Oil-in-water emulsions as suitable working media for the direct polarographic determination of aziprotryne and desmetryne from its organic extracts in water samples

The electroanalytical behavior of the reduction of the herbicides aziprotryne (2-azido-4-isopropylamino-6-methylthio-1,3,5-triazine) and desmetryne (4-isopropylamino-6-methylamino-2-methylthio-1,3,5-triazine) in oil-in-water emulsions is reported. This medium allows the differential pulse polarographic determination of these s-triazines directly from their sample extracts in an appropriate organic solvent. Sodium pentanesulfonate was chosen as the most suitable surfactant to be used as emulsifying agent, whereas ethyl acetate was selected as the organic solvent to form the emulsions. The peak current was maximum in a 0.3 mol L^–1 HClO₄ medium of the continuous aqueous phase for aziprotryne, and at pH 3.0 for desmetryne, and the potential became more negative as the pH increased for both herbicides. The limiting current is diffusion controlled and the electrode process is irreversible. Four electrons are involved in the overall electrochemical reduction process as determined by controlled potential coulometry, whereas the αn_a values suggested that two electrons are involved in the rate-determining step. Using differential pulse polarography, aziprotryne and desmetryne can be determined in the emulsified medium over the concentration ranges 1.0 · 10^–7–1.0 · 10^–4 mol L^–1, with limits of detection of 4.5 · 10^–8 mol L^–1 and 6.6 · 10^–8 mol L^–1, respectively. The method was applied to the determination of aziprotryne and desmetryne in spiked irrigation water. At concentration levels of 6.0 · 10^–7 mol L^–1 aziprotryne and 4.0 · 10^–7 mol L^–1 desmetryne, recoveries of 94 ± 3% and 94 ± 4%, respectively, were obtained after preconcentration on Sep-Pack C₁₈ cartridges. Finally, partial least-squares regression (PLSR) has been used for treatment of the polarographic data obtained from mixtures of aziprotryne, desmetryne and simazine in oil-in-water emulsions. The size of the calibration set was of 29 samples by ninety two current measurements at different potentials. Prediction of the herbicides concentration within the range 1.0 · 10^–6 –1.0 · 10^–5 mol L^–1 was possible.     

Determination of the herbicide desmetryne in organised media by adsorptive stripping voltammetry

An electroanalytical method for the determination of the herbicide desmetryne at nanomolar levels in dispersed media, based on adsorptive stripping voltammetry, is reported. The adsorption of desmetryne at the hanging mercury drop electrode was checked both in micellar solutions, where the anionic surfactant sodium pentanesulphonate was chosen as the most suitable surfactant agent, and in oil-in-water emulsions prepared with ethyl acetate as the organic solvent. In a micellar medium formed with 0.02% sodium pentanesulphonate and with 0.1 mol l(-1) Britton-Robinson buffer (pH 1.5), the herbicide could be determined over the 1.0 x 10(-8)-4.0 x 10(-7) mol l(-1) concentration range, when an accumulation potential of -0.70 V was applied for 50 s. On the other hand, in an oil-in-water emulsion formed with 2% ethyl acetate and 0.04% sodium pentanesulphonate as emulsifying agent in 0.1 mol l(-1) HClO(4), desmetryne could be determined over the 2.0 x 10(-9)-1.0 x 10(-7) mol l(-1) concentration range. The limits of detection were 2.4 x 10(-9) and 4.2 x 10(-10) mol l(-1) in micellar and emulsified media, respectively, with R.S.D.s (n=10) 3.6 and 3.7%. The degree of interference from some other s-triazines on the desmetryne differential pulse response was also evaluated. Finally, the method developed in emulsified medium was applied to the determination of desmetryne in spiked apple juice.     

Synthesis,polarography and herbicidal activity of quaternary salts of 2-(4-pyridyl)-1,3,5-triazines, 5-(4-pyridyl)pyrimidine, 2-(4-pyridyl)pyrimidine and related compounds

2-(4-Pyridyl)-1,3,5-triazine, 2-(4-pyridyl)-4-methyl-1,3,5-triazine, 2-(4-pyridyl)-4,6-dimethyl-1,3,5-triazine and 2-(4-pyridyl)pyrimidine have been prepared by modification of established triazine and pyrimidine syntheses. These compounds and some of their relatives have been converted to quaternary pyridinium salts. The polarographic reduction potentials of the salts in aqueous solution are pH dependent. The activity of the salts as post-emergent herbicides is reported.     

EC(EE) processes in the reduction of some 2-methylthio-4,6-di(alkylamino)-1,3,5-triazines on mercury electrodes

Polarographic (direct current, dc, and differential pulse, DP) studies of the electroreduction of the s-triazine derivatives ametryn (2-methylthio-4-ethylamino-6-isopropylamino)-1,3,5-triazine), dimethametryn (2-methylthio-4-ethylamino-6-(1,2-dimethylpropyl) amino-1,3,5-triazine) and simetryn (2-methylthio-4,6-di(ethylamino)-1,3,5-triazine) were made in the acidity range from 2.25 M H₂SO₄ to pH 6.5. Above this last pH value no signals were obtained. In DP polarography, two main reduction peaks were observed, accompanied by a pre-peak due to the adsorption of the herbicides on the electrode. The main peaks corresponded to two-electron irreversible reduction processes, at pH values higher than the protonation pK of the triazine ring (ca. 4). In this pH range, the protonation of the triazine ring preceding the reduction process is responsible for decrease in limiting current. At pH<pK the herbicides suffer a cleavage of the –SCH₃ group via two different intermediates related by a chemical reaction, whose extension depends on the herbicide.     

Determination of lomefloxacin, an antibacterial drug, in pharmaceutical preparations based on its polarographic catalytic wave in the presence of 2-iodoacetamide.

In a 0.125 mol/L phosphate (pH 6.6)/2.5 x 10(-4) mol/L 2-iodoacetamide solution, lomefloxacin yields a response of a polarographic catalytic current. The second-order derivative peak current of the catalytic wave of lomefloxacin is proportional to its concentration in the range of 1.0 x 10(-8)-1.0 x 10(-6) mol/L (r = 0.998). The sensitivity of the catalytic wave is 25-times higher than that of the corresponding reduction wave for 5.0 x 10(-7) mol/L lomefloxacin. The proposed method was applied to the determination of lomefloxacin in pharmaceutical preparations. The polarographic reduction wave is ascribed to a one-electron reduction of the C=C bond of lomefloxacin zwitterion accompanied by an acid-base equilibrium. The catalytic wave should be caused by regeneration of the lomefloxacin molecule at electrode surface due to the one-electron reduction product being further oxidized by electroreductive intermediate products of 2-iodoacetamide.     

Modeling of 2,4-dichlorophenoxyacetic acid controlled-release kinetics from lignin-based formulations

The second Fick’s law of diffusion, considering boundary conditions that at both slab faces the concentration of herbicide is equal to zero (sink conditions), has been adequate to describe our kinetic data obtained from experiments on 2,4-dichlorophenoxyacetic acid, (2,4-D) released from lignin-based formulations in a water static bath system. However, the same model proved to be invalid in describing the experimental data obtained with ametryn (2-ethylamino-4-isopropylamino-6-methylthio-1,3,5-triazine) and diuron (3-[3,4-dichlorophenyl]-1,1-dimethylurea) formulations in a water dynamic bath system. For ametryn and diuron formulations, because of the lower aqueous solubility of these herbicides, it was necessary to model a stagnant film at the formulation surface to describe better the release kinetics because the model incorporating sink conditions is insufficient. This study presents a new mathematical modeling of experimental data obtained with 2,4-D formulations in a water static bath system. The new model incorporates a stagnant film as the boundary condition at the formulation surface, and its diffusion coefficient value is more precise than the one estimated by the model employing sink conditions.     

Cyanuric chloride catalyzed mild protocol for synthesis of biologically active dihydro/spiro quinazolinones and quinazolinone-glycoconjugates

We have developed an efficient cyanuric chloride (2,4,6-trichloro-1,3,5-triazine, TCT) catalyzed approach for the synthesis of 2,3-dihydroquinazolin-4(1H)-one (3a-3x), 2-spiroquinazolinone (5, 7), and glycoconjugates of 2,3-dihydroquinazolin-4(1H)-one (10a, 10b) derivatives. The reaction allows rapid cyclization (8-20 min) with 10 mol % cyanuric chloride to give skeletal complexity in good to excellent yield. We believe that this novel procedure may open the door for the easy generation of new and bioactive quinazolinones.     

血红蛋白模拟过氧化物酶催化反应体系的极谱分析

用极谱分析法研究了血红蛋白催化H2O2氧化邻苯二胺(OPD)的反应体系.血红蛋白具有类似过氧化物酶的功能,它能够催化OPD-H2O2的反应生成一种具有电化学活性的产物,该产物在滴汞电极上-0.64V(vs.SCE)产生一个峰形良好的极谱还原峰.优化了血红蛋白的催化反应条件和催化反应产物的极谱测定条件 在最佳条件下,该体系可用于血红蛋白含量的测定,线性范围为2.0×10-9～2.0×10-7mol/L,检测限为1.0×10-9mol/L;也可用于痕量H2O2的测定,线性范围为1.0×10-6～2.0×10-4mol/L,检测限为1.0×10-6mol/L.     

2,4,6-tri(3,5-Dimethylpyrazoyl)-1,3,5-triazine modified carbon paste electrode for trace Cobalt(II) determination by differential pulse anodic stripping voltammetry

A differential pulse anodic stripping voltammetry was developed for the sensitive and selective determination of Co(II) at 2,4,6-tri(3,5-dimethylpyrazoyl)-1,3,5-triazine modified carbon paste electrode in 0.1 mol l(-1) NH(4)Cl solution (pH 4.95). The oxidation peak of Co(II) was observed at 0.03 V(vs. Ag/AgCl) by scanning the potential in a positive direction. The analysis procedure consisted of an open circuit accumulation step in stirred sample solution. This was followed by medium exchange to a clean solution and subsequently an anodic potential scan was effect to obtain the voltammetric peak. The current was proportional to the concentration of the Co(II) ion in a range of 1x10(-8)-1x10(-6) mol l(-1) for 3 min accumulation and in the range of 1x10(-9)-1x10(-8) mol l(-1) for 5 min accumulation; most of metal ions do not interfere with the determination. The developed method was applied to Co(II) determination in potable water.     

Determination of nicotinamide (NA) using its polarographic catalytic wave in the presence of KIO3

Nicotinamide (NA) yields a polarographic catalytic wave with a peak potential -1.38 V (vs. SCE) in 0.1 mol/L HAc-NaAc (pH 4.7)/4 x 10(-3) mol/L KIO3 buffer solution. The sensitivity of the catalytic wave increased in one order of magnitude as compared to that of the responding reduction wave without KIO3. Based on this observation, a new method for the determination of NA was recommended. The second order derivative peak current was proportional to the NA concentration in the range of 5 x 10(-8)- 6 x 10(-7) mol/L. 0.11-fold vitamin B1, 0.13-fold B2, 0.14-fold B6 and 8-fold nicotinic acid amounts do not interfere the determination of 1 x 10(-6) mol/L NA. The proposed method was used to determine the NA content in multivitamin tablets, with good agreement to the declared amount.     

Simultaneous square-wave voltammetric determination of aspartame and cyclamate using a boron-doped diamond electrode

A simple and highly selective electrochemical method was developed for the simultaneous determination of aspartame and cyclamate in dietary products at a boron-doped diamond (BDD) electrode. In square-wave voltammetric (SWV) measurements, the BDD electrode was able to separate the oxidation peak potentials of aspartame and cyclamate present in binary mixtures by about 400 mV. The detection limit for aspartame in the presence of 3.0x10(-4) mol L(-1) cyclamate was 4.7x10(-7) mol L(-1), and the detection limit for cyclamate in the presence of 1.0x10(-4) mol L(-1) aspartame was 4.2x10(-6) mol L(-1). When simultaneously changing the concentration of both aspartame and cyclamate in a 0.5 mol L(-1) sulfuric acid solution, the corresponding detection limits were 3.5x10(-7) and 4.5x10(-6) mol L(-1), respectively. The relative standard deviation (R.S.D.) obtained was 1.3% for the 1.0x10(-4) mol L(-1) aspartame solution (n=5) and 1.1% for the 3.0x10(-3) mol L(-1) cyclamate solution. The proposed method was successfully applied in the determination of aspartame in several dietary products with results similar to those obtained using an HPLC method at 95% confidence level.     

Reactions of triacetylmethane with monosubstituted hydrazines and amidine analogues. Syntheses of 4-acetyl-3,5-dimethylpyrazole amidinohydrazone and 1,3,5-triazine derivatives

Triacetylmethane ( 1 ) reacts with amidinohydrazines in acidic medium to afford 4-acetyl-3,5-dimethylpyrazole amidinohydrazone derivatives 2,4 . However, a similar reaction of 1 with thiosemicarbazide or semicarbazide led mainly to 3,5-dimethylpyrazole ( 6 ). The great propensity of 1 to hydrolysis accounts for this last transformation, as well as for the fact that with guanidine it led to 2-amino-4,6-dimethylpyrimidine ( 10 ) and with S-methylisothiourea it provided the unexpected 2-amino-4-methyl-6-methylthio-1,3,5-triazine ( 11 ).     

Increased sensitivity of an enzyme immunoassay (ELISA) for the determination of triazine herbicides by variation of tracer incubation time

Immunoassays for triazine herbicides were tested for their reaction to the variation of the tracer incubation time. By application of a sequential technique the measuring range of atrazine could be expanded to five decades and the total duration of the test could be reduced to about 30 min. In an optimized version a lower detection limit of 9 pmol/l (2 ng/l) was achieved. The detection limit of a sensitive immunoassay for terbuthylazine is also below the concentration limit demanded of the German drinking water regulation (100 ng/l) and reaches 130 pmol/l (30 ng/l). Short tracer incubation times did not lead to increased cross-reactivities in contrast to theoretical models [1, 2]. Different mechanisms, which could cause a shift of the center point of the calibration curve, are discussed, including kinetic considerations.Nomenclature ametryn 2-(ethylamino)-4-(isopropylamino)-6-(methylthio)-1,3,5-triazine - atrazine 2-(chloro)-4-(ethylamino)-6-(isopropylamino)-1,3,5-triazine - deethylatrazine 2-(amino)-4-(chloro)-6-(isopropylamino)-1,3,5-triazine - DMSO dimethylsulfoxide - DOC dissolved organic carbon - ELISA enzyme-linked immunosorbent assay - glyme 1,2-dimethoxyethane - hydroxyatrazine 2-(ethylamino)-4-(hydroxy)-6-(isopropylamino)-1,3,5-triazine - PBS phosphate buffered saline - propazine 2-(chloro)-4,6-bis(isopropylamino)-1,3,5-triazine - simazine 2-(chloro)-4,6-bis(ethylamino)-1,3,5-triazine - terbuthylazine 2-(tert-butylamino)-4-(chloro)-6-(ethylamino)-1,3,5-triazine - TLC thin-layer chromatography - TMB 3,3,5,5-tetramethylbenzidine - tracer enzyme (peroxidase) labeled hapten     

A novel water-soluble fluorescent probe for the determination of methylamine

A novel water-soluble fluorescent probe, monosodium 7-(4,6-dichloro-1,3,5-triazinylamino)-1,3-naphthalenedisulfonic acid (DTND), was synthesized by reacting cyanuric chloride with 7-amino-1,3-naphthalenedisulfonic acid monopotassium salt at 0-5 degrees C. This new reagent was used for the determination of methylamine. The linear range is 3x10(-6)-2x10(-4) mol L(-1) with a detection limit (S/N=3) of 7.2x10(-8) mol L(-1), and the relative S.D. is 1.3% for ten replicate determinations of 1x10(-5) mol L(-1) CH3NH2. Common species in the aqueous environment have no or only slight influence on the determination. The method can be used to determine methylamine in real water samples.     

均三氮苯类除草剂结构与活性的理论研究

利用Gaussian03程序包中的B3LYP方法,选择6-31G基组对均三氮苯类除草剂及类似衍生物2-(4-溴苄氨基)-4-甲基-6-三氟甲基-1,3,5-三氮苯进行了量子化学计算,从理论上讨论了它们的空间结构、电子结构特征与活性的关系.计算结果表明:三氮苯环与N(7)和N(8)原子形成了共轭结构,分子活性大小与LUMO轨道的得电子能力以及在LUMO轨道中占主要成分的原子有重要关系.N(7)和N(8)连接单个具有推电子能力的基团,有利于生物活性的提高.对于2-(4-溴苄氨基)-4-甲基-6-三氟甲基-1,3,5-三氮苯中,N(8)和C(9)是重要的活性部位,和传统的均三氮苯类除草剂分子相比,与D1蛋白上不同的氨基酸残基发生了键合作用.     

An unmediated hydrogen peroxide biosensor based on hemoglobin incorporated in a montmorillonite membrane

Hemoglobin was incorporated in a montmorillonite membrane. Electrochemical and spectroscopic studies revealed that the electron transfer reactivity and peroxidase activity of the protein were both enhanced. Nevertheless, its structure was still maintained native-like in the membrane. An unmediated hydrogen peroxide biosensor was accordingly prepared. The calibration plot of this H202 sensor was linear in the range of 1.0 x 10(-6)-6.0 x 10(-4) mol L(-1). The relative standard deviation was 3.1% for six successive determinations at a concentration of 1.0 x 10(-4) mol L(-1). The detection limit was 6.0 x 10(-7) mol L(-1). Possible interferences in real sample analyses are discussed.     

四种阴离子的毛细管电泳电导检测(英文)

 采用柠檬酸 柠檬酸钠作为缓冲体系 ,使用负高压 ,对Cl-,NO3 -,HCO3 -和H2 PO4 -等 4种常见阴离子进行了分离检测 ,研究了缓冲剂的种类、浓度、pH值及操作电压对分离的影响。在选定的条件下 ,4种离子的定量线性范围 :Cl-5 0× 10 -5mol/L～ 2 5× 10 -3 mol/L ,NO3 -6 0× 10 -5mol/L～ 2 0× 10 -3 mol/L ,HCO3 -5 0× 10 -6mol/L～ 2 0× 10 -4 mol/L ,H2 PO4 -6 0× 10 -5mol/L～ 1 0× 10 -3 mol/L ;检出限 :Cl-1 5× 10 -5mol/L ,NO3 -3 0×10 -5mol/L ,HCO3 -1 0× 10 -6mol/L ,H2 PO4 -2 0× 10 -5mol/L ;峰面积的RSD (n =6 ) :Cl-3 1% ,     

1，2，4－三嗪类化合物研究（XXIV）──吡唑并－（5，4－e）－1，2，4－三嗪衍生物的合成

先合成１，２，４－三嗪环，然后并接吡唑环，对标题化合物进行了合成研究。对１，２，４－三嗪环上的硫化反应进行了改进，解决了３个反应活性相近部位的选择性肼解问题；并发现了肼基与乙酸乙酯于室温下反应生成１，３，４－　二唑环的新反应。     

An immunoassay for terbutryn using direct hapten linkage to a glutaraldehyde network on the polystyrene surface of standard microtiter plates

2-Aminobutylamino-4-ethylamino-6-isopropylamino-1,3,5-triazine (ABA-atrazine) has been synthesized and used as a coating hapten in an immunoassay with a monoclonal antibody against terbutryn. Coating was achieved by covalently linking ABA-atrazine to a glutaraldehyde polymer network directly bound to the polystyrene surface of a standard 96-well microtiter plate. The assay was carefully optimized. In particular, the coating hapten concentration had a strong effect on the ELISA sensitivity. By including a pre-incubation step a low test midpoint (IC50-value) of 0.130 microg L(-1) was achieved. As far as we are aware this is the most sensitive ELISA for terbutryn yet reported. The coating-hapten-format presented is proposed as generally applicable, because the glutaraldehyde-modified microtiter plate surface enables stable immobilization of a broad variety of coating haptens.     

Fluorimetric study of the interaction between human serum albumin and quinolones-terbium complex and its application

A highly sensitive spectrofluorimetric method is proposed for determination of human serum albumin (HSA) and some quinolone drugs. Using quinolones-terbium (Tb3+) complex as a fluorescent probe, in the buffer solution of pH 7.8, HSA can remarkably enhance the fluorescence intensity of the quinolones-Tb3+ complex at 545 nm and the enhanced fluorescence intensity of Tb3+ ion is in proportion to the concentration of HSA and quinolone drugs. Optimum conditions for the determination of HSA were also investigated. The linear ranges and limits of detection are 8.0 x 10(-9) to 8.0 x 10(-8) mol L(-1), 4.20 x 10(-9) mol L(-1) (for HSA); 1.0 x 10(-6) to 4.0 x 10(-6) mol L(-1), 1.87 x 10(-8) mol L(-1) (for norfloxacin) and 1.0 x 10(-7) to 1.0 x 10(-6) mol L(-1), 4.82 x 10(-8) mol L(-1) (for enoxacine), respectively. This method is simple, practical and relatively free interference from coexisting substances, as well as much more sensitive than most of the existing assays.