Griess test

After the Birmingham Six case, the Griess test has become highly controversial amongst the forensic community. Owing to its importance and impact on forensic science, this case is described herewith in detail. 

The conclusion is that a positive Griess test on hands cannot constitute evidence of the hands having had contact with explosives. The Griess test should be a presumptive test, to be used only as a preHminary tool for the investigation. Its results should be confirmed in the laboratory before being presented in court. 

Following the Birmingham Six case, the Griess test has become somewhat discredited by the forensic community. It should be emphasized, however, that when properly used, it is an excellent tool which can serve as a basis for an efficient field test. An explosive detection kit (ETK (explosive testing kit)), partly based on the Griess test, was successfully used in Israel in several terror and non-terror investigations [49] (see below). 

Tridite, which consists of PA DNPh, gives colors characteristic for PA, such as orn color with ethylenediamine deep red with the Griess Test(Modified)(See Charts A St B). None of the known colorimetric tests will detect DNPh in the presence of PA, because the colors produced by DNPh with some reagents (See Chart B) are always obscured by colors produced by PA... 

Trimonite, which consists of PA St MNN, gives a deep red Griess test(characteristic for PA) and a deep blood-red DPhA test(characteristic for MNN)(See Chart B)... 

Primary and secondary alkyl nitrites under basic conditions eliminate nitrite with concomitant production of a carbonyl group. The nitrite can be estimated by its formation of a diazonium ion with p-aminobenzenesulfonamide, followed by formation of an azo dye. The sequence is termed the Griess test... 

Testing of urine for nitrite is important because it can be used to detect urinary tract infection. The basis of the spot test used in the Nitur-Test (Boehringer Mannheim) and in the Rapignost strip system (Hoechst AG) is the classical Griess test. 

Griess test A presumptive test used in the analysis of GSR. 

If this oxidation is carried out in the presence of sulfanilic acid, the latter is diazotized and there is no redox reaction between the nitrous acid and the hydriodic acid (compare page 366). After removal of the excess iodine with thiosulfate, the diazonium salt may be coupled with a-naphthylamine to give a red azo dye. (See page 364 regarding this sensitive Griess test for nitrites.)... 

Metallic zinc reduces nitrates, in acetic acid solution, to nitrous acid. A sensitive test for nitrates results if the reduction is accomphshed in the presence of the reagents required for the sensitive Griess test for nitrites (see page 364). Nitrites must be removed before carrying out the test. The removal is best done with sodium azide as described below. 

Test with sulfanilic acid and a-naphthylamine (Griess test)i or N-l-naphthylethylenediamine ... 

In the classic Griess test, use is made of sulfanilic acid (I), with subsequent coupling of the resulting diazonium compound with a-naphthylamine (II), to give the red -benzene sulfonic acid-azo-a-naphthylamine (HI), here shown in its baso-form, to produce the red, water-soluble azo dye (IV). 

Griess reagent analychem A reagent used to test for nitrous add it is a solution of sulfanilic add, a-naphthylamine and acetic add in water. gres re.a jant ... 

In the Franchimont test [42], nitramines are reduced to nitrite ions by zinc and acetic acid and then subjected to the Griess reaction. A modification of this test was used for the identification of nitramine impurities in RDX [43]. 

As part of a routine procedure, a local forensic scientist was summoned to swab the detainees hands in an attempt to find explosives traces. Fie took etheral swabs from the suspects hands. On these swabs, he applied a field test based on the Griess reaction. Two of the five tested positively on one of their hands. The suspects were then interrogated extensively and several of them signed a confession. 

As stated above, nitrate esters (such as NG or PETN) and nitramines (such as RDX or HMX), form nitrite ions under alkahne conditions and therefore can be detected by the Griess reaction. However, the Griess spot test by itself does not enable to distinguish between individual explosives within these groups. 

Laboratory ELITE explosives detection device. Similarly to the aforementioned ETK, it can detect traces of mOitary, as well as homemade explosives, by applying the common Meisenheimer and Griess reagents. Because of the addition of a heating device nd efficient swiping for sample collection, the reported sensitivity of ELITE is 2—50 times higher than that of other commercial field tests [102]. For example, ELITE detection limits for TNT, 2,4-DNT, and tetryl were found to be 50, 100, and 50 ng, respectively. Lower thresholds (25—50ng) were reported for PETN, RDX, HMX, and NC [102]. 

X. Treatment with Modified Griess Reagent. Dissolve in a test tube ca O.lg of the sample... 

Refs l)Colvei(1918), 234-36(Color reaction with NaOH or NH3 solns of nitroderivs of benzene, toluene, naphthalene, etc a table) 2)E. Elvove, IEC II, 860-64(1919) [Modification of Webster s test for colorimetric detn of TNT in urea, described in BritMedJ 2, 845(1916). Instead of using Webster s KOH soln, Elvove proposed to use Griess Reagentf qv)] 3)H.W. van Urk, ChemWeekblad 21, 169 71(1924) CA 18, 2142(1924)(Discussion on formation of colored compds by reaction of alkali alcoholates with polynitrocompds of the aromatic series)... 

Sulphanilic acid-a-naphthylamine reagent. (Griess-Ilosvay test) This test depends upon the diazotization of sulphanilic acid by nitrous acid, followed by coupling with a-naphthylamine to form a red azo dye ... 

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