and scanning probe microscopy.
Instrumentation
Spectrometers: Instruments used for spectroscopy, such as UV-Vis spectrophotometers and IR spectrometers. Chromatographs: Instruments used for chromatography, such as GC systems and LC systems.
Electrochemical Analyzers: Instruments used for electrochemical methods, such as potentiostats and amperometric detectors. Thermal Analyzers: Instruments used for thermal analysis, such as TGA and DSC systems.
* Microscopes: Instruments used for microscopy, such as compound light microscopes, electron microscopes, and atomic force microscopes.
These techniques and instrumentation provide chemists with powerful tools to investigate the chemical world. They enable the development of new materials, the analysis of complex samples, and the understanding of fundamental chemical processes.
Experiment: Spectrophotometric Determination of Iron in Ore Sample
Objectives:
To determine the concentration of iron in an ore sample using spectrophotometry.Materials: Ore sample
Hydrochloric acid (HCl) Sodium dipotassium tetraoxalate (K2C2O4)
Potassium permanganate solution Phenanthroline solution
SpectrophotometerProcedure:Sample Preparation:*
1. Weigh approximately 0.5g of the ore sample into a crucible.
2. Heat the crucible in a muffle furnace at 550°C for 30 minutes to ash the sample.
3. Dissolve the ash in 10 mL of 1M HCl.
Iron Extraction:
1. Transfer the HCl solution containing the dissolved ash to a 50 mL volumetric flask.
2. Add 25 mL of 0.5M K2C2O4 solution and adjust the pH to 5.0 using NaOH or HCl as needed.
3. Boil the solution for 5 minutes to reduce Fe(III) to Fe(II).
4. Filter the solution into a clean 50 mL volumetric flask and dilute to the mark.
Color Development:
1. Transfer 10 mL of the filtered solution to a 25 mL volumetric flask.
2. Add 5 mL of phenanthroline solution and adjust the pH to 3.5.
3. Heat the solution in a boiling water bath for 30 minutes.
4. Cool the solution to room temperature.
5. Dilute to the mark with deionized water.
Spectrophotometric Analysis:
1. Set the spectrophotometer to a wavelength of 560 nm.
2. Zero the instrument with a blank solution (prepared by following steps 1-5 but without the ore sample).
3. Measure the absorbance of the sample solution.
Calculations:
1. Calculate the concentration of iron in the sample solution using Beer's law:
A = ε · c · l
where:
A = absorbance
ε = molar absorptivity
c = concentration
l = path length
2. Convert the concentration in the sample solution to the concentration in the ore sample using the following formula:
Concentration in ore sample (ppm) = (Concentration in solution (mg/L)) / (Weight of sample (g)) × 1000
Results:
The spectrophotometric analysis will provide a numerical value for the concentration of iron in the ore sample.
Significance:
This experiment demonstrates the use of spectrophotometry, a technique that measures the absorption of light by a sample to determine its concentration. It is widely used in analytical chemistry to quantify the presence of various substances in complex samples.