Laser-induced Fluorimetry Research Articles

A novel approach for trace to percentage level determination of uranium in rocks, soils and stream sediments by laser induced fluorimetry (LIF)

A method for precise and accurate determination of ppm to percentage level uranium in rocks, soils and stream sediments by laser induced fluorimetry (LIF) has been developed. Iron, above a ratio (iron to uranium) of 100, which is always the case when uranium is present at ppm level, interferes seriously. A prior removal of iron enables the determination of uranium over a wide range (ppm to % level).The method has been successfully applied to a host of silicate rock, soil and sediment samples, and the results obtained have been validated by conventional pellet fluorimetry after pre-concentration of the analyte.

Radiological and chemical toxicity due to ingestion of uranium through drinking water in the environment of Bangalore, India

Groundwater samples collected from 96 bore wells in the study area (city of Bangalore) were analysed for concentration of natural uranium using laser-induced fluorimetry. The risk to the population of the region associated with radiological and chemical toxicity of uranium due to its ingestion through drinking water over a lifetime was estimated. The concentration of uranium was found to be in the range 0.136 to 2027.5 μg L−1 with an average value of 92.42 μg L−1. In the present study, about 61% of the samples show concentrations of uranium within the safe limit of 30 μg L−1 as set by the world health organisation. The radiological risk estimated as lifetime cancer risk is in the range 4.3 × 10−7 to 6.4 × 10−3 with an average of 2.9 × 10−4. The chemical toxicity risk measured as lifetime average daily dose is found to range from 0.005 to 75.42 μg kg−1 d−1. The reference dose estimated as 1.12 μg kg−1 d−1 was used to assess the chemical toxicity. The results indicate that the chemical toxicity due to ingestion of uranium through drinking water is of more concern than the radiological toxicity. The present study, being the first of its kind in this region, will augment the database of uranium in groundwater.

Uranium concentration in ground water samples belonging to some areas of Western Haryana, India using fission track registration technique

Incharge, Chemical Laboratory, Central Region Atomic Minerals Directorate for Exploration and Research Department of Atomic Energy, Civil Lines, Nagpur-440001(MS), India E-mail: dpsr2002@yahoo.com Dear Editor, I have read the above cited paper very carefully. The undersigned has been involved in the analysis of geological materials and hydro-geochemical reconnaissance surveys attached with mobile geochemical laboratories in different parts of India for uranium exploration activities of the Atomic Minerals Directorate for Exploration and Research. I have also contributed on uranium determination in diverse matrices vide my publications: 1. Rathore DPS, Kumar M, Tarafder PK (2012). Presentation of differential laser-induced fluorimetry as a reference measurement procedure for determination of total uranium content in ores and similar matrices. Accred. Qual. Assur. 17:75-84 2. Rathore DPS (2008). Advances in Technologies for the Measurement of Uranium in Diverse Matrices (Review article). Talanta 77:9-20. 3. Rathore DPS (2007). Trends in the Methods of Measurement in Analytical Chemistry. Explor. Res. At. Miner. 17:145-149. 4. Rathore DPS, Kumar M (2004). Analytical Applications of a Differential Technique in Laser-Induced Fluorimetry: Accurate and Precise Determination of Uranium in Concentrates and for Designing Microchemielectronic Devices for on-line Determination in Processing Industries. Talanta 62:343-349. 6. Tarafder PK, Kunkal L, Murugan P, Rathore DPS (2002). Ion-associate Solvent Extraction of Uranium with 2,3-Dihydroxynaphthalene and Cetyltrimethylammoniumbromide, and its fluorimetric Determination in Silicate Rocks. Radioanal. Nucl. Chem. 253:135-142. 7. Manjeet Kumar, Rathore DPS, Singh AK (2001). Quinalizarin Anchored on Amberlite XAD-2: A New Matrix for Solid-Phase Extraction of Metal Ions for Flame Atomic Absorption Spectrometric Determination. Fresenius J. Anal. Chem. 370:377-383. 8. Kumar M, Rathore DPS, Singh AK (2001). Pyrogallol Immobilized Amberlite XAD-2: A Newly Designed Collector for Enrichment of Metal Ions Prior to their Determination by Flame Atomic Absorption Spectrometry. Mikrochimica Acta 137:127-135. 9. Rathore DPS, Tarafder PK, Kayal M, Kumar M (2001). Application of a Differential Technique in Laser-Induced Fluorimetry: Simple and a Precise Method for the Direct Determination of Uranium in Mineralised Rocks at Percentage Level. Anal. Chim. Acta 434:201-208. 10. Kumar M, Rathore DPS, Singh AK (2000). Metal Ion Enrichment on Amberlite XAD-2 Functionalized with Tiron: Analytical Applications. Analyst 125:1221-1226.

Age-dependent dose and health risk due to intake of uranium in drinking water from Jaduguda, India

Uranium is a heavy metal that is not only radiologically harmful but also a well-known nephrotoxic element. In this study, occurrence of uranium in drinking water samples from locations near the uranium mining site at Jaduguda, India, was studied by Laser-induced fluorimetry. Uranium concentrations range from 0.03 ± 0.01 to 11.6 ± 1.3 µg l(-l), being well within the US Environmental Protection Agency drinking water limit of 30 μg l(-1). The ingestion dose due to the presence of uranium in drinking water for various age groups varies from 0.03 to 28.3 μSv y(-1). The excess lifetime cancer risk varies from 4.3×10(-8) to 1.7×10(-5) with an average value of 4.8×10(-6), much less than the acceptable excess lifetime cancer risk of 10(-3) for radiological risk. The chemical risk (hazard quotient) has an average value of 0.15 indicating that the water is safe for drinking.

Influence of physico-chemical parameters on the distribution of uranium in the ground water of Bangalore, India

Laser-Induced Fluorimetry has been used to measure the concentration of uranium in the ground water samples collected from the selected study locations of Bangalore city, India. The concentration of uranium in the collected water samples is found to be in the range 0.24 μg/l to 770.1 μg/l, with a geometric mean (GM) value of 18.9 μg/l. About 35% of the water samples show the concentration of uranium above the safe limit of 30 μg/l, set by the United States Environmental Protection Agency (USEPA). The annual effective dose associated with the ingestion of uranium by the adult population of the region has been estimated using the International Commission on Radiation Protection (ICRP) and World Health Organization (WHO) guidelines. Few physicochemical parameters of water such as pH, Total dissolved solids (TDS), major cations, major anions, and trace elements were also measured. The correlation coefficient among the measured parameters was determined to find the dependence, if any, on the concentration of uranium in the water samples.

Presentation of differential laser-induced fluorimetry as a reference measurement procedure for determination of total uranium content in ores and similar matrices

The metrological principle of ‘differential technique in laser-induced fluorimetry’ analysis is discussed and recommended as a reference measurement procedure for determination of total uranium content in ores and similar matrices. The estimated relative expanded uncertainty values obtained for uranium content in standard IAEA samples are, S 1, 0.04 g/kg, S 2, 0.06 g/kg, S 3, 0.04 g/kg, and for S 4, 0.10 g/kg, respectively. These low uncertainty values obtained for uranium show high metrological quality of differential technique. This reference measurement procedure guarantees the quality of an analytical result (accuracy, high precision, reliability, comparability, and traceability). Laser-induced fluorimetry will be useful for the analysis of uranium in ores, certification of reference materials, borehole core assay, and other diverse applications in nuclear fuel cycle. Differential technique in spectrophotometry/laser fluorimetry has inherent high metrological quality. In principle, laser-induced fluorimetry is an ideal technique for the very accurate determination of uranium by the use of appropriate fluorescence-enhancing reagents and methodology depending upon the concentration of uranium and sample matrices.

Assessment of age-dependent uranium intake due to drinking water in Hyderabad, India

A study has been done to assess the uranium intake through drinking water. The area of study is twin cities of Hyderabad and Secunderabad, India. Uranium concentration in water samples was analysed by laser-induced fluorimetry. The associated age-dependent uranium intake was estimated by taking the prescribed water intake values. The concentration of uranium varies from below detectable level (minimum detectable level = 0.20 ± 0.02 μg l(-1)) to 2.50 ± 0.18 μg l(-1), with the geometric mean (GM) of 0.67 μg l(-1) in tap water, whereas in ground water, the range is 0.60 ± 0.05 to 82 ± 7.1 µg l(-1) with GM of 10.07 µg l(-1). The daily intake of uranium by drinking water pathway through tap water for various age groups is found to vary from 0.14 to 9.50 µg d(-1) with mean of 1.55 µg d(-1).

Novel fusion method for direct determination of uranium in ilmenite, rutile, columbite, tantalite, and xenotime minerals by laser induced fluorimetry

A simple, rapid, effective and eco-friendly decomposition method is developed for the determination of uranium (U) by laser induced fluorimetry (LIF). The salts of sodium di-hydrogen phosphate (NaH2PO4) and di-sodium hydrogen phosphate (Na2HPO4) were used in the ratio of 1:1 (phosphate flux) for the decomposition and dissolution of refractory, non silicate minerals like ilmenite, rutile, columbite, tantalite, and xenotime. The effect of associated matrix elements (Ti, Fe, Nb, Ta, Mn and Y present in the sample) on quenching of uranyl fluorescence was studied. The flux used for the sample decomposition has several advantages. In the reported sample decomposition methods, α-hydroxy acids are used as complexing agents to prevent hydrolysis and to get clear and stable solution. This solution can not be directly used for U determination by LIF as α-hydroxy acids quench uranyl fluorescence, hence separation is required. In the present method no such separation is required. The flux itself acts as fluorescence enhancing reagent and buffer (maintaining the optimum pH of 7.1 ± 0.1). The fused melt of the flux mixture, when disintegrated in water, gives clear and stable solution and has high tolerance for most of inorganic quenchers compared to reported phosphate buffers. Also just by dilution (due to high sensitivity of LIF), the concentration of quenchers could be brought down well within the tolerance limit. The accuracy and precision of the method was evaluated by analyzing Certified Reference Materials (IGS-33 and IGS-34 of Institute of Geological Sciences, UK) and Synthetic Minerals. The accuracy of the data is further evaluated by comparing with standard decomposition methods. The results are well within the experimental error. The RSD of the method is ±10% (n = 6) at 10 ppm level for Ilmenite and for other minerals the RSD of the method is ±5% (n = 6) at 50 ppm level. The method is being routinely applied to various refractory samples received from Rare Metal and Rare Earth Investigations for determination of uranium by laser fluorimetry.

Distribution of uranium in drinking water and associated age-dependent radiation dose in India

Exposure due to natural radiation is of particular importance because it accounts for the largest contribution (nearly 85 %) to the total collective dose of the world population. An attempt has been made to present the feasibility of uranium occurrence in drinking water samples from different states of India, by laser-induced fluorimetry. The associated age-dependent radiation dose was estimated by taking the prescribed water intake values of different age groups. The concentration of uranium obtained, i.e. 0.1 +/- 0.01 to 19.6 +/- 1.8 microg l(-1), is well below the drinking water guideline value of 30 microg l(-1). The annual ingestion dose due to uranium in drinking water for various age groups is found to vary from 0.14 to 48 microSv y(-1).

Complexation of Lanthanide(III) and Actinide(III) Cations with Tridentate Nitrogen-Donor Ligands: A Luminescence and Spectrophotometric Study

The complexation of lanthanide(III) (lanthanum, europium, and lutetium) and americium(III) by four tridentate nitrogen-donor ligands was investigated in homogeneous methanol/water solutions by using structural and thermodynamic approaches. The stoichiometry and inner-sphere hydration state of the europium complexes formed were determined by time-resolved laser-induced fluorimetry. The stability constants and in some cases the thermodynamic parameters were measured by ultraviolet-visible spectrophotometry and the van’t Hoff method. The comparison of the stability constant of americium complexes with lanthanide complexes shows better stability for the actinide species. The strong affinity for these ligands toward Am3+ is confirmed by the formation of higher complexes, especially in the case of 2,6-bis-(5,6-dimethyl-1,2,4-triazin-3-yl)-pyridine (MeBTP), the only ligand able to form a 1:3 complex. The influence of the solvent composition on the complexation thermodynamics highlights the effect of the solvent reorganization on the reaction.

Analytical applications of a differential technique in laser-induced fluorimetry: accurate and precise determination of uranium in concentrates and for designing microchemielectronic devices for on-line determination in processing industries

A novel instrumental technique for the direct, fast, accurate, and precise determination of uranium in concentrates and other U-rich materials (as well as to mineralized rocks) is presented. The proposed technique is an absolute methodology, based on the comparison of the fluorescence of the accurately known standard with a sample of similar but unknown concentration in the low operational range of the instrument (on same sample-dilution basis), by the use of H 3PO 4–NH 4H 2PO 4 as a fluorescence-enhancing reagent. The relative standard deviation of the proposed technique was 0.5–0.9% ( n=9) at 18.1, 36.2, 61.2, and 99.6% U 3O 8. The proposed technique is suitable for the determination of uranium in samples arising from exploration projects, ores from mining operations, mill process samples, uranium ore concentrates leading to fuel fabrication as well as samples from environmental monitoring containing up to 100% uranium. The results are in good agreement with those obtained by titrimetric, gravimetric, and TBP extraction–H 2O 2 spectrophotometric methods. The precision of the technique is within the acceptable ‘pure geochemistry’ type of analysis (R.S.D. ∼ 1.0%) and is comparable even those obtained with titrimetric and gravimetric assay. The proposed differential technique coupled with flow injection may open up new advancement in instrumentation leading to design and development of microchemielectronic devices for direct on-line determination, more compatible with the tools of computer age as also to help in handling of radioactive solutions in chemical laboratories in uranium processing industries.

Time-resolved laser-induced fluorimetry for screening polycylic aromatic hydrocarbons on solid-phase extraction membranes

The potential of solid-phase extraction (SPE) time-resolved laser-induced fluorimetry (TRLIF) is evaluated for screening polycyclic aromatic hydrocarbons (PAHs) in aqueous samples. Octadecyl membranes are used with the dual purpose of extracting the pollutants from the water sample and serving as the solid substrate for fluorescence detection. Excitation of fluorescence is performed with a Nd:YAG pumped tunable dye laser pumped with a pulsed source for time-resolving spectral interference. Wavelength time matrices (WTMs) and real time-resolved fluorescence spectra are recorded with a pulsed delay generator, a spectrograph and an intensified charge-coupled device (ICCD). In comparison to SPE solid-matrix luminescence (SML) with conventional instrumentation, this approach provides better limits of detection (LOD) and selectivity. The improvement in LOD is of one order of magnitude, reaching the parts-per-trillion level with 10 ml of water sample. The improvement in selectivity allows the direct determination of target compounds in complex samples. The direct determination of benzo[ a]pyrene from a spiked river water sample of unknown composition is presented.

Screening potential of solid-phase extraction and solid surface room temperature fluorimetry for polycyclic aromatic hydrocarbons in water samples

The analytical potential of solid-phase extraction and room temperature fluorimetry for screening polycylic aromatic hydrocarbons in water samples is evaluated. Solid-phase extraction was performed via a syringe procedure previously reported (Talanta 52 (2000) 727). The simplicity of fluorescence measurements on the solid substrate is equivalent to solution measurements. Since oxygen quenching of fluorescence is not significant, placing the extraction membrane in the substrate holder of the spectrometer rapidly performs fluorescence measurements. Limits of detection at the pg ml −1 level were estimated for several pollutants. With a commercial spectrofluorimeter, benzo( a)pyrene was quantitatively determined at the 5 pg ml −1 concentration level. This concentration compared favorably to limits of detection estimated by laser-induced fluorimetry. A unique advantage of this approach was the possibility of adjusting the volume of extracted water to reach concentration levels below instrumental detection levels. Since SPE procedure was rapid and simple the trade-off of including an additional experimental step to lower limits of detection was advantageous. Although the selectivity of this approach was not fully investigated, our studies showed that selective excitation was sufficient to identify benzo( a)pyrene in a seven-component mixture and spiked Red River water of unknown composition.

Application of a differential technique in laser-induced fluorimetry: simple and a precise method for the direct determination of uranium in mineralised rocks at the percentage level

A simple, rapid, cost-effective, accurate and precise differential laser-induced fluorimetric method for the direct determination of uranium in mineralised rocks at the percentage level is presented, based on the comparison of the fluorescence of the standard with a sample of similar but unknown concentration on the same sample weight basis, by the use of H 3PO 4–NH 4H 2PO 4 as a fluorescence enhancing reagent. The relative standard deviation of the method was 0.3–0.5% ( n=9) for 0.04 and 3.4% U 3O 8. The proposed technique is suitable for the determination of uranium in samples containing >0.01% uranium. The method has been evaluated using standards, SY-2, SY-3, low grade uranium ore-IAEA reference samples and core samples of diverse matrices. The results are in good agreement with the published data and those obtained by conventional fluorimetry and other methods and are of comparable precision to those obtained by titrimetric assay.

Depth-profiling of organic layers on microparticles with SNMS

Previous work on the quantification and localization of organically bound elements with plasma-based SNMS for the characterization of microparticles has been continued. Relative detection factors for 10 elements have been determined. Except for lead and bromine a principle proportionality to atomic ionization probabilities is shown. A moderate matrix dependence of less than 40% variation was found even when inorganic and organic materials are included. For depth calibration, erosion rates of organic materials were determined from the time interval necessary to sputter through planar single-layers and Langmuir-Blodgett multi-layer systems with known thickness, as well as from gravimetric powder measurements. Depth propagation rates were 0.7 nm·sec−1 for polymers and 2.3 nm·sec−1 for aromatic compounds, when 400 eV argon ion bombardment with 0.7 mA·cm−2 was used. A depth resolution of ∼30 nm has been obtained. Model particles of 5 μm size have been coated with fluoranthene. Inspection with SNMS revealed an incomplete coating covering only 20% of the microparticle surface with an average thickness of the partial coating of 300 nm. Subsequent characterization using laser-induced fluorimetry confirmed the amount of fluoranthene coating measured by SNMS.

On-line determination of iodine in nuclear fuel reprocessing off-gas streams by a combination of laser-induced fluorimetry and laser photoacoustic spectroscopy

The on-line determination of molecular iodine and orgabic iodides in nuclear fuel reprocessing off-gas streams containing high concentration of NO itx gas was studied. Ultraviolet radiation is used to convert organic iodides into molecular iodine. The approximate concentration of iodine before and after the photochemical conversion in the presence of NO itx gas was first determined by laser-induced fluorimetry. NO 2 was determined by photoacoustic spectroscopy, correcting the acoustic signal due to iodine by using the approximate iodine concentrion. NO was determined from the concentrations of NO 2 before and after the photoirradiation based on the photochemical fraction changes of NO and NO 2. The quenching of the fluorimetry due to NO and NO 2 was finally corrected with the NO and NO 2 concentrations obtained. The detection limit of the proposed method is 10 nl 1 -1.

In Vivo Fluorescence of Human Skin

Fluorescence is a feature of elastin and collagen, both major compounds of human dermis that are altered by age and photoexposure. We studied the intrinsic fluorescence of skin in vivo in 28 human volunteers to determine whether photoaging and chronologic aging of the skin could be evaluated by this noninvasive technique. We demonstrate that the excitation of skin autofluorescence by laser ultraviolet radiation yields characteristic tissue fluorescence spectra that are unrelated to age, pigmentation, or skin thickness. The differences in skin autofluorescence appear to be related to photoexposure. Thus, laser-induced fluorimetry, a noninvasive technique, may be adaptable as a marker of photoaging.