Development of a Potential-Modulated Electrochemiluminescence Measurement System for Selective and Sensitive Determination of the Controlled Drug Codeine.

Codeine is a common analgesic drug that is a pro-drug of morphine. It also has a high risk of abuse as a recreational drug because of its extensive distribution as an OTC drug. Therefore, sensitive and selective screening methods for codeine are crucial in forensic analytical chemistry. To date, a commercial analytical kit has not been developed for dedicated codeine determination, and there is a need for an analytical method to quantify codeine in the field. In the present work, potential modulation was combined with electrochemiluminescence (ECL) for sensitive determination of codeine. The potential modulated technique involved applying a signal to electrodes by superimposing an AC potential on the DC potential. When tris(2,2'-bipyridine)ruthenium(II) ([Ru(bpy)3]2+) was used as an ECL emitter, ECL activity was confirmed for codeine. A detailed investigation of the electrochemical reaction mechanism suggested a characteristic ECL reaction mechanism involving electrochemical oxidation of the opioid framework. Besides the usual ECL reaction derived from the amine framework, selective detection of codeine was possible under the measurement conditions, with clear luminescence observed in an acidic solution. The sensitivity of codeine detection by potential modulated-ECL was one order of magnitude higher than that obtained with the conventional potential sweep method. The proposed method was applied to codeine determination in actual prescription medications and OTC drug samples. Codeine was selectively determined from other compounds in medications and showed good linearity with a low detection limit (150 ng mL-1).

Sensitive screening of methamphetamine stimulant using potential-modulated electrochemiluminescence.

Methamphetamine (MA) is one of the most commonly abused recreational stimulants; thus, rapid and sensitive screening methods for MA are of great importance in forensic analytical chemistry. In the present work, potential modulation was combined with electrochemiluminescence (ECL) for the sensitive determination of MA. The potential modulated (PM) technique involved applying a signal to electrodes by superimposing an alternating current potential on the direct current potential. When tris(2,2'-bipyridine)ruthenium(II) (Ru(bpy)32+) was used as an ECL emitter, the sensitivity of MA detection by PM-ECL was over 100 times that obtained with in conventional potential sweep mode. The radical on the α-carbon of the amine moiety is thought to play an important role in the ECL reaction mechanism involving amine-containing species. However, in the case of MA-type stimulants, density functional theory calculations suggest that the generated α-carbon radicals induce further intramolecular proton transfer. On the basis of the proposed ECL reaction route, we clarified the conditions under which MA could be selectively detected in the presence of the similar substance methoxyphenamine. The proposed method was applied to MA determination in a spiked human urine sample and showed good linearity with a low detection limit (100 nM, ca. 15 ng mL-1).

Electrochemiluminescence of Tris(2,2'-bipyridine)ruthenium(II)/Tri-n-propylamine with an Electric Contactless Power Transfer System.

An electrochemiluminescence (ECL) analytical device was developed using an electric contactless power transfer system. A mutually induced electromotive voltage was generated by wrapping an enameled wire around a commercial contactless charger. There was no electrical contact between the power supply and the electrochemical cell. For the tris(2,2'-bipyridine)ruthenium(II) (Ru(bpy)32+)/tri-n-propylamine system, a weak ECL signal was observed. When an inexpensive rectifier diode was introduced between the coil and the working electrode, the ECL intensity detection sensitivity increased by more than 100 times. The relationship between the waveform of the applied voltage and the ECL response was clarified, and the optimum conditions were determined. The intensity of the induced electromotive voltage was easily controlled by changing the number of turns in the coil. The proposed method is a safe, simple, and inexpensive technique without electrical contact.

Sonochemiluminescence of lucigenin using amines as coreactant: Reactivity and mechanism studies.

Sonochemiluminescence (SCL) from aqueous solution of lucigenin (Luc2+) has been studied using aliphatic amines as coreactant. The SCL intensity are strongly dependent on the dissolved gases such as air, oxygen, nitrogen and argon. The most strong SCL signals are observed from oxygen saturated alkaline solution containing Luc2+ when small amount of trialkylamine, such as tripropylamine (TPrA) was added into the solution. In an ultrasonic field, TPrA can adsorb onto the cavitation bubble/solution interface where TPrA is oxidized by OH to form a radical cation TPrA+ and subsequently produce a highly reducing TPrA species through a deprotonation reaction of the TPrA+. TPrA is suggested to initiate the reduction reactions of Luc2+ and molecule oxygen to produce Luc+ and superoxide radical anion (O2-), respectively. The radical-radical coupling reaction between Luc+ and O2- is expected to initiate the light emission. The production of O2- is examined by spectrofluorometric method using 2-(2-pyridyl)benzothiazoline as a fluorescent probe. The results show that the production of O2- by ultrasound was more efficient in oxygen saturated solution in the presence of coreactants, consistent with the results with SCL measurements.

Anodic Electrochemiluminescence of CdTe Quantum Dots Using Tripropylamine as Coreactant: Size-dependent Effect.

The quantum size effect of CdTe quantum dots (QDs) has been one of the targets of extensive research concerning the optical spectroscopy of semiconductors, but little is known about their effects on electrochemiluminescence (ECL) behavior, especially in the anodic potential range. In this present study, water-soluble CdTe QDs with different sizes were synthesized with a microwave-assisted hydrothermal method. Upon electrochemical oxidation of the CdTe QD in the presence of tri-n-propylamine (TPrA) as a coreactant, two ECL signals, called ECL1 and ECL2, were observed at potentials corresponding to the oxidation of TPrA (at +0.8 V) and CdTe QDs (at +1.2 V), respectively. The relative intensity of ECL1 significantly increased with increasing the particle size of CdTe QDs, and disappeared when the particle size was less than 2.4 nm. Upon an anodic potential of +0.8 V, TPrA is oxidized at the electrode surface, where the intermediate radical species like TPrA•+ radical cation and CdTe QDs•- radical anion are supposed to be formed to give the excited chemical species of CdTe QDs*. Possible ECL mechanisms are proposed from a view point of thermodynamics.

Potential-modulated electrochemiluminescence of a tris(2,2'-bipyridine)ruthenium(II) / lidocaine system under 430 kHz ultrasound irradiation.

The electrochemiluminescence (ECL) of tris(2,2'-bipyridine)ruthenium(II) (Ru(bpy)32+) in the presence of lidocaine was investigated under ultrasound (US) irradiation. The sonoelectrochemical experiments are conducted by indirect irradiation of ultrasound with a piezoelectric transducer operating at 430 kHz. In a supporting electrolyte at pH 11, the Ru(bpy)32+/lidocaine system gave weak ECL peaks around +1.2 V and +1.45 V, respectively. The ECL signal at +1.2 V was attributed to redox reactions of the oxidative intermediates of Ru(bpy)32+ and lidocaine, while the signal at +1.45 V was assumed to be caused by an advanced oxidation process due to the generation of hydroxyl radicals (OH) at the electrode surface. In this study, the potential modulation approach is employed in the study of ECL process upon US irradiations because it can suppress the noise components from sonoluminescence effectly and improve the resolution of ECL-potential profiles. It is found ECL signals were greatly enhanced upon US irradiation at the output power of 30 W, however, the relative intensity of ECL signal at +1.2 V was larger than that obtained with a rotating disk electrode even though the mass transport effect is equilvalent. The experiment results suggest that the chemical effect (i.e., generation of OH) by 430 kHz US becomes remarkable in the electrochemical process. Detailed ECL reaction routes under US are proposed in this study.

Phloretin protects against cardiac damage and remodeling via restoring SIRT1 and anti-inflammatory effects in the streptozotocin-induced diabetic mouse model.

Diabetic cardiomyopathy increases the risk of heart failure independent of coronary artery disease and hypertension. Phloretin (PHL) shows anti-inflammatory effects in macrophages. In this study, we explored the protective effects of PHL on high glucose (HG)-induced injury in diabetic cardiomyopathy in vivo and in vitro. Using streptozotocin-induced diabetic mouse model and incubating cardiac cells line under a HG environment, PHL were evaluated of the activities of anti-inflammation and anti-fibrosis. In the study, PHL treatment ameliorated cardiomyocyte inflammation injury, and reduced fibrosis in vivo and in vitro. PHL also improved cardiac biochemical criterions after 8 weeks of induction of diabetes in C57BL/6 mice. Molecular docking results indicated that silent information regulator 2 homolog 1 (SIRT1) bound to PHL directly and that SIRT1 expression was upregulated in the PHL-treated group in HG-induced H9C2 cells. Protective effect of PHL was been eliminated in silence SIRT1 H9C2 cells. Taken together, these results suggested that PHL suppressed HG-induced cardiomyocyte injury via restoring SIRT1 expression.

Genome-wide dissection of segregation distortion using multiple inter-subspecific crosses in rice.

Mendelian inheritance can ensure equal segregation of alleles from parents to offspring, which provides fundamental basis for genetics and molecular biology. Segregation distortion (SD) leads to preferential transmission of certain alleles from generation to generation. Such violation of Mendelian genetic principle is often accompanied by reproductive isolation and eventually speciation. Although SD is observed in a wide range of species from plants to animals, genome-wide dissection of such biased transmission of gametes is rare. Using nine inter-subspecific rice crosses, a genome-wide screen for SD loci is performed, which reveals 61 single-locus quantitative trait loci and 194 digenic interactions showing distorted transmission ratio, among which 24 new SD loci are identified. Biased transmission of alleles is observed in all nine crosses, suggesting that SD exists extensively in rice populations. 72.13% distorted regions are repeatedly detected in multiple populations, and the most prevalent SD hotspot that observed in eight populations is mapped to chromosome 3. Xian alleles are transmitted at higher frequencies than geng alleles in inter-subspecific crosses, which change the genetic composition of the rice populations. Epistatic interaction contributes significantly to the deviation of Mendelian segregation at the whole-genome level in rice, which is distinct from that in animals. These results provide an extensive archive for investigating the genetic basis of SD in rice, which have significant implications in understanding the reproductive isolation and formation of inter-subspecific barriers during the evolution.

Sonochemical preparation of gold nanoparticles for sensitive colorimetric determination of nereistoxin insecticides in environmental samples.

A simple colorimetric method using gold nanoparticles (AuNPs) was developed as an efficient strategy for specific and sensitive detection of insecticides that are analogs of nereistoxin (NRT). The AuNPs were synthesized by a surfactant-free sonochemical reaction with ultrasonication at 430 kHz. A color change occurred in the presence of NRT because the AuNPs aggregated if they were coated with a small amount of thioctic acid (TA). At a pH of around 5, the TA adsorbed on the AuNPs was deprotonated, whereas NRT was protonated (NRT-H+). Adsorption of NRT-H+ onto the TA-coated AuNPs surface would decrease the surface charge of the AuNPs, and this resulted in aggregation. Because the aggregation of the TA-coated AuNPs could not be induced by amine compounds without thiol groups, this provided a surface-limited aggregation mechanism for specific sensing of NRT. The absorbance at 700 nm was dependent on the concentration of NRT, and the calibration curve was linear over the concentration range 85 nM (12 ng/mL) to 1000 nM (140 ng/mL). The applicability of the proposed method to detection of trace levels of NRT in environmental water samples was successfully demonstrated using a simple liquid-liquid reverse extraction technique.

Wide-Range Near-Infrared Sensitizing 1 H-Benzo[ c, d]indol-2-ylidene-Based Squaraine Dyes for Dye-Sensitized Solar Cells.

NIR absorbing squaraine dyes SQ1-SQ7 having 1 H-benzo[ c, d]indol-2-ylidene as a donor moiety were designed for application in DSSCs. Annulation of the benzene ring to an 3 H-indolium-based anchor moiety led to a red-shifted and broadened absorption band on TiO2 film, which were reflected in the improved short-circuit current density of SQ2 (6.22 mA cm-2) compared to the nonbenzene fused derivative SQ1 (4.39 mA cm-2). Although the introduction of a butoxy (SQ4: 806 nm) or dialkylamino group (SQ5-SQ7: 815-820 nm) to the 1 H-benzo[ c, d]indol-2-ylidene-based donor moiety resulted in red-shifted absorption maxima in ethanol compared to the nonsubstituted derivative SQ2 (784 nm), the HOMO energy level of SQ4-SQ7 gave rise to an undesirable approximation to the redox potential of I-/I3-. Thus, the butoxy (SQ4: 0.56) and dialkylamino (SQ5-SQ7: 0.25-0.30) derivatives had relatively lower conversion efficiencies. Since the 2-ethylhexyl derivative SQ3 exhibited red-shifted absorption (λmax: 796 nm), suitable HOMO and LUMO energy levels, and relatively efficient restriction of charge recombination, this dye achieved the highest conversion efficiency (1.31%), along with a high IPCE response of over 20% over a wide range from 640 to 860 nm and an onset of IPCE at 1000 nm.

Electrochemical Determination of Chromium(VI) in River Water with Gold Nanoparticles-Graphene Nanocomposites Modified Electrodes.

In this study, nanocomposites of ligand-free gold nanoparticles that are anchored onto the graphene surface (Graphene/AuNPs) were synthesized by a sonochemical method in a single reaction step. A highly sensitive amperometric sensor using Graphene/AuNPs is proposed for the determination of trace hexavalent chromium Cr(VI) in environmental water samples. Compared with a gold electrode, a glassy carbon electrode and a AuNPs modified glassy carbon electrode, the Graphene/AuNPs modified glassy carbon electrode exhibits the highest electrocatalytic activity and stability towards the reduction of Cr(VI), based on the results by cyclic voltammetry and electrochemical AC impedance studies. This study shows that the Graphene/AuNPs-based sensor can detect Cr(VI) with a low detection limit of 10 nM (∼0.5 µg/L), a wide dynamic range of 0 to 20 µM (R = 0.999) and very good selectivity and reproducibility. The electrode is applied to the determination of Cr(VI) in river samples with satisfactory recovery values.

Phloretin Prevents Diabetic Cardiomyopathy by Dissociating Keap1/Nrf2 Complex and Inhibiting Oxidative Stress.

Hyperglycemia induces chronic inflammation and oxidative stress in cardiomyocyte, which are the main pathological changes of diabetic cardiomyopathy (DCM). Treatment aimed at these processes may be beneficial in DCM. Phloretin (PHL), a promising natural product, has many pharmacological activities, such as anti-inflammatory, anticancer, and anti-oxidative function. The aim of this study was to investigate whether PHL could ameliorate the high glucose-mediated oxidation, hypertrophy, and fibrosis in H9c2 cells and attenuate the inflammation- and oxidation-mediated cardiac injury. In this study, PHL induced significantly inhibitory effect on the expression of pro-inflammatory, hypertrophy, pro-oxidant, and fibrosis cytokines in high glucose-stimulated cardiac H9c2 cells. Furthermore, PHL decreased the levels of serum lactate dehydrogenase, aspartate aminotransferase, and creatine kinase-MB, and attenuated the progress in the fibrosis, oxidative stress, and pathological parameters via Kelch-like ECH-associated protein 1 (Keap1)/nuclear factor E2-related factor 2 (Nrf2) pathway in diabetic mice. In additional, molecular modeling and immunoblotting results confirmed that PHL might obstruct the interaction between Nrf2 and Keap1 through direct binding Keap1, and promoting Nrf2 expression. These results provided evidence that PHL could suppress high glucose-induced cardiomyocyte oxidation and fibrosis injury, and that targeting Keap1/Nrf2 may provide a novel therapeutic strategy for human DCM in the future.

Anodic Stripping Voltammetry for the Determination of Trace Cr(VI) with Graphite/Styrene-Acrylonitrile Copolymer Composite Electrodes.

A square-wave anodic stripping voltammetry (SWASV) for the determination of trace amounts of hexavalent chromium Cr(VI) at a graphite/styrene-acrylonitrile (Graphite-SAN) copolymer composite electrode is described. This method involves a preconcentration step whereby the trace Cr(VI) was cathodically reduced to Cr(III) on an electrode surface in an acetate buffer (pH 5), followed by an anodic stripping technique with a square-wave voltammetric mode. It has been shown that the analytical sensitivity is significantly improved at the Graphite-SAN copolymer composite electrode in comparison with the conventional glassy carbon electrode, due to the strong interaction between Cr(III) and the nitrile end group of the SAN copolymer. The SWASV response was characterized with respect to the pH, deposition potential, possible interferences, etc. Under the optimal conditions, the stripping peak height linearly increased with the concentration of Cr(VI) in a range from 0 to 150 ng mL-1 with a correlation coefficient of 0.997, and a detection limit of 4.2 ng mL-1 was achieved based on signal-to-noise ratio of about 3. The Graphite-SAN composite electrode exhibited some interesting advantages, such as high mechanical rigid, easy surface renewable, higher sensitivity and better peak resolution in comparison with the results at conventional glassy carbon electrodes. They have been applied to the determination of Cr(VI) in real water samples with satisfactory recoveries.

Development and application of ultrasound-assisted microextraction to analysis of fenitrothion in environmental samples.

A microextraction technique based on ultrasonic emulsification and demulsification was developed for detecting pesticides at trace levels in environmental water samples. In this ultrasound-assisted microextraction (UAME), chloroform was emulsified with an aqueous sample solution containing trace fenitrothion (MEP) by ultrasonic irradiation (48 kHz) for 5 min. The emulsion was then demulsified by ultrasonic irradiation (2.4 MHz) for 10 min. This resulted in phase separation of the water and chloroform without centrifugation. The demulsified chloroform was collected by a microsyringe and submitted to gas chromatography-mass spectrometry. In conventional extraction with mechanical stirring, the extraction recovery (ER) of MEP was strongly dependent on the sample/chloroform volume ratio. However, in UAME, the ER was independent of the volume ratio and the ER was >80 % when the enrichment factor was 40. In UAME, MEP was rapidly extracted into the chloroform because of the large specific surface areas of the small chloroform droplets in the oil-in-water (O/W) emulsion. This gave a high extraction efficiency for MEP. UAME is a simple method requiring only a change in the ultrasound frequency and with no pretreatment steps that could contaminate the sample. The suitability of UAME was demonstrated by application to the detection of trace levels of pesticides in a spiked water sample from a fish tank. Graphical abstract Schematic diagram of the ultrasound-assisted microextraction (UAME) method.

Electrochemiluminescence of Tris(2,2'-bipyridyl)ruthenium(II) with Ascorbic Acid and Dehydroascorbic Acid in Aqueous and Non-aqueous Solutions.

The electrochemiluminescence (ECL) of tris(2,2'-bipyridyl)ruthenium(II) (Ru(bpy)3(2+)) is studied in non-aqueous media using dehydroascorbic acid (DHA) as coreactant to validate the evidence for the mechanism of the ascorbic acid (H2A)/Ru(bpy)3(2+) ECL system in an aqueous media. DHA is electrochemically reduced around -1.2 V vs. Ag/Ag(+) in pure acetonitrile to generate the ascorbyl radical anion (A(•-)), which is confirmed by in-situ UV-visible absorption measurements using a thin-layer spectroelectrochemical cell. The ECL of the DHA/Ru(bpy)3(2+) system in non-aqueous media is not observed in the potential range from 0 to +1.4 V in anodic potential sweep mode; however, distinct ECL is detected using double potential step electrolysis from -1.2 to +1.4 V vs. Ag/Ag(+). The ECL may be generated by a homogeneous charge-transfer process between A(•-) produced during the first pulse potential step (-1.2 V) and Ru(bpy)3(3+) generated during the second pulse potential step (+1.4 V). The calculated standard enthalpy (-ΔH°) for the charge-transfer reaction between A(•-) and Ru(bpy)3(3+) is 2.29 eV, which is larger than the lowest excited singlet state energy of Ru(bpy)3(2+) (*Ru(bpy)3(2+); 2.03 eV, 610 nm). It is determined that the generated intermediate A(•-) is crucial in the Ru(bpy)3(2+) ECL reaction.

Coordinated regulation of vegetative and reproductive branching in rice.

Grasses produce tiller and panicle branching at vegetative and reproductive stages; the branching patterns largely define the diversity of grasses and constitute a major determinant for grain yield of many cereals. Here we show that a spatiotemporally coordinated gene network consisting of the MicroRNA 156 (miR156/)miR529/SQUAMOSA PROMOTER BINDING PROTEIN LIKE (SPL) and miR172/APETALA2 (AP2) pathways regulates tiller and panicle branching in rice. SPL genes negatively control tillering, but positively regulate inflorescence meristem and spikelet transition. Underproduction or overproduction of SPLs reduces panicle branching, but by distinct mechanisms: miR156 and miR529 fine-tune the SPL levels for optimal panicle size. miR172 regulates spikelet transition by targeting AP2-like genes, which does not affect tillering, and the AP2-like proteins play the roles by interacting with TOPLESS-related proteins (TPRs). SPLs modulate panicle branching by directly regulating the miR172/AP2 and PANICLE PHYTOMER2 (PAP2)/Rice TFL1/CEN homolog 1 (RCN1) pathways and also by integrating other regulators, most of which are not involved in tillering regulation. These findings may also have significant implications for understanding branching regulation of other grasses and for application in rice genetic improvement.

Application of Electrochemiluminescence for the Evaluation of the Antioxidant Capacity of Some Phenolic Compounds Against Superoxide Anion Radicals.

This paper for the first time reports on novel and non-enzymatic method for studying the free radical-scavenging properties of phenolic compounds against superoxide anion radicals (O2·(-)) by using the cathodic electrochemiluminescence (ECL) of lucigenin (Luc(2+)). The ECL of Luc(2+) at a glassy carbon (GC) electrode is observed in an aeration electrolytic solution (pH 7), which is believed to be due to the reaction of a one-electron reduced form of Luc(2+) (i.e. a radical cation, Luc·(+)) with in situ electrogenerated O2·(-). The ECL intensity is dependent on the concentration of dissolved oxygen, and is suppressed dramatically by superoxide dismutase (SOD), a typical O2·(-) scavenger. Since the coexisting hydrogen peroxide (H2O2) has no influence on the cathodic ECL of Luc(2+), it is thus suggested that the ECL signal specifically reflected the O2·(-) concentration level generated at the electrode surface. When phenolic compounds were added into the solution, this resulted in the inhibition of ECL signals due to the elimination of O2·(-). The ECL inhibition rate measured at each concentration was compared against the SOD equivalent (U mL(-1)), and the relative antioxidant efficiency, Kao (U mmol(-1) equivalent SOD), was used to evaluate the antioxidant activity of some phenolic compounds, including flavonoids, in this study. Structurally different water-soluble phenols were compared, and those compounds containing to catechol skeletal structure are found to present the higher antioxidant capacity.

Synthesis, Absorption, and Electrochemical Properties of Quinoid-Type Bisboron Complexes with Highly Symmetrical Structures.

Novel bisboron complexes of bidentate ligands consisting of 1,4-benzoquinone and two pyrrole rings were synthesized by using a simple two-step reaction. In solution, the bisboron complexes showed absorption maxima at ∼620 and 800 nm, which were attributed to the allowed S0 → S2 and forbidden S0 → S1 transitions, respectively. The bisboron complexes did not show any fluorescence, probably because of their highly symmetrical structure which forbids the S0 → S1 transition. Bisboron complexes underwent a two-electron reduction to yield the corresponding aromatic dianion, which showed absorption maxima at ∼410 nm.

East China Sea Storm Surge Modeling and Visualization System: the Typhoon Soulik case.

East China Sea (ECS) Storm Surge Modeling System (ESSMS) is developed based on Regional Ocean Modeling System (ROMS). Case simulation is performed on the Typhoon Soulik, which landed on the coastal region of Fujian Province, China, at 6 pm of July 13, 2013. Modeling results show that the maximum tide level happened at 6 pm, which was also the landing time of Soulik. This accordance may lead to significant storm surge and water level rise in the coastal region. The water level variation induced by high winds of Soulik ranges from -0.1 to 0.15 m. Water level generally increases near the landing place, in particular on the left hand side of the typhoon track. It is calculated that 0.15 m water level rise in this region can cause a submerge increase of ~0.2 km(2), which could be catastrophic to the coastal environment and the living. Additionally, a Globe Visualization System (GVS) is realized on the basis of World Wind to better provide users with the typhoon/storm surge information. The main functions of GVS include data indexing, browsing, analyzing, and visualization. GVS is capable of facilitating the precaution and mitigation of typhoon/storm surge in ESC in combination with ESSMS.

Enzymatic flow injection method for rapid determination of choline in urine with electrochemiluminescence detection.

In order to determine trace choline in human urine, a flow injection analysis (FIA) system has been developed by coupling an enzyme reactor with an electrochemiluminescence (ECL) detector. The enzyme reactor is prepared by covalently immobilizing choline oxidase (ChOx) onto the aminopropyl-controlled pore glass beads, which are then carefully packed into a micro column. The enzyme reactor catalyzes the production of hydrogen peroxide that is in direct proportion to the concentration of choline. In this study, the enzymatically produced hydrogen peroxide was detected by an ECL detector positioned at the down stream of an enzyme reactor based on the luminol/H(2)O(2) ECL system. Under the optimized condition, the enzymatic FIA/ECL provided high sensitivity for the determination of choline with the detection limit as low as 0.05 microM (absolute detection limit was at sub pmol level). The method was successfully applied in the determination of choline in the samples of human urine, and the analytical results were in good agreement with those obtained by using the microbore HPLC with an immobilized enzyme reactor-electrochemical detection system.