Ultra-trace level determination of nitrite in human saliva by spectrofluorimetry using 1,3,5,7-tetramethyl-8-(3,4-diaminophenyl)-difluoroboradiaza-s-indacene

A rapid, highly sensitive and selective fluorogenic method for the determination of traces of nitrite is described. It is based on the reaction of weakly fluorescent 1,3,5,7-tetramethyl-8-(3,4-diaminophenyl)-difluoroboradiaza-s-indacence (DAMBO) and nitrite in acidic aqueous solution to give 1,3,5,7-tetramethyl-8-(5-benzotriazolyl)-difluoroboradiaza-s-indacene (DAMBO-T), which is highly fluorescent. The optimum reaction conditions and other analytical parameters are investigated to enhance the sensitivity of the method. The fluorescence enhancement at 507 nm is linearly related to the concentration of nitrite in the range of 6.0 × 10⁻⁹–5.0 × 10⁻⁷ mol L⁻¹ with a correlation coefficient of R = 0.9995 (n = 10) and a detection limit of 1.0 × 10⁻¹⁰ mol L⁻¹. The R.S.D. is 1.12% (n = 10). The method is applied to the determination of nitrite in human saliva samples with the recoveries of 96. 24–105.30%. Correspondence: Ke-Jing Huang, Department of Chemistry, Wuhan University, Wuhan 430072, P.R. China     

Spectrofluorimetric determination of trace nitrite in food products with a new fluorescent probe 1,3,5,7-tetramethyl-2,6-dicarbethoxy-8-(3',4'-diaminophenyl)-difluoroboradiaza-s-indacene

A new fluorescent probe 1,3,5,7-tetramethyl-2,6-dicarbethoxy-8-(3′,4′-diaminophenyl)-difluoroboradiaza-s-indacene (TMDCDABODIPY) has been developed to detect nitrite in meat products and vegetables. The fluorescence of TMDCDABODIPY is very weak, but when it reacts with nitrite, a strong fluorescent triazole forms in aqueous medium at room temperature, which offers the advantage of specificity and sensitivity for the determination of nitrite. The fluorescence intensity was linear over a nitrite concentration of 9-300 nmol l⁻¹ with a detection limit of 0.21 nmol l⁻¹ (S/N = 3). The proposed method has been used for the determination of trace nitrite in food products with the recoveries of 94.62-105.48%.     

Ultrasound-assisted liquid-phase microextraction and high-performance liquid chromatographic determination of nitric oxide produced in PC12 cells using 1,3,5,7-tetramethyl-2,6-dicarbethoxy-8-(3',4'-diaminophenyl)-difluoroboradiaza-s-indacene

To reveal the function of nitric oxide (NO) that has been reported as an intracellular second messenger and a diffusible intercellular messenger, a novel ultrasound-assisted liquid-phase microextraction (ULPME) and high-performance liquid chromatographic method for the determination of NO produced in PC12 cells has been developed. 1,3,5,7-Tetramethyl-2,6-dicarbethoxy-8-(3',4'-diaminophenyl)-difluoroboradiaza-s-indacene (DAMBO-CO(2)Et) has been used for NO trapping to form corresponding triazole (DAMBO-CO(2)Et-T). The enrichment factor of DAMBO-CO(2)Et-T reached 150 in 2.5 min with the proposed ULPME method. NO produced in (200+/-5) PC12 cells has been determined directly with the detection limit (S/N=3) of 2.5 x 10(-13)mol/L (5a mol), which was the lowest in HPLC determination of NO reported yet. The proposed method was sensitive, selective, convenient and rapid, which has great prospect in the qualitative and quantitative determination of NO in minimal biological samples.     

Development of a novel fluorescent probe for nitric oxide detection: 8-(3',4'-diaminophenyl)-difluoroboradiaza-S-indacence

A novel fluorescent probe, 8-(3',4'-diaminophenyl)-difluoroboradiaza-S-indacence (DABODIPY), was designed and synthesized for monitoring nitric oxide production, which features high photostability and no pH dependency over a wide pH range. The fluorescence of 8-(3',4'-diaminophenyl)-difluoroboradiaza-S-indacence is very low, however, when the probe traps nitric oxide (NO) in the presence of dioxygen, the strong fluorescent triazole form is obtained, which offers the advantages of specificity, and sensitivity for direct detection of NO. Calibration using various concentrations of NO showed the method has good linearity (0.08-4.00 micromol l(-1)) and its detection limit is 10 nmol l(-1) (s/n = 3). The proposed method has been used to monitor the release of NO from S-nitrosocysteine, a NO-releasing agent.     

Spectrofluorimetric determination of total amount of nitrite and nitrate in biological sample with a new fluorescent probe 1,3,5,7-tetramethyl-8-(3',4'-diaminophenyl)-difluoroboradiaza-s-indacence

A new synthesized fluorescent probe, 1,3,5,7-tetramethyl-8-(3′,4′-diaminophenyl)-difluoroboradiaza-s-indacence (TMDABODIPY), has been used to detect nitrite. When TMDABODIPY reacted with nitrite, a weak fluorescent triazole formed in 0.2 mol l⁻¹ HCl medium at room temperature. The fluorescence quenching intensity was linear over a nitrite concentration of 0.04–0.32 μmol l⁻¹ with a detection limit of 0.3 nmol l⁻¹ (S/N=3). The proposed method has been applied to the determination of total amount of nitrite and nitrate (reduced by Zn powder) in human serum and urine of health and hypertension persons with recoveries of 91.83–101.80%.     

1,3,5,7-四甲基-2,6-二乙酯基-8-(3’,4’-二氨苯基)-二氟化硼-二吡咯甲烷荧光光度法灵敏测定血液中亚硝基硫醇

S-亚硝基硫醇在生物体内具有传递信号、改变蛋白质的结构和功能、阻止有害物质对细胞的伤害等重要的生理作用.建立了一种灵敏、简单的应用荧光探针1,3,5,7-四甲基-2,6-二乙酯基-8-(3',4'-二氨苯基)-二氟化硼-二吡咯甲烷标记并测定S-亚硝基硫醇的荧光光度法:在1.0×10-4mol/L Hg2+存在下,荧光探针与S-亚硝基硫醇在30℃反应15min生成衍生物,在激发和发射波长分别为500nm和510nm处测定其荧光强度.荧光强度和S-亚硝基硫醇的浓度在(8.0～800.0)×10-9mol/L范围内成良好的线性关系.当信噪比等于3时,方法的检出限为6.0×10-10mol/L.该方法对健康人与心血管疾病患者血液中S-亚硝基硫醇的测定的加标回收率为97.46%～103.10%.     

Selective spectrofluorimetric determination of glutathione in clinical and biological samples using 1,3,5,7-tetramethyl-8-phenyl-(2-maleimide)-difluoroboradiaza-s-indacene

This work reports the development of a selective, sensitive and rapid spectrofluorimetric method for the determination of reduced glutathione (GSH) in the presence of relatively high levels of cysteine (Cys) in clinical and biological samples using 1,3,5,7-tetramethyl-8-phenyl-(2-maleimide)-difluoroboradiaza-s-indacene (TMPAB-o-M). The fluorescence from TMPAB-o-M is strongly quenched by its maleimide moiety, but after reaction with thiol, the fluorescence is restored with a 350-fold intensity increase (fluorescence quantum yield from 0.002 to 0.73). In H₃Cit-Na₂HPO₄ buffer (pH 7.40), the derivatization is completed in just 5 min under 37 °C. The linear range is 0.005-0.2 μmol L⁻¹, with detection limit of 1.1 × 10⁻¹⁰ mol L⁻¹ (signal-to-noise ratio = 3). Almost all amino acids, including Cys, impose no interference even if present at relatively high concentrations (amino acids:GSH = 100:1, Cys:GSH = 1:1, molar ratio, C_GSH = 3 × 10⁻⁷ mol L⁻¹). The sample can be used directly without further treatment after the protein is removed. The developed method is precise with a relative standard deviation (R.S.D.) lower than 5.0% (n = 6) and has been applied to the determination of GSH in human blood and pig’s liver with recoveries between 94.4 and 105.6%.     

X-ray Structure of 1- (3' -Phenyl-4' -morpholinyl-2' 5' - dithiole-1' - ylidene)-3, 4-biscarboethoxy-2-thionaphthalene

1INTR0DUCTIONa-Thiocarbonylthioformamideshavebeensynthesizedsince1980[l-23,however,thereisn0reP0rtofthesecomP0undsrelatedtheirpropertiesandreactivities(3).Ac-cordingtothepublishedpapers('-",adithioketone,adithioesterandadithioth-ioesteraresnitablefort4 2JcycloadditionwithalkenicandacetylenicdienophileS.Wewanttoknowwhethera-thiocarbonylthioformamideshavethesamecharacters,thereforethereactionofathiobenzoylthioformmorpholine(1)withdiethylacetylenedicarboxylate(2)wasexplored.Theredultsshowth…     

Complexation equilibria between niobium(V) and 4-(4'H-1',2',4'-triazolyl-3'-azo)-2-methylresorcinol Extraction-spectrophotometric determination of niobium in pyrochlore-bearing rocks

The complexation equilibria between niobium(V) and 4-(1'H-1',2',4'-triazolyl-3'-azo)-2-methylresorcinol has been studied by spectrophotometric methods and graphical and numerical calculation methods. The 1:2 Nb:R complex species formed at pH 6.2 ( = 2.16 x 10(4) l.mole(-1).cm(-1) at 490 nm) allows the determination of 0.15-2.50 ppm Nb. A 1:1 Nb:R complex species can be extracted into n-butanol from 0.1-1.5M hydrochloric acid ( = 1.28 x 10(4) l.mole(-1) .cm(-1) at 510 nm) and Beer's law is obeyed over the range 0.77-4.64 ppm Nb. Interferences and their elimination have been studied and the methods applied to the determination of niobium in pyrochlore-bearing ores.     

Synthesis of 1-(3',4'-dihydroxyphenyl)-7-(4"-hydroxyphenyl)- 4hepten-3-one

Natural diarylheptanoids have significant bioactivities. Some of them are potent inhibitors against prostaglandin biosynthesizing enzyme (PG synthetase) and 5-lipoxygenase (LT synthetase)1-2. Compound 1 was firstly isolated from Alnus rubra bark3. So far its synthesis has not been reported yet. Herein, we report the synthesis of compound 1. Meantime, compound 24 was also obtianed as an intermediate. Compound 7 and 16 were converted to compound 10 and 18 respectively, because compound 1…     

Solid-state synthesis of poly(3',4'-dimethoxy-2,2':5',2"- terthiophene): comparison with poly(terthiophene) and poly(3',4'-ethylenedioxy-2,2':5',2"- terthiophene)

A new terthiophene monomer: 3',4'-dimethoxy-2,2':5',2"-terthiophene (TMT) was synthesized and characterized by 1H-NMR, 13C-NMR and FTIR. The solid-state oxidative polymerizations of TMT were performed in various ratios of oxidant (FeCl?) to monomer (TMT). The resulting polymers were characterized by 1H-NMR, FTIR, UV-vis-NIR, GPC, X-ray diffraction, CV, as well as TGA and conductivity measurements. The structure and properties of poly (TMT) were compared with those of polyterthiophene [poly(TT)] and poly (3',4'-ethylenedioxy-2,2':5',2"-terthiophene) [poly(TET)] prepared under the same polymerization conditions. After comparative analysis with poly(TT) and poly(TET), the effects of the dimethoxy substituent and FeCl? on the structural and physicochemical properties of the poly(TMT)s were discussed in depth. The comparison suggested that the dimethoxy-substituted polymer did not display higher crystallinity, thermal stability, conductivity and electrochemical activity than ethylenedioxy substituted one. The results also showed that the effect of FeCl? on poly(TMT) was similar that seen with the poly(TT), in which the oxidation degree, electrochemical activity and conductivity increased steadily with increasing [FeCl?/[TT] ratio. Furthermore, the poly(TMT) and poly(TT) are mostly made up of dimers with a small amount of higher molecular weight components.     

3-(2-二唑啉基)-色酮类化合物的合成研究

报道了取代的邻羟基苯乙酮(1a～1e)经Vilsmeier-Haack反应一步制得3-醛基色酮(2a～2e),2a～2e与取代的芳酰肼(3a～3c)缩合制得15个酰腙类化合物(4a～4o),4a～4o在醋酸酐作用下关环得15个3-(2-苝二唑啉基)-色酮(5a～5o),并通过元素分析,IR,~1H NMR和MS诺数据确证了上述化合物的结构。     

Hydrolytic reactions of guanosyl-(3',3')-uridine and guanosyl-(3',3')-(2',5'-di-O-methyluridine)

Hydrolytic reactions of guanosyl-(3',3')-uridine and guanosyl-(3',3')-(2',5'-di-O-methyluridine) have been followed by RP HPLC over a wide pH range at 363.2 K in order to elucidate the role of the 2'-hydroxyl group as a hydrogen-bond donor upon departure of the 3'-uridine moiety. Under neutral and basic conditions, guanosyl-(3',3')-uridine undergoes hydroxide ion-catalyzed cleavage (first order in [OH(-)]) of the P-O3' bonds, giving uridine and guanosine 2',3'-cyclic monophosphates, which are subsequently hydrolyzed to a mixture of 2'- and 3'-monophosphates. This bond rupture is 23 times as fast as the corresponding cleavage of the P-O3' bond of guanosyl-(3',3')-(2',5'-di-O-methyluridine) to yield 2',5'-O-dimethyluridine and guanosine 2',3'-cyclic phosphate. Under acidic conditions, where the reactivity differences are smaller, depurination and isomerization compete with the cleavage. The effect of Zn(2+) on the cleavage of the P-O3' bonds of guanosyl-(3',3')-uridine is modest: about 6-fold acceleration was observed at [Zn(2+)] = 5 mmol L(-)(1) and pH 5.6. With guanosyl-(3',3')-(2',5'-di-O-methyluridine) the rate-acceleration effect is greater: a 37-fold acceleration was observed. The mechanisms of the partial reactions, in particular the effects of the 2'-hydroxyl group on the departure of the 3'-linked nucleoside, are discussed.     

Evaluation of select variables in the ion chromatographic determination of F-, Cl-, Br-, NO(-)3, SO(-2)4, and PO(-3)4 in serum samples

A full experimental design at two levels is applied for the estimation of the significance of select factors that may influence the ion chromatography (IC) determination of F-, Cl-, Br-, NO(-)3, SO(-2)4, and PO(-3)4 in serum samples. The factors studied are various sample deproteinization procedures, eluent composition, and flow rates. Deproteinization using either acetonitrile-NaOH or ultrafiltration can be used in order to obtain a significant protein removal before IC analysis; however, the former is recommended because it is less time-consuming and cheaper. Better resolution is obtained when a sodium hydroxide solution is used as the eluent. There is no influence of the sample's deproteinization procedures on the chromatographic resolution.     

Extractive photometric determination of gold(III) with 1-(2',4',6'-trichlorophenyl)-4,4,6-trimethyl-(1H,4H)-2-pyrimidinethiol in presence of tri-iso-octylamine

Tervalent gold was determined spectrophotometrically as its anionic 1:4 gold-thiol complex extracted into chloroform from aqueous acidic medium (1.5M sulphuric acid) in the presence of tri-iso-octylamine. The complex exhibits maximum absorption at 480 nm (molar absorptivity 4.60 x 10(3) l.mole(-1).cm(-1)) and Beer's law is obeyed in the concentration range 5-50 microg of gold(III) per ml. The relative standard deviation and relative error, calculated from ten determinations of solutions containing 15 microg of gold(III) per ml were 1.0% and 0.8%. The method is simple, selective and reproducible. It permits separation of gold(III) from associated elements and its determination in synthetic mixtures.