[Study on the mechanism of sodium formate enhancing luminol chemiluminescence and its application in micellar medium].

In the presence of sodium dodecylbenzene sulfonate (SDBS) surfactant micelles, the signal of K2 Cr2 O7-luminol-adenine chemiluminescence system was strongly enhanced by sodium formate, which is conventionally considered as free radical scavenger. The present article discussed the sensitizing mechanism of chemiluminescence through the methods of chemiluminescence emission spectra, UV-visible absorption spectra, and chemical reactions. The result indicated that free radical OH*, which existed in the original chemiluminescence system, was transformed into free radical O2* by the existence of sodium formate. Based on that, a highly sensitive flow injection-chemiluminescence method to determine adenine was established. Under optimal experimental conditions, the concentration of adenine was linear with the chemiluminescence intensity in the range of 8.18 x 10(-9) to 2.45 x 10(-11) mol x L(-1). The limit of detection (3sigma) was 8.72 x 10(-12) mol x L(-1). The method has been successfully applied to the analysis of adenine in VB4 pills and the results are satisfactory.

[Chemiluminescence determination of 6-mercaptopurine in the luminol-potassium ferricyanide system].

A novel chemiluminescence (CL) method to determine 6-mercaptopurine (6-MP) is described, based on the catalytic effect of 6-MP on the CL reaction of luminol with K3Fe(C-N)6 in a flow system. Under optimal experimental conditions, the calibration graph is linear in the range of 1.02 x 10(-7) to 1.02 x 10(-9) mol x L(-1) 6-MP. The linear regression equation was Y = 36.315c + 140.72, where Y is the relative emission intensity and c is the concentration of 6-MP expressed in 10(-8) mol x L(-1) and the correlation coefficient is 0. 998 2 with the detection limits of 6. 33 X 10(-10) mol x L(-1) (S/N = 3). CL peak-height precision is 3.54% of RSD (n = 12) for a level of 2.0 x 10(-9) mol x L(-1). This method satisfactorily provides a fast, simple, sensible and favorable technique for the determination of 6-MP in synthesized samples in implementation. Moreover, the possible mechanism of CL enhancement was briefly discussed. Obviously, the reaction was related to the formation of free radicals. Thus, the CL emission could preliminarily be attributed to the process of energy transfer due to O2. radical and * OH radical resulting from the oxidation product of 6-MP by K3Fe(CN)6, which acts as an active intermediate that reacts with luminol, leading to the formation of excited luminol molecule, which gives out an emission when it returns to its ground state.

[Concentrations and distribution of heavy metals in urban sewage discharge channel of Tianjin].

Concentrations of metals, organic matter(OM), total nitrogen (TN) and total phosphorus (TP) were determined in sediment and soil samples collected from 15 selected sites along Dagu sewage discharge channel in Tianjin, China. Relative enrichment factors and correlation analysis were taken to study the distribution and pollution level of metals. The results show that pollution level is more serious in sediment than that in soil. Hg, Cd, Zn and Pb are more enriched while Cr, Ni and As are less enriched. Relative enrichment factors (REF) of Hg, Cd, Zn and Pb in sediment are 59.3, 25.4, 14.5 and 7.5, and that in soil are 8.44, 5.19, 6.6 and 3.3, respectively. The heavy metal concentrations greatly vary among different sampling sites, which is demonstrated by the fact that coefficient of variation (CV) varies from 74.4% to 110.8% in sediment. The highest enrichments of heavy metals are found in sampling site S4 and S12, which are affected by chemical industry wastewater. There is no significant correlation between metal concentrations in sediment and those in soil. The concentrations of heavy metals in sediment are not reciprocally correlated, either. However, significant correlations exist among many pollutants in soil. Hg, Cd, Zn and Pb are positively correlated with each other, at the same time they are positively correlated with OM, TN and TP, but Cr, Ni and As are poorly correlated with OM and TP, which suggests that Cd, Zn and Pb have similar environmental geochemical properties and are contaminated by anthropogenic impact. When compared with the main rivers in Tianjin, the enrichment of heavy metals in Dagu sewage discharge channel is relatively high.

[Study on photo-degradation kinetics of hemin in the presence of anion surfactant].

A novel photodecomposition behavior of hemin was described. With RhB-H2O2 system a flow injection chemiluminescence method has been applied to the study of the photolytic kinetics of hemin under ultraviolet light. And the sodium dodecyl sulfonate (SDS) was added as a photostability-stabilizer. The results showed that the decomposition reaction of hemin in the presence and absence of SDS corresponded to a first-order reaction. Furthermore, the presence of SDS in the system decreased the photolytic rate of hemin by 1.8 times compared to that in the absence of SDS.

[Recent progress in flow-injection chemiluminescence for pharmaceutical analysis].

Flow-injection chemiluminescence(FI-CL) analysis has made great progress in analytical chemistry for its high sensitivity with a wide linear range, simple instruments, rapidity and reproducibility in signal detection, and being appropriate for on-line analysis. A review with 74 references dating from 2002-early 2004 is given of the application of FI-CL method in the determination of drugs.

[Determination of uric acid by chemiluminescence].

A novel chemiluminescence method for the determination of uric acid based on its inhibitory effect on the catalysis of Co2+ for the oxidation of luminol by H2O2 is described. The proposed method is simple, very sensitive and inexpensive. The decrease of cheniluminescence intensity is linearly correlated with uric acid concentration. The calibration graph is linear over the range of 1.0 x 10(-10) - 7.0 x 10(-6) mol x L(-1) and the detection limit is 1.1 x 10(-11) mol x L(-1). The relative standard deviation (RSD) for 5.0 x 10(-8) is 1.9% (n=4). The method has been successfully applied to the determination of uric acid in human urine and serum samples.

[Determination of 2,3,5,4'-tetrahydroxystilbene-2-O-beta-D-glucoside in the traditional Chinese preparation by high performance liquid chromatography with chemiluminescence detection].

Based on the chemiluminescence reaction of KMnO4-HNO3-2,3,5,4'-tetrahydroxystilbene-2-O-beta-D-glucoside sensitized by HCHO, an analytical method for 2,3,5,4'-tetrahydroxystilbene-2-O-beta-D-glucoside by RP-HPLC with chemiluminescence detector was developed. The chromatographic conditions were optimized. AN ODS hypersil column(25 mm x 4.0 mm, 125 x 4.0 mm i.d. 5 microm) was used with acetonitrile--0.3% H3PO4 [25:75, (phi)] as mobile phase, and the flow rate was 0.8 mL x min(-1) at the column temperature of 40 degrees C. The linear range of calibration curve was from 15.75 to 136.5 microg x mL(-1), the detection limit was 11.83 microg x mL(-1) with a concentration of 21 microg x mL(-1) of 2,3,5,4'-tetrahydroxystilbene-2-O-beta-D-glucoside, and the recovery was 102%-108%. The relative standard deviation was 3.45% (Cs = 21.0 microg x mL(-1), n = 3). The method has been applied to the determination of 2,3,5,4'-tetrahydroxystilbene-2-O-beta-D-glucoside in a few Chinese medicines, and the results were satisfactory. The method was simple, rapid and highly selective.

[Determination of Levofloxacin by chemiluminescence method].

A novel chemiluminescence method for the determination of Levofloxacin is based on its enhancement effect on thereaction of luminol with H2O2. The calibration graph is linear over the range of 5.53 x 10(-11)-2.21 x 10(-8) mol x L(-1) and the detection limit is 1.38 x 10(-11) mol x L(-1). The relative standard deviation (RSD) is 2.56% (n = 9). The method has been successfully applied to the determination of Levofloxacin in capsule samples.