por What are laboratory reagents?
The laboratory reagents they are chemical substances of diverse nature and composition that help the bioanalyst to carry out a series of reactions, involved with the determination of a wide variety of clinical tests.
The reagents can be, according to their physical state, solid, liquid or gaseous, and according to their chemical nature, acids, bases, salts, alcohols, aldehydes, among others. All areas of a clinical laboratory require various reagents, which differ from each other.
Reagents can be purchased ready to use. Some must be reconstituted, others must be prepared from the primary reagent mix. They can also be prepared with a simple dilution.
The function of each will depend on the analysis that you want to perform. For this, there are specific protocols that the analyst must follow carefully.
The handling and safeguarding of laboratory reagents must follow standards established by the institution, to guarantee the safety of the worker and their proper conservation. Therefore, it is recommended that the reagents be stored according to the risk category established by government regulations.
By taking into account the risks and putting biosafety regulations into practice, accidents at work are avoided.
Classification of reagents according to the degree of danger
There are at least 5 systems that classify the reagents, according to the degree of danger they possess. These systems are those proposed by:
The United States Environmental Protection Agency (EPA).
The US Department of Occupational Safety and Health (OSHA).
The European Community (EC).
The IMDG Code (International Maritime Dangerous Goods Code).
The United Nations Organization (UN).
In general, and coupled with what the EPA proposes, they can be classified as highly dangerous and dangerous.
highly dangerous reagents
They are those that can cause death in humans in very low amounts or that present a lethal dose in rats equal to LD50.
dangerous reagents
They are sub-classified as flammable, corrosive, explosive and toxic.
flammable substances
This category includes all reagents that contain more than 24% alcohol in solution in their composition or that have a flash point below 60 °C.
Also included in this category are all materials that can easily cause fire by friction or by spontaneous chemical modifications or accumulation of their gases.
Likewise, those that when they come into contact with fire are energetically incinerated, and oxidizing reagents, such as chlorates, nitrates, manganates and inorganic peroxides.
Toxic substances
Toxic reagents can be sub-divided into irritant, anesthetic, asphyxiant, nephrotoxic, hepatotoxic, neurotoxic, and carcinogenic.
corrosive substances
Strong acids and bases fall into this category, that is, those that have a pH below 2.1 and above 12.4. These substances are so caustic that they can corrode steel.
Any trace of these reagents can react with other residues and form toxic compounds capable of endangering the integrity of workers. These reagents must be kept away from the rest.
reactive substances
They are reagents that react violently when combined with water, acids, or bases, generating smoke, vapors, or gases. This is how reagents containing sulfur or cyanides in their composition react.
explosive substances
They are substances capable of producing an explosion at 25 °C at a pressure of 1.03 kg/cm2. This is because they have an explosive constant equal to or greater than that of dinitrobenzene.
Preparation of reagents
In general, the reagents should be prepared as follows:
Preparation of reagents from solid solutes
According to the technique, the precise grams are weighed on a scale.
The solid solutes are placed in a beaker and a little of the solvent indicated by the technique is added to them, usually water is used.
If necessary, the mixture is heated to help dissolution, as long as the technique so indicates.
It should be allowed to cool before transferring to the volumetric flask.
Use funnel for transfer.
Wash the beaker with a little of the solvent being used and add it to the flask.
Make up to the mark with the same diluent.
Transfer to a clean and dry bottle, properly label and store according to the reagent specifications.
Preparation of reagents from liquid solutes
The corresponding milliliters are measured with a serological or volumetric pipet.
Do not pipet directly with the mouth.
Use propipette. Take care that the pipette does not fill with bubbles.
To do this, before sucking, you have to make sure that the pipette is inserted to the bottom of the bottle and that it will continue like this even after you finish sucking.
Place the measured milliliters in a volumetric flask, make up to the mark with the diluent.
The flask can be stoppered and inverted several times to mix.
Transfer to a clean and dry container.
Reagent Filtration
Some reagents need to be filtered, for this purpose filter paper funnels are used.
A smooth funnel is used if the precipitate is to be recovered or a pleated funnel if the precipitate is not of interest.
Transfer of solid reagents
A clean, dry spatula is used to collect small amounts of solid reagents.
If the quantity is a little larger, a folded piece of paper can be used to help slide the reagent into the other container.
Transfer of liquid reagents
In the transfer of highly corrosive liquids, spills and splashes must be avoided.
For this, a funnel is used and a glass rod is placed through which the liquid to be transferred will be made to slide.
If the reagent emits vapors, work under an extraction hood and use the necessary safety equipment (gloves, face mask or mask, safety glasses, gown).
If an extraction hood is not available, work in a well-ventilated area.
Considerations after preparing the reagents
The reagents, after their preparation, should be packed in airtight containers, preferably amber in color.
Newly prepared reagents must be well labeled with indelible ink, including the name of the reagent, preparation date, expiration date, and the type of risk it presents (by inhalation, ingestion, or contact).
Storage temperature is also important, the prepared reagent must be placed at the proper storage temperature. Some can be stored at room temperature, but others require refrigeration.
Safe handling of reagents
The reagents must be handled with care, preventing the inhalation of vapors, direct contact with skin or mucous membranes, and accidental ingestion. To do this, biosecurity measures must be taken, such as the use of face masks, masks, gloves, safety glasses, and a laboratory coat.
All these elements protect the person handling the reagents. Not all reagents emit vapors or are corrosive, so you have to learn to know them.
Before handling a reagent, the bottle label must be checked and the safety pictograms must be observed. This will guide on the preventive measures that must be taken. This will prevent possible accidents.
Reagents classified as flammable cannot be handled near a burning burner or burner.
Reagent labels should always be placed on the bottle, never on the lid. Bottle caps should not be interchanged or placed on the table: they should be held with the fingers while handling the reagent.
Do not return the excess reagent taken to the original bottle, this can contaminate it.
If the reagent is corrosive or toxic, it should never be pipetted by mouth, a propipette should always be used. For safety in the bacteriology area, a piece of cotton should be placed on top of the pipettes. In case of accidents, the cotton serves as a barrier.
When you want to dilute reagents such as strong acids, for example, concentrated sulfuric acid or concentrated hydrochloric acid, it must be taken into account that water will never be placed directly on them, but rather the opposite: the acid will slowly be incorporated into the water, manipulating everything in security bell.
The work table must always be kept clean and dry. In case of spills or fire, do not try to solve the incident with water.
reagent storage
The labels of the vials have a colored stripe that indicates which group it is from: red stripe, flammable, white, corrosive, yellow, reactive, blue, health risk, green, low risk, striped, white and red or white and mismatched black.
Items from the same group can usually go together and each group must be separated from each other. However, there are reagents that, even though they are from the same group, are incompatible with each other: they must be separated. Check the label for incompatibilities.
Acids and bases should never be stored together, likewise, flammable, corrosive, oxidizing, and peroxide reagents should be kept as far apart as possible from each other (separate shelves).
Corrosive reagents should be at the bottom of the shelf and the most harmless at the top. The tall jars go at the top at the back of the shelf and the small ones at the front. Highly dangerous reagents require safety cabinets.
Finally, the MSDS (Material Safety Data Sheets) for each reagent should always be read before handling.
Final disposal of chemical waste
The use of reagents generates waste materials that must be disposed of in a way that affects the environment as little as possible.
Most used reagents in a clinical laboratory, composition and function
References
Management of chemical reagents. Safety tips. Retrieved from handling_of_reagents.
Baeza J. Preparation of solutions and their assessment. Retrieved from prior.uclm.es.
Reagent Storage. Retrieved from arlsura.com-reactivos_cistema.
chemical reagents. Recovered from vet.unicen.edu.ar.