Classifications

• • C—CHEMISTRY; METALLURGY
  • C11—ANIMAL OR VEGETABLE OILS, FATS, FATTY SUBSTANCES OR WAXES; FATTY ACIDS THEREFROM; DETERGENTS; CANDLES
  • C11D—DETERGENT COMPOSITIONS; USE OF SINGLE SUBSTANCES AS DETERGENTS; SOAP OR SOAP-MAKING; RESIN SOAPS; RECOVERY OF GLYCEROL
  • C11D3/00—Other compounding ingredients of detergent compositions covered in group C11D1/00
  • C11D3/16—Organic compounds
  • C11D3/20—Organic compounds containing oxygen
  • C11D3/22—Carbohydrates or derivatives thereof
  • C11D3/222—Natural or synthetic polysaccharides, e.g. cellulose, starch, gum, alginic acid or cyclodextrin

Definitions

• the present invention relates to techniques for removing surfactants from various solutions and surfaces.
• Surfactants also known as detergents, are amphipathic compounds that have found wide use in removing dirt, oil, and the like from various surfaces. The resulting surface, however, is generally not free of contaminating surfactant compounds since there is a tendency for the surfactant molecules to stick to the surface being cleaned.
• rinsing agents A number of agents have been proposed for re­moving detergent from surfaces being cleaned. These are generally known as rinsing agents and most often contain a non-ionic or an ionic surfactant. Such tech­niques, however, often just replace one surfactant with another. Other components of rinsing agent composi­tions, including starch degradation products such as dextrin, have been proposed for removing calcium ions from surfaces and for preventing calcium deposits. However, there remains a need for further development of rinsing agents capable of removing surfactants from surfaces.
• a method of removing surfactants from surfaces and from solutions in which a cyclodextrin is contacted with an environment containing a surfac­tant, and the cyclodextrin-bound surfactant is then separated from the environment.
• the environment is typically an aqueous solution from which a surfactant is being removed or is a surface previously contacted (washed) with a surfactant.
• the cyclodextrin can be provided in either soluble or insoluble form.
• an aqueous solution of a cyclodextrin is con­tacted with a previously washed surface in order to re­move surfactant on that surface.
• the cyclodextrin is provided in an insoluble form for removing surfactants from solution or from surfaces, particles, or dissolved materials present or in contact with a solution.
• Cyclodextrins are cyclic amyloses. Three types are known: a cyclohexaamylose ( ⁇ -cyclodextrin), a cycloheptaamylose ( ⁇ -cyclodextrin), and a cycloocta­amylose ( ⁇ -cyclodextrin). It was previously known that these cyclic amyloses form inclusion compounds (clath­rates) and are capable of trapping a number of differ­ent organic molecules. However, the use of cyclodex­trins to trap surfactants and remove them from a solu­tion or from a surface was not known prior to this in­vention. Such use is unexpected in view of the amphipathic nature of surfactants.
• Cyclodextrins are well known compounds and are commercially available. For a description of their properties and methods of production, see, for example, Bender et al ., Cyclodextrin Chemistry, Springer-Verlag, New York, 1978 (a 96-page book); French, Adv. Carbo­hydr. Chem. (1957) 12 :189-260: Thoma et al ., Starch: Chemistry and Technology, Vol. 1, Whistler et al ., Eds., Academic Press, New York, 1965, pp. 209-249: and Cramer et al ., Naturwiss. (1967) 154 :625-635. The compounds are naturally occurring and are obtained from the action of Bacillus macerans amylase on starch.
• Cyclodextrins can be used to remove any deter­gent from a solution or solid surface.
• the mode of ac­tion is not certain, although it appears that at least a part of the detergent molecule is trapped into the interior space of the cyclodextrin. However, it is not clear whether all of the detergent molecule must be ac­commodated within the interior space. An exact fit does not appear to be necessary since different cyclo­dextrins will remove the same detergent from an environment.
• cyclodextrins are effective in removing surfactants, advantages are achieved by matching the size of the surfactant to the size of the interior space of the cyclodextrin.
• Large surfactants such as those derived from cholic acid, are therefore most readily removed using ⁇ -­cyclodextrin, which has the largest interior space.
• Smaller surfactants such as fatty acid salts and fatty sulfonates, are most readily removed with ⁇ -­cyclodextrin, which has the smallest interior space of the three cyclodextrins.
• a cyclodextrin in a form which can be readily separated from the environment from which a surfactant is being removed, preferably by a phase separation process (e.g., filtering).
• a phase separation process e.g., filtering
• soluble cyclodextrins dissolved in aqueous solutions are particularly suit thoughable for use as rinsing solutions to remove surfactants from solid surfaces.
• Soluble cyclodextrins are less useful in removing surfactants from solutions as the cyclodextrin-surfactant inclusion complex tends to remain in solution.
• cyclodextrins attached to a solid surface are more useful for actually removing surfactants from solution rather than neutralizing surfactant molecules in solu­tion.
• a solid par­ticle or otherwise in a solid phase allows easy separa­tion of phases by filtration or similar techniques. Numerous techniques have been developed for binding biological molecules, such as cyclodextrins, to solid surfaces, and any known or hereafter discovered tech­niques can be used.
• Such techniques generally involve formation of a covalent bond between a hydroxyl group of a cyclodextrin and either a reactive group on the surface of the solid or one end of a bifunctional mole­cule, the other end of which forms a covalent bond to the solid surface.
• Functional groups are typically present on the solid surface or the surface can be mo­dified to contain functional groups capable of entering into covalent-bond-forming reactions. For example, amino and/or carboxy groups are present at the termini of polyamides. Hydroxyl groups are present in cellulo­sic materials.
• the benzene ring of polystyrene can be modified to contain functional groups such as hydroxyl or chloromethyl groups. Many organic surfaces can be oxidized to form carboxylate groups.
• cyclodextrins Since the surfac­tant-removing capacity of cyclodextrins is insensitive to conformational changes, it is well within the skill of an ordinary chemist to covalently link a cyclodex­trin to a functional group on a solid surface using a bifunctional reagent.
• Commercially available cyclo­dextrin polymers are also available. When formed into beads or other forms of suitable size, the polymeric cyclodextrin can be separated from solution by filtration.
• microporous materials having cyclydextrins bound to the pore walls provide a greatly enhanced surface area on which binding can take place, since the actual surface of the solid will be significantly larger than its exterior gross surface.
• Suspensions of solid-bound cyclodextrins will also typically be useful in removing surfactants from surfaces since contact of such an aqueous suspension with a surfactant-contaminated surface initially re­sults in dissolution of some or all of the surfactant into the aqueous solution.
• the presence of a surface-­bound cyclodextrin in such a suspension shifts the equilibrium of this dissolution reaction (provided sufficient cyclodextrin is present) until the surfac­tant has been essentially removed from the contaminated surfaces.
• the surface in question can be the surface of a biologically active molecule, such as an enzyme or other protein, in solu­tion.
• any amount of cyclodextrin reduces the amount of surfactant on a surface being treated. Accordingly, use of any amount of cyclodextrin to re­move surfactant falls within the scope of the broadest aspects of the present invention. However, it is pre­ferred to use a molar excess of the cyclodextrin in order to remove trace amounts of the detergent without requiring excessive equilibrium times.
• sat­isfactory rinse solutions can be prepared as aqueous solutions containing from .01% (w/v) cyclodextrin up to the solubility limit of the cyclodextrin being used.
• Different degrees of surfactant removal are achieved by varying the rinse procedure, with multiple rinses and larger amounts of rinsing agent being used to achieve the best removal of surfactants.
• the amount used can like­wise vary over a wide range with satisfactory results.
• surfactants can be removed from surfaces and solutions using cyclodextrins.
• suitable detergent compounds which can be removed in accordance with the present invention include the following:
• Water-soluble soaps such as the sodium, po­tassium, ammonium and alkanol-ammonium salts of higher fatty acids (C10-C22), and, particularly sodium and potassium tallow and coconut soaps.
• Anionic synthetic non-soap detergents which can be represented by the water-soluble salts of or­ganic sulfuric acid reaction products having in their molecular structure an alkyl radical containing from about 8 to 22 carbon atoms and a radical selected from the group consisting of sulfonic acid and sulfuric acid ester radicals.
• sodium or potassium alkyl sulfates derived from tallow or coco­nut oil: sodium or potassium alkyl benzene sulfonates: sodium alkyl glyceryl ether sulfonates: sodium coconut oil fatty acid monoglyceride sulfonates and sulfates: sodium or potassium salts of sulfuric acid esters of the reaction product of one mole of a higher fatty alcohol and about 1 to 6 moles of ethylene oxide: sodium or potassium alkyl phenol ethylene oxide ether sulfonates, with 1 to 10 units of ethylene oxide per molecule and in which the alkyl radicals contain from 8 to 12 carbon atoms; the reaction product of fatty acids esterified with isethionic acid and neutralized with sodium hydroxide, sodium or potassium salts of fatty acid amide of a methyl tauride; and sodium and potas­sium salts of SO3-sulfonated C10-C24 ⁇ -olefins
• Nonionic synthetic detergents made by the condensation of alkylene oxide groups with an organic hydrophobic compound.
• Typical hydrophobic groups include condensatin products of porpylene oxide with propylene glycol, alkyl phenols, condensation product of propylene oxide and ethylene diamine, aliphatic alcohols having 8 to 22 carbon atoms, and amides of fatty acids.
• nonionic detergents such as amine oxides, phosphine oxides and sulfoxides having semipolar char­acteristics can be removed.
• long chain tertiary amine oxides include dimethyldodecyl­amine oxide and bis-(2-hydroxyethyl) dodecylamine.
• phosphine oxides are found in U.S. Patent No. 3,304,263 which issued February 14, 1967, and include dimethyldodecylphosphine oxide and dimethyl-(2-hydroxydodecyl) phosphine oxide.
• Removable long chain sulfoxides include those corresponding to the formula wherein R1 and R2 are substituted or unsubstituted alkyl radicals, the former containing from about 10 to about 28 carbon atoms, whereas R2 contains from 1 to 3 carbon atoms.
• Specific examples of these sulfoxides include dodecyl methyl sulfoxide and 3-hydroxy tridecyl methyl sulfoxide.
• ampholytic synthetic detergents are sodium 3-dodecylaminopropionate and sodium 3-­dodecylaminopropane sulfonate.
• zwitterionic synthetic detergents include 3-(N,N-dimethyl-N-hexadecylammonio) propane-1-­sulfonate and 3-(N,N-dimethyl-N-hexadecylammonio)-2-­hydroxy propane-1-sulfonate.
• surfactants can be removed by the process of the pres­ent invention: (a) soaps (i.e., alkali salts) of fatty acids, rosin acids, and tall oil; (b) alkyl arene sul­fonates; (c) alkyl sulfates, including surfactants with both branched-chain and straight-chain hydrophobic groups, as well as primary and secondary sulfate groups; (d) sulfates and sulfonates containing an intermediate linkage between the hydrophobic and hydrophilic groups, such as the fatty acylated methyl taurides and the sul­fated fatty monoglycerides: (e) long-chain acid esters of polyethylene glycol, especially the tall oil esters; (f) polyethylene glycol ethers of alkylphenols: (g) polyethylene glycol ethers of long-chain alcohols and mercaptans; (h) fatty acyl diethanol amides
• a particularly useful application of the pres­ent invention is in clearing solutions and container surfaces used in biochemical reactions of surfactants. Since surfactants tend to disrupt the three-dimensional shape of macromolecules, such as proteins, assays which rely on binding interactions between macromolecules and/or enzymes to produce detectable signals are often disrupted by trace amounts of surfactants used to clean reagent containers, whether during routine cleaning of laboratory glassware or during rinse steps of various assay procedures. Sensitivity can therefore be en­hanced by removing surfactants from the surfaces and solutions that contact the biochemical components of such assays.
• surfactants are listed as such by Sigma Chemical Company on pages 310-316 of its 1987 Catalog of Biochemical and Organic Compounds. Such surfactants are divided into four basic types: an­ionic, cationic, zwitterionic, and nonionic.
• anionic detergents include alginic acid, caprylic acid, cholic acid, 1-decanesulfonic acid, deoxycholic acid, 1-dodecanesulfonic acid, N-lauroylsarcosine, and taurocholic acid.
• Cationic detergents include dodecyl­trimethylammonium bromide, benzalkonium chloride, ben­zyldimethylhexadecyl ammonium chloride, cetylpyridinium chloride, methylbenzethonium chloride, and 4-picoline dodecyl sulfate.
• zwitterionic detergents include 3-[(3-cholamidopropyl)-dimethylammonio]-1-pro­panesulfonate (commonly abbreviated CHAPS), 3-[(chol­amidopropyl)-dimethylammonio]-2-hydroxy-1-propanesul­ fonate (generally abbreviated CHAPSO), N-dodecyl-N,N-­dimethyl-3-ammonio-1-propanesulfonate, and lyso- ⁇ -phos­phatidylcholine.
• CHAPS 3-[(3-cholamidopropyl)-dimethylammonio]-1-pro­panesulfonate
• CHAPSO 3-[(chol­amidopropyl)-dimethylammonio]-2-hydroxy-1-propanesul­ fonate
• nonionic detergents in­clude decanoyl-N-methylglucamide, diethylene glycol monopentyl ether, n-dodecyl ⁇ -D-glucopyranoside, ethyl­ene oxide condensates of fatty alcohols (e.g., sold under the trade name Lubrol), polyoxyethylene ethers of fatty acids (particularly C12-C20 fatty acids), poly­oxyethylene sorbitan fatty acid ethers (e.g., sold under the trade name Tween), and sorbitan fatty acid ethers (e.g., sold under the trade name Span).
• Lubrol e.g., sold under the trade name Lubrol
• polyoxyethylene ethers of fatty acids particularly C12-C20 fatty acids
• poly­oxyethylene sorbitan fatty acid ethers e.g., sold under the trade name Tween
• sorbitan fatty acid ethers e.g., sold under the trade name Span
• Cyclodextrins are used to remove the detergent (surfac­tant) from the surface on which or the solution in which the detergent is present. Examples of surfaces are cloth, metal, painted and waxed surfaces, glass, plastic and the like. For example, cyclodextrins can be used in the rinse cycle of automatic clothes washers, dishwashers and labware washers. Cyclodextrins can also be used to remove detergents from building and/or automobile surfaces (such as after washing and prior to painting or waxing).
• LiDS concentration in solution was deter­mined by measuring the activity present in an enzyme acceptor-enzyme donor complementation assay.
• This assay is summarized below and is described in detail in U.S. Patent Application Serial No. , filed April 6, 1987 by Khanna et al . entitled "Reagent Stabilization in Enzyme-Donor Acceptor Assay.”
• This complementation assay is based on the ability of frag­ments of ⁇ -galactosidase to reassemble. The smaller fragment is referred to as the enzyme donor and the larger fragment as the enzyme acceptor. When both fragments are present in solution they reassemble to form an active enzyme.
• This complementation is in­hibited by LiDS. Standard solutions of as little as 0.015% LiDS were shown to completely inhibit the complementation reaction.
• Assay conditions were as follows: 25 ⁇ L of 13 nM ED4-T4 (enzyme donor attached to a T4 ligand) in assay buffer (150 mM potassium phosphate, 100 mM sodium phosphate, 10 mM EGTA (ethylene glycol tetraacetic acid), 2 mM magnesium acetate, 20 mM sodium azide, 0.05% Tween-20, 0.05 mM DTT (dithiothreitol), and 2.4% ethylene glycol, pH 7.0), and 100 ⁇ L of 2.19 mg/ml CPRG (chlorophenol red ⁇ -D-galactopyranoside, a ⁇ -galacto­sidase substrate) in assay buffer were mixed in the lower well of a Baker Encore sample disk.
• assay buffer 150 mM potassium phosphate, 100 mM sodium phosphate, 10 mM EGTA (ethylene glycol tetraacetic acid), 2 mM magnesium acetate, 20
• the upper well contains 25 ⁇ L of 5,000 nM EA (enzyme acceptor) in assay buffer with 100 ⁇ L of either a LiDS standard solution (w/v%) or the liquid component of the BCP/LiDS incubation.
• the reaction was performed on the Baker Encore instrument at 37°C.
• Table 1 shows the enzyme activity after complementation in solutions (as described above) which contained the indicated concentrations of LiDS. These data show the effects of surfactant on enzyme complementation.
• a concentration of 0.005% LiDS produced a com­plementation activity only about 60% that of a standard solution not containing any LiDS.
• the corresponding complementation activity was only about 10% of the normal activity.
• a ⁇ -­cyclodextrin polymer is capable of absorbing and se­questering a detergent, such as LiDS, from an aqueous solution.
• a detergent such as LiDS
• Potentially inhibitory concentrations of LiDS were incubated with the ⁇ -cyclodextrin polymer and assayed in a sensitive complementation assay. Comple­mentation was not affected at any of the ratios of LiDS to BCP tested, thereby indicating that the BCP was pre­venting LiDS from affecting the complementation reac­tion. Controls indicated that soluble ⁇ -cyclodextrins were not released from the polymer, thereby eliminating this possibility as a cause of the indicated result.

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