Note: Descriptions are shown in the official language in which they were submitted.
~i~9t~4~-
mis applicat~n is a division of oopending Canadian application
Serial ~o 319,224, filed January 8, 1979
VArlous electrochemlcal systems are known in the art for
detectlng the preseDce of and/or ~ea~uring the concentration
of varlou- ~ubst nco~ o~ lnterest ln ~mple ~olutions ~u~pectud
of cont-ining the selected ubstances, and find utility in a
variety of onY~ronmental~ medical and lndu~tr~ pplication~
Conor-lly, ~uch y~tQw4 are employed in analyzing for ~etallic
ion- of intore~t, although systems al~o exist for the detection
of non-m-tal- uch -- cyanldo lon, ul~ur dlox~de and halossn,
nd for cert-in organlc materl~
One type o~ prlor art electrochemical analyais employs
~ravlmetrlc ~ethods ~n~~hich s deposit formed by electrical
~ctlon i~ weighed on an analytical balance Gravimetric
~ethods are prone to weighing errors, require a ~killed
technician, and are relatively time consuming and in6ensitive.
Another type of prior art electrochemical analy~is employs
~on-6electiYe e~ectrodes A number of ion-selective electrodes
have been devi~ed for testing for a variety of ion~ of intere~t
nd are considered to be reliable and relatively easy to u~e
~ow-v r, ~ number of ubstanoe~ of intere~t in the environmRntal,
- ln~u-trial nd ~cdio-l fi-ld- caDnot b- mea~ured ~it`D 10D-
-loctiv- electrode- Moreover, ~on-~lect~ve electrodes re~pond
log~rlt~mlcally nd thu- qanerally are not sufflcfently
on~lt~v for ~a~-ur~ng conc-ntrations blslow bout 10 5 to
10 6 ~olar
. . .
ESA-117 CIP -~-
~': , .
i~39~
~ olarographic naly~i~ ba~ed on current voltage curves
obtaln-d witb h~nging drop mercury l-ctr~d~s of~er~ an advantage
over ion--elective electrode~ of ~ensitivity in dil~te Lolutions
A f-~ture and reguir-ment of classic hanging drop mercury
p~larographic lectroly-i~ cell~ i~ ths dropping mercury elec-
trodo, 1 c , mercury droplet~ being di~charged periodically
into ~ olution from fine bore capillary under a driving ~e~d
of ~ercury ~owev r, this very fe~ture, which hao permitted the
~nitiation of extr-m ly u~eful polarogr~phic method~ in re~earch
work, ~itig~to- ag~in-t more general use of cla~sic polarogra-
phic lectrolysi~ c~ a~ common analytical ~y~tems, and in
p-rticular a- tool- or monitoring and controlling industrial
proc--- tream~ or for field u~e te~ting in medical and
nvironmental ~pplication~ Moreover, the characteristic
p-riodic growth and f~ll of the mercury droplet~ cause oscillation~
in the curront-voltage curves obtained using such cells and tbua
prevent the e~tabli~hment of ~tandard curves Other problems
of hanging drop mercury electrodes which have eesentially limited
c ll- o~ploying Yame to laboratory and oxperimental u~ include
¢ond n-or curr-nt build-up whenever ~ new aercury dropl-t i~
b ing fo~ ea t th- c-plllary, nd liaited ~urf-ce re~ of the
~ropl-t- whlch lialt- -n-itivity of th- lectrode In addition,
fora tion of th- tiny aercury droplet- i~ a dolicate proce~
wbich aay b- af cted by ~ numbor of inoident-l factor~, includin~
a ch-nic~l vibr~tion, l-nt of capillary, and pul~ation of to~t
olution into the c-pillary inlet between drop- In tbi~ aonnec-
ESA-117 CIP -2-
tlon it hould b- noted that tho roproducibility of dsoplet- with
r-gard to ~heir drop line and m~ o~ mercury per drop mu~t be
pr~oe~cally p~rf~ct at ~11 tlmes to permit pxoper evaluation o
tb- pol~roqram
St$11 nother type of prior B~t electrochemical m~a~uring
y~tom i- ~ tochnique called coulo~tric tripping voltammetry
Coulom~ric tripping voltam~etry i8 a two-step proces compri~inS
l-otrod~po-iting the lectroactive material of intere~t on or in
n lndioatinq or working electrod ~nd then electrodis~olving or
tripping the depo-ited material back into 601ution In anodic
strlpping voltamm-try the mat~rial to be measured i~ plated onto
~n lectrod- by ~pplying a negative potential over an oxtended
t~n p riod, and then tripping tb- m~terial off tbe lectrode
ovor ~ relatively hort period by sweeping to a positive potential
~h- order or potenti~l at which the element~ of the
matori~l aro stripped off She electrode provides a qualitative
naly-l- of tho material, and the guantity of the current
provides ~ quartitative analy~is Anodic stripping
volt~etry off-rs the dvantage- of enhanced ~ensitiYity,
r--olution, and r-producibility compared to cla~sical polar-
o~r-phic analysi- obtained u~ing hanging drop mercury electrode~
~y way o~ xampl-, thin-film mercury/graphite composite electrode-
h-v b -n mploy d in nodic stripping voltammetry systema for an~-
lyring for ~ tal- at the ub-nanogrum level S-e, for oxample,
th- r ~ortod wor~ of Wayne ~ ~ht-on, Reginald ~ Griffin,
~n~ G-org- ~ ~chr-iber in ~R pid Sub-Nanogram 8i~ultan-ou-
ESA-117 C~P -3-
il;~9l~
Analysis of Zn, Cd, Pb, Cu, Bi and Ti", Trace Substances in
Environmental Health, University of Missouri, Dr. D. Hemphill,
Ed; pp. 396-406, (1971). While electrochemically analyzing
solutions employing composite mercury/graphite electrodes by
anodic stripping voltammetry, e.g. as taught by Matson et al,
supra, may provide sub-nanogram sensitivity, the ability to
rapidly and reliably differentiate and measure selected substances
at the picogram level is not generally possible using existing
electrochemical measuring techniques. Also, many metals interact
with the electrode to form an alloy or analgam. Thus, anodic
and cathodic stripping voltammetry are limited to detection of
a relatively small number of species of metals and non-metals.
Obviously, the ability to operate at such low concentrations and
on a wider variety of species would have major commercial utility
in environmental, medical and industrial applications.
It is thus a primary object of the present invention to provide a
novel method which overcomes the aforesaid and other problems
and limitations of the prior art and, more particularly, provide
a novel and improved method for electrochemically analyzing a
sample in order to qualitatively and/or quantitively determine
the presence of selected substances in the sample.
- ~:139~4~
The method of the present invention generally comprises the
steps of dissolving the sample in a reagent to form a test
solution, charging a quantity of the test solution to an elec-
trolytic cell in contact with a plurality of active testing
electrodes,'simultaneously providing a plurality of electrical
potentials,across the solution from the plurality of active
testing electrodes, deriving signals from the active testing
electrodes corresponding to charge transfer reactions of materials
in the solution and sorting the signals to obtain signals which
identify the selected substances.
- The detailed description which follows describes an apparatus,
including a novel electrode, especially adapted to carry out
the aforementioned method as well as a novel electrolyte or
reagent for treating serum to release iron for electrochemical
testing.
Yet other features of the method of the invention will in
- part appear obvious and will in part appear hereinafter. The
invention accordingly comprises the process comprising the
several steps and the relation of one or more of such steps
with respect to each of the others, all of which are exemplified
in the following detailed description, and the scope of the
application as will be indicated in the claims.
~139~
For a fuller understanding of the nature and objects of the
present invention, reference should be had to the following
detailed description taken in connection with the accompanying
drawings wherein:
Fig. 1 is a front view in perspective of a preferred form of
electrochemical measuring apparatus according to the invention;
Fig. 2 is a front view, partially in section, of a preferred
form of electrolytic cell of the apparatus of Fig. 1;
Fig. 3 is an end view, in cross-section of the sample solution
stirring member of apparatus of Fig. l;
Fig. 4 is a fragmentary plan view, in cross-section of a
preferred form of sensing electrode element of the apparatus of
Fig. l;
-
11~984~
Fiq. 5 i~ a diagrammatic view of a flow detector element ofthe apparatu~ of Fig l~
Pig 6 i~ block diagram of the electrical and pneu~atic
control- ~nd function~ of the apparatus of Fig lS
Fig 7 is a plot ~howing the current in microamperes, ~A,
v r-e- the potentisl in volts ver~ a standard Lilver~silver
halido re~-rence electrode, obtained in ~ceordance with the pre~ent
inv-ntion~ ~nd
Fig- ~ and 9 ar- front view4 ~ in p~r~pective, of alternative
or~ o~ olectrolytic cells in accordance with the pre~e~t invontion
~ he pre-ent invent~on i8 ba~ed on measurements o f
olectrochemical reactions of ~elected substances in solution
under controlled potential conditions As is well known in the
art, when electroactive substances are di~solv~d in a ~olvent to
form a re~gent or electrolyte, and an electrical current passed
through the electrolyte between an anode and a cathode disposcd
thorein, poeitive lon~ will be attracted to the negatively charged
c-thode where their charge will be neutralized, while negative ion-
will ~ove towards nd be di~charged t the anode The electrical
pot-ntials at which such electrochemi¢al reaction~ occur will
vary deponding upon the particular eubstances involved By way
of ox~ pl-, con-ider ~n agueou~ olution which containe
both iron nd copper lon~ Iron norm lly exhibits ~alance
o~ two or threo, while copper normally xhibit- valance of
on- or two ~he el-ctrical potential at which ferric ion~ ~Pe
in olution ~uy b r-duoed to ferrou- ion~ ~Fe ~ is a con~tant
~t a ~iven tomperaturo Li~ewise, the electriçal potenti~l
nt wbich cupric lon~ (Cu ) in ~olutlon ~ay be reduced to cuprou
E5A-117 CIP ~7~
il;~9~4~1
lon- (Cu~ al~o a constant at a given temperature, and i8
diff-r-nt from tbe electrical potential at which the reduction
of forrlc lon- to ferrou~ ione occur~ ~he electrical
potentlal at which ~uch reaction~ occur are approximately
d-acrlbed by tables of ~tandard or $ormal potentials~
Sbe ab~olute value of the elec~rical potential of ione o$ ~olu-
tlon 1- lnd t-r~inat- Howev-r, loctrochemical reaction-
for a ~artl¢ular p ci-- are de~cr~b-d in t~rm~ of a potential
v r-u- a tandard reference couple uch a8 H2/~ She
~aqnltude of tho pot-ntial i8 a mea~ure of the potential
tbat ha- to be applied versu~ a ~tand-rd reference
l-ctrodo to forco charge tran~fer to occur ~he electrical
pot-ntlal t which uoh reaction~ will occur ie
r-ferred to ae the ~Charge transfer potential"
B5~-117 CIP -8-
li;~9~4:t
A~iqning an arbitrary value of zero to hydrogen, the
potential E of an lectrochemical reaction may thus
b written according to the following reaction
E - E~ ~ 0 05915 1O9lO ( ~ tl)
wh-r- n i- ehe number of Faradays, Ap and AR are activitiffs
of th- product r-aotant~, and x ~nd y ar- oorrespond$ng co-
ffiai-nt- of th- l-ctroohem~cai s-nctions ~hu~, the potential
Eo i- tb- tandard potential related to the particular reaction
~ i- a potontial applied to drive the reaction either to reactants
or product~ accordinq to the equilibrium condition described
by quation tl) Under conditions where the ~ applied is
larqo nough to drive the reaction to virtual completion at
quilibrium, the current derived will be proportional to
t~- concentration of tho reactant in the ~olution ~owever,
b ckground noi-~ pr-vent~ direc~ measurement of ~oct cample
olution~ and in the caQe of very dilute solutions may prevent
direct measurem~nt in many in~tanceQ ~8 used herein the term
b-ckground noi~e~ i~ intended to refer both to major interference
f-ctor- uch ~ th- procence in the ~olution of other electroactive
~at rial- wbich, by virtue of their electrical activity in t~e
E5A-117 CIP -9-
4:~
olut~on, so-pond to the B~me electrical potent~al aa the ion
oi lntareat, and 180 ~ajor non-Faradaic int~rference factors
uch a- c-pacitunce ~ignal~ of the electrode in the solution due
to the exi6tence of a boundary layer of still solution adjacent
the active ~urface~ of the electrode, bulk solution signal~, in-
berent Farad~ic ~ignal~, electrode 6ettling signal~ and the like)
A featuxe and advantage o~ the present lnvention re6ide~ iA the
limlnation o~ an~/or cancellation of bac~ground noi~e through
oo~bination o~ olectroche~ical manipulations and el-ctrode
guometry
Furth~r under6tanding of the fe~ture~ and advantage~ of the
pre~ent invention will be had from the following detailed
de~cription of one preferred embodiment of the invention which
illu~trates an electrochemical testing sy~tem for measuring
tho lron content in ~erum or blood It will be under~tood
howevor, that the ~yste~ of the present invention may be
advantageously employed for detecting the pre~ence of
and maa~uring the concentration of variou~ otber sub~tance~ of
lnt-r--t in ample olution
R-forrlng to F~g 1, there i6 illu~trated an electrochemical
a-ur~ng pparatu- indlcated gen-rally at 10 including a ba~e
11 ~ount-d Qn ba-- 11 by me n- o~ uprigbt upport 12 i- a
cabin-t 13 who~o front face act~ an a control pan~
~ount d on th- pan-l ar- var~ou~ control ~ean~ lncluding -
ESA-117 CIP -10-
11~9~34~
display panel 16, function buttons including a ~tandby button
17, an ~utoblaAk~ control button 18, ~n ~autoblank set~
button 19, ~nd a c~libration knob 20 Al60 positioned on
the control panel 14 18 an off-on button 22, a flow
ind~c~tor 23 suit~bly labelled to ~how that a prior ~umple i8
flu-h-d out ~nd a ne~ te~t mdy b~ ~tarted Al90 on the control
panel ~rc t~rt button 24, ~nd a ~running~ indicator 25
For conv-ni~nce it,i~ preferred that the controlfi be co~binations
of pu-h-button~ and ~ndicating ligbt~, ~nd in the actual
~ppasatu~ ~uch combination button~ ~nd llghtfi are used
D-pending ~rom th- bottom of cabinet 13 i8 ~ cell assembly
~7 lndicated in outline ~nd shown in further detail in Fig 2
Po~itlonod on bass 11 re two contain~r~ 28 and 29, auitably
connected by pl~tic tubing or thu like to the cell block
Container 28 receive~ flushed cell contents at the end of each
run nd contain-r 29 holds a supply of fresh cell liquid or
lectrolyte
Fig 2 fihow~ the cell a~sem~ly of the apparatus of Fig
co~pri~ing generally a cell block 33 and a sensing electrode
3~ mount d th-roln Cell block 33 comprlse~ ~ ~uitable ~ounting
pi-c- w h -, fos x mple, o pl-~t~c bloc~ h-v~ng a cs~w t`nre~r
35 or oth-r ~ountlng ~ean- at tbe upp r nd A vertical channel
or cylindrlc~l hollow 36 run- through th cell block nd co~-
~uAlcat-- with tho ~nterior of cen~ing lectrode 3~ ~wo
pa--ag-way-, th fir-t an inlet pss~age 38 to receive a ~umple
to ~ t-~t-d whlah ~ay, ~or oxumpl-, be by mean~ oS a pipette
ESA-117 CIP -11-
,
~1~9~
~not ~hown) in~ert-d lnto chonnel 38, ~nd the ~econd an outlet
p~ g-w-y 39 fo~ c-ll liquid Cell block 33 i~ formed of ~
liquid-fmporviou~, ri~id, olectrically insulating, chemically
in-rt m terial ~uch ns unpla~tici~ed polyvinyl chloride, poly-
totrafluoroet~ylene fluorocarbon re~in~ or the like
~he bottom of~channel 36 i~ rece~sed to receive sen~ing
l-ctrod 34 8-n~in~ olectrode 34 io in the fonm of a bollow
cylindbr, and th- ,inn-r ~urface of th- lectrode and the inner
urfac- of ohann-l 36 are flu~h ~nd ~- ~ooth n- po~fble ~o
- to mlni~- th- m-t-r~-l c~ught tberebetween In actual
practic- tho l-ctrod- i~ permanently ~ounted in the cell
block by uit~bl- means uch a~, for ex~mple, by an epoxy
r--ln or t~e liko, and the inner ~urface of the joint between
th- two i~ machin-d smooth
At the bottom of sen~ing electrode 34 is a seal and
connector device 46 which may, for example, be in the form o~ a
pl~tic plug molded to the sen~ing electrode 34 havin,g a ~crew
tbr-~d connection 35~ for connecting a pipe or hose thereto
~nd having a channel 49 extending therethrough A continuou~
pa9-age i- thu~ formcd, nd electrolyte or other contents of the
c-ll cun b- flu~h-d out by pa~ing fr-~h olectrolyte or other
liquld ln th~qugh ch nn-l 49 ~nd out through outlet 39 in the
c-ll block bov th~ ctrodo
~SA-117 CIP -12-
`- - 11391~41
A- ~ntlonod upra ~n lmportant ~ture and ~Yantag~ of
th- pr-~ent invention i~ the ab~lity to differentiate b~tween
lectrlcal ~ignals reprQsentative of the c~arge tranfifer
lectrolytic reaction of 6elected substances of interest, and
lectrlcal ignal~ derived from the bulk sample 601ution, inter-
ferrlng ub~tance~ and other backgr~und noise Tbi~ featurs and
~dvantag- 1~ m d- po--ible ln p~rt by the construction of ~nsing
leotrode ~4~ ~--ing el-ctrode 34 compri~es a generally cylin-
drlcal body of block epoxy having ~ounted therQin a plUL~lity of
active ~lectrode egment~ ~he electrode body comprisea an
l-ctrlcally in~ulat~ng ~atarial ~uch aa a polymeric material
whil- the active electrode ~egments comprise a nuitable alectrode
b~ae uch 8 gr~phite, pyrolytic graphite or platinum, or the
active electrode segment~ may comprise coatings of active electrode
~terial ~uch ~ mercury or gold In practice, at least two
l-ctrically di~crete electrode areas are employed, for example,
in tAe form of ring~ or bands of active electrode surface on
the in-id- of ~ hollow electrode body The 6egment6 are
epar-t-d by l-ctrlcally in~ulating band~ on the in~ide of
th- el-ctrode ~ucb ~n electsode c~n be fosmed by bolding ~eg~nt-
ol activ l-ctrod- materi-l ln the for~ of rings ln de-ired po-i-
tioA nd molding th rin~- with nn l-ctric-lly lnsulatlng uch e-
an ~oxy r--in to iore cyllnd r 8-n-lng l-otrod-
3~ la hown ln lurther detall in Fig ~ For convenience
ol llluJtr~tion n-lng l-otrod- 34 ha- been hown ~ co~prl-ing
~SA-117 CIP -13-
4~
two ~ctive testin~ electrodu segments, a counter or power supply-
inq elactrode ogment, and a reference electrode segment as
~o~low-t- a ~r-t ct~ve te~ting electrode ~eqment 42, a second
activ testing electrode s~gment 43, a thir~ counter electrude
eg~ent ~4, and a referunce electrode segment ~5 The fi~t,
econd and thi~d ~ctivo lectrode egm~nt~ 42, ~3 and 44 are
formed o~ uit-bl- lectrode material sùch a8 gr~phite or the like
while the roference olectrode egment 45 i~ ~ormud of silv~r palla-
dium or the like Elactrode segments 42, 43, 44 and 45 each com-
pri~e a cylindrical ring embedded into a cylindrical electrode body
41. ~he electrode ~egments are spaced apar~ by a narrow gap so as
to ~e electrically insulated one from the other, and the slectrode
-gm nt- aro mounted so that the active surfaces are ~ubstantially
flusb With the inner urface of electrode body 41 so that the
lnner ~r~ace of the entire electrode 34 is a smooth as possible
Electrical connections (not shown in Fig 4) are provided to each of
tho el-ctrode segmonts and are suitably connected to the apparatus
by m-un8 of a four wire lead terminating iA a four-pronged
plug ~ ~hown in ~ig. 2 Obviously the electrode may comprise
~ddition~l ~ctive lectrode segments
Po-itioned within 01ectrode 3~ i~ a stirring ~ean~ 50
~tlrrlng ~o~n- S0 i- ~ounted for rotation within the electrode
~ody by meuns of rod 51. 8tirring means 50 nd rod 51 re
form-d of lectric~lly inaulati~g and chemically inert ~atarials
~5A-117 CIP
s~a~
Buch a~ molded resln ~he lower ~nd of btirring mean~ so ib
~llghtly wedge-~baped or cone-~aped, ~nd is g~nerally close
~ltt~ng witbin tha electrode body A diagonal groove 52 which
i- better ~een ln Fig 3 run~ ~long the surface of th~ &tirring
~e~n- 50 When rotated in th~ direction shown by arrow 54,
gsoove 52 creates a high degree of mixing or turbulence closely
adjacent to the ~ctive aurfaces of electrode ~egment~ 42, 43, 44
nd ~5 ao a~ to minimize the thicknos~ of the boundary layer
o~ till ~olution adjacent the active surfaces of the electrode
~egment~, while ~aximizing mass transfer to the electrode ~urfaces
In use off-on button 22 i~ fir~t activated Ordinarily,
tho pparatuc will be left running ln a ~tandby condition
ov-rni~ht nd will be turned off i~ it i~ to be left idle for
a period of a week or more At the start of each week, or for
purpo~e~ of abundant caution at the ~tart of each day, the
apparatu~ may be calibrated ~t is first operated with the
calibration button in operating position to standardize the
lectronic~ ~ will be hereinafter described A blank sample
of r~agent i8 run fir~t Then the ~auto-blank~ button 19 i~
~et, holding the cali~ration Next a standard sample of known
lon concentration i- introduced into the cell 22 and tho appa-
ratu- run through a cycle When it hae been properly t nd-
aralr-d, the calibr-tion k b 20 1~ ad~u~ted ~o th~t ~be reading
ln th dlnplay p nel 16 corre~pond- with the known ion quantity
ln the t ndard c-libration ample
E5A-117 CIP -lS-
.
ll~9~L'l~L
~ plastic tub- or pipa 40 (not ~hown in Fig 2~ conAects
tb- ~911 a-~-mbly 27 to th~ apparatuo At ~ ~elected point lonq
tub ~0 ~nd pr-f-r-bly wlthin c~blnet 13 i~ ~
f~ow ~etoctor illuHtrated di~gramnatically in Pig 5 ~n
e~ittor 55 or oth-r llqht ~ourc~ is positioned near n window
at a point ~long t~b ~0 Tho window m~y be a tran~parent
in~-rt or th- tube it-elf may b~ transparent Oppo6ite emitter
55, 1 e on the oppo~$te ~id~ of tube ~0 i~ ~ detector 56 posi-
tion-d adj~cent ~ similar window When tube ~0 i8 empty or
fill-d with a gas the bea~ of light 57 from the emitter i~
qult- diffu-e Whan tube ~0 i~ filled with a liquid uuch as
tbe c-ll electrolyto flowing through the tube, the liquid acts
a- a l-n- ~nd in¢re~o-- the harpnu~s of focus of li~bt be~ 57
D-t-¢tor 56 is aa~u-t-d for a tbreshold ~uch that it can deter-
~in- the pre~once o liguid in tube 40 and the length of
time ~uch liquid ~ present ~he oignal from detector 56 i~
mployed to indicato that there has been flow of liquid through
tub- ~O for a ufficient time to accompli6h flu~hing out of
c-ll olectrolyte ~ftor a ~ingle run eo a~ to re~ove the ~ample
t~ r rom.
In ropetitiv- run~ the cell 27 i~ repeatedly filled with
an loctrolyt~ nd th cell tirring opparatu~ 1- con6tantly in
oper~tion to keep tho cell contents uniform ~nd ~ixed A
~nown quantity of ~ test ~a~plo i8 thon pipetted into a coll 27
~SA-117 CIP -I6-
84~
~h- runn~ng ~ndic~tor 25 l~ght~ t~ ~how tbat the test i~ in op~-
ation In a preferred embodiment of the present invention the di~-
play p~nel i~ a digital di~play which count~ to zero and then up to
tho numbor of microgr~m~ per 100 mililiters of 6~rum (~9~). When
th- di4it~1 displ~y top8 counting the te~t is complute A~t~r
tim-d w-iting per,iod the cell olectrolyte containing th~ campl~
1- fluJhed into container 28 and a new ~upply of electrolyte is
fntroduced into the'cell ~rom container 29 When the start test
lnd$cator 2~ lights up again, the apparatus is ready for a nuxt
~u pl-.
In Pig 6 is ~hown a block diagram of electrical and fluid
flow control~ for the foregoing apparatu~ A cell 27 ~uch
a9 ths cell o~ Fig 1 iB connected to have a r~agent or electro-
lyte conveyod therethrough in individual analysi~ quantiti~ A
pump 60 pumps air tbrough a line 61 from a reagent container
62 A reagent valve 63 controls flo~ of the reagent to cell 27
Referring to Fig 2, the reagent flows into lower channel ~9
nd thu~ into ~nd throu~h the cell 27 Another Sluid lin~
65 i- po~itioned to c~rry the reagent or other liquid from the
coll 27 p~t an optlcal ~en~or 6~ ~uCh a~ Sor exa~ple, the
-n-or hown $n Fiq 5 Line 65 then convey~ tho liquid to -
dr-ln oontafn-r 69 A ~acuum line 70 return~ to pump 60 ~hu-
tb flow of the liqufd through c-ll 27 $B
lnto th- bottom of th- cell ~nd out through outlet 39
po-itlon-d abov th- o-ll. Pr-ferably lnlet ch~nnel 3B in cell
ES~-117 CIP -17-
27 will be located ~lightly sbove outlet channel 39 ~o that liquid
normally will flow out Qhannel 39 rather than cha~nel 3~
For analyzing ~ ~ample the eample i~ d~ssolved in a solvent
to form an electrolyte or reagent By way of example, for testing
for iron $n blood or ~erum a 8mall eample of blood or L~rUm,
typlcally a 5 to 100 ~lcroliter sample is added to an electrolyte
or ohemlcal roagent which rolea~es iron from it~ ~erum bonding
nd eparatos tbe transfer poten~ial~ of iron and its most
u~ual interferring element, copper
1~ total iron-binding capacity i8 being ~easured, th~ serum
i- fir~t fully ~aturated with iron, as by mi~ing it with an
iron-contdining ion exchange resin
Proferably, the electrolyte or reagent for treating ~erum to
release iron for ~e~ting compri~es 6trong ~ydrochloric a~id, e g
between bout 5 1/2 and about 8 1/2 Formal, and preferably about
7 ~ormal, in ~ lower alcohol ~uch aa propanol or isopropanol
Metbanol and ethanol bave been found nearly as effective as pro-
p-nol or i~opropanol, but have the di~advantage that they ~re ~ore
xpen~iv-, nd th-y ~r- moxe volatile ~nd therefore ~ore d$f~ioult
to handle higher alcohols BUCb as butanol and the liku are oper-
bl-, but are lo~- compatible with ~trong hydrochloric acid
Oth-r matorialY uch ~ aceton$trilo and acetone are al~o oper~blo
but ar~ a ~ti-f-ctory partly becau~e of le~ aati~fac~
tory performance nd p~rtly becauee of co~t, volatility,
toxl~lty and the like. ~he ~pparatus i~ calibrated in accordance
vith th- el-cted trongth~ of the hydrochloric acid
117 CIP -18-
li~9b~4.~
Th u~e of ~trong hydrochloric ~cid in lower ~lcohol
a~ an olectrolyte or raagent to relea~e iron from lts ~erum bond-
in~ and to epar~t- tho transfer potentiAl of iron ~nd it~ ~o~t
u-u~l lnt-rf-rr~ng ub-t~no~ copp~r, ~n order to prup~re ~b-
bloDd or erum ~or el~ctrochemical analy~i~ for iron i~ believed
nov-l
In place of hydrochloric ~cid there may bo omployod other
compounds having high chlorine or halogen content, ~ut such
other compound~ hàv~ not been found to be fully ~ati~factory
For ~xample, lithiu~ chloride i~ a more sxpen~ive ~ource of
chlorido ion and l~o tend~ to precipitate at lea~t a portion of
tho erum Hydrogon bromidu i~ another eource of halogen ion
but i~ al~o more expen~lve and i~ notably more difficult to
work with and i~ corro~ive
Included in the ro~gent or electrolyte is an extremely minute
quantity of ~ilver ion in the ~3nge of about 200 parts par mil-
lion which as~i~t~ in the operation of the ~ilver reference
lectrodo ~egment ~5 ~he reference potential i8 the ~ilver ion
potontial, maintained by reference electrode segment 45
Accord~ngly, the reagent or olectrolyte preferably will include
7 Yormal BCl in propanol togsther with 200 pdrts per million
~ilv-r ion nd uch re~gent or electrolyte will relea~e iron
lrom orum or it- iron binding component~ to make the iron avail-
abl- to electrochs~lcal mea~ur~ment ~nd al~o ~ill permit epara-
tio~ of the charg- tranefer potential- of iron and coppor, and
glv- r-produclblo r-~ult~ in the naly-i~ of -rum iron by
l~ctroch~mlcal ~o~-ur-ment teohnique~ in microllter ~mpl-
guantitl--.
~aa-117 CIP -19-
9~
T~e prepared ~ample comprising a serum to be t~sted, toqether
with a ~ea~ured guantity o~ a reagent or electrolyte i~ charged
eo o-ll a~-ombly 27, nd ~t~rring commenced
A potonti~l contsol 70 ppliea two different electrical
potenti~l- 72 and 73 to two of the ~ctive ta~ting el~ct~ode ~g-
~ont-, g el-otrode ogmant~ nd ~3 El~ctrical potontial 72
i- -t t a Yalue wbich causo~ an lactrochemic~l r~-ction of both
~ron and copp-r, whil- lectrical potontial 73 iJ set at a value
~h~ch cau~e- el-ctrochemical reaction of copper alone, a- ~ill
be ~--crlbad in detail here~nafter~ A reference potential is
appliod to the silver eloctrode ~egment 5, and ~nother potential
i~ applied to counter ~lectrode ~egment 44 and provides a
~ource of current to the cell Alternatively counter electrode
eg~ nt ~ may be held at ground ~he current or ~i~nal~ fro~
firJt And ~cond t~ting olectrodu segments ~2 and ~3 are fed
to a logic ~odule which Yubtracts the first signal from the
cond nd, lf d--irod, applies a multlple for calibratlon pur-
po--s. By w~y of ox~ple, tbe current or signals from the two
ctive electrode~ eg~ents in the cell 27 can be fod to a current
convertor ubtraator 75 with two variable ga~n- for
ad~u-tJ-nt ~h ignal than goes to a iqnal accumulator 76,
and t~-n to ~ calibr-tlon bl~nking circuit 77 which also h~ a
varl~blo goin or c~librator 7H ~h~ signal from the calibration
bl nking circuit 77 then i~ fed to a readout 80 and, in turn,
to an autobl~nk control ~1 The ~ign~l from the autoblank
cont~ol i- roturn~d to tbo calibration b~anking circuit 77
ESA-117 CIP -20-
4~
Wh~n tho calibration i~ correct, sn autoblank ~ot ~2 is operable
to f~x tho clrcuit-
~ ho loctroch~m~csl re~ctions which tak~ place and ~r~~ea-urod by the apparatu~ ar- th~ r~duction of ferric ion to
~crrous ion, the oxld~tion of ferrous ~on to ~erric ion, nd
the roduction of cupric ion to cuprous ion . ~Ge~erally,
~at-si-l will not b depooited on tho ~ctive el~ctrode egment~,
~nd ~ccordingly th~-- r~actions may be con~id~red to b~ ~charge
tran~f-r~ rath~r th~n electrolytic or olectrodepo~ition reaction~)
At actlve lectrodo ~gm~nt ~2 there occur~ th~ reduction of fesric
ion ~Pe 3) to ferrou- ion ~Fe 2~ and the reduction of c~pric ion
~Cu~2) to cuprou- ion (Cu~l) At activa electrode segment ~3 ther~
occur~ th~ r~duotlon of cuprio ~on to cuprous lon and the
oxidation of ferrou- lon to ferric ion A~ a matter of choice,
activo olectrod~ -q~e~t 42 i~ ~et at the highor potential
Th~ ignal ot the one olectrod~e 18 ~ubtracted from the other
with the following result
~A) F ~3 t ~ Fe t Cu t e ~ Cu nd (2)
(Bl Fo ~ Fel3 ~ e ~ Cu~2 Cu+~ 3)
by ubtr-ction
~A) ~ Fe~3 ~ d Fe+2 ~ Cu ~ O. ~)
A- c~n bo e~n, th~ roduction of cupric to cuprou~ lon 1
cancellod out in tho loqic with the result th~t the totsl o~
iron content i- th- ~ignal ~hich i8 fod to tho digital or other
r ~dout
E&A^117 CIP -21-
11;~ 4~
Csnerally, tho potential on active electrode ~egment ~2
m~y be v-ried b~two-n about 0 to 1 volt while the potential on
activ- loctrodo -gmon~ 43 msy be v~rled betw~en about 0 to
300 mlllivolts fro~ that of ~egment 42 Por te~ting for ~erum iron
ln accordance with th~ foregoinq tochnique activo el-ctrode seqment
~ wlll bo ot at potontial of bout ~60 mllllvolts wh$1- act$vo
el-ctroda egment ~3 will be ~et at a potential of about 250 m~ll$voltu
~ t i- to be appr-clAtod that the lnvention $~ not limited
to tb- mea-urement of orum lron, but that any electro-
ctivo ~ub~tance ~ay bo detected and me~ured using the forego~ngproc--- nd appar~tus ~y way of exum41e, the electrochemical
moa-uriAg ystem of the pre-ent invent~on may bo u-ed for
d-toct$ng ~nd mea-uring heavy motal~ sucb a~ zinc, cadnlum, lead,
copper, bismuth, gold, silvsr and thallium in blood ~ample~
~ oll known in th- rt uch heavy metal~ nor~ally are com-
plexed with blood, and thus mu~t be relea~ed before they can be
~e--ured A ~umber of reagents are ~nown in the art and sre
v-~lable commerci~lly for r¢lea~ing uch heavy metals from human
blood Ono such re-gent i~ callod METEXCHANGE~
nnd is available fro~ Environ~ental Science~ A~sociates, Inc , of
dford, ~bssachu--tt- Tho m~nufacturor de~cribes thi~
r-a~-nt a- compri-inq dllute aqueous ~olution of calcium
c~lorid-, chro~iu~ tri~chloride, hydrogen ion, phosphate $on,
~i-t~t- lon and dispor-ing gent ~he mixture oS calc$um ion
nd chro~ium ion 1- aid to c-uae rele~ae of oomplexed heavy
ESA-117 CIP -22-
~1~9~4~1
~ t-l ln blood ~o th~t the total concentration of heavy
a-tal c n b- ~footlvely ~oa~ured
~or-ovor, tb- lnvontion $~ not limited to tbo detection
nd n0a-ur~ont o~ heavy meoals in b$ological sample6 For
x-mpl-, heavy metal~ complexed with ga~oline can be detected
ana ~oa~ured in coordance with tbe foregoing by dis601ving
g~-olin- ~mple~ ln a roagent which comprise~ a dilute mixture
of ICl, N~Cl, N2~HCl and a polyalcohol The ~ame reagent
oan b- u-od to rol-a-- various other heavy metals from a wide
~ari-ty o~ organic ample- Other reagents which contain
a motal lon wh$ch wlll displaoe the heavy metal of intere~t
from the complea can al~o be u~ed
Addltlonally, large number of organic sub~tance~ are elec-
troactiv and thu~ can al~o be detected and measured ln accordanco
with th- foregoing lnvention including - unsaturated hydrocarbon~,
a~ids~, triazine~ and phenotbiazines, amino acids, amine~ and
mide~, phenol6, aromatic OH, quinolines, quinones, imine6,
ol~fln-, k~tone~, ald hyde~, o~ter~, and olefinic osters,
thor~, organo~etallics, diazo compound~, nitro compound~,
nd baloqen~ ~he um- reagents which ~re u6eful for dissolving
th-~- orq-ni¢ ub~tances for liquid chromatography generally can
l o be used a~ th- r-agent in the process of the presont $nvention
~aong-t ~ult~ble reog-nt~ arv mentioneds water, lower ~lcohol~,
~uch - m0th-nol, eth~nol and i~opropanol, and mixtures tbereof
I~ roqulr-d ~ trong inorg~nlc acid uoh n~ hydrochloric oid
E5~-117 CIP -23-
~3~
or pho~phoric ~cid, tsong base ~uch a~ sodium hydroxide,
or a alt uch ~- odium ¢hlorlde may be ~ncluded ~n the
r-~g-nt to s-lea-- t~ ~peciea of in~ere~t from a complex
For xampl - , for ~nalyzing blood ~amples for the pre~ence of
~ylenol, orphin~ or heroin in accordance with the present inven-
tion ~ uitable r-~g~nt comprl~e~ meth~nol/water~pho6phoric
ac~d ~lxtur- co~pri-lng about 30~ methanol, 0 1 to 1~ phosphoric
acld, and tbo bal-nc- wnter For an~lyz$ng blood ~ampl~ for
ntial traco loments ~uch a~ zinc, an aqueou~ ~olution of
c-lclu~ ac-tate buf-red to pH 3 has been found to be a suitàole
r ag-nt A nor~al allne r0agent may be used to measure glucose
~n blood or erum
Tho olectrocho~ical measuring system of the present
invent~on may also be advantageously e~ployed for detecti~g
nd mea-uring ub-tance~ ~uch a~ cyanlde, halogen, S02 and Ux
ln biological campl~-, water or eewa~e ~he ~lectrochemical
~ea-uring ystem of the present invention may also be adapted
for u~- in monitoring of olectroactive substance~ in chemical
proce-- tre~m~ The required electrode potentials are approxi-
m t-ly tb0 umo a~ would be employed in controlled potential
coulom~tric tripping of the me organlc ~ub~tance~
~h xtr~o -n-itlv~ty of the l-ctLochemical mea~uring
y-t~m of the pr---nt invention per~it~ acculate mea~urement~
~n pico~ram region Shus, tbe electrochemical neasuring
yst-~ o~ the pr~--nt invention may be ~dvantageously employed
ESA-117 CIP -2~-
9~
for ~ ~inq oil ~nalysis ~or agricultur~l purpo~eg a~d may ~l~o
be u~ed for ~etsl pro~pectinq In regard to ~his latter feature,
tho p~OCe~B involve~ ~ea~uring ~oil and/or water ~amples taken
in a grid pattern in order to zero in on significant deposits
of ~lected ~et~ y way of example, to zero in on deposits
of rolatively rare m~tal6 s~ch ag molybdenum, tungsten,
vanadiu~, eit niu~ ~pd uranium ~oil or water ~amples taken on
a grld are ~xtracted with and a~alyzed in a reagent comprising
alco~olic HCl olutlon such ~ o 20~ aolution of m~thanol in HCl
~h~ ctrolyte i- then cbarged to the cell, one of the ~ctive
alectrodo ogmonts i- se~ at an electrical potontial to oxldize
tho metal Or inter-st while another of tho active electroda
egmunt~ i9 et ~t dn electrolytic potential to oxidize the metal
of intere~t plus other interferring metals ~he required electrode
potontials are ~pproxi~ately the ~ame ~s would be employed in con-
~SA-117 CIP -25-
4~
trollod potential coulometric analybi~ of the ~ame metal or
met~l- Other metal~ may be mea~ured by changing the electrode
potential- and/or tbe reagent For 0xample, for chromium a
pseferrod rsegent l8 alcoholic hydroxide solution ~uch a~ 0 8
no~m~l NaO~ ln me~h~nol ~he u~e o f n~ alcoholic HCl ~olution
- reagent for el-~trocbemical analy~is of molybdenum, tung~ten,
v nadiu~, t~tanium and uranlu~, and tho u~o of an alcoholic
bydroxid- olut$on a~ reagent for electrochemical nnalysis of
cbrom~um ~r- beliov-d novel
Ga-eow u~ple~ nnd/or air~ornR ~umples can al~o be
naly~-a by bubbllng th- gaB or air through a uita~le re~gent
to di--olve the ubat-nce of interest The electrolyte can
tbon b- charged to the olectrochemical cell as above described,
a~d m~a~urement~ made in aoco~dance with the foregoing
One ~killed in the art will recognize that the invention
ie u-c-ptible to ~odification ~bu~, sen~ing electrode 34 in
E5~-117 CIP -26-
~ccordance with the present invention has been shown as comprising
two act~v- testing ~lectrode segments, a reference electrode seg-
~ nt nd oounter l-ct~ode egm~nt with the eluctrical potential~
on th~ two acti~e te~ting lectrod~ segments being ~djusted ~ccord-
inq to the p-rticular substances being detected and measured
On- killed in the art will recognize, however, that electrode 34
may comprise a large number of active testing electrode s~g~ents,
g lectrode ~ aay comprise 50 or 100 electrically discrete
active te~ting electrode uegments, each segment being electrically
coDn-cted to a different electrical potential to effectively re-
produc- n onti~e current voltage curve ~or e~ample, the elec-
trodo 3~ ~ay comp~i-e twelve active testinq electrode ~egments
at a ~eries of electrical potentials, which may be 20 to 80
~illivolt~ offset ~hus, to electrochemically analyze samples
which may contain a variety of electroactive ~ubstances of inter-
e~t in which there are known or suspected interferring substances,
ESA-117 CIP -27-
11;~9~4~
lt ~ i~pl~ ~atter to ~tore t~ g~al l~formation from each
l-ctrod- ~eg~ent and to ~elect out or ort only those active
loctrod -gment~ ~hich ar- at th- particul-r lectric~l poten-
elal whlch produca th- d-~lr-d loctroch~m~c~l r-act~on~, d-r~v~
~gnal- fron t~o-- l-ctroche~lcal ~-a¢t~on~, und um ~add or
ubtr~ct) th- ign~l~ to rrlv- at th- de-ired me~-uromont ~he
-l-ct-d actlv- l-ctrode -gm~ntY may be conn~ctod in manually
by th- op rator, .g according to printed in~truction~ Obviou~-
ly, uch un ~pparatu~ may alro include a plurality of reagent~,
~uppl~--, r-agent v-lve~, etc o that a p~rticular reagent muy
b- ~ntroduc-d d-p nding on the particular ub~tance being
d-t-ctd nd moa-ur-d
Sh- foregoing ~pparatu~ ha~ boen de~c~ibed ~ being run
und r operator control~ however, the apparatu~ can be ~dde to
op-r~t autom tically a~ follow~ - Referring to Fig 6, a control
B5~-117 CIP -28-
11;~9~4~
y~c~roni~qr 85 i- psovided for actueting ~ pump a~d valve
t~ing oontrol 86 nd al~o an ~nalog timing control 87 ~be
an~log ti~ing control 87 i~ in the ready po~ition ~nd i~ ~ctivated
for ~nalyai~ ~y t rt ~nalysi~ control 88 w~ich app~ra on
th- ~ppar~tus 8 st~rt to~t button 2~
Optlcal ~en~or 68 who~e op-r-tion i8 illustrated in Fig S
dir-ct- a ignal to 10w en~e circuit 19 which in tusn ~e~ds
a ~ignal to pump and v-lve timing control 86 and analog ti~ing
control 87 Should the flow through line 65 be inadequate for
co~pl-t- flushing of cell 27, the sign~l from flow s~n~0 circuit
90 oporat-- to turn off pump 60 or close valve 63 or both, and
to inaotivate analog timing oontrol B7 BO that ~n analysi-
c nnot b- ~tarted without resetting the apparatu~
A powor upply 91 operated from ~n A/C power source 92 ~up-
plie- a po~itive volt~ge through line 93, a negative voltage
through line 9~, nd ~ ground potential through line 95 which
ar- upplied to the cell potential control ?0 The cell poten-
tial control 70 can be controlled by potential bet 96
In a preferred form of automatic controls the apparatu~ con-
i~t- of two ~ection-~ analog circuitry for converting, condi-
tloning nd di~pl-ying lectrochemical 6ignal~ snd reagent hand-
llng olscuitry for utom tio ~ple h ndling
Sh- ~naly-ia cyol- 1- oontroll-d by two -qu ntial t~0~- ~7
~h- fir-t timing lnt-rval (30 econd~ init~at-d aft-r th-
tart nalysi- witch a8 i~ d0pre~aed Thia ~equence ia u~ed
to brlng the c-ll to quilibrium ~he econd interval ~20 econd-)
1- the conoentrat$on ~ a~urement During tbls time the electroche -
lc-l lgn~ conv rted and d~played In a preferred for~ th
~5A-117 CIP -29-
apparatu- di~play~ the ~count down~ or ~count up" digitally
durlng th- me~-urement Coll reerence potential i~ controlled
by potentla-tat clrcult 70 and i8 ~et by control 96
Thi- potontial i8 applied between the reference electrode segment
~5 and activo electrode segment 42 A difference potential i~
oon betweon active electrode ~egment 43 and reference electrode
~gm-nt ~5 This differenc~ potenti~l iB Bet by off~et 2 control
oporating on current convsrtor ~ubtr~ctor 75 The equival~nt
pot~nti-l become- lE~t 1 Eoffsetl
During thQ me~suroment interval the cell currents are fed
lnto curr nt-to-voltago convertor olrcu~t 75 nd gained con-
troll-d by potontiom ter- Galn 1~ nd ~Ga~n 2~ Tbe differonce
of tbo ra-ulting voltagQ~ i- taken nnd fed lnto the accumulator
circuit 76 and inteqrated during t~e mea~urement interval ~he
intogr~ted Yolt~go then ha~ the ~autoblank~ value ubtra¢ted
from it nd gained by calibrate circuitry 77
Tbo ro~ultant v~lue i8 then di~playod on the readout 80 in
dlr-ct unlt- of microgrum- of lron per lOOml ~g~) of ~rwm
Whon the digital dl-play ~tops counting the reagent or electrolyte
oont~ining the sa~pl- i~ flushed into container 2~ and a new
upply of reagont or eloctrolyte ie introduced into the c~ ron
cont~inor 29 Wh n the t~rt test indicator 2~ light- up agaln,
th- apparatus i~ roady for a next ~umple The entire te~t ~ay t ko
lo-a th n ono minut-, the large~t portion of which is tho pre-
li~inary ~xlng t~ra
ESA-117 CIP -30-
R-ag~nt or l-ctrolyte can be automatically charged to the
c-ll ln a number of way~ One way i~ to automatically fill the
c-ll ~hen tho unit wltch0s from the ~t-ndby to run position~ no-
th-r w-y 1- to uto~utically fill the cell at the end of each ana-
ly~i- cyclo
Pump nd valv- timers are ~et ~on~ by tbe control ~ynchroni~er
85 fro~ a trigger lgnal received by the standby control ~witch
or th- naly-i- cycl- timer Tbe ~olenoid valve 63 i~ u~ed to
~ontrol re~gent flow into the c~ll A pump supplie~ nominal
pro~ur ~- g p-l) to reagent ~upply 62 and a nominal e g
vacuu~ (17~ Hg) to drain re~ervoir 69 The pressure force~ cloan
r-ayont throuqh th- ~alve lnto cell 27 This incrua~e in cell
volu~o 1- tak~n ofi through the draln l~no to th~ drain re~-rvoir
69 The re-~-nt lnlet valve 1~ timed on for a shsrt time, e q
3 ~econds, and t~ pump 1~ left on for an additional 2 ~econd~ to
dr-in any exces~ r-aqent above a set level rom the cell
A fl~w ~ensor 68 con~i~ting of optical ~ensor 56 and
flo~ en~e circult 90 monitor~ the cell drain line 65 during
the reagsnt flu~hing cycle If there i~ no reagent flow or if a
low umount of re~q-nt pa~-e- through the cell, the flow ~en~e
circuit 90 will ro--t the pump and valv- timsr~ nd thu~ prevent
the ~tart of n n~ly-i~ An audio alarm and ~ndicator light
~light 23) may ~l-o be ctivated at thi- time T~u~, a new cycle
cannot be tarted until the operator places the instrument in the
tandby oondition whlch r-~ot- the ilow ~en~o circuit 90
ESA-117 CIP -31-
1~19~4:~
~ be flow ~en~c clrcult 90 compri~e~ an optical ~en~or
(LED 55 and phototr~nai-tor a60embly 56, Fig 5) and i~ placed
~t tb~ c-ll dr~in lln- ~n operation, the output f rom f low ence
circuit 90 ch~nges fro~ ~ low voltage level ~line empty) to a
higber voltage level (reagen~ flowing) Thls level change iB ~en-
aed ~nd integrated du~ing thB fir~t 4 ~econd~ of the reagent cycle
I~ thu integrator ~oltage i~ below a preset level at the end of the
4 econd ~nterv~l, in-trument lockout iu activated
~ n tbe outoblanking operation, wh~n a blank conecntration
reading i- taken and $o to be nulled out of future readings,
th- unit witched from ~run~ to~sutoblankU The autobl~nk
et witch i6 depre~--d, ~tarting a 4 ~econd timer The binary
codod decimal output from the display latched in the circuit
~bia ~CD number i~ tben convurted from a digital to an analog
ignal
An ~nalog voltage of correct polarity and maqnitude i~
E5A-117 CIP -32-
,
11;~9~
~-d ~o th- ealibration circuitry and ~ubtracted from the con-
e-ntr~tion analog vol~sge rosulting in a ~ero output to the
di-pl~y
Alt rn-tively, th- apparatu6 may be ~ade to operate uto-
Dat~eally, g by m~an~ of switching u~ing a ~croproces~or
~n u¢h oa--, for a known ~ubstance, tape containing ~n-tru~ent
~n-truction- would b inssrted in tho mlcroproco~or, which the~
-l-ct~ tho re~gont to be added to the eell, and the electrode
potent~al- She roDult~ could then be di~played for visual obaer-
~ation a- on CR~ tube or printed out, or the result, may be read
into ~cnory for ~ppropriate mathematical manipulation and then
di-pl~yod For n unknown ubstance, the instrument could be
¢o~-truoted to eonnoet a plurality of eloetrically diwrete
aetiv t--ting eleetrodes at different olectrical potentials to
thu- r-produce an entire current voltage curve which can then be
oo~p r-d to current voltage curve~ for known eloctroactive peci-
~
~Sh~ CI~ -33-
9~4~
The ~d-nti~ication of the unknown specie~ can be deter~ined by
~tchi~g curve ~hape~ while the amount of an electroactive 6peciea
pra-~nt ln the 9a~pl- can be determined from the ar~a under
v-riou~ ections of the curve for the unknown ~ore ~pecifically,
ri9. 7 lllu-trate~ a typical current ver~u~ potential chart
obtai~ed in ccor~anc- with thi~ invention In this graph, the
bor~ontal aYi~ indicate~ the difforence potential, in volt~, of
~or~ln~ lectrode- at Lncr-a-ingly more positive potentidl~ with
~e-p-ct to tho ilver/~ilver chloride reference electrode ~he
vortlc~l axi~ reprecont~ tho anodic current, in microampere~,
at tho indicated pot nt~al ~he wave~ of the current versu~
pot-nt$~1 curve- indicate a cbarp cbange ln current due to
tho chuAge in concentration of each electroactive ~pecie~ B it
reactc ln th~ reagent. gince the potantial ~t which a particular
l-ctroactlvo peciea ro~ctY iB characteristic of a particular
ESA-117 CIP -3~-
11~9~
p ci-- in particular reagent, the electroactive ~peci~ pre~ne
ln tb- ~mple ar- ~ - adily id~ntifi~d Al~o, ~ince th~ pr~eno~ of
~ny lnt-rf-rrin~ lsctroactive ~pecio~ i~ cancelled out by the
ol-ctronics, the area- under the peaks are disectly rel~ted to
the total amount of and thu~ t~ th~ concent~ation o~ each
l~ctroactive ~pocie~ in the ~amplo colution
A foature and advantage o~ tho pre~ent invention i~ that
~l-ctroch~mical ~e~surements are made of charge transfer re~c~ion~
ub~tantially ~imultaneously with the occurrance of the reaction~
Sbu- el0ctrochemic61 m~asurement~ in Accordance with the present
lnvention can be carried out imultaneou~ly on mo~e than one ~ub-
t~nc- of lntere~t in a ~ample by application of ~uitable electrical
Fotentlal- on tb- variou~ active electrode ~egments, ~nd t~ro~gh
lgnal orting For example, a blood ~mple may be te~ted ~im~l-
t-noou~ly for l~ad ~nd chromium
t8A-117 CIP -35-
' ' .
V-rlou- oth-r oh n~- wil~ be o~vio~ to ~ne -~killed i~ the
art rOr xa~pl-, th- ctive lectrode ~egment~ h~ve been
lllu~tr~t-d ~- compri~in~ continuou~ rings or bands~ how~ver,
on- klll-d 1~ th- rt will recognizo that the active olectrode
eq~ nt- ~ay comprl-o lndividual dot- or egment~, or a eri-a
of dot- or -qm n~- ~oreover, whil- tho l-ctrode prefer-bly
oom~ri--- a hollow cyllndrical, thu ~milar advant~ges may b~
chi-v d by ~ap~ng th- lectrod- a- a hollow cono and by pro-
~ldlnq a ~tirror o~ mating i~e and ~hape Furthermore, oee or
~oro ~GtiVo l-ctrod~ ogment~ may ~o ~dded to ch~nge the
el-ctroa- ~r-~ t ~olected voltage potenti~l~ 80 ~8 to reduce or
null out ot`herwi-- ~ery large ignal~ from lnterferring electro-
actlv p cl--, or r-~gont ~ignal~ in the ca~e o~ very dilute
olutlon-, and thu- lncrea~e ~en~itivity to a particular electro-
~b-o~c~l ~p cles of intere~t, ~nd to balance ~gnal~ ~oreover,
n-ither th- r~feroAc- olectrode nor the counter or power elec-
trod- n -d bo ~ount-d - egment~ or electrode 34, but can be
cpar t ly pro~ld d ~n known manner ln cont~ct with the ~olution
~ lng ~ -Yur d ~or xumple, the referenc- olectrode and/or th~
OOUAt-r l-ctrodo ~ y b- for~od ~n pluy ~6 Al~o, the apparatu~
m y co-prlc r- th ~ on- r-f-r-nc- l-ctrode nd~or mor- than
on~ oount-r lootrod- The apparatu- oould ~l~o b~ adapt d to
op ~at ~ low o-ll to thu- provido a continuou~ profil~
o~ proc~
~-117 CIP -36-
In d~ition to the foreyoing, it will be under_tood, ff
~hown ln ~lg 8, th~t the olectrochemical ~yQtem may compri~e
p~lr of ~ide-by--ido cell as~emblioY 27A and 27~ Cell
~ mbl~-~ 27A and 27~ re simllar to cell a98e~bly 27 a~ &bove
d--cr~bad In thi~ latter ca~e on~ of the cell asiemblie~, c g
bly 2~A iS ds-lgned to be the ~nAly~ cell wh~le the oth~r
o-ll e--~cbly 27B i- ~ blank correction cell ~ach active
l-otrod~ m-nt in oell ~embly 27A i8 p~ired wit~ ~
oor~ -pondln~ ~otiv l-ctsodc egm-nt in cell a~-umb~y 27B at
tb- n~Q ~otonti~l~ In use ample cont~in~ng reagent ~
i~ected lnto cell a~sembly 27A whil~ pure reagent i6 injocted
into coll assembly 27~ ~he cell contents are ~tirred at
~ub~tantially identlcal r~tos, and chargo tran~fer ~ig~al~
~ori~e~ a- bofore The signals from the active cell ~egment~
~n tho t~o cell ~se3blie~ 27A and 27~ ~re ~ummed, e g
- by ubtracting the ~ignal~ derivod Srom cell a~b~mbly
27B ~rom t~e signal~ deriv~d fro~ coll as~embly 27A, with
th- r0-u~t that 11 background ~ignalo are e~entially
null-d An ad~ nt~ge of employing two imilar cell
~--~mbli-9 i- thae ignal~ ro~ulting from i~puritie~ in
th r-~g-nt- ~r- null-d~ Al~o, ~ottl~ng o~Sect- re~ulting
fro~ ~ chnn~- of rcagont, ol-aning cycl--, ot¢ , are al-o
~ull-d C~ bl~-s 27A ~nd 27~ may co~pri~e identical
~ctlv- loctrod- -a~, or one oS the coll a~-~ablie~, ~typically
~S~-117 CIP -37-
th- ~lank corr~ction ooll au-embly 27a) may bo ~ad~ ~mallor th~n
th- ansly~i~ c~ll a~-enbly ~7A and the differences in ~ctiv~
l-ctrod- r-~ compon~at~d olectrically in known manner A~ ~un-
tion-,a ~bov-, th- tirr~ng rate in cell a~oembly 27A hould bo ~ub-
-tant~ally ~dentic~l to tbe ~tirring ratc in cell a~oumbly ~7a
Sh~ pl-~t way to ~s-ure ~atching i~ to m~c~n~cally connect
th- tirri~g ~n~nr 5pA ~d 50~ in th~ two a~ bli~ 27A ~d
27~ to ~ ~n~l- ~oto~
A~t-rnativ ly, th- ~wo oell ~a-mbli~- ~ay bo tack-d on-
on top of noth-r, g a~ hown ~n Fig 9 ~t 27C an~ 27D, ~nd
th- o-ll oontont- tlrrod by a ~tirring mo n- 50C ~nd 50D
w~icb ar- ~ounted on a oo~mon ~haft 51A Obviou~ly, care
~ust bs ~aken to prevent fluid transport betw~en the two c~ll
a---mblies 27C und 27D ~hi~ can ~o as~urod by clo~e manufacturing
tol-ranc-~ nd with oaling me~ns ~ are well known to ona
klllc~ in the art A~ before, groov~s 52C and 52D are
prov$ded on ~tirring means 50C and 50D, r~epectively If deaired,
th--o yroove~ mdy b- ~ade to run in opposite dire~tion~ to on~
nother to ~in~ iluid tran~port b~tw~-n coll 27C ~nd 27D
partlcular ~-ature nd advant-ge of th~ pr~ent invent~on
~hich r--ult- from tho u-o o~ ~n l~ctrode h~vlnq ~ plur~l~ty
of activ~ t sti~g l-ct~od~- t dif~ar~nt potential- in accord~nc-
~ith th- pre-ent invontlon i~ the ellmin~tion of cap~citanc-
i~nal~ whi~h wero lnh-rent ln prior ~rt olectrochem~cal
~eaaur~ng in w~ich tb- potonti-l on an lectrode ia changed
to obt~ln a ~oa~urc~ nt~
8tlll other foature4, advantag-~ and objecto ~ill bo obviou-
to oao ~ d ~n the ~rt
~SA-117 CI~ -3
