Solid-surface Room-temperature Phosphorimetry Research Articles

Sequential determination of norfloxaxin and levofloxacin in the presence of other fluorquinolones using synchronous scanning room-temperature phosphorimetry and Th (IV) as the selective signal inducer

The selective determination of norfloxacin in mixtures with other fluorquinolones was achieved by synchronous scanning solid surface room-temperature phosphorimetry (SSRTP) and Th(NO 3) 4 as selective phosphorescence inducer. The method also allowed the determination of levofloxacin in a sequential way. The optimization of experimental conditions was made through an univariate approach, in order to find the best conditions for norfloxacin phosphorescence, followed by a 2 3 factorial design in order to verify interaction among relevant variables, to check robustness for each variable and to perform final adjustment of parameters. Absolute limit of detection (ALOD) for norfloxacin was 12 ng with a linear signal response extending up to 400 ng. Under the same experimental conditions set for norfloxacin, the ALOD for levofloxacin was 13 ng with linear signal response up to 450 ng. Accuracy of the method, using Th (IV) as selective phosphorescence inducer, was evaluated through the analysis of commercial and simulated pharmaceutical formulations with recoveries between 94.4 and 101% for norfloxacin and 95.9 and 103.8% for levofloxacin. The use of Cd (II), a traditional phosphorescence inducer for fluorquinolones, did not allow selective determination of norfloxacin. Further studies indicated the potential application of the method in urine samples.

Uncertainties associated with signal measurements from solutions and from solid substrates using luminescence based methods

A careful study was performed to evaluate and compare uncertainties associated with the measurement of luminescence from chrysene by using fluorimetry in solution and by using solid surface room-temperature phosphorimetry (SSRTP). Chrysene was chosen as the luminescent analyte (measurand) for this study because it is a substance of environmental interest and also because it presents strong natural fluorescence and phosphorescence that is easily induced by the external heavy atom effect. The most common approach for uncertainty calculation is the one indicated in the Guide to the Expression of Uncertainty in Measurement which is recognized worldwide. The most relevant sources of uncertainty were identified. The expanded uncertainty (k = 2; 95%) for SSRTP was 3.27 × 10−6 mol L−1 (3.7 ng of chrysene) with relevant contributions from the internal reproducibility, preparation of solutions and from the analytical curve. This value is equivalent to 28% of the reference analyte value. For fluorimetry, an acceptable value for the expanded uncertainty was achieved by preparing solutions by weighing masses of analyte and solvent. In this case, the huge contribution from the preparation of solutions by adjusting volume is minimized and the uncertainty magnitude was 2.12 × 10−9 mol L−1 (21.2% of the chrysene reference concentration). In this case, relevant contributions were from the repeatability, the internal reproducibility and from the analytical curve. The preparation of solutions by weighing does not have a relevant impact in improving the quality of the signal measurements by SSRTP.

Selective Determination of Harmol by Room-Temperature Phosphorimetry: A Comparative Performance with Micellar Electrokinetic Capillary Chromatography

Selective determination of harmol in the presence of other β-carboline alkaloids without the need for previous separation of components was achieved by Solid Surface Room-Temperature Phosphorimetry (SSRTP) using HgCl2. Detection of harmol at concentrations as low as 5.2 × 10−7 mol L−1 can be made in urine samples. Recovery of 100±12% was achieved. The analytical performance of SSRTP was compared to Micellar Electrokinetic Capillary Chromatography (MECC).

Heavy atom enhanced room-temperature phosphorimetry for ultratrace determination of harmane

Harmane has been proposed for the treatment of epilepsy, AIDS and leshmaniosis. Its room-temperature phosphorescence was induced using either AgNO 3 or TlNO 3 , enabling absolute limits of detection of 0.12 and 2.4 ng respectively, with linear dynamic ranges extending up to 456 ng (AgNO 3 ) and 911 ng (TlNO 3 ). Relative standard deviations around 3% were observed for substrates containing 46 ng of harmane. Such sensitivity and precision are needed because harmane intake must be strictly controlled to achieve proper therapeutic response. Interference studies were performed using thalidomide, reserpine and yohimbine. Recovery of 104±6% was achieved using solid surface room-temperature phosphorimetry. The result was comparable to the one obtained by micellar electrokinetic chromatography.

Phosphorimetric Detection of Polycyclic Aromatic Hydrocarbons on Solid-Phase Extraction Membranes

Solid-surface room-temperature phosphorimetry (SS-RTP) has been employed for the determination of polycyclic aromatic hydrocarbons (PAHs) adsorbed on solid-phase extraction (SPE) membranes. Three types of membranes commercially available were tested as solid substrates for phosphorescence emission. The effects of humidity and oxygen quenching were studied on SPEC® membranes. Calibration curves with linear dynamic ranges varying from two to three orders of magnitude were obtained in the presence of 0.05 M sodium dodecyl sulfate and 0.1 M TlNO3. The relative standard deviations of measurements varied between 5 and 10%. The absolute limits of detection were estimated at the ng to sub-ng level. On the basis of the performance of SPE membranes as solid substrates, the potential application of SPE-RTP for the analysis of PAHs is discussed.

Kalman filtering-aided time-resolved solid-surface room temperature phosphorimetry for simultaneous determination of anthracyclines in solution.

Daunorubicin, doxorubicin and epirubicin react with EuIII to form complexes which exhibit analytically useful room temperature phosphorescence (RTP). The RTP features of the three complexes are similar and the RTP spectra completely overlap. However, their three phosphorescence decay rates are different, and these differences were utilized to analyse the time-resolved RTP data by Kalman filtering. Simultaneous quantification of all three complexes is demonstrated and a method is proposed for the simultaneous determination of the three anthracyclines in mixtures by RTP optosensing. The analytical errors observed are within +/- 5%.

Phosphorescence imaging system using an acousto-optic filter-based charge coupled device

We are reporting for the first time the development of an imaging spectrometer for solid surface room temperature phosphorimetry based on an acousto-optic tunable filter. A HeCd laser was employed as the excitation source, and a cooled two-dimensional charge coupled device was used as the detector. The spectral characterization and imaging capability of the new system were evaluated with two well known phosphorescent compounds. The phosphorescence emissions of pyrene and 1,2,3,4-dibenzanthracene adsorbed on chromatography paper treated for background reduction were investigated. Thallium(I) acetate was employed as a phosphorescence enhancer. Based on the performance of the proposed instrument, several potential applications are discussed.

Phosphorescence imaging system using an acousto-optic tunable filter and a charge-coupled device

We are reporting for the first time the development of an imaging spectrometer for solid-surface room temperature phosphorimetry based on an acousto-optic tunable filter. A HeCd laser was employed as the excitation source, and a cooled two-dimensional charge-coupled device was used as the detector. The spectral characterization and imaging capability of the new system were evaluated with two well known phosphorescent compounds. Thee phosphorescence emissions of pyrene and 1,2,3,4-dibenzanthracene adsorbed on chromatography paper treated for background reduction were investigated. Thallium(I) acetate was employed as a phosphorescence enhancer. Based on the performance of the proposed instrument, several potential applications are discussed.

Phosphorimetric determination of indomethacin in pharmaceutical formulations.

A simple, rapid and sensitive method for the determination of indomethacin was developed based on solid-surface room-temperature phosphorimetry. Phosphorescence emission was induced by the indomethacin hydrolysis reaction in a basic medium. Chromatography paper treated for background reduction was employed as a solid substrate. The use of four heavy-atom salts and sodium dodecyl sulfate was optimized to estimate an absolute limit of detection at the subnanogram level. A calibration curve with a linear dynamic range extending over two orders of magnitude (3.0 x 10(-7)-1.0 x 10(-4) mol dm-3) was obtained. The recovery of the method (98.4 +/- 6.8%) was tested using commercial formulations containing indomethacin as the only anti-inflammatory agent.

Development of a Room-Temperature Phosphorescence Fiber-Optic Sensor

The design of a new fiber-optic sensor based on solid-surface room-temperature phosphorimetry is presented for the analyses of polycyclic aromatic hydrocarbons in water samples. Analytical figures of merit are given for several compounds of environmental importance. Limits of detection at the nanograms per milliliter level were estimated for pyrene, benzo[e]pyrene, benzo[ghi]perylene, 1,2:3,4-dibenzanthracene, coronene, and 2,3-benzofluorene. The linearity of response of the phosphorescence sensor was evaluated, showing a fairly linear behavior for quantitative analysis. Finally, the feasibility of monitoring polycyclic aromatic hydrocarbons in aqueous media was illustrated by identifying pyrene in a contaminated groundwater sample.

Laser-Induced Solid-Surface Room-Temperature Phosphorimetry of Polycyclic Aromatic Hydrocarbons

Laser-induced solid-surface room-temperature phosphorimetry (SSRTP) has been employed for the detection of polycyclic aromatic hydrocarbons. A nitrogen-pumped laser and a dye laser were used as excitation sources. The effects of sample volume, laser irradiation, and background reduction treatment on the precision and sensitivity of the method were studied. With the use of thallium(I) acetate as a phosphorescence enhancer, picogram limits of detection were estimated for phenanthrene, pyrene, benzo[ g,h,i]perylene, chrysene, coronene, and 1,2-benzofluorene. The study demonstrates that laser excitation can improve the sensitivity of SSRTP by up to three orders of magnitude.

Analysis of Polycyclic Aromatic Compounds in Soil Samples Using Laser-Induced Phosphorimetry

Abstract The analysis and spectral characteristics of several polycyclic aromatic hydrocarbons (PAHs) have been investigated by Laser-Induced Solid-Surface Room Temperature Phosphorimetry (LI-SSRTP). These PAHs included phenanthrene, chrysene, 1,2 benzofluorene, 2,3 benzofluorene, pyrene, coronene, 1,2,3,4 dibenzanthracene, benzo(a)pyrene, benzo(e)pyrene, and benzo(g, h, i)perylene. A nitrogen laser was employed as the excitation source at 337 nm. Filter paper treated with UV irradiation for background reduction was used as the solid substrate. Thallium(I)acetate was employed as a phosphorescence enhancer. Absolute limits of detection in the picogram level were obtained for all the PAHs, improving SSRTP levels of detection by three orders of magnitude. Finally, the proposed method was tested with a PAH contaminated soil sample. Detection of several PAHs at the nanogram level was easily performed, showing the potential of LI-SSRTP to the analysis of samples of environmental concern.

Solid-surface room-temperature phosphorescence detection of serotonin, tryptamine, and gramine enhanced by inorganic salts and sodium dodecyl sulfate

Room-temperature phosphorescence characteristics of serotonin (5-hydroxytryptamine), typtamine, and gramine ([3-(dimethylaminomethyl)indole]) were studied on low-background paper substrates. Several experimental parameters were optimized for maximum signal intensity. Sodium iodide, thallium(I) nitrate, silver(I) nitrate, and lead(II) nitrate were tested as phosphorescence enhancers. The effect of sodium dodecyl sulfate on the enhancement efficiency of these inorganic salts was also studied. The pH values of the solutions were adjusted to optimize the interaction between analyte molecules and solid substrates. Under the experimental conditions for maximum phosphorescence intensity, working curves ranging from two (gramine) to four (typtamine) orders of magnitude were obtained. Limits of detection at the nanogram level were estimated for the three compounds, showing the potential of solid-surface room-temperature phosphorimetry as a detection technique for biogenic amines.

Solid surface room temperature phosphorimetry analysis of yohimbine hydrochloride in pharmaceutical formulations

A new method of analysis for yohimbine hydrochloride pharmaceutical formulations is reported. The phosphorescence characteristics of yohimbine hydrochloride were studied at room temperature employing low background paper substrate. The use of phosphorescence enhancers such as sodium iodide, thallium(I) nitrate, and sodium dodecyl sulfate were optimized to obtain limits of detection at the nanogram level. The interference effects of active ingredients commonly encountered in yohimbine hydrochloride formulations were also evaluated. These included methyl testosterone, strychnine hydrochloride, and tocopherol acetate. The recovery of the method was tested in commercial formulations containing yohimbine hydrochloride and tocopherol acetate. The analyses were performed by both the calibration curve and the standard addition procedure. The recoveries obtained varied from 93.61 ± 3.15% to 101.53 ± 11%. The simplicity, the sensitivity, and the selectivity of the method, associated to the satisfactory recoveries obtained, show the potential of solid surface room temperature phosphorimetry for the analysis of yohimbine hydrochloride formulations.

Solid surface room temperature phosphorimetry analysis of reserpine in pharmaceutical formulations

A simple, rapid and sensitive method for reserpine analysis has been developed based on solid surface room temperature phosphorimetry. Phosphorescence emission was induced by the reserpine hydrolysis reaction in basic medium. Chromatography paper previously treated for background reduction was employed as a solid substrate. Four heavy atom salts and sodium dodecyl sulfate were tested for maximum signal intensity. A calibration curve with a linear dynamic range of three orders of magnitude (10 −7-10 −4 M) was obtained. A 1.9 ng limit of detection was estimated and recoveries of 98.7 and 100.3% were obtained in two dosage forms with different pharmaceutical matrices.

Pharmaceutical formulation analysis of thalidomide by solid surface room temperature phosphorimetry

A rapid and simple method of analysis for thalidomide formulations has been reported based on solid surface room temperature phosphorimetry. Thalidomide phosphorescence was enhanced by Hg(II) ions deposited on paper substrates previously treated for background reduction. A calibration curve with a linear dynamic range of three orders of magnitude was obtained (1.37 × 10−6 M − 10−3 M) and a 1.8 ng absolute limit of detection was estimated. The recovery of the method was tested in pharmaceutical formulations containing thalidomide as the only active ingredient. The values obtained were 96.3 ± 6.6% (employing the calibration curve procedure) and 98.0 ± 5.3% (employing the standard addition procedure), which show the potential of the technique for the analysis of thalidomide in dosage forms.

Kalman filtering-aided time-resolved solid-surface room temperature phosphorimetry for simultaneous determination of tetracyclines in solution

Tetracycline, chlortetracycline and oxytetracycline react with Eu (III) to form complexes which exhibit analytically useful room temperature phosphorescence (RTP). The RTP features of the three complexes are similar and the RTP spectra completely overlap. However, their three phosphorescence decay rates are quite different. These differences are utilized here to analyze the time-resolved RTP data by Kalman filtering. Simultaneous quantification of all the three complexes is demonstrated and a method is proposed for the simultaneous determination of the three tetracyclines in mixtures by RTP optosensing. Analytical errors observed are within ± 5%.

Solid-surface room-temperature phosphorimetric detection of caffeine, theophylline and theobromine in liquid chromatography

Solid-surface room-temperature phosphorimetry (SSRTP) is proposed as an alternative detection technique for the liquid chromatographic determination of caffeine, theophylline and theobromine. The measurements are performed in a continuous mode with a two-nebulizer automated system for SSRTP detection. The analytical figures of merit obtained with the proposed detector are compared with those obtained by UV absorption detection. The SSRTP and UV chromatograms of spiked urine samples are compared, and the possibility of keeping the SSRTP substrates as permanent records of analyzed samples is discussed.

Utilization of inorganic phosphor as a reference signal in solid-surface room-temperature phosphorimetry

Utilization of inorganic phosphor as a reference signal in solid-surface room-temperature phosphorimetry