4.methanol in Wine

Toxicology Analysis of
Methanol in Traditional
Wine/ Ethanol
Practical work, year 4, semester 2

I. INTRODUCTION
• Methanol is a solvent and a reagent widely used in laboratory.
• Moreover, it is within the composition of antifreeze (often mixed with

ethylene glycol), windshield washing fluids and solutions employed in
some reproduction processes of documents.
I. INTRODUCTION
• Causes of intoxication of Methanol:

• Accidental or intentional ingestion of substances containing methanol (the rubbing
alcohol: denatured alcohol, which contains ethanol and acetone, falsified alcoholic
beverage, etc.).
• In addition, ingestion of industrial ethanol (which often contains methanol as a
denaturant) may also be a cause of poisoning, but the symptoms are usually less severe
than with pure methanol.
In fact, the toxicity of methanol is a result of its transformation to formaldehyde

by alcohol dehydrogenase.
THE PRATICE IN TOXICOLOGICAL
LABORATORY
Method I
II. OBJECTIVE
Identify the presence of Methanol via qualitative test in suspected

traditional wine.
The sample (traditional wine) has been collected in case of poisoning in a

province of Cambodia. This sample has been delivered urgently to the lab
to do qualitative test whether it can be contaminated with methanol or not.
 The qualitative test above is applicable to urine, stomach contents and scene residues.
PRINCIPLE
Methanol is oxidized specifically with potassium dichromate in sulfuric
acid milieu to form Formaldehyde. Then formaldehyde is complexes by
the addition of sulfuric chromotropic acid solution (sulfochromotropic
acid) to give the violet color.
MATERIALS AND REAGENTS
Materials: Reagents:
• Volumetric flask
• Potassium dichromate
• Test tubes
• Sulfuric acid
• Tube rack
• Chromotropic acid
• Beaker
• Ethanol
• Dropper
CONFIRMATION TEST
 Applicable to urine, stomach contents and scene residues.
 Reagents preparation:
1. Solution Potassium dichromate reagent: Potassium dichromate (25 g/l) in purified water, 25ml
2. Solution Potassium dichromate + concentrated sulfuric acid (1:1), 10ml
 Method:
• 1ml of sample/ standard control (-)/ standard control (+) then add 0.1 ml of (potassium dichromate + sulfuric acid) and allow to stand at
room temperature for 5 minutes.
• Add 0.1 ml of ethanol and about IO mg of chromotropic acid and gently add sulfuric acid drop by drop (10-20 drops) down the side of the
tube so that it forms a separate layer at the bottom.
 Result:
A violet color at the junction of the two layers indicates the presence of methanol. Formaldehyde also gives a positive result in this test.
 Sensitivity: Methanol, 50 mg/I.

Method II
II. OBJECTIVE
Identify the presence of Methanol via semi-quantitative test in

suspected alcohol.
PRINCIPLE
Methanol is oxidized specifically with potassium dichromate in sulfuric
acid milieu to form Formaldehyde. Then formaldehyde is complexes by
the addition of sulfuric chromotropic acid solution (sulfochromotropic
acid) to give the violet color.
Procedure
 Reagents preparation:
1. Solution Potassium dichromate reagent: Potassium dichromate (25 g/l) in purified water, 25ml
2. Solution Potassium dichromate + concentrated sulfuric acid (1:1), 20ml
 References standard preparation:
1. Prepare references standard in different concentration 0%, 20%, 40%, 60%, 80% & 100%.
 Method:
• 1ml of sample/ references standard then add 0.1 ml of (potassium dichromate + sulfuric acid) and allow to stand at room temperature for 5
minutes.
• Add 0.1 ml of ethanol and about IO mg of chromotropic acid and gently add sulfuric acid drop by drop (10-20 drops) down the side of the
tube so that it forms a separate layer at the bottom.
 Result:
A violet color at the junction of the two layers indicates the presence of methanol. Comparation sample with references standard.
 Sensitivity: Methanol, 50 mg/I.

CLINICAL INTERPRETATION
Acute methanol poisoning is characterized by delayed onset of coma, cyanosis,
respiratory failure, marked metabolic acidosis, electrolyte imbalance, hyperglycaemia
and blindness, which may be permanent. Treatment is aimed at correcting metabolic
abnormalities, inhibiting methanol metabolism by giving ethanol and removing
unchanged methanol by peritoneal dialysis or hemodialysis. Measurement of plasma
ethanol concentrations can be useful in monitoring therapy with this compound.
The Ends.

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Toxicology Analysis of

Practical work, year 4, semester 2

• Methanol is a solvent and a reagent widely used in laboratory.

• Moreover, it is within the composition of antifreeze (often mixed with

• Causes of intoxication of Methanol:

In fact, the toxicity of methanol is a result of its transformation to formaldehyde

Identify the presence of Methanol via qualitative test in suspected

The sample (traditional wine) has been collected in case of poisoning in a

2. Solution Potassium dichromate + concentrated sulfuric acid (1:1), 10ml

 Sensitivity: Methanol, 50 mg/I.

Identify the presence of Methanol via semi-quantitative test in

2. Solution Potassium dichromate + concentrated sulfuric acid (1:1), 20ml

 References standard preparation:

 Sensitivity: Methanol, 50 mg/I.

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