Atom Induced Room Temperature Phosphorescence Research Articles

Stereoselective Binding of Flurbiprofen Enantiomers and their Methyl Esters to Human Serum Albumin Studied by Time‐Resolved Phosphorescence

The interaction of the nonsteroidal anti-inflammatory drug flurbiprofen (FBP) with human serum albumin (HSA) hardly influences the fluorescence of the protein's single tryptophan (Trp). Therefore, in addition to fluorescence, heavy atom-induced room-temperature phosphorescence is used to study the stereoselective binding of FBP enantiomers and their methyl esters to HSA. Maximal HSA phosphorescence intensities were obtained at a KI concentration of 0.2 M. The quenching of the Trp phosphorescence by FBP is mainly dynamic and based on Dexter energy transfer. The Stern-Volmer plots based on the phosphorescence lifetimes indicate that (R)-FBP causes a stronger Trp quenching than (S)-FBP. For the methyl esters of FBP, the opposite is observed: (S)-(FBPMe) quenches more than (R)-FBPMe. The Stern-Volmer plots of (R)-FBP and (R)-FBPMe are similar although their high-affinity binding sites are different. The methylation of (S)-FBP causes a large change in its effect on the HSA phosphorescence lifetime. Furthermore, the quenching constants of 3.0 × 10(7) M(-1) s(-1) of the R-enantiomers and 2.5 × 10(7) M(-1) s(-1) for the S-enantiomers are not influenced by the methylation and indicate a stereoselectivity in the accessibility of the HSA Trp to these drugs.

Simple and rapid determination of the active metabolite of nabumetone in biological fluids by heavy atom-induced room temperature phosphorescence

A simple, selective and sensitive heavy atom induced-room temperature phosphorimetric method is described for the determination of 6-methoxynaphthylacetic acid, main metabolite of nabumetone, in biological fluid. The phosphorescence signals are a consequence of intermolecular protection when analytes are, exclusively, in presence of heavy atom salt and sodium sulfite as an scavenger to minimize room temperature phosphorescence quenching. This technique enables us to determine analytes in complex matrices without the need for a tedious prior separation process. Optimized conditions for the determination were 0.12 M TlNO 3. An amount of 0.025 M sodium sulfite and pH 7.5 (adjusted with 0.1 M sodium hydrogen phosphate-dihydrogen phosphate buffer solution). The delay time, gate time and time between flashes were 180, 1500 μs, and 5 ms, respectively. The maximum phosphorescence signal appeared instantly and the intensity was measured at λ ex = 328.4 nm and λ em = 544.4 nm. The response obtained was linearly dependent on concentration in the range of 20–1000 ng mL −1. The detection limit, according to error propagation theory, was 11.6 ng mL −1 and the detection limit as proposed by Clayton, was 17.4 ng mL −1. The repeatability was studied by using 10 solutions of 100 and 800 ng mL −1 of metabolite; if the theory of error propagation is assumed the relative error is 4.3 and 0.66%. The S.D. of replicates was found to be 2.2 and 11.0 ng mL −1. This method was successfully applied to the analysis of 6-methoxynaphthylacetic acid in human serum and urine.

Flow-through optosensing of 1-naphthaleneacetic acid in water and apples by heavy atom induced–room temperature phosphorescence measurements

A sensitive and selective phosphorimetric method for the determination of 1-naphthaleneacetic acid (1-NAA) based on a flow-injection system connected to a flow cell packed with a solid support and placed in the sample compartment of a conventional luminescence spectrometer is described. A non-ionic solid polymeric resin Amberlite XAD-7 is used for the packing. After injection of the sample, 1-NAA is on-line retained in the packed resin and measurements of the heavy atom induced (HAI)–room temperature phosphorescence (RTP) emission ( λ ex/ λ em = 292/490 nm) from this native luminescent compound are taken. The optimum experimental conditions were investigated by injecting 2 ml samples of an aqueous solution of 1-NAA in the flow system. A concentration 0.15 mol l −1 of thallium(I) ions, as heavy atom, both in the samples and the carrier flow, was finally selected. Also, a concentration of 6 mmol l −1 of sulphite was optimal for ensuring the necessary deoxygenation of the system at the selected flow rate of 0.8 ml min −1. After measurement, the solid support was efficiently regenerated by injecting 1 ml of a mixture water:acetone in a ratio 1:1 (v/v) into the flow. The detection limit (3 σ criterion) was 1.2 ng ml −1 of 1-NAA. The repeatability (R.S.D.) for five replicates of a sample containing 50 ng ml −1 of analyte turned out to be ±3% and the calibration graphs proved to be linear up to 500 ng ml −1 of 1-NAA (maximum concentration assayed). The effect of potential interferences from other organic species which can be also used as plant growth regulators, as well as from various inorganic cations and anions, has been investigated as well. The method was successfully applied to the determination of low levels of this plant growth regulator in natural waters (river and fountain waters) and apples.

Heavy atom induced room temperature phosphorescence: a tool for the analytical characterization of polycyclic aromatic hydrocarbons

We have developed a heavy atom induced room temperature phosphorescence (HAI-RTP) procedure for the analytical characterization of 15 polycyclic aromatic hydrocarbons (PAHs). This methodology is based on the measurement of the native RTP emission from the analytes. RTP measurements are made directly in fluid aqueous solution, without the need of a protective medium but in the presence of high concentrations of heavy atom perturbers. Efficient deoxygenation conditions should be ensured using sodium sulfite as the oxygen scavenger. In such conditions, 15 PAHs, identified as major pollutants by the Environmental Protection Agency (EPA), naphthalene, acenaphthylene, acenaphthene, fluorene, phenanthrene, anthracene, fluoranthene, pyrene, chrysene, benzo(a)anthracence, benzo(k)fluoranthene, benzo(b)fluoranthene, benzo(a)pyrene, indeno(1,2,3-cd)pyrene, benzo(g,h,i)perylene and dibenzo(a,h)anthracence, have been studied and analytically characterized using the proposed HAI-RTP procedure. To our knowledge, this is the first time that an analytically useful RTP emission of some of the PAHs under study in aqueous media has been observed. Once optimized the chemical variables affecting the phosphorescence phenomenon in solution, the phosphorescence spectral characteristic of all of the selected toxic compounds (excitation and emission wavelengths and triplet lifetimes) were obtained. Under the optimal experimental conditions, calibration graphs and detection limits (in the ng ml −1 level) were established for the 15 PAHs under study. Potential applicability of the developed methodology will be discussed.

Heavy atom induced room temperature phosphorescence: a tool for the analytical characterization of polycyclic aromatic hydrocarbons

Heavy atom induced room temperature phosphorescence: a tool for the analytical characterization of polycyclic aromatic hydrocarbons

FACILE ANALYSIS OF CARBAZOLE IN COMMERCIAL ANTHRACENE BY HEAVY ATOM–INDUCED ROOM TEMPERATURE PHOSPHORESCENCE

The applicability of heavy atom–induced room temperature phosphorescence (HAI-RTP) in real samples is demonstrated in this work. In this methodology only two reagents, potassium iodide as heavy atom salt and sodium sulfite as oxygen scavenger, were used to obtain the phosphorescent signal of carbazole in solution while anthracene did not show phosphorescence under these experimental conditions. In this study a new simple, rapid, and selective phosphorimetric method is proposed, using HAI-RTP methodology for the determination of carbazole in high-purity anthracene. The phosphorescence intensity was measured at 438 nm with excitation at 290 nm. Phosphorescence was fully developed instantly. A linear concentration range between 0 and 250 ng/mL−1 with a detection limit of 1.05 ng/mL−1 (10.5 ng of CBZ in 600 ng of anthracene), an analytical sensitivity of 1.7 ng/mL−1, and standard deviation of 0.71% at 150 ng/mL−1 concentration level was obtained. The method has been successfully applied to the analysis of carbazole in spiked anthracene samples.

Sensitive and simple determination of the vasodilator agent dipyridamole in pharmaceutical preparations by phosphorimetry.

The applicability of heavy atom-induced room-temperature phosphorescence to pharmaceutical samples is demonstrated in this work. Thus a new, simple, rapid, and selective phosphorimetric method for dipyridamole determination is proposed. The phosphorescence signals are a consequence of intermolecular protection when analytes are exclusively in the presence of heavy atom salts and sodium sulfite as an oxygen scavenger to minimize RTP quenching. The determination was performed in 0.1 mol L(-1) thallium(I) nitrate and 8 mmol L(-1) sodium sulfite at a measurement temperature of 20 degrees C. The phosphorescence intensity was measured at 635 nm, with excitation at 305 nm. Phosphorescence was easily developed; a linear concentration range was obtained between 0 and 100 ng mL(-1) with a detection limit of 940 ng L(-1), an analytical sensitivity of 2.5 ng mL(-1), and a standard deviation of 2.7% at 60 ng mL(-1) concentration. The method has been successfully applied to the analysis of dipyridamole in a unique Spanish commercial formulation containing 100 ng mL(-1) per capsule. The recovery was 101.6% with 6.5% standard deviation of analytical measurement. The method using the standard addition methodology has been validated.

Simple determination of propranolol in pharmaceutical preparations by heavy atom induced room temperature phosphorescence

The applicability of heavy atom induced room temperature phosphorescence in real samples is demonstrated in this work. In this methodology only two reagents, potassium iodide as heavy atom salt and sodium sulphite as oxygen scavenger, were used to obtain phosphorescent signal of propranolol in solution. Thus a new simple, rapid and selective phosphorimetric method is proposed for propranolol determination in pharmaceutical preparations. The phosphorescence intensity was measured at 492 nm exciting at 294 nm. Phosphorescence was fully developed instantly, obtaining a linear concentration range between 0 and 500 ng ml −1 with a detection limit of 14.4 ng ml −1, an analytical sensitivity of 6.7 ng ml −1 and a standard deviation of 1.4% at a 300 ng ml −1 concentration level. The method has been successfully applied to the analysis of propranolol in an antidepressive pharmaceutical preparation and it was validated using standard addition methodology.

The use of modified simplex method to optimize the room temperature phosphorescence variables in the determination of an antihypertensive drug

In the present paper, the modified simplex method (MSM) has been applied, for the first time, to determine compounds by a luminescence technique. The method was based on the optimization of chemical and instrumental variables affecting phosphorescence using a geometric simplex in two and three dimensions of space, respectively. As application, we have determined a novel antihypertensive drug, naftopidil, in urine and serum, by heavy atom induced room temperature phosphorescence (HAI-RTP); this technique enables us to determine analytes in complex matrices, biological fluids, without the need for a tedious prior separation process. With the proposed method, the maximum signal of phosphorescence appears instantly once the sample has been prepared and the intensity was measured at λ ex=287 nm and λ em=525 nm. Overall least-squares regression was used to find the straight line that fitted the experimental data. The detection limit, as well as the repeatability and the standard deviation (S.D.) for replicate sample, were also determined.

Simple and rapid determination of the drug naproxen in pharmaceutical preparations by heavy atom-induced room temperature phosphorescence

A simple, selective and sensitive heavy atom-induced room temperature phosphorimetric method (HAI-RTP) is described for the determination of naproxen (NAP) in pharmaceutical preparations. The phosphorescence signals are a consequence of intermolecular protection when analytes are, exclusively, in presence of a heavy atom salt and sodium sulfite as an oxygen scavenger to minimize RTP quenching. These variables selection constitute the basis of a HAI-RTP method for the determination of naproxen (detection limit 17.6 ng ml −1; 1.71% relative standard deviation at 250 ng ml −1). The method has been applied satisfactorily to the analysis of pharmaceutical preparations.

A Simple and Rapid Phosphorimetric Method for the Determination of α-Naphthaleneacetamide in Fruit Samples

A simple and rapid phosphorimetric method for the determination of α-naphthaleneacetamide residues in fruit samples is presented. The method is based on a new, simple and sensitive methodology: Heavy Atom Induced Room Temperature Phosphorescence (HAI-RTP). The effect of different heavy atom salts and sodium sulfite concentration over the phosphorescence signals was investigated. The resultant HAI-RTP spectra were successfully applied for determining α-naphthaleneacetamide concentrations in the range of 7.8 to 100 μg·L−1, with relative standard deviations between 2.6 and 5.7%.

Determination of the Drug Naphazoline in Pharmaceutical Preparations by Heavy Atom-Induced Room-Temperature Phosphorescence

A simple, selective, and sensitive heavy atom-induced room-temperature phosphorimetric method (HAI-RTP) is described for the determination of naphazoline (NPZ) in pharmaceutical preparations. The phosphorescence signals are a consequence of intermolecular protection when analytes are, exclusively, in the presence of a heavy atom salt and sodium sulfite as an oxygen scavenger to minimize RTP quenching. This variable selection constitutes the basis of the HAI-RTP method for the determination of naphazoline (detection limit 43.5 ng/mL; 2.39% relative standard deviation at 500 ng/mL). The method has been applied to the analysis of pharmaceutical preparations.

Heavy Atom Induced Room Temperature Phosphorescence Method for the Determination of the Plant Growth Regulator β-Naphthoxyacetic Acid

A simple, selective, and sensitive heavy atom induced room temperature phosphorimetric method (HAI-RTP) is described for the determination of the plant growth regulator β-naphthoxyacetic acid (NOA) in spiked apple samples. A careful selection of the different variables (heavy atom and sodium sulfite) to obtain the phosphorescence signal constitutes the basis of a HAI-RTP method for the determination of NOA. The analytical curve of NOA gives a linear dynamic range of 0−625 ng mL-1 and a detection limit of 30.5 ng mL-1. A recovery of 108.8% was obtained for 500 ng mL-1 NOA in spiked apple samples. Keywords: β-Naphthoxyacetic acid; heavy atom induced room temperature phosphorescence (HAI-RTP)