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Fabrication of a material based on the Schiff base reaction to achieve covalent attachment of NH2-MIL-53(Al) and 3-formylsalicylic acid ligand (3-FSA) for fluorimetric detection of Zn2+ ions based on inhibition...

This work describes the application of time resolved fluorescence in microtiterplates and electrochemical methods on glassy carbon electrode for investigating the interactions of europium-3-carboxycoumarin with pesticides aldicarb, methomyl and prometryne. Stern-volmer studies at different temperatures indicate that static quenching dominates for methomyl, aldicarb and prometryne. By using Lineweaver-Burk equation binding constants were determined at 303 K, 308 K and 313 K. A thermodynamic analysis showed that the reaction is spontaneous with ΔG being negative. The enthalpy ΔH and the entropy ΔS of reactions were all determined. A time-resolved (gated) luminescence-based method for determination of pesticides in microtiterplate format using the long-lived europium-3-carboxycoumarin has been developed. The limit of detection is 4.80, 5.06 and 8.01 μmol L(-1) for methomyl, prometryne and aldicarb, respectively. This is the lowest limit of detection achieved so far for luminescent lanthanide-based probes for pesticides. The interaction of the probe with the pesticides has been investigated using cyclic voltammetry (CV), differential pulse polarography (DPP), square wave voltammetry (SWV) and linear sweep voltammetry (LSV) on a glassy carbon electrode in I = 0.1 mol L(-1) p-toluenesulfonate at 25 °C. The diffusion coefficients of the reduced species are calculated. The main properties of the electrode reaction occurring in a finite diffusion space are the quasireversible maximum and the splitting of the net SWV peak for Eu(III) ions in the ternary complex formed . It was observed that the increase of the cathodic peak currents using LSV is linear with the increase of pesticides concentration in the range 5 × 10(-7) to 1 × 10(-5) mol L(-1). The detection limit (DL) were about 1.01, 2.23 and 1.89 μmol L(-1) for aldicarb, methomyl and prometryne, respectively. In order to assess the analytical applicability of the method, the influence of various potentially interfering species was examined. Influence of interfering species on the recovery of 10 μmol L(-1) pesticides has been investigated.

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The formation of monomeric and dimeric binary and ternary complexes of Eu(III), Gd(III), Dy(III), and Pr(III) with primary ligand 2-amino-6-oxy 8-azapurine (8-azaguanine) and amino acids amino-succinic acid (aspartic acid), 2-amino-propanoic acid (D-alanine), (L-alanine), 2-amino-4-methyl thiobutanoic acid (methionine), 2-amino succinamic acid (asparagine), 2-amino 4-methyl pentanoic acid (DL-leucine), 2-amino-3-indolyl propanoic acid (L-tryptophan), 2-amino 3-(4-hydroxyphenyl)-propanoic acid (L-tyrosine), 2-amino-3-imidazole propanoic acid (histidine), 2-amino-5-guanidino pentanoic acid (arginine), and 4-amino-5oxo-pentanoic acid amide (glutamine); or nucleotides adenosine 5 0 -triphosphate (5 0 -ATP), adenosine 5 0 -diphosphate (5 0 -ADP), adenosine 5 0 -monophosphate (5 0 -AMP), adenosine 5 0 -monophosphate (5 0 -GMP), inosine 5 0 -monophosphate (5 0 -IMP), or nucleobases (uracil, 5-aminouracil, dihydrouracil); and with zwitterionic buffers (primary ligands) 4-(2-hydroxyethyl) piperazine-1-propane sulfonic acid (EPPS), 3-(N-morpholino)-2-hydroxypropane sulfonic acid (MOPSO), 3-(cycloxylamino)-1-propane sulfonic acid (CAPS), N-(tris(hydroxy methyl)-methyl)-2-amino-ethane sulfonic acid (TES), 3-(cyclohexyl amino)-2-hydroxy-1propane sulfonic acid (CAPSO), N-(tris(hydroxy methyl)-methyl)-3-amino propane sulfonic acid (TAPS), N-(2-acetamido)-2aminoethane sulfonic acid (ACES), 2-morpholinoethane sulfonic acid (MES), piperazine 1,4-bis(2-ethane sulfonic acid) (PIPES), N-(1,1-dimethyl-2-hydroxy ethyl)-3-amino 2-hydroxypropane sulfonic acid (AMPSO), N-(2-acetamido)-imino-diacetic acid (ADA); and nucleobases 6-amino-purine (adenine), 2-amino-6-oxypurine (guanine), 2-amino-6-oxy 8-azapurine (8-azaguanine), 5-methyl pyrimidine (thymine), 2,4-dioxypyrimidine (uracil), 5-amino 2,4-dioxypyrimidine (5-aminouracil), and 5,6-dihydro-2,4dioxypyrimidine (dihydrouracil), has been studied potentiometrically at (25.0 ( 0.1) °C and ionic strength I = 0.1 mol 3 dm À3 (KNO 3 ). The acidÀbase properties of ligands were investigated and discussed. The formation of the 1:1 and 2:1 binary and 1:1:1 and 2:1:1 ternary complexes are inferred from the corresponding titration curves. The stability constants of the binary and ternary systems were evaluated. Initial estimates of the formation constants of the resulting species and the protonation constants of the different ligands used have been refined with SUPERQUAD computer program.