Application of a number of physical and chemical analysis methods the assessment of a multicomponent sample composition of natural water

.

Semiquantitative XRD analysis with the aid of reference intensity ratio estimates

Estimation of reference intensity ratios (ki or RIR) can be made on the basis of an atomic scattering function. Tests of regression equations for 50 compounds that predict an approximate reference intensity ratio from the easily computed scattering function have shown usefulness in multicomponent semiquantitative X-ray diffraction analysis. The method is best applied whenever only one or two minor components of a multicomponent sample have no readily measurable or calculable ki values and must be estimated. Where the difference between observed and predicted constants is large, these tests show that the ratios of true- to test-weight fractions are proportional to the corresponding ki ratios. The largest absolute errors occur whenever the ki must be predicted for components with medium weight fraction values. Estimation of ki for components of less than 10 weight percent results in only small errors in both predicted component and the other components of the sample. Where more than two components require predicted ki in a given sample, unacceptable errors for all components may result.

New Instrumentation for Use in Excitation-Emission Fluorescence-Polarization Measurements

A fluorescence excitation-emission matrix (EEM) is an excellent way to determine a specific substance in a multicomponent sample. In the present investigation, a novel, rapid-scanning spectrofluorometer has been developed for measuring an EEM; the instrument employs a 0.35-meter monochromator for choosing the excitation wavelength and a continuously variable interference filter for selecting the emission wavelength. With the system, a 51 × 93 excitation-emission matrix can be collected in 3.2 min, and detection limits of 500 ng/L are obtained for fluorescein dye in ethanol. Fluorescence polarization measurements in the plane parallel and perpendicular to the polarized excitation light adds another dimension to the instrument for characterizing a sample. The instrument is controlled by an IBM XT computer although data analysis is performed on a Macintosh computer with Spyglass software. A series of two-dimensional contour plots and multidimensional excitation-emission-polarization plots can be rapidly generated.

Quantitative Fourier-Domain Analysis. Part II: Determination of Boundary Conditions

A new approach for determining the boundary conditions of a Fourier-domain data set prior to performing quantitative multicomponent analysis has been developed. Processing boundary conditions were determined by calculating the condition number of the calibration matrix which contains the models used to describe the chemical system being studied. Once the boundary conditions for the Fourier-domain data set were determined, the Kalman filter was used to estimate the concentration of individual components in a multicomponent sample. Synthetic data were first analyzed to determine both the feasibility of the data-analysis method and the effect that background variations would have on the concentration estimates. Raw interferograms of multicomponent samples, collected with the use of Fourier transform infrared (FT-IR) spectroscopy, were also analyzed. Validation samples were analyzed to verify the chosen boundary conditions.