DBPIA-NURIMEDIA

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1 Printed in the Republic of Korea "/"-:5*$"- 4$*&/$& 5&$)/0-0(: Vol. 18, No. 5, , 2005» 677*4 Ÿ w sƒ ½»x Á Á½ k w y w, w y œw Some considerations for the analytical approaches to measure atmospheric ammonia: tests on a relative performance of a portable colorimeter against UV/VIS spectrophotometer K. H. Kim, S. Y. Park and S. T. Kim 1 Dept. of Earth & Environmental Sciences, Sejong University 1 Dept. of Environmental and Life Engineering, Daejeon University (Received June 9, 2005, Accepted August 24, 2005) :» d y w UV/VIS Ÿ w sƒw. ƒ l w w, x,, y» w w w. w, UV/VIS Ÿ yw e. w sƒw ƒ l 3μg ƒà ùkû. ù, û š w ùkû., 10 μg w x w ƒ š, 100 μg š w w.» 30 l w š ƒ w, ( ƒw š w ) 500 ppb 5 ppm w zw ùkû. w p wš w, y w yw w ƒ w ü. Abstract : In this study, we investigated the performance of a portable colorimeter used for the measurements of atmospheric ammonia against the more reliable method like UV/VIS spectrophotometer. For the purpose of this study, we tested a portable colorimeter and UV/VIS spectrophotometer for such basic analytical parameters as detectibility, reproducibility, linearity, and accuracy. According to our study, the performance of the colorimeter was fairly good to show a good agreement with the UV/VIS system. However, the performance of colorimeter suffered from both low and high concentration ranges: it was found to have very poor reproducibility at lower concentration (below 10 μg), while its linear dynamic range was limited at the upper end (e.g., near 100 μg). Corresponding author Phone : +82-(0) Fax : +82-(0) khkim@sejong.ac.kr 425

2 426 ½»xÁ Á½ k If we assume that air samples are collected up to 30 liter, it implies that the colorimeter can be used to measure samples containing NH 3 in the range of 500 ppb to 5 ppm (without the aid of diluting technique). Consequently, we recommend the use of such instrument with the awareness of its basic properties pertaining to the fundamental performance (such as its detectable range). Key words: atmospheric, ammonia, colorimeter, UV/VIS spectrophotometer, performance test»y w û ppb ( w) l ppm ƒ. 1,2 w, y» ppt û y ƒ w t. w ƒ 0.5 ppm š w t š w. yy ù œ w mw. 3-6 w ƒ» w w. z w w» w, ƒ w»»» w v» š. 7,8» w w. x v š. d w œ x r y w y. Ÿ y w sx,, sx. 9,10 r r - p v ùp ùp ƒwš, w w r Ÿ d w w. 20(unitƒ v ex) ml )», ƒ 1 ppm ww w w. 10 ppm, ƒ g w» w. w w ƒ w ( y 100,, y ƒ 10, y y ) w, ƒ w y ƒ w š. 11 w» y w» w» w, ƒ rw y w ƒx yw p w wš w. w, ƒ r y w w UV/VIS Ÿ» wš ƒ ww. mw ƒx y ƒ p w sƒwš w. r» w» w, ƒ x»» sƒwš w. p sƒ w» y w» w, r w t w ƒ w, ƒ sƒw.»» w y œw w { (Fig. 1)»» wš w. d w ƒ w w., w š n j s w» k(blank level) wš, x m w w s w Ÿ m w Ÿ d w. d Ÿ l mw t, t w w ƒ w. w { s ( Analytical Science & Technology

3 » : UV/VIS Ÿ w sƒ 427 Fig. 1. A schematic diagram of the portable colorimeter investigated in this study. ), Ÿ, Ÿ, ú t 4 w. Ÿ w w m Ÿ š m Ÿ w w. d Ÿ ƒ yw w Ÿ w w z mw. w w Ÿ Hewlett Packard M.I. USA HP8453 w. UV l ü e q nm, Beam mode double beam, 1 nm bandwidth, 0.05 % w stray light.» k(blank level) 10 mm-3 ml Cuvett Beam n w w. Ÿd» k 635~640 nm q. w ww» w r» w., 3ƒ x (, r - p t ùp, ùp ) wš, y w t t ƒƒ w z w. p t w 44.7 mm y 100, 50, 10, 3.3, 1 w y w. x ƒƒ t r - p t ùp ùp w v w y w. sƒw» w, w k w ƒ d w w. p, w,,» yw sƒ w. š k, ƒ» y w w w sƒ w. w» ƒ wš w. m w ƒ l sƒw» w» œ x w protocol ww. ƒ w Table 1 w ƒ w t w w y w. ƒ¾» w, ƒ¾ ƒ w w. š w t r 3 w, w w.»»» 3,000 ng ƒ¾ w» w (Table 1)., 30 l œ» m k š w,»» UV/VIS 132 ppb, š 155 ppb w w ùkû. Table 1. Comparison of detection limits (DL) between two different measurement techniques: a portable colorimeter (COL) and UV/VIS spectrophotometer DL COL a UV-VIS b ng ppb c Superscripts a and b denote colorimeter and UV-VIS spectrophotometry, respectively. Superscript c implies that the sampling volume of 30 L was assumed. Vol. 18, No. 5, 2005

4 428 ½»xÁ Á½ k Table 2. Calculation of precision (reproducibility) between the two systems. Test is made at two different concentration levels of low and high 1. Calculation at low concentration (7,548 ng) Reading scale Absolute mass (ng) Sample No. COL a UV-VIS b COL UV-VIS Mean Table 3. Comparison of linearity range of ammonia analysis between the two systems Order Analyte (ng) COL Reading UV-VIS NM NM NM *NM= not measurable RSD (%) c Calculation at high concentration (75,480 ng) Reading scale Absolute mass (ng) Sample No. COL UV-VIS COL UV Mean RSD (%) c For superscripts a and b, refer to Table 1. Superscript c denotes the relative standard deviation. ƒ l w w w ùkû. x ƒ x sƒw» w Table 2 ƒ w w. 7,548 ng š 75,480 ng w. x t r (relative standard deviation (RSD)=(SDÜ100)/Mean) w,»» l ü w w. š x 4% UV/VIS 6% w w Fig. 2. Calibration curves obtained by the colorimeter (upper) and UV/VIS method (lower).., l ƒ x w. UV/VIS, š w x w 7% ùkù» w x w., x 30%, x w y. x w w. Analytical Science & Technology

5 » : UV/VIS Ÿ w sƒ 429 l ƒ sƒw» w, w v ƒ. Table 3 Fig. 2 w w. w w ƒ¾ 3μg l 120 ƒ j 377 μg ¾ w. w, w ƒ ùkù y w. 150 μg ùkû. UV/VIS, w 377 μg¾ w, w ƒ y w. y w sƒ sƒw» w w ƒ» y w sƒ wš w. ù w sƒ w w» w w. 30 o C 496 ng w r p (VICI Metronics, CA, USA) w, ƒ w. w t ƒ 500 ml/min w, 10, 25, 45, 60, 95 m g. mw (ng) (ppb) Table 4 w. k w z, ƒ w ƒ w. Table 4 w w w ƒ w w. x ù sƒ y w ƒ w ùkû. ƒ 4,960 ng dw ƒ 38% j ùkû. š ƒ ƒw, l w ew w ƒ ùkù y w. sƒw» w r ywš y UV/VIS Ÿ w x ww. w, ƒ» x š w w, x,, y w. w, yw w y w. w w œ w ùkû, x x w ùkû. š w, w ƒ x w., μg z ƒ w y w. 30 l œ» k š ƒ w, j 500 ppb~5 ppm ƒ ww ü ƒ w. w w w x w, w w y w. Table 4. Evaluation of relative accuracy of colorimetery method by checking against the UV-visible spectrophotometer Theoretic values a Measured concentrations Order ng ppb Ratio b ng ppb COL UV/VIS COL UV/VIS C/U Superscript a denotes the theoretical values for NH 3 concentrations computed by considering the permeation rate at fixed flow rate. Superscript b denotes the NH 3 concentration ratio determined between COL (c) and UV-VIS (u). Vol. 18, No. 5, 2005

6 430 ½»xÁ Á½ k ƒ w y w. š x 1. K. H. Kim, Performance characterization of the GC/ PFPD for H 2 S, CH 3 SH, DMS, and DMDS in air Atmospheric Environment, 39(12), (2005). 2. K.-H. Kim, Y.-J. Choi, E.-C. Jeon and Y. Sunwoo, Characterization of malodorous sulfur compounds in landfill gas Atmospheric Environment, 39(6), (2005). 3. ½»x,,, y, y, y,,, w y» {» yw y d w»y wz, 21(2), (2005a). 4. ½»x,, y, y, y,,,, œ ü» w p w w»y wz, 21(2), (2005b). 5., œ» w üw œ w w ý y wz, 2(1), 32-37(2003). 6. z, ½ k,, y, w w ý y wz, 3(4), (2004). 7. y, ½»x,» e» : s w DNPH p w wz, 18(1), 42-49(2005). 8., ( š ) y (2003). 9.,, «,, x, y œ w d ( š )., y (2001). 10. x, ½, r w w : sx,, sƒ w y wz, 4(1) 92(1994) 11. ½, y w w œ w (2003). Analytical Science & Technology