Effect of a dual-head short-stroke pump on post-column peroxyoxalate chemiluminescence detection

A dual-head short-stroke pump has two advantages in the post-column peroxyoxalate chemiluminescence (PO-CL) detection system. The first is to increase the mixing efficiency of solutions. The second is to increase the stability of the PO-CL reaction by keeping the aryl oxalate and hydrogen peroxide solutions separate. The detection sensitivities for six polycyclic aromatic hydrocarbons (PAHs) increased in the present system by using bis(2,4-dinitrophenyl) oxalate (DNPO) or bis(2,3,4,5,6-pentafluorophenyl) oxalate (PFPO) instead of such popular aryl oxalates as bis(2,4,6-trichlorophenyl) oxalate (TCPO) and bis[2-(3,6,9-trioxadecyloxycarbonyl)-4-nitrophenyl] oxalate (TDPO). Both DNPO and PFPO increased the sensitivities by factors of 4.1-10.2 and 3.5-8.1, respectively. In addition, DNPO was more stable than PFPO in acetonitrile. These results suggest that DNPO is the most useful aryl oxalate for the sensitive PO-CL detection of PAHs.     

Kinetics of two pathways in peroxyoxalate chemiluminescence

It has been shown that 1,1'-oxalyldiimidazole (ODI) is formed as an intermediate in the imidazole-catalyzed reaction of oxalate esters with hydrogen peroxide. Therefore, the kinetics of the chemiluminescence reaction of 1,1'-oxalyldiimidazole (ODI) with hydrogen peroxide in the presence of a fluorophore was investigated in order to further elucidate the mechanism of the peroxyoxalate chemiluminescence reaction. The effects of concentrations of ODI, hydrogen peroxide, imidazole (ImH), the general-base catalysts lutidine and collidine, and temperature on the chemiluminescence profile and relative quantum efficiency in the solvent acetonitrile were determined using the stopped-flow technique. Pseudo-first-order rate constant measurements were made for concentrations of either H2O2 or ODI in large excess. All of the reaction kinetics are consistent with a mechanism in which the reaction is initiated by a base-catalyzed substitution of hydrogen peroxide for imidazole in ODI to form an imidazoyl peracid (Im(CO)2OOH). In the presence of a large excess of H2O2, this intermediate rapidly decays with both a zero- and first-order dependence on the H2O2 concentration. It is proposed that the zero-order process reflects a cyclization of this intermediate to form a species capable of exciting a fluorophore via the "chemically initiated electron exchange mechanism" (CIEEL), while the first-order process results from the substitution of an additional molecule of hydrogen peroxide to the imidazoyl peracid to form dihydroperoxyoxalate, reducing the observed quantum yield. Under conditions of a large excess of ODI, the reaction is more than 1 order of magnitude more efficient at producing light, and the quantum yield increases linearly with increasing ODI concentration. Again, it is proposed that the slow initiating step of the reaction involves the substitution of H2O2 for imidazole to form the imidazoyl peracid. This intermediate may decay by either cyclization or by reaction with another ODI molecule to form a cyclic peroxide that is much more efficient at energy transfer with the fluorophore. The reaction kinetics clearly distinguishes two separate pathways for the chemiluminescent reaction.     

A new sensitive determination method of estradiol in plasma using peroxyoxalate ester chemiluminescence combined with an HPLC system

A new sensitive determination method of estradiol in a plasma sample using peroxyoxalate ester chemiluminescence was developed. Estradiol, which was extracted by liquid-liquid extraction using ethyl acetate from plasma, was derivatized with dansyl-chloride (DNS-Cl) and separated by reverse-phase HPLC. The performance of four oxalates, bis(trichlorophenyl)oxalate (TCPO), bis(2,4-dinitrophenyl)oxalate (DNPO), bis(pentafluorophenyl)oxalate (PFPO), and bis[4-nitro-2-(3,6, 9-trioxadecyloxycarbonyl)phenyl] oxalate (TDPO), were evaluated using the static system, and DNPO was found to have the most sensitive and stable chemiluminescence at a H(2)O(2) concentration of 30 mM. HPLC-chemiluminescence system using DNPO for the determination of estradiol was established. The detection limit of dansylated-estradiol (DNS-E2) was 15 fmol (4 pg) in the standard solution and 44 fmol (12 pg) in the rat plasma sample at S/N = 3.     

Chemiluminescence detection in capillary electrophoresis using an ultra-fast co-catalyzed peroxyoxalate chemiluminescent reaction and electrokinetic reagent delivery

Summary Despite the impressive limits of detection and inherent selectivity afforded by peroxyoxalate chemiluminescence (POCL) detection, efficient coupling of POCL to capillary electrophoresis (CE) remains limited by the relatively slow kinetics of the reactions that drive imidazole-catalyzed chemiluminescence. Moreover, oxalate esters, used in POCL, are sparingly soluble in polar solvents and hydrolyze rapidly, presenting an additional challenge with respect to detection following aqueous phase separations. In this paper, a novel method for coupling an ultrafast POCL reaction to CE is presented. Post separation electrokinetic delivery of the POCL reagent bis(2,4,6-trichlorophenyl)oxalate (TCPO) was accomplished using a commercially available micro tee. Electrokinetic addition of TCPO allowed for precise control of the ratio of TCPO to the chemiluminescence (CL) reagents 1,2,2,6,6-pentamethylpiperidine (PMP) and 1,2,4-triazole (triazole), spiked into the running buffer. This novel method for CL reagent delivery avoided the problems and costs associated with using pressure or mechanical pumps to deliver reagents post separation. Use of this dual-component system (PMP and triazole) resulted in intense CL with half-lives of less than 2 seconds. Optimum conditions for CE-POCL detection were investigated using stopped-flow kinetics. The detection limit for 3-aminofluoranthene, following separation by CE, was<0.95 nM.     

A study of peroxyoxalate-chemiluminescence of 4,4'-bis{[4,6-bis (2-hydroxyethyl)amino-1,3,5-triazin-2-yl]amino}stilbene-2,2'-disulfonic acid-disodium salt as a novel blue fluorescer

The chemiluminescence arising from the reaction of bis(2,4,6-trichlorophenyl)oxalate (TCPO) with hydrogen peroxide in the presence of brightener 4,4'-bis{[4,6-bis(2-hydroxyethyl)amino-1,3,5-triazin-2-yl]amino}stilbene-2,2'-disulfonic acid-disodium salt (Triazinyl) has been studied. The influence of concentration of TCPO, hydrogen peroxide, Triazinyl, base catalysts and temperature on the resulting chemiluminescence was investigated. The kinetic parameters for the peroxyoxalate-chemiluminescence (PO-CL) of Triazinyl were evaluated from computer fitting of the resulting intensity-time plots. The activation energies, E(a), were evaluated from temperature dependence of the corresponding rise and fall rate constants.     

化学发光免疫分析检测人血清中的癌胚抗原

基于辣根过氧化物酶(HRP)催化H2O2氧化3-(4-羟苯基)丙酸(PHPPA),生成能发荧光的3-(4-羟苯基)丙酸二聚体.在乙腈介质中,在增强剂眯唑参与下,与双[2,4,6-三氯苯基]草酸酯(TCPO)和H2O2反应产生强化学发光.用辣根过氧化物酶(HRP)标记癌胚抗原(CEA)单克隆抗体,通过CEA的双抗夹心免疫...     

Chemiluminescence of bis(2,4,6-trichlorophenyl) oxalate in aqueous micellar systems

The chemiluminescent reaction of bis(2,4,6-trichlorophenyl) oxalate (TCPO) in aqueous micellar systems is compared with the reaction in a mixture of acetonitrile and aqueous phosphate buffer. The chemiluminescence was studied in batch experiments with perylene as the fluorophore. The oxidation of TCPO produced the same intensity of chemiluminescence in the buffered acetonitrile as in Arkopal N-300 micelles, the best micellar system. The solubility of TCPO in an aqueous micellar system is greater than that in the acetonitrile/aqueous buffer (80:20, v/v), but TCPO is less stable in the former system.     

Solution kinetics of the degradation of the chemiluminescent reagent bis(2,4-dinitrophenyl) oxalate in water/acetonitrile

Simultaenous ultraviolet absorbance measurements at 240 and 260 nm are used to quantify DNPO and its principle degradation product 2,4-dinitrophenol. The stability of DNPO was determined in various water acetonitrile mixtures (23±0.5°C). The decomposition follows (pseudo)- first-order kinetics in each system, and is third order in water concentration. An Arrhenius plot was used to obtain estimates for the activation energy, activation enthalphy, and activation entropy.     

Electroreduction of Ru(III) Oxalate Complexes on DME at Variable Supporting-Electrolyte Concentration

The recharging of Ru(III) oxalate complexes is studied on DME in mixed sulfate–oxalate electrolytes of variable concentration. The discovered deceleration of the process with decreasing supporting-electrolyte concentration qualitatively agrees with the expected effect of the EDL structure on the recharging kinetics, but the obtained quantitative data are at severe variance with theory. At low supporting-electrolyte concentrations the process rate in freshly-prepared solutions depends on the concentration of oxalate ions. The dependence has nothing to do with trioxalate complexes of Ru(III) coexisting in the bulk solution with Ru(III) complexes, which have a reduced number of coordinated ligands, as such complexes emerge only after 2–3 days of storing the solutions. The most probable factor responsible for such a dependence seems to be a volume reaction of charge transfer from the formed Ru(II) complexes onto trioxalate complexes of Ru(III). The reaction has a catalytic effect on the hydration of the latter and seems to be responsible for the discrepancy between experiment and theory.     

Parameters Affecting the Peroxyoxalate Chemiluminescence

ABSTRACT

A careful study of the parameters affecting the chemiluminescent reaction of TCPO (bis(2,4,6-trichlorophenyl)oxalate) and 2-NPO (bis(2-nitrophenyl)oxalate) with hydrogen peroxide, in the presence of imidazole (used as buffer and catalyst) and the fluorophore 3-AFA (3-aminofluoranthene), was carried out in acetonitrile/water medium. The data are reported in terms of the time (t_Imax) required for the relative maximum chemiluminescence intensity (I_max) and the area (A) under the curve of intensity νs. time. At controlled acidity and high unprotonated imidazole concentration ([IMI] = 1x10^?2 mol.L^?1), the I_max and t_Imax values do not depend on the acetonitrile/water ratio. The CL intensity is maximum at around pH 6.0 (higher buffer capacity). For 1x10^?2 < [IMI] < 1x10^?4 mol.L^?1, the area is largest when [IMI] = 1x10^?3 mol.L^?1 and linearly dependent on the hydrogen peroxide concentration (10^?5 ? 10^?3 mol.L^?1). The area is also enhanced by increasing the fluorophore concentration. The acidity controls the unprotonated imidazole and H⁺ concentration. Several errors can arise from quantitative analyses carried out without control of the HIMI⁺ and IMI concentrations.     

Mechanistic information from low-temperature rapid-scan and NMR measurements on the protonation and subsequent reductive elimination reaction of a (diimine)platinum(II) dimethyl complex

A detailed kinetic study of the protonation and subsequent reductive elimination reaction of a (diimine)platinum(II) dimethyl complex was undertaken in dichloromethane over the temperature range of -90 to +10 degrees C by stopped-flow techniques. Time-resolved UV-vis monitoring of the reaction allowed the assessment of the effects of acid concentration, coordinating solvent (MeCN) concentration, temperature, and pressure. The second-order rate constant for the protonation step was determined to be 15200 +/- 400 M(-1) s(-1) at -78 degrees C, and the corresponding activation parameters are DeltaH = 15.2 +/- 0.6 kJ mol(-1) and DeltaS = -85 +/- 3 J mol(-1) K(-1), which are in agreement with the addition of a proton that results in the formation of the platinum(IV) hydrido complex. The kinetics of the second, methane-releasing reaction step do not show an acid dependence, and the MeCN concentration also does not significantly affect the reaction rate. The activation parameters for the second reaction step were found to be DeltaH = 75 +/- 1 kJ mol(-1), DeltaS = +38 +/- 5 J mol(-1) K(-1), and DeltaV = +18 +/- 1 cm(3) mol(-1), strongly suggesting a dissociative character of the rate-determining step for the reductive elimination reaction. The spectroscopic and kinetic observations were correlated with NMR data and assisted the elucidation of the underlying reaction mechanism.     

A study of chemiluminescence from reaction of bis(2,4,6-trichlorophenyl)oxalate, hydrogen peroxide and diethyl-2-(cyclohexylamino)-5-[(E)-2-phenyl-1-ethenyl]-3,4-furandicarboxylate as a novel fluorescer

The chemiluminescence (CL) arising from reaction of bis(2,4,6-trichlorophenyl)oxalate (TCPO) with hydrogen peroxide in the presence of a diethyl-2-(cyclohexylamino)-5-[(E)-2-phenyl-1-ethenyl]-3,4-furandicarboxylate as a novel fluorescer (Flu) has been studied. The relationship between the chemiluminescence intensity and concentrations of TCPO, sodium salicylate, hydrogen peroxide and fluorescer is reported. The chemiluminescence parameters including intensity at maximum CL, time at maximum intensity, total light yield, theoretical maximum level of intensity and pseudo-first-order rate constants for the rise and fall of the CL burst (k_r and k_f) were evaluated from computer fitting of the resulting intensity-time plots. The activation parameters E_a, ΔH^Δ, ΔS^Δ and ΔG^Δ for the rise and fall steps were evaluated from the temperature dependence of k_r and k_f values.     

Studies on the effects of imidazole on the peroxyoxalate chemiluminescence detection system for high performance liquid chromatography

The catalytic effect of bases (imidazole, pyridine, Tris and triethylamine) on the peroxyoxalate chemiluminescence (PO-CL) reaction for high performance liquid chromatography (HPLC) was investigated. Imidazole increased PO-CL intensity extraordinarily, whereas the other bases (pyridine, Tris and triethylamine) did not. The peak heights of dipyridamole (coronary vasodilator) obtained using the eluents containing buffers were largest at pH 7.0, a few times less at pH 6.0 and pH 5.0, 100 times less at pH 4.0 and a few hundred times less at pH 3.0. The eluents containing buffers at pH 3, 4, 5, 6 or 7 each with imidazole increased the peak heights by a few to ten times as compared with those without imidazole, and those peak heights were within one order of magnitude. On the other hand, the eluent containing buffer at pH 2 did not affect the peak heights with or without imidazole. Bis(4-nitro-2-(3,6,9-trioxadecyloxycarbonyl)phenyl) oxalate (TDPO) alone and bis(2,4-dinitrophenyl)oxalate (DNPO) plus TDPO were recommended to be used against eluents containing buffers of pH 5-7 and pH 3-4, respectively. Dipyridamole and benzydamine hydrochloride (anti-inflammatory drug) were separated on the ODS column and detected by the present system. The detection limits of dipyridamole and benzydamine hydrochloride were 40 amol and 270 fmol, respectively.     

Thermodynamic and kinetic studies on the reaction between the vitamin B12 derivative beta-(N-methylimidazolyl)cobalamin and N-methylimidazole: ligand displacement at the alpha axial site of cobalamins

The equilibria and kinetics of substitution of the 5,6-dimethylbenzimidazole at the alpha site of beta-(N-methylimidazolyl)cobalamin by N-methylimidazole have been investigated, and the product, bis(N-methylimidazolyl)cobalamin, has been characterized by visible and 1H NMR spectroscopies. The equilibrium constant for (N-MeIm)Cbl+ + N-MeIm right harpoon over left harpoon (N-MeIm)2Cbl+ was determined by 1H NMR spectroscopy (9.6 +/- 0.1 M(-1), 25.0 degrees C, I = 1.5 M (NaClO4)). The observed rate constant for this reaction exhibits an unusual inverse dependence on N-methylimidazole concentration, and it is proposed that substitution occurs via a base-off solvent-bound intermediate. Activation parameters typical for a dissociative ligand substitution mechanism are reported at two different N-MeImT concentrations, 5.00 x 10(-3) M (DeltaH++ = 99 +/- 2 kJ x mol(-1), DeltaS++ = 39 +/- 5 J x mol(-1) x K(-1), DeltaV++ = 15.0 +/- 0.7 cm3 x mol(-1), and 1.00 M (DeltaH++ = 109.4 +/- 0.8 kJ x mol(-1), DeltaS++ = 70 +/- 3 J x mol(-1) x K(-1), DeltaV++ = 16.8 +/- 1.1 cm3 x mol(-1)). According to the proposed mechanism, these parameters correspond to the equation of (N-MeIm)2Cbl+ and the ring-opening reaction of the alpha-DMBI of (N-MeIm)Cbl+ to give the solvent-bound intermediate in both cases, respectively.     

Fast peroxyoxalate chemiluminescence for minimized analytical separation systems

The maximum intensity, Imax, and time required to reach the maximum emission, taumax, for 1-aminopyrene monitored in 1,1'-oxalyldi-4-methylimidazole (OD4MI) chemiluminescence (CL) reactions are approximately 61 times higher and 16 times faster than their respective values for bis(2,4,6-trichlorophenyl)oxalate (TCPO) CL reactions in the presence of imidazole (ImH).     

Quenching effect of some heavy metal ions on the fast peroxyoxalate-chemiluminescence of 1-(dansylamidopropyl)-1-aza-4,7,10-trithiacyclododecane as a novel fluorophore

The fast chemiluminescence (CL) arising from the reaction of bis(2,4,6-trichlorophenyl)oxalate (TCPO) with hydrogen peroxide in the presence of 1-(dansylamidopropyl)-1-aza-4,7,10-trithiacyclododecane (L) as a novel fluorophore, and imidazole as catalyst, has been studied in ethyl acetate solution. The relationships between the chemiluminescence intensity and concentrations of TCPO, imidazole, hydrogen peroxide and L are reported. In the presence of imidazole as catalyst, the entire CL signal was completed in less than 3 s. The quenching effect of Cu²⁺, Pb²⁺, Cd²⁺, Hg²⁺ and Ag⁺ ions on the chemiluminescent system was investigated, the resulting Stern–Volmer plots were obtained and the K_Q values were calculated. It was found that the quenching effect of metal ions on the chemiluminescence of L decreases in the order Cu²⁺ > Pb²⁺ > Cd²⁺ > Hg²⁺ > Ag⁺.     

流动注射化学发光植物组织传感器测定草酸盐

草酸是尿道结石主要成因之一 .统计结果表明 ,90 %以上结石均含草酸钙 .回肠病、口角性肠胃炎及脂肪吸收不良均可引起尿液中草酸的增加 .草酸盐的测定在临床上具有重要意义 .微量草酸测定的传统方法是变色酸比色法或偶氮化合物比色法[1 ] .测定草酸盐的方法还有原子吸收光谱法[2 ] 、高效液相色谱法[3] 、离子色谱法[4] 、光度法[5] 和草酸氧化酶法[6] 等 .这些方法或操作复杂、耗时 ,或灵敏度低 ,使其应用受到限制 .本文提出一种测定草酸盐的新方法 ,其原理为草酸 +Ｏ2草酸氧化酶 ＣＯ2 +Ｈ2 Ｏ2 ,Ｌｕｍｉｎｏｌ+Ｈ2 Ｏ2 ｈｖ　　将含有草…     

Solvent effect on the adduct formation of methyltrioxorhenium (MTO) and pyridine: enthalpy and entropy contributions

1:1 adduct formation between methyltrioxorhenium (MTO) and pyridine in different solvents (n-hexane, benzene, chloroform, ethyl acetate, dichloromethane and acetone) was studied using spectrophotometric techniques. The formation constants were determined from the absorbance change of the adduct versus pyridine concentration. The values of the formation constants vary from 114.5 to 752.5 L mol(-1) at T= 20 degrees C depending on the dielectric constant of the solvent (epsilon(r) = 1.89-20.7). Enthalpy and entropy changes during the adduct formation reactions were determined from van't Hoff plots. The measured enthalpy change of -37.0 to -22.2 kJ mol(-1) depends on epsilon(r), which is explained by Onsager's reaction field theory. The measured entropy change ranges from -71.2 to -36.6 J K(-1) mol(-1), and the dependence on the solvent is discussed in terms of the solvation effect.     

聚乙二醇(PEG)桥连的新型双N-杂环卡宾-膦的合成及其在水相Suzuki反应中的应用

通过乙酸1-(2-二苯膦基二茂铁基)乙基酯与PEG-400衍生的双咪唑化合物反应,制得新型PEG桥连的双咪唑盐-膦配体,其结构经1HNMR,<31>PNMR和MS鉴定.初步催化研究表明,该PEG桥连的双咪唑盐一膦可作为支持配体在有机和水相中高产率地实现Pd催化的溴代芳烃和苯硼酸的Suzuki偶联反应.     

First Synthesis of Bis(di(indolyl)aryl)methanes From Bis(salicylaldehydes)

In this article, a simple method for the synthesis of bis(di(indolyl)aryl)methanes is described. The iodine‐catalyzed (5 mol %) reaction of indoles with various bis(salicylaldehyde) derivatives affords the bis(di(indolyl)aryl)methanes in excellent yields. The reaction works well under mild reaction condition with shorter reaction time.