| The chemiluminescence (CL) has attracted a great deal of attention as an interesting anduseful detection method in analytical chemistry because of its advantages. It has beendeveloped to be an important and powerful tool in different fields such as environmentalmonitoring, drug analysis, food analysis, biomedical detection, and clinical diagnose. MostCL reactions have low quantum efficiencies and thus show weak luminescence. The weakemission can be greatly enhanced by sensitizers, which is used to establish sensitized CLsystem. The sensitized CL system for detection has the advantages of longer emission time,stronger CL intensity, higher sensitivity and veracity, wider linear range and easiermeasurement. In the paper, some recent developments and applications of sensitized CLsystems, including the uses of metal ions, fluorescent substances, surfactants, enzymes andnanoparticles are reviewed. The CL properties of CdTe quantum dots (QDs),diperiodatocuprate (III)(DPC),2-substituted-4,5-di(2-furyl)-1H-imidazoles and lanthanideions were investigated, and some of sensitized CL systems were developed. The effects ofreaction medium, reactant concentrations and coexisting substances on the CL emission wereinvestigated. The possible enhancement mechanisms of the CL systems were investigated.The methods were successfully applied to determine the content of the practical samples.In this paper,3-mercaptocarboxylic acid (MPA) modified CdTe QDs were used assensitizers and emissive species for CL analysis. The addition of CdTe into thecalcein-K3Fe(CN)6system and Tween20into the CdTe-H2O2system could inducesignificant enhancement of CL signals. The new sensitized CL systems ofCdTe-calcein-K3Fe(CN)6and Tween20-CdTe-H2O2were developed. The effects of theparticle sizes of CdTe QDs and reactant concentrations on the CL emission were investigated in detail. The possible enhancement mechanisms of the CL systems were further investigatedbased on the photoluminescence (PL) and CL spectra. The influences of polyphenols, such ascatechol, hydroquinone, hyperin, chlorogenic acid and kaempferol, on the CL signals of theCdTe-calcein-K3Fe(CN)6and Tween20-CdTe-H2O2systems were examined. It was foundthat the addition of the polyphenols into the systems could induce inhibition of CL signals.There is a good linear relationship between the quenched intensity for the CL and theconcentration or the logarithm of concentration of polyphenols. The proposed methods wereapplied to the determination of hyperin in seed of Cuscuta chinensis Lam. and catechol in tapwater sample, respectively. The results obtained were satisfactory. The proposed systemshave advantages of high sensitivity and wide linear response range for the determination ofpolyphenols.The DPC solution was prepared according to the reported method. In the paper, asensitized CL system was developed based on the catalytical effect of DPC on the1,10-phenanthroline (phen)-H2O2in the presence of cetyltrimethylammonium bromide(CTAB). The effects of experimental parameters, including reaction medium andconcentrations of DPC, H2O2, CTAB and phen, on the CL intensity of the system wereinvestigated. Meanwhile the increase of CL intensity of the DPC-phen-H2O2-CTAB system isproportional to the concentration of phen in the range of low concentration. The linear rangeof the calibration curve is5.0×10-9-1.0×10-6mol/L, and the corresponding detection limit is1.9×10-9mol/L. The CL mechanism was also discussed briefly based on the PL and CLspectra. Under the optimal conditions, the effects of polyphenols on theDPC-phen-H2O2-CTAB CL system were investigated. It was observed that polyphenolsinhibit the CL signal of the system. Hydroquinone was used as an example to investigate theapplication of the CL system for the determination of polyphenols. The quenched CLintensity is linearly related to the logarithm of concentration of hydroquinone. The linearrange of the calibration curve is2.5×10-9-1.0×10-5g/mL, and the corresponding detectionlimit is1.8×10-9g/mL. The method was applied to the determination of hydroquinone inwater samples, such as tap water, rain water and lake water samples. The spiked samples wereanalyzed and the recoveries of hydroquinone at the different concentration levels ranged from 92%to106%.In the paper, two2-substituted-4,5-di(2-furyl)-1H-imidazoles,2,4,5-tri(2-furyl)-1H-imidazole (TFI) and2-phenyl-4,5-di(2-furyl)-1H-imidazole (PDFI), were synthesizedaccording to the reported methods. The directly oxidized CL of TFI and PDFI by basic H2O2and acidic KMnO4were studied in detail. The H2O2and KMnO4could directly oxidize TFIand PDFI to produce strong CL emission, and the CL emission induced by TFI was sronger.The addition of Cu2+into the TFI/PDFI-H2O2system and albumin into the TFI/PDFI-KMnO4system could induce significant enhancement of CL signals, and the enhanced CL intensity islinearly related to the concentration of Cu2+and the logarithm of concentration of albumin,respectively. Two new sensitized CL systems were developed. The proposed methods havebeen used to determine trace amount of Cu2+and albumin with limits of detection (3σ) of6.5×1011mol/L,3.5×10-10mol/L, respectively. The interference of some metal ions, glucoseand amino acids was tested, and the results indicated the proposed methods are quite selectivefor determination of Cu2+and albumin. The proposed methods were applied to thedetermination of Cu2+in the reference material samples (such as silicate rock, soil and streamsediments) and human serum albumin (HSA) in human serum samples, respectively. Theresults obtained were satisfactory.The reactions of lanthanide ions Tb3+, Eu3+, Ce3+ and La3+ with some common oxidants,including K2S2O8, H2O2,(NH4)2S2O8, Ce(SO4)2, K3Fe(CN)6, KMnO4, were investigated. Theexperimental results indicate that only K2S2O8and (NH4)2S2O8can react with lanthanide ionsin alkaline medium, which produces CL signals. The rank order of CL intensity was Tb3+>La3+> Eu3+> Ce3+ in the presence of the same oxidant. However, compared with CL inducedby K2S2O8, that induced by (NH4)2S2O8was weaker. Therefore, K2S2O8was selected asoxidant for the CL reaction. A new CL system of Tb3+-K2S2O8was developed for thedetermination of albumin, such as bovine serum albumin (BSA), HSA and ovalbumin (OVA).Some experimental conditions were examined and optimized. The linear ranges of thecalibration curves are5.0×10-9-5.0×10-6mol/L for BSA,5.0×10-8-1.0×10-5mol/L for HSAand2.5×10-7-1.0×10-5mol/L for OVA, and the corresponding detection limits are1.9×10-9mol/L,1.5×10-8 mol/L and1.5×10-7mol/L, respectively. The method was applied to the determination of HSA in human serum samples, and the results were in agreement with thoseobtained by the bromcresol green method. The relative errors for the analytical results werefrom-2.0%to4.3%.
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