ELSEVIER Analytica Chimica Acta 322 (1996) 203-208 ArfLwTIcA zyxwvuts CHIMICA zyxwvutsrqpo ACTA Chromogenic reagents for iron( II) : studies in the 1,2,4-triazine series J. Almog *, A. Hirshfeld, B. Glattstein, J. Sterling ‘, zyxwvutsrqponmlkjihgfedcbaZ Z. Goren * zyxwvutsrqponmlk Diuision zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA of Identijication and Forensic Science (D.I.F.S.), Israel National Police Headquarters, Jerusalem, Israel Received 2 November 1995; accepted 23 November 1995 Abstract Sixteen as-triazines with different substituents at the 3- and 5-/6-positions have been prepared as the first part of a comprehensive study ultimately to develop an improved means to determine whether an individual has handled a firearm. Their reaction with iron(H) in solution was studied spectrophotometrically, and sensitivity to iron was compared with that of 3-(2-pyridyl)-.5,6-diphenyl-1,2,4_triazine (PDT). Eight of the new compounds exhibited higher sensitivity than PDT. The substituents which brought about the greatest increase in sensitivity where 4-phenyl-2-pyridyl (at position 3) and 3,4-dimethoxyphenyl (at positions 5 and 6). Quite surprisingly, as-triazines containing the 2-quinolyl group at position 3 did not exhibit any visible reaction with iron even after 12 h. 3-~4-Phenyl-2-pyridyl~-5,6-bis-(3,4-dimethoxyphenyl)-1,2,4- triazine was found to be the most sensitive ferroin-type chromogen reported to date (molar absorptivity = 3.81 x lo4 1 mol-’ cm-’ at 571 nm). Keywords: UV-visible spectrophotometry; Complexation; Forensic analysis; Iron(R); 3-(2-PyridylJ-5.6-diphenyl-1.2.4triazine (PDT); 1,2,4,-Triazines 1. Introduction Law-enforcement agencies are faced with an ever-increasing need to determine whether suspects have handled firearms recently. The current “Field Test”, which is in use by a number of police forces, is based on the formation of a magenta coloured complex upon spraying the suspect’s hand with a * Corresponding author. ’ Visiting scientist. Permanent address: Teva Pharmaceutical Industries, P.O. Box 1142, Jerusalem, Israel. * Visiting scientist. Permanent address: D.I.F.S., Israel National Police Headquarters, Jerusalem, Israel. solution of the reagent PDT [3-(2-pyridyll-5,6-di- phenyl-1,2,4_triazine] (Al, Table 1) [l I. The colour results from small traces of iron which are trans- ferred to the hand by contact with the weapon, and may react with PDT in the presence of a mild reducing agent to develop the shape of iron contain- ing parts of the firearm (Fig. 1) [l-6]. The reducing agent is essential as most of the iron on the hand is in the iron(II1) form, which does not give a colour with the chelating agent. It seems, however, that in many cases there is still no colour development even in cases of confirmed recent con- tact with a weapon. This may result from too brief a contact with the weapon and hence too small an amount of iron transferred to the hand, the good 0003-2670/96/%15.00 0 1996 Elsevier Science B.V. All rights reserved SSDI 0003.2670(95)00605-2