Quantitative and Instrumental Analysis in Chemistry
Quantitative and instrumental analysis is a branch of chemistry that deals with the quantitative determination of the composition of a sample of matter.
Key Points:
- Quantitative analysis is the determination of the amount (concentration) of a specified analyte in a sample.
- Instrumental analysis is the use of instruments to measure physical or chemical properties of a sample.
- Quantitative and instrumental analysis are used in a wide variety of fields, including chemistry, biology, environmental science, and medicine.
Main Concepts:
- Titration: A technique used to determine the concentration of an unknown solution by reacting it with a solution of known concentration.
- Spectrophotometry: A technique used to measure the amount of light absorbed by a sample at specific wavelengths.
- Chromatography: A technique used to separate the components of a mixture based on their different properties.
- Mass spectrometry: A technique used to measure the mass-to-charge ratio of ions.
Quantitative and instrumental analysis are essential tools for chemists and other scientists.
Quantitative and Instrumental Analysis Experiment: Spectrophotometric Determination of Iron in Food Samples
Objective:
To determine the concentration of iron in food samples using spectrophotometry, a technique that measures the absorbance of light by the sample.
Materials:
- Food samples (e.g., spinach, meat, or fortified cereal)
- 10-mL volumetric flask
- Spectrophotometer
- Cuvettes
- Iron standard solution
- 1,10-phenanthroline solution
- Ethanol
- Deionized water
Procedure:
1. Sample Preparation:
a. Weigh approximately 1 gram of the food sample and place it in a 10-mL volumetric flask.
b. Add 5 mL of ethanol to the flask and shake vigorously to dissolve the sample.
c. Add 1 mL of 1,10-phenanthroline solution and shake again.
d. Fill the volumetric flask to the 10-mL mark with deionized water and mix thoroughly.
2. Standard Solution Preparation:
a. Prepare a series of iron standard solutions with known concentrations (e.g., 0, 1, 2, 4, 6, and 8 ppm).
b. Pipette appropriate volumes of the standard solutions into a series of cuvettes.
3. Spectrophotometric Analysis:
a. Set the spectrophotometer to the wavelength of maximum absorbance for the iron-phenanthroline complex (typically around 510 nm).
b. Zero the spectrophotometer using a blank solution (prepared by following the same procedure without the food sample).
c. Place each cuvette containing the standard solutions and the sample solution in the spectrophotometer and measure the absorbance.
d. Plot a calibration curve by graphing the absorbance values vs. the corresponding iron concentrations of the standard solutions.
4. Iron concentration Calculation:
a. Determine the absorbance of the sample solution from the calibration curve.
b. Calculate the iron concentration in the sample using the following formula:
Iron concentration (ppm) = (Absorbance of sample / Absorbance of standard) * Concentration of standard
Significance:
- Spectrophotometry is a quantitative analytical technique that allows for the determination of the concentration of a substance in a sample by measuring the absorbance of light.
- This experiment demonstrates the practical application of spectrophotometry in determining the iron content in food samples, which is important for evaluating the nutritional value of foods and ensuring adequate dietary iron intake.
- Iron is an essential mineral for human health, playing a crucial role in oxygen transport, energy metabolism, and immune function.
- The experiment highlights the importance of quantitative analysis in various fields, including food chemistry, environmental science, and clinical chemistry.