Choosing the Right Reagent

Reagents are substances used to trigger a chemical reaction. They have numerous applications. In the medical field, for example, they are added to samples to carry out diagnostic tests or to detect the presence of certain substances in mixtures.
There are various types of reagents, and they come in many different forms, though most are either solid or liquid. The reactions they trigger are varied and specific to each reagent. This may correspond to a color change, release of gas, formation of a precipitate, etc.

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  • What are the different types of reagents?

    A distinction must be made between reactants and reagents. Reactants (or substrates) are consumed during the chemical reaction, while reagents are used to initiate the reaction or test whether it occurs. In other words, reactants are the elements we seek to identify or measure in a chemical reaction. Depending on the type of application, the same compound can be used as either a reagent or a reactant. Here are the main types of reagents:

    • Solvents
    • Catalysts
    • Acids
    • Bases (or hydroxides)
    • Alcohols

    Solvents are used to dilute or dissolve the reagents to obtain the reactive solution. Catalysts are used to speed up chemical reactions. In aqueous solutions, acids can donate one or more protons. Bases, on the other hand, can accept one or more protons in aqueous solutions. The pH of buffer solutions varies very little. Finally, alcohols are weak acids and are likely to donate a proton. They can be used as solvents or a fuel source, especially ethanol.

    Fujifilm buffer solution

  • What applications are reagents used for?

    Reagents are generally used in laboratories but are also available in kit form for use in the field. Their applications are numerous. These include:

    • Drug tests

    Reagents are the basic components of clinical test kits used to screen for various diseases (such as COVID-19) or pregnancy.

    In drug tests, the reagents are calibrated to react to the presence of a drug at a certain threshold. If the threshold is exceeded, the test result is positive. These tests can detect cannabis, opiates (heroin, morphine), cocaine, crack, amphetamines, etc. They are used in a variety of circumstances, mainly in roadside drug testing, road accidents or traffic offenses, doping control, or in-company drug testing.

    Reagents are also used in environmental analysis tests, particularly for water (clean water, wastewater, industrial sewage) and soil.

    They are also used to test pH, blood gas, and electrolyte levels.

    Reagents are used in food testing to determine the nutritional value and quality of certain foods or to detect contaminants, especially pesticides and heavy metals, in order to ensure food safety. These tests are carried out in the food, beverage, and agricultural sectors.

    RANDOX quality control reagent

    ERBA Diagnostics coagulation reagents

  • How do you evaluate and maintain the quality of a reagent?

    The quality of a reagent depends on its purity grade, packaging, and shelf life. These guarantee its chemical stability. Several factors can alter this chemical stability, such as temperature variations, humidity, microorganisms (bacteria), or exposure to light.

    • Purity: Reagents are classified according to their purity grade:
      • Chemically pure
      • Pure for analysis
      • Spectrally pure
      • Pure
      • Technical
    • Packaging: Reagents are packaged in vials, usually as solutions or powders. To reduce the risk of contamination, the vial should only be opened for a very short time, and the cap should be put back on immediately after use. You should never put any leftover reagent that has already been poured out back into the vial.
    • Shelf life: To ensure maximum shelf life, reagents should be stored in a cool (below 25°C), dry, dark place. Some need to be refrigerated. The expiration date is no longer valid once the vial has been opened, as air entering the vial can contaminate the product or otherwise compromise its stability.

    Reagent quality depends on:

    • Purity
    • Packaging
    • Shelf life
  • How are reagents stored?

    As we have stated, reagents generally need to be stored in a cool, dry, dark, and safe environment. Here are the main recommendations for correctly storing reagents:

    • Cold place: Temperature variations are detrimental to chemical stability. Care must also be taken with the storage temperature, as high temperatures can cause and accelerate dangerous chemical reactions. Laboratory or medical-grade refrigerators or freezers can be used to store reagents and prevent this.
    • Dry, dark place: Humidity and exposure to light can affect the chemical stability of reagents. We recommend storing them in closed cabinets, away from light and moisture.
    • Safe storage: Liquid and solid products that can produce dangerous reactions must be stored per occupational health and safety and fire prevention rules and regulations. For certain types of reagents, explosion-proof, fire-proof, and corrosion-proof cabinets should be used.
  • What are the dangers of using reagents?

    The dangers vary depending on the nature of the reagent, so it is advisable to always consult the safety data sheet of the reagent you are going to use. In general, these are the main risks that can arise from the incorrect use and storage of these products:

    • Burns or fires
    • Explosion
    • Corrosion
    • Poisoning
  • What precautions should be taken to avoid dangerous situations?

    To avoid dangerous situations, it is essential to have adequate safety systems and devices. These include:

    • Alarms
    • Fire extinguishing devices
    • Automatic switches
    • An updated manual of procedures with a view to adopting increasingly safe practices
    • Ventilation systems to evacuate airborne substances capable of reacting dangerously
    • Locks on reagent storage areas, with access restricted to qualified and authorized personnel only
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