Monocrotophos is a member of Organophosphate insecticide. It is an important insecticide and has a diversified role in agriculture in INDIA. The increasing numbers of human poisoning cases were found to be occurred by the consumption of organophosphate insecticide monocrotophos. So in this paper, we represent a novel Thin Layer Chromatographic spray reagent for the detection and identification of Monocrotophos

B S Dhobal

C D Pawar

R K Pardeshi

U D Pawar

English

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To Chemistry Journal Vol 6 (2020) ISSN: 2581-7507                                                  http://purkh.com/index.php/tochem 
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New Chromogenic Spray Reagent for TLC Detection and Identification of Organophosphrous 
Insecticide Monocrotophos in Biological Material. 
U D. Pawar1, C D Pawar2, B S. Dhobal 3, R K. Pardeshi 4* 
Regional Forensic Science Laboratories Aurangabad. MS, India1 
Department of chemical technology Dr BAMU, Aurangabad MS, India2 
B R Barwale College Jalna, MS, India3 
Sant Ramdas College Ghansawangi, Jalna, MS, India4* 
rkpardeshiudp@gmail.com* 
Abstracts  
Monocrotophos is a member of Organophosphate insecticide. It is an important insecticide and has a diversified 
role in agriculture in INDIA. The increasing numbers of human poisoning cases were found to be occurred by 
the consumption of organophosphate insecticide monocrotophos. So in this paper, we represent a novel Thin 
Layer Chromatographic spray reagent for the detection and identification of Monocrotophos. 
Keywords: Thin-layer Chromatography, Organophosphate insecticide, Monocrotophos, Forensic science, 
Biological material. 
Introduction  
During the last few years, Forensic Science Laboratories of Maharashtra, India, detected several human poisoning 
cases due to consumption of Monocrotophos. Large number of biological samples (postmortem samples) were 
received for toxicological analysis. Thin-layer chromatography (TLC) and high-performance thin-layer 
chromatography (HPTLC) are the cheapest preferred method of choice for a toxicological analysis of pesticides. 
By observing the results of toxicological chemical analysis the conclusion can be drawn that Monocrotophos 
played a key role in many poisoning cases. Proposed chromogenic reagent is found to be a selective spray 
reagent for Monocrotophos in routine analysis by HPTLC. Monocrotophos reacts with this chromogenic reagent 
and gives intense pink-colored compound. The other organochlorine insecticides, organophosphate insecticides 
and pyrethroid insecticide did not give any positive reaction with this reagent Biological material constituents 
(amino acids, peptides, proteins, fats etc.) also do not interfere with this chromogenic reagent.  
Monocrotophos Dimethyl (E)-1-methyl-2-(methylcarbamoyl)vinyl phosphate is the organphsphate compound. 
Toxicology department detected several cases of human poisoning with Monocrotophos in routine forensic 
toxicological analysis.The insecticides are generally analyzed by thin-layer chromatography (TLC) as a method 
of choice.The chemical structure of Monocrotophos is shown below it has easily hydrolyzable phosphate ester 
group. 
 
Thin layer chromatography (TLC) is the method of choice for screening biological sample due to its speed, low 
cost, and versatility. Several chromogenic reagents are reported such as p-benzoquinone reagent [1],potassium 
iodate-starch[2],sodium carbonate-chloranil in acetone[3], mercuric nitrate diphenylcarbazone[4],palladium 
To Chemistry Journal Vol 6 (2020) ISSN: 2581-7507                                                  http://purkh.com/index.php/tochem 
 6 
chloride [5],vanillin reagent[6],benzil reagent[7],methanolic ferric chloride[8],50% potassium iodate in 1:1ethanol-
hcl[9],Cupric acetate[10] diazotized sulphanilamide or sulphanilic acid [11],Chromogenic reagent [12] etc. 
This study reports a new method for the analytical determination of Monocrotophos in biological samples by 
TLC. Selective detection of Monocrotophos after TLC is possible by use of reported chromogenic spray reagent. 
Monocrotophos reacts with the chromogenic reagent and produce an intense pink-colored compound in 
presence of hydrochloric acid. In continuation of our research work [13-16] on the identification and detection of 
different spraying reagents for the different poisons we developed synthetic poisons, with the hope it gives 
quick results for forensic toxicology field.              
Experimental Materials and Methods 
Chemicals and Reagents  
All reagents were of analytical-reagent grade commercial formulation of Monocrotophos (UPL Ltd, India) 
solution was prepared in ethyl acetate (2 mg mL
−1
).  
Chromogenic reagent  
2 gm. Stannous chloride (SNCL2) in 20%  of 40 ml  Hydrochloric acid (S.D. Fine-Chem Ltd., Mumbai, India). 
Both were mixed slowly and with continuous stirring. 
Extraction of Monocrotophos from Biological Materials  
About 50 g viscera sample [(I) pieces of stomach, small and large intestine with its contents, (II) pieces of liver, 
spleen, kidney, and lungs] containing history of monocrotophos poisioning was taken. Material was cut into fine 
pieces and minced carefully, 50 mL ethyl acetate was added and the contents were kept for 2 hours and then 
the extract was transferred into a steel capsule and evaporated to dryness at room temperature. The residue 
was re dissolved in 1 mL of ethyl acetate and was used for Thin-Layer chromatography.  
Thin-Layer Chromatography  
TLC plates (silica gel   mfg. by Merck Ltd., Germany) were used the silica gel was mixed with water for four hours 
with stirring and then was spread on  glass plate and kept for two hours at room temperature then it was put 
an oven in at 1100 c then  plate was activated and ready to use. Hexane- acetone (9.5:0.5, by volume) mixture 
was used as solvent system for monocrotophos residues. The samples were spotted on TLC plates with fine 
capillary tubes along with pure Monocrotophos as the standard. The plates were dried, and the chromatogram 
was developed in a pre-saturated tank containing the solvent system as mentioned above. After developing the 
plate, the solvent front (distance travelled by the solvent) was immediately marked and the extra solvent was 
evaporated (dried) in fume hood. The plate was then sprayed with above mentioned chromogenic reagent and 
the plate was then kept in oven at 1100c for 10 min. Pink colored spot with white background was clearly visible 
at RF 0.76 as shown in figure 1 RF values and color of spots tallied with commercial sample of standard 
Monocrotophos. 
Results and Discussion  
Monocrotophos is an organic compound which reacts with above chromogenic reagent to give intense pink-
colored compound. The color of the spot remains stable for about 6 hours. The limit of detection with this 
reagent is approximately 6μg. The reagent does not react with the organochlorine insecticides endosulfan, BHC, 
and DDT, etc and with the organophosphorus insecticides dimethoate, phorate, quinalphos, etc. and with the 
synthetic pyrethroids like fenvalerate, cypermethrin, and deltamethrin. Visceral constituents (amino acids, 
peptides, proteins, fats, etc.) do not interfere. The chromogenic reagent is utilized in the proposed method is 
To Chemistry Journal Vol 6 (2020) ISSN: 2581-7507                                                  http://purkh.com/index.php/tochem 
 7 
cheap and easy to prepare and does not involve any critical reaction condition or tedious sample preparation. 
Hence, this can be used routinely for the detection of Monocrotophos in biological materials.                                                                           
 
Figure 1 
TLC showing monocrotophos residues using chromogenic spray reagent: a) blank viscera, b) viscera with 
monocrotophos poisoning, and c) standard monocrotophos.in shown figure  
 Conclusions  
To the best of our knowledge, chromogenic reagent stannous chloride along with hydrochloric acid was used 
for the first time for the detection and identification of Monocrotophos in biological post-mortem samples in 
fatal poisoning cases of Monocrotophos. The proposed reagent is simple, and can be used for routine analysis 
of Monocrotophos. Work on new spray reagents is in progress, and the authors hope to report it soon when it 
is done.  
Acknowledgment  
Authors are grateful to Dr. K. V. Kulkarni, Director, Forensic Science Laboratories, Home Department State of 
Maharashtra, Mumbai, India, and Head Department of chemistry Dr Babasahab Ambedkar Marathwada 
University Aurangabad MS. India. For helpful discussion and suggestions. 
Conflict of Interest The authors declare that they have no conflict of interest. 
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New Chromogenic Spray Reagent for TLC Detection and Identification of Organophosphrous Insecticide Monocrotophos in Biological Material.

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New Chromogenic Spray Reagent for TLC Detection and Identification of Organophosphrous Insecticide Monocrotophos in Biological Material.

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