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  2. Matrix (chemical analysis) - Wikipedia

    en.wikipedia.org/wiki/Matrix_(chemical_analysis)

    This is especially important for solid samples where there is a strong matrix influence. [5] In cases with complex or unknown matrices, the standard addition method can be used. [ 3 ] In this technique, the response of the sample is measured and recorded, for example, using an electrode selective for the analyte.

  3. Standard addition - Wikipedia

    en.wikipedia.org/wiki/Standard_addition

    This method, however, assumes the pure aqueous solution of silver and a photographic waste sample have the same matrix and therefore the waste samples are free of matrix effect. Spreadsheet for standard addition example on determining the silver concentration of photographic film waste.

  4. Matrix-free methods - Wikipedia

    en.wikipedia.org/wiki/Matrix-free_methods

    Matrix-free conjugate gradient method has been applied in the non-linear elasto-plastic finite element solver. [7] Solving these equations requires the calculation of the Jacobian which is costly in terms of CPU time and storage. To avoid this expense, matrix-free methods are employed.

  5. Sample preparation in mass spectrometry - Wikipedia

    en.wikipedia.org/wiki/Sample_preparation_in_mass...

    A particularly useful method involves depositing the matrix solution on the surface of the sample probe in a solvent that will evaporate very rapidly, thus forming a very thin fine layer of matrix. The sample solution is then placed on top of the matrix layer and allowed to evaporate slowly, thus integrating the sample into the top layer of ...

  6. Estimation of covariance matrices - Wikipedia

    en.wikipedia.org/wiki/Estimation_of_covariance...

    Simple cases, where observations are complete, can be dealt with by using the sample covariance matrix. The sample covariance matrix (SCM) is an unbiased and efficient estimator of the covariance matrix if the space of covariance matrices is viewed as an extrinsic convex cone in R p×p; however, measured using the intrinsic geometry of positive ...

  7. Matrix (mathematics) - Wikipedia

    en.wikipedia.org/wiki/Matrix_(mathematics)

    For example, if A is a 3-by-0 matrix and B is a 0-by-3 matrix, then AB is the 3-by-3 zero matrix corresponding to the null map from a 3-dimensional space V to itself, while BA is a 0-by-0 matrix. There is no common notation for empty matrices, but most computer algebra systems allow creating and computing with them.

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  9. Calibration curve - Wikipedia

    en.wikipedia.org/wiki/Calibration_curve

    A calibration curve plot showing limit of detection (LOD), limit of quantification (LOQ), dynamic range, and limit of linearity (LOL).. In analytical chemistry, a calibration curve, also known as a standard curve, is a general method for determining the concentration of a substance in an unknown sample by comparing the unknown to a set of standard samples of known concentration. [1]