Aliphatic polyamine detection

One class of redox analytes for which diamond ofiers a somewhat unique response, especially in the carbon electrode family, is the electrooxidation of aliphatic polyamines, such as cadaverine (H2N-(CH2)5-NH2). Polyamines are ubiquitous components of all cells and are known to play critical roles in the proliferation, difierentiation, maintenance, and neoplastic transformation of mammalian cells [159]. Polyamines are known to be involved in angiogenesis—a process essential for tumor growth and metastasis (biological markers for cancer) [160,161]. 

Despite favorable thermodynamics, the oxidation of aliphatic polyamines in aqueous media is kinetically limited because the reactions require transfer of oxygen from water, and most electrodes lack the ability to support and sustain this complex mechanism [162-164]. The oxidation of amines in aqueous media has been typically limited to a few select anode materials (Au, Ag, Ag-Au alloys, Ag-Pb02) in alkaline media that are capable of transferring oxygen from water to the analyte [165-167]. Stable detection of the amines at these metals is often complicated by electrode fouling with the reaction product(s), resulting in poor response stability. 

Importantly, these analytes can be quantitatively electrooxidized at boron-doped diamond thin-film electrodes without derivatization, the use of pulsed voltammetiic waveforms as is most often required for detection at metal electrodes like gold, or fouling [36,39,43,110]. Boron-doped diamond electrodes possess the requisite physicochemical properties needed to support the amine oxidation via an anodic oxygen-transfer reaction (e.g., surface boron sites for amine coordination and localized sp carbon sites where the oxidant, OH , is generated at lower overpotential than the surrounding diamond matrix), and these properties can 

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Cyclic voltammetric i-E curves, background (dashed line) and total current (solid line), for 1.0 mM (A) CAD, (B) PUT, (C) SPMD, and (D) SPM in 0.01 M borax buffer/0.1 m NaCl, pH 11. The working eleetrode was a microcrystalline diamond film deposited from a 0.5% CH4/H2 ratio and 10 ppm B2H6. Scan rate = 0.1 V/s. Electrode geometric area = 0.2 cm. (From Ref. 121.) 

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HA, heterocyclic amine AA, aromatic amine PA, polyamine Al, aliphatic amine N, nitrosamine MAM, Musk amino metabolities ABDACs, alkylbenzyldimethylammonium chlorides BCD, electron capture detection AED, atomic emission detection FID, flame ionization detection FPD, flame photometric detection GC-MS-SIM, GC-MS selected ion monitoring NPD, nitrogen phosphorus detection NlCl, negative-ion chemical ionization El, electron ionization CGC, capihary GC A, air H, water W, waste. 

Amides of the polyamine spermidine bearing aliphatic or hydroxycinnamic acyl residues are widely distributed in the plant kingdom (Bienz et al. 2002). In most cases the acyl moieties represent the latter residnes. For snch conjugates see Sect 6.6.4.3. A novel metabolite with an aUphatic acyl residue, A/ A/ -ditigloylspermi-dine, has been isolated from the seeds of Ipomoea nil (L.) Choisy collected on Zanzibar/Tanzania (Schimming et al. 2005). It turned out to dominate to an unusual extent in the alkaloid fraction beside seven minor congeners. Most of them were isomers of the main metabolite. All these metabolites were also present in unripe fruits and stems. However, they were not detectable in snch parts from another provenance (Ecnador) of this species (seeds not checked). 

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