EXPERIMENT 3: IDENTIFICATION TEST FOR ATROPINE SULFATE USING INFRARED SPECTROSCOPY

SPECTROSCOPY

Interaction between matter & electromagnetic radiation (EMR)

SPECTROSCOPY

main purpose

identify & analyze a molecule based on their interaction with EMR

Infrared (IR) Spectroscopy

• a technique in analytical chemistry that measures interactions between matter and the infrared portion of the electromagnetic spectrum

FT-IR

• Fourier Transform Infrared Spectroscopy

• collects IR spectra

• use mathematical frontier transform to convert the raw data (from the IR) into a spectrum that’s readable to the analyst

MID-IR SPECTROSCOPY

• A specific range of infrared spectroscopy that focuses on the mid-infrared region of the electromagnetic spectrum 

MID-IR SPECTROSCOPY

used to 

• analyze the molecular vibrations and chemical bonds of compounds, particularly in the mid-infrared range, which is approximately 4000 to 400 cm^-1 (wavenumbers)

MID-IR SPECTRUM

• Displays absorption bands at different frequencies, representing the vibrational modes of the sample’s chemical bonds 

MID-IR SPECTRUM

• The positions and intensities of these bands are

characteristic of the functional groups present in the compound, allowing for the identification and structural analysis 

Applications

• chemical identification

• quality control

• environmental monitoring

• forensic analysis

• material characterization

CHEMICAL IDENTIFICATION

• Mid-IR spectra serves as unique “fingerprints” for compounds, enabling differentiation between similar compounds

• Look at functional groups present in the compounds

QUALITY CONTROL

• Widely used in industries such as pharmaceuticals, food, and polymers for product composition and to ensure product quality and consistency  

• detect presence of adulterants in our product (via presence of different peaks in the reading)

ENVIRONMENTAL MONITORING

• Mid-IR spectroscopy is applied in the detection of pollutants and environmental contaminants e.g., in air and water

• toxic metals in our material (usually in water)

FORENSIC ANALYSIS

• It can be applied in forensic investigations to identify unknown substances found at crime scenes

MATERIAL CHARACTERIZATION

Mid-IR spectroscopy aids in analyzing the composition and properties of various materials, including solids, liquids, and gases

SAMPLE

• Thin Film

• Mixing it with an infrared-transparent matrix (solid)

• Using specialized cells or cuvettes (liquid)

3000-4000:

Bonds to Hydrogen

Alcohol

Amide

Hydrocarbon

2000-3000:

Triple Bonds

1500-2000:

Double Bonds

1000-1500:

Single Bonds

SP3 would be

below 3000

SP2 would be

above 3000

<197A>

The substance under examination is intimately in contact with an internal reflection element for attenuated total reflection (ATR) analysis.

ACCEPTANCE CRITERIA

• The IR spectrum of the preparation of the sample exhibits maxima only at the same wavenumbers as that of the appropriately prepared corresponding USP Reference Standard

MID-INFRARED SPECTROSCOPY

provide _

• valuable insights into the molecular composition and structure of various substances

MID-IR REGION

• of great interest because it corresponds to the fundamental vibrational frequencies of many chemical bonds

When infrared light in this range interacts with a sample,

it is absorbed by the compound's specific vibrational modes, producing characteristic absorption bands in the mid-IR spectrum. 

• When infrared light in this range interacts with a sample, it is absorbed by the compound's specific vibrational modes, producing characteristic absorption bands in the mid-IR spectrum. 

  • These absorption bands _

provide valuable information for identifying and analyzing the structure of various compounds.

Principle

• similar to that of general infrared spectroscopy

• When infrared light passes through a sample, it interacts with the compound's molecules, causing specific vibrational modes to absorb energy at specific frequencies.

mid-IR light source

• e.g., a globar (a heated silicon carbide rod) or a Fourier transform infrared (FT-IR) spectrometer with a built-in infrared light source

• emits a broad spectrum of mid-infrared light

monochromator

• or interferometer

• selects specific wavelengths for analysis

holder

• or cell

• where the sample is placed

detector

records the intensity of transmitted or absorbed light

Sample Preparation

• Create a thin film, mix it with an infrared-transparent matrix, or use specialized cells or cuvettes.

• Expose the sample to mid-IR light, and the instrument measures the transmitted or absorbed light, producing an infrared spectrum.