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1.
Talanta ; 149: 53-61, 2016 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-26717813

RESUMEN

The present study reports a fast and accurate methodology for laser-induced breakdown spectroscopic, LIBS, analysis of aqueous samples for environmental monitoring purposes. This methodology has two important attributes: one is the use of a 300nm oxide coated silicon wafer substrate (Si+SiO2) for the first time for manual injection of 0.5 microliter aqueous metal solutions, and two is the use of high energy laser pulses focused outside the minimum focus position of a plano convex lens at which relatively large laser beam spot covers the entire droplet area for plasma formation. Optimization of instrumental LIBS parameters like detector delay time, gate width and laser energy has been performed to maximize atomic emission signal of target analytes; Cu, Mn, Cd and Pb. Under the optimal conditions, calibration curves were constructed and enhancements in the LIBS emission signal were obtained compared to the results of similar studies given in the literature. The analytical capability of the LIBS technique in liquid analysis has been improved. Absolute detection limits of 1.3pg Cu, 3.3pg Mn, 79pg Cd and 48pg Pb in 0.5 microliter volume of droplets were obtained from single shot analysis of five sequential droplets. The applicability of the proposed methodology to real water samples was tested on the Certified Reference Material, Trace Metals in Drinking Water, CRM-TMDW and on ICP multi-element standard samples. The accuracy of the method was found at a level of minimum 92% with relative standard deviations of at most 20%. Results suggest that 300nm oxide coated silicon wafer has an excellent potential to be used as a substrate for direct analysis of contaminants in water supplies by LIBS and further research, development and engineering will increase the performance and applicability of the methodology.

2.
Spectrochim Acta A Mol Biomol Spectrosc ; 141: 307-15, 2015 Apr 15.
Artículo en Inglés | MEDLINE | ID: mdl-25704130

RESUMEN

Crystal structure of the title compound, C26H21N3O5, has been synthesized and characterized by FT-IR, (1)H NMR, (13)C NMR and X-ray single crystal determination. The molecular geometry was also calculated by using Gaussian 03 software and structure was optimized by using HF and DFT/B3LYP method with the 6-31G(d) basis sets in ground state. The comparison of the theoretical and experimental geometries of the title compound indicated that the X-ray parameters agree with the theoretically obtained values. It was seen that R(2) value changes from 0.015 to 0.021 Å for bond length and angle. The calculated vibrational frequencies are also in good agreement with the experimental results. The (1)H and (13)C NMR chemical shifts values of (E)-2-(2-hydroxystyryl)-6-(4-methoxybenzoyl)-5-(4-methoxyphenyl)-1,2,4-triazin-3(2H)-one molecule have been calculated by the GIAO method. Besides, molecular electrostatic potential maps (MEP), Mulliken charges and Nonlinear Optical effects (NLO) analysis of the compound have been calculated by the HF and B3LYP/6-31G(d) methods.


Asunto(s)
Modelos Moleculares , Triazinas/química , Espectroscopía de Resonancia Magnética con Carbono-13 , Cristalografía por Rayos X , Electrones , Enlace de Hidrógeno , Conformación Molecular , Dinámicas no Lineales , Espectroscopía de Protones por Resonancia Magnética , Espectroscopía Infrarroja por Transformada de Fourier , Electricidad Estática , Termodinámica , Vibración
4.
Anal Chim Acta ; 770: 7-17, 2013 Apr 03.
Artículo en Inglés | MEDLINE | ID: mdl-23498681

RESUMEN

A laser induced breakdown spectrometry hyphenated with on-line continuous flow hydride generation sample introduction system, HG-LIBS, has been used for the determination of arsenic, antimony, lead and germanium in aqueous environments. Optimum chemical and instrumental parameters governing chemical hydride generation, laser plasma formation and detection were investigated for each element under argon and nitrogen atmosphere. Arsenic, antimony and germanium have presented strong enhancement in signal strength under argon atmosphere while lead has shown no sensitivity to ambient gas type. Detection limits of 1.1 mg L(-1), 1.0 mg L(-1), 1.3 mg L(-1) and 0.2 mg L(-1) were obtained for As, Sb, Pb and Ge, respectively. Up to 77 times enhancement in detection limit of Pb were obtained, compared to the result obtained from the direct analysis of liquids by LIBS. Applicability of the technique to real water samples was tested through spiking experiments and recoveries higher than 80% were obtained. Results demonstrate that, HG-LIBS approach is suitable for quantitative analysis of toxic elements and sufficiently fast for real time continuous monitoring in aqueous environments.


Asunto(s)
Antimonio/análisis , Arsénico/análisis , Germanio/análisis , Rayos Láser , Plomo/análisis , Espectrofotometría , Abastecimiento de Agua/análisis , Borohidruros/química , Gases , Límite de Detección
5.
Acta Crystallogr Sect E Struct Rep Online ; 68(Pt 12): o3430, 2012 Dec 01.
Artículo en Inglés | MEDLINE | ID: mdl-23476248

RESUMEN

In the title compound, C11H15ClN2O3S, the 3-chloro-2,2-dimethyl-propanamide and sulfonamide substituents are arranged on opposite sides of the benzene ring plane. In the crystal, mol-ecules are linked by N-H⋯O and C-H⋯O hydrogen bonds, forming a three-dimensional network.

6.
Acta Crystallogr Sect E Struct Rep Online ; 68(Pt 12): o3475-6, 2012 Dec 01.
Artículo en Inglés | MEDLINE | ID: mdl-23476284

RESUMEN

The mol-ecular conformation of the title compound, C11H15ClN2O3S, is stabilized by a C-H⋯O hydrogen bond, forming an S(6) ring motif. In the crystal, mol-ecules are linked by two pairs of inversion-related N-H⋯O hydrogen bonds, generating R2(2)(8) and R2(2)(20) ring motifs, resulting in chains running along [0-11]. These chains are connected by N-H⋯O hydrogen bonds along [100], forming layers parallel to (011). There are also C-H⋯π inter-actions between the layers, which consolidate the three-dimensional structure.

7.
Acta Crystallogr Sect E Struct Rep Online ; 68(Pt 12): o3481, 2012 Dec 01.
Artículo en Inglés | MEDLINE | ID: mdl-23476289

RESUMEN

In the title compound, C15H23N3O3S·H2O, the piperidine ring has a chair conformation. In the crystal, the sulfonamide mol-ecules are linked by N-H⋯O hydrogen bonds, forming a layer parallel to (10-1). The layers are inter-connected via N-H⋯Ow, Ow-H⋯N and Ow-H⋯O (w = water) hydrogen bonds, forming a three-dimensional network.

8.
Acta Crystallogr Sect E Struct Rep Online ; 66(Pt 3): m253-4, 2010 Feb 06.
Artículo en Inglés | MEDLINE | ID: mdl-21580208

RESUMEN

The title compound, [CoCl(2)(C(11)H(15)N(3)O(2)Si)(2)]·C(3)H(7)NO, was synthesized from 5-nitro-1-trimethyl-silylmethyl-1H-benzimid-azole and cobalt(II) chloride in dimethyl-formamide. The Co(II) atom is coordinated in a distorted tetra-hedral environment by two Cl atoms and two N atoms. In the crystal structure, there are a number of C-H⋯Cl and C-H⋯O hydrogen-bonding inter-actions between symmetry-related mol-ecules.

9.
Acta Crystallogr Sect E Struct Rep Online ; 66(Pt 7): o1559-60, 2010 Jun 05.
Artículo en Inglés | MEDLINE | ID: mdl-21587803

RESUMEN

In the title compound, C(9)H(11)ClN(2)O(3)S, the dihedral angle between the benzene ring and the amido -NHCO- plane is 15.0 (2)°. An intra-molecular C-H⋯O hydrogen bond generates an S(6) ring motif. In the crystal structure, the amino NH(2) group is involved in inter-molecular N-H⋯O hydrogen bonds, which connect the mol-ecules into a double layer structure expanding parallel to the bc plane. The layers are further linked by an amido N-H⋯O hydrogen bond. Between the layers, a weak π-π inter-action with a centroid-centroid distance of 3.7447 (12) Šis also observed.

10.
Acta Crystallogr Sect E Struct Rep Online ; 66(Pt 7): o1596, 2010 Jun 05.
Artículo en Inglés | MEDLINE | ID: mdl-21587833

RESUMEN

In the title compound, C(8)H(9)ClN(2)O(3)S, the benzene ring makes a dihedral angle of 4.1 (9)° with the amido -NHCO- plane including the major occupancy component of the carbonyl O atom [19 (4)° for the minor component]. An intra-molecular C-H⋯O inter-action occurs. The O atom of the carbonyl group is disordered over two positions with site-occupancy factors of 0.67 (11) and 0.33 (11). Inter-molecular N-H⋯O hydrogen bonds help to stabilize the crystal structure.

11.
Acta Crystallogr Sect E Struct Rep Online ; 65(Pt 3): o626-7, 2009 Feb 28.
Artículo en Inglés | MEDLINE | ID: mdl-21582278

RESUMEN

The stabilized conformation of the title compound, C(36)H(25)NO(3), 4-(9-anthryl)-1-(2-methoxyphenyl)-spiro[azetid-in-3,9'-xanthen]-2-one, may be compared with that of the isomeric compound 4-(9-anthr-yl)-1-(4-methoxy-phen-yl)spiro-[azetidin-3,9'-xanthen]-2-one. In the title isomer, the meth-oxy group is slightly twisted out of the plane of the attached benzene ring, with a C-O-C-C torsion angle of 31.5 (2)°. Its ß-lactam ring is essentially planar, with a maximum deviation of -0.021 (1) Å. The ß-lactam ring makes dihedral angles of 18.815 (9), 83.33 (7) and 53.62 (8)° with the mean planes of the benzene, xanthene and anthracene ring systems, respectively. The structure is stabilized by C-H⋯π, C-H⋯N and C-H⋯O inter-actions.

12.
Acta Crystallogr Sect E Struct Rep Online ; 64(Pt 10): o1919, 2008 Sep 13.
Artículo en Inglés | MEDLINE | ID: mdl-21201127

RESUMEN

In the title compound, C(24)H(28)N(2)O(3)S, the pendant methyl C atom bonded to the cyclo-hexane ring is disordered over two sites in a 0.580 (11):0.420 (11) ratio. The cyclo-hexane ring adopts a distorted chair conformation while the thia-zolidine ring has an envelope conformation. The two phenyl rings make a dihedral angle of 71.8 (2)° with each other. The conformation is stabilized by an intra-molecular N-H⋯O hydrogen bond. In the crystal structure, an inter-molecular hydrogen bond O-H⋯O occurs.

13.
Acta Crystallogr Sect E Struct Rep Online ; 64(Pt 10): o1939-40, 2008 Sep 13.
Artículo en Inglés | MEDLINE | ID: mdl-21201146

RESUMEN

Mol-ecules of the title spiro-[4.5]decane derivative, C(17)H(30)N(2)O(3)S, are linked by paired O-H⋯N hydrogen bonds into centrosymmetric R(2) (2)(16) dimers and these dimers are linked into a three-dimensional framework structure by C-H⋯O interactions.

14.
Acta Crystallogr Sect E Struct Rep Online ; 64(Pt 3): o621-2, 2008 Feb 22.
Artículo en Inglés | MEDLINE | ID: mdl-21201955

RESUMEN

The title compound, C(25)H(26)N(2)Te, was synthesized from bis-[1,3-bis-(3-phenyl-prop-yl)benzimidazolidin-2-yl-idene] and Te in a toluene solution. The molecule possesses a twofold rotation axis passing through the Te atom and the center of the benzimidazole ring system. The benzimidazole ring system makes an angle of 67.9 (4)° with the phenyl rings.

15.
Acta Crystallogr Sect E Struct Rep Online ; 64(Pt 5): m612-3, 2008 Apr 02.
Artículo en Inglés | MEDLINE | ID: mdl-21202170

RESUMEN

In the title complex, [Hg(2)I(4)(C(26)H(20)FOP)(2)], the Hg(II) centre is four-coordinate with one short Hg-I bond [2.6895 (7) Å], one Hg-C bond and two asymmetric bridging Hg-I bonds with distances of 2.7780 (8) and 3.2599 (8) Å. The title mol-ecule has a crystallographic inversion centre at the centroid of the four-membered ring formed by the two Hg atoms and two I atoms. The crystal packing is stabilized by C-H⋯O hydrogen bonds.

16.
Acta Crystallogr Sect E Struct Rep Online ; 64(Pt 5): o810-1, 2008 Apr 10.
Artículo en Inglés | MEDLINE | ID: mdl-21202301

RESUMEN

The title compound, C(21)H(22)N(4)O(2)S(2)·0.5H(2)O, crystallizes with two mol-ecules in the asymmetric unit. The dihedral angles between the phenyl and imidazothiazole ring systems are 19.16 (9) and 21.37 (9)°. In the imidazothiazole ring systems, the cyclohexane rings adopt chair conformations, while the thiazole rings have distorted envelope conformations. The two mol-ecules are stabilized by intra-molecular N-H⋯O, O-H⋯O and C-H⋯S inter-actions and the crystal structure is stabilized by inter-molecular N-H⋯O, O-H⋯O, C-H⋯O and C-H⋯N inter-actions.

17.
Acta Crystallogr Sect E Struct Rep Online ; 64(Pt 5): o923, 2008 Apr 26.
Artículo en Inglés | MEDLINE | ID: mdl-21202404

RESUMEN

In the title compound, C(22)H(21)NO(5)S, the 2-naphthol group and the thio-phene ring are almost coplanar, with a dihedral angle of 5.75 (7)°. The structure is stabilized by intra-molecular O-H⋯O, O-H⋯N and C-H⋯S, and inter-molecular C-H⋯O hydrogen-bonding inter-actions.

18.
Acta Crystallogr Sect E Struct Rep Online ; 64(Pt 8): o1572-3, 2008 Jul 23.
Artículo en Inglés | MEDLINE | ID: mdl-21203273

RESUMEN

In the title compound, C(15)H(26)N(2)O(2)S, the cyclo-hexane and morpholine rings adopt chair conformations, while the thia-zole ring has a twist conformation. An intra-molecular C-H⋯S hydrogen-bond inter-action forms a five-membered ring. The crystal packing involves C-H⋯O=C inter-molecular inter-actions where carbonyl O atoms act as double acceptors to two symmetrically related H atoms.

19.
Acta Crystallogr Sect E Struct Rep Online ; 64(Pt 8): o1574-5, 2008 Jul 23.
Artículo en Inglés | MEDLINE | ID: mdl-21203274

RESUMEN

The title compound, C(16)H(28)N(2)O(3)S, is dimerized by inversion symmetry-related inter-molecular O-H⋯N hydrogen bonding, forming an R(2) (2)(16) motif. The dimers are also linked through inter-molecular C-H⋯O hydrogen bonding. The compound is chiral with a stereogenic centre located in the thia-zole ring, but in the crystal structure it forms a racemate. The thia-zole ring has an envelope conformation, while the cyclo-hexane and morpholine rings adopt chair conformations.

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