Anal. Chem. 1989, 61, 2699-2703
Table I. Phosphorus-Determination Results ( % P,O,) in Zircon BCS-388 (Certified Value = 0.12% P,O,) assay
x
short-term precisiona long-term precisionb method precisionc
0.122
S
RSD
0.119
0.002 0.004
0.120
0.003
1.64 3.36 2.50
" T e n consecutive determinations. b T e n determinations over 10 consecutive days. T e n determinations o n 10 sample specimens. Each determination is the mean of 10 400-ms integrations.
levels obtained from the three test series can be considered as very satisfactory. Registry No. P, 7723-14-0; Zn, 14940-68-2.
LITERATURE CITED Sarudi, I. Z . Anal. Chem. 1950, 737,416-423. Boix, A.; Debras-Guaon, J. Chim. Anal. 1971,53,459-469. Boix, A.; Debras-Guaon, J. Bull. SOC. Fr. C6ram. 1971,92,3-14. Jaffrezic, H.; Decarreau, A.; Carbonnel, J. P.; Deschamps, N. J. Radloanal. Chem. 1973, 78, 49-53. Garg, A. N. Radiochem. Radioanal. Lett. 1979,39,319-328. Knyazeva, D. N.; Nikitina, I.B.; Korsakova, N. V.; Volchenkova, V. A. Zavod. Lab. 1982,48, 16-18. Knyazeva, D. N.; Nlkitina, I . B.; Korsakova, N. V.; Volchenkova, V. A. Chem. Abstr. 1983,98,26956q. Korte, N.; Kollenbach, M.; Donivan, S. Anal. Chim. Acta 1983, 746, 267-270. Narayanan, P.; Khopkar, S. M. J. Liq. Chromatogr. 1985, 8 . 765-776.
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Baadsgaard, H.; Sandell, E. B. Anal. Chim. Acta 1954, 7 7 , 183-187. Riley, J. P. Anal. Chim. Acta 1958, 79,413-428. Langer, K.; Baumann, P. Z . Anal. Chem. 1975,277, 359-368. Bodkin, J. B. Analyst(London) 1976, 707,44-48. Whitehead, D.; Maiik, S. A. Analyst (London) 1978, 707, 485-490. (15) Watkins, P. J. Analyst (London) 1979, 704, 1124-1128. (16) Iosof, V.; Neacsu, V. Rev. Roum. Chim. 1980,25, 589-597. (17) Kuroda, R.; Ida. I.Fresenius' Z . Anal. Chem. 1983,376, 53-54. (18) Chaimers, R. A. Analyst (London) 1953, 78,32-36. (19) Sala, J. V.: Hernandis, V.; Canals, A. Analyst (London) 1986, 7 7 7 , 965-968. (20) c, o, Anal, Chem, lgs6,38, 1228-1234, (21) Kuroda, R.; Ida, I.; Oguma, K. Mikrochim. Acta 1984, I , 377-383. (22) Riddle, C.; Turek, A. Anal. Chim. Acta 1977,92,49-53. (23) Wohlers. C. C. ICP Inf. Newsl. 1985, 70, 593-688. (24) Winge, R. K.; Peterson, V. J.; Fassei, V. A. Appl. Spectrosc. 1979, 33,206-219. (25) Bankston, D. C.; Humphris, S. E.; Thompson, G. Anal. Chem. 1979, 57, 1218-1225. (26) Cook, J. M.: Miles, D. L. Analyst (London) 1985. . 770. . 547-549. i27j Burman, J. 0.ICP Inf. Newill. 1977,3 ,'33-36. (28) Mclaren, J. W.; Berman, S. S.; Boyko, V. J.; Russell, D. S. Anal. Chem. 1981,53, 1802-1806. (29) FariAas, J. C.; Valle, F. J. An. Odm., Ser. B 1987, 83, 310-318. (30) Debras-Guaon, J. Bull. SOC.Fr. C6ram. 1979, 123,29-35. (31) Simon, S. J.; Boltz, D. F. Anal. Chem. 1975,47, 1758-1763. (32) Tyson, J. F.; Stewart, G. D. Anal. Proc. 1981, 78,184-187. (33) DeSesa, M. A.; Rogers, L. B. Anal. Chem. 1954, 26, 1381-1383. (34) Wadeiin, C.; Mellon, M. G. Anal. Chem. 1953,25, 1668-1673. (35) Lapitskaya, E. V. G/ass Ceram. 1982,39,521-522. (36) Baialardo, A. M.; Coedo, A. G. Rev. Metal. (Madrid) 1973,9,35-38. (37) Floyd, M. A.; Fassei, V. A,; D'Silva, A. P. Anal. Chem. 1980, 52, 2 168-2 173. (10) (11) (12) (13) (14)
RECEIVED for review June 9,1989. Accepted August 14,1989.
Phosphine-Ozone Gas-Phase Chemiluminescence for Determination of Phosphate Kitao Fujiwara* Faculty of Integrated Arts and Sciences, Hiroshima University, Naka-ku, Hiroshima 730, Japan
Toshie Kanchi, Shin-ichiro Tsumura, and Takahiro Kumamaru Department of Chemistry, Hiroshima University, Naka-ku, Hiroshima 730, J a p a n
Gas-phase chemiluminescence generated by mixing phosphine and ozone has been Investigated. Various chambers for mixing ozone and phosphine were designed such as flashing ozone and phosphine in the opposite direction or i n p i n g phosphlne into ozone flow wlth the view of observing chemiluminescence: The noise power spectra in the chemiluminescence emission occurring in different chambers were given by the fast Fourier transform analysis. The color of chemiluminescence varied according to the concentration of phosphine: emission appears in the spectral range from 500 to 800 nm with peaks at 675 and 740 nm for introducing phosphine (concentration, about 15 % ); emission appears from 350 to 700 nm with the peaks at 530 and 675 nm for introducing phosphine (concentration, 103 ppm). For the quantitative analysis of phosphate, the sample solution was dried on the quartz boat, and then the aqueous NaBH, solution was applied to this dried phosphate and was dried again. Phosphine was generated by means of heating the dried mixture of phosphate and NaBH, at 480 'C, which was detected by the ozone gas phase chemiluminescence. The detection limit was 1 ng of P as phosphate and the linear dynamic range extends up to 5000 ng of P.
Several advantages can be counted for developing the conversion techniques of phosphate to phosphine, Le., extension in applicable analytical method ( I ) , elimination of sample matrix effects, and increase in sensitivity. In the previous papers (2-4), several methods have been proposed for phosphine generation, e.g., passing fine mists of aqueous solution of phosphate on a surface of heated graphite ( 3 ) ,or the solid phase reduction of phosphate by sodium tetrahydroborate ( 4 ) . Especially, the latter method reproducibly gave the phosphine and is rather simple when compared to the former method. In this paper, phosphine generated with the solid phase reduction of phosphate is detected by the gas-phase chemiluminescence with mixing ozone. In ref 3, we have studied the chemiluminescence detection of phosphate. However, the generation method of phosphine adopted was lacking in precision, and the detection limit was rather poor due to the low conversion efficiency. Thus, the instrumental and analytical conditions have to be reinspected for the gas-phase chemiluminescence detection of phosphine coupled with the solid-phase phosphine generation technique by sodium tetrahydroborate. The simple and high sensitive detection method of phosphate has been established.
0003-2700/89/0361-2699$01.50/0 0 1989 American Chemical Society
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ANALYTICAL CHEMISTRY, VOL. 61, NO. 24, DECEMBER 15, 1989
Table I. Summary of Instruments Used ozone generator Nippon Ozone Co., Type 0-3-2 spectrometer Jasco, Type CT-25-C multichannel detector PCD image sensor Hamamatsu, Type S2304-512Q detector Type C2327 data processing unit Type C2890 DMA interface Type M2891 personal computer NEC, Pcgaoi vx printer PC-PR201F2 scope Trio, Type CS1577 (30 MHz) Fourier transformation and general spectral observation analyzer (recorder) Yokogawa, Type 36553 Yokogawa, Model 3659 20A FFT module dc amplifier Keithley, Type 427 dc (A/V) amplifier NF Electronic, Type LI-76 function generator NF Electronic, Model FG-121B P M power source Hamamatsu, C 488R P M (photomultiplier) Hamamatsu, R456 determination of phosphate electric furnace Mitamura Riken, 400 W digital thermometer Nippo Electric, Type LM499 P M housing with electronic cooler Hamamatsu, Type C659-A PM Type R649 photon counter T'ype C2130 strip chart recorder Hitachi, Model 056
It is well-known that phosphine ignites in the atmosphere and emits visible light, which is called ignis fatuus or will0'-the-wisp (the flickering lights seen in darkness over marshland, peat bogs, and swamps) ( 5 ) . However this luminescence was not well elucidated. As the phosphorus chemiluminescence of the room temperature, only the luminescence with oxidizing P, with addition of H 2 0 or D 2 0 has been previously reported by VanZee e t al. (6). A spectroscopic characteristics of the chemiluminescence occurred by mixing phosphine and ozone or oxygen was, therefore, also give in this paper.
EXPERIMENTAL SECTION Reagents. Phosphorous acid (H3P03) of analytical grade was purchased from Wako Chemical Industries, Ltd., for producing large amounts of phosphine. A cylinder of the standard phosphine at 103 ppm diluted with helium (produced by Nippon Sans0 Co., Ltd.) was used for continuous measurement of phosphine chemiluminescence. The standard aqueous solution of phosphorus was made by dissolving potassium dihydrogen phosphate of analytical grade (Wako). Sodium tetrahydroborate used in this study was a tablet type (Nissoh Benthoron Co., Ltd.) of the grade for atomic absorption spectrometry. Selenium (SeO, in 0.5 mol/L HNO,), lead (Pb(NO& in 0.1 mol/L HNO,), bismuth (Bi(N03), in 0.8 mol/L HNO,), germanium (K,GeO, in 0.2 mol/L KOH), antimony (SbCl, in 2.8 mol/L HCl), arsenic (As203 in 0.05% NaCl and 0.2 mol/L HCl), and tin (SnC14in 3 mol/L HCl) at loo0 ppm were purchased from Kanto Chemical Co., Inc., and were used for observing the effect of interferent ions. Apparatus. Equipment used in this paper is listed in Table I.
An ozone generator was a silent discharge type operated a t the applied electric voltage of 100 with flowing oxygen at the rate of 100 mL/min. The concentration of ozone was 13 g/m3 under this condition. Spectrometric Observation for Phosphine Chemiluminescence. To observe the chemiluminescence of phosphine a t high concentration (around l o % ) , a spectrophotometer equipped with a photodiode array was used for simultaneous observation of wide wavelength emission. A personal computer was used for processing the multichannel signal from the photodiode array. To observe the chemiluminescence of phosphine at low concentration (less than a few hundred parts per million), the same spectrometer as employed in the above multichannel measurement was used with photomultiplier detection, where a mirror was set inside the spectrometer for switching the optical pathway from the diode array to photomultiplier. The output signal of the photomultiplier through a dc amplifier was fed into
a digital analyzing recorder which has a function to perform fast Fourier transform of input signal (frequency analysis of noise in the input signal). Wavelength scanning of the spectrometer was done by a stepping motor which was controlled by a function generator. Determinationof Phosphate Ion. The method for generating phosphine from aqueous phosphate solution, which was previously reported ( 4 , 7 ) ,was improved for the chemiluminescencedetection. Two types of the sample vessels (boat and half cylindrical types) were examined. A boat-shaped container made of quartz was used as a sample container instead of a half cylinder of quartz tube which was adopted in the previous paper. This vessel shape is convenient when a large amount of sample solution is applied. The generated phosphine was mixed with ozone in a chemiluminescence chamber. Various types of chambers were designed and made in our laboratory. In the case of quantitative analysis for phosphate, a photon counting system with cooling photomultiplier was adopted because of the low intensity of chemiluminescence emission. The analog output of the photon counter was recorded on a strip chart recorder. Procedure. The recommended procedure for determination of phosphate is as follows: 10-2000 1L of phosphate solution (sample) is placed in the sample vessel and completely dried. Then, 100 pL of 6% sodium tetrahydroborate is added to this vessel and dried again a t a temperature below 45 "C in an oven for 2 h. This dried mixture is inserted into a phosphine generation tube made of quartz which is heated at 4W-500 "C by a cylindrical Nichrom heater whose temperature is controlled and monitored by a digital thermometer. Helium is used as the carrier gas of the generated phosphine and continuously flows in the phosphine generation tube a t a flow rate of 600 mL/min. Phosphine is trapped in a U-tube cooled at liquid nitrogen temperature for 2 min. This trap is packed with a small amount of quartz wool. After collecting phosphine, the cold trap is soaked (warmed) in a water bath. Phosphine is, then, introduced into the chemiluminescence chamber and mixed with ozone, which is supplied from a generator of silent discharge type through which oxygen flows at the rate of 150 mL/min. The peak height of the chemiluminescence signal fed into a strip chart recorder is read for calculating phosphate concentration. Caution: Phosphine is a poisonous gas. The lowest published lethal concentration for hamstem is 8 ppm (8). It is also explosively flammable. When using the system shown in Figure 1 for measuring chemiluminescence spectra, the operator should obey safety guides. Especially in Figure lA, when a large amount of phosphine is collected in the trap, special caution for protecting against ignition and leaking of phosphine must be required. However, it should be noted that it the quantitative analysis of phosphate ion is not dangerous when using the system shown in Figure 4 because only a small amount of phosphate is applied and converted to phosphine. The poisonous effect of phosphine is smaller than that for arsine, which is commonly treated in atomic spectroscopy.
RESULTS AND DISCUSSION Chemiluminescence Spectra of Phosphine. When phosphine at high concentration was exposed to air, the color of emission varied from white to red and reversed to white before termination. Sometimes, a greenish emission appears, which can be ascribed to HPO or (PO),. This fact shows that the chemiluminescence spectrum changes due to the concentration of phosphine. Figure 1A shows the schematic diagram for observing chemiluminescence of phosphine at high concentration. Since the supply of highly concentrated phosphine is temporal, the chemiluminescence spectrum was observed with a multiwavelength detection system. In the figure, phosphine was synthesized according to the reaction 4H3P03
heat w
l i
/
K l 102
p, ng
Flgure 5 . log-log plots of calibration curves: (upper)obtained by the no. 1 chamber in Figure 4; (middle)obtained by the no. 2 chamber in Figure 4; (bottom)obtained by the no. 3 chamber in Figure 4.
Table 11. Signals Given by Diverse Ions P
1ooa
Bi
As Se Pb
32 f 4 0.28 f 0.07 0.14 f 0.06
Sb Sn Ge
0.11 f 0.04 0.07 f 0.02 0.07 f 0.03 0.03 f 0.01
"The signal given by phosphate ion is referred to as 100. The applied chemical form of each element is noted in Experimental Section. The applied amounts of elements are 20 fig. where phosphine was injected in the ozone, needs a higher flow rate of phosphine carrier with lower flow rate of ozone for obtaining the maximum luminescence in comparison with the case of the type 3 chamber in which the carrier and ozone directly collide with each other. Figure 5 shows log-log calibration plots obtained with using the type 1, 2, and 3 chambers. Both type 1 and 3 chambers give the same detection limits of about 1 ng, and the linear dynamic ranges are from 2 to 5000 ng for the type 1 and from 10 to 5000 ng for the type 3. The type 2 chamber shows a detection limit of 3 ng with a linear dynamic range of 50-1000 ng. The narrow dynamic range of the type 2 chamber can be explained by its short length between the entrance and exhaust gases. Interferences. Table I1 shows the signal intensity when the diverse ions giving volatile hydride are applied to the present measurement, in which the signal due to 500 ng of P as phosphate ion is referred to as 100. In the table, most of elements such as Se, Pb, Bi, Sb, Sn, and Ge do not give the strong interference that As does. The present hydride generation-chemiluminescence technique is fundamentally suitable for phosphate analysis, but the selectivity against arsenic (ratio of signal intensities of P to As) is rather poor, i.e., about 3-5. In the analysis of a sample coexisting with
ANALYTICAL CHEMISTRY, VOL. 61, NO. 24, DECEMBER 15, 1989
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