Abstract: An apparatus and method by which tracer compounds and combustion products in the exhaust of an internal combustion engine are more completely combusted, so that oil consumption of the engine can be more precisely and concurrently measured on a real-time basis using tunable diode laser spectroscopy. The apparatus includes a furnace capable of completely burning nonradioactive stable organobromo compounds and combustion products within the exhaust gas of the engine, without being reactive with the compounds or the resulting tracer gas or isotopic specie of the compounds. The furnace generally has at least one passage through which the exhaust gas passes. The wall surfaces of the passage are formed of a material with a high concentration of titanium, such that the exhaust gas is substantially limited to contact with the high-Ti material while within the furnace.

Abstract: This invention provides a method for invisibly tagging, for subsequent identification purposes, various liquid petroleum hydrocarbons, such as crude oil, diesel fuel, heating oil, kerosene, lubricating oils, waxes, jet fuel, and in particular gasoline, remarkably using visible dyes by incorporating therein one or more visible dyes at minute levels such that they cannot be visually detected by the human eye. Visible dyes which have high solubility in petroleum hydrocarbons and maximum absorption in the 550-700 nm visible wavelength range are used to impart such invisible markings. The visible dyes, although employed at non-visible levels, are still capable of detection in a relatively quick and simple manner which requires minimal instrumentation, creates no waste products for disposal, and gives true quantitative results of dye concentrations in the field.

Abstract: A synthesis member preferably comprises two elements: a crown and a stem. The stem includes a tag, such as a transponder, that is used to identify the synthesis member and/or the synthetic history of the synthesis member when used in the automated synthesis of compound libraries containing large numbers (e.g. 1000 or more) compounds. The crown provides the location at which compounds are synthesized. The combination of a crown for use with compound synthesis and stem allows the tracking of individual synthesis members from a library containing thousands of such synthesis members. Because each synthesis member is individually tracked and can be logged into a database and/or process flow control system, the synthesis of several thousand individual compounds in conventional containers, such as round bottom flasks is made possible using only traditional compound synthesis approaches.

Abstract: Polymers having amine-thiol terminal moieties are provided. The amine-thiol terminal moieties are imparted by using amine-thiols as chain transfer agents in aqueous addition polymerizations. The polymers are useful as mineral dispersants, as water-treatment additives for boiler waters, cooling towers, reverse osmosis applications, sugar refining, paper production, geothermal processes and oil wells, and as detergent additives acting as builders, anti-filming agents, dispersants, sequestering agents and encrustation inhibitors.

Abstract: Tartrate-resistant acid phosphatase (TRAP) has been used as a marker for bone resorption. However, there are two forms of said enzyme in the body: TRAP 5a and TRAP 5b, of which TRAP 5b is a much more specific marker. The present invention is directed to an immunoassay for measuring the bone resorption rate, which methods enables the specific determination of TRAP 5b, whereby the amount of TRAP 5b reflects the bone resorption rate. The method is useful in diagnosing disorders associated with a change in the bone resorption rate, such as osteoporosis. Methods of screening for susceptibility to such disorders, and method of monitoring the effect of treatment are also provided. Further a test-kit useful in said methods is provided.

Abstract: Formed constituents of a quiescent anticoagulated whole blood sample are optically or visually analyzed in a sample chamber which has a varying through plane thickness due to convergent opposing sample chamber walls. At least one of the convergent walls of the chamber is transparent so that the blood sample constituents can be observed. The chamber's varying thickness produces a first lesser thickness region in the chamber wherein a quiescent monolayer of red blood cells in the sample will reside after the sample is introduced into and fills the chamber. Larger formed constituents such as white blood cells in the sample are unable to enter the aforesaid lesser thickness region of the chamber. The red cells which reside in the greater thickness regions will agglomerate to form rouleaux and lacunea. The exact thickness of the chamber at any particular location in the chamber can be predetermined, or can be determined in situ as the sample is being analyzed.

Abstract: A method for detecting an analyte of interest present in a mixture at an ultralow concentration includes selecting a radioactive derivatizing agent comprising a multiphoton-emitting radioisotope moiety and a moiety reactive with the analyte of interest, the radioisotope moeity being bound to the derivatizing agent by a bond that is stable under the conditions employed in the other steps of the method, derivatizing the analyte of interest with the derivatizing agent, separating the analyte of interest from other components of the mixture by chromatography, and detecting the analyte of interest using multiphoton detection. The derivatizing step may be performed before or after fractionation. A radiophore for multiphoton emission enhanced chromatography has a first moeity bound to a multiphoton-emitting radioisotope, and a second moiety that is reactive with a functional group of an analyte of interest.

Abstract: The present invention is directed to tracer-containing chemical compositions and to the use of at least one perfluorocarbon tracer in such compositions to provide a means of identifying and quantitatively analyzing such compositions.

Abstract: A breath test for determining the rate of metabolism of a drug is described. First, a safe and effective amount of the drug, preferably appropriately labelled and most preferably isotopically-labelled, is administered to a subject. After a suitable time period, the exhaled breath of the subject is analyzed to determine the concentration of a metabolite. The concentration of the metabolite is then used to determine the rate of metabolism of the drug. A breath test kit is also described. Such a breath test kit would include an item or items necessary for performing at least one of the methods of determining the rate of metabolism of a drug in a subject. For example, such a breath test kit could include an isotopically-labelled drug to be administered to the subject.

Abstract: A method of determining the concentration of a sample antigen in the presence of an interferant by (1) running two immunoassays on the sample: one assay where the interferant influences the binding of both the sample antigen and a labeled antigen and a second assay where the interferant influences the binding of the sample antigen but not the labeled antigen; (2) obtaining a plot of the possible sample antigen concentrations versus the possible interferant concentrations corresponding to the readout for the sample for each of the two immunoassays; and (3) determining the sample antigen concentration and the interferant concentration which correspond to the point that appears on both of the immunoassay plots.

Abstract: An arrangement for the investigation of hydrophilic macromolecules (1) in an aqueous solution having a solid carrier surface (5) onto which a lipid film (24) is disposed, wherein the molecules (1) to be investigated are bound, by means of a molecular coupling system (20), to the lipid film (24) and thus are immobilized, is characterized in that the molecular coupling system (20) comprises at least two, preferably three molecular or nuclear components (21, 22, 23), which can be coupled to each other, of which a first component (21) is bound to the lipid film (24) and a second component (22) is bound to a hydrophilic macromolecule (1) to be investigated. In this way, it is rendered possible to immobilize and investigate any hydrophilic macromolecules, wherein the coating of the solid carrier surface should be able to be carried out in an as easy as possible and reversible manner.

Abstract: A modified surfactant of the PLURONIC.TM.-type compound and method for manufacture is disclosed. The surfactant compound has at least one PEO block attached at a first end to at least one PPO block, with at least one of the PEO block having an organic metal-chelating end group (R) attached to a second end, the remaining PEO blocks having an unmodified hydroxyl group at the second end. The metal-chelating group is charged with an metal-ion. A protein with a metal-affinity tag, e.g., a histidine tag, is then complexed with the metal-chelating group to form a complex of the modified surfactant, the metal ion, and the protein. The modified surfactant may be adsorbed upon a hydrophobic surface, charged with a metal ion, and then complexed with a protein with a metal-affinity tag. A surface with specific activity toward proteins is the presented, which is suitable for applications where a protein is immobilized upon a surface to give the surface specific protein activity.

Abstract: A method for determining cleaning action on medical instruments and other objects is disclose. The method uses a predetermined soiling substance, for example fresh blood mixed with a radioactive marker. The soiling substance is applied to the instrument as a predetermined contamination. By making various radiation and time measurements one can determine in absolute mass units either the remaining soiling after the completion of a cleaning process or the soiling prior to the cleaning process. By comparing the determined masses one may validate specific cleaning processes, machines or agents.

Abstract: A method of monitoring a therapeutic regimen in an animal, the method involving a) providing to the animal a therapeutic compound and a detectable compound that passes into the bloodstream, excretory system, or other tissue or body fluid in detectable form; b) after a period of time, following step (a), sufficient for passage of a detectable amount of the detectable compound into the body fluid or tissue, collecting a sample of the fluid or tissue from the animal; and c) measuring or detecting the detectable compound, or a detectable metabolite thereof, in the sample, wherein the detectable compound involves one member of a specific binding pair, and detection is carried out using the second member of the specific binding pair.

Abstract: A method for measuring the quantity of a polymeric or pre-polymeric composition within a given volume that includes combining the polymeric or pre-polymeric composition with a plurality of microparticles having a non-ferromagnetic or non-ferrimagnetic core provided with a coating that is ferromagnetic, ferrimagnetic, or conductive, to form an admixture in which the microparticles are substantially uniformly dispersed throughout the composition. The microparticles have a detectable electromagnetic characteristic which correlates with the amount of the composition within a given volume. The electromagnetic characteristic of the microparticles is then measured to determine the quantity of the composition within a given volume.

Abstract: A method of tagging and detecting objects is disclosed which comprises the steps of: (a) applying a volatile taggant to the object; and (b) subsequently detecting the presence of the taggant by the absorption, transmittance, reflectance, photon emission or fluorescence of the taggant and therefore a proximity of the tagged object. The present invention therefore provides optical sensing means which do not require physical separation of differing compounds for discrimination thereof.

Abstract: Liquids, such as petroleum fuels, are tagged with chemical compounds having a light-absorbing identifying chemical moiety and at least one polymerizable chemical moiety. The marker is identified in a specimen of the liquid by polymerizing the marker compound, generally along with additional co-polymerizable material.

Abstract: A method for measuring the level of stress in a polymeric or pre-polymeric composition within a given volume that includes combining the polymeric or pre-polymeric composition with a plurality of microparticles having a non-ferromagnetic or non-ferrimagnetic core provided with a coating that is ferromagnetic or ferrimagnetic to form an admixture in which the microparticles are substantially uniformly dispersed throughout the composition. The microparticles have a detectable magnetic characteristic which correlates with level of stress in the composition within a given volume. The change in the magnetic characteristic of the microparticles is then measured to determine the level of stress in the composition within a given volume.

Abstract: Use of compounds from the class of the phthalocyanines, naphthalocyanines, nickel dithiolene complexes, aminium compounds of aromatic amines, methine dyes or azulenesquaric acid dyes which have their absorption maximum in the range from 600 to 1,200 nm and/or a fluorescence maximum in the range from 620 to 1,200 nm, as markers for liquids, a process for detecting markers in liquids, and a detector suitable for this purpose.

Abstract: A liquid hydrocarbon fuel composition comprises at least one tagging agent and a mixture of hydrocarbon components having boiling points in the range of about 100 degrees F. to about 800 degrees F. The tagging agent is present at a concentration in the range of from about 0.5 ppb to about 500 ppb. The tagging agent is elutable by chromatographic analysis of the liquid hydrocarbon fuel composition apart from the hydrocarbon components of the fuel composition. The tagging agent is formed from an organic compound containing elements found at natural isotopic abundance. Preferably, two or more tagging agents are employed in the fuel so that each fuel composition can be assigned a unique tagging agent composition. Analysis techniques are also disclosed.

Abstract: A breath test for determining the rate of metabolism of a drug is described. First, a safe and effective amount of the drug, preferably appropriately labelled and most preferably isotopically-labelled, is administered to a subject. After a suitable time period, the exhaled breath of the subject is analyzed to determine the concentration of a metabolite. The concentration of the metabolite is then used to determine the rate of metabolism of the drug. A breath test kit is also described. Such a breath test kit would include an item or items necessary for performing at least one of the methods of determining the rate of metabolism of a drug in a subject. For example, such a breath test kit could include an isotopically-labelled drug to be administered to the subject.

Abstract: Markers which are soluble in petroleum fuel and are extractable from petroleum fuel by either acidic aqueous solutions or basic solutions and develop a color in the presence of the extracting acidic or basic aqueous solution, are identified by passing a specimen putatively containing the marker through an acidic resin column or a basic resin column, as the case may be.

Abstract: Methods for marking a liquid and methods and systems for identifying marked liquids. A liquid can be marked for identification purposes with at least a first marker and a second marker. Each of the markers is miscible with the liquid. The markers are mixed in the liquid so that the ratio of the concentration of the first marker to the concentration of the second marker is substantially equal to a predetermined value. Thus, when a system according to the invention measures the concentrations of the first and second markers, the system can compare the ratio of the measured concentration of the first marker to the measured concentration of the second marker with a look up table of the predetermined values to provide information concerning the identity of the liquid. In a preferred embodiment, the concentration of the markers is measured using an absorption spectrometer.

Abstract: A polymer tagged with luminol is provided which enables the fluorescent or chemiluminescent detection of the tagged polymer at low concentrations. The chromophore may be covalently bonded to the polymer backbone without sacrificing the chromophore's fluorescent or chemiluminescent properties. The present invention has been found useful in the treatment and monitoring of industrial waters.

Abstract: A method for assay of an analyte by use of a material labeled with a chemiluminescent substance, which comprises adding a quencher and/or decreasing the specific activity of a chemiluminescent substance labeled probe, thereby decreasing the quantity of chemiluminescence.

Abstract: Methods and compositions for determining the amount of chemical cross talk r isotopic scrambling, induced by an analytical procedure on a test sample using a reference standard composition containing a predetermined ratio of isotopes is disclosed. The method includes subjecting a reference sample which comprises a predetermined ratio of labeled isotopes to an analytical procedure; determining the degree of isotopic scrambling in the reference sample, subjecting a test sample to the identical analytical procedure; the degree of isotopic scrambling caused by the analytical procedure to the reference sample provides an indication of the presence of chemical cross-talk caused by the analytical procedure on the test sample. In preferred aspects, the cross talk is determined using mass spectral analysis and the reference sample comprises an algae mixture having a predetermined ratio of carbon-12 to carbon-13 isotopes.

Abstract: Method for tagging hydrocarbons and for detecting the presence of tagged hydrocarbons in a hydrocarbon mixture. The method can be utilized to tag gasoline, diesel fuel, heating oil, lubricating oil or crude petroleum. The hydrocarbon to be tagged is blended with a relatively small amount of a fluorescent dye. The presence of the tagged hydrocarbon is subsequently determined by exciting the dye to fluoresce at wavelengths in the higher portion of the visible spectral region or the lower portion of the near infrared spectral region.

Abstract: A porous material (10) is contaminated with soil (14). Optionally, the porous material is partially shielded by an impermeable layer. The contaminated porous material is packaged and shipped to a user site. The contaminated porous material is removed from the package and placed in an automated processor containing medical equipment (22). The medical equipment and porous material are subjected to a cleaning, disinfecting, or sterilizing cycle in the processor. The cleaning process is evaluated by examining the porous material with an infrared or other electronic reader (24) to determine the presence of remaining soil which has not be removed during the cleaning, disinfecting, or sterilizing cycle.

Abstract: A method for determining wafer cleanliness by fluorometric monitoring of the impurities in the semiconductor chip wafer rinse solution. A clean chip is indicated by a leveling off of increased concentration of impurities as the rinsing of the chip progresses. A method for optimizing reuse or recyling of the water discharged from the rinse process which accurately measures the contaminants in that water.

Abstract: A method for the quantitative determination of dissolved oxygen in a liquid fuel includes the steps of doping a sample of the fuel with a preselected concentration of a probe material including a luminophor which exhibits luminescence of wavelength which is quenched by oxygen dissolved in the fuel, illuminating the fuel with light from a coherent light source, such as a laser, of a wavelength which induces the luminescence in the luminophor, and thereafter measuring the change with time of the luminescence from the luminophor in the fuel and determing from the change with time of the luminescence the concentration of oxygen in the fuel.

Abstract: The present invention relates to a method of diagnosing diabetes, which comprises administering a diagnostic agent comprising glucose labeled with .sup.13 C at a specific position, or pyruvic acid labeled with .sup.13 C in at least one specific position. According to the present invention, there is provided a method of diagnosing diabetes by administering a diagnostic agent which can be used safely without side effects to give accurate results immediately with less physical pains on the subject. The present method of diagnosing diabetes can distinguish between healthy persons and patients with diabetes even under the circumstances where the patients are easily missed, and further it can determine the type of diabetes (insulin-dependent type or insulin-independent type).

Abstract: The present invention relates to a method and apparatus for quantitative determination of the level of spalling of a protective surface coating as a result of repetitive heating and cooling. The method comprises introducing at least one radionuclide into the protective coating of an article, alternately heating and cooling the article for a predetermined number of heating and cooling cycles, collecting the spalled particles and measuring the radioactivity thereof. The apparatus comprises a chamber for receiving the coated article, means for heating the chamber or the article and a spall collector. The spall collector is characterized in having means for immobilizing any spalled coating particles and in being so adapted that the level of radioactivity of any spalled particles can be measured by a .gamma.-spectrometer.

Abstract: Methods and apparatus are disclosed for determining the presence of a catabolic state in an organism (or collection of organisms) by measuring changes in isotopic ratios in biological materials obtained from them. Preferably, .sup.13 C/.sup.12 C ratios are monitored for isotopically unenriched animals, such as by testing changes in the ratio in blood or breath.

Abstract: A method for detecting the presence of a target nucleic acid species having first, second and third target sequences. In the present invention, a solution to be tested is brought into contact with a solid support having a probe nucleic acid species attached thereto, the probe nucleic acid sequence comprising a sequence that is complementary to the first target sequence. A dye solution is then brought into contact with the solid support. The dye solution includes a first dye attachment nucleic acid sequence coupled to a first dye and a second dye attachment nucleic acid sequence coupled to a second dye. The first dye attachment nucleic acid sequence is complementary to the second target sequence and the second dye attachment nucleic acid sequence is complementary to the third target sequence.

Abstract: A water-immiscible organic fluid is tagged and identified by tagging the organic fluid with between about 0.25 and about 100 ppm of a marker compound having the formula: ##STR1## where the OH groups are either ortho or para to the diazo moieties, and the Xs are the same or different and are selected from C.sub.1 -C.sub.12 -alkyl, Cl, Br, F, NH.sub.2, CN, NO.sub.2, NH(C.sub.1-3 -alkyl) and N(C.sub.1-3 -alkyl).sub.2, and the fluid is identified by extracting the tagged fluid with an alkaline aqueous extractant having a pH above about 12 and containing, based on 100 parts by weight of said extractant, between about 10 and about 60 parts by weight of an organic cosolvent having the formula:R.sup.1 --O--R.sup.2 --NH.sub.2 (II)where R.sup.1 is C.sub.1 -C.sub.3 -alkyl, and R.sup.2 is C.sub.2 -C.sub.6 -alkylene.

Abstract: A water-immiscible marker is dissolved in polyethylene glycol or other suitable carrier, and the marker so dissolved is added to a waterborne composition which is used as an additive to a waterborne or water processable composition. Subsequently, the marker is either extracted with a non-polar solvent or detected by means of a surface spot test. From the non-polar solvent, the marker is extracted with an acidic aqueous solution or an alkaline aqueous solution, depending upon the marker, and color-developed. Likewise, a surface spot test can detect the presence of the marker by, if necessary, first softening the marked surface to be tested either chemically or by thermal means, and developing a color with a color-developing reagent placed on the exposed surface. Applications can include the marking of paint, coatings, wax emulsions and water soluble/dispersable additives commonly used in water based applications, e.g., cement additives.

Abstract: A chemical metering and control system is provided which maintains a desired level of a pesticide (or other chemical) in any open or closed channel flow stream with fluctuating flow rates. The system dispenses an amount of the pesticide at an injection point of the flow stream along with a fluorescent indicating dye, and then takes a sample downstream from the injection point to determine how much of the indicating dye is present in the flow stream, and therefore how much pesticide is present. At the sampling point a pump extracts a flow stream sample and passes the sample to a fluorometer which measures the amount of fluorescent indicating dye injected upstream. A proportional integral derivative (PID) controller then adjusts the level of the pesticide/dye mixture in order to achieve the appropriate concentration of pesticide in the flow stream.

Abstract: The invention provides methods for purifying or manipulating bone marrow and blood cells based upon P-glycoprotein expression. The methods rely upon immunopurification procedures or upon differential accumulation of materials subject to P-glycoprotein mediated efflux.

Abstract: A method is disclosed for identifying the source of a transported chemical shipment. The method employs either a chemical element or an organic compound with one or more atoms that are non-radioactive isotopes generally not found in nature. A small quantity of the isotopic compound is introduced into the storage vessel containing the chemical to be transported prior to shipment of the chemical. Upon arrival at its destination point, a sample of the chemical shipment is analyzed. Matching the isotopic compound found in the chemical with the isotopic compound introduced into the storage vessel prior to shipment is indicative that the shipped chemical is identical to the chemical received. Non-radioactive materials may further be employed for detecting the source of a newly introduced contaminant in a water supply. The chemical substance may be a non-radioactive isotope of the chemical shipment being transported.

Abstract: A method for allowing authentification of a bulk liquid e.g. petrol or another mineral oil based product, comprises introducing into the liquid a small amount of a chemiluminescent substance. Samples for authentification are subjected to the conditions required to trigger the chemiluminescent reaction and monitored for chemiluminescent emission.

Abstract: A method for diagnosing premenstrual syndrome in a female human comprising the step of measuring the ratio of esterified L-carnitine to free L-carnitine in a patient's serun or plasma. Women who have an esterified to free L-carnitine ratio of greater than about 0.22 are diagnosed as having premenstrual syndrome.

Abstract: Rare elements, which can be selected from Ni, Cu, W, Li, N, Ce, Sn, Y, Nd, Nb, Co, La, Pb, Ga, Mo, Th, Cs, Ge, Sm, Gd, Be, Pr, Se, As, Hf, Dy, U, B, Yb, Er, Ta, Br, Ho, Eu, Sb, Tb, Lu, Tl, Hg, I, Bi, Tm, Cd, Ag, In, Se, Pd, Pt Au, He, Te, Rh, Re, Ir, Os, and Ru can be used to tag commodities, including explosive materials, with a unique tagging agent.

Abstract: A method for tagging hydrocarbons and for detecting the presence of tagged hydrocarbons in a hydrocarbon mixture. The method can be utilized to tag gasoline, diesel fuel, heating oil, lubricating oil or crude petroleum. The hydrocarbon to be tagged is blended with a relatively small amount of a fluorescent dye. The presence of the tagged hydrocarbon is subsequently determined by exciting the dye to fluoresce at wavelengths in the higher portion of the visible spectral region or the lower portion of the rear infrared spectral region.

Abstract: A process for the preparation of organic and inorganic deuterium-tagged compounds is disclosed. The process comprises heating a deuterium oxide-solution of an organic or inorganic compound, the solution having a pH of from about 10 to about 1 to a temperature and pressure so that a supercritical reaction mass forms and one or more deuterium atoms of the deuterium oxide solvent exchanges with one or more protons of the organic or inorganic compound. After cooling the reaction solution formed from the supercritical reaction, the organic or inorganic deuterium-tagged compound is separated.

Abstract: Additives are proposed for compositions comprising radiolabelled organic compounds e.g. 32P-labelled nucleotides. Stabilisers are selected from tryptophan, para-aminobenzoate, indoleacetate and the azole group. Dyes are selected from Sulphorhodamine B, Xylene Cyanol, Azocarmine B and New Coccine. Preferred compositions contain both stabiliser and dye.

Abstract: Use of compounds from the class of the phthalocyanines, naphthalocyanines, nickel dithiolene complexes, aminium compounds of aromatic amines, methine dyes or azulenesquaric acid dyes which have their absorption maximum in the range from 600 to 1,200 nm and/or a fluorescence maximum in the range from 620 to 1,200 nm, as markers for liquids, a process for detecting markers in liquids, and a detector suitable for this purpose.

Abstract: A novel method for monitoring the success or the yield of chemical reactions involving a reactant bound to a solid phase support, or to forecast the success of such reactions, or to quantify the number of deuterium containing groups present in a solid-phase bound sample, using infrared spectroscopy and deuterium-carbon absorbances, along with novel compounds and intermediates useful for carring out the method.

Abstract: The isotopic composition of a multiatomic isotope-bearing species such as CO.sub.2 in an analyte is measured by maintaining the analyte in a condition such that isotope-bearing species are present in an excited state and directing light at wavelengths corresponding to transition energies of isotope-bearing species with different isotopes. The interaction between the analyte and light at the different wavelengths is monitored, as by monitoring the optogalvanic effect caused by the light of the different wavelengths. The light may be supplied by a laser including the isotope-bearing species. A stable isotope such as .sup.13 C or .sup.18 O can be used as a tracer in a chemical or biological test and detected using the composition-determining method.

Abstract: An integral multi-layer analytical element for analyzing bile acid sulfate comprising a support member, a reagent layer on said support member and a porous developing layer on said reagent layer, at least one of the reagent layer and developing layer containing bile acid sulfate sulfatase, 3.beta.-hydroxysteroid dehydrogenase and a combination of thio-NAD.sup.+ and reduced NAD or reduced NADP, in which the reagent layer contains a water-soluble polymer, a buffer and at least one component selected from the group consisting of sugar alcohols and Mn.sup.2+, which element suppresses the increase of blank values and prevents agglomeration of the enzyme during the preparation of a solution for forming the reagent layer.

Abstract: A system for tagging products or substances for retrospective identification using controlled abundance ratios of multiple isotopes in each of one or more elements in the tagged substance. The abundance ratios of the isotopes of the tagging elements are measured by suitable means to determine the identification code of the tagged product of substance.