Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 123 (2014) 110–116

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Spectrochimica Acta Part A: Molecular andBiomolecular Spectroscopy

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Spectroscopic study on the reactions of bis-salophen with uranyland then with fructose 1,6-bisphosphate and the analytical application

1386-1425/$ - see front matter � 2013 Elsevier B.V. All rights reserved.http://dx.doi.org/10.1016/j.saa.2013.12.026

⇑ Corresponding author. Tel.: +86 734 8280649; fax: +86 734 8282375.E-mail address: llfcxllc@163.com (L. Liao).

Xing Shen, Lifu Liao ⇑, Lin Chen, Yunfei He, Canhui Xu, Xilin Xiao, Yingwu Lin, Changming NieCollege of Chemistry and Chemical Engineering, University of South China, Hengyang, Hunan 421001, China

h i g h l i g h t s

� Bis-salophen reacts with uranyl toform binuclear complex uranyl-bis-salophen (UBS).� UBS reacts with fructose 1,6-

bisphosphate (F-1,6-BP) to formsupramolecular polymer.� The two reactions were studied by

fluorescence and RLS spectroscopy,respectively.� Based on the reactions a fluorescence

method for detecting U (VI) wasestablished.� A RLS method for detecting F-1,6-BP

was also established.

g r a p h i c a l a b s t r a c t

a r t i c l e i n f o

Article history:Received 3 August 2013Received in revised form 16 November 2013Accepted 5 December 2013Available online 18 December 2013

Keywords:Bis-salophenUranylFructose 1,6-bisphosphateFluorescenceResonance light scattering

a b s t r a c t

The chelating reaction of bis-salophen with uranyl to form binuclear complex uranyl-bis-salophen (UBS)was studied by fluorescence spectroscopy. The coordination reaction of UBS with fructose 1,6-bisphos-phate (F-1,6-BP) to form supramolecular polymer was then studied by resonance light scattering (RLS)spectroscopy. The reaction of bis-salophen with uranyl results in a remarkable enhancement of fluores-cence intensity. The maximum emission wavelength of the fluorescence is at 471 nm. The reaction of UBSwith F-1,6-BP results in a remarkable enhancement of RLS intensity. The maximum scattering wave-length of the RLS is at 460 nm. The two reactions were used to establish fluorescence method for thedetermination of uranium (VI) and RLS method for the determination of F-1,6-BP, respectively. Underoptimum conditions, the linear ranges for the detection of uranium (VI) and F-1,6-BP are 0.003–0.35nmol/mL and 0.05–5.0 nmol/mL, respectively. The detection limits are 0.0017 nmol/mL and 0.020nmol/mL, respectively. The proposed fluorescence method has been successfully applied for the determi-nation of uranium (VI) in environmental water samples with the recoveries of 97.0–104.0%. The proposedRLS method has also been successfully applied for the determination of F-1,6-BP in medicine injectionsamples with the recoveries of 98.5–102.3%.

� 2013 Elsevier B.V. All rights reserved.

Introduction

The reactions of ditopic ligands with metal ions to form binu-clear complexes and their metallo supramolecular polymers havebecome of increasing interest in the last ten years. These reactionsoffer possibilities for the use in various fields due to produced var-

ious properties. The examples of applications include the use inoptical [1,2], luminescent [3,4], molecular recognition and sensing[5,6] fields. At present, a few of ditopic terdentate ligands and sev-eral metal ions have been studied for the reactions of forming cor-responding complexes and polymers [7–11]. However, up to date,ditopic tetradentate ligands and ditopic monodentate ligands aswell as uranyl ion are hardly studied for reactions of forming binu-clear complexes and their supramolecular polymers.

X. Shen et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 123 (2014) 110–116 111

Uranium is an important element and has been widely used asnuclear fuel. It is also high toxic and can severely damage humanhealth and environment. Therefore, it is very important to studyproper analytical method for the detection of uranium in waterand environment [12–15]. Uranium can also be used in other fieldsdue to its special advantages in structure and property, such asused as catalysts, analytical reagents and high density material[16–19]. Nevertheless, exploiting new application of uranium isstill an interesting research field. Utillizing the reactions of uranylwith ditopic ligands to form uranyl-based binuclear complexes andsupramolecular polymers can provide the possibility for the re-search of new application of uranium as well as new uranium ana-lytical method.

Salophen is a tetradentate Schiff base ligand. It can combineuranyl cation to form stable uranyl–salophen complex [20]. Hencesalophen is an excellent reagent used for recognition of uranium[21]. Since uranyl cation typically adopts a pentacoordinate envi-ronment, a tetradentate salophen ligand in uranyl–salophen com-plex leaves one site open for coordination to another molecule[22,23]. Thus, a uranyl–salophen complex is easily to bind a mono-dentate ligand to form a stable sandwich-type supramolecule:salophen–uranyl-monodentate ligand. Previous study demon-strated that the monodentate ligands can be phosphate and itsderivatives such as adenosine triphosphate, and uranyl–salophencomplex has strong ability to recognize these monodentate ligandswith high affinity and high selectivity [24–27]. Therefore, it is pos-sible to utilize the coordination reactions of salophen to uranyl anduranyl–salophen complex to monodentate ligands for the con-struction of binuclear uranyl complexes and corresponding metallosupramolecular polymers.

Fructose 1,6-bisphosphate (F-1,6-BP) is a ditopic monodentateligand containing two phosphate groups. It is an important sub-strate in living organisms and involved in many diseases for thetreatment and diagnosis [28–30]. The detection of F-1,6-BP is ofimportance in pharmaceutical analysis, clinical diagnosis and bio-chemical study [31–33].

Here, for the first time, we have studied the chelating reactionof bis-salophen, which is a ditopic tetradentate ligand, with uranylto form binuclear complex uranyl-bis-salophen (UBS) by fluores-cence spectroscopy, and then studied the coordination reactionof UBS with F-1,6-BP to form supramolecular polymer by reso-nance light scattering (RLS) spectroscopy. Based on the two reac-tions, we have established a fluorescence method for thedetermination of uranium (VI) and a RLS method for the determi-nation of F-1,6-BP. The two proposed methods have been success-fully applied for the analysis of real samples with satisfactoryresults.

Experimental

Materials and apparatuses

Salicylaldehyde and 3,30,4,40-tetraminobiphenyl were pur-chased from Aladding (Shanghai, China). Uranyl nitrate hexahy-drate was obtained from Aldrich (Milwaukee, WI, USA).Fructose 1,6-bisphosphate, trisodium salt (F-1,6-BP) was pur-chased from Sigma (Oakville, ON, USA). Other chemicals werepurchased from Merck and Aldrich. All chemicals used were ofanalytical grade.

Fluorescent spectra and RLS spectra were recorded on a Hitachi4500 spectrofluorometer. 1H NMR spectra were obtained from aBruker 300-MHz NMR spectrometer. FT-IR spectra were taken ona Shimadu IR Prestige-21 FTIR spectrophotometer in the range of4000–400 cm�1. Elemental analyses were carried out with a Ther-mo Finnigan EA 1112 elemental analyzer.

Preparation of bis-salophen

The ditopic tetradentate Schiff base ligand, or bis-salophen, was pre-pared according to the procedure involving Schiff base condensation oftetramine with hydroxyaldehyde. Salicylaldehyde (1.05 g, 10 mmol)and 3,30,4,40-tetraminobiphenyl (0.535 g, 2.5 mmol) were dissolvedin 25 mL of methanol. The mixture was stirred for 1 h under refluxand then cooled to room temperature. The resulting yellow solid mass,N0; N00; N000-tetrasalicylidene-3; 30-diaminobenzidine ðbis-salophenÞ,was filtered, and the product was recrystallized from THF and driedunder vacuum. The preparing reaction and chemical structure ofbis-salophen is shown in Fig. 1.

The ligand was characterized by analytical and spectral data.For elemental analysis of C40H30N4O4, calculated results are the fol-lowing: C 76.19, H 4.76, N 8.88; found: C 75.82, H 4.85, N 8.67. For1H NMR (300 MHz, CDCl3), d results are the following: 13.01 (s, 4H,OH), 8.66 (s, 4H, imino bond), 7.45–6.95 (m, 22H, ArH). For FT-IR(KBr pellet, m (cm�1)), absorption results are the following: 3452(OAH stretching), 1616 (C@N stretching), 1408 (CAO stretching),1097 (CAN stretching), 619 (CAH deformation). The presence ofimino bonds indicated by 1H NMR and IR spectroscopy demon-strates the formation of the ditopic tetradentate Schiff base ligand.

Bis-salophen solution (5.0 nmol/mL) used for the detection ofuranium (VI) was prepared by dissolving the obtained bis-salophenin water containing 5% (v/v) DMSO.

Preparation of binuclear uranyl Schiff base complex UBS

The complex was prepared by the following procedure. Bis-salo-phen (0.158 g, 0.25 mmol) and uranyl nitrate hexahydrate (0.251 g,0.5 mmol) were dissolved in 25 mL of DMF. The mixture was stir-red for the chelating reaction. After completion of the reaction, thesolution was removed under reduced pressure. The obtained solidmass was purified by using a silica gel column, and eluted withchloroform–acetone mixture. Evaporation of solvent under re-duced pressure afforded the solid binuclear uranyl bis-salophencomplex. The preparing reaction and chemical structure of UBS isalso shown in Fig. 1.

The binuclear uranyl complex was characterized by 1H NMRand IR spectral data. For 1H NMR (300 MHz, CDCl3), d results arethe following: 9.60 (s, 4H, imino bond), 7.8–6.7 (m, 22H, ArH).For FT-IR (KBr pellet, m (cm�1)), absorption results are the follow-ing: 1608 (C@N stretching), 1382 (CAO stretching), 1103 (CANstretching), 891 (U@O stretching), 619 (CAH deformation). Thechemical shift signal of OH groups at d13.01 which is present inthe 1H NMR spectrum of bis-salophen disappears upon complexa-tion. The absorption band of OH groups in the region 3500–3400cm�1 which is present in the IR spectrum of bis-salophen also dis-appears upon complexation. These results indicate the formationof the binuclear complex.

UBS solution (0.1 lmol/mL) used for the detection of F-1,6-BPwas prepared by dissolving the obtained UBS in water containing20% (v/v) DMSO.

Procedure of uranium detection by fluorescence method

An appropriate amount of uranium (VI) calibration solution orsample solution, 1.0 mL of pH 6.0 2-(N-morpholino) ethane sul-fonic acid (MES) buffer solution and 1.0 mL of Diethylene triaminepenlaacetic acid (DTPA) masking agent solution were added into a10 mL volumetric flask. The solution volume was fixed at 9 mLwith water. Then under stirring 1.0 mL of bis-salophen solutionwas dropped into the uranium (VI) solution containing MES andDTPA with a total dropping time of 10 min. After bis-salophenwas dropped, the fluorescence spectra of the system were recordedon the spectrofluorometer. A calibration curve of the emission

Fig. 1. Illustrated procedures of preparing ditopic tetradentate ligand bis-salophen, preparing binuclear complex uranyl-bis-salophen (UBS), detecting uranium (VI) byfluorescence method and detecting fructose 1,6-bisphosphate (F-1,6-BP) by RLS method.

112 X. Shen et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 123 (2014) 110–116

fluorescence intensity versus uranium (VI) concentration was plot-ted. The procedure of uranium (VI) detection is also illustrated inFig. 1.

Procedure of F-1,6-BP detection by resonance light scattering method

An appropriate amount of F-1,6-BP calibration solution or sam-ple solution, 1.0 mL of pH 6.0 MES buffer solution and 1.0 mL ofUBS solution were added successively into a 10 mL volumetricflask. The total volume of the solution was fixed at 10 mL withwater. The solution was mixed thoroughly and was incubated for30 min. The RLS spectra of the system were recorded on thespectrofluorometer. A calibration curve of the RLS intensity versusF-1,6-BP concentration was plotted. The procedure of F-1,6-BPdetection is also illustrated in Fig. 1.

Results and discussion

Fluorescence spectra of bis-salophen and uranyl system

The emission fluorescence spectra of bis-salophen in the pres-ence of different concentrations of uranyl are shown in Fig. 2.The figure reveals that the fluorescence intensity of bis-salophenis weak in the absence of uranyl. The fluorescence intensity of ura-nyl is also weak in the absence of bis-salophen. When bis-salophenand uranyl coexist in the solution, bis-salophen reacts with uranyl

to form binuclear uranyl complex with rigid plane structure,resulting in the enhancement of the fluorescence intensity. Theexperimental results demonstrate that the maximum excisionand emission wavelengths are at 346 nm and 471 nm, respectively.Under a certain concentration condition of bis-salophen, the fluo-rescence intensity is lineariy enhanced with the increase of theamount of uranium, which demonstrates that the chelating reac-tion of bis-salophen with uranyl can be used to establish a fluores-cence method for the determination of uranium (VI). In this workthe fluorescence intensity at 471 nm was selected for the detectionof uranium (VI).

Resonance light scattering spectra of UBS and F-1,6-BP system

The experimental results show that when UBS reacts with F-1,6-BP, there is no obvious change in the fluorescence, but thereis distinct change in the RLS. Fig. 3 displays the RLS spectra ofUBS and F-1,6-BP system. It is apparent that the RLS intensity ofUBS is weak in the absence of F-1,6-BP. The RLS intensity of F-1,6-BP is also weak in the absence of UBS. However, in the coexis-tence of UBS and F-1,6-BP, the supramolecular polymers with largemolecunlar volumes are formed by the coordination reaction ofUBS with F-1,6-BP, resulting in the enhancement of the RLS inten-sity. The maximum scattering wavelength is at 460 nm. Under acertain concentration condition of UBS, there is a linear relation-ship between the enhanced RLS intensity at 460 nm and the

Fig. 2. Emission fluorescence spectra of bis-salophen and uranium (VI) system. The concentration of bis-salophen is 0.5 nmol/mL. The concentrations of uranium (VI) are (a)0.0, (b) 0.05, (c) 0.1, (d) 0.15, (e) 0.2, (f) 0.25, (g) 0.3 and (h) 0.35 nmol/mL. The calibration curve is shown as an inset.

Fig. 3. RLS spectra of UBS and F-1,6-BP system. (a) The concentration of F-1,6-BP is 5.0 nmol/mL and UBS is absent. (b)–(g) The concentration of UBS is 10.0 nmol/mL and theconcentrations of F-1,6-BP are (b) 0.0, (c) 1.0, (d) 2.0, (e) 3.0, (f) 4.0 and (g) 5.0 nmol/mL. The calibration curve is shown as an inset.

X. Shen et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 123 (2014) 110–116 113

concentration of F-1,6-BP in a certain range. Therefore, a RLS meth-od for the determination of F-1,6-BP can be establish by using thecoordination reaction of UBS with F-1,6-BP. In this work the RLSintensity at 460 nm was selected for the detection of F-1,6-BP.

Optimum conditions for the determination of uranium (VI) using bis-salophen as ligande

Effect of the acidityThe effect of pH on the fluorescence intensity of bis-salophen

and uranyl system was investigated. The fluorescence intensityvaries as the pH of the solution is varied. It reaches maximumand keeps constant in the pH range of 5.5–7.5. When pH is higherthan 7.5 or lower than 5.5, the fluorescence intensity decreases.The results demonstrate that the experiment needs to be carriedout in weakly acidic medium or neutral medium. The reason maybe that in strong acidic medium the coordination ability of bis-salo-phen to uranyl is weak due to its protonation, and in basic medium

the binding ability of uranyl cation to bis-salophen is also weak dueto its hydrolyzation. The selection of proper buffer system was alsostudied. Although phosphate is the most commonly used buffersystem for preparation of neutral buffer, it affects the coordinationreaction between uranyl and bis-salophen due to its strong com-bining capability to uranyl. Therefore, in this work the solutionacidity was controlled with a pH 6.0 MES buffer.

Effect of bis-salophen concentrationThe effect of bis-salophen concentration on the fluorescence

intensity of the system was investigated. The results show thatfor a certain amount of uranium (VI), the enhanced fluorescenceintensity depends on the concentration ratio of bis-salophen touranium (VI) strongly. When the concentration ratio is less than0.5, the fluorescence intensity is enhanced with the increase ofthe concentration of bis-salophen. When the concentration ratioreaches 0.5 or is higher than 0.5, the fluorescence intensity reachesmaximum and keeps constant due to the complete complexation

114 X. Shen et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 123 (2014) 110–116

of bis-salophen with uranyl. The results further show that whenthe concentration of uranyium (VI) is 0.35 nmol/mL or less than0.35 nmol/mL and the concentration of bis-salophen is 0.18 nmol/mL or higher than 0.18 nmol/mL, there is a linear relationship be-tween the fluorescence intensity and the uranyium (VI) concentra-tion. In this work the selected concentration of bis-salophen for thedetermination of uranium (VI) was 0.5 nmol/mL.

Effect of addition sequence of the reagents and incubation timeThe effect of addition sequence of the reagents was tested. The

results show that the linear relationship between the fluorescenceintensity and uranium (VI) concentration with the addition se-quence of dropping bis-salophen into uranium (VI) solution is bet-ter than that with the addition sequence of dropping uranium (VI)into bis-salophen solution. The reason may be that when bis-salo-phen is dropped into uranium (VI) solution, the reaction product isbinuclear uranyl complex. Otherwise, when uranium (VI) isdropped into bis-salophen solution, the reaction product is a mix-ure of binuclear uranyl complex and mononuclear uranyl complex.The effects of total dropping time of dropping bis-salophen intouranyl solution and the incubation time after dropped were alsoinvestigated. The results show that when the total dropping timeis more than 8 min, the linear relationship is good. The results alsoshow that after dropped the fluorescence intensity of the mixturereaches the maximum immediately and keeps constant, or themixture needs not an additional incubation time. Therefore, in thiswork the selected addition sequence is dropping bis-salophen intouranium (VI) solution with a total dropping time of 10 min. Thefluorescence intensity was measured immediately after droppedwithout additional incubation time.

Optimum conditions for the determination of F-1,6-BP

Effect of the acidityThe effect of pH on the RLS intensity of UBS and F-1,6-BP system

was investigated. The RLS intensity was found to increase at firstand then decrease with the increase of the solution pH, and wasfound to reach maximum in a pH range of 5.5–8.0. The resultsdemonstrate that the incubation reaction also needs to be carriedout in weakly acidic medium or neutral medium, because in acidicmedium the binding affinity between UBS and F-1,6-BP is weakdue to the protonation of phosphate group in F-1,6-BP, and in basicmedium the binding affinity is also weak due to the hydrolyzationof uranyl. In this work the solution acidity was controlled at pH 6.0by using MES as a buffer for the reaction of UBS with F-1,6-BP.

Effect of UBS concentrationThe effect of UBS concentration on the RLS intensity of the sys-

tem was investigated. The results show that the enhanced RLSintensity depends on the concentration of UBS. When UBS concen-tration is low, the RLS intensity of system is also low due to theincomplete reaction of F-1,6-BP. With the increase of UBS concen-tration, the RLS signal becomes stronger gradually. When UBS con-centration is in the range of 5.0–20.0 nmol/L, the RLS intensityreaches the maximum and keeps constant. When UBS concentra-tion is higher than 20.0 nmol/L, Although the RLS intensity isstrong, the linear relationship is not good. Considering the sensitiv-ity and linear relationship simultaneously, 10.0 nmol/L of UBS wasemployed in this experiment.

Effect of addition sequence of the reagents and incubation timeThe effect of addition sequence of the reagents was tested. The

results show that addition sequence hardly affects on the RLSintensity of the system. In this work the used addition sequencewas adding UBS into F-1,6-BP solution. After mixed, the RLS inten-

sity is enhance with the increase of incubation time. When theincubation time is over 20 min, the RLS intensity reaches maxi-mum and keeps constant. In this work the selected incubation timewas 30 min.

Analytical parameters

Analytical parameters for the determination of uranium (VI)Under optimal conditions the calibration curve for the determi-

nation of uranium (VI) was tested with different amounts of ura-nium (VI) according to the general procedure. The curvedemonstrates that there is a linear relationship between the fluores-cence intensity (F) and the uranium (VI) concentration (c) in therange of 0.003–0.35 nmol/mL (Fig. 2, inset). The linear regressionequation is F = 207.3 c (nmol/mL) + 2.9 with a correlation coefficientof r = 0.9995. The detection limit of the method was determined tobe 0.0017 nmol/mL calculated from three times the standard devia-tion through 11 parallel blank tests. The relative standard deviation(RSD) of six parallel determinations for 0.2 nmol/mL uranium (VI)was 2.37%.

Analytical parameters for the determination of F-1,6-BPThe calibration curve of RLS intensity (IRLS) against the concen-

tration of F-1,6-BP (c) was also tested under optimal conditions.There is a good linear relationship between IRLS and c in the rangeof 0.05–5.0 nmol/mL. The linear regression equation is IRLS = 67.3 c(nmol/mL) + 23.5 and the correlation coefficient is 0.9992. Thedetection limit is 0.020 nmol/mL calculated from three times thestandard deviation through 11 parallel blank tests. The RSD of sixparallel determinations for 3.0 nmol/mL F-1,6-BP is 3.52%.

Influences of coexistent substances

Influences of coexistent metal ions to the detection of uraniumSome coexistent metal ions can compete with uranium to react

with bis-salophen, resulting in the interference in the detection ofuranium (VI). DTPA was found to be an excellent masking agent oflots of metal ions for the detection of uranium (VI). The influence ofthese metal ions to the detection of 0.2 nmol/mL uranium (VI) inthe presence of 0.1 mmol/L of DTPA was investigated. The influ-ence was examined individually by adding a relatively high con-centration of these ions. An error of less than 5% was consideredto be no influence to the determination of uranium (VI). The resultsshown that 10 times of Ca2+, Mg2+, Al3+, Mn2+, Fe3+, Zn2+, Cd2+, Cu2+

and Pb2+ do not interfere with the determination. The experimen-tal results indicate that this method is suitable for the detection ofuranium (VI) in samples containing other competitor metal ions.

Influences of coexistent substances to the detection of F-1,6-BPIn F-1,6-BP pharmaceuticals, the major substances coexisting

with F-1,6-BP are fructose 6-phosphate, fructose and inorganicphosphate. The influence of these coexistent substances to thedetection of 2.0 nmol/mL of F-1,6-BP was investigated, whichwas examined individually by adding these compounds. An errorof less than 5% was considered to be no influence to the determina-tion of F-1,6-BP. The results show that equivalent amount of fruc-tose 6-phosphate and inorganic phosphate has no influence to thedetermination. Moreover, fructose does not interfere with thedetermination. These results demonstrate that this method isselective toward F-1,6-BP, since it has two phosphate groups andboth play a key role in the formation of the supramolecular poly-mer with large molecunlar volume.

Table 1Analytical results of uranium (VI) in environmental water samples.

Sample Founda (nmol/mL) R.S.D (%) Standard added (nmol/mL) Total found (nmol/mL) Recovery (%)

1 – – 0.200 0.197 98.52 0.052 3.8 0.200 0.257 102.53 0.048 4.4 0.200 0.242 97.04 0.035 4.7 0.200 0.243 104.0

a Mean value of six measurements.

Table 2Analytical results of F-1,6-BP in diluted medicine injection samples.

Sample Founda (nmol/mL) RSD (%) Added (nmol/mL) Total found (nmol/mL) Recovery (%)

1 2.25 1.65 2.00 4.22 98.52 1.89 2.24 2.00 3.88 99.53 2.02 2.07 2.00 4.03 100.34 2.13 1.54 2.00 4.18 102.3

a Mean value of six measurements.

X. Shen et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 123 (2014) 110–116 115

Analysis of real samples

Analysis of environmental water samples containing uraniumIn order to test the validation of the fluorescence method for

real samples, the uranium (VI) in four environmental water sam-ples contaminated by different uranium slag heaps were separatedand analyzed directly by this method. The recovery experiment ofadded standard uranium concentrations was also carried out toevaluate applicability and reliability of this developed method incomplex system. The results summarized in Table 1 demonstratethat the new fluorescence method based on the reaction of bis-salophen with uranyl can be successfully applied to real sampleswith good recoveries.

Analysis of pharmaceutical samples containing F-1,6-BPThe proposed RLS method was applied to real samples. The real

samples are F-1,6-BP medicine injections with the indicated con-centrations of 0.10 mmol/mL of F-1,6-BP calcium salt or0.075 mmol/mL of F-1,6-BP sodium salt as well as less than0.01 mmol/mL of fructose 6-phosphate, fructose and inorganicphosphate (Hebei Changtian Pharmaceuticals, China). The F-1,6-BP injections were diluted directly step by step to a proper concen-tration range with water as diluter. The dilutions were analyzedaccording to the experimental procedure of F-1,6-BP detection.To evaluate the applicability and reliability of this developed meth-od, the recovery experiment of added standard F-1,6-BP concentra-tions was also carried out. All results were summarized in Table 2.The results demonstrate that the new RLS method based on thereaction of UBS with F-1,6-BP can be successfully applied to realpharmaceutical samples with good recoveries.

Conclusions

In summary, for the first time, we studied the chelating reactionof bis-salophen with uranyl to form UBS by fluorescence spectros-copy and the coordination reaction of UBS with F-1,6-BP to formsupramolecular polymer by RLS spectroscopy. Utilizing the tworeactions we established a fluorescence method for the determina-tion of uranium (VI) and a RLS method for the determination of F-1,6-BP. The two proposed methods have been successfully appliedfor the analysis of real samples with satisfactory results. The prin-ciple of studying these reactions by fluorescence and RLS spectros-copy described in this paper may be generally applicable to be usedto study other interesting chelating and coordination reactions ofditopic tetradentate ligands with metal ions and then with ditopic

monodentate ligands. The strategy used in the proposed analyticalmethods may also be applicable to be used for the spectroscopicdetermination of other targets based on the formation of binuclearcomplexes and supramolecular polymers.

Acknowledgement

This work is supported by the National Natural Science Founda-tion of China (NSFC Nos. 11275091, 10975069 and 11275090).

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