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Etymology[ edit ] According to Etymology Online,  the verb assay, at least since the 13th century, meant "to try, endeavor, strive; test the quality of", from Anglo-French assaier, from assai n.
For assay of currency coinsthis literally meant analysis of the purity of the gold or silver or whatever precious component was used to represent the true value of the coin. This might have translated later possibly after the 14th century into a generalized meaning of analysis,[ citation needed ] e.
General steps[ edit ] An assay analysis is never an isolated process and must be combined with pre- and post-analytic procedures.
The information communication e. Like any multi-step information handling and transmission systems, variation and errors in the communicated final results of an assay involve corresponding parts in every such step; i. Since the assay itself the analytic step gets much attention,  steps that get less attention by the chain of users, i.
It might involve a simple centrifugal separation or washing or filtration or capture by some form of selective binding or it may even involve modifying the target e.
Generally there are multiple separate steps done before an assay and are called preanalytic processing. But some of the manipulations may be inseparable part of the assay itself and will not thus be considered pre-analytic.
The presence and quantity of that analyte is converted into a detectable signal generally involving some method of signal amplification, so that it can be easily discriminated from noise and measured - e.
Sometimes the concentration of the analyte is too large and in that case the assay may involve sample dilution or some sort of signal diminution system which is a negative amplification.
A system of deciphering the amplified signal into an interpretable output that can be quantitative or qualitative.
It can be visual or manual very crude methods or can be very sophisticated electronic digital or analog detectors. Signal enhancement and noise filtering may be done at any or all of the steps above. These may simply be in the form of a narrow band-pass optical filer, or a blocking reagent in a binding reaction that prevents nonspecific binding or a quenching reagent in a fluorescence detection system that prevents "autofluorescence" of background objects.
An end point assay, in which a single measurement is performed after a fixed incubation period; or A kinetic assay, in which measurements are performed multiple times over a fixed time interval.
Kinetic assay results may be visualized numerically for example, as a slope parameter representing the rate of signal change over timeor graphically for example, as a plot of the signal measured at each time point.
For kinetic assays, both the magnitude and shape of the measured response over time provide important information.
Usual assays are simple or single target assays which is usually the default unless it is called multiplex. Multiplex assays are used to simultaneously measure the presence, concentration, activity, or quality of multiple analytes in a single test.
Generally they have a few more gradations than just two outcomes, positive or negative, e. An example of such an assay used in coagulation testing laboratories for the commonest inherited bleeding disease - Von Willebrand disease is VWF antigen assay where the amount of VWF present in a blood sample is measured by an immunoassay.
The functional counterpart of the VWF antigen assay is Ristocetin Cofactor assay, which measures the functional activity of the VWF present in a patients plasma by adding exogenous formalin-fixed platelets and gradually increasing quantities of drug named ristocetin while measuring agglutination of the fixed platelets.
Sample type and method[ edit ] Depending on the general substrate on which the assay principle is applied: Examples include in vivo, whole organism e. Immunoassay when the response is an antigen antibody binding type reaction.
Signal amplification[ edit ] Depending on the nature of the signal amplification system assays may be of numerous types, to name a few: Light detection systems that may use amplification e.
Radioisotope labeled substrates as used in radioimmunoassays and equilibrium dialysis assays and can be detected by the amplification in Gamma counters or X-ray platesor phosphorimager Polymerase Chain Reaction Assays that amplify a DNA or RNA target rather than the signal Combination Methods Assays may utilize a combination of the above and other amplification methods to improve sensitivity.
Enzyme-linked immunoassay or EIA, enzyme linked immunosorbent assay. Detection method or technology[ edit ] Depending on the nature of the Detection system assays can be based on: Colony forming or virtual colony count: If the emitted light is of a specific visible wavelength it may be called colorimetryor it may involve specific wavelength of light e.
Transmittance of light may be used to measure e. Turbidimetry when the opacity of straight-transmitted light passing through a liquid sample are measured by detectors placed straight across the light source. When the size statistics of cells is assessed by an image processor.
Other physical property based assays may use.Services What we offer. Bureau Veritas Minerals (BVM) is a service company that provides mineral preparation and laboratory testing services for mining, minerals exploration and research. Improved data management and analysis expected from MGB Friday, 31 August The Mines and Geosciences Bureau (MGB) continues to enhance the competence of its personnel in the management and analysis of data related to the environment and natural resources.
Read more: Improved data management and analysis expected from MGB. ABOUT US Gauteng Refinery is part of a group of companies which has been active for over 30 years in precious metals beneficiation throughout Africa. It is in the business of recovering and refining gold and silver, and the platinum group metals: platinum, palladium, rhodium, ruthenium, iridium and osmium.
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