Azide Detection

One of the first demonstrations of diamond s usefulness in electroanalysis was the oxidative detection of azide anion in aqueous media [29,30,37]. Sodium azide has been widely used commercially and, in the past, as an inflator for automotive airbags. Azide anion is highly toxic and presents a 

Diazonium salt reduction on a boron-doped nanocrystaUine diamond thin-film electrode (A) general reaction mechanism, (B) a series of cyclic vol-tammetric i-E curves in 1 mM 4-nitrophenyldiazonium salt + 0.1 M TBABF4/ CH3CN during the surface derivatization step, and (C) a cyclic voltammetric i-E curve for the derivatized surface in 0.1 M TBABF4/CH3CN. Scan rate = 0.05 V/s. Electrode area = 0.2 cm.  

Marcel Dekker, Inc. 270 Madison Avenue, New York, NewYoric 10016 

Diamond provides a sensitive, reproducible, and stable response for azide electrooxidation, leading to superior detection performance compared with glassy carbon. The electrochemical reaction at diamond is believed to be [29,30,37] 

A peak-shaped oxidation response was observed in cyclic voltammetric measurements (pH 7.2 phosphate buffer) made with both electrodes, but the background currents, upon which the faradaic response is measured, were dramatically different. The oxidation peak potentials, Ep, were 1045 and 1100 mV, and the background-corrected peak currents, were 57 and 88 pA for glassy carbon and diamond, respectively. This 35% difference in current magnitude was an unusual case, as most diamond electrodes yielded peak currents that were within 5% of those for glassy carbon. 

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Figure 5.26 The temperature dependencies of the rate constant of decay of singlet 2-fluorophenylnitrene 70a (curve 1) and the apparent rate constant of formation of triplet 2-fluorophenylnitrene 73a and ketenimine 72a (curve 2). Solid lines (1) and (2) results of nonlinear global fit of the data to an anal5dical solution according Scheme 5.5. Insert transient absorption spectra produced by LFP (249 nm) at 295 K of 2- fluorophenyl azide in pentane, detected 500 ns after the laser pulse (curve 1) and 4-fluorophenyl azide detected 50 ns after the laser pulse (curve 2) and persistent spectrum of triplet 2-fluorophenylnitrene (73a) in methylcyclohexane at 77 K (curve 3).

The discussed results confirm the potential and beneficial effects of iodine-azide reaction as a detection system in planar chromatography. The proposed detection system allows selective and sensitive detection for thiol or thione at picomol per spot level (procedures 3 and 4). The other detection methods routinely used in TLC—iodine vapor, UV—gave a positive but less sensitive test. Iodine-azide detection system is inexpensive the reagents are readily available chemicals and the analysis times are short. The non-improved iodine-azide method (procedures 1 and 2) has not been widely applied on account of the relatively high detection limits obtained with the procedure. 

Kazmierczak, D. Ciesielski, W. Zakrzewski, R. Detection and separation of amino adds as butylthiocarbamyl derivatives by thin-layer chromatography with the iodine azide detection system. J. Liq. Chromatogr. Relat. Technol. 2005,... 

Iodine-azide detection system is very selective because the reaction between iodine and azide ions takes place only in the presence of sulfur(II) compounds ... 

Currently, three modes of separation (ion, ion-pair, and reversed-phase chromatography) for the detection of sulfur(II) compounds using the iodine-azide detection system are available. 

Zakrzewski, R. Ciesielski, W. Iodine-azide detection system in planar chromatography. Trends Chromatogr. 2007, 3, 1-10. 

Zakrzewski, R. Determination of methimazole in urine following its separation by RP-HPLC with iodine-azide detection system. J. Chromatogr. B, 2008, 869, 67-74. 

The detection limit obtained with the diamond electrode was 8 nM (0.3 ppb) for S/N = 3, with a linear dynamic range of 5 orders of magnitude. The response of the diamond electrode was stable for periods up to 12 h. Thus, diamond electrodes outperformed GC in terms of linear dynamic range, detection limit and response stability for azide detection. 

Phenylhydrazine condenses with carbon disulphide to yield the phenylhydrazine salt of P phenyldithiocarbazic acid (I), which on heating at 96-98 until the first evolution of ammonia is detectable affords diphenylthiocarb-azide (II) ... 

Corrosion products and deposits. All sulfate reducers produce metal sulfides as corrosion products. Sulfide usually lines pits or is entrapped in material just above the pit surface. When freshly corroded surfaces are exposed to hydrochloric acid, the rotten-egg odor of hydrogen sulfide is easily detected. Rapid, spontaneous decomposition of metal sulfides occurs after sample removal, as water vapor in the air adsorbs onto metal surfaces and reacts with the metal sulfide. The metal sulfides are slowly converted to hydrogen sulfide gas, eventually removing all traces of sulfide (Fig. 6.11). Therefore, only freshly corroded surfaces contain appreciable sulfide. More sensitive spot tests using sodium azide are often successful at detecting metal sulfides at very low concentrations on surfaces. 

Arylsulfenyl azides in this reaction mainly give the product of the triazole ring opening 380, which is isomeric to the expected triazole 381 detected only in negligible quantities (72S571). 

Studies of presumed azido-tetrazole tautomerism for 3-azido-l,2,4-benzotria-zine 1-oxides 3 show that compounds 3 exist only in the form of azides, both in the crystalline state and in solution. Similar results were obtained in the studies of 3-azido-1,2,4-triazine 1-oxides 4, which have never been detected in the tetrazole form (69CB3818, 77JHC1221, 82JOC3886). 

The reaction of 1030 with nitrous acid led, through azide 1031, to labeled 1032. The proposed angular structure 1032 is the major component both in solution and in the solid state. By means of 13C-NMR, a ternary equilibrium was detected in dimethyl sulfoxide, which involves 1032 as the main compound in addition to 1031 and the linear isomer present in smaller... 

Mercury (Quicksilver, Hydrargyrum), Hg, at wt 200.61, silvery liq, mp —38.87°, bp 356.9°, d 13.546g/cc at 20°. Insol in w, HC1, ale and eth sol In nitric acid. Sometimes found native poisonous. Can be prepd by heating the ore cinnabar (HgS) either in air or with lime. Forms numerous salts, some of which are very expl, eg, Hg fulminate, Hg azide, etc. The presence of Hg in expls, even in minute quants, is unde-sireable because it affects the result of thermal stability tests. Marshall (Ref 1) describes various tests used in Engl and Ger for its detection in different expls and propints Refs 1) Marshall 2, 708-12(1917) 2) Mellor... 

Surprisingly, no marked effect of the substituent R2 on the product ratio was observed whereas in the similar reaction of 2 -hydroxychalcone dibromides a great influence of substituent R2 on the competing reaction pathways was found (ref. 4). Noteworthy, no formation of the azide E (regioisomer of 2) was detected. 

The possible routes leading to azides 2 are outlined in Scheme 1. The only pathway which we can exclude the 2=>C=>D=>E=>2 sequence since neither intermediate E nor its possible derivative E could be detected in the reaction mixture. (P-Azido a,P-unsaturated ketones are known to afford isoxazoles via nitrenes derived by loss of nitrogen (refs. 4,10). Azides 2 may form either via intermediate A (Sn + E route) or via allyl bromide-type intermediate B (E -f Sn route), both routes may operate on the basis of experimental results obtained so far. 

Irreversible reaction of [18] iodine with acetylsalicylic acid, aethaverine, amidopyrine, ascorbic acid, benzo-caine, quinine, dihydrocodeine, fluorescein, glycine, hydrocortisone acetate, isoni-azid, metamizole, papaverine, paracetamol, phenacetin, phenol-phthalein, piperazine, resorcinol, salicylic acid, salicylamide, sulfaguanidine, thymol, triethanolamine, tris buffer detection by reaction chromatography... 

The detection depends on the iodine azide reaction that normally takes place very slowly and during the course of which sodium azide reacts with iodine to form sodium iodide with the production of nitrogen ... 

Ridomil, with which the treatment with starch solution was not carried out, is said to yield brown chromatogram zones on a pale yellow background [14]. Hence, it may be assumed that this detection is based not on the iodine azide reaction but on the physical adsorption and enrichment of iodine in the lipophilic chromatogram zones (cf. Iodine Reagents ). 

D. Pseudohalogeno-derivatives.—Little work has been carried out in this area. Isocyanates of cyclic phosphazenes, previously unknown, are thought to be formed in the reaction of NgPaBrg with AgOCN in nitro-methane. They were detected by i.r. spectroscopy, and underwent ready polymerization, which precluded their isolation. On the other hand, isothiocyanates, [NP(NCS)2] (n = 3 or 4), are well known and a detailed study of their spectra has been reported. The azide, N3Pa(N3)8, has been the subject of an i.r. study which suggests that the molecule has Z)3A symmetry. 

Figure 10 Capillary ion analysis of 30 anions 1 = thiosulfate, 2 = bromide, 3 = chloride, 4 = sulfate, 5 = nitrite, 6 = nitrate, 7 = molybdate, 8 = azide, 9 = tungstate, 10 = monofluorophosphate, 11 = chlorate, 12 = citrate, 13 = fluoride, 14 = formate, 15 = phosphate, 16 = phosphite, 17 = chlorite, 18 = galactarate, 19 = carbonate, 20 = acetate, 21 = ethanesulphonate, 22 = propionate, 23 = propanesulphonate, 24 = butyrate, 25 = butanesulphonate, 26 = valerate, 27 = benzoate, 28 = D-glutamate, 29 = pentane-sulphonate and 30 = D-gluconate. Experimental conditions fused silica capillary, 60 cm (Ld 52 cm) x 50 p i.d., voltage 30 kV, indirect UV detection at 254 nm, 5 mM chromate, 0.5 mM NICE-Pak OFM Anion-BT, adjusted to pH 8.0, with 100 mM NaOH. (From Jones, W. R. and Jandik, R, /. Chromatogr., 546, 445,1991. With permission.)...

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