| Partâ… Determination of Gallium by Cloud Point Extraction-Spectral AnalysisGallium is a kind of rare metal with good application prospect in medicine.Gallium mainly was used for scanning and locating bone neoplasms and some solid tumors.In recent years,it has been found that gallium has an obvious effect on anti-cancer.In addition,gallium has anti-inflammation and enhancing immune function.In order to research its biological function and dose-effect relationship,the quantitative detection method of gallium is essential. However,many existing determination methods are suitable to determine gallium in mineral and metallurgical materials.There are few reports on determination of gallium in biological samples(e.g.,serum) and plant samples(e.g.,Chinese herbal medicine).Moreover,most methods used the volatile organic solvent to extract gallium,which results in environmental pollution and health risk for laboratory technician.Cloud point extraction(CPE) is a kind of new environmentally benign extraction method without use of volatile organic solvents,which based on the solubility and cloud point phenomenon of aqueous solution of non-ionic or zwitterionic.Upon alteration of the experimental conditions such as temperature,pH and ionic strength of solution,the solution is separated into two phases.The analyte is parted from the aqueous solution,and enriched in surfactant rich phase.It is an easy,safe,high efficiency and economical methodology for preconcentration and separation.CPE has been widely used for separation and analysis of biomacromolecule,traces metal elements,and organic toxicants.The aim of this study is to establish methods for the determination of trace gallium by spectrofluorimetry and graphite furnace atomic absorption spectrometry coupled with cloud point extraction.That will provide environment friendly,efficient,easy,green analytical techniques for determination of gallium.Methods1.CPE-Fluorescence SpectrophotometryA CPE procedure,which used Triton X-114 as nonionic surfactant and 8-hydroxyquinoline(8-HQ) as chelating agent,was developed for the extraction of Ga in water samples prior to its determination by fluorescence spectrophotometry.The main factors affecting CPE efficiency,such as pH of sample solution,concentration of 8-HQ and Triton X-114,equilibration temperature and time,were optimizated in detail.The proposed method is applied to determination of trace amount of gallium in water samples.2.CPE- Graphite Furnace Atomic Absorption SpectrometryThe process of cloud point extraction was same with the above-mentioned methods.To reduce the viscosity of the surfactant rich phase prior to GFAAS analysis,0.40 mL of methanol acidified with 0.1 mol·L-1 HNO3 was added to it.The proposed method was applied to determination of trace amount of gallium in Chinese herbal medicine and serum.Chinese herbal medicine and serum were digested by 65%nitric acid before determination.Results1.CPE- Fluorescence SpectrophotometryUnder optimum conditions,the extraction efficiency of gallium was 89.5%,The calibration graphs using the preconcentration system for gallium were linear over the range 0.05～1.50μg·mL-1.The detection limit(DL) of gallium for the preconcentration of 10 mL solution was 0.03μg·mL-1.The relative standard deviation of this method for 0.10μg·mL-1, 0.50μg·mL-1 and 1.50μg·mL-1 gallium standard solution were 5.5%,1.4%and 4.1%(n=7).CPE-Fluorescence spectrophotometry was applied to the determination of gallium in water samples.The results showed that gallium was not detected in tap water and river water, and average recoverys were 97.3%and 92.0%.2.CPE- Graphite Fumace Atomic Absorption SpectrometryUnder optimum conditions,a preconcentration factor of 20 was achieved.The detection limit(DL) of gallium was 2pg.The extraction ratio of gallium was higher than 98%.The calibration graphs using the preconcentration system for gallium were linear over the range 0.002～0.020μg·mL-1.The relative standard deviation of this method for 0.002μg·mL-1, 0.010μg·mL-1 and 0.020μg·mL-1 gallium standard solution were 14.3%,5.5%and 6.1%(n=7).CPE-Graphite Furnace Atomic Absorption Spectrometry was applied to the determination of gallium in serum and Chinese herbal medicine with satisfactory result. Average recoveries between 95.6%and 104.8%were obtained for spiked samples.ConclusionCloud point extraction is a simple,environment-friendly,efficient separation and preconcentration method of trace metals.Cloud point extraction for preconcentration and separation of gallium has not yet been reported.In this study,Cloud point extraction to preconcentrate trace levels of gallium as a prior step to its determination by fluorescence spectrophotometry and graphite furnace atomic absorption spectrometry has been developed. The method was not only simple,high sensitivity,low detection limit,high accuracy,but also did not use toxic and harmful organic solvents.These methods were used for the determination of trace gallium in samples with satisfactory results. Partâ…¡Influence of Solvent Scattering on SpectrofluorimetryIt had been known that solvents could change the spectrum and the strength of the fluorescent material.The scattered light of solvents also has the same influence to some extant.However there were only several reports on this topic and the corresponding data was incomplete.The purpose of this article is to further investigate the regularity of scattering of four commonly used solvents such as water,ethanol,chloroform and carbon tetrachloride in spectrofluorimetry,and the effect on the measurement of the fluorescence of very dilute solutions.MethodsThe most prominent Raman bands and scattering intensity of four commonly used solvents were recorded by a spectrofluorimeter with the different exciting light.Results1.Raman SpectraRaman spectra of different kind of solvents are different,and Raman bands changes with that of the exciting light.But frequency shifts,that the frequency of Raman scattered light is compared with that of the exciting light,are constant for a given substance and independent of the exciting frequency.Water showed two prominent Raman bands corresponding to shifts in frequency of 0.348μm-1 and 0.172μm-1 in the fluorescence spectrum.The frequency shifts of ethanol were 0.306,0.150μm-1 and 0.075μm-1,that of chloroform were 0.307μm-1 and 0.155μm-1.The frequency shift of carbon tetrachloride was not obtained,owing to the Raman peak overlapped partly with the Rayleigh band,and the relative intensity of the Raman peak was also very weak.According to the definition of frequency shift,the relationship was established among the wavelength of the Raman peak,frequency shifts of the Raman peak and wavelength of the exciting light,λRaman=λex/(1-Δσ·λex).By this rule,the positions of the most prominent Raman bands could be predicted.2.Scattering Light IntensityIn spectrofluorimetry,the Rayleigh scattering light intensity of four solvents had the same regularity changes.Furthermore,the variation of the Rayleigh and Raman scattering light intensity for water,ethanol and chloroform showed identical.In respect of the same solvent,solvent scattering light intensity excited at UV district was larger than excited at long wavelength district.In terms of different solvents,the order of scattering light intensity is ethanol＞water＞chloroform＞carbon tetrachloride.Therefore,solvent scattering has small interference on fluorescence spectrum excited at long wavelength light.Carbon tetrachloride was less affected on the fluorescence analysis.ConclusionThe results showed that,the impact of solvent scattering on fluorescence analysis was not only related to the type of solvent,but also to the excitation wavelength.If we knew that change rule of the scattering and their interferences with the excitation and emission spectra, it will be helpful for selecting optimum excitation and emission wavelength in the fluorescent analysis.
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