Chemiluminescence detection of opium poppy (papaver somniferum) alkaloids

A review with 98 references. The determination of the opium poppy (Papaver somniferum) alkaloids and their semi-synthetic derivatives has important applications in industrial process monitoring, clinical analysis and forensic science. Liquid-phase chemiluminescence reagents such as tris(2,2′-bipyridyl)ruthenium(II) and acidic potassium permanganate exhibit remarkable sensitivity and complementary selectivity for many P. somniferum alkaloids, which has been exploited in the development of a range of analytical procedures using flow analysis, high-performance liquid chromatography, capillary electrophoresis and microfluidic instrumentation.

Chemistry, spectroscopy and analytical applications of certain chemiluminescent reactions

Chemiluminescence, the production of light from a chemical reaction, has found widespread use in analytical chemistry. Both tris (2, 2’-bipyridyl) ruthenium (II) and acidic potassium permanganate are chemiluminescence reagents that have been employed for the determination of a diverse range of analytes. This thesis encompasses some fundamental investigations into the chemistry and spectroscopy of these chemiluminescence reactions as well as extending the scope of their analytical applications. Specifically, a simple and robust capillary electrophoresis chemiluminescence detection system for the determination of codeine, O6-methylcodeine and thebaine is described, based upon the reaction of these analytes with chemically generated tris(2,2'-bipyridyl)ruthenium(III) prepared in sulfuric acid (0.05 M). The reagent solution was contained in a glass detection cell, which also held both the capillary and the cathode. The resultant chemiluminescence was monitored directly using a photomultiplier tube mounted flush against the base of the detection cell. The methodology, which incorporated a field amplification sample introduction procedure, realised detection limits (3a baseline noise) of 5 x 10~8 M for both codeine and O6-methylcodeine and 1 x 10~7 M for thebaine. The relative standard deviations of the migration times and the peak areas for the three analytes ranged from 2.2 % up to 2.5 % and 1.9 % up to 4.6 % respectively. Following minor instrumental modifications, morphine, oripavine and pseudomorphine were determined based upon their reaction with acidic potassium permanganate in the presence of sodium polyphosphate. To ensure no migration of the permanganate anion occurred, the anode was placed at the detector end whilst the electroosmotic flow was reversed by the addition of hexadimethrine bromide (0.001% m/v) to the electrolyte. The three analytes were separated counter to the electroosmotic flow via their interaction with a-cyclodextrin. The methodology realised detection limits (3 x S/N) of 2.5 x 10~7 M for both morphine and oripavine and 5 x 10~7 M for pseudomorphine. The relative standard deviations of the migration times and the peak heights for the three analytes ranged from 0.6 % up to 0.8 % and 1.5% up to 2.1 % respectively. Further improvements were made by incorporating a co-axial sheath flow detection cell. The methodology was validated by comparing the results realised using this technique with those obtained by high performance liquid chromatography (HPLC), for the determination of both morphine and oripavine in seven industrial process liquors. A complimentary capillary electrophoresis procedure with UV-absorption detection was also developed and applied to the determination of morphine, codeine, oripavine and thebaine in nine process liquors. The results were compared with those achieved using a standard HPLC method. Although over eighty papers have appeared in the literature on the analytical applications of acidic potassium permanganate chemiluminescence, little effort has been directed towards identifying the origin of the luminescence. It was found that chemiluminescence was generated during the manganese(III), manganese(IV) and manganese(VII) oxidations of sodium borohydride, sodium dithionite, sodium sulfite and hydrazine sulfate in acidic aqueous solution. From the corrected chemiluminescence spectra, the wavelengths of maximum emission were 689 ± 5 nm and 734 ± 5 nm when the reactions were performed in sodium hexametaphosphate and sodium dihydrogenorthophosphate or orthophosphoric acid environments respectively. The corrected phosphorescence spectrum of manganese(II) sulfate in a solution of sodium hexametaphosphate at 77 K, exhibited two peaks with maxima at 688 nm and 730 nm. The chemical and spectroscopic evidence presented strongly supported the postulation that the emission was an example of solution phase chemically induced phosphorescence of manganese(II). Thereby confirming earlier predictions that the chemiluminescence from acidic potassium permanganate reactions originated from an excited manganese(II) species. Additionally, these findings have had direct analytical application in that manganese(IV) was evaluated as a new reagent for chemiluminescence detection. The oxidations of twenty five organic and inorganic species, with solublised manganese(IV), were found to elicit analytically useful chemiluminescence with detection limits (3 x S/N) for Mn(II), Fe(II), morphine and codeine of 5 x 10-8 M, 2.5 x 10-7 M, 7.5 x 10-8 M and 5 x 10-8M, respectively. The corrected emission spectra from four different analytes gave wavelengths of maximum emission in the range from 733 nm up to 740 nm indicating that these chemiluminescence reactions also shared a common emitting species, excited manganese(II). Whilst several analytical problems were addressed in this thesis and answers to certain questions regarding the fundamentals of acidic potassium permanganate chemiluminescence were proposed, there are several areas that would benefit from further research. These are outlined in the final chapter of this thesis.

Silver sulfide as a staining agent for scanning electron microscopy of nylon 6/MXD6 blends

BACKGROUND: In transmission and scanning electron microscopy imaging, the ability to obtain sufficient contrast between the components of a blend when they are both of a similar chemical structure still remains problematic. This paper investigates the domain morphology of a polymer blend containing two polyamides, nylon 6 and the semi-aromatic polyamide poly(m-xylene adipamide) (MXD6), using scanning electron microscopy in backscattered electron imaging mode. The efficiency of three staining agents, ruthenium tetroxide, phosphotungstic acid and silver sulfide, in obtaining optimum phase contrast between the two polymers is discussed.
RESULTS: The use of silver sulfide as a staining agent was found to be a fast and reliable approach which required basic sample preparation and provided excellent compositional contrast between the phases present in the nylon 6/MXD6 blends compared to the other staining agents.
CONCLUSIONS: The technique described in this paper is believed to be a novel and versatile method that has the potential to further improve the ability to study complex polymer blends where one polymer contains an aromatic ring.

Sequential injection and liquid chromatography for chemiluminescent detection of opiates

This thesis encompasses the development of analytical instrumentation, software and chemical methodologies for the rapid determination of pharmaceuticals in process extracts. Sensitive detection of morphine, codeine, oripavine and thebaine was achieved by measuring the quantity of light emitted as a result of their reactions with potassium permanganate and tris(2,2'-bipyridyl)ruthenium(III).

The design and evaluation of two types of chemical sensor

During the course of this investigation it was discovered that functionalised Ruthenium tris(bipyridyl) complexes exhibit different chemical, spectroscopic and electrochemical properties to those of the parent compound. Furthermore, it was possible to develop 1,8-naphthalimide-based compounds that furnished strong 1:1 host:guest complexes with larger anions such as hydrogen pyrophosphate. This dissertation presents in investigation into the systhesis and analytical evaluation of two types of chemical sensors: chemiluminescent and fluorescent.

Chemiluminescence from reactions with bis-cyclometalated iridium complexes in acidic aqueous solution

Chemical reactions between certain bis-cyclometalated iridium complexes, cerium(IV) and organic reducing agents in aqueous solution produce an emission of light which in some cases is more intense than that from analogous reactions with conventional ruthenium-based reagents, thus providing a new avenue for chemically-initiated luminescence detection.

Electrochemiluminescent monomers for solid support syntheses of Ru(II)-PNA bioconjugates : multimodal biosensing tools with enhanced duplex stability

The feasibility of devising a solid support mediated approach to multimodal Ru(II)-peptide nucleic acid (PNA) oligomers is explored. Three Ru(II)-PNA-like monomers, [Ru(bpy)2(Cpp-L-PNA-OH)]2+ (M1), [Ru(phen)2(Cpp-L-PNA-OH)]2+ (M2), and [Ru(dppz)2(Cpp-L-PNA-OH)]2+ (M3) (bpy = 2,2′-bipyridine, phen = 1,10-phenanthroline, dppz = dipyrido[3,2-a:2′,3′-c]phenazine, Cpp-L-PNA-OH = [2-(N-9-fluorenylmethoxycarbonyl)aminoethyl]-N-[6-(2-(pyridin-2yl)pyrimidine-4-carboxamido)hexanoyl]-glycine), have been synthesized as building blocks for Ru(II)-PNA oligomers and characterized by IR and 1H NMR spectroscopy, mass spectrometry, electrochemistry and elemental analysis. As a proof of principle, M1 was incorporated on the solid phase within the PNA sequences H-g-c-a-a-t-a-a-a-a-Lys-NH2 (PNA1) and H-P-K-K-K-R-K-V-g-c-a-a-t-a-a-a-a-lys-NH2 (PNA4) to give PNA2 (H-g-c-a-a-t-a-a-a-a-M1-lys-NH2) and PNA3 (H-P-K-K-K-R-K-V-g-c-a-a-t-a-a-a-a-M1-lys-NH2), respectively. The two Ru(II)-PNA oligomers, PNA2 and PNA3, displayed a metal to ligand charge transfer (MLCT) transition band centered around 445 nm and an emission maximum at about 680 nm following 450 nm excitation in aqueous solutions (10 mM PBS, pH 7.4). The absorption and emission response of the duplexes formed with the cDNA strand (DNA: 5′-T-T-T-T-T-T-T-A-T-T-G-C-T-T-T-3′) showed no major variations, suggesting that the electronic properties of the Ru(II) complexes are largely unaffected by hybridization. The thermal stability of the PNA·DNA duplexes, as evaluated from UV melting experiments, is enhanced compared to the corresponding nonmetalated duplexes. The melting temperature (Tm) was almost 8 °C higher for PNA2·DNA duplex, and 4 °C for PNA3·DNA duplex, with the stabilization attributed to the electrostatic interaction between the cationic residues (Ru(II) unit and positively charged lysine/arginine) and the polyanionic DNA backbone. In presence of tripropylamine (TPA) as co-reactant, PNA2, PNA3, PNA2·DNA and PNA3·DNA displayed strong electrochemiluminescence (ECL) signals even at submicromolar concentrations. Importantly, the combination of spectrochemical, thermal and ECL properties possessed by the Ru(II)-PNA sequences offer an elegant approach for the design of highly sensitive multimodal biosensing tools.

Selective excitation of concomitant electrochemiluminophores : tuning emission color by electrode potential

ECL in 3D: Selective electrogenerated chemiluminescence (ECL) of several ruthenium and iridium complexes simultaneously in solution can be controlled by electrode potential (see picture; λem=emission wavelength). These luminescent redox systems create a range of new possibilities for multi-analyte ECL detection, assessment of interdependent electrochemical/spectroscopic properties, and color tuning in light-emitting devices.

Evaluation of selected platinum group metal complexes as chemiluminescence reagents

This research extends the investigations into the chemiluminescence and electrochemiluminescence of platinum group metal reagents and their applications. The effect of the chemical nature of tris(2,2'-bipyridyl)ruthenium(II) and selected analogues on the chemiluminescence reaction is further explored, and this chemistry is extended to include novel iridium(III) and osmium(II) based chemiluminescence reagents.

Control of excitation and quenching in multi-colour electrogenerated chemiluminescence systems through choice of co-reactant

We demonstrate a new approach to manipulate the selective emission in mixed electrogenerated chemiluminescence (ECL) systems, where subtle changes in co-reactant properties are exploited to control the relative electron-transfer processes of excitation and quenching. Two closely related tertiary-amine co-reactants, tri-n-propylamine and N,N-diisopropylethylamine, generate remarkably different emission profiles: one provides distinct green and red ECL from [Ir(ppy)3] (ppy=2-phenylpyridinato-C2,N) and a [Ru(bpy)3](2+) (bpy=2,2'-bipyridine) derivative at different applied potentials, whereas the other generates both emissions simultaneously across a wide potential range. These phenomena can be rationalized through the relative exergonicities of electron-transfer quenching of the excited states, in conjunction with the change in concentration of the quenchers over the applied potential range.

Red-green-blue electrogenerated chemiluminescence utilizing a digital camera as detector

Exploiting the distinct excitation and emission properties of concomitant electrochemiluminophores in conjunction with the inherent color selectivity of a conventional digital camera, we create a new strategy for multiplexed electrogenerated chemiluminescence detection, suitable for the development of low-cost, portable clinical diagnostic devices. Red, green and blue emitters can be efficiently resolved over the three-dimensional space of ECL intensity versus applied potential and emission wavelength. As the relative contribution ratio of each emitter to the photographic RGB channels is constant, the RGB ECL intensity versus applied-potential curves could be effectively isolated to a single emitter at each potential.

Annihilation electrogenerated chemiluminescence of mixed metal chelates in solution : Modulating emission colour by manipulating the energetics

We demonstrate the mixed annihilation electrogenerated chemiluminescence of tris(2,2′-bipyridine)ruthenium(ii) with various cyclometalated iridium(iii) chelates. Compared to mixed ECL systems comprising organic luminophores, the absence of T-route pathways enables effective predictions of the observed ECL based on simple estimations of the exergonicity of the reactions leading to excited state production. Moreover, the multiple, closely spaced reductions and oxidations of the metal chelates provide the ability to finely tune the energetics and therefore the observed emission colour. Distinct emissions from multiple luminophores in the same solution are observed in numerous systems. The relative intensity of these emissions and the overall emission colour are dependent on the particular oxidized and reduced species selected by the applied electrochemical potentials. Finally, these studies offer insights into the importance of electronic factors in the question of whether the reduced or oxidized partner becomes excited in annihilation ECL. This journal is

Considering the chemical energy requirements of the tri-n-propylamine co-reactant pathways for the judicious design of new electrogenerated chemiluminescence detection systems

The introduction of a 'co-reactant' was a critical step in the evolution of electrogenerated chemiluminescence (ECL) from a laboratory curiosity to a widely utilised detection system. In conjunction with a suitable electrochemiluminophore, the co-reactant enables generation of both the oxidised and reduced precursors to the emitting species at a single electrode potential, under the aqueous conditions required for most analytical applications. The most commonly used co-reactant is tri-n-propylamine (TPrA), which was developed for the classic tris(2,2'-bipyridine)ruthenium(ii) ECL reagent. New electrochemiluminophores such as cyclometalated iridium(iii) complexes are also evaluated with this co-reactant. However, attaining the excited states in these systems can require much greater energy than that of tris(2,2'-bipyridine)ruthenium(ii), which has implications for the co-reactant reaction pathways. In this tutorial review, we describe a simple graphical approach to characterise the energetically feasible ECL pathways with TPrA, as a useful tool for the development of new ECL detection systems.

Iridium(III) N-heterocyclic carbene complexes: an experimental and theoretical study of structural, spectroscopic, electrochemical and electrogenerated chemiluminescence properties

Four cationic heteroleptic iridium(III) complexes have been prepared from methyl- or benzyl-substituted chelating imidazolylidene or benzimidazolylidene ligands using a Ag(I) transmetallation protocol. The synthesised iridium(III) complexes were characterised by elemental analysis, (1)H and (13)C NMR spectroscopy and the molecular structures for three complexes were determined by single crystal X-ray diffraction. A combined theoretical and experimental investigation into the spectroscopic and electrochemical properties of the series was performed in order to gain understanding into the factors influencing photoluminescence and electrochemiluminescence efficiency for these complexes, with the results compared with those of similar NHC complexes of iridium and ruthenium. The N^C coordination mode in these complexes is thought to stabilise thermally accessible non-emissive states relative to the case with analogous complexes with C^C coordinated NHC ligands, resulting in low quantum yields. As a result of this and the instability of the oxidised and reduced forms of the complexes, the electrogenerated chemiluminescence intensities for the compounds are also low, despite favourable energetics. These studies provide valuable insights into the factors that must be considered when designing new NHC-based luminescent complexes.