Heavy 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.

A Review of Heavy-Atom-Induced Room-Temperature Phosphorescence: a Straightforward Phosphorimetric Method

This review discusses the development of heavy-atom-induced, room-temperature phosphorescence (HAI-RTP), a new technique based on the use of RTP emitted directly from the analyte in a fluid solution with no protective medium except the presence of high concentrations of a heavy-atom perturber. These experimental conditions permit sufficient interaction between the perturber and the analytes to produce an effective population of their triplet states and thus emit intense phosphorescence.

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.

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.

Study of the substituent groups effect on the room-temperature phosphorescent emission of fluorene derivatives in solution

We present here the first study of the effect of substituent groups and the chemical structure of fluorene derivatives on phosphorescent emission. A group of fluorene derivatives have been studied with a new methodology of room-temperature phosphorescence emission called heavy atom induced room-temperature phosphorescence (HAI-RTP). This methodology makes use of RTP emission directly from the compound in fluid solution, without a protective medium but only with the presence of high concentrations of heavy atom perturbers and an oxygen scavenger. These experimental conditions permit sufficient interaction between the perturbers and the phosphors to produce effective population of the triplet states of the latter and, consequently, intense phosphorescent emission. Good deoxygenation conditions are obtained using sodium sulfite as the oxygen scavenger. We show here that it is possible that many fluorene derivatives can exhibit RTP emission in aqueous solutions in the absence of a protective medium. Phosphorescence spectral characteristics of these compounds (excitation and emission wavelengths and lifetime) and the optimization of the chemical variables involved in the phosphorescence phenomenon are reported. Under optimal experimental conditions, calibration graphs and detection and quantification limits in the ng ml −1 level have been established.

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.

Determination of the amino acid tryptophan and the biogenic amine tryptamine in foods by the heavy atom induced-room temperature phosphorescence methodology.

Very simple and selective methods are presented to determine the amino acid tryptophan (Trp) and the biogenic amine tryptamine (Tryp), both compounds with an indole-type molecular structure by the methodology named Heavy Atom Induced-Room Temperature Phosphorescence (HAI-RTP) which constitutes the first time that HAI-RTP has been used to detect compounds with non-naphthalenic structures in their molecules. Different variables affecting the phosphorescence signal (heavy atom perturber and sodium sulfite concentration) were carefully studied. The analytical curves give a linear dynamic range of 15-100 ng ml(-1) and a detection limit of 4 ng ml(-1) for Trp and 94-400 ng ml(-1) and 28 ng ml(-1) for Tryp. The methods have been successfully applied to the analysis of complex food matrices such as the presence of tryptophan in yoghurt and tryptamine in bottled beer. A single alkaline hydrolysis to release Trp from yoghurt proteins and two methods for extracting Tryp from beer samples are proposed and optimised. A total Trp content of 374 mg of Trp per kg of yoghurt was quantified by the standard addition method of calibration and a recovery of 90% was obtained for 250 ng ml(-1) of Tryp in spiked non-alcoholic beer samples.

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.

HAI−RTP Determination of Carbaryl Pesticide in Different Irrigation Water Samples of South Spain

In this work, a widely used pesticide named carbaryl, present in numerous water supplies, has been determined by the so-called heavy atom induced room-temperature phosphorescence (HAI-RTP) methodology. A detailed study of numerous instrumental variables such as sensitivity, slits, decay time, and gate time, and those of experimental type such as heavy atoms, oxygen scavenger, temperature, buffer solutions, and organic solvents, have been carried out. The detection limit was 2.8 ng mL(-)(1) with a relative standard deviation of 2.12% at the 150 ng mL(-)(1) level. Spiked irrigation water samples taken from different places near agricultural fields gave mean percentage recoveries of 95.7%. The results obtained in this study indicate that the proposed method is suitable for the determination of residues of carbaryl pesticide in water samples with good reproducibility and sensitivity for the analysis of this compound being rapid and very simple for routine analysis.

Heavy-atom induced room-temperature phosphorescence: a straightforward methodology for the determination of organic compounds in solution

We present here the first confirmation that the new methodology of room-temperature phosphorescence emission named heavy-atom induced room-temperature phosphorescence (HAI-RTP), can be observed for both polycyclic aromatic hydrocarbons and nitrogen heterocycles. This methodology makes use of RTP emission directly from the analyte in fluid solution, without a protective medium but only with the presence of high concentrations of heavy atom perturbers. This permits a sufficient interaction between the perturbers and the analytes to produce effective population of their triplet states, and consequently, an intense phosphorescent emission. Good deoxygenation conditions are obtained using sodium sulfite as the oxygen scavenger. In order to confirm this new phosphorescence methodology, a wide variety of compounds, with different chemical structure, have been selected. In this work, polycyclic aromatic hydrocarbons as naphthalene derivatives (naphthylacetic acid, α-naphthalene acetamide, naproxen, nafronyl, dansylamide and carbaryl) and fluorene and several nitrogen heterocyclic compounds as benzimidazole derivatives (thiabendazole), carbazole, indole derivatives (tryptamine, tryptophan and indole-3-butyric acid) and an acridine derivative (9-hydroxy-4-methoxyacridine), have been studied. Phosphorescence spectral characteristics of these compounds (excitation and emission wavelengths and lifetime) and the optimization of the chemical variables involved in the phosphorescence phenomenon in solution, are reported. Under optimal experimental conditions, calibration graphs and detection limit in the ng ml −1 level, have been established.

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)