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HDH TECHhJUL06IE'S IIJC . TEL ~ ~0 -792-~53' May ~ ~4 9L' S ~ 1 3 No .004 P .0
<br />~. ~` • ANALYTICAL CHEM~, VOL. 83, N0. ,APRIL 1, 1981 • 698
<br />' •ai on which the EPA has eat the regulatory limits (4). Copilnp Fan
<br />....il cyanide =
<br />free cyanide + week metal cyanide + CNATC (1)
<br />Current EPA methods for cyanide determination, while t2 cm cork nap
<br />generally successful in species diffesetrtiation, are lengthy and aempia
<br />labor inteirsivs. Tyre detection limits of these mothode are out
<br />ofton too high W provide useful information far ty))ical en-
<br />demic concentrations. It ie also woll•known that these
<br />methods suffer from poor precision duo in earl W a variety
<br />of serious interferences (5). As a result of these 6hottcominge, F E P
<br />a variety of altemativo methods have recently been developed. tetlps e
<br />lubmp
<br />These include colorimetric• (5, 6), potentiometric (~, and g
<br />
<br />chro»raWgraphic (A-10) determinptinne. The latter method, Pniups
<br />H3BK8-t )a
<br />while providing the beat speciation determination, lacks de• aamoio Lg,ap
<br />Lection sensitivity. Huth the calorimetric and potantiometric is
<br />methods, liko the lradilianal procedures, continue to suffer
<br />from serious interferences nr lack a means of speciation dp• i pyre.
<br />
<br />termination. support
<br />Wqo
<br />The goal of this work has been to produce a cyanide de- E~octripecx Fi.rur• Rt
<br />tection syatom that not only has a limit of detection below '
<br />the EPA water quality criterion of v ug/L Wtal cyanide (9)
<br />but is also Able t4 differentiate cyenido apociee by clnaeifica•
<br />tine, thereby providing a hotter representation of the potential Flpun t. H39K~175 pholoeell.
<br />toxicity of the sample. The use of a highly eeloMive reaction
<br />between cyanide and silver metal is employed W tLiGll these .,.m~.
<br />stringent requirements: buro• :~~~ rn„«.~i °
<br />F ~.•' .cFe~orion
<br />ire, $OalrOmap
<br />4Ag + BCN' + 2H70 + Ox ~ 4Ag(CN); + 40H' (2)
<br />The reaction in cq 2 produces a soluble silver dicyano mmplex Ftpurs 2. 91ock diagram of the exparlment I deslpn.
<br />that con be detected by standard atomic absorption spec•
<br />trnmotric (AAS) methods. Two faCWre that combine to make metals 9 mL of sample. Other light so teas used iacludod e
<br />this silver AAS detection method appealing ere (i) ailvor is General Electric germicidal lamp (Model G25Tb) and the same
<br />one element that eon be coatis detected et extremely low lamp with a l.5•mm•[Irick hnro$ilicate gl es sleeve. The entire
<br />concentrations by AAS and (ii) the cyanide roasts rapidly with system was cooled by o 5-in. fan mounlrrl xially above the lamp
<br />the normally inert silver metal. The cotiplitrg of this reaction and enclosed in a foil-lined light shield th
<br />in diameter. The silver reoctiorr chamber t was nominally 30 cm
<br />painted of a pure silver
<br />with AAS detection was first Used by G. Jungresie (I1, 121 as membrane filter (pore eizn 5 r.m, diamete 13 mml held in piece
<br />an indirect method far the cyanide ion. While this procedure by o 13•mrn stainless steel Cdter hnldor (Ito erica Cotp.. Livermore,
<br />proved adcgtlate for cyanide ion dotcrrninatlon, emphasis hoe CA). The resulting solutions were sooty. fur their soluble silver
<br />since shitted W the determination of Waal cyanide and all chase concentration by using o Varian Techtron Wmic absorption (AA)
<br />species that make up this category. It has, therefore, been spectrometer. The above Components e e finally connected iir
<br />aer essary to dovelop techniques and procedures that will allow aeries ae illustrated in Figure 2.
<br />h[a sensitive detection method to be used W speciete and Raagonte, All chemical used wore of he highest grade com-
<br />.:etecl both simple oird complex cyanides. mercially available. Standard cyenido s utiona were {)repared
<br />The resttlls presented below demonstrate that, givers the from e t g of CN-/L of potassium cyanide
<br />W pl•I = 12 with potassium hydroxide tuck solution, adjuawd
<br />r ante hazldling, an.
<br />al>{)rupriate chemical Conditions, the silver~yanide reaction standardized with silver nitrate.
<br />can 6e used far the gttenlitative determination of free cyanide Standard metal cyanide solutions war prepared by dilution
<br />contained in an aqueous sample. Moreover, by otnploying from their potassium salts. Stock soluti [IS of pntuuium !Ctrl
<br />pltotgchemical ligpnd dissociation techniques, this same re- cyanide, KaFe(CN)s; potassium cobalticy ride, K'Go(CN)a; po-
<br />action can Also he used to determine Wtel cyanide concpn- caesium chromic cypni<le, KtCr(CN)s; p tassiu[n ferrucyani[ie,
<br />tratione. Finally, by coupling the above methods with a- KrFe(CN)s•3H.,0; potassium silver cyanide KAg(CN)ti pnlarwlum
<br />tpbliehed aelrrtive oxidation • •rrtion chemistry, the quan• thiocyannte, KSCN; and potassium zinc c •anido, Ka7.n(CN)~, all
<br />tilative determination of CT ~ '•. may 1)e obtained. These available from Pfnlu and 6auer, were dil tod in distilled water
<br />; provide a means of charac- W a concentration of 1D0 mg/L cyanide,
<br />three determinations
<br />then d held at pH ~ 12 by
<br />,
<br />,
<br />retiring cyanide samples ibruugh which the possible Wxico• t]te Addition of potassiwn hydroxide. All
<br />end hoot-protected conditimra. Sodium h ere stoend under light
<br />ophosphile solution
<br />In,;.,al effects of the sam le are indicated. These techni uea
<br />p q wee prepared Icy dissolving 44 g of Naffs Ot•Ht0 in 100 rnL of
<br />.ill also allow the analysis to be performed in a manner thpt distilled water. Preparation of all other olutions needed Wray
<br />is safi r and simpler than previously possible. be found in the Cyenlde sections A-D of tanrlard Methods (3).
<br />EXPT'.RIMENTAL SECTION bus W the Wxieity of cyanide, care sh
<br />ecddental ingestion or akin contact with s old be taken to avoid
<br />lutione. Acidificet.ion
<br />Apppratus'. Solutions x~ere introduced by using a Rainin of cyanide solutions may liberate acutal toxic HCN gas. As a
<br />ina[rumer4 (Rabbit Model) peristaltic pump. '"!.o phoW cell safety precaution, all analytic procduros n thin work have bran
<br />(Figure 1) was constructed with a Philips mere. ry vapor lamp developed using solutiphe of pH ~ 12 nr a eve. Complete carets
<br />(Mode) H39ICB•17,5) xnd was powered 6y x Blearipack fixture precautinna and first aid treatmenu e t aptly described in
<br />(Modal It-175M). By use of a framework of boat Pyrex coda t2 Standard Methuda (3).
<br />cm in diarnetir, n sample tube helix of Teflon tubing ('/is-in. i.d. Procedures. Determination of Tatar nd Frrr C)~aziide. 1'n
<br />x'!e-ui, n. d.: Cole Farmer) was constructed around the center 40 mL of presen•ed (pH adjusttd W 12) c snide sample adr?
<br />of t},n lamp. The smr: •r':• helix was localized as near to the err g of sodium hydroxide and 5 mL of sodium ypophnaph~rr ~ rlw
<br />sours: as passible, ]ea ~: ~ about a 5-mm gap 6eta•een the tubing and mix well. Begin W eat up the oyetem y first optb:~~z
<br />Wad the lamp envehr; - ;'hr sample helix used holds npproxi• atomic sbaorption spectrometer for the d lectlon of ai.
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