CA1204048A - Method for the detection and removal of substitution labile transition metal ions - Google Patents
Method for the detection and removal of substitution labile transition metal ionsInfo
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- CA1204048A CA1204048A CA000400912A CA400912A CA1204048A CA 1204048 A CA1204048 A CA 1204048A CA 000400912 A CA000400912 A CA 000400912A CA 400912 A CA400912 A CA 400912A CA 1204048 A CA1204048 A CA 1204048A
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- metal ions
- pyridinethiol
- chelating
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N31/00—Investigating or analysing non-biological materials by the use of the chemical methods specified in the subgroup; Apparatus specially adapted for such methods
- G01N31/02—Investigating or analysing non-biological materials by the use of the chemical methods specified in the subgroup; Apparatus specially adapted for such methods using precipitation
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- Pyridine Compounds (AREA)
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Abstract
ABSTRACT OF THE INVENTION
A method of detecting substitution labile transition metal ions from an aqueous solution. The method comprising the step of adding an effective amount of an ionizable 2-pyridinethiol-1-oxide salt. The presence of said salt anion being compatible with the presence of or subsequent addi-tion of chelating or sequestering agents having a higher equilibrium content for the ion to be complexed than the salt anion whereby the presence of the ion is confirmed by a color change and the formation of a precipitate. The metal-pyridinethiol complex thus precipitated can be removed from solution by conventional unit operations, for example by filtration or centrifuging.
A method of detecting substitution labile transition metal ions from an aqueous solution. The method comprising the step of adding an effective amount of an ionizable 2-pyridinethiol-1-oxide salt. The presence of said salt anion being compatible with the presence of or subsequent addi-tion of chelating or sequestering agents having a higher equilibrium content for the ion to be complexed than the salt anion whereby the presence of the ion is confirmed by a color change and the formation of a precipitate. The metal-pyridinethiol complex thus precipitated can be removed from solution by conventional unit operations, for example by filtration or centrifuging.
Description
=~ ~
METHOD FOR THE DETECTION AND REMOVAL OF SUF~STITllTION
LABILE TR~NSITION METAL IONS
1. Description:
FIELD OF' INVENTION
- The present invention relates ~o the detection and~or removal of substitution labile transition metal ions pr~sent in aqueous solutions. More specifically, the metho~
described herein concerns the use of a 2-pyridinethiol-1-oxide anion to determine the presence of said transition metal ions and to facilitate their removal from solution by chelation. Most specifically, the present invention relates to the detection/removal of said transition metal ions from an aqueous solution also containing other che-lating agen~s, or from aqueous solutions into which other chelating agents will be added, the use of a 2-pyri~inethiol-l-oxide alkali salt being compatible with said other chelating agents.
BACKGROUND OF THE INVENTION
Industrial, household and cosmetic preparations are often sensitive to the presence of heavy metal ions; which iOllS interfere with active agents resulting in a ~imun.iti.on or loss of product effectiv~ness. The nature of the inter ference caused by the metal ions is varied, for example, the breakin~ of emulsions in furniture polishes, hand cr2ams or lotions, Friede~-Crafts reactions that affect fragranc~
stability, or xeduction in peroxide stability.
Metal ions which behave in this manner are the substi-tution labile transition metal cations, for example, some complexes of ferric and ferrous, and cupric ions. Substitu-.......
~4 tion inert cations, for example, the chromic ion, ~o not complex or transchelate with organic ligands, ancl therefo~e do not require removal from the aqueous solution. Whether an ion is substitution labile or substitution inert depends on the d orbital con~igura~ionl subs-titution inert ions being characterized by 3 and 8 d electrons in their outer shell. Transition metal ions having 4, 5 an~ 6 d electrons in the outer shell ~re also substitu~ion inert if complexed with strong field ligands such that the electrons in those d orbits are paired.
Substitution labile ion contamination in the prepara-tion of these products typically occurs during man~lfacture, the ions being present in the process water arriving from outside the facility battery limits. The contamination may also occur because of the nature of piping and equipment materials used witin the battery limits of the processiny ~aeility. Of course, if the magnitude o~ in-plant contamin-ation is too great, replacement of equipment may be more economical than removal of the ions by chemical/physical means. ~roduct contamination may occur during storage or shipment from the product containers, especially metal containers having a polymeric film that ean be seratched.
Past practice has sought to eontrol the dimunition/
loss in produet effectiveness caused by ion contamination by several means. Process water entering the facility can be treated by distillation or ion exchange, thereby removing the contaminants. A second method, often used in conjunction with water treatment, has been to incorporate within -the product composition a chelating agent that complexes the S
substitution labile transition metal ion thereby reducing offending physical or chemical interference. Typical chelating agents are alkali salts of nitrilotriacetic acid, , : ~ ~ !
. . , ~2~
ethylenediaminetriace-tic acid and the like. In cer~ain formulations the incorporation of these chelating agen~s are also necessary even though -the processing water and facility have been successEully purged of the substitution labile ions. Instances where the chelating agent would be required are where the product is shipped in containers which may allow the ions to enter into the product solution, where the product is used in an aqueous environment that may contain the metal ions, or where the chelating a~ent --itself is an active ingredient of the formulation.
Greater flexibility in the manufacture of the afore-said chemical preparations could be achieved if ~here was a simple method whereby the substitution labile ions could be identified prior to the use of the process water in the product batch. SimiIarly, the manufacture of these formulations would be simplified if the ions could be removed without resorting to expensive distillation and/or ion exchange methods. Because the formulations themselves may con-tain a chelating agent, it is critical that -the method used to detect or remove the substitution labile metal ions does not itself deactivate other ~helating agents present in solution or that are to be aclded to the final product formulation. The detection,/removal means should also be inert to the other active and non-active constituents;of the formulation, should be usable over a wide pH range, and should not exhibit off odors.
SU~ARY OF INVENTION
It is an object of this invention to provide a method for the detection and/or removal of substitution labile heavy metal transition ions from an aqueous solu-tionO
It is a urther object of this invention to provide a - -method for the detection or ~emoval of the aforesaid ions from an aqueous solution, which method is compatible with the presence of other chelating and sequestering agen~s.
The primary objec~ of the in~en~ion is to detect or remove the aforesaid me~al ions from an aqueous solution by the addition ofan effective amount of an ionizable salt of a 2-pyridinethiol-1-oxide compound, specifically an alkali salt of 2-pyridimethiol~l-oxide, the presencP of which does not interfere with the use of or incorpora$ion of other 10 chelating or sequestering agents.
These and other objects and advantages of the present invention will be readily apparent upon a reading of the detailed description of invention, a summary of which ~ollows~ .
The method of detecting the presence of a subs titution labile metal ion comprises the step of adding an effective amount of an ionizable salt of 2-pyridinethiol-1-oxide, the presence of said salt being compatible with the presence or subsequent addition of !helating or sequestering agents 20 having a higher equilibrium constant for the ion to be complexed than said salt anion. The presence of said ion is confirmed by the formation of a precipitate which typically is highly coloredu Removal of the complexed ion from $he a~ueous solution may then be accomplished by distillation, filtration, centrifuging, or ~ther means used to separate a solid ~rom an aqueous phaseO
- 4a -In one aspect the invention provides a method of deter-mining the prese~ce or absence of substitution labile transition metal ions in process water to be u~ed in the manufacture of chelating or sequestertng agent containing preparations, the method comprising the steps of (a~ con~acting said process water with an e~fective amount of an i onizable salt of
METHOD FOR THE DETECTION AND REMOVAL OF SUF~STITllTION
LABILE TR~NSITION METAL IONS
1. Description:
FIELD OF' INVENTION
- The present invention relates ~o the detection and~or removal of substitution labile transition metal ions pr~sent in aqueous solutions. More specifically, the metho~
described herein concerns the use of a 2-pyridinethiol-1-oxide anion to determine the presence of said transition metal ions and to facilitate their removal from solution by chelation. Most specifically, the present invention relates to the detection/removal of said transition metal ions from an aqueous solution also containing other che-lating agen~s, or from aqueous solutions into which other chelating agents will be added, the use of a 2-pyri~inethiol-l-oxide alkali salt being compatible with said other chelating agents.
BACKGROUND OF THE INVENTION
Industrial, household and cosmetic preparations are often sensitive to the presence of heavy metal ions; which iOllS interfere with active agents resulting in a ~imun.iti.on or loss of product effectiv~ness. The nature of the inter ference caused by the metal ions is varied, for example, the breakin~ of emulsions in furniture polishes, hand cr2ams or lotions, Friede~-Crafts reactions that affect fragranc~
stability, or xeduction in peroxide stability.
Metal ions which behave in this manner are the substi-tution labile transition metal cations, for example, some complexes of ferric and ferrous, and cupric ions. Substitu-.......
~4 tion inert cations, for example, the chromic ion, ~o not complex or transchelate with organic ligands, ancl therefo~e do not require removal from the aqueous solution. Whether an ion is substitution labile or substitution inert depends on the d orbital con~igura~ionl subs-titution inert ions being characterized by 3 and 8 d electrons in their outer shell. Transition metal ions having 4, 5 an~ 6 d electrons in the outer shell ~re also substitu~ion inert if complexed with strong field ligands such that the electrons in those d orbits are paired.
Substitution labile ion contamination in the prepara-tion of these products typically occurs during man~lfacture, the ions being present in the process water arriving from outside the facility battery limits. The contamination may also occur because of the nature of piping and equipment materials used witin the battery limits of the processiny ~aeility. Of course, if the magnitude o~ in-plant contamin-ation is too great, replacement of equipment may be more economical than removal of the ions by chemical/physical means. ~roduct contamination may occur during storage or shipment from the product containers, especially metal containers having a polymeric film that ean be seratched.
Past practice has sought to eontrol the dimunition/
loss in produet effectiveness caused by ion contamination by several means. Process water entering the facility can be treated by distillation or ion exchange, thereby removing the contaminants. A second method, often used in conjunction with water treatment, has been to incorporate within -the product composition a chelating agent that complexes the S
substitution labile transition metal ion thereby reducing offending physical or chemical interference. Typical chelating agents are alkali salts of nitrilotriacetic acid, , : ~ ~ !
. . , ~2~
ethylenediaminetriace-tic acid and the like. In cer~ain formulations the incorporation of these chelating agen~s are also necessary even though -the processing water and facility have been successEully purged of the substitution labile ions. Instances where the chelating agent would be required are where the product is shipped in containers which may allow the ions to enter into the product solution, where the product is used in an aqueous environment that may contain the metal ions, or where the chelating a~ent --itself is an active ingredient of the formulation.
Greater flexibility in the manufacture of the afore-said chemical preparations could be achieved if ~here was a simple method whereby the substitution labile ions could be identified prior to the use of the process water in the product batch. SimiIarly, the manufacture of these formulations would be simplified if the ions could be removed without resorting to expensive distillation and/or ion exchange methods. Because the formulations themselves may con-tain a chelating agent, it is critical that -the method used to detect or remove the substitution labile metal ions does not itself deactivate other ~helating agents present in solution or that are to be aclded to the final product formulation. The detection,/removal means should also be inert to the other active and non-active constituents;of the formulation, should be usable over a wide pH range, and should not exhibit off odors.
SU~ARY OF INVENTION
It is an object of this invention to provide a method for the detection and/or removal of substitution labile heavy metal transition ions from an aqueous solu-tionO
It is a urther object of this invention to provide a - -method for the detection or ~emoval of the aforesaid ions from an aqueous solution, which method is compatible with the presence of other chelating and sequestering agen~s.
The primary objec~ of the in~en~ion is to detect or remove the aforesaid me~al ions from an aqueous solution by the addition ofan effective amount of an ionizable salt of a 2-pyridinethiol-1-oxide compound, specifically an alkali salt of 2-pyridimethiol~l-oxide, the presencP of which does not interfere with the use of or incorpora$ion of other 10 chelating or sequestering agents.
These and other objects and advantages of the present invention will be readily apparent upon a reading of the detailed description of invention, a summary of which ~ollows~ .
The method of detecting the presence of a subs titution labile metal ion comprises the step of adding an effective amount of an ionizable salt of 2-pyridinethiol-1-oxide, the presence of said salt being compatible with the presence or subsequent addition of !helating or sequestering agents 20 having a higher equilibrium constant for the ion to be complexed than said salt anion. The presence of said ion is confirmed by the formation of a precipitate which typically is highly coloredu Removal of the complexed ion from $he a~ueous solution may then be accomplished by distillation, filtration, centrifuging, or ~ther means used to separate a solid ~rom an aqueous phaseO
- 4a -In one aspect the invention provides a method of deter-mining the prese~ce or absence of substitution labile transition metal ions in process water to be u~ed in the manufacture of chelating or sequestertng agent containing preparations, the method comprising the steps of (a~ con~acting said process water with an e~fective amount of an i onizable salt of
2-pyridinethiol-1-oxide, said chelating or sequestering agent in the preparations being selected from the group consisting of phosphate salts, citrate salts, nitrilotriacetic acid and salts thereof, and ethylenediaminetetraacetic acid and salts thereof, the presence of the anion of the ionizable salt of 2-pyridinethiol-l-oxide being compatible with said chelating or sequestering agent, which agent has a higher equilibrium constant : for said subs-titution labile transition metal ions than fox the salt anion, and (b) observiny whether a precipitate is formed by reaction of said metal ions and said salt anion, whereby the ., presence of said substitution lab~le transit~on metal ion is confirmed by the formation o~ a precipitateO
.~ In another aspect the invention provides a method of determining the suitability of process water to be used in the manufacture of industrial, household, or cosmetic pre-parations that contain a chelating or seques~ering agent, the method comprising the steps of (a) contacting said process water to be used in the manufacture of said chelating or sequestering agent containing industrial, household, or cosmetic preparations with an effective amount of an ionizable salt of 2-pyridinethiol-l-oxide, said process water being unsuitable in the presence of substitution labile transition metal ions selected from the group consisting o~ Fe , Fe , Mn , Cr ~ or mi~tures thexeof, said chelating or sequestering a~ent in the preparations being selected from the group consisting o~ phosphate salts, citrate - ~b salts, nitrilotriacetic acid and salts thereof~ and ethylenediaminetetraacetic acid and salts thereof, the presence of the anion of the ionizable salt of 2~pyridinethiol-oxide being compatible with said chelat;ng or sequester.ing agent, which agent has a higher equilibrium constant for said sub~
stitution labile metal ions t~an ~or the salt anion; (b) observing whether a precipitate is formed by reaction of said substitution labile transition metal ions and said salt anion;
and (c) rejecting said process water for use in the manufacture of said preparations i~ a precipitate is formed.
~ETAILED DESCRIPTIiON OF INVENTION
.
In accordance with this in~ention, it has been found that ionizable salts o~ 2-pyridinethiol-1-oxide (herein after pyridinethiol) when added to an aqueous solution containing substitution labile transition metal ions, 1 C +2 Ti~3 V~3 Mo~5~O+6~CU ions, forms a highly colored precipi~ate ~hereby indicating the presence of said ions. It has also been found, that the prese,lce of the pyridinethiol in the agueous solution is compatible with many chelating and sequestering agents used currently in the production of household, industrial, and cosmetic preparations, which compatibility is not predicted by chemical or thermodynamic rate laws.
The preferxed form of pyridinethlol used in the detection of the substltut.ion labile ions has the structural f~rmula in tautomeric form as follows:
[~5 b o where X is an alkali Group I metal of sodi~m, postassium, and lithium. Pyridinethiol compounds are gol~ under the Omad.ine trademark, e.g., Sodium Omadine~l/ by Olin Chemicals, Stamford, Connecticut. As disclosed in ~'R~te and Mechan~
isms of Substitution of Inorganic Complexes in Solukion", Ho Taube Chemical Reviews, pages 69-126 (1952), the kinetic~ governing rates of chelation are determined primarily by d orbital configurationO Metal complexes requiring positive crystal field stabilization enerqy in their activated complex exchange inner sphere ligands very slowlyO Such complexes are substitution inert.
Metal complexes possessing 3 and 8 d electrons in thei.r outer shell are substitution inert a Finally~ transition metal ions poss2ssing 4, 5 and 6 d electrons in their outer shell that are complexed with strong field liyands, or example, metal complexes wherein 4~ 5 and ~ d electrons are paired, are also substltution inert~ Substitution i t ~ ~ v-~2 C ~3 Mo+3 W~3 Re+4;~n~4 a~e ~o~
} r~
~2~
subject to transchelation, and do not interEere in the chemical preparation under consideration. Metal transition ions not within the above definition of substitution inert ions are considered to be substitution labile, and will adversely affect the effectiveness of the household, industrial or cosmetic preparation. Depending upon the active ingredients in said preparations, the substitution labile ions can cause emulsified preparations to split into two phases, may combine chemically with expensive dyes, perfumes, or aromatic materials or may reduce the stability of other active ingredients. For this reason, many pre-parations include in their formulation a chelatinq agent or sequestering agent that sacrificially complex with these ions to decrease their interference. Even though the chelating or sequestering agents are added to the prepara-tion formula, flexibility in manufacture of these composi-tions would be enhanced iE the manufacturer could determine a priori whether the process water contains the substitu-tion labile ions. For example, if the process water does not contain these ions, the addition of the chela-ting agent may be dispensed with or a lesser amount of the chelating ayent could be used. Alternatively, if substantial amounts of the ions are present in the process water, the manufacturer could attempt to remove the ions by ion exchange or by the method of the present invention. However, -the method of the present invention for detecting the presence of the ions does place into solution and into the preparation an effec-tive amount of the pyridinethiol, a relatively weak chela-ting agent, and subsequen-t addition of other chelating or sequestering agents should not result in transchelation of these materials especially where the chelating or seques-tering agent is an active ingredient of the -formulation.
The rate of chemical conversion of reactants to products is determined empirically, and is described by chemical kinetics. Observed reaction rates are quantified as rate laws. Conversely, thermodynamic equilibrium measures the po~ential or driving force of a chemical reaction; i.e.
it predicts the tendency to form one reaction product over another~ The potential ox driving force of the chemical reaction is measured by equilibrium constants~ the larger the equilibrium constant, ~he greater the driving ~orce to obtaill equilibrium. The table below provides equilibrium constan~s for several transi~ion metal chelating agents 10 common7y used ana various metal ions, as well as the equil-librium constants fnr pyridinethiol.
Equilibrium Constants for M~t~- Co~
Chelating Liyands H Co~2 Fe~2 zn~2 2-Pyridinethiol-l-Oxide 4.5 10.0 4.7 11.3 Thioglycolic Acid 13.2 12.4 10.9 1599 Dithizone 15.0 13.0 - -Sodium Nitrolotriacetate(NTA) 13.0 14.2 8.8* 10.4*
20 Sodium Ethylenediamine tetracetate (EDTA) 10.2 16.2 14~3 16~4 Ethylene Diamine17.5 1400 9.6 11.5 1, 10-phenanthroline 4~9 l9o9 21~0 18.5 *Value for Kl Inspection of this Table indicates that the pyridinethiol anion is a relatively weak ligand, and thermodynamically, a metal complex of the pyridinethiol should react with ano~hex chelating agent havi.ng a higher equilibrium constant to form the metal complex of that chelating agent. Hence, an analysis of the thermodynamic data would predict that when pyridinethiol is in solution with another chelating agent specified in the table, complex forma-tion would always favor ~he chelating agent at the expense of pyridinethiol.
That is the use of the pyridinethiol to provide an indication of the presence of metal complexes would subsequf~ntly, after the addition of one of the above chelating agents, reduce or eliminate the effects of pyridinethiol. Based upon thexmodynamic considerations, the following chemical reac-tions should take place with octahedral metal complexes:
[M P3] ~nC _ ~ MCX+3P (13 Transchelation of pyridinekhiol Mx ~ 3p ~C - McX ~ 3p- t2)-Competing equilibrium n favoring the thermo-dynamic~lly more stable chelatlng agent while the reaction below should not be ~avored:
MCn ~ 3P ~ ~~ [MP ]X-3~ C 13) Transchelation to form the pyridine-thiol complex where ~5 is the substitution labile ion, C is a chelating agent, and P is a pyridinethiol anion, and where x is the charge of -the substitution labile ion and n is ~h~
coordinating power of the chelating agent.
Equa~i~n 1 indicates t.hat pyridinethi.ol complexe~ with a substitution labile transition metal ion and in a solution with a chelating agent (C~ having a higher equilibrium constant than the metal-pyridinethiol complex should trans-chelate to form a metal complex of said chelating agent~
Equation 2 indicates that a solutiol of metal ions, pyridi-nethiol, and a chelaking agent should preferenkially form the chelating agent-mekal complex. Equation 3 indicates that a c~lelating agen~-metal complex in sol.ution should not transchelate with pyridinethiol to form the pyridi-nethiol complex.
i These arguments are based upon equilibriurn constant data and provide a good basis for predicting the outcome of a chemical reaction. Thermodynamics can pred.ict the stability of a complex but cannot assure that a given reaction will in fact occur. As p.reviously stated, chemical kenitics emperically measures a reaction and quantifies it as a rate law whereas thermodynamics can only predict how fast equilibrium is obtained. if the reac~ion takes place. Analysis of the above principals with respect to stability and transchelation has not been considered heretofore, apparently because there has been no particular interest in the rate and equilibrium aspects of pyridinethiol chemistry vis-a-vis other chelating agents. From the examples hereinafter described, it was found that the pyri-dinethiol anion behaves in an unusual and unexpected way.
In the competing reaction of Equation 2, it was found that the substitutlon labile ion did not complex with the chelating agent, but rather formed an insoluble precip.itate 1i with the pyridinethiol: , M -~ nC -~ 3P -~ [MP3] ~-~ Cn (4) while the transchel.ation reaction of Equation 3 did in fact take place forming the pyridinethiol metal complex:
MCn + 3P ~ [MP3] l~ nC ~5) Again, the complex formed was insoluble. Thus, it can be seen that pyridinethiol/ which forrned a highly col~r~d pre-cipitate of the substitution labile metal ion, could be used to indicate the presence of the ion, ye-t would not ~2~
~ 10 -c;ubs~ ent-ly react- ~r krarll;ch~lat:n wit}l .~e~ etll-erir)~3 aclentr~
or chelating agents place~ in-to soIution.
. .
Detection of substitution labile transition metal ions can be accomplished by adding to the aqueous solution an effective amount o the pyridinethiol anion, followed by visual or instrumen-t observation of the forma-tion of the precipi~ate, ~ypically also associated with a color change. Precipitates possess a range of colors:
green (cupric); blue (ferrous); blue-grey (ferric). To remove the ions from solution, the pyridinethiol can be added to the process water to form the precitptate, followed by removal of the precipitate by conventional means, for example, by distillation, filtration or centrifuging. The amount of pyridinethiol anion added to the pro~ess water is dependent upon whether detection or removal is desired.
Where detection is the primary purpose of the acldition, the pyridinethiol can be added in small concentrations, it only being necessary to obtain the color change and the formation of the precipitate. ~ere removal of the substitution labile ions is desired, the pyridinethiol should be added in excess to ensure complete precipitation of all substitution labile ions in solution. `' The following examples illustrate reactions t4) and (S) described above.
~XAMPLE_I
Two solutions were prepared; solution A and solution B described below:
Solution A
Item Parts by Weight Deioni2ed Water 85.20 Sodium 2-Pyridinethiol-l-Oxide (40%) 0.03 Disodium Ethylenediaminetetra- -acetate Hydrate (EDTA salt) 0.04 Solution B
Item Parts by Weight Deionized water 14.705 Fe2~504)3 9~120 0.025 14.730 Solution B was added to a buret and titrated in-to Solution A.
Immediately after addition, a blue color appeared due to the formation of the ferric 2-pyridinethiol-l-oxide complex.
The order of addition was then reversed and the chelating agents were added to a solu-tion of ferric sulfa-te. As before, -the results were the same. Shortly after addition, the formation of an insoluble dark precipitate was noted. It was con-cluded that -the ferric ion did not preferentially complex with EDTA, even though equilibrium constant data would suggest thermodynamic driving force according to Equation 2 was in favor ofthe EDTA com,le~.
-EXAMPLE II
This example was conducted to test transchelation of a substitution labile metal ionO Two solutions were pre-pared; solutions C and D described below:
Solution C
Item Parts by Weight Deionized water 89.905 Disodium EDTA .2H2O 0.040 Fe2~S4)3 91~2 _0 025 89.970 Solution D
Item Parts by Weight Deionized water 10.000 Sodium 2-Pyridinethiol-l-Oxide (40%) 0.030 10.030 Ferric EDTA was formed and solution D containing the pyrid-inethiol anion titrated into solution C. Immediately after addition, a violet color was observed and a precipitate formed. As before, the order of addition was reversed, and with the same results. The conclusion is that the substitu-tion labile ferric EDTA complex transchelated to form the insoluble ferric 2-pyridinethiol-1-oxide complex which subsequently precipitated from solution according to reac-~ion (5).
F,X~M~
To test the subs~itution inertness of the ferrous and ferric ion when complexed with s-txong field ligands, the following experiment was conducted:
Solution E
Item Parts by Weight Deio~ized ~ater 89.94 K3Fe(CN)6 0.03 89~97 Solution F
Ite_ Par-ts b~ Weight Deioni7ed water 89.93 K4Fe(CN)6 3H2 0 04 89.97 Solution G
Item Par-ts by Weight Deionized water 10.000 Sodium ~-Pyridinethiol-l-Oxide (40%) 0.030 10.030 Solution G was added to solution E and solution F.
Unlike the results obtained with Examples I and II, after 40 minutes no color change or precipitate was observed.
.
.. .... .. ...
r~
This led -to the conclusion tha~ cyanide is a strong field ligand and will make the ferrous/ferric complexes substi-tution inert, i~e. cyanide causes the 5d and 6d electrons to be paired. When these compounds were added -to a solution of pyridinethiol anion, no reaction oc~urred because com-plex formation and subsequent precipitation can only occur with substitution labile transition metal ions. This was confirmed by preparing a solution of chromic chloride, which was added to a disodium EDTA solution. When solution G was added to this mix-ture, no color change or precipitate was observed after 30 minutes. This was because the chromic ion, d , is substitution inert and like ferric cyanide and ferrous cyanide will not transchelate with pyridinethiol.
EXAMPLE IV
The industrial applicatlon of the invention was tes~ed by the following experiment in which solutions H, I, J and K were prepared.
Solution H
Item Parts by Weight Deionized water 70.00 ~nion Carbide Silicone Emulsion LE-45~ (~0%) 5.00 Fragran~e 0.20 Sodium 2 Pyridinethiol l-Oxide (40%) 0.03 75.23 Soluti.on I
Item Parts by Weight Deionized water 14.710 CUS4 5H2 0.020 1~.730 Solution J
Item Parts by Weight Deionized water 14.685 Sn Cl2.2H~O 0.020 FeSO4.7H2O 0.025 14.730 Solution K
.
Item Parts b~ Weight Deionized water 14.70S
Fe2(So4)3 9H2 0.025 14.730 When solùtion I, J, or K containing substitution labile ferric, ferrous, or cupric ions was added to solution H
containing the pyridinethiol, an immediate color change was noted and a precipitate formed. The odor of the resultin~
mixture was noted after 30 minutes and after 18 hours, and such organoleptic condition was comparable to the control.
The colored precipi~ate ranged from green tcupric) to blue (ferrous) to grey ~ferric)~ Solu-tion H is typical of a light duty polishing cl.eaner containing a silicone emulsion.
r~
- 16 ~
Typically transition metal ions would destabiliz~ the silicone emulsion so that the water used in the formula-tion must be controlled.
The above description of Lhe invention is exemplary only, the scope of the invention not being limited except as described in the claims that follow.
.~ In another aspect the invention provides a method of determining the suitability of process water to be used in the manufacture of industrial, household, or cosmetic pre-parations that contain a chelating or seques~ering agent, the method comprising the steps of (a) contacting said process water to be used in the manufacture of said chelating or sequestering agent containing industrial, household, or cosmetic preparations with an effective amount of an ionizable salt of 2-pyridinethiol-l-oxide, said process water being unsuitable in the presence of substitution labile transition metal ions selected from the group consisting o~ Fe , Fe , Mn , Cr ~ or mi~tures thexeof, said chelating or sequestering a~ent in the preparations being selected from the group consisting o~ phosphate salts, citrate - ~b salts, nitrilotriacetic acid and salts thereof~ and ethylenediaminetetraacetic acid and salts thereof, the presence of the anion of the ionizable salt of 2~pyridinethiol-oxide being compatible with said chelat;ng or sequester.ing agent, which agent has a higher equilibrium constant for said sub~
stitution labile metal ions t~an ~or the salt anion; (b) observing whether a precipitate is formed by reaction of said substitution labile transition metal ions and said salt anion;
and (c) rejecting said process water for use in the manufacture of said preparations i~ a precipitate is formed.
~ETAILED DESCRIPTIiON OF INVENTION
.
In accordance with this in~ention, it has been found that ionizable salts o~ 2-pyridinethiol-1-oxide (herein after pyridinethiol) when added to an aqueous solution containing substitution labile transition metal ions, 1 C +2 Ti~3 V~3 Mo~5~O+6~CU ions, forms a highly colored precipi~ate ~hereby indicating the presence of said ions. It has also been found, that the prese,lce of the pyridinethiol in the agueous solution is compatible with many chelating and sequestering agents used currently in the production of household, industrial, and cosmetic preparations, which compatibility is not predicted by chemical or thermodynamic rate laws.
The preferxed form of pyridinethlol used in the detection of the substltut.ion labile ions has the structural f~rmula in tautomeric form as follows:
[~5 b o where X is an alkali Group I metal of sodi~m, postassium, and lithium. Pyridinethiol compounds are gol~ under the Omad.ine trademark, e.g., Sodium Omadine~l/ by Olin Chemicals, Stamford, Connecticut. As disclosed in ~'R~te and Mechan~
isms of Substitution of Inorganic Complexes in Solukion", Ho Taube Chemical Reviews, pages 69-126 (1952), the kinetic~ governing rates of chelation are determined primarily by d orbital configurationO Metal complexes requiring positive crystal field stabilization enerqy in their activated complex exchange inner sphere ligands very slowlyO Such complexes are substitution inert.
Metal complexes possessing 3 and 8 d electrons in thei.r outer shell are substitution inert a Finally~ transition metal ions poss2ssing 4, 5 and 6 d electrons in their outer shell that are complexed with strong field liyands, or example, metal complexes wherein 4~ 5 and ~ d electrons are paired, are also substltution inert~ Substitution i t ~ ~ v-~2 C ~3 Mo+3 W~3 Re+4;~n~4 a~e ~o~
} r~
~2~
subject to transchelation, and do not interEere in the chemical preparation under consideration. Metal transition ions not within the above definition of substitution inert ions are considered to be substitution labile, and will adversely affect the effectiveness of the household, industrial or cosmetic preparation. Depending upon the active ingredients in said preparations, the substitution labile ions can cause emulsified preparations to split into two phases, may combine chemically with expensive dyes, perfumes, or aromatic materials or may reduce the stability of other active ingredients. For this reason, many pre-parations include in their formulation a chelatinq agent or sequestering agent that sacrificially complex with these ions to decrease their interference. Even though the chelating or sequestering agents are added to the prepara-tion formula, flexibility in manufacture of these composi-tions would be enhanced iE the manufacturer could determine a priori whether the process water contains the substitu-tion labile ions. For example, if the process water does not contain these ions, the addition of the chela-ting agent may be dispensed with or a lesser amount of the chelating ayent could be used. Alternatively, if substantial amounts of the ions are present in the process water, the manufacturer could attempt to remove the ions by ion exchange or by the method of the present invention. However, -the method of the present invention for detecting the presence of the ions does place into solution and into the preparation an effec-tive amount of the pyridinethiol, a relatively weak chela-ting agent, and subsequen-t addition of other chelating or sequestering agents should not result in transchelation of these materials especially where the chelating or seques-tering agent is an active ingredient of the -formulation.
The rate of chemical conversion of reactants to products is determined empirically, and is described by chemical kinetics. Observed reaction rates are quantified as rate laws. Conversely, thermodynamic equilibrium measures the po~ential or driving force of a chemical reaction; i.e.
it predicts the tendency to form one reaction product over another~ The potential ox driving force of the chemical reaction is measured by equilibrium constants~ the larger the equilibrium constant, ~he greater the driving ~orce to obtaill equilibrium. The table below provides equilibrium constan~s for several transi~ion metal chelating agents 10 common7y used ana various metal ions, as well as the equil-librium constants fnr pyridinethiol.
Equilibrium Constants for M~t~- Co~
Chelating Liyands H Co~2 Fe~2 zn~2 2-Pyridinethiol-l-Oxide 4.5 10.0 4.7 11.3 Thioglycolic Acid 13.2 12.4 10.9 1599 Dithizone 15.0 13.0 - -Sodium Nitrolotriacetate(NTA) 13.0 14.2 8.8* 10.4*
20 Sodium Ethylenediamine tetracetate (EDTA) 10.2 16.2 14~3 16~4 Ethylene Diamine17.5 1400 9.6 11.5 1, 10-phenanthroline 4~9 l9o9 21~0 18.5 *Value for Kl Inspection of this Table indicates that the pyridinethiol anion is a relatively weak ligand, and thermodynamically, a metal complex of the pyridinethiol should react with ano~hex chelating agent havi.ng a higher equilibrium constant to form the metal complex of that chelating agent. Hence, an analysis of the thermodynamic data would predict that when pyridinethiol is in solution with another chelating agent specified in the table, complex forma-tion would always favor ~he chelating agent at the expense of pyridinethiol.
That is the use of the pyridinethiol to provide an indication of the presence of metal complexes would subsequf~ntly, after the addition of one of the above chelating agents, reduce or eliminate the effects of pyridinethiol. Based upon thexmodynamic considerations, the following chemical reac-tions should take place with octahedral metal complexes:
[M P3] ~nC _ ~ MCX+3P (13 Transchelation of pyridinekhiol Mx ~ 3p ~C - McX ~ 3p- t2)-Competing equilibrium n favoring the thermo-dynamic~lly more stable chelatlng agent while the reaction below should not be ~avored:
MCn ~ 3P ~ ~~ [MP ]X-3~ C 13) Transchelation to form the pyridine-thiol complex where ~5 is the substitution labile ion, C is a chelating agent, and P is a pyridinethiol anion, and where x is the charge of -the substitution labile ion and n is ~h~
coordinating power of the chelating agent.
Equa~i~n 1 indicates t.hat pyridinethi.ol complexe~ with a substitution labile transition metal ion and in a solution with a chelating agent (C~ having a higher equilibrium constant than the metal-pyridinethiol complex should trans-chelate to form a metal complex of said chelating agent~
Equation 2 indicates that a solutiol of metal ions, pyridi-nethiol, and a chelaking agent should preferenkially form the chelating agent-mekal complex. Equation 3 indicates that a c~lelating agen~-metal complex in sol.ution should not transchelate with pyridinethiol to form the pyridi-nethiol complex.
i These arguments are based upon equilibriurn constant data and provide a good basis for predicting the outcome of a chemical reaction. Thermodynamics can pred.ict the stability of a complex but cannot assure that a given reaction will in fact occur. As p.reviously stated, chemical kenitics emperically measures a reaction and quantifies it as a rate law whereas thermodynamics can only predict how fast equilibrium is obtained. if the reac~ion takes place. Analysis of the above principals with respect to stability and transchelation has not been considered heretofore, apparently because there has been no particular interest in the rate and equilibrium aspects of pyridinethiol chemistry vis-a-vis other chelating agents. From the examples hereinafter described, it was found that the pyri-dinethiol anion behaves in an unusual and unexpected way.
In the competing reaction of Equation 2, it was found that the substitutlon labile ion did not complex with the chelating agent, but rather formed an insoluble precip.itate 1i with the pyridinethiol: , M -~ nC -~ 3P -~ [MP3] ~-~ Cn (4) while the transchel.ation reaction of Equation 3 did in fact take place forming the pyridinethiol metal complex:
MCn + 3P ~ [MP3] l~ nC ~5) Again, the complex formed was insoluble. Thus, it can be seen that pyridinethiol/ which forrned a highly col~r~d pre-cipitate of the substitution labile metal ion, could be used to indicate the presence of the ion, ye-t would not ~2~
~ 10 -c;ubs~ ent-ly react- ~r krarll;ch~lat:n wit}l .~e~ etll-erir)~3 aclentr~
or chelating agents place~ in-to soIution.
. .
Detection of substitution labile transition metal ions can be accomplished by adding to the aqueous solution an effective amount o the pyridinethiol anion, followed by visual or instrumen-t observation of the forma-tion of the precipi~ate, ~ypically also associated with a color change. Precipitates possess a range of colors:
green (cupric); blue (ferrous); blue-grey (ferric). To remove the ions from solution, the pyridinethiol can be added to the process water to form the precitptate, followed by removal of the precipitate by conventional means, for example, by distillation, filtration or centrifuging. The amount of pyridinethiol anion added to the pro~ess water is dependent upon whether detection or removal is desired.
Where detection is the primary purpose of the acldition, the pyridinethiol can be added in small concentrations, it only being necessary to obtain the color change and the formation of the precipitate. ~ere removal of the substitution labile ions is desired, the pyridinethiol should be added in excess to ensure complete precipitation of all substitution labile ions in solution. `' The following examples illustrate reactions t4) and (S) described above.
~XAMPLE_I
Two solutions were prepared; solution A and solution B described below:
Solution A
Item Parts by Weight Deioni2ed Water 85.20 Sodium 2-Pyridinethiol-l-Oxide (40%) 0.03 Disodium Ethylenediaminetetra- -acetate Hydrate (EDTA salt) 0.04 Solution B
Item Parts by Weight Deionized water 14.705 Fe2~504)3 9~120 0.025 14.730 Solution B was added to a buret and titrated in-to Solution A.
Immediately after addition, a blue color appeared due to the formation of the ferric 2-pyridinethiol-l-oxide complex.
The order of addition was then reversed and the chelating agents were added to a solu-tion of ferric sulfa-te. As before, -the results were the same. Shortly after addition, the formation of an insoluble dark precipitate was noted. It was con-cluded that -the ferric ion did not preferentially complex with EDTA, even though equilibrium constant data would suggest thermodynamic driving force according to Equation 2 was in favor ofthe EDTA com,le~.
-EXAMPLE II
This example was conducted to test transchelation of a substitution labile metal ionO Two solutions were pre-pared; solutions C and D described below:
Solution C
Item Parts by Weight Deionized water 89.905 Disodium EDTA .2H2O 0.040 Fe2~S4)3 91~2 _0 025 89.970 Solution D
Item Parts by Weight Deionized water 10.000 Sodium 2-Pyridinethiol-l-Oxide (40%) 0.030 10.030 Ferric EDTA was formed and solution D containing the pyrid-inethiol anion titrated into solution C. Immediately after addition, a violet color was observed and a precipitate formed. As before, the order of addition was reversed, and with the same results. The conclusion is that the substitu-tion labile ferric EDTA complex transchelated to form the insoluble ferric 2-pyridinethiol-1-oxide complex which subsequently precipitated from solution according to reac-~ion (5).
F,X~M~
To test the subs~itution inertness of the ferrous and ferric ion when complexed with s-txong field ligands, the following experiment was conducted:
Solution E
Item Parts by Weight Deio~ized ~ater 89.94 K3Fe(CN)6 0.03 89~97 Solution F
Ite_ Par-ts b~ Weight Deioni7ed water 89.93 K4Fe(CN)6 3H2 0 04 89.97 Solution G
Item Par-ts by Weight Deionized water 10.000 Sodium ~-Pyridinethiol-l-Oxide (40%) 0.030 10.030 Solution G was added to solution E and solution F.
Unlike the results obtained with Examples I and II, after 40 minutes no color change or precipitate was observed.
.
.. .... .. ...
r~
This led -to the conclusion tha~ cyanide is a strong field ligand and will make the ferrous/ferric complexes substi-tution inert, i~e. cyanide causes the 5d and 6d electrons to be paired. When these compounds were added -to a solution of pyridinethiol anion, no reaction oc~urred because com-plex formation and subsequent precipitation can only occur with substitution labile transition metal ions. This was confirmed by preparing a solution of chromic chloride, which was added to a disodium EDTA solution. When solution G was added to this mix-ture, no color change or precipitate was observed after 30 minutes. This was because the chromic ion, d , is substitution inert and like ferric cyanide and ferrous cyanide will not transchelate with pyridinethiol.
EXAMPLE IV
The industrial applicatlon of the invention was tes~ed by the following experiment in which solutions H, I, J and K were prepared.
Solution H
Item Parts by Weight Deionized water 70.00 ~nion Carbide Silicone Emulsion LE-45~ (~0%) 5.00 Fragran~e 0.20 Sodium 2 Pyridinethiol l-Oxide (40%) 0.03 75.23 Soluti.on I
Item Parts by Weight Deionized water 14.710 CUS4 5H2 0.020 1~.730 Solution J
Item Parts by Weight Deionized water 14.685 Sn Cl2.2H~O 0.020 FeSO4.7H2O 0.025 14.730 Solution K
.
Item Parts b~ Weight Deionized water 14.70S
Fe2(So4)3 9H2 0.025 14.730 When solùtion I, J, or K containing substitution labile ferric, ferrous, or cupric ions was added to solution H
containing the pyridinethiol, an immediate color change was noted and a precipitate formed. The odor of the resultin~
mixture was noted after 30 minutes and after 18 hours, and such organoleptic condition was comparable to the control.
The colored precipi~ate ranged from green tcupric) to blue (ferrous) to grey ~ferric)~ Solu-tion H is typical of a light duty polishing cl.eaner containing a silicone emulsion.
r~
- 16 ~
Typically transition metal ions would destabiliz~ the silicone emulsion so that the water used in the formula-tion must be controlled.
The above description of Lhe invention is exemplary only, the scope of the invention not being limited except as described in the claims that follow.
Claims (17)
1. A method of detecting the presence of substitution labile metal ions, the method comprising the step of adding an effective amount of an ionizable salt of 2-pyridinethiol-1-oxide, the presence of said salt anion being compatible with the presence or subsequent addition of chelating or sequestering agents having a higher equilibrium constant for the ion to be complexed than the salt anion, whereby the presence of the ion is confirmed by the formation of a precipitate.
2. A method for the removal of substitution labile transi-tion metal ions from an aqueous solution, the method comprising the steps of adding an effective amount of an ionizable salt of 2-pyridinethiol-1-oxide, the transition metal ions being chelated thereby and forming a precipitate, the addition of said pyridinethiol being compatible with the presence of or the subsequent addition of chelating or sequestering agents of higher equilibrium constants, and removing said precipitate from solution.
3. The method of claim 1 or 2 wherein the ionizable salt of 2-pyridinethiol-1-oxide is the sodium salt.
4. The method of claim 1 or 2 wherein the chelating or sequestering agents are ammonia, ammonium salts, phosphate salts, citrate salts, nitrilotriacetic acid and salts thereof, and ethylenediaminetetraacetic acid and salts thereof.
5. The methods of claim 1 or 2 wherein the substitution labile transition metal ions are selected from the group con-sisting of ions with 0d, 1d, 2d, 7d, 9d and 10d electrons and combinations of same.
6. The methods of claim 1 or 2 wherein the substitution labile transition metal ions are selected from the group con-sisting of ions with 0d, 1d, 2d, 7d, 9d and 10d electrons and combinations of same, and wherein said ion is Ti+3, V+3, Cu+1, Au+1, Co+2, Ag+1, Os+6, Mo+5, Mo+6, Zn+2, Cd+2, Hg+2 or a mixture thereof.
7. The methods of claim 1 or 2 wherein the substitution labile transition metal ions are selected from the group con-sisting of ions with 4d, 5d and 6d electrons complexed in such manner that the d electrons are unpaired and combinations of the same.
8. The methods of claim 1 or 2 wherein the substitution labile transition metal ions are selected from the group con-sisting of ions with 4d, 5d and 6d electrons complexed in such manner that the d electrons are unpaired and combinations of the same, and wherein said ion is Fe+2, Fe+3, Mn+2, Mn+3, Cr+2 or a mixture thereof.
9. The method of claim 2 wherein the method for removal of the precipitate is centrifuging.
10. The method of claim 2 wherein the method for removal of the precipitate is filtration.
11. The methods of claim 1 or 2 wherein the precipitate is colored.
12. A method of determining the presence or absence of sub-stitution labile transition metal ions in process water to be used in the manufacture of chelating or sequestering agent contain-ing preparations, the method comprising the steps of (a) con-tacting said process water with an effective amount of an ioniz-able salt of 2 pyridinethiol-1-oxide, said chelating or sequester-ing agent in the preparations being selected from the group con-sisting of phosphate salts, citrate salts, nitrilotriacetic acid and salts thereof, and ethylenediaminetetraacetic acid and salts thereof, the presence of the anion of the ionizable salt of 2-pyridinethiol-1-oxide being compatible with said chelating or sequestering agent, which agent has a higher equilibrium constant for said substitution labile transition metal ions than for the salt anion, and (b) observing whether a precipitate is formed by reaction of said metal ions and said salt anion, whereby the presence of said substitution labile transition metal ion is confirmed by the formation of a precipitate.
13. The method of claim 12 wherein said process water has an essentially neutral pH.
14. A method of determining the suitability of process water to be used in the manufacture of industrial, household, or cosmetic preparations that contain a chelating or sequestering agent, the method comprising the steps of (a) contacting said process water to be used in the manufacture of said chelating or sequestering agent containing industrial, household, or cosmetic preparations with an effective amount of an ionizable salt of 2-pyridinethiol-1-oxide, said process water being unsuitable in the presence of substitution labile transition metal ions selected from the group consisting of Fe+2, Fe+3, Mn+2, Cr+, or mixtures thereof, said chelating or sequestering agent in the preparations being selected from the group consisting of phosphate salts, citrate salts, nitrilotriacetic acid and salts thereof, and ethylenediaminetetraacetic acid and salts thereof, the presence of the anion of the ionizable salt of 2-pyridinethiol-oxide being compatible with said chelating or sequestering agent, which agent has a higher equilibrium constant for said substitu-tion labile metal ions than for the salt anion; (b) observing whether a precipitate is formed by reaction of said substitution labile transition metal ions and said salt anion; and (c) rejecting said process water for use in the manufacture of said preparations if a precipitate is formed.
15. The method of claim 14 wherein the ionizable salt of 2-pyridinethiol-1-oxide is the sodium salt.
16. The method of claim 15 wherein the chelating or sequestering agent is selected from the group consisting of sodium nitrilotriacetic acid and sodium ethylenediaminetetra-acetic acid.
17. The method of claim 14 wherein said process water has an essentially neutral pH.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US32187681A | 1981-11-16 | 1981-11-16 | |
| US321,876 | 1981-11-16 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1204048A true CA1204048A (en) | 1986-05-06 |
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ID=23252413
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000400912A Expired CA1204048A (en) | 1981-11-16 | 1982-04-13 | Method for the detection and removal of substitution labile transition metal ions |
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| Country | Link |
|---|---|
| JP (1) | JPS5890166A (en) |
| AU (1) | AU551472B2 (en) |
| CA (1) | CA1204048A (en) |
| DE (1) | DE3242189A1 (en) |
| FR (1) | FR2516657A1 (en) |
| GB (1) | GB2109551B (en) |
| GR (1) | GR76778B (en) |
| IT (1) | IT1149120B (en) |
| NZ (1) | NZ202108A (en) |
| ZA (1) | ZA827991B (en) |
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| BR112015002155B1 (en) * | 2012-07-31 | 2020-06-30 | Arch Chemicals, Inc. | composition and method for preventing discoloration of compositions containing pyrithione |
| CN102866118A (en) * | 2012-09-14 | 2013-01-09 | 苏州金宏气体股份有限公司 | Method for detecting total content of heavy metal in high-pure and hyper-pure ammonia |
| CN114014422B (en) * | 2021-11-05 | 2023-09-26 | 济源职业技术学院 | Metal ion separation and enrichment system and method for separating and enriching cobalt (II) |
-
1982
- 1982-04-13 CA CA000400912A patent/CA1204048A/en not_active Expired
- 1982-10-07 NZ NZ202108A patent/NZ202108A/en unknown
- 1982-10-29 AU AU90009/82A patent/AU551472B2/en not_active Expired - Fee Related
- 1982-11-02 ZA ZA827991A patent/ZA827991B/en unknown
- 1982-11-04 FR FR8218477A patent/FR2516657A1/en active Pending
- 1982-11-08 GR GR69753A patent/GR76778B/el unknown
- 1982-11-15 IT IT49489/82A patent/IT1149120B/en active
- 1982-11-15 GB GB08232599A patent/GB2109551B/en not_active Expired
- 1982-11-15 DE DE19823242189 patent/DE3242189A1/en not_active Withdrawn
- 1982-11-16 JP JP57201002A patent/JPS5890166A/en active Pending
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| Publication number | Publication date |
|---|---|
| ZA827991B (en) | 1983-09-28 |
| AU9000982A (en) | 1983-05-26 |
| IT1149120B (en) | 1986-12-03 |
| JPS5890166A (en) | 1983-05-28 |
| AU551472B2 (en) | 1986-05-01 |
| IT8249489A0 (en) | 1982-11-15 |
| NZ202108A (en) | 1985-05-31 |
| GB2109551A (en) | 1983-06-02 |
| GR76778B (en) | 1984-09-04 |
| DE3242189A1 (en) | 1983-05-26 |
| GB2109551B (en) | 1985-08-14 |
| FR2516657A1 (en) | 1983-05-20 |
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