ABSTRACT
We describe a terbium-ligand complex (TbL) for a microtiterplate assay for phosphate (P) in the 0.3-100 micromol L(-1) range based on luminescence quenching. As the pH optimum is at neutral pH (7.4) the probe is quenched by both, primary (H(2)PO(4)(-)) and secondary phosphate (HPO(4)(2-)). The LOD is 110 nmol L(-1). A Stern-Volmer study revealed that quenching is mostly static. Due to the ms-decay time of TbL, the first luminescence lifetime assay for phosphate could also be developed. The lifetime-based calibration plot is linear between 0.5 and 5 micromol L(-1) of P. The effect of various surfactants on assay performance and a study on interferents are presented. The probe was successfully applied to determination of P in commercial plant fertilizers and validated against the molybdenum blue test. The probe is the most sensitive lanthanide-based probe for phosphate.
Subject(s)
Coordination Complexes/chemistry , Luminescent Measurements/methods , Phosphates/analysis , Terbium/chemistry , Fertilizers/analysis , Hydrogen-Ion Concentration , Kinetics , Surface-Active Agents/chemistry , Time FactorsABSTRACT
We present a time-resolved (gated) luminescence-based method for determination of Cu2+ ions in microtiterplate format in the nanomolar concentration range using the novel long-lived terbium-[1-methyl-4-hydroxy-3-(N-2-ethyl-5-aminothiadiazolyl-)-carbamoyl-quinoline-2-one] (TbL) complex. The probe works best in Tb:L = 1:2 stoichiometry at neutral pH. The dynamic range is from 10 to 300 nmol L(-1) of Cu2+ and the limit of detection is 4.3 nmol L(-1). This is the lowest limit of detection achieved so far for luminescent lanthanide-based probes for copper. It is shown that gating can efficiently suppress intense, short decaying background fluorescence e.g. that of Rhodamine 6G. The assay can be performed by measurement of luminescence decay time, as well. Stern-Volmer studies indicate that static quenching dominates over dynamic quenching. TbL2 was tested for the effect of some relevant interferents and the assay was applied to the determination of copper in tap water samples. The results achieved were in good agreement with those of a reference method.
Subject(s)
Copper/analysis , Fresh Water/analysis , Luminescent Measurements/methods , Organometallic Compounds/chemical synthesis , Hydrogen-Ion Concentration , Organometallic Compounds/chemistry , Rhodamines/chemistry , Time FactorsABSTRACT
New europium complexes of 3-oxo-1-hydroxy-quinoline-2-carboxylic acid amide derivatives (L1-L3), which are highly luminescent and do not require luminescence enhancers are reported. The luminescence intensity of the Eu-L1-3 complexes was enhanced by the addition of citrate ions in water solution. A sensitive luminescence enhancement system was developed for the determination of citrate ions on the base of Eu-9-fluoro-1-hydroxy-5-methyl-3-oxo-6,7-dihydro-3H,5H-pyrido[3,2,1-ij]quinoline-2-carboxylic acid (2-piperazin-1-yl-ethyl)-amide (L1) complex. This effect was applied to the determination of the drug, which is not a lanthanide luminescence sensitizer. The Eu-L1- Cit complex with a components' ratio 1:1:2 was proposed to be used as the analytical form for the luminescence determination of drug - mosapride citrate. The calibration curve is linear in the range of 1.0-25.0 microg/mL of mosapride citrate (LOD is 0.35 microg/mL). This method was applied for the determination of mosapride citrate in dosage form - tablets "Mosid MT" - 2.5 mg.
Subject(s)
Benzamides/analysis , Morpholines/analysis , Calibration , Hydrogen-Ion Concentration , Luminescent Measurements , Tablets/chemistryABSTRACT
The interaction of the terbium-difloxacin complex (Tb-DFX) with DNA has been examined by using UV-vis absorption and luminescence spectroscopy. The Tb-DFX complex shows an up to 85-fold enhancement of luminescence intensity upon titration with DNA. The long decay times allow additional detection schemes like time-resolved measurements in microplate readers to enhance sensitivity by off-gating short-lived background luminescence. Optimal conditions are found at equimolar concentrations of Tb(3+) and DFX (0.1 or 1 microM) at pH 7.4. Under these conditions, the luminescence intensity is linearly dependent on the concentration of ds-DNAs and ss-DNA between 1-1500 ng mL(-1) and 4.5-270 ng mL(-1), respectively. The detection limit is 0.5 ng mL(-1) for ds-DNAs and 2 ng mL(-1) for ss-DNA. The mechanism for the luminescence enhancement was also studied.
