摘要:

ANALYST, MARCH 1993, VOL. 118 297 Determination of Trace Concentrations of Arsenic in Nickel-base Alloys by Electrothermal Atomic Absorption Spectrometry Suh-Jen Jane Tsai and Yea-Ling Bae De pa rtm en t o f Applied Chem is tr y, Pro viden ce University, Ta ich u ng Hsien, Taiwan A procedure for the determination of trace concentrations of arsenic in nickel-base alloys was developed. Solid samples of nickel-base alloys were decomposed with a mixture of hydrochloric acid and nitric acid (4 + I ) , the resulting solution was heated nearly to dryness and the residue was dissolved in about 2 ml of distilled, de-ionized water. Most of the excess of the acids was removed by repeating the heating and dissolution procedures. The final solutions were analysed by electrothermal atomic absorption spectrometry using a pyrolytic graphite platform in a pyrolytic graphite coated graphite tube at 193.7 nm.Various pre-treatment conditions, which included chemical modifiers, hydrazine and potassium iodide, were evaluated. Potassium iodide gave satisfactory results. The accuracy of the analytical results was checked using certified reference materials. The optimum conditions that gave the highest precision and accuracy of the results were established. Keywords: Arsenic determination; nickel-base alloy; electrothermal atomic absorption spectrometry Nickel-base superalloy is one of the most important materials in the aerospace industry. The presence of trace elements had deleterious effects on the mechanical and physical properties of high-temperature alloys. 1-3 The significance of close control of trace elements in nickel-base superalloys was reinforced in a detailed study by Ford in 1984.4 Trace elements present in either the raw materials or the finished castings were extremely damaging to the creep life and creep ductility of cast nickel-base alloys.Among the six trace elements studied, viz., Bi, Te, Se, Pb, Ag and Mg, Bi was the most detrimental in reducing the creep life. In contrast, Mg improved the castability of superalloys. Hence, accurate determinations of trace metals in superalloys have always been necessary. Lowe's report' also addressed the significance of the determination of trace elements in nickel-base alloys. A unique design of a high-temperature hollow-cathode source was proposed for the simultaneous determination of concomi- tant trace elements in nickel-base superalloys directly from drillings or small pieces.Trace amounts of As in solid samples have also been measured with a resistively heated furnace.3 There are only a few reports on this subject owing to the complexity of the matrix of superalloys. Matrix interferences in electrothermal atomic absorption spectrometry (ETA AS) were effectively reduced using an analytical system with a stabilized temperature platform furnace (STPF) .6,7 Therefore, it was considered worthwhile to develop an analytical procedure for the determination of trace elements in nickel-base superalloys with an STPF. Among the three popular atomization methods, namely flame, hydride generation and graphite furnace, the electrothermal method offers the highest sensitivity and lowest detection limits in most instances. The hydride generation technique coupled with AAS, inductively coupled plasma atomic emission spectrometry (ICP-AES), gas chromatography or molecular absorption spectrometry has been successfully applied to the determination of trace amounts of arsenic in both environ- mental and biological samples.8-13 However, the coexistence of more than 20 elements in a solution of superalloys prevented the adaptation of hydride generation AAS or AES to determine trace contents of superalloys without tedious separations.When an alkaline solution of a reductant, often NaBH4, was mixed with the acidic analyte solution, the sample solution solidified, which made the stripping of volatile metal hydrides almost impossible.The main problem in determining trace amounts of arsenic by ETAAS is matrix interferences. These were often elimin- ated by introducing effective chemical modifiers such as nickel compounds, palladium and magnesium nitrate. 14 Successful applications of modifiers have been reported in analyses of samples other than nickel-base superalloys15-17 and the reaction mechanisms involved have been studied. 1 ~ 1 9 This paper describes a selective and sensitive method for the determination of arsenic by ETAAS. The accuracy of the proposed method was evaluated with a certified reference material (CRM) of nickel-base alloy. Experimental Apparatus A Perkin-Elmer Model 1 lOOB atomic absorption spec- trometer fitted with an HGA-700 furnace and AS-70 auto- sampler was used.Integrated absorbances (peak area) values were used in measurements. Experimental parameters and peak profiles were recorded with an Epson EX-800 printer. An electrodeless discharge lamp (EDL) equipped with a Perkin-Elmer EDL power supply was used for the determin- ation of arsenic. New pyrolytic graphite coated graphite tubes (part No. B010-9322) and pyrolytic graphite platforms (part No. B010-9324) were used. Maximum power heating was used for the atomization step. A Barnstead Nanopure II system was employed for water purification. Reagents and Standards Concentrated hydrochloric acid and nitric acid were singly distilled acids obtained from Eastar Chemicals. Standard solutions of arsenic (H3As04 in HN03, 0.5 mol 1 - I ) and titanium (TIC& in HCI, 5 moll- 1) were prepared from Titrisol solutions (Merck).Standard solutions of Ga, In, V (prepared in 2% HN03) Ge and Ta (prepared in H20-trace HF) were products of Inorganic Ventures. Niobium (atomic absorption standard solution, in water), Z r (atomic absorption standard solution, in 5% HCI) and hydrazine hydrate solution (24% m/v) were products of Aldrich. Working solutions werc prepared from 1000 mg 1-1 stock solutions by serial dilution. Distilled, de-ionized water (DDW) prepared with a Barnstead Nanopure IT system was used in all experiments. The nickel-base alloy spectroscopic standard (SS) CRM 346A IN 100 Alloy was obtained from the Bureau of Analysed Samples. Purified grade argon (99.99%) was used as the purge gas during sample analysis.298 ANALYST, MARCH 1993, VOL.118 Procedures A 0.02000 g amount of sample was digested with a minimum volume of HCI-HN03 (4 + 1). After digestion, the sample solution was heated nearly to dryness and the residue was dissolved in a few millilitres of DDW. Most of the excess of the acids was removed by repeating the heating and dissolution procedures. The sample solutions were then treated with either of the following procedures: method A, the solution was diluted to 10 ml with 0.2% HN03; method B, 0.05 g of citric acid and 3.0 ml of hydrazine hydrate solution (15% d v ) were added and the sample solution was diluted to 10 ml with 0.2% HN03; method C, 1 ml of 5.0% m/v Kl solution was added before dilution with 0.2% HN03. The corresponding blank solutions were also prepared.Calibration solutions of 0.2-0.8 ng of arsenic were prepared by dilution of the working solutions with 0.2% HN03. These solutions were analysed by ETAAS. The concentration of arsenic was determined by injecting 2, 3, 5 or 10 p1 of the sample solution onto the platform in a pyrolytic graphite coated graphite tube. The optimum 'dry,' 'char' and 'atomize' HGA-700 programme developed in this laboratory was followed and the integrated areas of the absorption peaks were recorded. The recommended analy- tical conditions and the temperature programme are sum- marized in Table 1. Blanks were run rcgularly and their values were subtracted from the gross values to obtain the net values reported. Results and Discussion The optimum conditions for arsenic determinations are given in Table 1.Arsenic was determined by both the direct calibration method with standard arsenic solutions and the method of standard additions. Temperature Programmemeating Programme The background interferences can be partly eliminated by careful control of the temperature programmes. Fig. 1 shows the effect of charring temperature on the signal intensities. The absorbances of SS CRM 346A IN 100 Alloy and the arsenic standard solutions were monitored at an atomization temperature of 2300 "C. The signal intensities decreased Table 1 Optimum analytical conditions for arsenic determinations Light source Supply power Background corrector Lamp current Wavelength Slit Signal processing Integration time Internal gas Tubdsite Characteristic mass* Electrodeless discharge lamp 8W D2 lamp 8 mA 193.7 nm 0.7 nm Peak area 5.0s High-purity Ar (99.99%) Pyrolytic graphite coated 15.9 pg graphi te/platform Furnace conditions- Furnace Time/s Gas flow tcmpera- rate/ Read StcpNo.ture/"C Ramp Hold mlmin-1 on 1 120 10 20 300 - 2 1300 10 1 0 300 - 3 20 5 10 300 - 4 2300 0 5 0.0 0.0 5 2650 I 5 300 - 6 20 5 5 300 - * Mass of As giving a peak absorbance of 0.0044. gradually above 1300°C. This was due to the atomization of arsenic at any temperature higher than 1300°C. In order to minimize the volatilization losses of arsenic during the charring cycle, 1300°C was chosen as the charring tempera- turc. Fig. 2 shows the absorbances of arsenic as a function of the atomization temperature. The signal intensity of the SS CRM 346A IN 100 Alloy reached a plateau when the temperature increased to 2300 "C, whereas the absorbances of standard arsenic solutions decreased rapidly above this temperature.This indicated that some of the arsenic atoms were expelled from the graphite tube at higher temperatures. Interferences Potential interfering ions, including gallium, germanium, indium, niobium, tantalum, vanadium, zirconium and titan- ium, were studied. In order to elucidate the effects of foreign ions on the determination of arsenic, several sample solutions spiked with different metal ions were analysed. The relative absorbances were monitored with various concentrations of foreign ions up to 800 ppm. The relative absorbance (rel. abs.) was defined by the following equation: absorbance of (500 pg As + foreign ions) rel.abs. = absorbance of 500 pg As Table 2 summarizes the effects of metal concentrations on the relative absorbances. Zirconium caused a large enhance- ment of the absorption signals. The relative absorbance increased dramatically from 1.21 to 4.55 as the concentration increased from 40 to 800 ppm. As the zirconium enhancement varied linearly with concentration, the interference of zirco- 0.7 0.6 0.5 - 0.2 0.1 E 0 W W h 500 800 1000 1200 1400 1600 1800 2000 Charring temperature/"C Fig. 1 Absorbances of arsenic as a function of charring temperature at an atomization temperature of 2300 "C. A, 38.0 pg of SS CRM 346A 1N 100 Alloy and B, 680 pg of standard As n 0.5 0.4 1300'1 500 1800 2000 2200 2400 Atomization tern peratu rePC Fig.2 Absorbances of arsenic as a function of the atomization temperature at a charring temperature of 1300°C. A, 38.0 pg of SS CRM 346A IN 100 Allov and B. 680 DE of standard AsANALYST, MARCH 1993, VOL. 118 299 nium could be corrected by keeping the same concentration of interfering ion in both the standard solutions and the sample solutions as the calibration graphs were established. Tantalum, indium and vanadium gave a 30% enhancement of the absorption signals over the same concentration range. Therefore, the interferences from these three ions could be corrected similarly. The enhancement of the arsenic signals might be due to the stabilization of arsenic through the formation of less volatile compounds during the charring step, the non-specific absorption of the concomitant materials, e.g., the molecular absorption of metal chlorides, oxides and other salts which formed within the range 300-SOO0C,18 or the forma tion of thermos table in terme t a l k compounds and/or solid solutions. Titanium and niobium caused less than a 10% deviation in the relative absorbances. This indicated that the tolerance limits of these ions were up to 800 ppm. The effects of gallium and germanium on the absorption signals of analyte were interesting. Arsenic, gallium and germanium are highly volatile elements. These elements formed monoxides which were thermally stable only up to 600 "C even in the presence of a chemical modifier, such as nickel nitrate.18 The possible mechanisms involved in the atomization of arsenic in a graphite furnace were discussed by Styris et al.19 The gaseous species, As203, was decomposed thermally into As2, arsenic oxide, higher arsenic oxides and condensed-phase arsenic. Once the condensed-phase arsenic was formed it would polymerize into dimers, which would sublime, causing losses of analyte and resulting in low absorption signals of arsenic. The vaporization of the gaseous oxides was another major contributor to arsenic losses. Sufficient atomization would occur if the dissociation adsorption of the A s 0 or As2 and the desorption of the resulting arsenic proceeded successfully. In the presence of gallium there was less opportunity for arsenic to be polymerized as the latter was 'diluted' by gallium. Consequently, the relative absorbances were increased.The stabilization of arsenic could also be the result of the formation of thermostable intermetallic compounds similar to those, [Pd,As,O,], which had been proposed by Styris et al.19 The oxide Ga203 was first formed in a graphite tube and then reduced to Ga20, GaO and CO, which was released.18.20 As the concentration of gallium increased (above 400 pprn), the dissociation adsorption of arsenic oxide became less effective and more A s 0 was carried out of the graphite tube by the argon. This resulted in a smaller enhancement of the arsenic signals. Germanium when present in low concentrations (less than 160 ppm) had a negligible effect on the stabilization of arsenic atomization. As shown in Table 2, a slight depression of the relative absorbances was found. The formation of GeO was one of the reasons for the lower sensitivity in the determin- ation of germanium by ETAAS.?' The atomization of germanium was improved through the formation of thermally stable intermetallic compounds and germanates when chem- ical modifiers, Ni(N03)2 and Fe(N03)3, were employed.As Table 2 Effect of metal concentration on relative absorbance. Relative absorbance = absorbance of (500 pg As + foreign ions)/absorbance of 500 pg As. Results given are the averages of five determinations Concentration (ppm) Ele- ~ ment 40 80 160 240 320 400 480 600 680 800 Zr Ta In V Ti Nb Ga Ge 1.21 1.14 1.31 0.98 1.02 1.09 1.18 0.86 1.63 2.14 2.65 2.63 3.12 3.57 3.96 4.31 4.55 1.27 1.33 1.13 1.21 1.26 1.27 1.20 1.17 1.20 1.36 1.37 1.37 1.36 1.34 1.37 1.37 1.33 1.38 1.31 1.28 1.23 1.33 1.32 1.34 1.36 1.32 1.28 1.03 1.06 0.96 0.95 1.06 1.03 0.97 0.91 0.91 1.07 1.12 1.12 1.19 1.07 0.97 0.97 0.91 1.04 1.25 1.22 1.15 1.09 1.95 1.55 1.46 1.27 1.40 0.89 0.97 1.38 1.34 1.16 1.15 1.24 1.29 1.43 the ratio of the concentrations of analyte and interfering ion varied, different intermetallic compounds would be obtained.22 The relative absorbance increased dramatically to 1.38 as the concentration of germanium increased to 240 ppm.Less enhancement was observed as the concentration of metal increased. The formation of different intermetallic compounds could cause different degrees of improvement of the arsenic atomization. The erratic results with gallium and germanium could be mainly due to the high volatility of GaO and GeO and the formation of intermetallic compounds between arsenic and interfering ions.In this work, the atomic absorption of arsenic was moni- tored at 193.7 nm. The predominant molecular absorption wavelengths are 244.5 and 265.94 nm for GaO and GeO, respectively.2()x21 Although the molecular absorption of metal oxides could also contribute to the signal enhancement of the analyte, the contribution of molecular oxides could be negligible. However, the gaseous reactions involved in a graphite tube are very complicated and diverse mechanisms have been suggested. Further investigations are required in order to verify the mechanisms involved. Pre-treatment/Chemical Modifier The nickel-base alloy SS CRM 346A IN 100 Alloy for trace analysis, contains over 50% Ni, with the composition (values in mg g-1) C 1.5, Cr 100, Mo 30, Al55, Co 150, TI 50, V 10, Pb 0.022 and trace amounts of Bi, Ag, Se, Te, TI, Sb, As, Cd, Ga, Sn, Zn, Mg, Ca and In.The certified arsenic content was 51 t- 2 ppm. As sulfate caused a large depression of the arsenic signals and enhanced the interferences from alkali metal ions,15,23 sulfuric acid is not recommended for sample decomposition. After the solid sample had been decomposed completely with HCI-HN03 (4 + 1), sample solutions were prepared by the following pre-treatment procedures: in method A , the decomposed sample was diluted with 0.2% HN03 directly; in method B, 0.05 g of citric acid and 3.0 ml of hydrazine hydrate solution (15% m/v) were added before the solution was diluted; and in method C, 1 ml of potassium iodide solution (5.0% m/v) was added before dilution with Chemical modification techniques have been widely applied in trace analysis by ETAAS.The addition of chemical modifiers would result in either an increase in the volatility of unwanted elements or a decrease in the volatility of the atoms of interest. Nickel has often been employed as an effective chemical modifier and has been successfully applied to the determination of trace amounts of arsenic in environ- mental samples.14 Nickel is known to form thermally stable complexes, Ni(As03)z.Ni0, or other arsenides with arsenate ions.24 The addition of nickel stabilized the As atoms up to 1300-1500 "C. Hence the As atoms would not be released until the atomization step. In work by Stein et al.,15 trace concentrations of arsenic (about 10 pg I - I ) in potable, fresh and estuarine water were precisely and accurately determined by ETAAS with the addition of 0.05% of nickel.15 The concentration of the chemical modifier was often lo4 times higher than the analyte concentration.As there was over a 104-fold excess of nickel present in a sample of SS CRM 346A IN 100 Alloy, the sample solution was analysed directly after dilution with 0.2% HN03 as in method A. As listed in Table 3, the analytical results were 41.9 k 6.1 and 35.2 ? 1.3 ppm for the calibration graph method and the method of standard additions, respectively. Although the addition of nickel compounds prevented the charring losses of arsenic, serious interferences still existed. Different behaviours had been observed when trivalent and pentavalent arsenic were analysed by ETAAS .23 Standard arsenic solutions prepared from As203 or Na2HAsOj could be measured with a relative standard deviation of <5%, while 0.2% HN03.300 ANALYST, MARCH 1993, VOL.118 those prepared from As205 resulted in a relative standard deviation of 220%. This implied that better analytical results would be obtained if trivalent arsenic was measured in a graphite tube. Based on this prediction, a volume of reductant was added before the sample solutions were analysed. After the nickel-base alloys had been decomposed completely, both trivalent and pentavalent arsenic were possibly present in the sample solutions. Hydrazine hydrate had been successfully employed as an effective reductant in the determination of trace amounts of As, Sb and Sn in high-purity selenium.25 However, the addition of hydrazine did not improve the analytical results as given in Table 3.Potassium iodide also functions as an effective reductant to reduce AsV to AS"' in the hydride generation step.26 Therefore, the sample solution was treated with potassium iodide according to method C. A great improvement in the analytical results was found. Details are given in the following section. Quantitative Results Integrated absorbances are susceptible to the total number of atoms present in the light path and independent of the rate of atomization. Therefore, integrated absorbances were recorded instead of peak height absorbances. A calibration graph with a linear range from 0.2 to 0.8 ng was established [correlation coefficient ( R ) = 0.9994, -(intercept x K ) ( B ) = -0.0100, l/slope ( K ) = 4.1555; see Table 31.This work showed that the addition of potassium iodide resulted in more accurate and precise results for nickel-base alloys. The nickel-base alloy CRM was analysed to validate the accuracy of the proposed procedure. There was good agreement between the certified arsenic content and the results obtained with both the calibration graph method and the method of standard additions (Table 3). By adding various amounts of standard arsenic to sample solutions (0.4M.60 ng), a recovery of 99 k 3% was obtained. The detection limit was 0.30 ng g-1. Conclusions Trace amounts of arsenic in relatively complex samples, nickel-base superalloys, were successfully determined. A solid Table 3 Analytical paramctcrs and results of As determinations. Mean results of five determinations f standard deviation.The mass of standard arsenic added ranged from 0.4 to 0.6 ng. Calibration graphs: concentration = K x absorbance + B Linear rangehg R' K B 0.200-0.800 0.9994 4.1555 -0.0100 A nalytical results- As in SS CRM 346A IN 100 Alloy (ppm)* Mcthod A Method B Method C measurement 41.9 f 6.1 18.2 k 9.3 51.4 f 4.5 additions mcthod 3.5.2 f I .3 40.0 f 6.3 51 .0 -t 4.0 Direct Standard Recovery - - 99 f 3% Detection limit - - 0.30 ng gg' * Certified As content: 51 f 2%. sample was decomposed with HCI-HN03 (4 + 1) and after the removal of the excess of the acids, 1 ml of 5.0% m/v potassium iodide solution was added before dilution with 0.2% HN03. The resulting solutions were analysed by ETAAS.The addition of an effective reductant, potassium iodide, reduced AsV to As"' and gave reproducible results. The relatively high accuracy of the proposed methods was demonstrated by good agreement with the results obtained by the proposed method and with certified values. Financial support of this work by a grant from the National Science Council of the Republic of China is gratefully acknowledged. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 References Andrews, D. G., and Headridgc, J. B., Analyst, 1977,102,436. Backman. S . , and Karlsson, R. W., Analyst, 1979, 104, 1017. Headridge, J. B., and Nicholson, R. A., Analyst, 1982, 107, 1200. Ford, D. A., Met. Technol., 1984, 11, 438.Lowe, D. S . , AnalyJt, 1985, 110, 583. Sturgeon, R. E.. Fresenius' J. Anal. Chem., 1990, 337, 538. L'vov, B. V., Anal. Chem.. 1991, 63, 924A. Narsito, Agterdenbos, J., and Santosa. S. J.. Anal. Chim. Acta, 1990, 237, 189. Van Elteren. J. T., Gruter, G. J. M . , Das, H. A., and Brinkman, U. A. Th., Int. J. Environ. Anal. Clzem., 1990, 43, 41. Van Elteren, J. T., Haselager, N. G., Das, H. A., de Ligny, C. L., and Agterdenbos. J.. Anal. Chim. Acta, 1991, 252, 89. Schramcl, P., and Xu, L.-Q.. Freseniur' J. Anal. Chem., 1991, 340, 41. Cutter, L. S . , Cutter. G. A., and San Dicgo-McGlone, M. L. C., Anal. Chern., 1991, 63, 1138. Sanz. J., Gallarta, F . , and Galban, J . , Anal. Chim. Acta, 1991, 255, 113. Schlemmer, G., and Wclz, B.. Spectrochim. Acta, Part B , 1986, 41, 1157. Stein, V. B., Canelli, E., and Richards, A. H . , A f . Spectrosc., 1980, 1, 133. Bettinelli, M.. Pastorelli, N., and Baroni, U., Anal. Chim. Acta, 1986, 185, 109. Bozsai. G., Schlemmer, G., and Grobenski, Z . . Talanta, 1990, 37, 545. Volynsky, A., Tikhomirov, S . . and Elagin, A., Analyst, 1991, 116, 145. Styris, D. L.. Prell, L. J., and Redfield, D. A., Anal. Chem., 1991, 63, 503. Shan, X., Yuan, Z . , and Ni, Z.. Anal. Chem., 1985,57,857. Kolb, A., Muller-Vogt, G., Wendl, W., and Stobel, W., Spectrochim. Acta, Part B , 1987, 42, 951. Xuan. W.-K., and Li. J.-G., Spectroclzim. Acta, Part B , 1990, 45, 669. Chakraborti. D., De Jonghe, W. and Adams, F., Anal. Chim. Actu, 1980, 119, 331. Koreckova, J., Frech, W., Lundberg, E., Pcrsson, J.-A.. and Cedergren, A., Anal. Chim. Actu, 1981, 130, 267. Ivanova, E . , Vracheva, N . , Havezov, l . , and Jordanov, N . , Fresenius' 2. Anal. Chem., 1988, 330, 516. Donaldson, E. M.. and Leaver, M. E., Talanta, 1988. 35, 297. Paper 2102013K Received April 21, 1992 Accepted June 1 I , 1992

ISSN:0003-2654    

DOI:10.1039/AN9931800297

出版商:RSC    

年代:1993

数据来源: RSC

摘要:

ANALYST. MARCH 1993, VOL. 118 301 Flame Atomic Absorption Spectrometric Determination of Magnesium in Nickel-base Alloys Suh-Jen Jane Tsai and Yea-Ling Bae Department o f Applied Chemistry, Pro viden ce University, Ta ic h u ng Hsie n, Taiwan Flame atomic absorption spectrometry (FAAS) was employed for the determination of magnesium with wavelength 285.4 nm, slit-width 0.7 nm and air-acetylene flame (flow rates 2 and 15.5 I min-1, respectively). A pre-treatment procedure for the determination of trace concentrations of magnesium in nickel-base alloys was developed. Matrix interferences could be effectively eliminated by the addition of both ethylenedi- aminetetraacetic acid and SrCI2. The accuracy of the results was checked with certified reference materials of nickel-base alloys.For IN100 and Inconel alloy 718 with a certified magnesium content of 130 k 9 and a reference value of 12 k 5 ppm, the procedure gave values of 130 k 3 and 7 k 1 ppm, respectively. The detection limit was 0.50 ng g-1 and the recovery ranged from 97 f 4 t o 104 k 2%. Keywords: Magnesium determination; nickel-base alloy; flame atomic absorption spectrometry The determination of trace amounts of magnesium in nickel- base superalloys1 and environmental samples2 has always been a challenge. Flame atomic absorption spectrometry (FAAS) gives low detection limits in the determination of a few elements. In fact, magnesium is one of the most sensitive elements that can be determincd by FAAS.3 However, it is subject to interferences from a number of anions, cations and detergents.47 The interference of silicate was eliminated by the addition of releasing agents such as La,s and most of the interferences from cations can be eliminated by strontium chloride.4 Among the various types of flames, the air- acetylene flame provided the most suitable atom reservoir for magnesium determinations, because there are less interfer- ences from foreign ions.”lO The merit of the method proposed here is that trace amounts of magnesium in a complex matrix can be determined without tedious solvent extractions.The accuracy of the method was evaluated with certified reference materials of nickel-base alloys, namely INlOO and Inconel alloy 718. The good accuracy and precision of the results showed the high reliability of this method when applied to the analysis of nickel-base alloys.Experimental Apparatus A Perkin-Elmer Model 2380 atomic absorption spectrometer equipped with a flow spoiler and a hollow cathode lamp operated at 8 mA was used for magnesium determinations. The operating conditions were wavelength 285.4 nm, slit- width 0.7 nm, and air-acetylene flame (flow rates 2 and 15.5 I min- I , respectively). A Barnstead Nanopure TI system was employed for water purification. Reagents and Standards Concentrated hydrochloric acid and nitric acid were singly distilled acids from Eastar Chemical. A standard solution of magnesium (1 .000 k 0.002 g MgClz in 6% HCI) was prepared from Titrisol solutions (Merck). Strontium chloride hexahy- drate, SrC12-6H20, was obtained from Merck, sodium ethyl- enediaminetetraacetate (EDTA) from RDH and lanthanum chloride heptahydrate, LaCI3-7H20 (99.9% ACS reagent), from Aldrich.Working solutions were prepared from 1000 mg 1-1 stock solutions by serial dilution. The certified reference materials of nickel-base alloys, INlOO (SS-CRM No. 346A) and Inconel alloy 718 (BS 718 A) were obtained from the Bureau of Analysed Samples and Brammer Standard, respectively. Purified grade argon (99.99%) was used as the purge gas during sample analysis. Procedures A precisely weighed amount (about 0.01 g) of sample was digested with a minimum volume of HCI-HN03 (4 + 1). The solution was heated mildly until the decomposition process was completed. The sample solution was then treated accord- ing to one of the following procedures: method A, the sample solution was diluted to 10 ml with distilled, de-ionized water; method B, 1 ml of lanthanum solution (5.0% m/v) was added to the sample solution before dilution; method C, the sample solution was prepared similarly, but Sr solution (5.0% m/v) and EDTA solution (4.0% m/v) were added before dilution.In order to ascertain the optimum concentration of Sr and EDTA, a series of sample solutions that contained different amounts of Sr (0.20, 0.30, 0.40, 0.50, 0.80, 1 .O, 2.5 and 5.0% m/v) and EDTA (0.12, 0.24, 0.40, 0.80 and 2.4% m/v) were prepared. The corresponding blank solutions were also prepared. Results and Discussion Trace amounts of magnesium in nickel-base alloys were determined by FAAS using the given operating parameters and the results are given in Table 1.The certified reference materials I N 1 0 and Inconel alloy 718 were employed for evaluating the accuracy of the proposed method. The compo- Table 1 Analytical parameters and results of Mg determinations Calibration graphs:” concentration = K x absorbance + R Linear range (ppm) R2 K B 0.050-0.30 0.9986 1.5859 -0.0063 Analytical results?- Mg found (ppm) Mg content (ppm) Method A Method B Method C IN I00 130 ? 9 ND 80+3 1 3 0 t 3 Inconel alloy 7 1 8 1 2 f S ND - 7 t l Detection limit - - - 0.SOngg-’ * Light source, hollow cathode lamp; wavelength, 285.4 nm; slit-width, 0.7 nm; flame, air-acetylene, oxidizing (lean, blue); R2 = correlation coefficient; K = l/slope; B = -(intercept x K ) . t. Results of four determinations; ND = not detectable; detection limit = 30 of blanks ( n = 7).302 ANALYST, MARCH 1993, VOL.118 sition of IN100 was (values in mg g- 1 ) C 1.5, Cr 100, Mo 30, A1 55, Co 150, Ti 50, V 10, Pb 0.022 and trace amounts of Bi, Ag, Se, Te, TI, Sb, As, Cd, Ga, Sn, Zn, Ca and In. The certified magnesium content was 130 k 9 ppm. The composition of Inconel alloy 718 was (values in mg g-1; numbers in parentheses are not certified but are provided for information only)C0.36,Si1.2,Mo30.6,Fe192.1,Mn0.8,Cu0.6,Al5.7, Ti 10.2, P 0.07, Ni 520, Co 3.2, Nb 51.9, S 0.01, Cr 181.9, B 0.046, V (0.3), Sn (0.04), W (0.8), V (0.3). A reference value of 12 rt 5 ppm Mg was not certified, but was for information. After solid samples had been decomposed with HCl-HN03 (4 + 1), the sample solutions were prepared according to methods A , B and C above.It was not possible to detect any absorption signal of Mg atoms when sample solutions of nickel-base alloys were analysed directly after decomposition according to method A. This indicated that there were serious interferences from the matrix. Several cations, anions and detergents interfere in the determination of magnesium by FAAS.4-6 For example, aluminium interfered through the reaction631 1 MgO + A1203 + MgA1204 Once the thermally stable magnesium aluminate spinel MgA1204 has been formed, it would be extremely difficult for the atomization process to proceed. The addition of lan- thanum would decrease the silicate interference.* Although the addition of 1 ml of lanthanum solution (5.0% m/v) as in method B altered the result from undetectable to 80 k 3 pprn of magnesium, further improvement was still required.Strontium chloride eliminated most of the interferences from cations except those due to Fellr, Crlll and Ti1".4 Strontium could function as a releasing agent through the reaction Sr + MgO .+ SrO + Mg The reagent EDTA is known to chelate with many metal ions, including magnesium ions. The refractory compounds of magnesium would be greatly reduced through chelation. The experimental results showed that the addition of both stron- tium and EDTA solutions had considerable effects on the analysis. In fact, method C gave the most satisfactory results. In order to ascertain the optimum conditions for the pre-treatment of nickel-base alloys, serial analyses were performed with different strontium concentrations (0.20- 2.5%) and EDTA concentrations (0.12-2.4%).The best results for TNlOO were obtained with 0.24% m/v EDTA and 0.30 m h strontium. For Inconel alloy 718, the optimum concentrations of EDTA and Sr in the sample solutions were 0.4 and 0.5% m/v, respectively. For IN100 with a certified magnesium content of 130 rt 9 pprn the proposed method gave 130 -t- 3 ppm and for Inconel alloy 718 with a reference value of 12 k 5 pprn this method gave 7 k 1 ppm. The proposed method gave a detection limit of 0.50 ng 8-1 and the recovery ranged from 97 k 4 to 104 rt 2% (seven determinations). This shows that trace amounts of magnesium in nickel-base alloys can be determined accurately and precisely with the proposed FAAS procedure. Financial support of this work by a grant from the National Science Council of the Republic of China is gratefully acknowledged. 1 2 3 4 5 6 7 8 9 10 11 References Lowc, D. S., Analyst, 1985, 110, 583. Pal, T., Jana, N. R., and Das, P. K., Analyst, 1992, 117, 791. Gimeno Adelantado, J . V., Perk Martinez, V., Pastor Garcia, A., and Bosch Reig, F., Talanta, 1991. 38, 959. Ramakrishna, T. V., Robinson, J. W., and West, P. W., Anal. Chim. Acta, 1966, 36, 57. Firman, R. J., Spectrochim. Acta. 1965,21, 341. Halls, D. J . , and Townshcnd, A., Anal. Chim. Acta, 1966, 36, 278. Ramakrishna, T. V., West, P. W., and Robinson. J . W., Anal. Chim. Acta, 1968, 40, 347. Stojanovic, D. Dj.. Vajgand, V. J . , and Nikolic, S. D., Spectrochim. Acta, Part B, 1987, 42, 915. Andrew, T. R., and Nichols, P. N. R., Analyst, 1967. 92. 156. Shaw. F., and Ottaway, J . M.. Analyst, 1975, 100. 217. Harrison, W. W.. and Wadlin, W. H., Anal. Chem., 1969. 41, 374. Paper 2/03081 K Received April 21, 1992 Accepted June I I , I992

ISSN:0003-2654    

DOI:10.1039/AN9931800301

出版商:RSC    

年代:1993

数据来源: RSC

摘要:

ANALYST, MARCH 1993, VOL. 118 303 Determination of Trace Amounts of Aluminium in Natural Waters by Solid-phase Spectrofluorimetry Jose Luis Vilchez, Alberto Navalon, Ramiro Avidad, Trinidad Garcia-Lopez and Luis Ferm in Ca pitan-Val hey* Department of Analytical Chemistry, University of Granada, E- 18071 Granada, Spain A spectrofluorimetric method for the determination of trace amounts of aluminium was developed, based on solid-phase spectrofluorimetry. Aluminium reacted with salicylidene-o-aminophenol t o form a fluorescent complex that was adsorbed on a dextran-type cation-exchange gel. The fluorescence of the gel, packed in a 1 mm silica cell, was measured directly with use of a solid-surface attachment. The applicable concentration range was from 0.20 to 14.00 pg 1-1, with a relative standard deviation of 1.0% and a detection limit of 0.02 pg 1-1.The method was applied to the determination of aluminium in natural waters. The method is more sensitive and selective than that based on salicylidene-o-aminophenol alone. Keywords: Salicylidene-o-aminophenol; aluminium determination; solid-phase spectro fluorimetry; natural water During the last decade, there has been an increased interest in the biological importance of aluminium because of evidence for the systemic toxicity of the element and the development of accurate analytical techniques. Aluminium is used in building and vehicle construction, and in the manufacture of paint, electrical equipment, packaging containers and cooking utensils. It is used therapeutically as an antacid, in drinking-water purification and as an antiperspir- ant.Aluminium toxicity has been linked to encephalopathy,'-3 osteomalacy and osteodistrophy,4.~ anaemia,"7 gastrointesti- nal symptoms8 and possible cardiotoxicityg features. Analyses for aluminium are mainly used to determine the blood and urine levels in individuals who work with aluminium and in patients subjected to haemodialysisl() or receiving total parenteral nutrition. 11 Monitoring of patients on haemodialysis is critical. Sequen- tial determination of aluminium in serum is required and even the water used in dialysis must be checked to ensure that levels of aluminium remain low.12 Aluminium determination by fluorescence measurements has been widely studied, and numerous methods have been proposed.13 One of the best known involves salicylidene-o- aminophenol as a reagent.13-16 This method yields a sensitive and relatively selective procedure, although there are several disadvantages regarding practical applications. 1.5 Solid-phase spectrofluorimetry (SPF) combines the measurement of solid-surface fluorescence with the use o€ a solid support (e.g., an ion-exchange gel) to preconcentrate the analyte, which has been rendered fluorescent by the use of an appropriate reagent. This approach has been found to be useful for the analysis of very dilute solutions, such as water. 17-22 In this paper, a method for the determination of trace amounts of aluminium by SPF is described, which was applied satisfactorily to the determination of aluminium in natural waters.By using this methodology, a higher sensitivity, a lower detection limit and a lower interference level than in solution are obtained. Experimental Reagents All the reagcnts used were of analytical-reagent grade unless stated otherwise. * To whom correspondcncc should be addressed. Sephadex CM C-25 cation-exchange gel (Pharmacia Fine Chemicals, Uppsala, Sweden) was used in the sodium form and without pre-treatment in order to avoid contamination. Salicylidene-o-aminoptienol (SOA Ph) . This was synthe- sized as described earlier19 and used as a 1.0 X 10-3 mol 1 - 1 solution in acetone, which was stable for at least 1 week. Solutions of lower concentrations were prepared fresh each day. Standard aluminium(rir) stock solution, 1 .O mg ml- 1 . Prepared from A1(N03)3-9H20 (Merck, Darmstadt, Ger- many) in 0.1 mol 1-1 nitric acid and standardized by titrimetry with ethylenediaminetetraacetic acid (EDTA) (Xylenol Orange as indicator).Working solutions were prepared by appropriate dilutions with doubly distilled water. Buffer solutions. Solutions of the required pH were prepared from 1.0 mol 1 - 1 sodium acetate (Merck) solution and 1.0 rnol 1-1 acetic acid (Merck). Apparatus All spectrofluorimetric measurements were performed with a Perkin-Elmer LS 5 luminescence spectrometer (Norwalk, CT, USA), equipped with a xenon discharge lamp (9.9 W) pulsed at line frequency, Monk-Gillieson F/3 monochromators, a Rhodamine 101 counter to correct the excitation spectra, a Hamamatsu R928 photomultiplier, a Houston Omnigraphic x-y recorder (Houston Instruments, Houston, TX, USA), a variable-angle solid-surface accessory, designed and construc- ted in-house (see Fig.l),23 and a Braun Melsungen Thermo- mix 1441 thermostat (B. Braun, Germany). In order to compare all the spectrofluorimetric measurements and ensure reproducible experimental conditions, the LS 5 spectrometer was checked daily with a sample of the fluorescent polymer standard p-terphenyl (1.0 x 10-7 mol I - I ) having a relative fluorescence intensity of 90% at he, = 340 nm, he, = 295 nm; the slit-widths were 2.5 and 2.5 nin, and the sensitivity factor was 0.594. The LS 5 spectrometer was interfaced with an IBM PS/2 30-286 microcomputer, with RS 232C connections for spectral acquisition and subsequent calculation of the excitation- emission matrices.24 The contour plots in the excitation- emission plane were produced by linking points of equal fluorescence intensity.A Canon RJ-300 printer (Canon, Tokyo, Japan) was used for graphical representation. A Crison 501 digital pH meter (Crison Instruments, Barcelona, Spain) with a combined glass-saturated calomel electrode and an Agitaser 2000 rotating agitator (Tecnotrans, Barcelona, Spain) were also used.304 ANALYST, MARCH 1993, VOL. 118 f hem I 31 5 135 225 r I L Fig. 1 Variable-angle solid-surface accessory Fluorescence Measurements The measured relative fluorescence intensity (RFI) of the gel beads, containing the fluorescence products and packed into a 1 mm silica cell, was the diffuse transmitted fluorescence emitted from the gel at the unirradiated face of the cell.The optimum angle between the cell plane and the excitation beam was 45" in all instances.23 Procedures Basic procedure A 500 ml water sample containing 0.2&14.00 pg 1 - 1 of Al"' was transferred into a 1 1 polyethylene bottle, and 2.5 ml of 1.0 mol 1-1 acetic acid-acetate buffer (pH 5.80), 2.5 ml of 1.0 X 10-3 mol 1-1 SOAPh and 100 mg of Sephadex CM C-25 gel were added. The mixture was shaken mechanically for 10 min. Afterwards, the gel beads were collected by filtration under suction and, with the aid of a pipette, were packed into a 1 mm cell, together with a small volume of the filtrate. A blank solution containing all the reagents except aluminium was prepared and treated in the same way as described for the sample. The fluorescence intensities (20.0 5 0.5"C) of the sample and blank were always measured 5 min after loading the samples at A,,, = 508 nm, with A,, = 410 nm.A calibration graph was established in the same way, with use of aluminium solutions of known concentration. Procedure for natural waters The above-mentioned reagents were added to a volume of natural water sample containing an adequate amount of All1', levelled off at 500 ml with doubly distilled water and placed in a 1 1 polyethylene bottle. The subsequent steps were as in the basic procedure. The calibration graph method was used for calibration purposes. Sample treatment Natural waters (preserved by addition of 0.25 ml of concen- trated nitric acid per litre of sample) were passed through a 600 W 350 I I --- 450 500 550 Em ission/n m 600 Fig.2 ( a ) Projected three-dimensional spectrum of the aluminium- SOAPh complex fixed on Sephadcx CM C-25 gel in an acetic acid-acetate buffcr (pH 5.80). Increments in excitation wavelengths were 2 nm for each emission scan and scan speed was 240 nm min-1. (b) Contour plot of the excitation-emission matrix of the aluminium- SOAPh complcx fixed on Sephadex CM C-25 gel in an acetic acid-acetate buffer (pH 5.80). The contours join points showing the same relative fluorescence intensity filter-paper with a pore size of 0.45 pm (Millipore, Milford, MA, USA) and the filtrates were collected in polyethylene containers that had been cleaned carefully with nitric acid. The samples were stored at 4 "C until analysis. Analyses were performed with the least possible delay.The usual precautions were taken to avoid contamination .25 Results and Discussion Spectral Characteristics The reagent SOAPh reacts with All1', originating in solution as a 1 : 1 fluorescent chelate at slightly acidic pH (approximately 6). 1 6 1 6 In the prescence of Sephadex cation-exchange gel, the complex, probably cationic, is adsorbed on the gel, as the complex is not adsorbed on anion-exchange gels. A CM C-25 dextran-type gel was selected as it was found to have a lower background fluorescence. In Fig. 2(a), the three-dimensional spectrum of the alumi- nium-SOAPh complex adsorbed on the gel (after the contri- bution of the blank has been subtracted) is represented as anANALYST, MARCH 1993, VOL. 118 305 isometric projection, where the emission spectra at stepped increments of the excitation wavelength have been recorded and plotted.Computer software allows the spectrum to be examined from a high or low excitation wavelength. In Fig. 2(b), the three-dimensional spectrum has been transformed into a contour plot in the excitation-emission plane, in order to ascertain both excitation and emission maxima. The peak wavelengths in the excitation spectra of the SOAPh-AI"' system are identical for the immobilized and solvated systems (410 nm). The maxima of the emission spectra for the two systems differ, being located at 520 nm in solution and at 508 nm in the gel phase. The modification of the features of the fluorescence spectra was considered to be a result of the modification of the surrounding environment of the complex in the gel phase with respect to solution. In addition, it was observed that a decrease in the excitation slit-width (Slitcx) or an increase in the emission slit-width (Slitem) increased the fluorescence signal.A similar effect has been reported by other workers.26 For optimum excitation and emission, slit-widths of 2.5 nm were selected in both instances. From a study of the half-life time of the excited state of the complex in the solid phase at different temperatures, it was concluded that the luminescence process was fluorescence (T< 5 x 10-6 s). Optimization of Variables p H dependence First, a buffer solution from those proposed in the literature was chosen on this system in solution. The ammonium acetate-hydrochloric acid buffer16 cannot be used, because it alters the gel.The sodium acetate-acetic acid buffer solution was found to afford the best results. The optimum pH value for the formation and fixation of the species falls in the narrow range 5.50-6.00. At pH <3.5 or >7.5 the complex is not formed and/or not fixed on the gel (Fig. 3). The fluorescence is independent of ionic strength, adjusted with the buffer solution, NaCl or NaC104, up to 0.01 moll-'. For higher values, the fluorescence emission decreases according to the equation: RFT = 8.2 X p-1'2 (RFI = relative fluorescence intensity; p = ionic strength; r = 0.995). This effect can be attributed to the competition from other ions in the ion-exchange equilibrium .27 SOA Ph concentration The optimum SOAPh concentration for maximum fluores- cence intensity was 5.0 x 10-6 mol 1-1 for an SOAPh-to- aluminium ratio of about 11 : 1.At higher SOAPh concentra- tions, however, the quenching effect observed in solution appeared more pronounced in the gel phase, probably owing to the re-absorption effect of the solid matrix (SOAPh fixed on Sephadex) .2X 3 4 5 6 7 8 PH Fig. 3 Influence of H on relative fluorescence intensity. [SOAPh], 2.0 x 10-5 mol I - l ; r.411i1], 1.85 x 10-6 mol 1-1; acetic acid-acetate buffer solution; Sephadex CM C-25, 100 mg; sample, 500 ml; stirring time, 10 min; A,,, 410 nm; kern. 508 nm; and T , 20.0 k 0.5 "C Influence of temperature The effect of temperature on the ion-exchange process and hence, on the fluorescence emission, was studied. The ion-exchange process was independent of temperature in the range 0-4OoC, with measurement of RFI at 20.0 k 0.5"C.In the latter instance, the fixation of species was carried out at room temperature. On the other hand, RFI decreased when the temperature of the system increased, the effect being totally irreversible. The decrease of RFT was 0.4% at 1O"C, 0.8% at 20°C, 12.2% at 30"C, 43.1% at 40°C and 78.5% at 50 "C. All RFI measurements reported here were performed at 20.0 k 0.5"C. Other experimental conditions The stirring times necessary for maximum RFI development were 10, 15, 20 and 25 min for 500, 1000, 1500 and 2000 ml samples, respectively. As the use of a large amount of the gel lowered the RFI, only the amount required to fill the cell and facilitate handling, i.e., 100 mg, was used in all the measure- ments.With regard to the stability of the fixed complex, the RFI, after an initial increase during 2 min of 10% , remained constant for at least 3 h. The order of addition of reagents did not affect the results obtained. The order used was aluminium, buffer, SOAPh and gel. Effect of sample volume on sensitivity In previous papers,17-22 it was mentioned that one of the main advantages of SPF methods is the potential increase in sensitivity with increase in the sample volume taken for analysis. This effect can be assessed by measuring the RFl of Sephadex equilibrated with different volumes of solutions containing the same concentration of AI"' and proportional amounts of the other reagents. Plots of RFI versus sample volume show an increase in fluorescence signal with sample volume, tending asymptotic- ally to a constant RFI value above a certain volume.The shape of the graphs suggests a Langmuir-type isotherm, as is observed in some ion-exchange spectrophotometric studies.29 Stoichiometry of the Complex Fixed on the Gel The stoichiometry of the SOAPh-AI"' complex fixed on Sephadex CM C-25 gel was studied by continuous-variation and molar-ratio methods. In both instances, the ligand-to- metal ratio found was 1 : 1. This species is identical with the complex reported by Dagnall et al.15 and Morishige16 in solution. The cationic nature of the complex could justify its fixation on the gel. In this study the tendency of the gel to sorb complexes with a large number of ligands was not observed.This occurrence has been described by several workers.3(&-32 Calibration and Precision The calibration graphs for samples treated according to the procedure described above are linear for the concentration ranges 0.20-14.00 pg 1-1 for 500 ml, 0.20-12.0 pg 1-1 for 1000 ml and 0.10-10.0 pg 1-1 for 1500 and 2000 ml sample volumes. The analytical parameters are summarized in Table 1. The reproducibility of the proposed method and of the packing of the gel in the 1 mm cell was determined. The precision was measured for an aluminium concentration of 1.00 pg 1-1 by performing ten independent determinations. The relative standard deviations (RSDs) (p = 0.05, n = 10) were 1.0, 0.9, 0.8 and 0.8% for 500, 1000, 1500 and 2000 ml samples, respectively. The precision (RSD) of the packing operation, calculated from ten measurements, was 0.9% for the aluminium-SOAPh complex fixed on the gel, 0.9% €or the gel blank (gel with SOAPh and buffer) and 0.8% for the gel only. It appears, therefore, that one of the main factors306 ANALYST, MARCH 1993, VOL.118 Table 1 Analytical parameters Sample volume/ml Parameter 500 1000 1500 2000 Slope 4.68 6.65 8.56 10.34 Linear dynamic Correlation Detection limit/ Determination RSD* (%) I .0 0.9 0.8 0.8 Intercept 0.1 0.3 0.2 0.2 range/pg I- 1 0.20-14.00 0.20-12.00 0.10-10.00 0.10-10.00 coefficient 0.999 0.998 0.998 0.998 Pg 1- 0.022 0.016 0.014 0.012 limit/pg 1-1 0.075 0.053 0.047 0.039 * RSD = relative standard deviation. Table 2 Methods for the spectrofluorimetric determination of aluminium Detection limit"/ Reagent I%-' SOAPh 0.27 Morin 0.27 Salicylidene-2-amino-3-hydroxyfluorene 0.2 6-(4-Methylsalicylideneamino)-rn-cresol 0.2 N-Salicylidene-2-hydroxy-4-carboxyaniline 0.2 Morint 0.1 2,6-Bis[(o-hydroxy)phenyliminomethyl]- l-hydroxybenzene 0.1 2,4-Dihydroxybenzaldehyde semicarbazone 0.08 N-Salicylidene-2-hydroxy-5-sulfoaniline 0.08 MorinS 0.02 SOAPh$ 0.02 * Or minimum concentration used for calibration.$ Ion-exchange spectrofluorimetry . Extraction procedure. Ref. 14 35 36 16 37 38 39 40 37 18 This work affecting the reproducibility is the packing of the gel. Centrifugation of the gel when packed in the cell did not lead to improved precision. Sensitivity and Detection Limit The sensitivity in SPF methods can be enhanced by increasing the volume of the sample.In practice, this increase can be calculated from the slope of the calibration graphs. The calculated values of the sensitivity ratio (S) for the samples analysed in this study are: = 2.21, S1soo/5oo = 1.83 and S1(H)oIsoO = 1.42, where the subscripts represent the sample volumes (ml). The non-linear dependence of sensitivity versus sample volume can be attributed to the decrease in the distribution coefficient with analyte concentration, as is usual in a non-linear isotherm. The increase in sensitivity obtained with the proposed method is substantial, particularly with respect to solution methods that involve use of SOAPh as a reagent. In order to compare this increase in sensitivity, the calibration graph for the determination of Al"' with SOAPh in solution, was established, i.e., for the method of Dagnall et aZ.14 Under our experimental conditions, the equation for the calibration graph was RFI = 0.16[Al"'] ( r = 0.999), the ratio of the slopes being 29 : 1.The IUPAC detection limits33 and the limits of determina- tion34 were calculated for 500, 1000, 1500 and 2000 ml sample volumes. The results are reported in Table 1. The proposed method was compared with methods de- scribed in the literature for the spectrofluorimetric determina- tion of aluminium. For comparison purposes those methods Table 3 Effect of foreign ions on the determination of 1.00 pg I-' of aluminium Foreign ion o r species Tolerance level/pg I - I Table 4 Determination of aluminium in natural waters Water Amount found*/pg 1-1 156 t 2 37.6 If: 0.3 19.0 k 0.1 17.2 k 0.2 5.12 k 0.08 14.5 k 0.2 Tap water (Granada City) Raw water (Genil River) Raw water (Quentar Dam) Raw water (Aguas Blancas River) Mineral water (Lanjaron) Mineral water (Ortigosa del Monte) * Average value k standard deviation of three determinations.Table 5 Recovery study of aluminium in natural waters Amount added1 Water* M - l - Tap water (Granada City)/lO mlS 1 . 00 2.00 3.00 - Raw water (Genil River)/SO mlS 1 .oo 2.00 3.00 Raw water - (Quentar Dam)/100 mlS 1 .OO 2.00 3.00 - Raw water (Aguas Blancas River)/ 1 .00 100 ml$ 2.00 3.00 (Lanjaron)/250 mlS 1 .OO Mineral water - 2.00 3.00 Mineral water - (Ortigosa del Monte)/ 1 .oo 100 ml$ 2.00 3.00 * Final volume 500 ml in all instances. Amount foundt/ 3.12 4.10 5.20 6.10 3.76 4.74 5.70 6.68 3.80 4.90 5.75 6.92 3.44 4.48 5.40 6.50 2.56 3.52 4.54 5.60 2.90 3.96 4.85 5.80 % - ' t Data are the average values of three determinations.3 Initial sample volume in each instance. Recovery (Yo) - 99.5 101.6 99.7 99.6 99.0 98.8 102.1 99.1 101.8 100.9 99.3 100.9 98.9 99.6 100.7 101.5 99.0 98.3 - - - - - that were considered to be among the most sensitive reported to date were selected (Table 2). Effect of Foreign Ions A systematic study was carried out on the effect of foreign ions on the determination of All1' at the 1.00 pg 1 - 1 level. A 10 mg 1 - 1 level of potentially interfering ions was tested first, and if interference occurred the ratio was reduced progressively until interference ceased. Higher ratios were not tested. Tolerance was defined as the amount of foreign ion that produced an error not exceeding +5% in the determination of the analyte.The results are summarized in Table 3. Interference levels were lower than those found in solution methods.1416 On the other hand, the proposed method is more selective than those involving methods based on morin. 183.38ANALYST, MARCH 1993, VOL. 138 307 Determination of Aluminium in Natural Waters The method was applied to the determination of aluminium in water samples. Tap water from Granada, which is treated with aluminium compounds for flocculation purposes, raw water from Granada supplies to the city reservoirs (Quentar Dam, Genil River and Aguas Blancas River), and mineral water from Lanjaron (Granada) and Ortigosa del Monte (Segovia) natural springs were selected. The volume of water used for the analysis depended on the aluminium content: 10 ml of tap water; 50 ml of raw Genil River water; 100 ml of raw Quentar Dam water, raw Aguas Blancas River water and Ortigosa del Monte spring water; and 250 ml of Lanjaron spring water.The analysis was carried out by the calibration graph method. The average aluminium content (based on three determina- tions) in the samples studied is listed in Table 4. The aluminium content found in tap water was higher than that in raw waters. This is related to the use of commercial aluminium salts in the water-treatment plant, as previously stated. In order to check the accuracy of the proposed method a recovery study was carried out on the waters mentioned above. For this, various amounts of aluminium were added, and the percentage recovery was determined.Table 5 shows the results obtained for all the water samples. This study was funded by the Direccion General de Investigac- ion Cientifica y Ticnica (DGTCYT) del Ministerio de Educac- ion y Ciencia (Spain) (Project No. PS88-0101). 1 2 3 4 5 6 7 8 9 10 11 12 References Alfrey, A. C., Legendre, G . R., and Kaehny, W. D . , New Engl. J . Med., 1976, 294, 184. Dunea, G . , and Mahurkan. S. D., Ann. Intern. Med., 1978,88, 502. Davism, A. M., Oli, H., and Walker, G. S . , Lancet, 1982, 2, 785. Wills, H. R., Clin. Chem. (Winston-Salem, N.C.), 1985, 31, 5 . Gardiner, P. E., and Ottaway, J . M., Anal. Chim. Acta, 1981. 128, 57. Fernandez Soto, I., Allende, M. T., and Diaz de GreAi, M. C., Nefrologia, 1986, 6, 71.Drueke, T., Touam, M., and Lacour, B., Nefrologia. 1986. 6, 67. Andreoti, S. P., Bcrgtcin, J. M., and Sherrad, D . J., New Engl. J. Med., 1984, 310, 1079. Siderman, S . , and Marior, D., Nephron, 1982, 31, 1. Joffc, P., Olscn, F., Hcaf, J . G.. Gammelgaard, B., and Podenphant, J . , J. Clin. Nephrol., 1989, 32. 133. Vargas, J. H.. Klein. G . L . , Ament. M. E., Ott. S. M., Sherrad, D. J., Horst, R. L., Berquist, W. E., Alfrey, A. C., Slatopolsky, E., and Coburn. J. W., Am. J . Clin. Nutr., 1988,48, 1070. Woolfson, A. D., and Gracey, G . M., J. Clin. Pharm. Ther., 1988, 13, 243. 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 Fcrnandez Gutierrez, A., and Muiioz de la PeAa, A., in Molecular Luminescence Spectroscopy: Methods and Applica- tions, Part I, ed.Schulman. S. G.. Wiley, New York. 1985, ch. Dagnall, R. M., Smith, R . , and West, T. S . , Chem. Ind. (Lowdon), 1965,34, 1499. Dagnall, R. M., Smith, R., and West. T. S . , Tulunta, 1966, 13, 609. Morishige, K., Anal. Chim. Acfa, 1980, 121, 301. Capitan, F., Manzano, E., Navalon, A . , Vilche7, J. L., and Capitan-Vallvcy, L. F., Analyst, 1989, 114, 969. Capitan, F., Manzano, E., Vilchez, J. L., and Capitan-Vallvey, L. F., Anal. Sci., 1989. 5, 549. Capitan, F., Navalon, A.. Vilchez, J. L., and Capitan-Vallvey. L. F., Talantu, 1990, 37, 193. Capitan, F., de Gracia, J . P., Navalon. A., Capitan-Vallvey, L. F., and Vilchez, J. L., Analyst, 1990, 115, 849. Capitan, F., Manzano. E., Navalon, A., Vilchcz, J . L., and Capitan-Vallvey, L.F., Talanta, 1992, 39, 21. Capitan, F., Sanchcz-Palcncia. G . , Navalhn, A.. Capitan-Vall- vey, L. F., and Vilchez, J . L., Anal. Chim. Acta, 1992,259,345. Manzano, E., Ph.D. Thesis, University of Granada, Spain, 1989. Oms, M. T., Cerda. V., Garcia-Sanchez, F., and Ramos, A . L., Talanta, 1988, 35, 671. American Public Health Association, American Water Works Association, Water Pollution Control Federation, Mktodos Normalizados para el Analisis dc Aguas Potables y Residuales, Diaz dc Santos, Madrid, 1992, pp. 1.45-1.47. Garcia-Vior, L. O., and Possidoni de Albinati, J. F., An. Quim., Ser. B , 1987, 83, 319. Waki. H . , Noda, S . , and Yamashita, M.. React. Polym., 1988, 7, 227. Laserna, J . J., Ph.D. Thesis, University of Malaga, Spain, 1980. Yoshimura, K., Ishii, N., and Tarutani. T., Anal. Chem., 1986, 58, 591. Yoshimura, K., Waki, H., and Ohasi, S . , Talunta. 1976,23,449. Toshimitsu, Y.. Yoshimura, K., and Ohasi, S . . Talanra, 1979. 26, 273. Capitan-Vallvey, L. F., Bosque-Sendra, J . M., and Valencia, M. C., Analusis, 1989, 17, 601. IUPAC, Nomenclature, Symbols. Units and Their Usage in Spcctrochcmical Analysis. Pure Appl. Chem., 1976, 45, 105. Guidelines for Data Acquisition and Data Quality Evaluation in Environmental Chemistry, Anal. Chem., 1980, 52, 2242. Will, F., Anal. Chem.. 1961, 33, 1360. White, C . E., McFarlanc, H. C. E., Fogt, J.. and Fuchs, R., Anal. Chem., 1967, 39, 367. Morishigc, K., Anal. Chim. Acta, 1974, 72, 295. Medina Escriche, J . , and Hernandez Hernandez, F . , Analyst, 1985, 110, 287. Capitan, F., Avidad, R . , Navalon, A., and Capitan-Vallvey, L. F., Mikrochim. Acta, 1992. 107, 65. Morishige, K . , J. Inorg. Nucl. Chem., 1978, 40. 843. 4, pp. 372-546. Paper 21041 45 F Received August 3, 1992 Accepted November 17, I992

ISSN:0003-2654    

DOI:10.1039/AN9931800303

出版商:RSC    

年代:1993

数据来源: RSC

摘要:

ANALYST, MARCH 1993, VOL. 118 COMM U NlCATlON 309 Material for publication as a Communication must be on an urgent matter and be of obvious scientific importance. Rapidity of publication is enhanced if diagrams are omitted, but tables and formulae can be included. Communications receive priority and are usually published within 5-8 weeks of receipt. They are intended for brief descriptions of work that has progressed to a stage at which it is likely to be valuable to workers faced with similar problems. A fuller paper may be offered subsequently, if justified by later work. Manuscripts are usually examined ‘by one referee and inclusion of a Communication is at the Editor‘s discretion. Network Analysis: Acoustic Energy Transmission Detection of Polynucleotide Hybridization at the Sensor-Liquid Interface Hongbo Su, Mengsu Yang, Krishna M.R. Kallury and Michael Thompson* Department of Chemistry, University of Toronto, 80 St. George Street, Toronto, Ontario, Canada M5S ?A? Palladium has been sputtered onto the surface of gold-plated thickness-shear mode acoustic wave sensors. Adsorption of polynucleotides onto the PdO surface is confirmed by X-ray photoelectron spectroscopy and by gas-phase sensor measurements. Hybridization of complementary strands of polynucleotide at the device-liquid interface results in series resonant frequency signals (network analysis) that are significantly higher than expected from mass-based responses. This observation is interpreted in terms of the perturbation of acoustic energy transmission by changes in interfacial properties on hybridization.Preliminary measurements of changes in motional resistance from network analysis are also presented. Keywords: Polynucleotide hybridization; acoustic wave sensor The ability of complementary deoxyribonucleic acid (cDNA) sequences to form double-stranded hybrids with high effi- ciency and spccificity in the presence of a mixture of many non-complementary nucleic acids was first reported by Hall and Spiegelman.1 Since this work, DNA probe technology has formed the basis of tests for genetic disease, detection of pathogenic organisms such as viruses, bacteria and parasites, establishment of personal identity in forensic cases, and assays for mutation, activation, amplification and expression of oncogenes.2 For most of the applications, hybridization probes labelled with radioisotopes such as 32P or 1251 are utilized because of their sensitivity and non-involvement of the label in the chemical reactivity of the probe molecule.However, owing to factors such as the time and effort involved in such radiolabelling procedures and the problem of fluctua- tions in specific activity, alternative transduction techniques have been explored. The two categories of hybridization detection in vogue consist of ‘indirect systems’ which utilize phenomena such as luminescence, and ‘direct’ analytical devices which are based on biosensor design.3 A recent addition to the strategy of direct detection of hybridization is the signal offered by the thickness-shear- mode (TSM) acoustic wave device.4 Fawcett et al.5 reported the immobilization of single strand nucleic acid on 9 MHz AT-cut piezoelectric crystals through covalent binding to a styrene-acrylic acid copolymer.Frequency measurements in air were observed following hybridization of polyadenylic acid(5’) with polyuridylic acid(5’). In a similar procedure a single strand Salmonella DNA probe was bound to a device, but in this case the solution part of the complementary DNA was adsorbed onto particles in order to apply the gas-phase measurement .6 The first in situ liquid-phase measurement involved attachment of single strand DNA to a self-assembled * To whom correspondencc should be addressed. monolayer of 11-mercaptoundecanoic acid bound to the gold electrode of a TSM device? A subsequent experiment also demonstrated in situ detection of DNA hybridization (invok- ing a conventional mass-based response), although no evidence was presented to confirm the occurrence of hybridi- zation at the sensor-liquid interface.8 The present work has been concerned with the role of interfacial properties such as surface viscosity and roughness on the TSM liquid-phase response,’-ll and with complete characterization of the sensor by a network analysis method.12 This technique provides the measurement of a large number of parameters in addition to the resonant frequency of the TSM crystal.12.13 In spite of the fact that several metals and their complexes have been investigated for their interaction with DNA, very few reports have dealt with the role of metal-oxide surfaces.Therefore, a study has been undertaken to elucidate the immobilization of nucleic acids on PdO deposited onto Au-plated quartz TSM crystals with a view to the development of nucleic acid hybridization probes through acoustic trans- duction.The preliminary results of this work are presented here. Experimental Instrumentation An HP 4195A Network/Spectrum Analyzer (Hewlett-Pack- ard, Palo Alto, CA, USA) was used to characterize the TSM device. A 9 MHz AT-cut quartz crystal (ICM, Oklahoma City, OK, USA) with gold electrodes (diameter 0.51 cm) was coated with about 500 8, of Pd by sputtering a Pd target (99.95%, Pure Tech, Carmel, NY, USA) under Ar + O2 using an Ultek 2400-SSA system (Perkin-Elmer, Palo Alto, CA, USA). X-ray photoelectron spectroscopy (XPS) of the poly- nucleotide-immobilized surfaces was performed with a Ley- bold Max 200 ESCA Tnstrument.310 ANALYST, MARCH 1993, VOL.118 Procedures Polyadenylic acid(5') { poly[ A], relative molecular mass ( M , ) > 100 000} and polycytidylic acid(5') (poly[C], M , 370 000- 400000) (Sigma, St. Louis, MO, USA) were immobilized by imposing 20 p1 of nucleic acid solution (1 mg ml-1) onto the Pd surface. The surface was rinsed with water and immersed in water and buffer solution (70"C, pH 7.0 phosphate and 0.1 mol 1-1 NaCI) for 20 min followed by drying in an oven (80 "C). Polyuridylic acid(5') (poly[U], M , 800 000-1 200 000) and polyguanidylic acid(5') (poly[G], M , 170 000-300 000) (Sigma) solutions (0.2 mg ml-1) were incubated to 60 "C and injected into the measurement cell which contained the poly[A] and poly[C]-coated devices, respectively.The poly- nucleotide-coated devices were stabilized in buffer solution at 60 "C prior to the injection and about 0.3 mg of polynucleotide was introduced upon each injection. The other, uncoated, side of the device was protected under nitrogen. Controlled experiments with non-complementary solutions were per- formed following the same procedure. Results and Discussion Characterization of the Palladium OxidelPolynucleotide Surface by X-ray Photoelectron Spectroscopy The XP spectra of the individual polynucleotide and the hybridized surfaces (Poly [C], Poly [U], Poly [A], Poly [GI, Poly [A/U] and Poly [G/C]) were recorded without buffer treatment to avoid any contribution from these species.The C( 1s) : N( 1s) ratios and the N( 1s) : P(2p) binding energy peak ratios computed from the low resolution elemental composi- tion data are presented in Table 1. Also presented in the same table are the values of the ratio C(ls)[C-N+C-O, : C(ls)lc=01 calculated for all six surfaces from high resolution experi- ments. From the data in Table 1, it can be observed that the C(1s) : N(1s) ratios are in good agreement with the calculated values. The N(1s) : P(2p) binding energy peak ratios are a fraction higher than the theoretical values for the individual poly- nucleotide surfaces. This is probably due to the orientation of the molecules on the Pd surface which could result in the attenuation of the P(2p) peak. Similar attenuation was observed by Bain and Whitesides for the S(2p) peak of thiols on Au surfaces.14 However, the hybridized surfaces do exhibit ratios close to the thoretical values, indicating that these surfaces are more uniform and possess a greater degree of orientation compared with the individual pol ynucleotide surfaces.The immobilization of the polynucleotides on the PdO surface could also be verified from the high resolution C(1s) peak ratios. As these molecules only contain C-N/C-0 and C=O carbons which appear around 286-287eV and 288- 289 eV, respectively, the ratio of these two peaks, in comparison with the corresponding theoretical values, also serves to confirm the deposition of the polynucleotides. The exact nature of the binding of polynucleotides to the Pd surface is not yet clearly understood. The XPS technique shows that the deposition of Pd under an Ar + 0 2 environ- ment produces a PdO layer, the Pd (3d) peak corresponding to the oxide appearing around 336.5 eV in contrast to Pd metal which displays its Pd (3d) peak around 335.5 eV.The interaction of Pt" with nucleotides was demonstrated to involve the N-7 nitrogen of the purine ring of the guanine moieties.15 Similarly, the complexation of cytosine with Ag' was shown to occur through the endocyclic N-3 nitrogen of the forrner.16 If these data are any indication, the present Pd" surfaces can also be presumed to react with the N-3 and N-7 nitrogens of the pyrimidine and purine oligonucleotides. Further spectroscopic studies are underway to pinpoint the nature of interaction of Pd" with these oligonucleotides. However, the most important feature of the immobilized polynucleotides is their stability under the hybridization conditions and their ability to interact with their complemen- tary strands.Detection of Polynucleotide Hybridization by Acoustic Energy Transmission Frequency measurements recorded in air after the immobili- zation of the polynucleotide and subsequent drying at room temperature with nitrogen, show average decreases of about 1200 and 630 Hz for Poly [C] and Poly [A], respectively. Each of these two immobilized oligonucleotide surfaces was sub- jected to three sets of experimental conditions before network analysis. Thus, in experiment I , the Poly [C] surface was treated with Poly [A] and after analysis, the solution was drained off and the surface rinsed twice with buffer and then treated with Poly [GI solution.After liquid phase analysis, the surface was washed with hot buffer, dried with nitrogen and the frequency recorded in air. In experiment 11, the Poly [A] used in experiment I was substituted with Poly [U], the rest of the procedure remaining the same. In experiment 111, the Poly [C] surface was treated with Poly [GI alone. A similar thrce set (IV-VI) study was made with the Poly [A] surface, using (i) Poly [C], then Poly [U]; (ii) Poly [GI, then Poly [U] and (izi) Poly [U] alone. The frequency decreases registered, in air, with the immobilized Poly [C] surface for experiments 1-111 were about 150-220 Hz. Similarly, for the immobilized Poly [A] surface, the frequency shifts for experiments TV-VI were about 70-180 Hz.Interestingly the series resonance frequency exhibits significantly higher values in the solution phase upon hybridization (Table 2). For the same set of experiments, the frequency decreases in solution are about 3-7 times larger than those in air. The real-time measurements of the frequency response of the two polynucleotide-coated TSM devices upon exposure to complementary and/or non-com- plernentary polynucleotide solutions are shown in Fig. 1. These results clearly demonstrate the occurrence of a sequence-specific hybridization process at the sensor-liquid interface when complementary nucleotides are used. The frequency shifts were negligible when the polynucleotide- coated surfaces were exposed to the non-complementary polynucleotide solution.One of the parameters derived from the network analysis of Table 1 XPS ratios from elemental composition and high resolution measurements on the C(1s) binding energy peaks Oligonucleotide C( 1 s) : N( Is) N(1s) : P(2p) c(ls)[C-N+C-O] : c(ls)[C=O] on the Pd" surface Found Calculated Found Calculated Found Calculated POlY [CI 3.3: 1 3 : 1 3.5: 1 3 : 1 6.2: 1 7 : 1 POlY [UI 3.9: 1 3 : 1 3 : 1 2 : 1 2.9: 1 3 : 1 POlY [A1 2.3 : 1 2 : 1 5.6: 1 5 : l No C=O carbons POlY [GI 3.1 : 1 2: 1 5.7: 1 5:1 8 : 1 9 : 1 Poly [ N U ] 2.5 : 1 2.5 : 1 3.8: 1 3.5: 1 15: 1 13: 1 Poly [C/G] 2.5: 1 2.5 : 1 3.8: 1 4: 1 6 : 1 8 : 1ANALYST, MARCH 1093, VOL. 118 31 1 Table 2 Series resonant frequcncy decreases of the polynucleotide-immobilized TSM devices upon hybridization Immobilized polynucleotide Injection steps Experiment Sample Afin a,r/Hz 1 2 Afn air/Hz A f n wln/Hz I1 POlY [CI 1156 POlY LUl POlY [GI 218 544 111 POlY [CI 1215 POlY [GI 1s 1 V POlY [A1 624 POIY [GI POIY [UI 73 VI POlY [A1 624 POlY[UI 102 570 I POlY [CI 1283 POlY [A1 POlY [GI 162 680 1169 IV POlY [A1 654 POlY [CI POlY [UI 177 520 SO0 Step 1 Step 2 (a) 1.i I Step I I200 Hz 0 1000 2000 3000 4000 5000 6000 7000 8000 Time/s ( 6 Step 1 Step 2 I I Step 1 Step 2 0 1 0 RunlV I Step 1 I 0 amw=m 0 V n 0 I100 Hz Run VI I 1 I I I I I 0 1000 2000 3000 4000 5000 6000 7000 Time/s Fig. 1 Responses of the series resonant frequency of (a) the poly[C]- and ( 6 ) the oly[A]-coated TSM devices exposed to non-complemen- tary (step 17 and complementary (ste 2) polynucleotidc solutions.Immobilized poly[C] treated with: polyf)A] and then with poly[G] (run I); poly[U] and then poly[G] (run’ 11); poly[G] on1 (run 111). Immobilized poly[A] treated with: poly[C] and then p o l y b ] (run IV); poly[G] and then poly[U] (run V); poly[U] alone (run VI) 0 1000 2000 3000 4000 5000 60007000 8000 Tirneh 0 Run IV Step 1 Step 2 I 1 Run V Step 1 Step 2 n VI Step 1 i - I I I I I I I 0 1000 2000 3000 4000 5000 6000 7000 Tirne/s Fig. 2 see Fig. 1 Responses of the equivalent circuit resistance. For conditions3 12 ANALYST, MARCH 1993, VOL. 118 the TSM device is the electric equivalent circuit resistance. The motional resistance, R,, represents the dissipation of acoustic energy into the quartz and into the surroundings. The amount of acoustic energy transmitted to the liquid is mediated by the sensor-liquid interface and R,, changes with the structure of the interface. Rigid mass loading has a minimal effect on the resistance.The response of the resistance during the hybridization is depicted in Fig. 2. Our results indicate that R, increases as hybridization occurs. However, a surprising unexpected difference in the behaviour of R, can be observed that is dependent on the nature of the polynucleotide bound to the surface or based on the sequence of addition of the polynucleotide solutions in experiments I-VI. Thus, when immobilized Poly [C] is treated with the non-complementary Poly [A], a significant decrease in R, occurs. On the other hand, when immobilized Poly [A] is reacted with a solution of Poly [C], no change in R,, is observed.Further, when immobilized Poly [C] is treated first with Poly [A] solution and then with Poly [GI, only a marginal increase in R,, is observed, in comparison with the large shift in R, recorded in experiment I1 (immobilized Poly [C] + Poly [U] and then Poly [GI). This increase in R, is even larger than the example where immobilized Poly [C] is treated imme- diately with Poly [GI solution (experiment 111). It is to be noted that the largest shift in R, is associated with a minimal decrease in frequency (experiment I1 versus experiments I and Similar variations in R, are observed with the immobilized Poly [A] surface. The largest increase in R, is noticed in experiment I where Poly [A] is first treated with a solution of Poly [C] and then with Poly [U).The R, value of the straight Poly [A]-Poly [U] hybridization (experiment VI) is inter- mediate between experiments TV and V. The above observations concerning the R, clearly indicate that although non-complementary polynucleotides do not bind to immobilized polynucleotide surfaces, they do cause a significant shift in the structure of the surface-bound mol- ecules. As the most plausible reason for such changes with molecules such as the oligonucleotides is an orientational change at the interface, it is to be assumed that the non-complementary nucleotides bring about such alterations in the surface-anchored nucleotide molecules. Poly- nucleotides consist of polar sugar phosphate moieties and relatively less polar nucleobase moieties. As the binding of the polynucleotides to the PdO surface is presumed to be through the nitrogen atoms of their nucleobase, a flip-flop of these moieties will expose the sugar phosphate moieties to the liquid phase on top.The immobilized Poly [C] undergoes twice as large a shift in R, upon treatment with Poly [U] and then Poly [GI, in comparison with the immobilized Poly [A] which shows 111). maximum shift in R, when treated with Poly [C] followed by Poly [U]. It appears that more sugar phosphate moieties are exposed to the medium in the former compared with the latter, which in turn indicates that pyrimidine systems undergo orientational changes more readily than purine bases at metallic surfaces. This work demonstrates that the network analysis technique can be utilized not only for following nucleic acid hybridiza- tion but also for the study of orientational changes during the interaction between either complementary or non-com- plementary strands.We are very grateful to the Natural Sciences and Engineering Council of Canada for support of this work. 1 2 3 4 5 6 7 8 9 I0 11 12 13 14 15 16 References Hall, B. D., and Spiegelman, S . , Proc. Natl. Arad. Sci., U.S.A., 1961, 47, 137. Symons, R. H., Nucfeic Acid Probes, CRC Press, Roca Raton, FL, 1989. Downs, M. E. A., Kobayashi, S., and Karube, I . , Anal. Lett., 1987, 20, 1897. Thompson, M., Kiplipg, A. L., Duncan-Hewitt, W. C., Rajakovid, Lj. V., and CaviC-Vlasak, B. A., Analyst, 1991, 116, 881. Fawcett, N. C., Evans, J. A., Chien, L.-C., and Flowers, N., Anal. Lett., 1988, 21, 1099. Richards, J. C . , and Bach, D. T., Eur. Put., 0 295 965, 1988. Su, H., M.Sc. Thesis, University of Toronto, 1991. Okahata, Y . , Matsunobu, Y . , Kuniharu. I., Masayuki, M., Murakami, A., and Makino, K . , J. Am. Chem. SOC., 1992,114, 8299. RajakoviC, Lj. V., CaviC-Vlasak, B. A., Ghaemmaghami, V., Kallury, K. M. R., Kipling, A. L., and Thompson, M., Anal. Chem., 1991, 63. 615. Duncan-Hewitt, W. C., and Thompson, M., Anal. Chem., 1992, 64, 94. Yang, M. Thompson, M., and Duncan-Hewitt, W. C., Lang- muir, in the press. Kipling, A . L., and Thompson, M., Anal. Chem.. 1990, 62, 1514. Martin, S. J., Granstaff, V. E., and Frye, G. L., Anal. Chem., 1991, 63, 2272. Bain, C. D., and Whitesides, G . M., J. Phys. Chem., 1989, 93, 1670. Hartwig, J. F., and Lippard, S. J . , J. Am. Chem. Soc., 1992, 114, 5646. Menzer, S . , Sabat, M., and Lippert, B . , J. Am. Chem. SOC., 1992, 114,4644. Paper 21060.570 Accepted January 18, 1993

ISSN:0003-2654    

DOI:10.1039/AN9931800309

出版商:RSC    

年代:1993

数据来源: RSC

摘要:

ANALYST, MARCH 1993, VOL. 118 313 Adams. Michael J., 229 Andrew, B. E . , 153 Ashok Kumar, T., 293 Avidad, Ramiro, 303 Bae, Yea-Ling, 297, 301 Bangar Raju, G., 101 Barclay, David A.. 245 Barjat. Herv6, 73 Barnard Howie, Judith A., 35 Bayo, Javier, 171 Bell, Jimmy D., 241 Belton. Peter S . , 73 Bhaskar, Nilam. 1 Biondi, Cinzia, 183 Birmingham, John. J.. 1 Brinkman, Udo A. Th., 11 Bruns, Roy E., 213 Cai, Xiaohua, 53 Canela, Ramon, 171 Capitan-Vallvcy , Luis Fcrmin, Carlos dc Andradc, J o ~ o , 213 Carlson, Robert G., 257 Cermak, Josef, 79 Chadima. Radko, 79 Chaisuksant, Rasamee, 179 Chartier. A . , 157 Chen. Liang, 277 Chokshi. Hitesh P., 257 Clarke, Colin G., 229 Corbini, Gianfranco, 183 Cordcro, Bernard0 Moreno, 209 Corti, Picro, 183 Cotsaris, Evangelo, 265 Cummins, Diane, I Cummins, Phillip G ., 1 Daenens. P., 137 Davis. Willard E . , 249 de la Guardia, Migucl. 23 de Paula Eiras, Sebastiiio, 213 Debrabandcre, Lode, 137 Diaz, Susana, 171 Diewald, Wolfgang, 53 Domingucz, Lucas, 171 Dowle, Chris J . , 17 Dreassi, Elcna, 183 Economou, Anastasios, 47 Egan, Dcnisc A., 201 Espinosa-Mansilla, Anunciacion, 89 303 CUMULATIVE AUTHOR INDEX JANUARY-MARCH 1993 Fcarn, Tom. 235 Fernandez Laespada, Ma. Esther, 209 Feygin, Ilya, 281 Fielden, Peter R., 47 Fox, C. G., 157 Fraidias Becerra, Antonio J., Frutos, G . , 59 Fu, Chengguang. 269 Gaind, Virindar S., 149 Garcia Gomez de Barreda, Daniel, 175 Garcia-Lopez, Trinidad, 303 Georges, J., 157 Ghijsen, Rudy T., 11 Givens, Richard S . , 257 Goodfellow, Brian J . , 73 Greenway, Gillian, 17 Gregory, Donald P., 1 Grob, Robert, 11 Gu, Zhi-cheng, 105 Haswell, Stephen J., 245 Hawkins.Peter, 35 Hembree. Jr., Doyle M.. 249 Hidalgo de Cisneros. Jos6 L. Hokari, Norihisa, 219 Howard, Vyvyan C., 1 Huang, Ka-lin, 205 Hunt, Terence P.. 17 Idriss. Kamal A., 223 Iizuka, Ryuji, 165 Ishida, Junichi, 165 Iwachido, Tadashi, 273 Jedrzejczak, Kazik, 149 Jones, Carol L., 1 Ju, Dowcon, 253 Kalchcr, Kurt, 53 Kallury, Krishna M. R., 309 Kasumimoto, Hanae, 131 Katz, Stanley E.. 281 Kesslcr, Margalith, 235 Kinoshita, Toshio, 161 Kobayashi, Atsushi, 273 Kobayashi, Shouichi. 131 Kotrly, Stanislav, 79 Kovanic, Pavel, 145 Krishan Puri. Bal. 85 Kubal, Gina, 241 175 Hidalgo, 175 Kumar, Manjeet. 193 Lan, Chi-Ren, 189 Li, Xiang-Ming, 289 Liang. Wei-An, 97 Lin, Yuehe, 277 Lopez Ruiz, B., 59 Lunte, Susan M., 257 Magee, Robert J., 53 Martin, J.P., 59 Mathieu, Jacques, 11 Mellidis, Antonios S . , 179 Mertens, Bart, 235 Midgley, Derek, 41 Miller, Richard M.. 1 Moreno, Miguel A . , 171 Moriyama, Youichi, 29 Moss, Martin C., 1 Muiioz Leyva, Juan A.. 175 Nabekura, Tomiko, 273 Nagahiro, Tohru, 85 Nakagawa, Genkichi, 219 Nakamura, Kayoko, 29 Navalon, Alberto, 303 Neuhold. Christian, 53 Nicholson. Brenton C., 265 Nimura, Noriyuki, 161 O'Kennedy, Richard, 201 Palaniappan, R., 293 Papageorgiou, Vassilios P., 179 Paukcrt, Tom%, 145 Pkrez Pavon, Josk Luis, 209 Peris Cardells, Empar, 23 Pitre. Krishna S . , 65 Pramauro, Edmondo, 23 Preston, Gaynor, 245 Prevot, Alessandra Bianco, 23 Prieta, Javier, 171 Proietti, Danicla, 183 Pyo, Dongjin, 253 Radulovic, Stojan, 241 Raurich.Josep Garcia, 197 Reckhow, David A., 71 Ruan, Fu-Chang. 289 RubcSka, Ivan, 145 Rubio Leal, Amparo, 89 Sadlcr, Peter J . , 241 Salch, Magda M. S . , 223 Salinas, Francisco, 89 Salvatore, Michael J . , 281 Sanchis, Vicente. 171 Sanz Pedrero, P . , 59 Satakc, Masatada, 85 Savarino, Piero. 23 Shcppard, Robert C., 1 Shimoishi, Yasuaki, 273 Singleton, Scott, 1 Smyrl, Norman R., 249 Sramkova, Jitka, 79 Srivastava, P. K., 193 Su, Hongbo, 309 Suirez, Guillermo, 171 Svendsen, C. N., 123 Tang, Gui-na, 205 Taniguchi, Hirokazu, 29 Thompson, Michael, 235, 309 Torrades, Francesc, 197 Toyo'oka, Toshimasa, 257 Tsai, Suh-Jen Jane, 297. 301 Tsuzuki, Wakako, 131 Tucker, Alan, 241 Van Bovcn, M., 137 Veiro, Jcffrcy A., 1 Verma, Neerja, 65 Vijaya Raju, K., 101 Vilchez, J o d Luis, 303 Viscardi, Guido, 23 Voulgaropoulos, Anastasios, Wada, Hiroko, 219 Wang, Bao-ning.205 Wang, Joseph, 277 Williams, David M., 249 Williams, Kathleen E., 245 Wong, Kwok-Yin, 289 Wuchner, Klaus, 11 Xie, Yuefeng. 71 Xu, Hongda, 269 Yamaguchi, Masatoshi, 165 Yamauchi, Shuji, 161 Yang, Mengsu, 309 Yoshida, Tomohiko, 29 Yuchi, Akio, 219 Zenki, Michio, 273 Zhcng, Minghui, 269 Zhou, Jie, 97 Zhu, Zhong-Iiang. 105 179 ZOU, Shi-Fu, 97Pre- and Post-Symposia and Short Courses XXVIII Colloquium Spectroscopicurn Interna tionale PRE-SYMPOSIUM 3rd Kingston Conference. Analytical Spectroscopy in the Earth Sciences June 28-29,1993 SHORT COURSES Introductory Chemometrics June 29,1993 Vapour Generation Techniques: Theory and Practice June 29,1993 Spectroscopic Data Handling July 46,1993 5th Surrey Conference on Plasma Source Mass Spectrometry July 46,1993 Application of Glow Discharge in Optical and Mass Spectroscopy Graphite Atomizer Techniques in Analytical Spectroscopy Trace Elements in Clinical Biochemistry July 7, 1993 For further information contact- POST-SYMPOSIA July 4-7,1993 July 4-7,1993 Kingston University, Surrey University of York University of York University of York Lumley Castle Hotel, Co. Durham University of York University of Durham University of Durham XXVIII COLLOQUIUM SPECTROSCOPICUM JNTERNATIONALE Department of Chemistry (CSI Secretariat) Loughborough University of Technology, Loughborough, Leicestershire, UK LEll3TU

ISSN:0003-2654    

DOI:10.1039/AN9931800313

出版商:RSC    

年代:1993

数据来源: RSC