Yue-Qin Fan

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.

(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.

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 cadmium in vegetables with 3,5-bis(4-phenylazophenylaminodiazo)benzoic acid

A new highly sensitive and selective chromogenic reagent, 3,5-bis(4-phenylazophenylaminodiazo)benzoic acid (BPPABA) has been synthesized and applied to the determination of trace cadmium(II) in vegetables. The method is based on the color reaction between BPPABA and cadmium (II). In the presence of Triton X-100, cadmium(II) reacts with BPPABA in Na2B4O7-NaOH buffer solution (pH 10.5), forming red complex with maximum absorption at 530 nm. Under the optimal conditions, Beer’s law is obeyed within 0–12 μg of cadmium within 25 mL of solution, and the apparent molar absorptive coefficient of the complex is 2.8 × 105 L/mol cm. The detection limit and the relative standard deviation were found to be 0.92 μg/L and 1.0%, respectively. Interference of foreign ions was also investigated. Most of the metal ions are tolerated in considerable amounts except for Hg(II), Cu(II) and Ni(II). To eliminate the interference of foreign ions, metal ion imprinted polymer technique was utilized.

Spectrophotometric determination of nickel in biological samples using 1-azobenzene-3-(3-hydroxyl-2-pyridyl)-triazene

A new sensitive and selective chromogenic reagent, 1-azobenzene-3-(3-hydroxyl-2-pyridyl)-triazene (ABHPT), was synthesized. It has been found that ABHPT reacts with nickel(II) in a borax buffer solution (pH 10.0) to form 2: 1 red complexes with the maximum absorption at 530 nm. The apparent molar absorptivity of the complex is 2.6 × 105 L/(mol cm). Most metal ions can be tolerated in considerable amounts, whereby only zinc and mercury may interfere with the determination of nickel(II). Nevertheless, this can be easily eliminated by prior separation with sulfhydryl dextran gel. A new method for the spectrophotometric determination of trace nickel(II) was developed. Beer’s law is obeyed for 0–15 μg of nickel(II) in 25 mL of solution. The limit of quantification, limit of detection, and relative standard deviation are 0.74 ng/mL, 0.25 ng/mL, and 1.0%, respectively. The method has been applied to the determination of trace nickel(II) in biological samples with satisfactory results.

Ethyl 2-amino-6-benzyl-4,5,6,7-tetra-hydro-thieno[2,3-c]pyridine-3-carboxyl-ate.

In the title compound, C17H20N2O2S, the tetrahydropyridine ring adopts an envelope conformation with the N atom at the flap position; the phenyl ring makes a dihedral angle of 81.06 (10)° with the thiophene ring. The amino group links with the carbonyl O atom via intramolecular N—H⋯O hydrogen bonding, forming a six-membered ring. In the crystal, intermolecular N—H⋯O hydrogen bonds link the molecules into infinite chains running along the b axis.

N-Phenyl­morpholine-4-carboxamide

In the title compound, C11H14N2O2, the urea-type NC=ON moiety [planar to within 0.0002 (13) Å] is inclined to the phenyl ring by 42.88 (8) Å, and the morpholine ring has a chair conformation. In the crystal, intermolecular N—H⋯O hydrogen bonds link the molecules into infinite chains in [001].

3-Phenyl-2-(pyrrolidin-1-yl)-5,6-dihydro-8H-thio-pyrano[4',3':4,5]thieno[2,3-d]pyrimidin-4(3H)-one.

In the title compound, C(19)H(19)N(3)OS(2), the thio-pyran ring adopts a twist-chair conformation and the pyrimidinone unit is essentially planar, with a mean deviation of 0.0497 Å. The thio-phene ring is essentially planar with a maximum deviation of 0.024 (2) Å, while the pyrrolidine ring exhibits an envelope conformation. The pyrimidinone and thio-phene rings are almost coplanar, forming a dihedral angle of 6.31 (15)°, while the dihedral angle between the mean planes of the phenyl ring and the pyrimidinone ring is 68.13 (10)°. In the crystal structure, adjacent mol-ecules are linked by C-H⋯O hydrogen bonds, forming a two-dimensional network in the ac plane.

Spectrophotometric determination of lead in traditional Chinese medicines with dibromop-methyl-acethylsulfonazo

A new highly sensitive and selective chromogenic reagent dibromo-p-methyl-acethylsulfonazo (DBMASA) has been synthesized and purified. A method has been proposed for the spectrophotometric determination of lead with DBMASA in traditional Chinese medicines. The content of lead in the samples was low, so we used sulfhydryl cotton fiber (SCF) to separate and enrich trace Pb(II), which lead to a satisfactory result. In 0.25 M phosphoric acid medium, which greatly increased the selectivity, lead reacted with DBMASA to form a 1: 2 blue complex, having an intense absorption peak at 640 nm. Under the optimal conditions, Beer’s law is obeyed over the range 0.01–1.0 µg/mL of Pb(II) and the apparent molar absorptivity is 1.06 × 105 L/mol cm. The detection limit and variation coefficient are found to be 2.1 ng/mL and 1.3%, respectively. The method has been applied to the determination of lead in traditional Chinese medicines with satisfactory results.