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Analysis of a selenium brightener in a silver plating solution by inductively coupled plasma emission spectrometry with hydride generation
Analysis of a Selenium Brightener in a Silver Plating Solution by Inductively Coupled Plasma Emission Spectrometry with Hydride Generation by Hye Sun Oh, Chullae Cho, and Kilnam Hwang Cheonan Research Institute, ANAM S & T, Sungsung Dong, Cheonan, Choongnam, South Korea
A
brightener is a grain-refining reagent and is present in a small concentration in silver plating solutions. The brightener is used to promote preferential deposition in valleys rather than on hills of a growing surface. Consequently, the surface roughness is reduced. Recently, a soluble selenium compound was used as a brightener in a silver plating solution.Jr' The selenium concentrations in silver plating solutions are very low, 0.3 to 0.9 ug/ml. In natural water there are numerous methods available for the measurement of total selenium concentrations and for the separation and determination of dissolved selenium species; however, for silver plating solutions many matrix interferences exist and selenium has not been reliably detected. Precipitation with La(OH)3 3. 4 has been used routinely to separate the analyte from interferences, such as Cu2+ , Ni 2+ , and Co2+ , and is used in the approach presented here. Lanthanum is added to the acid leachate as the nitrate salt, followed by ammonia solution, causing precipitation of La(OH)3' which coprecipitates many species. Elements such as Cu 2+ remain in solution, presumably as the Cu(NH 3)/ + ion. Also, it was recently shown" that using an alkaline sample solution in combination with complexing agents, such as ethylenediaminetetraacetic acid (EDTA), diethylenetriaminepentaacetic acid (DTPA), or tartrate, eliminates the interference from very high concentrations of Ni2+, C02+, Cr 3+, and Fe 3+ . Concentrations of up to 8,000 mgll, Ni2+ , or C02+ , and 5,000 mgll Cr 3+ , or Fe 3+ could be effectively masked. This method was used for the determination of selenium in nickel metal, nickel oxide, and a steel alloy." however, low sensitivity was observed for selenium in the analysis of the steel alloy. A possible explanation for the depression of the selenium signal might be that other hydride-forming elements present in the sample solution interfered with the determination/':" Mainly, the controls of a brightener are executed 12
in a Hull cell test 10 more than chemical analysis because of small concentration amount and many matrixes in a plating solution. The brightener concentration is not finely controlled by this method. For analysis of selenium brightener, La(OH)3 is used for La(OH)3-selenide precipitation in the silver plating solution, and anion exchangers are used for removing cations in the digested solution. EXPERIMENTAL
Apparatus Selenium was analyzed by ICP (Inductively Coupled Plasma-Optical Emission Spectrometer, GBC, Australia) and H2Se was formed by a hydride generator accessory. A pH meter and 0.45 IJ-m filter were used for a sample pretreatment. Reagents Selenium standard solution (standard solution for inductively coupled plasma emission spectrometer, 10,000 'YglmD, sodium borohydride (98%), and sodium hydroxide (98 %) were used for hydride generation. Hydrochloric acid and nitric acid were electronic-grade reagents. Potassium silver cyanide (99.9%), potassium cyanide (98%), buffer salts (mixture of K2HP04 , H3B03, KH2P0 4 , and KHC20 4 ) , selenium brightener [mixture of hydrazine hydrate (N2H60, 0.224 wt/vol %), sucrose (C12H220U, 0.20 wt/vol %), selenium dioxide (Se02' 0.004 wt/vol %), and additive mercaptobenzothiazole thiopropane sulfonate (ClOHlONNa03S3' 1.0 wt/vol %)] were used to make plating solution. The concentration of selenium was 28 ug/ml in the original selenium brightener solution. Lanthanum hydroxide was prepared from lanthanum nitrate hexahydrate [La(N0 3)3' 6H 20, guaranteed grade) and ammonia solution (NH 40H, guaranteed grade). Acetic acid (CH3COOH, guaranteed grade) was used for activation of the anion exchanger. The anion exchange resin used was Seppak Acell Plus QMA [-C(O)NH
ALDONEX New Low Profile Switchmode Power Supplies
rl ',ll Url 'd .ibo v« - N('w-Al d OI1l'X Sw itch rnodc power supp ly line .
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Aldonex Inc. Available Models:
Aldonex Inc. 2917 St. Charl es Rd. PO Box 148 Bellwood, IL 60104 Phone: Fax: E-mail: Web:
708- 547-5663 708-547-57 38 sa [email protected] www.aldonex.com
Max Power
Max Cu rrent
250 W 500 W 1.5 kW 2.0 kw 3.0 kw 6.0 kW 10.0 kW 15.0 kW 30.0 kw
25/\
Dimension W/D/H in.
Circle 002 on reader information card
12/11/4
50A
10/9/5
100A
10/ 12/ 6
300A
17/ 16/ 9
300A
17/1 6/ 9
1000A
18/ 18/ 11
ROOA
18/ 18/ 11
1500A
18/20/ 11
2000A
25/3 8/ 13
size <1 urn Whatman filter paper to remove any particulate. Aqueous solutions were prepared with 18.2 MO water.
Conditions of Operation Procedure for Making Artificial Silver Plating Solution A mixture of 100 gIL KAg(CN)2' 2.5 gIL KCN, 40 gIL buffer salts, 2 (v/v) % additive and 2 (v/v) % selenium brightener was used. This solution was used as a silver plating solution and allowed control of concentrations of various components of the solution. Conditions for Inductively Coupled Plasma Emission Spectrometry and Hydride Generation Parameters of inductively coupled plasma emission spectrometer were forward power: 1.25 kW; sample gas flow rate: 0.4 Umin; viewing height: 10.01 mm; nebulizer pressure: 6 kPa; wavelength: 196.090 nm; gas: Ar (99.999 %). Selenium was found to have very high sensitivity when the concentration of the reducing agent (NaBH 4) was 1 wt.lv % in 1 wt./v % NaOH solution. NaBH4 stock solution was only good for five days. Selenium also gave high sensitivity when the sample solution was acidified to 2.5 M in HCl. Activation ofAnion Exchange Resins and Cation Separation from the Selenium Solution The anion exchange resin (- N(NH 3)3 + functional group) was consecutively rinsed with 10 ml of deionized water, 10 ml of 3 M HCI solution, 20 ml of deionized water, 10 ml of3 M acetic acid solution, 20 ml of deionized water, 10 ml of acetate buffer (pH 2.6-3.0), and finally 10 ml of deionized water. Then 10 to 30 ml of pretreated sample was applied to the activated anion exchanger. The resin was then washed with 10 ml of deionized water. Selenium compounds were eluted with 10 to 30 ml of 3 M HCI solution"! (rinse flow rate: 1-2 ml/min; eluent flow rate: 0.5 mVmin; sample flow rate: 0.5-1 ml/min). Selenium compounds are concentrated in the eluted volume of 3 M HCl. Pretreatment for Selenium Analysis in the Silver Plating Solution It is known that selenium has the selenide form in the alkaline silver plating solution.f Thompson et al. reported that iron (III) hydroxide or lanthanum hydroxide (lanthanum nitrate hexahydrate + ammonia solution: pH 9.0-9.5) can be utilized for selenium (IV, VI) coprecipitation.P Iron hydroxide only coprecipitates with selenium (IV), and both selenium (IV) and selenium (VI) are coprecipitated with lanthanum hydroxide (lanthanum nitrate hexahydrate + ammonia solution: pH 9.0-9.5).13 Selenium 14
(IV) has a higher sensitivity detection than selenium (VI) by inductively coupled plasma emission spectrometry with hydride generation. Also, Bleakley et al. reported that selenium was precipitated in a colloidal form with lanthanum at pH 2.9, and the coprecipitation effect was gratifiable over the range pH 9 to 10. 14 The recovery of selenium has been found to depend on the concentration of lanthanum hydroxide and the pH of the silver plating solution. It was anticipated that the selenium compound might be easily precipitated with the lanthanum at low pH. So, simultaneous use of both methods was attempted: added lanthanum hydroxide for coprecipitation with selenium and HN03 solution for making +4 or +6 oxidation state. High recovery of selenium was obtained with -0.026 M CO.5g/10 ml) of lanthanum hydroxide in the silver plating solution. At these conditions the excess added lanthanum hydroxide did not contribute to coprecipitation of selenium and did not affect the selenium analysis by inductively coupled plasma emission spectrometry with hydride generation.P Pretreatment of the silver plating solution was carried out using the following procedure. First, the silver plating solution was cooled to O°C for an hour and filtered (to eliminate potassium salts of oversaturated co,>, HP0 42-, H 2B0 3-, and Ag(CN)2- precipitating) before addition of 0.5 g lanthanum hydroxide into 100 ml silver plating solution. The 25 ml of HN03 was slowly added to the silver plating solution with stirring over 30 minutes. The solution was about pH 2 at this and was filtered before digestion. The precipitate was composed of selenium coprecipitated with lanthanum, AgCN, and metal cyanide. Five ml of concentrated HCI solution was added to the precipitate, and the slurry was heated at 95°C for 30 minutes. The digested solution was cooled to room temperature, filtered, and then separated selenide from cations by using anions exchanger to eliminate the other metals reacting with NaBH 4 when H 2Se is formed. Row selenium recovery resulted by reaction with NaBH4 and cations (Cu++, Ni++ etc).16 Metal impurities, such as Cu and Ni, were present at -2,500 ug/ml and 2,000 f.1g1ml respectively in the pretreatment solution before using anions exchanger. RESULTS AND DISCUSSION
Selenium Analysis Without Metal Impurities Matrix interferences were investigated in silver plating solution based on their effect on selenium recovery. The silver plating solution was treated with 25 ml of HN03, filtered, and the filtrate anaMetal Finishing
-
100 r-
~
III
III
o o
o6 60
~ 40
o
1
2
3
5
Sample Number
6
7
lyzed. All samples were prepared in a 100 ml volumetric flask and contents of component were 10 g KAg(CN)2' 0.25 g KCN, 2 ml additive, 4 g buffer salts, and 4 ml selenium brightener (about 1.2 ug/ml selenium). Potassium silver cyanide had the highest matrix effect. Figure 1 shows the matrix effect when the solution contained all components, and the solution containing selenium brightener only, were chosen as base line and 100%, respectively. But selenium recovery was low under this pretreatment condition although selenium brightener was only contained in the solution. The fact can be explained that selenium is not perfectly changed selenite (HSe0 3 or SeO/ ) or selenate (HSe0 4 or Se0 4 2 - ) 17 and is volatilized. Figure 2 shows the effect of coprecipitation for selenium analysis. It does not effect the pretreatment of anion exchange resin because impurities aren't present in the artificial silver plating solution.
Selenium Analysis Solution Containing Metal Impurities We artificially prepared a silver plating solution for use as a standard solution. The standard solution and the line solution were pretreated by the same method. The detection limit of selenium was about 0.5 ug/ml in the line silver plating solution. Selenium recovery was low because coprecipitation is not efficient and selenium volatilizes in the acid pretreatment in the plating solution. Figure 3 shows the sensitivity of the spectrum of inductively cou-
..
....
........... . .... ..- •..........•.......
...
r"
•......-... •....
o
8
Figure 1. Mixture solutions for the matrix effect of artificial silver plating solution. ((1)KAg(CNIz + KCN + selenium brightener; (2) KAg(CNIz + KCN + additive + selenium brightener; (3) KAg(CN)2 + KCN + additive + buffer salts + selenium bright· ener; (4) KAg(CNIz + KCN + buffer salts + selenium brightener; (5) additive + buffer salts + selenium brightener; (6) buffer salts + selenium brightener; (7) additive + selenium brightener; (8) selenium brightener]. The contents of component were 10 9 KAg(CNIz. 0.25 g KCN. 2 ml additive. 4 g buffer salts. and 4 ml selenium brightener (about 1.2 ILg/ml selenium) in 100 mlvolumetric flask. It was dissolved and filled with deionized water to the mark.
October 2000
.............
~
n 4
, ,' "'~
!
...-
UlJL
So ........ ""'::::::-',•••••
C ::::I
r-
C
~ 20
}.16_,. 'ep
-
!! 80
2
6 10 14 18 Selenium Brighlener«vol'/vol.) %)
22
Figure 2. Comparison coprecipitation. (e: on IX acid pretreatment; .: coprecipitation; .: anion exchanger usmg after coprecipitation).
pled plasma emission spectrometry with hydride generation of about 0.5 ug/ml in selenium analysis of the line silver plating solution by this method. Control of selenium brightener by this analysis method can be accepted although selenium brightener is at - 2 to 3 v/v o/c in the silver plating solution. This pretreatment condition can be usefully applied by selenium analysis method of the line silver plating solution. CONCLUSION
The selenium analysis method for a silver plating solution containing matrix interferences was studied by inductively coupled plasma emission spectrometry with hydride generation. The detection limit for selenium was about 0.5 ug/ml in the following procedure, La(OH):1 was added to the silver plating solution, followed by HNO a (thereby precipitated AgCN) and coprecipitating La(OHl:l-selenide. These were digested, and cations in the digest solution
13317.
..
§
o II
""r- ~ 1~
6658.
c
G
e.eeeL--'----'--..........--::7':::""-~-"'-----'----;l-;;;96.I!lll 196.0!lll 195.9!lll
WavelengU(nm) Figure 3. Spectrum of inductively coupled plasma emission spectrometry with hydride generation of abo~t 0.5 yg/ml selenium in the silver plating line solution analySIS.
15
were removed by an anion exchange column before selenium analysis. Potassium silver cyanide appeared to give the highest matrix effect from the main components of the silver plating solution. BIOGRAPHIES
Hye Sun Oh holds a BS from Cheonan National Technical College. She is with the Chemical Analysis Research Team of Cheonan Research Institute ANAM S&T Co. Ltd. Chullae Cho is a Senior Researcher and a leader of Chemical Analysis Research Team of Cheonan Research Institute ANAM S&T Co. Ltd. He holds a PhD from Seoul National University. Kilnam Hwang is the Manager of Chemical & Material Research Group of Cheonan Research Institute ANAM S&T Co. Ltd. He received a PhD in electrochemistry from Seoul National University. REFERENCES
1. Harshaw, W.J. et aI., U.S. Patent, 2,125,229; 1938 2. Ostrow, B.D., U. S. Patent, 2,777,810; 1957
3. Aslin, G.E.M., J. Geochem. Explor., 6:321; 1976 4. Bedard, M. and J.D. Kerbyson, Anal. Chem., 47:1441; 1975 5. Wickstrom, T. et al., J. Anal. At. Spectrom., 10:803; 1995 6. Meyer, A. et al., Fresenius'Z. Anal. Chem., 296: 337; 1979 7. Verlinden, M. and H. Deelstra, Fresenius'Z. Anal. Chem., 296:253; 1979 8. Dedina, J., Anal. Chem., 54:2097; 1982 9. Welz, B. and P. Stauss, Spectrochim. Acta, Part B, 48:951; 1993 10. Lowenheim, FA, "Modern Electroplating," John Wiley & Sons, New York, p. 568; 1974 11. Adeloju, S.B. et al., Anal. Chem., 55:2076; 1983 12. Thompson, M.B. et aI., Water Res., 15:407; 1981 13. Nakashima, S., Analytical Chemistry, 51:654; 1979 14. Reichel, W. and B.G. Bleakley, Analytical Chemistry, 46:59; 1974 15. Tao, G. and E.H. Hansen, Analyst, 119:333; 1994 16. Thompson, M. et al., Analyst, 103:705; 1978 17. Nygaard, D.D. and J.H. Lowry, Anal. Chem., 54:803; 1982 MF
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GEORGE FISCHER +GF+ Circle 025 on reader information card
16
Metal Finishing
A
brightener is a grain-refining reagent and is present in a small concentration in silver plating solutions. The brightener is used to promote preferential deposition in valleys rather than on hills of a growing surface. Consequently, the surface roughness is reduced. Recently, a soluble selenium compound was used as a brightener in a silver plating solution.Jr' The selenium concentrations in silver plating solutions are very low, 0.3 to 0.9 ug/ml. In natural water there are numerous methods available for the measurement of total selenium concentrations and for the separation and determination of dissolved selenium species; however, for silver plating solutions many matrix interferences exist and selenium has not been reliably detected. Precipitation with La(OH)3 3. 4 has been used routinely to separate the analyte from interferences, such as Cu2+ , Ni 2+ , and Co2+ , and is used in the approach presented here. Lanthanum is added to the acid leachate as the nitrate salt, followed by ammonia solution, causing precipitation of La(OH)3' which coprecipitates many species. Elements such as Cu 2+ remain in solution, presumably as the Cu(NH 3)/ + ion. Also, it was recently shown" that using an alkaline sample solution in combination with complexing agents, such as ethylenediaminetetraacetic acid (EDTA), diethylenetriaminepentaacetic acid (DTPA), or tartrate, eliminates the interference from very high concentrations of Ni2+, C02+, Cr 3+, and Fe 3+ . Concentrations of up to 8,000 mgll, Ni2+ , or C02+ , and 5,000 mgll Cr 3+ , or Fe 3+ could be effectively masked. This method was used for the determination of selenium in nickel metal, nickel oxide, and a steel alloy." however, low sensitivity was observed for selenium in the analysis of the steel alloy. A possible explanation for the depression of the selenium signal might be that other hydride-forming elements present in the sample solution interfered with the determination/':" Mainly, the controls of a brightener are executed 12
in a Hull cell test 10 more than chemical analysis because of small concentration amount and many matrixes in a plating solution. The brightener concentration is not finely controlled by this method. For analysis of selenium brightener, La(OH)3 is used for La(OH)3-selenide precipitation in the silver plating solution, and anion exchangers are used for removing cations in the digested solution. EXPERIMENTAL
Apparatus Selenium was analyzed by ICP (Inductively Coupled Plasma-Optical Emission Spectrometer, GBC, Australia) and H2Se was formed by a hydride generator accessory. A pH meter and 0.45 IJ-m filter were used for a sample pretreatment. Reagents Selenium standard solution (standard solution for inductively coupled plasma emission spectrometer, 10,000 'YglmD, sodium borohydride (98%), and sodium hydroxide (98 %) were used for hydride generation. Hydrochloric acid and nitric acid were electronic-grade reagents. Potassium silver cyanide (99.9%), potassium cyanide (98%), buffer salts (mixture of K2HP04 , H3B03, KH2P0 4 , and KHC20 4 ) , selenium brightener [mixture of hydrazine hydrate (N2H60, 0.224 wt/vol %), sucrose (C12H220U, 0.20 wt/vol %), selenium dioxide (Se02' 0.004 wt/vol %), and additive mercaptobenzothiazole thiopropane sulfonate (ClOHlONNa03S3' 1.0 wt/vol %)] were used to make plating solution. The concentration of selenium was 28 ug/ml in the original selenium brightener solution. Lanthanum hydroxide was prepared from lanthanum nitrate hexahydrate [La(N0 3)3' 6H 20, guaranteed grade) and ammonia solution (NH 40H, guaranteed grade). Acetic acid (CH3COOH, guaranteed grade) was used for activation of the anion exchanger. The anion exchange resin used was Seppak Acell Plus QMA [-C(O)NH
ALDONEX New Low Profile Switchmode Power Supplies
rl ',ll Url 'd .ibo v« - N('w-Al d OI1l'X Sw itch rnodc power supp ly line .
Wp sq uer-zr-d high perfor rnanr e components into a lightw eight and thin package w ith a 200 0A 15V po w e-r supp ly w eighing in at 2h5 Ibs! These remarkable new Switchmod e pOWN sup plies have everything yo u've hr-en look in g for : Wa ll mount abl e, rack mount abl e or stand alo ne floor mod els. Heavy duty co nstruc tio n for industrial app li catio ns. Automatic Vol tage and Current control. < 1'X, rippl e throu ghout iu ll r,mge. Shor t circuit pro tectio n. PLC control wit h netw ork ing abi li ty for up to 200 powe r supplir« . Built in over current and over temperature protect ion . 100'%. dut v cycle . Powde r coa ted e nrlosurr- . \\'('11 protected from corros io n. Availab le w ith pol arit y reverse. CE approved.
Aldonex Inc. Available Models:
Aldonex Inc. 2917 St. Charl es Rd. PO Box 148 Bellwood, IL 60104 Phone: Fax: E-mail: Web:
708- 547-5663 708-547-57 38 sa [email protected] www.aldonex.com
Max Power
Max Cu rrent
250 W 500 W 1.5 kW 2.0 kw 3.0 kw 6.0 kW 10.0 kW 15.0 kW 30.0 kw
25/\
Dimension W/D/H in.
Circle 002 on reader information card
12/11/4
50A
10/9/5
100A
10/ 12/ 6
300A
17/ 16/ 9
300A
17/1 6/ 9
1000A
18/ 18/ 11
ROOA
18/ 18/ 11
1500A
18/20/ 11
2000A
25/3 8/ 13
size <1 urn Whatman filter paper to remove any particulate. Aqueous solutions were prepared with 18.2 MO water.
Conditions of Operation Procedure for Making Artificial Silver Plating Solution A mixture of 100 gIL KAg(CN)2' 2.5 gIL KCN, 40 gIL buffer salts, 2 (v/v) % additive and 2 (v/v) % selenium brightener was used. This solution was used as a silver plating solution and allowed control of concentrations of various components of the solution. Conditions for Inductively Coupled Plasma Emission Spectrometry and Hydride Generation Parameters of inductively coupled plasma emission spectrometer were forward power: 1.25 kW; sample gas flow rate: 0.4 Umin; viewing height: 10.01 mm; nebulizer pressure: 6 kPa; wavelength: 196.090 nm; gas: Ar (99.999 %). Selenium was found to have very high sensitivity when the concentration of the reducing agent (NaBH 4) was 1 wt.lv % in 1 wt./v % NaOH solution. NaBH4 stock solution was only good for five days. Selenium also gave high sensitivity when the sample solution was acidified to 2.5 M in HCl. Activation ofAnion Exchange Resins and Cation Separation from the Selenium Solution The anion exchange resin (- N(NH 3)3 + functional group) was consecutively rinsed with 10 ml of deionized water, 10 ml of 3 M HCI solution, 20 ml of deionized water, 10 ml of3 M acetic acid solution, 20 ml of deionized water, 10 ml of acetate buffer (pH 2.6-3.0), and finally 10 ml of deionized water. Then 10 to 30 ml of pretreated sample was applied to the activated anion exchanger. The resin was then washed with 10 ml of deionized water. Selenium compounds were eluted with 10 to 30 ml of 3 M HCI solution"! (rinse flow rate: 1-2 ml/min; eluent flow rate: 0.5 mVmin; sample flow rate: 0.5-1 ml/min). Selenium compounds are concentrated in the eluted volume of 3 M HCl. Pretreatment for Selenium Analysis in the Silver Plating Solution It is known that selenium has the selenide form in the alkaline silver plating solution.f Thompson et al. reported that iron (III) hydroxide or lanthanum hydroxide (lanthanum nitrate hexahydrate + ammonia solution: pH 9.0-9.5) can be utilized for selenium (IV, VI) coprecipitation.P Iron hydroxide only coprecipitates with selenium (IV), and both selenium (IV) and selenium (VI) are coprecipitated with lanthanum hydroxide (lanthanum nitrate hexahydrate + ammonia solution: pH 9.0-9.5).13 Selenium 14
(IV) has a higher sensitivity detection than selenium (VI) by inductively coupled plasma emission spectrometry with hydride generation. Also, Bleakley et al. reported that selenium was precipitated in a colloidal form with lanthanum at pH 2.9, and the coprecipitation effect was gratifiable over the range pH 9 to 10. 14 The recovery of selenium has been found to depend on the concentration of lanthanum hydroxide and the pH of the silver plating solution. It was anticipated that the selenium compound might be easily precipitated with the lanthanum at low pH. So, simultaneous use of both methods was attempted: added lanthanum hydroxide for coprecipitation with selenium and HN03 solution for making +4 or +6 oxidation state. High recovery of selenium was obtained with -0.026 M CO.5g/10 ml) of lanthanum hydroxide in the silver plating solution. At these conditions the excess added lanthanum hydroxide did not contribute to coprecipitation of selenium and did not affect the selenium analysis by inductively coupled plasma emission spectrometry with hydride generation.P Pretreatment of the silver plating solution was carried out using the following procedure. First, the silver plating solution was cooled to O°C for an hour and filtered (to eliminate potassium salts of oversaturated co,>, HP0 42-, H 2B0 3-, and Ag(CN)2- precipitating) before addition of 0.5 g lanthanum hydroxide into 100 ml silver plating solution. The 25 ml of HN03 was slowly added to the silver plating solution with stirring over 30 minutes. The solution was about pH 2 at this and was filtered before digestion. The precipitate was composed of selenium coprecipitated with lanthanum, AgCN, and metal cyanide. Five ml of concentrated HCI solution was added to the precipitate, and the slurry was heated at 95°C for 30 minutes. The digested solution was cooled to room temperature, filtered, and then separated selenide from cations by using anions exchanger to eliminate the other metals reacting with NaBH 4 when H 2Se is formed. Row selenium recovery resulted by reaction with NaBH4 and cations (Cu++, Ni++ etc).16 Metal impurities, such as Cu and Ni, were present at -2,500 ug/ml and 2,000 f.1g1ml respectively in the pretreatment solution before using anions exchanger. RESULTS AND DISCUSSION
Selenium Analysis Without Metal Impurities Matrix interferences were investigated in silver plating solution based on their effect on selenium recovery. The silver plating solution was treated with 25 ml of HN03, filtered, and the filtrate anaMetal Finishing
-
100 r-
~
III
III
o o
o6 60
~ 40
o
1
2
3
5
Sample Number
6
7
lyzed. All samples were prepared in a 100 ml volumetric flask and contents of component were 10 g KAg(CN)2' 0.25 g KCN, 2 ml additive, 4 g buffer salts, and 4 ml selenium brightener (about 1.2 ug/ml selenium). Potassium silver cyanide had the highest matrix effect. Figure 1 shows the matrix effect when the solution contained all components, and the solution containing selenium brightener only, were chosen as base line and 100%, respectively. But selenium recovery was low under this pretreatment condition although selenium brightener was only contained in the solution. The fact can be explained that selenium is not perfectly changed selenite (HSe0 3 or SeO/ ) or selenate (HSe0 4 or Se0 4 2 - ) 17 and is volatilized. Figure 2 shows the effect of coprecipitation for selenium analysis. It does not effect the pretreatment of anion exchange resin because impurities aren't present in the artificial silver plating solution.
Selenium Analysis Solution Containing Metal Impurities We artificially prepared a silver plating solution for use as a standard solution. The standard solution and the line solution were pretreated by the same method. The detection limit of selenium was about 0.5 ug/ml in the line silver plating solution. Selenium recovery was low because coprecipitation is not efficient and selenium volatilizes in the acid pretreatment in the plating solution. Figure 3 shows the sensitivity of the spectrum of inductively cou-
..
....
........... . .... ..- •..........•.......
...
r"
•......-... •....
o
8
Figure 1. Mixture solutions for the matrix effect of artificial silver plating solution. ((1)KAg(CNIz + KCN + selenium brightener; (2) KAg(CNIz + KCN + additive + selenium brightener; (3) KAg(CN)2 + KCN + additive + buffer salts + selenium bright· ener; (4) KAg(CNIz + KCN + buffer salts + selenium brightener; (5) additive + buffer salts + selenium brightener; (6) buffer salts + selenium brightener; (7) additive + selenium brightener; (8) selenium brightener]. The contents of component were 10 9 KAg(CNIz. 0.25 g KCN. 2 ml additive. 4 g buffer salts. and 4 ml selenium brightener (about 1.2 ILg/ml selenium) in 100 mlvolumetric flask. It was dissolved and filled with deionized water to the mark.
October 2000
.............
~
n 4
, ,' "'~
!
...-
UlJL
So ........ ""'::::::-',•••••
C ::::I
r-
C
~ 20
}.16_,. 'ep
-
!! 80
2
6 10 14 18 Selenium Brighlener«vol'/vol.) %)
22
Figure 2. Comparison coprecipitation. (e: on IX acid pretreatment; .: coprecipitation; .: anion exchanger usmg after coprecipitation).
pled plasma emission spectrometry with hydride generation of about 0.5 ug/ml in selenium analysis of the line silver plating solution by this method. Control of selenium brightener by this analysis method can be accepted although selenium brightener is at - 2 to 3 v/v o/c in the silver plating solution. This pretreatment condition can be usefully applied by selenium analysis method of the line silver plating solution. CONCLUSION
The selenium analysis method for a silver plating solution containing matrix interferences was studied by inductively coupled plasma emission spectrometry with hydride generation. The detection limit for selenium was about 0.5 ug/ml in the following procedure, La(OH):1 was added to the silver plating solution, followed by HNO a (thereby precipitated AgCN) and coprecipitating La(OHl:l-selenide. These were digested, and cations in the digest solution
13317.
..
§
o II
""r- ~ 1~
6658.
c
G
e.eeeL--'----'--..........--::7':::""-~-"'-----'----;l-;;;96.I!lll 196.0!lll 195.9!lll
WavelengU(nm) Figure 3. Spectrum of inductively coupled plasma emission spectrometry with hydride generation of abo~t 0.5 yg/ml selenium in the silver plating line solution analySIS.
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were removed by an anion exchange column before selenium analysis. Potassium silver cyanide appeared to give the highest matrix effect from the main components of the silver plating solution. BIOGRAPHIES
Hye Sun Oh holds a BS from Cheonan National Technical College. She is with the Chemical Analysis Research Team of Cheonan Research Institute ANAM S&T Co. Ltd. Chullae Cho is a Senior Researcher and a leader of Chemical Analysis Research Team of Cheonan Research Institute ANAM S&T Co. Ltd. He holds a PhD from Seoul National University. Kilnam Hwang is the Manager of Chemical & Material Research Group of Cheonan Research Institute ANAM S&T Co. Ltd. He received a PhD in electrochemistry from Seoul National University. REFERENCES
1. Harshaw, W.J. et aI., U.S. Patent, 2,125,229; 1938 2. Ostrow, B.D., U. S. Patent, 2,777,810; 1957
3. Aslin, G.E.M., J. Geochem. Explor., 6:321; 1976 4. Bedard, M. and J.D. Kerbyson, Anal. Chem., 47:1441; 1975 5. Wickstrom, T. et al., J. Anal. At. Spectrom., 10:803; 1995 6. Meyer, A. et al., Fresenius'Z. Anal. Chem., 296: 337; 1979 7. Verlinden, M. and H. Deelstra, Fresenius'Z. Anal. Chem., 296:253; 1979 8. Dedina, J., Anal. Chem., 54:2097; 1982 9. Welz, B. and P. Stauss, Spectrochim. Acta, Part B, 48:951; 1993 10. Lowenheim, FA, "Modern Electroplating," John Wiley & Sons, New York, p. 568; 1974 11. Adeloju, S.B. et al., Anal. Chem., 55:2076; 1983 12. Thompson, M.B. et aI., Water Res., 15:407; 1981 13. Nakashima, S., Analytical Chemistry, 51:654; 1979 14. Reichel, W. and B.G. Bleakley, Analytical Chemistry, 46:59; 1974 15. Tao, G. and E.H. Hansen, Analyst, 119:333; 1994 16. Thompson, M. et al., Analyst, 103:705; 1978 17. Nygaard, D.D. and J.H. Lowry, Anal. Chem., 54:803; 1982 MF
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