THE MYSTERY BEHIND THE DEATH OF A BRIDE

By

R.S. Verma, R.M. Tripathi and A.K.Dalela

Central Forensic Science Laboratory,

DFS, MHA, Govt. of India, Sec.36-A, Chandigarh

TRENDS OF POISONING

In Northern India, 25% cases of poisoning relate to insecticides Carbamate constitutes a major share Correct identification of insecticides is a challenge to toxicologists

PROBLEMS WITH THE SAMPLES

The quality and quantity of insecticides available in the biological tissues/fluids is usually very lowLonger period in between ingestion and collection of samples further reduces availability of insecticides

ROUTINE TECHNIQUES- LIMITATIONS

Colour tests lack specificityTLC also lacks specificity Rt parameter in GC & HPLC being non-specific only enhances the confidence level for identification

ADVANTAGES OF USING GC-MS

Fast analysisSensitive detectorImproved resolutionDerivitization not necessaryCorrect identification possible

HISTORY OF THE CASE

A newly married lady admitted in the hospital after suspected poisoning Stomach wash preserved in the hospitalDoctors suspected organophosphorus/ celphos poisoning Lady died after 62 hours hospitalisation

Contd….Report of viscera did not indicate any poison(Chemical examination lab.)CFSL, Chandigarh received only stomach wash (15 ml) on order of Pb. & Hr. High CourtSample size was very small

THIN LAYER CHROMATOGRAPHY

TLC gave a faint black spot with Tollen’s reagentMay be due to carbamate/ organophosphorous insecticideGave negative results for organophosphorous insecticide

GC-MS ANALYSIS

Capillary column DB-5(30m)Column Temp. 80oC-250oCTemp. Programming 8oC/minInjector Temp. 250oCDetector Temp. 250oCIon Source Temp 200oC

TIC OF CASE SAMPLE

Contd….

i) Base peak 110

ii) Mass spectrum contained three characteristic ions with m/z 110, 81&152

iii) Three ions not enough to form opinion

WHICH CARBAMATES CONTAIN THREE IONS? (110, 152 & 81)

Carbofuran 221,165,149,131,122,103,

91,77,57

Carbaryl 201,167,157,144,127,115,

101,89,72,57

Propoxur 209,152,137,121,110,92,81,

64,58

Pirimicarb 238,166,152,138,123,110,

109,72,53

Contd……..

Methicarb 225,168,153,139,121,109,91

77,58

Methomyl 162,127,105,88,71,58

Aldicarb 144,115,100,86,76,69,58

LIBRARY MASS SPECTRUM OF PROPOXUR

LIBRARY MASS SPECTRUM OF PIRIMICARB

Contd……

Only propoxur contains ions 110, 152 & 81 Base peak is 110 & ions 152 & 81 are with about 15 to 20% abundancePirimicarb contains only two ions 110 & 152 with less than 10% abundanceBase peak in pirimicarb in 166 and also ion with m/z 81 is absent

Contd…

On the basis of the presence of three characteristic ions with m/z 110, 152 and 81 and their abundance, the probable carbamate remains to be propoxurOther ions present in mass spectrum of propoxur such as 92,82 & 64 were found to be absent in the mass spectrum of case sampleAbsence of remaining ions restricts identification of insecticide propoxur in case sample

Contd..To corroborate findings TLC of standard propoxur with varying amount was conducted under similar conditions Mass spectra of extracted standard propoxur also contained ions at 110, 152 and 81 with base peak and 110

TIC WITH MASS SPECTRUM OF PROPOXUR

TIC WITH MASS SPECTRUM OF CASE SAMPLE

Contd…

Retention time of TIC of propoxur and its ions with m/z 110, 152 and 81 is 1.83 minutesRetention time of TIC of case sample & ions 110, 81 & 152 is also 1.83 minutesTIC of case sample and extracted standard propoxur shows that all the three ions present have originated from the same peak having similar retention time

CONCLUSIONNo doubt, eight peak mass spectrum is required for the identification of the compoundIn this study, identification of the compound could be possible with the help of three ions onlyIn toxicological samples, quality and quantity of insecticides can be very low, where it will be difficult to get eight peak mass spectrum

•Contd…

The method stated above focussing the characterization of most abundant ions and also considering their retention time matching with TIC of the substance can be safely used to identify unknown substance including carbamatesHence, analysis confirms poison in gastric lavage of lady. Thus, solving mystery of her death.

THANKS