Calibration curve

About: Calibration curve is a research topic. Over the lifetime, 6552 publications have been published within this topic receiving 95128 citations.

Short communication Simple high-performance liquid chromatographic method for the determination of tocotrienols in human plasma

Abstract: A simple high-performance liquid chromatographic method using fluorescence detection was developed for the determination of vitamin E especially d-, g- and a-tocotrienols in human plasma. The method entailed direct injection of plasma sample after deproteinization using a 3:2 mixture of acetonitrile-tetrahydrofuran. The mobile phase comprised 0.5% (v / v) of distilled water in methanol. Analyses were run at a flow-rate of 1.5 ml / min with the detector operating at an excitation wavelength of 296 nm and emission wavelength of 330 nm. This method is specific and sensitive, with a quantification limit of approximately 40, 34 and 16 ng / ml for a-, g- and d-tocotrienol, respectively. The mean absolute recovery values were about 98% while the within-day and between-day relative standard deviation and percent error values of the assay method were all less than 12.0% for a-, g- and d-tocotrienol. The calibration curve was linear over a concentration range of 40-2500, 30-4000 and 16-1000 ng / ml fora-, g- and d-tocotrienol, respectively. Application of the method in a bioavailability study for determination of the above compounds was also demonstrated. © 1999 Elsevier Science B.V. All rights reserved.

Direct Analysis of Pieces of Materials by Solid Sampling Electrothermal Atomic Absorption Spectrometry Demonstrated Using High-Purity Titanium

Abstract: Solid sampling electrothermal atomic absorption spectrometry using the boat technique and a transversely heated graphite tube was applied to direct analysis of pieces of high-purity titanium for Al, As, Ca, Co, Cr, Cu, Fe, K, Mg, Mn, Na, Ni, Pb, Sn, and Zn. It was found that the enthalpy for alloy formation between the analyte element and the titanium matrix plays an important role in the atomization mechanism. While the elements Ca, Cu, K, Mg, Mn, Na, Pb, and Zn could be determined without any modification, carbon powder was added to facilitate the vaporization of As, Co, Fe, Ni, and Sn and to eliminate the matrix interferences in the determination of Al and Cr. Quantification was performed by using a calibration curve obtained with use of aqueous standard solutions. Accuracy was checked by comparison of the results with those of three other methods. Sample amounts of up to 30 mg per atomization were applicable. The limits of detection for the 15 elements assayed were between 0.02 (Mg) and 30 ng/g (Sn).

Spectral filtering modulation method for estimation of hemoglobin concentration and oxygenation based on a single fluorescence emission spectrum in tissue phantoms.

Abstract: Purpose: Hemoglobin concentration and oxygenation in tissue are important biomarkers that are useful in both research and clinical diagnostics of a wide variety of diseases such as cancer. The authors aim to develop simple ratiometric method based on the spectral filtering modulation (SFM) of fluorescence spectra to estimate the total hemoglobin concentration and oxygenation in tissue using only a single fluorescence emission spectrum, which will eliminate the need of diffuse reflectance measurements and prolonged data processing as required by most current methods, thus enabling rapid clinical measurements. Methods: The proposed method consists of two steps. In the first step, the total hemoglobin concentration is determined by comparing a ratio of fluorescence intensities at two emission wavelengths to a calibration curve. The second step is to estimate oxygen saturation by comparing a double ratio that involves three emission wavelengths to another calibration curve that is a function of oxygen saturation for known total hemoglobin concentration. Theoretical derivation shows that the ratio in the first step is linearly proportional to the total hemoglobin concentrations and the double ratio in the second step is related to both total hemoglobin concentration and hemoglobin oxygenation for the chosen fiber-optic probe geometry. Experiments on synthetic fluorescent tissue phantoms, which included hemoglobin with both constant and varying oxygenation as the absorber, polystyrene spheres as scatterers, and flavin adenine dinucleotide as the fluorophore, were carried out to validate the theoretical prediction. Results: Tissue phantom experiments confirm that the ratio in the first step is linearly proportional to the total hemoglobin concentration and the double ratio in the second step is related to both total hemoglobin concentrations and hemoglobin oxygenation. Furthermore, the relations between the two ratios and the total hemoglobin concentration and hemoglobin oxygenation are insensitive to the scattering property of the tissue model for the chosen probe geometry. Conclusions: A simple two-step ratiometric method based on the SFM of fluorescence spectra is proposed to estimate the total hemoglobin concentration and oxygenation in a tissue model using only a single fluorescence emission spectrum. This method is immune to the variation in system throughput caused by inconsistent optical coupling because of its ratiometric nature. Calibration curves are insensitive to the scattering coefficient for the chosen probe geometry. Moreover, since only fluorescence intensities at a few wavelengths in a single fluorescence emission spectrum are needed in this method, the SFM method minimizes the amount of required data and reduces the data acquisition time. Finally, since this method does not use nonlinear regression, it can dramatically save computation time in data processing. The high sensitivity of the proposed method to superficial tissue volumes makes it ideal for fluorescence based oximetry and medical diagnostics in applications such as early epithelial cancer diagnosis or wherever the measured tissue volume is exposed to the outside such as in open surgery.