Abstract: An aqueous wash solution is buffered to a pH of from about 5 to about 9 and contains at least about 1.5 weight percent of a compound comprising a lower alcohol sulfate anion having from 6 to 10 carbon atoms and an alkali metal or ammonium cation, such as sodium decyl sulfate. This wash solution is useful in a method for the determination of an immunological ligand, and is not prone to crystallization at lower temperatures. Particularly, it is useful for washing the immunological complex formed between the ligand and a receptor molecule therefor. Unreacted materials can be readily separated from the complex by the washing, particularly if the separation is carried out using a filtration membrane in a test device. A test kit for ligand determination comprises the wash solution as well as one or more receptors for the ligand, at least one of which is labeled for detection. This kit is particularly useful for measuring human chorionic gonadotropin (hCG) as an early indicator of pregnancy.

Abstract: Diluent and wash compositions are useful in a rapid and sensitive assay for detecting antibodies, and especially retroviral antibodies, in a biological specimen. The diluent composition is buffered to a pH of 6 to 10 and includes a protein or carbohydrate, a surfactant and a negatively-charged organic compound. The wash composition is buffered to a pH of 5 to 10 and includes a surfactant. These compositions can be included in a diagnostic kit. The method of this invention includes mixing the biological specimen with the diluent composition, forming an immunological complex between ligand and antibodies in the specimen and separating complexed materials from uncomplexed materials using a filtration membrane and a washing step. An enzyme labeled anti-antibody is added to form a ligand-antibody-antibody complex followed by its detection using suitable reagents.

Abstract: A test kit useful for the determination of an immunological ligand includes a labeled receptor for that ligand, a specific wash solution and a test device. The wash solution is buffered to a pH of from about 5 to about 9 and contains at least 0.01 weight percent of a compound having a dodecyl sulfate anion and an alkali metal or ammonium cation. One such compound is sodium dodecyl sulfate. The test device has several test wells, and in each well there is a microporous membrane. A receptor for the ligand of interest is immobilized in one test well. The kit is particularly useful for measuring human chorionic gonadotropin as an early indicator of pregnancy.

Abstract: Diluent and wash compositions are useful in a rapid and sensitive assay for detecting antibodies, and especially retroviral antibodies, in a biological specimen. The diluent composition is buffered to a pH of 6 to 10 and includes a protein or carbohydrate, a surfactant and a negatively-charged organic compound. The wash composition is buffered to a pH of 5 to 10 and includes a surfactant. These compositions can be included in a diagnostic kit. The method of this invention includes mixing the biological specimen with the diluent composition, forming an immunological complex between ligand and antibodies in the specimen and separating complexed materials from uncomplexed materials using a filtration membrane and a washing step. An enzyme labeled anti-antibody is added to form a ligand-antibody-antibody complex followed by its detection using suitable reagents.

Abstract: An aqueous wash solution is buffered to a pH of from about 5 to about 9 and contains at least about 0.01 weight percent of a compound comprising a dodecyl sulfate anion and an alkali metal or ammonium cation, such as sodium dodecyl sulfate. This wash solution is particularly useful in a method for the determination of an immunological ligand. Particularly, it is useful for washing the immunological complex formed between the ligand and a receptor molecule therefor. Unreacted materials can be readily separated from the complex by the washing, particularly if the separation is carried out using a filtration membrane in a test device. a test kit for ligand determination comprises the wash solution as well as one or more receptors for the ligand, at least one of which is labeled for detection. This kit is particularly useful for measuring human chorionic gonadotropin (hCG) as an early indicator of pregnancy.

Abstract: An immunoassay test device is disclosed with dried reagent drops applied to a sloping side wall of a reaction wall. A method of applying them as liquid drops is also described, wherein the slope of the side wall, and the composition and volume of the liquid drop are selected to insure that the liquid drops do not flow down to the bottom of the well.

Abstract: An aqueous wash solution is buffered to a pH of from about 5 to about 9 and contains at least about 1.5 weight percent of a compound comprising a lower alcohol sulfate anion having from 6 to 10 carbon atoms and an alkali metal or ammonium cation, such as sodium decyl sulfate. This wash solution is useful in a method for the determination of an immunological ligand, and is not prone to crystallization at lower temperatures. Particularly, it is useful for washing the immunological complex formed between the ligand and a receptor molecule therefor. Unreacted materials can be readily separated from the complex by the washing, particularly if the separation is carried out using a filtration membrane in a test device. A test kit for ligand determination comprises the wash solution as well as one or more receptors for the ligand, at least one of which is labeled for detection. This kit is particularly useful for measuring human chorionic gonadotropin (hCG) as an early indicator of pregnancy.

Abstract: A device useful for the determination of a ligand in an aqueous liquid comprises a water-insoluble substrate. Immobilized in at least one location on that substrate is a biotinylated receptor for the ligand. This receptor is in dried form and immobilized with one or more dried water-soluble acrylamide homo- or copolymer binder materials. When the immobilized receptor is contacted with an aqueous sample, the binder material is dissolved and the receptor is released for reaction with the ligand. The resulting reaction product is determined in a suitable manner. The device can be included in a kit having other components useful for ligand determination. The device and method of its use are particularly useful for the determination of human chorionic gonadotropin (hCG) as an early indicator of pregnancy.

Abstract: A multilayer analytical element exhibits improved precision in the assay of total lactate dehydrogenase (LDH). The element also provides reduced susceptibility to total protein and hemoglobin interferences in the assay. The element contains a porous spreading layer composed of a particulate structure. A fluorinated surfactant is also used in the assay. This surfactant has one or more fluorocarbon moieties provided, that when the surfactant has more than one such moiety, they are substantially linear. The surfactant can be incorporated in the element or added at the time of the assay.

Abstract: An analytical element is used to determine magnesium ions at a pH of from about 8.5 to about 11. This element comprises an absorbent carrier material containing a 1,5-bis(2-hydroxyphenyl)-3-cyanoformazan compound which is substituted in at least one of the 3-, 4- and 5-positions of either phenyl moiety. The substituents are chosen such that their cumulative Hammett-sigma value is greater than about 0.23, provided that none of the substituents is carboxy. The assay is carried out in the presence of a calcium ion chelating agent and a suitable buffer. In preferred embodiments, the cyanoformazan is incorporated in the element in such a manner so as to be isolated from protein molecules which may be encountered in the assay.

Abstract: An element for the analysis of liquids contains a radiation-transmissive, detectable species migration-inhibiting layer interposed between a porous radiation-blocking layer and a radiation-transmissive reagent layer. All three layers are permeable to a predetermined analyte. The reagent layer contains a composition that provides a detectable species such as a dye in proportion to the concentration of the analyte that diffuses into the reagent layer from the overlying porous radiation-blocking layer. The detectable species migration-inhibiting layer acts to reduce the migration of, for example, dye from the reagent layer into the porous radiation-blocking layer, where the optical density of the dye cannot easily be measured. Optionally, the above-described three layers can be carried on a radiation-transmissive support, and other layers such as spreading layers, registration layers, and subbing layers can also be present in the element.