Flow injection assays with chemiluminescence and bioluminescence detection — A review

This paper reviews publicaions that combine the technique of flow injection (FI) with chemiluminescence (CL) and bioluminescence (BL) detection, from the earliest papers in 1979/80 to mid-1992, and refers exclusively to reactions occurring in solution. Airsegmented systems and liquid chromatography with CL detection are not considered unless FI has been used to pre-optimize the system. The applications have been categorized in terms of the type of CL reaction; there are separate entries for luminol, peroxyoxalate, other CL reactions and BL reactions. Each of the four sections includes a table of applications that lists the analyte, the nature of the reaction, the sample matrix and the limit of detection.     

Determination of aromatic compounds by high-performance liquid chromatography with on-line photoreactor and peroxyoxalate chemiluminescence detection.

This paper describes a novel high-performance liquid chromatographic (HPLC) method for the determination of aromatic compounds with peroxyoxalate chemiluminescence (PO-CL ) detection following on-line UV irradiation. Aromatic compounds were UV irradiated (254 nm, 15 W) to generate hydrogen peroxide, which was determined via PO-CL detection using a mixture of bis(2,4,6-trichlorophenyl)oxalate (aryloxalate) and 2,4,6,8-tetrathiomorpholinopyrimido[5,4-d]pyrimidine (fluorophore) as a post-column CL reagent. Generation of hydrogen peroxide from aromatic compounds was confirmed using a flow injection analysis (FIA) system incorporating an enzyme column reactor immobilized with catalase. The conditions for UV irradiation were optimized using benzene and monosubstituted benzenes (phenol, benzaldehyde, nitrobenzene and N,N-dimethylaniline) by an HPLC system to evaluate the analytical performance of the proposed system. The detection limits for benzene and monosubstituted benzenes were in the range 2.1-124 pmol/injection at signal:noise (S:N) ratio = 3. Monocyclic and polycyclic hydrocarbons were also employed to investigate their CL properties. The possibility of PO-CL detection for a wide variety of aromatic compounds was shown for the first time.     

Flow‐based analysis using microfluidics–chemiluminescence systems

This review will discuss various approaches and techniques in which analysis using microfluidics–chemiluminescence systems (MF–CL) has been reported. A variety of applications is examined, including environmental, pharmaceutical, biological, food and herbal analysis. Reported uses of CL reagents, sample introduction techniques, sample pretreatment methods, CL signal enhancement and detection systems are discussed. A hydrodynamic pumping system is predominately used for these applications. However, several reports are available in which electro‐osmotic (EO) pumping has been implemented. Various sample pretreatment methods have been used, including liquid–liquid extraction, solid‐phase extraction and molecularly imprinted polymers. A wide range of innovative techniques has been reported for CL signal enhancement. Most of these techniques are based on enhancement of the mixing process in the microfluidics channels, which leads to enhancement of the CL signal. However, other techniques are also reported, such as mirror reaction, liquid core waveguide, on‐line pre‐derivatization and the use of an opaque white chip with a thin transparent seal. Photodetectors are the most commonly used detectors; however, other detection systems have also been used, including integrated electrochemiluminescence (ECL) and organic photodiodes (OPDs). Copyright © 2012 John Wiley & Sons, Ltd.     

High-performance liquid chromatography of phosphatidic acid

This paper reviews existing high-performance liquid chromatographic (HPLC) methods for the analysis of phosphatidic acid (PA) in various sample matrices. In addition to the introductory background discussion on important aspects of PA in lipid biochemistry, the review provides comprehensive coverage in the areas of derivatization techniques, detection methods, and HPLC separation techniques. Conversions of PA to suitable derivatives enhance the detection sensitivity and improve the chromatographic behavior of the analytes. Detection methods include the use of state-of-the-art detectors and are discussed in terms of sensitivity, specificity, and compatibility with analytical systems. Pertinent normal-phase and reversed-phase HPLC data for PA are compiled from published methods.     

Quantum dots‐based chemiluminescence probes: an overview

This mini‐review describes the recent developments in quantum dots‐based nanoprobes in liquid‐phase chemiluminescence (CL) analysis. In the referenced reports, multiple quantum dots (QDs) were adopted as final emission species either after direct oxidation reactions (direct CL) or after chemiluminescence resonance energy transfer (indirect CL). This review does not include papers in which QDs have been used as enhancers, catalysts, carriers or quenchers in chemiluminescence systems. A brief overview on the CL mechanisms of various QDs‐based nanoprobes and their analytical applications over the last decade is given, followed by comments on the future challenges and prospects in this field.     

Potential of the luminol reaction in the sensitive detection of pesticide residues by flow injection analysis.

This study presents the first analytical application of the luminol chemiluminescence (CL) reaction for the sensitive detection of carbamate residues. Some experiments have been carried out to check the influence of the presence of traces of a N-methylcarbamate (carbaryl) on the CL emission produced from the oxidation of luminol using different oxidants, showing a significant enhancing effect on the CL emission when the oxidation of luminol is produced by potassium permanganate in alkaline medium, this enhancement being proportional to the carbaryl concentration. This fact has permitted the establishment of a sensitive chemiluminescence flow-injection (CL-FIA) method for the direct determination of carbaryl. The optimization of instrumental and chemical variables influencing the CL response has been carried out by applying experimental designs. Under the optimal conditions, the CL intensity was linear for a carbaryl concentration over the range 5-100 ng/mL with a detection limit of 4.9 ng/mL. This luminol-KMnO4-based FIA-CL system in basic medium shows an easy, fast and cheap alternative detection mode for the analysis of carbaryl residues in environmental water samples.     

Prospects for chemiluminescent and bioluminescent immunoassay and nucleic acid assays in food testing and the pharmaceutical industry

The sensitivity, speed and convenience of chemiluminescent (CL) and bioluminescent (BL) immunoassays and probe assays have led to a diverse range of applications for these technologies, mainly in the clinical laboratory. These methods are now being explored by the food and pharmaceutical industries. Demanding detection limits and the complexity of sample preparation for food and pharmaceutical analyses present daunting challenges for the analyst. Immunoassay and nucleic acid amplification technologies have been applied to food testing, but these have mostly favoured non-luminescent endpoints. Food assays with CL or BL endpoints are now emerging, e.g., Clostridium botulinum type A detection using a CL immunosorbent assay; Salmonella and Zygosaccharomyces detection using a combination of PCR and CL detection. The analytical challenges posed by the pharmaceutical industry include testing for contaminants in raw materials and drug products, and drug discovery. The sensitivity and rapid signal acquisition characteristics of CL and BL are advantageous for the high throughput, massively parallel testing of micro-sized samples demanded in drug discovery. Current progress and the prospects for CL and BL immunoassay and nucleic acid technologies in this and other pharmaceutical and food applications is reviewed. © 1998 John Wiley & Sons, Ltd.     

Reverse micelle-based chemiluminescence system for quinine sulphate.

A new chemiluminescence (CL) method is proposed for the determination of quinine sulphate, which is based on the dichloromethane solvent extraction of the ion-pair complex of tetrachloroaurate (III) with quinine sulphate, and luminol CL detection in a reversed micellar medium formed by the cation surfactant cetyltrimethylammonium bromide in a dichloromethane-cyclohexane (3:7, v/v)-water (0.35 mol/L Na2CO3 buffer solution, pH 11.5). The ion-pair complex of tetrachloroaurate (III) with quinine sulphate produced an analytical CL signal when it entered the reversed micellar water pool. In optimum conditions, CL intensities are proportional to the concentrations of the studied drug over the range 0.015-10 microg/mL, with a detection limit of 1.5 ng/mL. The relative standard deviation (RSD) is 1.38% for 2.5 microg/mL quinine sulphate (n=11). The method has been applied to the determination of the studied drug in biological fluids, with satisfactory results.     

Light from maillard reaction: Photon counting,emission spectrum,photography and visual perception

Several authors have reported on high-sensitivity measurement of oxygen-dependent low-level chemiluminescence (CL) from Maillard reactions (MR), i.e. nonenzymatic amino-carbonyl reactions between reducing sugars and amino acids (also referred to as nonenzymatic browning). Here we report for the first time, that light from Maillard reactions can be seen by the human eye and also can be photographed. In parallel with visual perception and photography CL was monitored by means of a CL-detection programme of a liquid scintillation counter (LSC, single photon rate counting). CL emission spectrum was recorded by a monochromator-microchannel plate photomultiplier arrangement. CL intensity from reaction of 6-aminocaproic acid with D-ribose (200 mg each) in 5 mL H₂O at pH 11 at 95°C was high enough for visual perception after adaptation to absolute darkness. Reaction in dimethylsulphoxide (DMSO) exhibited strongly enhanced CL (10 mg each in 5 mL were sufficient for visual detection) and could be photographed (15 minutes' exposure, ASA 6400); all characteristics of Maillard specific CL (O₂-dependence, no CL from nonreducing sugars, inhibition by sulphur compounds) remained. Visual detection of CL and measurement by LSC were in full concordance. The CL emission spectrum showed two broad peaks at around 500 nm and 695 nm. Fluorescence emission of the brown reaction mixture matched the bluegreen part of the CL emission spectrum. Emission of visible light during Maillard reactions may partly originate from oxygen-dependent generation of excited states and energy transfer to simultaneously formed fluorescent products of the browning reaction.     

Flow injection chemiluminescence determination of dihydralazine sulphate based on permanganate oxidation sensitized by rhodamine B.

A novel flow injection chemiluminescence (CL) method for the determination of dihydralazine sulphate (DHZS) is described. The method is based on the CL produced during the oxidation of DHZS by acidic permanganate solution in the presence of rhodamine B. Rhodamine B is suggested as a fluorescing compound for the energy-transferred excitation. The CL emission allows quantitation of DHZS concentration in the range 5-800 ng/mL, with a detection limit of 1.9 ng/mL (3sigma). The experimental conditions for the CL reaction are optimized and the possible reaction mechanism is discussed. The method has been applied to the determination of DHZS in pharmaceutical preparations and compares well with the high performance liquid chromatography (HPLC) method.     

A simple and fast detection technique for arsenic speciation based on high‐efficiency photooxidation and gas‐phase chemiluminescence detection

High‐efficiency photooxidation (HEPO) and gas phase chemiluminescence detection (CL) combined with high‐performance liquid chromatography (HPLC) and hydride generation were developed for speciation of As(III), As(V), monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA). After chromatography separation, the arsenic species were passed through HEPO which performed efficient photooxidation and converted MMA and DMA to As(V) in several seconds. Then the reaction of ozone and arsine upon hydride generation produced a CL signal as the analytical parameter. The total analytical process was completed within 10 min. The effects of operational parameters such as the concentrations of hydrochloric acid and NaBH₄ solution, carrier gas flow and air gas flow for ozone generation were investigated. Detection limits were 3.7, 10.3, 10.2 and 10.0 µg/L for As(III), As(V), MMA and DMA, respectively. The recoveries of the four arsenic species in human urine sample ranged from 87 to 94%. Copyright © 2009 John Wiley & Sons, Ltd.     

Determination of propylthiouracil and methylthiouracil in human serum using high-performance liquid chromatography with chemiluminescence detection

Based on the sensitizing effect of formaldehyde on the chemiluminescence (CL) reaction of propylthiouracil (PTU) and methylthiouracil (MTU) with acidic potassium permanganate and the combination technique of high-performance liquid chromatography (HPLC), a sensitive, selective and simple post-column CL detection method for determining PTU and MTU is described. The optimal conditions for the CL detection and HPLC separation were carried out. The linear ranges were 0.1-20 microg mL(-1) for MTU and 0.1-10 microg mL(-1) for PTU, the detection limits were 0.03 microg mL(-1) for PTU, 0.03 microg mL(-1) for MTU and the quantification limits were 0.1 microg mL(-1) for PTU, 0.1 microg mL(-1) for MTU. The method has been satisfactorily applied for the determination of MTU and PTU in human serum samples.     

Direct chemiluminescent imaging detection of human serum proteins in two-dimensional polyacrylamide gel electrophoresis

A novel chemiluminescence (CL)-based imaging method capable of directly detecting proteins in polyacrylamide gels after electrophoresis is proposed. Human serum proteins are presently detected by a direct CL imaging method after native 2-D PAGE. As a consequence, some proteins, including haptoglobin (Hp), Hp precursor, hemopexin (Hpx) precursor, Ig alpha-1 chain C region, and Complement C3 precursor can be detected and identified by MS and MS/MS techniques. These proteins are all acute phase proteins, which have been defined as biomarkers for certain diseases. Moreover, serum proteins from healthy people and cirrhotic patients were analyzed. A decrease in Hp spots for cirrhotic patients could be confirmed. The CL imaging conditions were optimized, including the concentrations of H(2)O(2) and luminol. The process of CL detection of proteins is simple, and there is no need for specialized equipment. In comparison with the traditional CBB-R250 staining method, the detection sensitivity was improved and the detection period decreased about 70 times. Hence, this technique possesses potentials as a rapid, convenient, and inexpensive analytical technique for protein detection and for the diagnosis of diseases.     

Separation methods for camptothecin and related compounds

This paper reviews working procedures for the analytical determination of camptothecin and analogues. We give an overview of aspects such as the chemistry, structure–activity relationships, stability and mechanism of action of these antitumor compounds. The main body of the review describes separation techniques. Sample treatment and factors influencing high-performance liquid chromatography development are delineated. Published high-performance liquid chromatographic methods are summarized to demonstrate the variability and versatility of separation techniques and a critical evaluation of separation efficiency, detection sensitivity and specificity of these methods is reported.     

Detection of synthetic corticosteroids in bovine urine by chemiluminescence high-performance liquid chromatography.

The development of a black market of chemical cocktails for illegal growth promotion in food-producing animals includes substances that are potentially dangerous for human health, such as synthetic corticosteroids. The potential presence of these residues in food makes it necessary to develop rapid and sensitive analytical methodologies to detect such substances, preferably in live animals before they arrive at the market. A chemiluminescence (CL) detection method for the determination of four synthetic corticosteroids (prednisolone, betamethasone, dexamethasone and flumethasone) in bovine urine has been developed. The proposed system, which does not need any derivatization procedure, offers an easy method well suited for routine research. Urine samples were homogenized with methanol:water (50:50, v/v) and centrifuged. The upper layer was collected and Strata X cartridges were used for cleaning up. The purified residues were evaporated to dryness and then redissolved in the mobile phase. Analysis of the extracts was performed using high-performance liquid chromatography with chemiluminescence detection, employing luminol as the CL reagent. The recovery curves, obtained at four spiking levels (different for each corticosteroid), showed that recoveries of at least 70% could be obtained for urine. The chemiluminescence detection procedure afforded satisfactory results with respect to sensitivity and the LOD and LOQ, taken as the first point of the regression curve, ranged from 4 ppb to 65 ppb. The maximum mean RSD was below 13% and below 15% for intra- and inter-day assay, respectively, in all cases.     

Ultrasensitive assay of clindamycin in medicine and bio-fluids with chemiluminescence detection.

A simple chemiluminescence (CL) method using flow injection has been developed for the determination of clindamycin, based on the inhibitory effect of clindamycin on the CL generated from the luminol-K(3)Fe(CN)(6) system in alkaline medium. It was found that the decrement of CL intensity was linear with the logarithm of clindamycin concentration over the range 0.7-1000 ng/mL. The detection limit was 0.2 ng/mL with a relative standard deviation (RSD) of <5.0% (n = 7). At a flow rate of 3.0 mL/min, a complete analytical process could be performed within 0.5 min, including sampling and washing. The proposed procedure was applied successfully to the determination of clindamycin in pharmaceutical preparations and human urine without pretreatment.     

Cathodoluminescence-emitting lipid droplets in rat testis: a study by analytical color fluorescence electron microscopy

Cathodoluminescence (CL) from lipid droplets (LDs) in the rat testis was examined by analytical color fluorescence electron microscopy. The results show that (1) the Cl at wavelengths of 320 nm (CL320) and 450 nm (CL450) is derived from cholesterol esters and a mixture of lipids including vitamin A esters, respectively; (2) CL320 in the LDs of Leydig cells sharply decreases on postnatal day 21, while CL320 and CL450 in the LDs of Sertoli cells begin to be detectable; (3) the CL450-emitting LDs in seminiferous tubules, whose distributional patterns display cyclic changes during the spermatogenic cycle, are involved in spermatogenesis; and (4) the intensity of CL as well as the distributional patterns of CL-emitting LDs in testicular cells change after hypophysectomy, vitamin-A deficiency, and treatment with ethylene dimethane sulfonate and testosterone propionate. This study demonstrates that analytical color fluorescence electron microscopy is a useful tool for in-vivo observation of some specific compounds which cannot be visualized by other methods.     

Trap capture of three economically important fruit fly species (Diptera: Tephritidae): evaluation of a solid formulation containing multiple male lures in a Hawaiian coffee field

Invasive fruit flies (Diptera: Tephritidae) pose a global threat to agriculture through direct damage to food crops and the accompanying trade restrictions that often result. Early detection is vital to controlling fruit flies, because it increases the probability of limiting the growth and spread of the invasive population and thus may greatly reduce the monetary costs required for eradication or suppression. Male-specific lures are an important component of fruit fly detection, and three such lures are used widely: trimedlure (TML), cue lure (CL), and methyl eugenol (ME), attractive to Mediterranean fruit fly, Ceratitis capitata (Wiedemann); melon fly, Bactrocera cucurbitae (Coquillett); and oriental fruit fly, Bactrocera dorsalis (Hendel), respectively. In California, Florida, and Texas, the two Bactrocera lures are applied to separate species-specific traps as liquids (with a small amount of the insecticide naled added), whereas TML is delivered as a solid plug in another set of traps. Thus, the detection protocol involves considerable handling time as well as potential contact with a pesticide. The purpose of this study was to compare trap capture between liquid male lures and "trilure" wafers that contain TML, ME, raspberry ketone (RK, the hydroxy equivalent of CL), and the toxicant DDVP embedded within a solid matrix. Field studies were conducted in a Hawaiian coffee (Coffea arabica L.) field where the three aforementioned species co-occur, showed that the wafer captured at least as many flies as the liquid baits for all three species. This same result was obtained in comparisons using both fresh and aged (6-wk) baits. Moreover, the wafers performed as well as the single-lure traps in an ancillary experiment in which TML plugs were substituted for liquid TML. Additional experiments demonstrated explicitly that the presence of ME and RK had no effect on captures of C. capitata males and similarly that the presence of TML had no effect on the capture of B. cucurbitae or B. dorsalis males.     

Determination of alkaloids in Sinomenium acutum by field‐amplified sample stacking in capillary electrophoresis with chemiluminescene detection

A simple and rapid capillary electrophoresis (CE) with an acidic potassium permanganate chemiluminescence (CL) detection method was developed to determine three alkaloids (curine, sinomenine and magnoflorine) simultaneously. A laboratory‐built CE–CL detection interface was used. The field‐amplified sample stacking technique was applied to the online concentration of alkaloids. Experimental conditions for CE separation and CL detection were investigated in detail to acquire optimum conditions. Under optimal conditions, the three alkaloids were baseline separated within 6 min, and the detection limits (S/N = 3) ranged from 0.03 µg/mL to 0.49 µg/mL. This method was successfully applied to determine the above three alkaloids in Sinomenium acutum, and the result of the determination of sinomenine was in good agreement with those given by high‐performance liquid chromatography and CE methods. In addition, a possible CL reaction mechanism of sinomenine–KMnO₄–H₂SO₄ was proposed. Copyright © 2013 John Wiley & Sons, Ltd.