Elimination Of Spectral Interferences Research Articles

Ion-exchange HPLC-ICP-MS: A new window to chromium speciation in biological tissues

The presented work proposes a novel analytical ICP-MS-based approach for the accurate and precise chromium speciation in biological tissues. The determination of total Cr(VI) and soluble Cr(III) species was carried out by alkaline EDTA extraction followed by their separation using ion-exchange high-performance liquid chromatography inductively coupled plasma mass spectrometry (IE-HPLC-ICP-MS). The developed method was validated according to the procedure given in the United States Food and Drug Administration guideline on the validation of bioanalytical methods. Validation parameters included limit of detection (≤ 0.03 μg g−1), limit of quantification (≤ 0.08 μg g−1), linearity (r ≥ 0.9998), intra-day and inter-day accuracy (86–110%) and precision (≤ 10%), extraction recovery (89–110%), carry-over effect and sensitivity. In addition, special attention was paid to the study of chromium species interconversion and the elimination of spectral interferences. Moreover, the validated ICP-MS method employing microwave acid digestion was used to determine the total Cr content in collected fractions. Finally, the whole ICP-MS-based methodology was applied to the analyses of two certified reference materials of hepatopancreas tissue. Obtained results indicated that the majority of chromium in biological tissues is bound to the solid residue, Cr(VI) was determined in none of the samples investigated. This is the first study focusing on soluble Cr(III), total Cr(VI), and total bound Cr species in biological tissues. It is characterized by efficient sample preparation and fast simultaneous analysis of Cr species with parallel total Cr analysis serving for chromium balance evaluation.

Quantitative determination of anthocyanins in three sweet cherry varieties using diffuse reflectance infrared Fourier transform spectroscopy

The determination of sweet cherry anthocyanins in crude material of three varieties using diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and the curve-fitting deconvolution method is described. A linear relationship between the sweet anthocyanins content and the peak area at 1640–1630 cm −1 was established with a high correlation coefficient (0.990). The deconvolution analysis using the curve-fitting method allowed the elimination of spectral interferences from other cell wall components. The proposed methodology was compared with a reference UV–vis spectrophotometric method and found equivalent in reproducibility and accuracy ( F-test, t-test). The proposed method is simple, rapid, non-destructive for the analytical samples and could be applicable to any cherries.

On-line preconcentration and recovery of palladium from waters using polyaniline (PANI) loaded in mini-column and determination by ICP-MS; elimination of spectral interferences

The applicability of polyaniline (PANI) for the on-line preconcentration and recovery of palladium from various water samples has been investigated. Batch experiments were performed to optimize conditions such as pH and contact time to achieve quantitative separation of Pd spiked at high (μg ml −1) and low levels (ng ml −1). During all the steps of the removal process, it was found that Pd was selectively removed by PANI even in the presence of various ions. Quantitative removal of Pd occured in the entire studied pH range (1–12) and the K d value was found to be >10 6. Kinetic studies show that a contact time of <4 min was adequate to reach equilibrium. The retained Pd was subsequently eluted with a mixture of HCl and thiourea, optimized using a factorial experimental design approach. ICP-OES was used for the micro-level determinations of Pd whereas ICP-MS was used for the determination of Pd at sub-ppb levels. Breakthrough curve using column experiments demonstrated that PANI has an excellent ability to accumulate up to ∼120 mg g −1 of Pd from synthetic sample solutions. A preconcentration factor of about 125 was achieved for Pd when 250 ml of water was passed. PANI columns prepared were used up to 10 times in consecutive retention–elution cycles without appreciable deterioration in their performance. The proposed on-line method also has the ability to remove interfering elements Cu and Y for the determination of Pd in waters by ICP-MS. The reported method has been applied successfully for the determination of Pd in ground water, lake water sea-water and waste water samples. The recoveries were found to be >95% in all cases. These studies indicate that PANI has an excellent ability to preconcentrate Pd from various waters making the method very promising for the determination of Pd.

Determination of the degree of esterification of pectinates with decyl and benzyl ester groups by diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and curve-fitting deconvolution method

Pectinates with benzyl and decyl ester groups were prepared by alkylation of the tetrabutylammonium salt of pectic acid with benzyl and decyl bromides, respectively. The degree of esterification (DE) of the pectin derivatives was determined by diffuse reflectance infrared Fourier transform spectroscopy and the curve-fitting deconvolution method. A linear relationship between DE and the ratio of the peak area at 1745 cm −1 to the sum of the peak areas at 1745 and 1608 cm −1 was established with a high correlation coefficient 0.98. The deconvolution analysis using the curve-fitting method allowed the elimination of spectral interferences from pectin components and their degradation products. The limits of the method are given by DE 6 and 93%. The method was compared with chemical analysis and found to be equivalent in view of accuracy and repeatability ( t-test, F-test). The method is applicable in analysis of natural or synthetic mixtures and/or crude pectin substances.

Determination of Uronic Acids in Isolated Hemicelluloses from Kenaf Using Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) and the Curve-Fitting Deconvolution Method

Hemicellulose samples were isolated from kenaf (Hibiscus cannabinus L.). Hemicellulosic fractions usually contain a variable percentage of uronic acids. The uronic acid content (expressed in polygalacturonic acid) of the isolated hemicelluloses was determined by diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and the curve-fitting deconvolution method. A linear relationship between uronic acids content and the sum of the peak areas at 1745, 1715, and 1600 cm(-1) was established with a high correlation coefficient (0.98). The deconvolution analysis using the curve-fitting method allowed the elimination of spectral interferences from other cell wall components. The above method was compared with an established spectrophotometric method and was found equivalent for accuracy and repeatability (t-test, F-test). This method is applicable in analysis of natural or synthetic mixtures and/or crude substances. The proposed method is simple, rapid, and nondestructive for the samples.

Detection and correction of interferences in spectroscopy techniques

By combining the apparent content curves method and the Youden method, we have developed a strategy for detecting constant and proportional errors in spectroscopy techniques. A method for elimination of spectral interferences (different of blank) is also proposed. To apply of this method there must be a matrix effect that varies with the amount of sample or a simulated matrix effect provided working under different experimental conditions that induce a variation of the analytical signal of the analyte. The proposed procedures have been applied to the determination of methyl orange in presence of phenol red, bromothymol blue and bromocresol purple.

A silver solution for surface-enhanced Raman scattering

A silver solution has been prepared from the reduction of silver nitrate (AgNO3) by hydrogen peroxide (H2O2) under basic conditions for surface-enhanced Raman scattering (SERS). Reaction conditions such as temperature, time, absence of oxygen, pH of the reaction mixture, and reagent purity have been found to be important factors contributing to the reaction process and the SERS performance of the substrate product. These factors have been evaluated and optimized. It was found that the T=0°C, long reaction period, nitrogen or inert gas purging, and alkaline conditions are essential for preparing the SERS-active silver solution. The purity of reagents is as important as other factors. One major advantage of this reduction process for producing the substrate for SERS is the reduction or elimination of spectral interference caused by the reaction by-products. Two series of experiments have been conducted to test the shelf life and the aging effect of the substrate on the SERS intensity. Some SERS activities of the silver solution substrate have been compared with those of other sols. An excitation profile as well as the dependence of SERS data on UV illumination, oxidizing agent and reducing agent have been collected and discussed in terms of SERS phenomena.

FT-IR spectroscopic determination of the degree of esterification of cell wall pectins from stored peaches and correlation to textural changes

The FT-IR spectroscopic study of peach cell walls revealed the existence of two peaks absorbing at 1749 and 1630 cm −1 assigned, respectively, to the absorption of the esterified and non-esterified carboxyl groups of the pectin molecules. A linear relationship between the degree of esterification [(number of esterified carboxylic groups/number of total carboxylic groups)×100] and the ratio of the area underneath the peak at 1749 cm −1 over the sum of the areas underneath the two peaks, at 1749 and 1630 cm −1, was established using the FT-IR spectra of standard compounds. The use of the 2nd derivative and curve-fitting techniques allowed the elimination of spectral interferences from other cell wall components. The degree of esterification (D.E.) of pectins from Redhaven peaches immediately after harvest and during storage was evaluated from FT-IR data. During storage at 0°C, the D.E. remained practically constant up to 35 days. During storage at higher temperatures it decreased approaching a final value — the same for all temperatures. This value was reached after 22 days of storage at 5°C, 15 days at 15°C and after only 6 days at 20°C. The changes in the degree of esterification during storage correlated well to fruit firmness.

Elimination of spectral interferences in the reaction of 2-thiobarbituric acid with malonaldehyde, 2-furfuraldehyde and 5-hydroxymethyl-2-furfuraldehyde by partial least squares multivariate calibration (PLS)

The spectral resolution of ternary mixtures of malonaldehyde (MLD), 2-furfuraldehyde (FUR) and 5-hydroxymethyl-2-furfuraldehyde (HMF) in the presence of glyoxal and biliverdine is achieved by partial least squares multivariate calibration (PLS). The spectrophotometric method is based on the reaction of these substances with 2-thiobarbituric acid (TBA). A calibration set of standard samples has been statistically designed in the presence of adequate amounts of both interferent compounds in several degrees of concentration. The possibility of a spectrophotometric determination of mixtures of MLD, FUR and HMF in the presence of glyoxal and biliverdine is demonstrated. A comparative study of the results found by application of PLS-1 and PLS-2 methods is presented.

Determination of malonaldehyde in human plasma: elimination of spectral interferences in the 2-thiobarbituric acid reaction.

A selective, derivative spectrophotometric method has been developed for the determination of malonaldehyde (MLD), based on a reaction with 2-thiobarbituric acid (TBA). The proposed method has been applied to the determination of MLD in human plasma. A study to eliminate several spectral interferences is described. A comparative study of the results obtained using the proposed derivative method and a conventional TBA method applied to human plasma is presented and the advantages of the proposed method over the conventional method for the determination of MLD in human plasma are evaluated.

Elimination of spectral interferences in inductively coupled plasma-atomic emission spectroscopy using orthogonal polynomials

Orthogonal polynomials have been applied to correct for spectral interferences in ICP-AES. The emission spectra of many analytes measured over fairly wide wavelength ranges have characteristic normal probability distribution profiles (quadratic pattern) centering on the prominent line of each element. The emission spectra of many interferents (with the exception of direct line overlap) display more or less linear shapes over the same analyte wavelength range. Accordingly, a quadratic polynomial fitting results in coefficient values that relate largely to the concentration of the analyte and negligibly to the concentration of interferents. The method has been demonstrated to cancel the interference caused by the presence of 1000 mg l concentrations of Ca, Mg, Al and Fe in the analysis of selected elements (Cr, Cu, Mn, P, Zn, S and Pb) at their most sensitive prominent lines. The results indicate not only the efficacy of the proposed method for eliminating such interferences, but also its superiority over the currently used two- and three-point correction procedures.

中空陰極管の交流放電励起によるＳ／Ｎ比の向上について

中空陰極管の交流放電励起によるＳ／Ｎ比の向上について

Elimination of spectral interferences in the determination of Se in nickel-base alloys using Zeeman background correction

Spectral interferences from the presence of nearby matrix lines can occur when using continuum source background correction. An interference of this type exists when determining Se in nickel-base alloys using deuterium background correction. This interference introduces a significant analytic error at both the 196.0- and 204.0-nm Se lines. By comparison, Zeeman effect background correction is free of any spectral interference problem. Zeeman background correction, used in conjunction with the stabilized temperature platform furnace, permitted accurate analysis without the requirement for matrix-matched standards.