Shuangming Meng

Preconcentration and determination of trace elements with 2-aminoacetylthiophenol functionalized Amberlite XAD-2 by inductively coupled plasma–atomic emission spectrometry

2-Aminoacetylthiophenol (AATP)-modified Amberlite XAD-2 has been synthesized by coupling it through NNNH group. The resulting chelating resin, characterized by elemental analysis, thermogravimetric analysis (TGA) and infrared (IR) spectra, was used to preconcentrate Cd, Hg, Ag, Ni, Co, Cu and Zn ions. Several parameters, such as distribution coefficient and sorption capacity of the chelating resin, pH and flow rates of uptake and striping, volume of sample and eluent, were evaluated. The effects of electrolytes and cations on the preconcentration were also investigated. The recoveries were >96%. The procedure was validated by standard addition and analysis of a standard reference sediment material (GBW 07309 China). The developed method was utilized for preconcentration and determination of Cd, Hg, Ag, Ni, Co, Cu and Zn in tap water, river water and sediment samples by inductively coupled plasma-atomic emission spectrometry (ICP-AES) with satisfactory results. The 3sigma detection limits for Cd, Hg, Ag, Ni, Co, Cu and Zn were found to be 0.10, 0.23, 0.41, 0.13, 0.25, 0.39 and 0.58mugl(-1), respectively. The relative standard deviation of the determination was <10%.

Solid-phase spectrophotometric determination of nickel in water and vegetable samples at sub-μg l−1 level with o-carboxylphenyldiazoaminoazobenzene loaded XAD-4

A highly sensitive and selective solid-phase spectrophotometric method for the determination of sub-mugl(-1) level nickel(II) is described. Nickel(II) was sorbed on a styrene-divinylbenzene-type resin Amberlite XAD-4 as a Ni(II)-o-carboxylphenyldiazoaminoazobenzene (o-CDAA) complex. At pH 9.0, resin phase absorbances at 588 and 800nm were measured directly with an apparent molar absorptivity of 2.95x10(7)gmol(-1)cm(-1). The linear range of the determination was 1.2-41mugg(-1) resin. The detection limit and the quantification limit were found to be 0.24 and 0.76mugg(-1) resin, respectively. The relative standard deviation of 10 replicate determinations of 1.0mug nickel(II) in 100ml sample was of 1.5%. The tolerance limit of coexistent ions was also investigated. Most of them are in tolerable amount. For practical analyses, 1ml acetylacetone used can eliminate the interferences caused by Cu and Fe. The procedure was validated by analysis a certified water reference material (GBW 08618 Beijing, China) and a tomato leaf certified reference material (GBW 08402 Beijing, China) with the results in agreement with the certified values. The method was applied to the determination of nickel(II) in water and vegetable samples with satisfactory results.

Spectrophotometric determination of lead in vegetables with dibromo-p-methyl-carboxysulfonazo

A new highly sensitive and selective chromogenic reagent dibromo-p-methyl-carboxysulfonazo (DBMCSA) was synthesized and studied for the spectrophotometric determination of lead in detail. In 0.25 M phosphoric acid medium, which greatly increases the selectivity, lead reacts with DBMCSA to form a 1:2 blue complex, having a sensitive absorption peak at 648 nm. Under the optimal conditions, Beers law is obeyed over the range from 0 to 0.8 mugml(-1) Pb(II) and the apparent molar absorptivity is 1.04x10(5) lmol(-1)cm(-1). The detection limit and the variation coefficient were found to be 2.14 ngml(-1) and 1.0%, respectively. It is found that, except for Ca(II) and Ba(II), all foreign ions studied do not interfere with determination. The interference caused by Ca(II) and Ba(II) can be easily eliminated by prior extraction with potassium iodide-methylisobutylketone. The method has been applied to the determination of lead in vegetables with satisfactory results.

3-Phenyl-2-(piperidin-1-yl)-3,5,6,8-tetra­hydro-4H-thio­pyrano[3′,4′:2,3]thieno[5,4-d]pyrimidin-4-one

In the title compound, C20H21N3OS2, the piperidinyl ring has a distorted chair conformation. Weak intermolecular C—H⋯O hydrogen bonds link the molecules into centrosymmetric dimers. The crystal packing exhibits short intermolecular S⋯S distances of 3.590 (2) Å.

Spectrophotometric determination of thorium in food using 2-(2,5-disulfonic-4-methoxyphenylazo)-7-(2-hydroxyl-5-carboxylphenylazo)-1,8-dihydroxynaphthalene-3,6-disulfonic acid

A new highly sensitive and selective chromogenic reagent, 2-(2,5-disulfonic-4-methoxyphenylazo)-7-(2-hydroxyl-5-carboxylphenylazo)-1,8-dihydroxynaphthalene-3,6-disulfonic acid (1), was synthesized and applied to the spectrophotometric determination of trace thorium. In 5 mL of a 6 M perchloric acid medium, which greatly increases the selectivity, thorium reacts with 1 to form a 1: 2 green complex, having a sensitive absorption peak at 670 nm. Under optimal conditions, Beer’s law is obeyed over the range from 0 to 0.8 μg/mL Th(IV) and the apparent molar absorptivity is 2.09 × 105 L/mol cm. It is found that, uranium(VI), Ti(IV), heavy rare earths, and most of other common metal ions do not interfere. The method has been tested on the determination of thorium in food samples with satisfactory results.

Solid Phase Extraction and Preconcentration of Trace Heavy Metal Ions in Natural Water with 2,2′‐Dithiobisaniline Modified Amberlite XAD‐2

Abstract A solid phase extraction and preconcentration methodology utilizing a new chelating resin is described for the separation of Cd, Ni, Co, Cu, and Zn. The chelating resin matrix was prepared by covalently linking 2,2′‐dithiobisaniline synthesized from 2‐aminothiophenol with the benzene ring of polystyrene‐divinylbenzene resin Amberlite XAD‐2 through a –N˭N– group. Its adsorption and preconcentration behavior for Cd, Ni, Co, Cu, and Zn in aqueous solution was studied using batch and column procedures in detail. The newly designed resin quantitatively adsorbs Cd, Ni, Co, Cu, and Zn above pH 5.0. Subsequent elution with 2 M HCl readily strips the sorbed metal ions from the resin. The sorption capacity is 360, 230, 170, 200, and 150 mol g−1 for Cd, Ni, Co, Cu, and Zn, respectively. Their preconcentration factors are 80–200. The time for 80% sorption was less than 10 min for all five metal ions. The effects of electrolytes on the preconcentration were also investigated with the recoveries >95%. The procedure was validated by analysis of a standard reference river sediment material (GBW 08301 China). The developed method was successively utilized for the determination of Cd, Ni, Co, Cu, and Zn in tap water and river water by flame atomic absorption spectrometry (FAAS) after column SPE and preconcentration. The 3σ detection limits for these metal ions were found to be 0.10, 0.34, 0.42, 0.16, and 0.52 g L−1, respectively. The relative standard deviation was <10% for the determination of 10 g each of Cd, Ni, Co, Cu, and Zn in a 100 mL water sample.

(E)-N'-(Furan-2-ylmethyl-ene)-4-(quinolin-8-yl-oxy)butanohydrazide.

In the title molecule, C18H17N3O3, the dihedral angle between the mean planes of the furan ring and the quinoline group is 77.4 (2)°. In the crystal structure, intermolecular N—H⋯N hydrogen bonds link the molecules into centrosymmetric dimers.

Facile Synthesis of Thieno[2,3-d]pyrimidine Derivatives Using Inorganic Base Catalysis

Abstract Potassium carbonate as inorganic base catalyst was used to develop an efficient synthetic procedure for the preparation of thieno[2,3-d]pyrimidine derivatives. The molecular structure of the newly synthesized compounds were confirmed by NMR spectral data. GRAPHICAL ABSTRACT

Preparation of cobalt hydroxide film modified electrode and its analytical application

Cobalt hydroxide film modified electrode was prepared by depositing cobalt hydroxide on glassy carbon electrode (GCE) surface in an alkaline aqueous solution and then characterized by cyclic voltammetry. The electrochemical behavior of resorcin on the film modified electrode was investigated. The results show that cobalt hydroxide films in alkaline solutions have good electrocatalytical activity towards the oxidation of resorcin. The recovery of resorcin from sample ranged from 95.2 to 103.4% and the oxidation peak currents were directly proportional to the resorcin concentration from 5.0 × 10−6 to 1.05 × 10−4 M with correlation coefficient of 0.9986. A detection limit of 1.0 × 10−7 M for resorcin was estimated. Various factors affecting the electrocatalytical activity of cobalt hydroxide film were investigated in detail. Real water samples were analyzed and satisfactory results were obtained.

Spectrophotometric determination of trace copper(II) in biological samples with 2,4-bis(4-phenylazophenylaminodiazo)phenol

A highly sensitive and selective chromogenic reagent 2,4-bis(4-phenylazophenylaminodiazo)phenol (BPPAAP) reacted with copper(II) to form a highly stable complex in the ethanolic solution at pH range of 9.0–12.0. The Cu(II)-BPPAAP complex showed maximum absorbance at 540 nm, with molar absorptivity being 1.86 × 105 L/mol cm. Beer’s law was obeyed over the range 0–0.2 μg/100 mL of copper(II) and variation coefficient is found to be 2.4–4.8%. The detection and quantification limit of the method are 2.0 and 6.5 ng/mL, respectively. To eliminate the interference of foreign ions, a convenient and efficient method using a column packed with sulfhydryl dextrose gel as a solid-phase extractant was utilized with satifactory reults. The developed method has been successfully employed for the determination of copper(II) in the biological samples.