Ground and excited-state electronic interactions in poly(propylene amine) dendrimers functionalized with naphthyl units: effect of protonation and metal complexation.

We report the absorption spectra and the photophysical properties (fluorescence spectrum, quantum yield, and lifetime) of four dendrimers of the poly(propylene amine) family (POPAMs) functionalized at the periphery with naphthylsulfonamide (hereafter called naphthyl) units. Each dendrimer Gn, where n = 1 to 4 is the generation number, comprises 2n + 1 (i.e., 32 for G4) naphthyl functions in the periphery and 2n + 1--2 (i.e., 30 for G4) tertiary amine units in the branches. All the experiments have been carried out in acetonitrile solutions. Comparison with two reference compounds (N-methyl-naphthalene-2-sulfonamide, A, and N-(3-dimethylamino-propyl)-2-naphthalene-1-sulfonamide, B) has shown that the absorption spectra of the dendrimers are significantly different from those expected from the component units. Furthermore, the intense fluorescence band of the naphthyl unit (lambda max = 343 nm; phi = 0.15, tau = 8.5 ns) is strongly quenched in the dendrimers. The quenching effect increases with increasing generation and is accompanied by the appearance of a weak and broad emission tail at lower energy. Protonation of the amine units of the dendrimers by addition of CF3SO3H (triflic) acid causes a strong increase in the intensity of the naphthyl luminescence and a change in the form of the emission tail. The shapes of the titration curves depend on dendrimer generation, but in any case, the effect of the acid can be fully reversed by successive addition of a base (tributylamine). The results obtained show that in the dendrimers there are interactions (both in the ground and excited states) between naphthyl units as well as between naphthyl units and amine units of the branches; this gives rise to dimer/excimer and charge-transfer/exciplex excited states. Titration with Zn(CF3SO3)2 has the same effect as acid titration, as far as the final emission spectrum is concerned, but a much higher concentration of Zn(CF3SO3)2 has to be used and the shapes of the titration plots are very different. Titration with Co(NO3)2.6H2O causes a much smaller increase in the intensity of the naphthyl fluorescence compared with Zn(CF3SO3)2. The results obtained have shown that protonation and metal coordination can reveal the presence of ground and excited state electronic interactions in functionalized poly(propylene amine) dendrimers, and that the presence of photo-active units in the dendrimers can be useful to reveal some peculiar aspects of the protonation and metal coordination processes.     

Countercurrent Chromatography for the Measurement of the Hydrophobicity of Sulfonamide Amphoteric Compounds

Octanol-water partition coefficients (P _o/w ) of 17 sulfonamides (SAs) were determined by countercurrent chromatography (CCC). The measured P _o/w values were in the 0.002–46 range (–2.65 < log P _o/w < 1.7). The lipophility of these compounds depends on the pH showing a maximum for intermediate values. The apparent P _o/w coefficients of SAs were obtained at 5 pH values: 2, 3, 5, 7 and 11, using 0.01 M ammonium phosphate octanol saturated buffers. A theoretical model linking these values with pH for amphoteric compounds was checked and verified. Often the P _o/w coefficients of the molecular forms obtained with the CCC method differ significantly from literature values obtained using softwares and/or from experimental values calculated with extrapolation. The CCC method allows also the determination of the P _o/w coefficients of the ionic forms of the SAs, cationic forms at low pH values and anionic forms at elevated pHs. The acidity constants were also estimated using the theoretical model. Relationships between SA retention factors obtained by RPLC and hydrophobicity were also discussed.     

聚(甲基丙烯酸-乙二醇二甲基丙烯酸酯)搅拌棒吸附萃取与液相色谱-质谱联用检测牛奶中的磺胺类药物

将聚(甲基丙烯酸-乙二醇二甲基丙烯酸酯) (poly(MAA-co-EDMA))聚合物原位聚合于玻璃内插管外表面上,得到一种多孔聚合物涂层;将其作为搅拌棒吸附萃取的萃取介质,考察了其对磺胺类药物的萃取性能;最后将其与高效液相色谱-电喷雾质谱(HPLC-ESI-MS)联用,建立了一种牛奶中4种磺胺类药物的检测方法。在最佳条件下,牛奶中4种磺胺类药物的检出限(S/N=3)和定量限(S/N=10)分别为0.11～0.52 μg/L和0.35～1.72 μg/L。在1～500 μg/L的范围内峰面积与质量浓度具有良好的线性关系,日内、日间测定的相对标准偏差不高于11.3%。结果表明,该方法简便、灵敏度高且成本低,适合于牛奶中磺胺类药物的检测。     

固相萃取技术在磺胺类药物残留分析中的研究进展

磺胺类药物(Sulfonamides,SAs)残留与食品安全水平息息相关。存在SAs残留的基质复杂多样,开发快速、高效、高选择性的前处理方法是检测的关键。固相萃取(SPE)具有较少的溶剂使用量、绿色环保、高选择性、高灵敏度、节省时间、成本低、能与不同检测手段兼容等特点,已被广泛应用于SAs残留的前处理过程。该文简要介绍了移液枪头式SPE、磁性SPE、分子印迹SPE、管内SPE和其他SPE模式,并总结了它们在SAs残留检测分析中的研究进展。     

Trace quantification of selected sulfonamides in aqueous media by implementation of a new dispersive solid‐phase extraction method using a nanomagnetic titanium dioxide graphene‐based sorbent and HPLC‐UV

Herein, a new dispersive solid‐phase extraction method using a nano magnetic titanium dioxide graphene‐based sorbent in conjunction with high‐performance liquid chromatography and ultraviolet detection was successfully developed. The method was proved to be simple, sensitive, and highly efficient for the trace quantification of sulfacetamide, sulfathiazole, sulfamethoxazole, and sulfadiazine in relatively large volume of aqueous media. Initially, the nano magnetic titanium dioxide graphene‐based sorbent was successfully synthesized and subsequently characterized by scanning electron microscopy and X‐ray diffraction. Then, the sorbent was used for the sorption and extraction of the selected sulfonamides mainly through π–π stacking hydrophobic interactions. Under the established conditions, the calibration curves were linear over the concentration range of 1–200 μg/L. The limit of quantification (precision of 20%, and accuracy of 80–120%) for the detection of each sulfonamide by the proposed method was 1.0 μg/L. To test the extraction efficiency, the method was applied to various fortified real water samples. The average relative recoveries obtained from the fortified samples varied between 90 and 108% with the relative standard deviations of 5.3–10.7%.     

超高压液相色谱-串联四极杆质谱法对牛奶中24种磺胺类药物残留的检测

利用超高压液相色谱-电喷雾串联四极杆质谱（UPLC-MS/MS）联用技术,建立了一种能在10 min内快速分离和测定牛奶中24种磺胺类药物残留的方法。样品经匀浆、超声、乙腈重复提取、氮吹浓缩,流动相溶解,饱和正己烷脱脂。采用ACQUITY UPLCTMBEHC18柱（100 mm&#215;2.1 mm i.d.,1.7μm）,以乙腈-0.2%乙酸水溶液（体积比1∶9）为流动相,梯度洗脱,目标分析物使用超高压液相色谱-电喷雾串联质谱进行测定;以保留时间和离子对进行定性和定量,在ESI（＋）和MRM监测模式下进行样品分析。该方法检出限（LOD）为0.04～1.35μg/kg;在1～200μg/L范围内线性关系良好,回收率为61%～117%,相对标准偏差为2.92%～18.98%。该法样品前处理简单、分析速度快、回收率和灵敏度高、检出限低,可以满足各国对牛奶中24种磺胺类药物的检测要求。     

Amino acids as selective sulfonamide acylating agents

Acylation of antimalarial and bacteriostatic sulfonamides with N-protected amino acids and peptides was carried out using standard peptide coupling methods. These acylation reactions are regioselective for the N⁴ nitrogen atom of diazine-containing sulfonamides. In contrast, only N¹ coupling was found for sulfisoxazole, an isoxazole-based sulfonamide. Computational studies suggest that a combination of geometrical, thermodynamic and electronic factors are responsible for the different reactivities reported.     

A Microtiter Plate Assay for Sulfonamides

Abstract

Sulfamethoxazole, sulfisoxazole, and sulfadiazine are sulfonamides used in the treatment of several infectious diseases. Several studies have demonstrated that the amino substituent plays an important role in both the toxicity and the therapeutic effect of these drugs. In view of these findings, a rapid and convenient method of analysis would be useful for monitoring selected patients receiving these drugs. With the increasing use of microtiter plate methodology in the clinical laboratory, an assay based upon the Bratton-Marshall reaction with the amino substituent was adapted to the microtiter plate format. The results indicate that the microtiter plate assay for sulfonamides retains the sensitivity and linearity necessary for analysis of sulfonamides in biological fluids at clinically relevant concentrations. The assay is simple, rapid, convenient, and suitable for monitoring procedures where only the measurement of the active drug concentration is required.     

An Unusual Occurrence in the Reaction of 4-Azasteroid Derivatives with N-Fluorodibenzenesulfonimide and Lithium Diisopropylamide

The reaction of N,N-diethyl-3-oxo-4-methyl-4-aza-5-androstane-17β-carboxamide(1) with N-fluorodibenzenesulfonimide(NFA) and lithium diisopropylamide(LDA) was studied.Under absolute anhydrous and anaerobic conditions,the formation of 5(2α-fluoro-4-methyl-3-oxo-4-aza-5α-androstane-17β-carboxylic acid methyl ester) can be rationalized by participating in the expected nucleophilic substitution reaction.Not in absolute anhydrous and anaerobic conditions,the formation of 10(N-di-isopropyl-N'-aryl-sulfonamides(C12H20N2O2S) and 11(N-diethyl-3-oxo-4-methyl-4-aza-5-androstene-17β-carboxamide) can be rationalized by assuming that the situ genera-ted carbanion 2 followed by a single electron transfer mechanism.5,10 and 11 were characterized.10 was a new compound and determined by X-ray single-crystal diffraction.Crystal data for 10:space group C2/c with a = 14.783(2),b = 7.6193(11),c = 24.663(3) ,β = 98.688(3)o,V = 2746.1(7) nm3,Mr = 256.36,Z = 8,Dc = 1.240 g/cm3,μ = 0.229 mm-1,F(000) = 1104,R = 0.0511 and wR = 0.1268.There exist intramolecular H-bonds which result in a supramolecular framework of the title compound.The formation mechanisms of 10 and 11 were also discussed briefly.     

Hydrogen‐bonded complexes of sulfonamides and thioamides with DMF: FT‐IR and DFT study,NBO analysis

The structure of H‐complexes of dimethylformamide (DMF) with N‐(2,2,2‐trichloro‐1‐hydroxyethyl)‐p‐toluenesulfonamide (1), N‐[1‐(4‐chlorophenylsulfonylamino)‐2,2,2‐trichloro)ethyl]dithiooxamide (2), N,N'‐bis[2,2‐dichloro‐1‐(4‐chlorophenylsulfonylamino)‐2‐phenylethyl]ethanebis(thioamide) (3) and N,N'‐bis[2,2,2‐trichloro‐1‐(phenylsulfonylamino)ethyl]ethanebis(thioamide) (3a) as proton donors was investigated using Fourier transform infrared spectroscopy and Density Functional Theory calculations. According to calculations, the interaction of DMF with the sulfonamide and thioamide NH groups in the complexes strongly affects the intramolecular H‐bonding in 1–3. From the natural bond orbital analysis, complexation with DMF strongly decreases the energy of the intramolecular N?H · · · S = C bonds, up to their rupture. Variation of the strength of the intra‐ and intermolecular H‐bonds in the complexes is consistent with the calculated frequencies of the NH and OH stretching vibrations, and the analysis of the corresponding bands in the IR spectra allows to suggest the preferable structure of the formed H‐complexes. Copyright © 2013 John Wiley & Sons, Ltd.