Preservatives Used for different poisoning samples

Poisons/Toxins are often involved in homicidal, accidental or suicidal deaths. The examination and detection of different types of poisons and their identification is a significant part of forensic science and it is studied in forensic toxicology, a branch of forensic science. The investigation of cases of poisoning is one of the most difficult tasks and preservation of viscera or biological evidences is even more problematic. Here we are going to know about preservatives used for the conservation of viscera, and which part of body should be collected, etc.

Under the following circumstances, viscera are required to be preserved:

  • In cases of homicide, suspicious or sudden death.
  • In cases of death due to suspected poisoning.
  • In cases of obscured autopsy.
  • In cases of death due to hanging or drowning.
  • In cases of death due to burn, if the patient died within 48 hours after receipt of the injury.

What should be collect in different types of scenario?

In Case of Criminal abortion: Vagina, cervix and uterus with adnexa and the contents.

In case of Firearm injuries: Skin around the entrance wounds.

For Microbiological investigations

  • Blood from the heart.
  • Smears from the throat.
  • Swabs from abscess cavities.
  • Fluid from cysts etc.

Preservation of Viscera

  • Stomach and its contents
  • 30 cm small Interline and contents
  • Liver- 500 gms
  • One kidney/Half of each
  • Blood 100 cc (in NaF), (Minimum 10 ml)*
  • Urine- 100 cc– (Commonly used preservatives for chemical urinalysis specimens include tartaric acid, boric acid, chlorhexidine, ethyl paraben, thymol and sodium propionate [Toulene is the best preservative for urine examination])

• Formaldehyde is used for preservation of Museum specimens and not for preservation of viscera for toxicological analysis. (Formalin is 40% formaldehyde.)

• Viscera is stored at 4°C

• Histopathology specimen is preserved in 10% neutral formalin/95% Alcohol

When Preservatives are not Necessary:

Preservatives are not necessary in following conditions:

  • Preservatives are not necessary if the viscera are being analyzed within 24 hours.
  • If the sample is being kept in refrigerator or ice box.
  • If the sample is hair, bones or nails.
  • In case of lungs in detecting volatile poisons.

Common Preservatives :

Most commonly used preservative is saturated sodium chloride.: Saturated Solution of Sodium Chloride is the common preservative used for preservation of viscera. Almost every poison can be preserved in saturated solution of sodium chloride except poisoning from corrosive acids, alkalis, corrosive sublimate and aconite. However, carbolic acid can be preserved in saturated solution of sodium chloride.

The best preservative for preservation of viscera is rectified spirit. : Rectified Spirit is also considered as an ideal preservative. But there are some exceptions, such as; alcohol, kerosene, chloroform, ether, chloral hydrate, formic acid, carbolic acid, phosphorus and paraldehyde.

Rectified spirit is not used in:

  • Alcohol
  • Phenol
  • Phosphorous
  • Paraldehyde.

Which Body Part or Organ should be preserve in which type of Poisonings?

  • Heart– Strychnine, Digitalis
  • Spleen- It is the best organ for Cyanide poisoning
  • Brain– Alkaloids, organophosphates, volatile organic poisons
  • Bile– Narcotic drugs, cocaine, methadone, Glutathione, Barbiturates, Tranquilizers
  • Vitreous– Alcohol, Chloroform
  • Lung– Gaseous poison, HCN, Alcohol, Chloroform
  • Bone– Arsenic, Antimony, thallium, Radium
  • Skin– C/o hypodermic injections (10 cm radius about site with muscle and fat), snake bite
  • Hair, Nails, Uterus, spinal card– When indicated
  • CSF– (in 10 mg NaF/ml of fluid) in Alcohol intoxication.
  • Body Fat— Endrin ,DDT(Organo Chlorines)
  • Muscle– When internal organs badly putrified

Which specimen should be kept in which preservative?

  • 10% formalin for a week: For complete examination of the brain.
  • Additional materials to be preserved in poisoning due to Alcohol: About 100 ml of blood from a peripheral vein and as much CSF as can be withdrawn. 10 mg / ml of sodium or potassium fluoride and 3 mg of sodium oxalate with Fluoride should be used to preserve CSF.
  • All acids except carbolic acid: Rectified spirit.
  • In all poisons excluding acids but including carbolic acid: Saturated solution of common salt.
  • Blood for chemical analysis: Potassium oxalate +NaF. (with a layer of liquid paraffin above it in cases of carbon monoxide and other gas poisoning cases).
  • Bleaching powder or chlorine gas: Rectified spirit.
  • Blood for grouping: Equal volume of 5% sodium citrate + 0.25 ml. formalize.
  • Barbiturates: One half of the brain.
  • Carbon monoxide, coal gas, chloroform, cyanides: About 100 ml of blood from the heart and one half of the brain.
  • Heavy metals: About 10 cm. of shaft of long bone (femur), about 5 gms. of plucked scalp hair, all finger or toe nails (nails are entirely removed from their beds), skin of the back and a wedge of quadriceps muscles before opening the abdomen.
  • Injected poisons: Skin, subcutaneous tissue and muscle forming the injection track, bone deep and similar material from the opposite area as control.
  • Organ phosphorus, endrine, neurotic poisons: Brain, spinal cord. Also in certain special circumstances, the following material is to be preserved
  • NaF: should be added to urine, blood, vitreous humor for Alcohol estimation and to samples of- Cocaine, Carbon Monooxide, Cyanide.
  • Sodium or Potassium Fluoride: 10 mg / ml of sodium or potassium fluoride and 3 mg of sodium oxalate for blood. Fluoride should also be added to urine.
  • Virology Specimen: 80% Glycerol in Buffer saline.
  • Vitreous Humor: Stored in a refrigerator (4°C) upto 48 hours. 10 mg / ml of sodium or potassium fluoride and 3 mg of sodium oxalate with Fluoride should be used to preserve CSF.

Note: The viscera should never be preserved in formaldehyde and the same should be used only for histopathology purpose rather than toxicology purpose.

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