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International Programme on Chemical Safety. Basic Analytical Toxicology. 6.93 Phosphorus and phosphides.Obtenido de: http://www.who.int/ipcs/publications/training_poisons/basic_analytical_tox/en/index11.html

6.93 Phosphorus and phosphides

Yellow phosphorus (P) and the phosphides of zinc, aluminium andmagnesium are used as rodenticides, usually as a paste containing sugarand bran.

QUALITATIVE TEST

Applicable to stomach contents and scene residues.

Reagents

1. Silver nitrate solution (saturated) in methanol.

2. Aqueous lead acetate solution (100 g/l).

Method

1. Soak a strip (5 × 1 cm) of filter-paper in the silver nitrate solution and allowto dry at room temperature.

2. Soak a similar strip of filter-paper in the lead acetate solution and againdry at room temperature.

3. Place 5 ml of sample in a boiling-tube fitted with a cork with a slit cut ineach side.

4. Insert the test papers into the slits, stopper the tube and heat on a water-bath at 60°C for 20 minutes.

ResultsIf only the silver nitrate paper is blackened then phosphorus or phosphidesmay be present. If both papers are blackened then sulfides may be presentand the result is inconclusive.

Sensitivity

Phosphorus, 1 g/l.

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International Programme on Chemical Safety. Basic Analytical Toxicology. 6.93 Phosphorus and phosphides.Obtenido de: http://www.who.int/ipcs/publications/training_poisons/basic_analytical_tox/en/index11.html

CONFIRMATORY TEST

Applicable to blackened silver nitrate paper from the test above.

Reagents

1. Ammonium molybdate reagent. Mix 5 g of ammonium molybdate in 100ml of water and 35 ml of concentrated nitric acid (relative density 1.42).

2. o- Toluidine reagent. Mix 50 mg of o- toluidine and 10 ml of glacial aceticacid, diluted to 100 ml with purified water.

3. Concentrated ammonium hydroxide (relative density 0.88).

4. Powdered calcium hypochlorite.

Method

1. Place the silver nitrate paper on a glass microscope slide and cover withcalcium hypochlorite.

2. Leave in a moist chamber for 15 minutes to allow oxidation of phosphideto phosphate.

3. Remove excess hypochlorite by careful washing with a small amount ofpurified water and dry the test paper by blotting with absorbent tissue.

4. Add 50 µl of ammonium molybdate reagent to the dried paper followedby 50 µl of o- toluidine reagent and expose the paper to ammonia fumes fromconcentrated ammonium hydroxide in a fume cupboard .

Results

A blue colour confirms phosphorus.

Sensitivity

Phosphorus, 1 g/l.

Clinical interpretation

Acute poisoning with yellow phosphorus gives rise to gastrointestinalcorrosion, nausea and vomiting, leading to coma, hypotension andhepatorenal damage. Phosphides release phosphine (PH 3) on contact withwater or moist air, and this gas acts on the gastrointestinal and centralnervous systems. Abdominal pain may be followed by nausea, vomiting,gross ataxia, convulsions and coma, with death, usually within 2 hours, insevere cases. Treatment is symptomatic and supportive.