Citric Acid

Chemical Name

  • Citric acid
  • Trisodium salt dihydrate
  • Trisodium citrate dihydrate

IUPAC / CAS

2- hydroxypropane -1,2,3 - tricarboxylic acid / 6132 – 04 - 03

Physical and Chemical Properties

Citric acid is available as white crystals at room temperature and atmospheric pressure. It is a colorless and odorless chemical agent, naturally found in many fruits and vegetables. The three carboxyl groups (COOH) contribute to its property of being acidic in nature. The citrate ion is an excellent buffer for controlling the pH of acidic solutions. Citric acid is naturally present in almost all forms of life. The excess citric acid is readily metabolized and eliminated from the body.

Mode of Action

Citric acid shows an unexpected ability to enhance the antimicrobial power of a wide range of disinfectants and antibiotic agents. 1 % citrate greatly enhances the ability of antibiotics to kill or inhibit a wide range of bacterial species including antibiotic resistant strains. Citrate alone is effective in preventing bacterial growth in platelet concentrates and in red blood cell suspensions.  Besides enhancing the power of antibiotics, citrate also enhances the antimicrobial properties of disinfectant organic dyes such as crystal violet and methylene blue.  Citrate also enhances the antimicrobial properties of polyphenols of plant origin. Iodine-based disinfectants are also enhanced without enhancing protein denaturation. As citric acid gives away protons in solution, there is a decrease in the pH of the solution, which directly co-relates with the antimicrobial properties of the biocide agent. The main effect is due to the prevention of absorption of essential nutrients by the microorganisms due to disruption of the protein motive force, which provides energy for active absorption of nutrients. It alters the permeability of cell wall causing damage and hence cell death, especially in gram negative bacteria. It is also capable of chelating metal ions present in the cell wall thereby causing damage.

Respiratory infections

Majority of the respiratory infections caused by adenovirus are asymptomatic. Adenovirus type 7 is known to cause a fulminant bronchiolitis and pneumonia. Cough, fever, sore throat and runny nose are common presenting symptoms of adenovirus infections. Physical findings are often correlated with the symptoms of the patient. Serotypes 4 & 7 are associated with features of atypical pneumonia where the physical findings may not match the findings of the roentgenogram. 

Activity Spectrum

This is a characteristic syndrome in children which is attributed to adenoviruses. It is characterized by fever (38 ° C), pharyngitis, rhinitis, conjunctivitis and cervical adenitis. The symptoms persist for 3 to 5 days. Complications are rare and several studies have identified serotype 3 to be the most commonly involved organism. Contaminated swimming pools and ponds are known to be the source of infection.   

Advantages

  • Noncarcinogenic to humans
  • Environmentally safe
  • Citric acid is a weak organic acid that is used as a cleaning agent and as an oxidant.
  • It is extensively used as a flavoring agent and preservative in the food industry (denoted as E330). When added to ice-cream it keeps the fat globules separate.
  • It is an excellent buffer and hence used as a buffering agent in pharmaceuticals and household cleaners.
  • The property of chelating metals helps in softening water and producing foam and hence it is extensively used in the laundry industry.

Disadvantages

  • Citric acid causes irritation to the skin and the mucous membranes.
  • Does not have broad effective spectrum of activity, hence used with other disinfectants 

Ease of Use

Citric acid is an environmentally friendly preservative, extensively used in the food industry. It decomposes above 170° C by giving out carbon dioxide and water.

Regulatory Information

Citric acid is recognized as safe for use in food by all major national and international food regulatory agencies. IARC has classified citric acid as a class 3 agent. Citric acid also figures on the European Inventory of Existing Chemical Substances (EINECS). The European Community Directive 67/548/EEC has labeled citric acid as follows:

  • Xi – Irritant
  • R36 – Irritant to the eyes 

  • S26 – In case of contact with eyes, immediately rinse with plenty of water and seek medical advice

Safety Measures

  • Contact with dry citric acid or with concentrated solutions can result in skin and eye irritation, so protective clothing should be worn when handling these materials
  • Keep away from heat and ignition sources.
  • Keep away from oxidizers, reducing agents, acids and alkalis
  • Store in a cool dry, well ventilated area in a tightly closed container.
  • Engineering controls: Use local exhaust ventilation and process enclosures to keep airborne particles within the recommended exposure limits
  • Avoid breathing any dust, vapors, mist or gas as it causes irritation to the mucous membranes.

First Aid Treatment

  • Eye contact: Immediately wash the eyes with splashes of cold water at the eyewash station for 15 mins. A medical examination must be done inorder to assess the extent of injury.
  • Skin contact: Discard any clothes on the site of skin contact and wash the part with soap and water for 15 minutes.
  • Fire: In case of a fire, wear fireproof clothes with a self contained breathing apparatus. Open all the windows to allow good ventilation.
  • Ingestion: Wash the mouth thoroughly with water, a gastric lavage may be helpful if ingested in large quantities . Refer the patient for medical examination
  • Inhalation: Remove the victim from the source into an area with fresh air. If unable to breathe respiratory support must be given to the patient. Medical supervision may be required to prevent complications.