Separation and determination of tellurium(IV) and -(VI) by electrothermal atomic absorption spectrometry using a tungsten furnace after collection as the 3-phenyl-5-mercapto-1,3,4-thiadiazole -2(3H)-thione–tellurium complex on cobalt(III ) oxide Tomohiro Narukawa Department of Chemistry, Chiba Institute of Technology, Shibazono, Narashino, Chiba 275–0023, Japan Received 16th June 1998, Accepted 13th November 1998 Using cobalt(III ) oxide powder as a collector of tellurium(IV) and -(VI), the latter are separated from matrix components contained in a sample solution, then determined by electrothermal atomic absorption spectrometry using a tungsten furnace.When only cobalt(III ) oxide powder was used for the collection of tellurium, the recovery of tellurium(IV) and -(VI) increased as the sample solution became more basic; almost 100% recovery was obtained at pH 11.0. When 0.1% m/v 3-phenyl-5-mercapto-1,3,4-thiadiazole-2(3H)-thione potassium salt (bismuthiol II) was used as an auxiliary agent for the collection, there was diVerence in the collection behavior between tellurium(IV) and -(VI) depending on the pH of sample solution (100 ml ): 100% recovery was obtained at pH 1–7 for tellurium(IV) and at pH 3–7 for tellurium(VI).Therefore, by collecting tellurium(IV,VI) at pH 4.0 and then tellurium(IV) at pH 1.0, fractionation and determination of tellurium(IV,VI) can be achieved. The cobalt(III) oxide powder used as a collector is also eVective as a chemical modifier in the determination; by introducing cobalt(III) oxide powder in the form of a slurry (5 ml ) into a furnace, the volatilization loss of tellurium could be suppressed up to a charring temperature of 1400 °C.For 1.25 mg per 5 ml (0.25 mg l-1) tellurium(IV), when this method was used the relative standard deviation (n=6) was <3%. The detection limit (3s) was 12 mg l-1 (0.12 ng per 10 ml ). The method applied to several water samples, experiments being performed on the fractionation and determination of tellurium(IV,VI), and 100% recovery was obtained.In Europe and the USA, although tellurium is designated as tungsten tube. In addition, with respect to ETAAS using a tungsten furnace containing a tungsten board as the furnace, a harmful contaminant, it has become the focus of attention in terms of its use in semiconductors. In nature, tellurium is the behavior and determination of tellurium have not yet been investigated. present in the form of tellurite [TeO32-, tellurium(IV)] and/or tellurate [TeO42-, tellurium(VI)], and is distributed widely in Since elements exhibit diVerent toxicity levels depending on the chemical species present, analysis for diVerent chemical the Earth’s crust in trace amounts.Concentrations of tellurium in natural waters are generally at the sub-ppt level.1 Therefore, species, so-called speciation, becomes important for water samples; therefore, methods of determination following the it is diYcult to determine tellurium, and the behavior of tellurium in nature is almost unknown.separation of diVerent existing forms have become important. 13–15 In recent years, for determinations of diVerent chemi- The following method has been used as a major method for the determination of tellurium.2,3 3-Phenyl-5-mercapto- cal species, on-line analytical methods using a combination of chromatography and ICP-MS and other methods have been 1,3,4-thiadiazole-2(3H)-thione potassium salt (bismuthiol II ) is used to form a complex with tellurium(IV), and after pre- investigated.16 Another eVective method involves determination using AAS or ICP-AES after fractionation of a specified treatment by organic solvent extraction, the concentration of tellurium(IV) is determined by absorptiometry.4,5 Another chemical species using solvent extraction and collectors.We have found that, as a collector of micro-amounts of method in which tellurium hydroxide is introduced into a furnace for electrothermal atomic absorption spectrometry elements present in a solution, cobalt(III ) oxide (Co2O3) exhibits a superior collection ability to some metallic elements.In (ETAAS) permits the highly sensitive determination of tellurium. 6,7 With ETAAS using a graphite furnace and a method addition, cobalt(III ) oxide is fairly stable against pH changes in the solution without being dissolved, and could be used as including pre-treatment, the eVects and behavior of a chemical modifier in the analysis of aqueous solution samples were a collector in strongly acidic solutions.It is also eVective as a chemical modifier for determining lead and bismuth by means investigated,8 and the method was applied to various environmental samples.9,10 of ETAAS using a tungsten furnace.17–20 In these experiments, we attempted to apply cobalt(III) oxide In contrast, very few findings regarding the behavior and determination of tellurium in a tungsten furnace have been as a collector for the fractionation and determination of trace amounts of tellurium(IV) and -(VI) present in a solution.In reported. Suzuki and co-workers11,12 reported the behavior of tellurium during atomization using a tungsten tube as the addition, bismuthiol II is an eVective auxiliary agent for the fractionation and collection of tellurium(IV) and -(VI). furnace. However, when a commercially available conventional tungsten board was used in the furnace, the behavior of Therefore, we investigated the fractionation and determination of tellurium(IV) and -(VI) present in a solution by means of tellurium during atomization and the eVects of a chemical modifier were not always identical with those when using a ETAAS using a tungsten furnace.J. Anal. At. Spectrom., 1999, 14, 75–80 75Table 1 Instrumental operating parameters Experimental Tellurium Reagents Parameter Dry Char Atomize Clean Ultrapure water purified with a Milli-Q-Labo filter (Nippon Millipore, Tokyo, Japan) was used throughout.Ramp time/s 10 10 0 0 Hold time/s 20 15 2 1 Temperature/ °C 130 1200 2400 2600 Tellurium(IV ) standard solution. This was prepared by Wavelength 214.3 nm diluting AAS-grade tellurium solution (1000 mg l-1, 6 M HCl) Spectral bandwidth 0.50 nm (Wako, Osaka, Japan) with water. Lamp current 10 mA Gas flowrate Ar 5.0 l min-1 H2 1.0 l min-1 Tellurium(VI ) standard solution.This was prepared as follows. Precisely 0.255 g of sodium tellurate (95.0% Na2H4TeO6) (Wako) was dissolved in water to make 100 ml of solution, Results and discussion providing a 1000 mg l-1 stock standard solution of tellurium( VI). This stock standard solution was diluted with Studies of measurement conditions water to give working standard solutions for use in the experiments. Influence of charring temperature. Using 0.25 mg l-1 tellurium(IV) and -(VI) standard solutions and a constant atomization temperature 2400 °C, the eVects of charring tem- Cobalt(III ) oxide.The required amounts of cobalt(III ) oxide perature on the absorbance obtained during the atomization powder (purity 99.5%) (Wako) were measured and used for were investigated by varying the charring temperature in the the experiments. range 200–1400 °C. At the same time, the following two solutions were used for the same experiments, and the results obtained are shown in Fig. 1: (1) 5 ml of 0.25 mg l-1 tel- Bismuthiol II solution. A 0.1 g amount of commercially lurium(IV) or -(VI) standard solution in which 30 mg of available bismuthiol II agent (C8H5KN2S3·xH2O) (Tokyo cobalt(III) oxide was dispersed (suspension); and (2) a solution Kasei, Tokyo, Japan) was dissolved in 100 ml of water to give containing 1.25 mg of tellurium(IV) or -(VI) prepared according a 0.1% m/v bismuthiol II solution. The solution was stored in to the procedure and made into a slurry (1.25 mg in 5ml= the dark, and was freshly prepared approximately every 2 0.25 mg l-1). The absorption signals of tellurium obtained weeks.using these solutions are shown in Fig. 2. When only tellurium(IV) or -(VI) standard solution was used, Apparatus the absorbance gradually decreased with increasing charring temperature. The absorbance of tellurium(IV) obtained during An PS200A electrothermal atomizer was attached to an the atomization was higher than that of tellurium(VI). SAS7500A spectrometer (Seiko Instruments, Chiba, Japan).On the other hand, with respect to tellurium(IV) and -(VI) An L-233 hollow cathode lamp (Hamamatsu Photonics, solutions with dispersed cobalt(III) oxide, the absorbance Hamamatsu, Japan) was employed and a deuterium lamp was maintained a constant value in the charring temperature range used for background correction. At the sample introduction 200–1300 °C and was the same for both species of tellurium. part, a high capacity (50 ml ) U-type metal board made of In the case of the slurries prepared according to the tungsten was used.experimental procedure using bismuthiol II as an auxiliary agent, an absorbance approximately twice that of the Procedure 0.25 mg l-1 tellurium(VI) standard solution was obtained in the charring temperature range 200–400 °C. However, back- The pH of 100 ml of sample solution containing 2.5 mg of ground absorption resulting from bismuthiol II was simul- total tellurium was adjusted to 4.0 using hydrochloric acid taneously observed, and a result that lacked reproducibility, and ammonia solution, and then combined with 2.0 ml of such as a relative standard deviation (RSD) of 6–7% for six 0.1% m/v bismuthiol II solution and 30 mg of cobalt(III) oxide powder and mixed for 15 min by sonication.The resulting solution was filtered by vacuum using a membrane filter made of nitrocellulose (diameter 25 mm, pore size 8.0 mm) and separated into a solid phase [cobalt(III) oxide powder] and filtrate.The solid phase obtained was washed with water, introduced into a test-tube with the cobalt(III ) oxide powder together with the membrane filter and mixed with 5 ml of water to make a slurry. The test-tube was shaken well by hand so that the suspended solid was dispersed uniformly in the tube, then part of the slurry was introduced into a tungsten furnace. This sample was atomized according to the conditions shown in Table 1 and the absorbance of tellurium (peak height) was measured.For the fractionation and determination of tellurium(IV) and -(VI), the pH of the sample solution was adjusted to 1.0 and procedures similar to those mentioned above were performed so that only tellurium(IV) was collected by the cobalt(III ) oxide powder. By means of ETAAS using a Fig. 1 EVect of charring temperature. +, TeIV standard solution tungsten furnace, the concentration of tellurium(IV) was first (0.25 mg l-1) only; 6, TeVI standard solution (0.25 mg l-1) only; measured, then the concentration of tellurium(VI) was calcu- &, suspension of TeIV and cobalt(III) oxide; %, suspension of TeVI lated by subtracting the concentration of tellurium(IV) from and cobalt(III ) oxide; $, slurry of TeIV for the proposed method; #, slurry of TeVI for the proposed method.Injection volume: 10 ml. that of total tellurium. 76 J. Anal. At. Spectrom., 1999, 14, 75–80Fig. 2 Atomic absorption profiles of tellurium on atomization.Fig. 3 EVect of pH on the collection of TeIV and TeVI.&, Tellurium(IV) (A) TeIV standard solution (charring temperature: 200 °C); (B) TeVI only;%, tellurium(VI) only;$, tellurium(IV) with 0.1% m/v bismuthiol standard solution (charring temperature: 200 °C); (C) suspension of II; #, tellurium(VI) with 0.1% m/v bismuthiol II. Sample volume, TeIV and cobalt(III) oxide (charring temperature: 200 °C); 100 ml; stirring time, 15 min; cobalt(III ) oxide, 30 mg; amount of TeIV (D) suspension of TeVI and cobalt(III) oxide (charring temperature: or TeVI, 1.25 mg. 200 °C); (E) suspension of TeIV and cobalt(III) oxide (charring temperature: 1200 °C); (F) suspension of TeVI and cobalt(III ) oxide (charring temperature: 1200 °C); (G) slurry of TeIV for the proposed However, as the pH increased, the recovery gradually increased method (charring temperature: 200 °C); (H) slurry of TeVI for the and became 100% for both tellurium(IV) and -(VI) at pH 11.0.proposed method (charring temperature: 200 °C); (I ) slurry of TeIV On the other hand, when bismuthiol II was also added as for the proposed method (charring temperature: 1200 °C); (J ) slurry an auxiliary agent, a recovery of 100% was obtained for of TeVI for the proposed method (charring temperature: 1200 °C). tellurium(IV) in the pH range 1.0–7.0 and for tellurium(VI) in Concentration of TeIV or TeVI, 0.25 mg l-1; injection volume, 10 ml.the pH range 3.0–7.0. In addition, no tellurium(VI) was collected in the pH range 1.0–1.5. Based on these results, the pH value to be used for determining the determination of total measurements, was obtained. The absorption signals obtained tellurium was fixed at 4.0 and that for the collection of at a charring temperature of 600 °C showed a shoulder, tellurium(IV) alone at 1.0. indicating broad-type absorption signals. In the charring tem- In the proposed method, bismuthiol II was added to sample perature range 1000–1400 °C, constant absorption signals with solutions after adjustment of their pH values.However, when good reproducibility (RSD 3%, n=6) were obtained, and bismuthiol was added first and then the pH was adjusted, no background absorption resulting from bismuthiol II was similar recovery trends with pH change were obtained. observed. At this charring temperature, the absorbance was similar to that of tellurium solution with dispersed cobalt(III ) EVects of mixing time oxide.Based on the results obtained, a charring temperature of 1200 °C and a charring time of 15 s were adopted. The pH of 100 ml sample solutions containing 1.25 mg of tellurium(IV) or -(VI) was adjusted to 4.0, then 30 mg of For solutions containing cobalt(III) oxide, no decrease in the absorbance due to the volatilization of tellurium was cobalt(III) oxide and bismuthiol II were added. The samples thus prepared were mixed for various time periods and the observed even at charring temperatures of 1000–1400 °C, and the absorbances obtained for the solutions were higher than recoveries were determined.The reaction time was set at 0 min, 30 mg of cobalt(III) oxide dispersed in water were filtered by those of the tellurium standard solutions. In addition, the absorption signals of tellurium(IV) and -(VI) during atomiz- vacuum and placed uniformly on a membrane filter, then the sample solutions containing tellurium were introduced on to ation coincided.Hence cobalt(III) oxide was considered to be eVective as a chemical modifier for the determination of the filter. A recovery of 30% was obtained. As the mixing time increased, the recovery increased. A recovery of 100% was tellurium by ETAAS using a tungsten furnace. obtained for both tellurium(IV) and -(VI) when the mixing time was 10 min, and was maintained up to a mixing time of Influence of atomization temperature. Using the slurries of tellurium(IV) and -(VI) prepared as mentioned above, the 30 min.Considering the requirements for rapid operation and concentration of a large volume of sample solutions, the influence of the atomization temperature of tellurium was tested. When the charring temperature was kept at 1200 °C mixing time adopted was 15 min. When a solution was mixed for 15 min and left to stand for 6 h, and then a slurry was and the atomization temperature was varied, constant absorbances were obtained at atomization temperatures of prepared from that solution and used for the measurement, a recovery of 100% was obtained and no change in the recovery 2300–2600 °C.Therefore, the atomization temperature and hold time were fixed at 2400 °C and 2 s, respectively, in order was observed. Therefore, it was considered that tellurium(IV) and -(VI) collected by cobalt(III ) oxide did not redissolve in to obtain the best reproducibility. the solution. EVect of pH on collection of tellurium EVects of amount of collector For 100 ml sample solutions containing 1.25 mg of either tellurium(IV) or -(VI), the pH was adjusted to between 1.0 and Amounts of 10–50 mg of cobalt(III) oxide were added to 100 ml sample solutions containing 1.25 mg of tellurium(IV) 11.0 using hydrochloric acid or ammonia solution, then either 30 mg of cobalt(III ) oxide powder alone or both the powder or -(VI), the sample solutions were mixed for 15 min then the recovery of tellurium was determined.and bismuthiol II as an auxiliary agent were added and the recovery of tellurium was determined. Fig. 3 shows the results. A recovery of approximately 50% was obtained when 10 mg of cobalt(III) oxide were added. This was because the apparent When only cobalt(III ) oxide was added, the recoveries of tellurium(IV) and -(VI) at pH 1.0 were 70 and 5%, respectively. solid-to-liquid ratio was low since the volume of the slurry J. Anal. At. Spectrom., 1999, 14, 75–80 77was kept constant at 5 ml; no tellurium was detected in the filtrate.When 20–50 mg of cobalt(III) oxide were added, 100% recovery was obtained; therefore, the amount of cobalt(III ) oxide adopted in the proposed method was 30 mg. EVects of amount of bismuthiol II The recovery using various amounts of bismuthiol II in the experimental procedure was examined. The concentration of the bismuthiol II solution was set at 0.1% m/v and the volume of bismuthiol II solution added was varied from 0.5 to 20.0 ml.A 100% recovery was obtained when the volume added ranged from 0.5 to 10.0 ml. In addition, no eVect on the absorption signals or on the background absorption was observed during the atomization. When the volume added was 10.0 ml, background absorption due to bismuthiol II was observed and Fig. 4 Absorption spectrum of tellurium. (A) Tellurium(IV)– the reproducibility of the absorbance was increased to 6–8%. bismuthiol II–cobalt(II) system; (B) tellurium(VI)–bismuthiol II system; Therefore, the volume of 0.1% m/v bismuthiol II added in the (C) tellurium(VI)–bismuthiol II–cobalt(II) system.Extraction solvent: method was selected as 2.0 ml. chloroform. EVects of tellurium(IV ) and -(VI ) concentrations The pH of 100–500 ml of sample solutions containing tel- or higher. The amount of white–purple precipitate increases lurium(IV) and -(VI) was adjusted to either 1.0 or 4.0 and the as the pH increases, and reaches a maximum at pH 5.0–6.0.concentration of large volumes of solution and also fraction- In addition, under basic conditions, the precipitate begins to ation and analysis of the solution were investigated. A recovery disappear, and disappears completely at pH 12.0 or higher. of 100% was achieved with 100–500 ml of sample solution Furthermore, no such precipitate is formed when the pH is containing tellurium(IV) and -(VI). adjusted to 5.0–6.0 by the addition of hydrochloric acid to Fractionation and analysis were possible for cases in which basic solution.tellurium(IV) and -(VI) co-existed and in which their ratio After precipitation, the precipitate was extracted with diVered (Table 2). chloroform and the absorbance of the chloroform phase was measured using an absorptiometer. The results obtained are Collection mechanism of tellurium(IV ) and -(VI ) shown in Fig. 4 and demonstrate that when the tellurium(IV)– bismuthiol II–cobalt(II) system is extracted with chloroform, Bismuthiol II reacts with tellurium(IV) to form maximum absorbance is observed at around 327 nm.In con- [Te(C8H5N2H3)4], which is extracted by an organic solvent. trast, when the tellurium(VI)–bismuthiol II system is extracted Tellurium(VI) is easily reduced to tellurium(IV) by hydrochloric with chloroform, the absorption spectrum of only the bis- acid, hydrobromic acid or a reducing agent. However, in the muthiol II agent is observed at around 240 nm.In addition, proposed method, it is assumed that even when tellurium when the tellurium(VI)–bismuthiol II–cobalt(II) system is exists in a condition in which it is easily collected as total extracted with chloroform, absorption signals are observed at tellurium, its valency dose not change; tellurium is collected around 330 and 260 nm, which diVer from the results for as either tellurium(IV) or -(VI). This is because when teltellurium( IV). lurium(IV) or -(VI) is present in large amounts, such as of the However, since the amounts of tellurium present in actual order of 10 mg, tellurium(IV) forms a white–yellow precipitate samples are very low, no formation of precipitate is observed at pH 1.0 due to the presence of bismuthiol II agent.It also experimentally. We studied the precipitate of tellurium using forms a white–yellow precipitate in the presence of cobalt(II) Freundlich’s adsorption isotherm equation, which is generally (CoCl2 in 1 M HCl), which is a component of cobalt(III) oxide used for investigating the adsorption of a substance from a used as a collector in the method.liquid to a solid phase. In the experiment, the pH of a solution Tellurium(VI) forms a yellow precipitate upon addition of with an arbitrary concentration of tellurium(IV) or -(VI) was bismuthiol II agent and adjustment of pH to basic values. adjusted to 4.0; after filtering the solution, the concentrations However, tellurium(VI) is not extracted by an organic solvent.of tellurium in the solid phase (q mg l-1) and the filtrate On the other hand, when bismuthiol agent and cobalt(II) (c mg l-1) were measured to obtain an adsorption isotherm. co-exist, a white–purple precipitate is formed at around pH 3.0 Fig. 5 shows the adsorption isotherm plot obtained from the experimental results. Good linearity is obtained for both Table 2 Results of fractionation and determination for tellurium(IV) tellurium(IV) and -(VI), indicating that tellurium is collected and -(VI) from large volumes via adsorption on cobalt(III) oxide (solid phase).Accordingly, when the amount of tellurium present is very low, tellurium(IV) Amount of tellurium/mg Found (mg l-1)a,b Recovery (%) reacts with bismuthiol II to form a complex, and tellurium(VI) Sample reacts with bismuthiol II which is subject to reaction in the TeIV TeVI volume/ml TeIV TeVI TeIV TeVI presence of cobalt(III) oxide to form a reaction product, then 1.25 1.25 100 250.0 250.0 100 100 both resulting products were collected by adsorption on the 1.25 0.25 200 252.2 50.5 101 101 surface of cobalt(III) oxide. 1.25 2.50 200 248.7 499.8 99 100 1.25 0.25 300 250.1 51.2 100 102 Calibration graph 0.25 1.25 300 49.8 249.7 100 100 1.25 1.25 500 249.8 501.4 100 100 The dynamic range of the calibration graph obtained with the 0.25 0.25 500 50.6 48.9 101 98 proposed procedure was linear up to 5.0 ng of tellurium. The 0.25 1.25 500 49.8 250.5 100 100 calibration graphs for tellurium(IV) and -(VI) are identical, aSlurry: 5 ml.bRSD=2–4%. with the detection limit (3s) being 12 mg l-1 (0.12 ng in 10 ml ). 78 J. Anal. At. Spectrom., 1999, 14, 75–80Table 4 Analytical results for tellurium(IV) and -(VI) in water and waste liquid samples Added/mg Found (mg l-1)a Recovery (%) Sample Taken/ml TeIV TeVI TeIV TeVI TeIV TeVI Spring waterb 500 — — N.D.c N.D. — — 500 0.50 — 99.4 — 99 — 500 — 0.50 — 101.9 — 102 River waterb 500 — — N.D.N.D. — — 500 0.50 — 102.2 — 102 — 500 — 0.50 — 99.8 — 100 Waste liquidb 500 — — 22.4 N.D. — — 500 0.50 — 122.0 — 98 — 500 — 0.50 — 97.4 — 97 500 0.50 0.50 122.6 102.2 101 102 aSlurry, 5 ml. bNarashino, Chiba; injection volume, 10 ml. cN.D.: not detected. Fig. 5 Freundlich plots of TeIV and TeVI adsorption on cobalt(III) oxide. $, Tellurium(IV); #, tellurium(VI). Sample volume, 100 ml; cobalt(III) oxide, 30 mg; adsorption time, 15 min; temperature, room temperature; q, concentration of TeIV or TeVI in solid phase; cover a huge range, when presenting results it should not be c, concentration of TeIV or TeVI in liquid phase.stated that the test concentrations are 10–100 times those contained in natural waters. Reference to a document summar- EVects of foreign ions izing some ‘natural’ concentrations should be included and it should simply be said that the test concentrations were selected With the aim of applying the proposed method to accordingly.environmental samples, we evaluated the eVects of foreign ions on the recovery of tellurium. As foreign positive ions, Application to water samples chloride compounds were used. The amount of ions added was 10–100 times that contained in natural water. The method was applied to three kinds of water samples: Table 3 gives the results for the measurement of recovery spring water, river water and waste liquid. The pH of 500 ml when each ion co-exists in 100 ml of sample solution containing sample solutions was adjusted to either 1.0 or 4.0 using 1.25 mg of tellurium(IV) or -(VI).No eVect on the recovery is hydrochloric acid and ammonia water. Since the volume of observed when large amounts of alkali and alkaline earth slurry was 5.0 ml, the samples were subjected to 100-fold metals co-exist, or when large amounts of other metal ions concentration; however, no tellurium was detected. Therefore, are present. we conducted addition and collection experiments using As the concentrations of elements present in natural waters various samples, and obtained good results (Table 4).Since the amount of tellurium existing in natural water is Table 3 EVect of foreign ions on the determination of tellurium(IV) extremely low, no tellurium could be detected even when and -(VI) natural water samples were concentrated 100-fold. However, using the proposed method, it is possible to detect tellurium Found (mg l-1)b Recovery (%) without it being aVected by large amounts of foreign ions.Therefore, the method was applied to waste liquid containing Ion Added/mga TeIV TeVI TeIV TeVI chemicals (Table 4). In the waste liquid discharged from — —c 250.0 250.0 — — chemical laboratories prior to chemical treatment, a small NaI 200 250.5 248.6 100 99 amount of tellurium was detected. In addition, good recoveries KI 200 252.1 250.5 101 100 were obtained in the addition and collection experiments.MgII 150 250.2 251.0 100 100 Using the proposed method, tellurium with diVerent CaII 150 253.6 254.6 102 102 valencies can be easily separated from matrix components, SrII 1 250.3 250.7 100 100 BaII 5 247.8 249.2 99 100 and their amounts determined separately, using cobalt(III ) MnII 3 248.2 247.7 99 99 oxide powder as a collector. In addition, not only is the CoII 0.1 250.1 249.5 100 100 cobalt(III) oxide powder used as a collector in strongly acidic NiII 0.1 247.6 248.1 99 99 pH regions, it is also eVective as a chemical modifier of CuII 0.5 246.4 247.1 99 99 tellurium; cobalt(III ) oxide is an eVective agent for the determi- ZnII 0.2 249.8 250.0 100 100 nation of tellurium by ETAAS using a tungsten furnace.CdII 0.01 250.2 248.9 100 100 SnII 0.05 249.3 250.1 100 100 Furthermore, the method for the determination of tellurium PbII 0.5 250.7 249.1 100 100 is expected to be applicable to the analysis of industrial AlIII 10 255.3 254.2 102 102 wastewaters. CrIII 0.5 253.6 254.1 101 102 FeIII 10 247.6 246.5 99 99 AsIII 0.05 250.1 250.0 100 100 References BiIII 0.1 250.6 248.9 100 100 VV 1 248.3 248.8 99 100 1 Y. Hashimoto and Y. Sekine, Bunseki, 1990, 2, 111. 2 T. Ashino, K. Takada and K. Hirokawa, Anal. Chim. Acta, 1994, MoVI 0.01 247.9 248.1 99 99 Cl- 1000 250.0 251.1 100 100 297, 443. 3 S. Hikime, Bull. Chem. Soc. Jpn., 1960, 33, 761. NO3- 1000 254.1 252.7 102 101 SO42- 50 243.9 242.4 98 97 4 H. Yoshida, M. Taga and S. Hikeme, Talanta, 1966, 13, 185. 5 K. L. Cheng, Talanta, 1961, 8, 301. SiO32- 100 243.9 245.9 98 98 PO43- 5 244.4 244.8 98 98 6 J. C. Van Loon and R. R. Barefoot, Analyst, 1992, 117, 563. 7 M. O. Andreae, Anal. Chem., 1984, 56, 2064. aSample volume: 100 ml. bSlurry: 5 ml. cAmount of TeIV or TeVI: 8 G. Schlemmer and B. Welz, Spectrochimica Acta, Part B, 1986, 1.25 mg. 41, 1157. J. Anal. At. Spectrom., 1999, 14, 75–80 799 K. Dittrich, T. Franz and R.Wennrich, Spectrochimica Acta, Part 17 T. Narukawa, A. Uzawa, W. Yoshimura and T. Okutani, J. Anal. At. Spectrom., 1997, 12, 781. B, 1995, 50, 1655. 18 T. Narukawa, A. Uzawa, W. Yoshirura and T. Okutani, Anal. 10 G. Weibust and F. J. Lanmyhr, Anal. Chim. Acta, 1981, 128, 23. Sci., 1998, 14, 779. 11 M. Suzuki and K. Ohta, Prog. Anal. At. Spectrosc., 1983, 6, 49. 19 T. Narukawa, W. Yoshimura and A. Uzawa, Bull. Chem. Soc. 12 M. Suguki, K. Ohta, T. Yamakita and T. Katsuno, Spectrochimica Jpn., 1998, 71, 1385. Acta, Part B, 1981, 36, 679. 20 T. Narukawa, W. Yoshimura and A. Uzawa, Bunseki Kagaku, 13 H. Tao, Bunseki Kagaku, 1997, 46, 239. 1998, 47, 707. 14 K. Yokoi, Bunseki, 1996, 2, 108. 15 K. Hiraki and Y. Nakaguchi, Bunseki, 1994, 12, 1020. 16 N. P. Vela and J. A. Caruso, J. Anal. At. Spectrom., 1993, 8, 787. Paper 8/04574G 80 J. Anal. At. Spectrom., 1999, 14, 75–80