USEPA Method OIA-1677: A New Approach to Cyanide Analysis

Transcription

1 USEPA Method OIA-1677: A New Approch to Cynide Anlysis Appliction Note Keywords Avilble Cynide CNLb CNSolution Cynide Method OIA-1677 Presented t the 1999 Pittsburgh Conference on Anlyticl Chemistry nd Applied Spectroscopy Orlndo, FL Mrch 7 12, 1999 Summry On July 7, 1998, the U.S. Environmentl Protection Agency (USEPA) proposed mending the Guidelines Estblishing Test Procedures for the Anlysis of Pollutnts under Section 304(h) of the Clen Wter Act by dding Method OIA-1677: Avilble Cynide by Flow Injection, Lignd Exchnge, nd Amperometry. This method employs flow injection nlysis (FIA) nd ws developed nd vlidted by ALPKEM (purchsed by OI Anlyticl in 1996) in coopertion with the University of Nevd - Reno Mcky School of Mines. According to the Federl Register notice, the USEPA considers Method OIA-1677 to be significnt ddition to the suite of nlyticl testing procedures for vilble cynide becuse it (1) hs greter specificity for cynide in mtrices where interferences hve been encountered using currently pproved methods, (2) hs improved precision nd ccurcy compred to currently pproved CATC cynide methods, (3) mesures vilble cynide t lower concentrtions, (4) offers improved nlyst sfety, (5) shortens smple nlysis time, nd (6) reduces lbortory wste. Introduction Cynide is toxic pollutnt pursunt to section 307()(1) of the Clen Wter Act (CWA) 1 nd is priority pollutnt s derived from the toxic pollutnt list. 2 Public nd privte entities subject to regultory limits for cynide menble to chlorintion (CATC) under the CWA, s well s CWA regultory uthorities, hve indicted interference problems when the currently pproved methods were used to test certin smple mtrices. During the Seventeenth Annul EPA Conference on Anlysis of Pollutnts in the Environment (My 3 5, 1994), the interference sitution ws publicized nd request ws mde for comments nd suggestions for cynide method tht reduced or eliminted these interferences. 3 At the time, ALPKEM ws working with the University of Nevd - Reno Mcky School of Mines on drmticlly simplified nd improved method for cynide nlysis. ALPKEM begn dilog with the USEPA tht rpidly developed into process whereby the new cynide method becme test vehicle for the USEPA s Stremlining Proposl. 4 Summry of Method OIA-1677 Method OIA-1677 is divided into two prts: (1) smple pretretment nd (2) cynide quntifiction vi mperometric detection. In the smple pretretment step, lignd-exchnge regents re dded to smple. The lignd-exchnge regents displce cynide ions (CN ) from wek nd intermedite strength metllo-cynide complexes. Figure 1 is representtion of the vilble cynide flow scheme.

2 In the FIA system, 200-µL liquot of the pretreted smple is injected into the flow injection mnifold. The ddition of hydrochloric cid (HCl) converts cynide ion to hydrogen cynide (HCN). The HCN diffuses through gs diffusion (GD) membrne into n lkline-receiving solution where it is converted bck to cynide ion (CN ). The mount of cynide ion in the lkline-receiving solution is mesured mperometriclly (AMP) with silver-working electrode, silver/silver chloride reference electrode, nd pltinum counter electrode t n pplied potentil of zero volts. The current generted in the cell is proportionl to the concentrtion of cynide in the originl smple, s determined by clibrtion. The nlysis time is 90 seconds per smple. BASE CARRIER PUMP FLOW INJECTION VALVE µl WASTE AMP ACID 1.0 GD WASTE Figure 1. Avilble Cynide Flow Injection Anlysis Flow Scheme Single-Lbortory Study Initilly, ALPKEM conducted single-lbortory vlidtion study in order to refine the method nd demonstrte the method s specificity nd selectivity. The results of tht study re vilble from the USEPA in the Report of the Drft Method OIA-1677 Single-Lbortory Vlidtion Study. 5 The single-lbortory study consisted of three groups of tests to estblish (1) the bility of Method OIA-1677 to mesure the cynide from vrious metllocynide complexes, (2) the bility of Method OIA-1677 to identify cynide in the presence of interferences, nd (3) the recovery nd precision of Method OIA-1677 compred to USEPA Method nd SM 4500 CN I. To determine the method s bility to mesure cynide from vrious metllo-cynide complexes, two different concentrtions (0.2 nd 2.0 mg/l) of 15 different metllo-cynide complexes were nlyzed individully in triplicte, for totl of 90 nlyses (see Tble 1). Method OIA-1677 yielded recoveries rnging from 97% to 104% for seven of the 15 complexes (zinc, cdmium, copper, silver, nickel, nd mercury). As with the currently pproved methods for vilble cynide, Method OIA-1677 did not determine cynide from the thermodynmiclly nd kineticlly stble complexes of coblt, gold, nd iron. To compre the performnce of Method OIA-1677 to the performnce of currently pproved methods, two different concentrtions of the sme 15 metllo-cynide complexes given bove were nlyzed individully in triplicte by the USEPA-pproved CATC Method SM 4500 CN I nd Method OIA This resulted in nother set of 180 dt points (see Tble 2). These results show improved recoveries nd improved precision for Method OIA-1677 compred to both the SM 4500 CN I nd the CATC methods for selected nlytes. For the mercury cynide complexes, recovery improved from 59% for SM 4500 CN I to 99% for Method OIA-1677, nd high levels of interferences in the nickel nd silver determintions showed similr improvements over the CATC method. Dt for zinc, cdmium, nd copper were comprble mong the three cynide procedures. Agin, there were no recovery differences for the thermodynmiclly nd kineticlly stble coblt, gold, or iron cynide complexes.

3 Tble 1. Species Dependent Cynide Recoveries (%) Obtined with the Flow Injection Avilble Cynide Method OIA-1677 Species mg/l CN 2.00 mg/l CN [Zn(CN) 4 )] 97.4 (0.7) 98.5 (0.7) [Cd(CN) 4 )] (0.8) (0.2) [Cu(CN) 4 ] (1.3) 99.0 (0.6) [Ag(CN) 4 ] (0.9) (0.5) [Ni(CN) 4 ] (0.2) (0.5) [Hg(CN) 4 ] (0.6) 99.0 (0.3) Hg(CN) (0.4) 98.0 (0.3) [Fe(CN) 6 ] 4 [Fe(CN) 6 ] 3 [Pd(CN) 4 ] (4.9) [Pt(CN) 4 ] [Pt(CN) 6 ] [Ru(CN) 6 ] 4 [Au(CN) 2 ] 1.3 (0.0) 0.0 [Co(CN) 6 ] b (0.0) 2.0 b (0.0) % reltive stndrd devition (n=3) is given in prentheses. b Commercil product contins some free cynide. Tble 2. Species Dependent Cynide Recoveries (%) Obtined with the ASTM WAD nd the USEPA CATC Distilltion Methods Species mg/l CN 2.00 mg/l CN WAD CATC WAD CATC [Zn(CN) 4 )] (1.9) 99.5 (0.5) (0.3) (2.6) [Cd(CN) 4 )] (1.5) (1.3) (1.8) (1.7) [Cu(CN) 4 ] (1.1) 97.7 (1.9) 96.0 (1.5) 98.0 (1.2) [Ag(CN) 4 ] 97.8 (1.6) 97.8 (1.2) 99.0 (2.7) 54.8 (2.9) [Ni(CN) 4 ] (1.2) (3.5) 97.3 (1.8) 72.0 (1.1) [Hg(CN) 4 ] 71.3 (2.5) 95.8 (2.5) 58.9 (2.6) 97.6 (3.3) Hg(CN) (9.0) 98.0 (5.9) 20.7 (7.1) 85.4 (3.8) [Fe(CN) 6 ] 4 [Fe(CN) 6 ] 3 [Pd(CN) 4 ] 32.6 (6.5) (3.0) 0.0 [Pt(CN) 4 ] [Pt(CN) 6 ] [Ru(CN) 6 ] 4 [Au(CN) 2 ] 1 [Co(CN) 6 ] b (2.9) 1.9 b (4.3) % reltive stndrd devition (n=3) is given in prentheses. b Commercil product contins some free cynide.

4 To test the bility of Method OIA-1677 to identify cynide in the presence of interfering species, 16 different possible interferents were tested t two different concentrtions (20 nd 200 mg/l) (see Tble 3). Additionlly, two different concentrtions of 16 interferents were nlyzed in triplicte for single cynide test solution, resulting in second set of 96 nlyses (see Tble 4). Even in the presence of these interferents, cynide recoveries rnged from 99% to 103% using this method. Tbles 5 nd 6 present dt of interferents nd vrious msking gents. Tbles 7 nd 8 present the dt on the sulfide interferents. Figures 2 nd 3 re clibrtion curves covering the dynmic rnge of the method. Tble 3. Response of the Avilble Cynide Method to the Presence of Possible Interferents Interfering Species Interferent Concentrtion Interferent Concentrtion 20 mg/l 200 mg/l CH 3 CHO C 6 H 12 O 6 C 3 H 8 O 3 OCl b OCN SO SCN SO 4 S 2 O Cl Br I CO 3 + NH 4 NO 2 NO 3 b In µg/l (ppb) pprent cynide. After the ddition of scorbic cid; otherwise 3 µg/l pprent cynide.

5 Tble 4. Determintion of CN by the Avilble Cynide Method in the Presence of Possible Interferents (% reltive stndrd devition (n=3) is given in prentheses) Species Rtiob CN Found (mg/l) Rtiob CN Found (mg/l) CH 3 CHO (0.5) (1.5) C 6 H 12 O (1.2) (2.5) C 3 H 8 O (2.2) (1.0) OCl OCN (0.1) 620 (0.2) SO (0.8) (7.9) SCN (0.2) (0.4) SO (1.4) (0.6) S 2 O (1.0) (0.2) Cl 73 (1.2) (2.1) Br (1.0) (0.2) I (1.2) (0.2) CO (1.2) 430 (0.6) + NH (1.7) 1440 (0.9) NO (1.0) (0.6) NO (0.4) (2.4) All smples contining mg/l CN nd 20 or 200 mg/l of the potentilly interfering species were kept in the refrigertor t 4 C for 12 hours before nlysis. b Molr concentrtion rtio: species/cn Tble 5. Response of the Avilble Cynide Method to the Presence of Possible Interferents With nd Without Interferent Tretment (% reltive stndrd devition (n=3) is given in prentheses) b Species Rtio CN Found (mg/l) Untreted Treted b CH 3 CHO (0.5) (1.1) (1.5) (1.3) OCl (0.2) SO (0.7) (0.6) (0.8) (0.7) All smples contined mg/l CN nd were refrigerted t 4 C for 12 hours prior to nlysis. With the interference removl method (for CH 3 CHO: 2 ml of 3.5% ethylene dimine solution per 100 ml of smple; for OCl nd SO 3 : 50 mg of scorbic cid per 100 ml of smple). Note: Ethylene dimine or scorbic cid ws dded within one minute fter mixing CN with the interferent.

6 Tble 6. Response of the Flow Injection/Lignd Exchnge Avilble Method to the Presence of Potentil Reductnts (% reltive stndrd devition (n=3) is given in prentheses) Smple + Reductnt 0.2 ppm CN g Sodium Arsenite 0.2 ppm CN g Sodium Arsenite 0.2 ppm CN g Sodium Arsenite 0.2 ppm CN g Ascorbic Acid 0.2 ppm CN g Ascorbic Acid 0.2 ppm CN g Ascorbic Acid 0.2 ppm CN g Oxlic Acid 0.2 ppm CN g Oxlic Acid 0.2 ppm CN g Oxlic Acid 0.2 ppm CN g Sodium Thiosulfte 0.2 ppm CN g Sodium Thiosulfte 0.2 ppm CN g Sodium Thiosulfte Molr Rtio (Red/CN ) (0.52) (0.44) (2.70) (1.79) (0.62) (0.40) (0.56) (0.38) (0.16) (0.26) (0.34) (0.64) Cynide Concentrtion (ppm) 0 h 24 h 48 h 72 h (1.56) (1.34) (0.52) (0.69) (0.16) (0.33) (0.42) (0.38) (0.18) (0.86) (0.57) (0.53) (0.26) (0.51) (1.21) (0.49) (0.10) (0.62) (0.31) (0.76) (0.18) (0.94) (0.75) (0.39) (0.62) (0.99) (0.25) (0.48) (0.58) (0.67) (0.88) (1.61) (0.48) (0.36) (0.51) (0.66) All smples were refrigerted t 4 C. Tble 7. Determintion of Cynide by the Avilble Cynide Method in the Presence of Sulfide (S ) (% reltive stndrd devition (n=3) is given in prentheses) Rtio CN Found (mg/l) CN Found (mg/l) Rtio S 2 /CN Filtered After Unfiltered S 2 /CN Filtered After Unfiltered PbCO 3 Addition for 12h PbCO 3 Addition for 12h (1.5) (0.6) 0.0 Smples contining mg/l CN nd 20 or 200 mg/l S were treted with PbCO 3 until test for S ws negtive. For filtrtion of PbS, Acrodisc 0.2-µM syringe filters were used. Smples (filtered nd unfiltered) were kept t 4 C for 12 hours before nlysis.

7 Tble 8. Recovery of Cynide by the Flow Injection/Lignd Exchnge Avilble Cynide Method in the Presence of Sulfide (S ) s Function of Time Time (hrs) Rtio S 2 /CN CN Found (mg/l) Anlyzed Immeditely After Filter Anlyzed After 12 hrs Rtio S 2 /CN CN Found (mg/l) Anlyzed Immeditely After Filter Anlyzed After 12hrs b b Smples contining mg/l CN nd 20 or 200 mg/l S were treted with PbCO 3, nd the precipitted PbS ws filtered fter 2, 4, nd 6 minutes of contct time. No cynide ws detected in the unfiltered smples nlyzed fter 12 hours indicting complete rection of CN + S to SCN. Cynide Rnge: 0 to 50 µg/l 7x10 4 (48.5; x10 4 Current (picoamperes, E-12 Amperes) 5x10 4 4x10 4 3x10 4 2x10 4 (9.7;14077 y (Current) = 1363x (CN Conc.) R^2 = x10 4 (4.85;7378 0x10 0 (0;1565) Cynide Concentrtion (µg/l) Figure 2. Avilble Cynide Clibrtion Curve for 0 to 50 µg/l

8 1x10 6 9x10 5 Cynide Rnge: 0.2 to 5 mg/l (5;971300) Current (picoamperes, E-12 Amperes) 8x10 5 7x10 5 6x10 5 5x10 5 4x10 5 3x10 5 2x10 5 1x10 5 0x10 0 (0.2;36807) (0.4;75974) (1;195382) (0.6;115113) (2;383435) (3;574798) (4;777197) y (current) = 19,427x (CN Conc.) R^2 = Cynide Concentrtion (mg/l) Figure 3. Avilble Cynide Clibrtion Curve for 0.2 to 5 mg/l Interlbortory Study The interlbortory method vlidtion study ws performed by nine lbortories, working coopertively s the WAD Cynide Round Robin Group. Ech lbortory nlyzed n identicl set of nine field smples using Method OIA These field smples were collected from nine different effluents, rnging from publicly owned tretment works (POTW) to n industry deemed likely to contin cynide in its effluent. Ech smple ws nlyzed in triplicte using the FIA procedure for totl of 243 nlyses (nine smples performed in triplicte by nine lbortories). Field smple results re presented in Tble 9. The complete study results re detiled in the report titled The Interlbortory Vlidtion of Method OIA-1677 nd re vilble from the USEPA 5. The purpose of the interlbortory study ws (1) to confirm the performnce of Method OIA-1677 in multiple lbortories, (2) to ssess Method OIA-1677 interlbortory dt vribility, nd (3) to develop Method OIA-1677 qulity control (QC) cceptnce criteri. Along with the nlysis of the field smples, ech lbortory performed ll required QC nlyses, including initil clibrtion; clibrtion verifiction; determintion of initil precision nd recovery; blnk nlysis; determintion of ongoing precision nd recovery (OPR); determintion of mtrix spike recovery nd mtrix spike duplicte recovery (MS/MSD) in ech smple type; nd ssessment of recovery of cynide s Hg(CN) 2 spiked into smples (lignd-exchnge regent performnce check or LERPC). In ddition, ech lbortory performed minimum detection level (MDL) study. The reltive stndrd devition (RSD) of results cross ll lbortories nd ll smples ws 12%. The men smple recoveries cross ll effluent types tested ws 96%, nd the MS nd MSD men recoveries were 99% cross ll effluent types tested. According to the July 7, 1998 Federl Register proposl, these results exceed the generlly ccepted norms for nlyticl chemistry results.

9 Tble 9. Avilble Cynide Recoveries From Vrious Aqueous Mtrices s Determined During the Interlbortory Study Smple Description Smple CN Concentrtion Added CN Concentrtion Averge % Recovery RSD Regent Wter with 0.01M NOH 0.0 µg/l 100 µg/l s KCN, POTW Secondry Effluent 3.0 µg/l 100 µg/l s KCN, 2 mg/l s [Pt(CN) 6 ] Petroleum Refinery Secondry Effluent 9.9 µg/l 2 mg/l s KCN, 5 mg/l s [Fe(CN) 6 ] Coke Plnt Secondry Effluent 14.0 µg/l 50 µg/l s KCN 95 4 Rolling Mill Direct Filter Effluent 4.0 µg/l None Metls Finishing Indirect Primry Effluent 1.0 µg/l 200 µg/l s KCN, 2 mg/l s KSCN Regent Wter with 0.01M NOH 0.0 µg/l 200 µg/l s KCN Regent Wter with 0.01M NOH 0.0 µg/l 10 mg/l s KCN, 10 mg/l s [Pt(CN) 6 ] Mining Tiling Pond Effluent µg/l 4 mg/l s KCN 98 3 Cyno-complexes of Pt nd Fe were dded to the POTW nd petroleum refinery effluents, respectively; thiocynte ws dded to the metls finishing effluent to demonstrte tht the cynide nlysis system does not determine these forms of cynide. Dt from the interlbortory study were used to develop QC cceptnce criteri for Method OIA The interlbortory report fully describes the lbortory procedures nd QC clcultions. The QC in Method OIA is more extensive thn tht in currently pproved methods for CATC, contining ll of the stndrdized QC tests proposed in the USEPA s stremlining inititive (62 FR 14976) nd used in the 40 CFR 136 Appendix A methods. Criteri were developed for initil precision nd recovery (IPR), ongoing precision nd recovery (OPR), nd recovery of cynide s Hg(CN) 2 spiked into regent wter smples (LERPC). QC cceptnce criteri for the IPR, OPR, MS, MSD, nd reltive percent difference (RPD) for the MS nd MSD were clculted using procedures described in the USEPA s Stremlining Guide (see Tble 10). In ddition to those procedures, QC cceptnce criteri lso were developed for Hg(CN) 2 t the upper level of the nlyticl rnge. Criteri for this LEPRC test were developed ccording to the sme procedure s the IPR test.

10 Tble 10. Avilble Cynide QC Acceptnce Criteri s Determined During the Interlbortory Study Prmeter Required Recovery Precision Rnge (%) Initil Precision nd Recovery 9122 < 5.1% RSD Ongoing Precision nd Recovery 8132 N/A Clibrtion Verifictions N/A Mtrix Spike/Mtrix Spike Duplicte 8130 < 11% RSD Nine single-lbortory MDL studies were performed s prt of the effort to determine MDLs nd minimum levels (MLs). The MDL is defined s the minimum concentrtion of substnce tht cn be mesured nd reported with 99% confidence tht the nlyte concentrtion is greter thn zero. To determine the MDL, the lbortories were required to follow the procedure in 40 CFR Prt 136, Appendix B. In the Appendix B procedure, seven liquots of regent wter re spiked with the nlyte or nlytes of interest nd nlyzed by the proposed method. For the MDL studies, KCN ws used s the spiking mteril. Spike levels were in the rnge of one to five times the estimted detection limit. Following ddition of KCN, cynide levels in ech of the seven liquots were determined. The combined MDL of ll the lbortories in the study ws determined to be 0.5 µg/l CN. A representtive single-lbortory MDL dt set is included in Tble 11. Tble 11. Single-Lbortory Determintion of Minimum Detection Level nd Minimum Level of the Avilble Cynide Method Smple Smple ID pico Amps µg/l CN Remrks Cl Cl Cl Liner Cl R = µg/l µg/l µg/l µg/l µg/l µg/l µg/l Avg 3 µg/l Stndrd Devition RSD 1.746% Minimum Detection Level = 3.14 x = 0.17 ppb Minimum Level (ML) = 3.18 x 0.17 = 0.5 ppb

11 The ML is defined s the level t which the entire nlyticl system produces recognizble signl nd n cceptble clibrtion point. The ML is determined by multiplying the MDL by 3.18 nd rounding the resulting vlue to the number nerest to [1, 2, or 5] x 10 n, where n is n integer. The ML for Method OIA-1677 ws determined to be 1.0 µg/cn. Results of the MDL studies, long with the relevnt clcultions re detiled in the interlbortory study report 5. Conclusion Method OIA-1677 demonstrtes greter specificity for cynide in mtrices where interferences hve been encountered using CATC methods. In ddition, Method OIA-1677 mesures cynide t lower concentrtions nd offers improved precision nd ccurcy over currently pproved CATC methods. This proposed method offers improved lbortory sfety nd reduces lbortory wste compred to currently pproved CATC methods nd, of prticulr note, elimintes distilltion, thereby significntly reducing the possibility of lbortory ccidents. Becuse the determintive step in Method OIA-1677 is mperometry, the chemicl regents employed for colorimetric determintions under currently pproved methods re unnecessry. This significntly reduces the genertion of hzrdous wste by the lbortory. Cynide nlysis by Method OIA-1677 is lso significntly more rpid thn by currently pproved methods. Proposl of Method OIA-1677 hs been the result of collbortive effort between OI Anlyticl nd the USEPA. It is method tht pplies the innovtive technologies of lignd exchnge, flow injection nlysis, nd mperometric detection to the determintion of vilble cynide, pollutnt regulted under the CWA. Approvl of Method OIA-1677 will llow the use of these technologies to overcome interference problems commonly encountered in the determintion of vilble cynide nd would thereby provide more relible results for complince determintions. References CFR Toxic Pollutnts CFR 423. Appendix. 3. Article by Goldberg, et l. Avilble from the USEPA Smple Control Center, 300 N. Lee Street, Alexndri, VA 22314, (703) Guide to Method Flexibility nd Approvl of EPA Wter Methods, EPA-821-D , December Avilble from the USEPA Wter Resource Center, (202) A copy of the supporting documents for Method OIA-1677 re vilble for review t the USEPA Wter Docket, 401 M Street, SW, Wshington DC For ccess to docket mterils, cll (202) between 9.m. nd 3:30 p.m. for n ppointment.

12 P.O. Box 9010 College Sttion, Texs Tel: (979) FAX: (979)