Spectroscopy in Food analysis

Introduction

Atomic mass spectrometry (MS) is a powerful analytical technique used to identify and characterize organic and inorganic analytes in complex matrices such as food.

MS is based on the principle of mass-to-charge ratio (m/z) measurement of ionized analytes. The resulting mass spectra provide unique patterns of peaks that can be used for qualitative and quantitative analysis.

Basic Concepts of MS

• Ionization: The first step in MS is to convert the analyte into a gas and then into an ionized form. This is typically achieved using techniques such as electron impact (EI), chemical
  ionization (CI), or electrospray (ESI).
• Separation: Once ionized, the analytes are passed through a mass spectrometer, which separates them based on their m/z ratios. Various types of mass spectrometers are used for this purpose, including quadrupole, time-of-flight (TOF), and tandem mass spectrometry (MS/MS).
• Detection: The ions pass through a detector, which measures the relative abundances of ions of different m/z ratios. This information is then used to determine the structures and identities of the analytes.

Equipment and Techniques in MS

The major components of an MS system include the following:.

• Sample introduction system: The sample is introduced into the MS system through the introduction system.
• Vacuum system: The MS system operates at high vacuums to allow ions to travel through the system without collisions.
• Ionization system: The analytes are ionized in the mass spectrometer using various methods, including electron impact, chemical
  ionization, electrospray, and matrix-associated laceration using mass spectrometry (MALDI).
• Separation system: The ionized analytes are then passed through a mass filter to separate them based on their m/z ratios.
• Detection system: The filtered ions are then passed through a detector, which measures the relative abundances of ions of different m/z ratios.

Types of MS Experiments and Techniques

Different types of MS experiments and techniques are used for food analysis, depending on the specific analytes of interest and the desired level of information.

• Single quadrupole MS: Single quadrupole MS is the most common type of mass spectrometer, and it is used for basic qualitative and quantitative analysis.
• Triple quadrupole MS: Triple quadrupole MS is a more versatile type of mass spectrometer that can be used for both qualitative and quantitative analysis, as well as for selected reaction monitoring (SRM) experiments.
• Ion-trap MS: Ion-trap MS is a type of mass spectrometer that uses a radiofrequency (rf) quadrupole to store and manipulate ions, allowing for more complex experiments and increased analysis.
• Time-of-flight (TOF) MS: TOF MS is a type of mass spectrometer that measures the time it takes for ions to travel a certain distance, allowing for highly accurate mass measurements.
• Fourier Transform Ion : FTI MS is a high-resolution type of MS. It provides measurements of accurate mass based on the frequencies of ions in the cell that has a known dimension under controlled conditions.

Data Analysis and Interpretation

MS data is interpreted by analyzing the mass spectra and chromatograms generated by the instrument. The m/z ratios of the ions provide information about the chemical structures of the analytes, and the relative abundances of the ions provide information about their relative abundances in the sample.

For example, a mass-to-charge ratio (m/z) of 100.1026 can be assigned to a molecule with a chemical formula of C6H12O. Similarly, an m/z of 118.1077 can be assigned to a molecule with a chemical formula of C6H14O2. This process allows analysts to identify and list different chemical structures present in a sample.

Applications of MS in Food Analysis

MS has a wide range of applications in food analysis, including the following:

• Identification of food contaminants: MS can be used to identify a variety of food contaminants, such as pesticides, herbicides, and veterinary drugs.
• Detection of food allergens: MS can be used to identify and
  quantitate food allergens, such as peanut, milk, and egg.
• Characterization of food authenticity: MS can be used to characterize the authenticity of food products, such as by verifying the presence or absence of certain ingredients.
• Nutritional analysis: MS can be used to determine the nutritional composition of food products, such as the levels of vitamins,
  minerals, and fatty acid.
• Methanol analysis: MS can be used to measure the strength of high percentage of alcohol in wines and distilled sprits to help calculate the alcohol by volume (ABV).

Conclusion

MS is a powerful and versatile analytical technique that is essential for food analysis. MS can be used to identify and characterize organic and inorganic analytes in food, and it has a wide range of applications in food safety, quality control, and research.