Determination of inosine 5′-monophosphate and guanosine 5′-monophosphate in pig feed by capillary zone electrophoresis

A capillary zone clectrophoresis method was developed for the determination of IMP and GIMP, commonly used as flavor enhancers in poultry feed, in a real sample of complex composition. A baseline separation of inosine 5′-monophosphate and guanosine 5′-monophosphate was achieved within 10 min and the other components in the sample did not interfere with the separation. Quantitative results obtained from pig feed samples are presented. The separation conditions and experimental reproducibility are also discussed.     

Theory of reflectance measurements in quantitative evaluation in TLC and HPTLC. 1. Multilayer model of reflectance and transmittance

In the approach described in this paper, the layer of adsorbent is divided into n sublayers. The radiation density in each sublayer is given by the sum of the transmittance and the reflectance of the adjacent sublayers. Absorption of light by the layer or the substance will diminish this radiation density. Depending upon the factors of reflectance and transmittance some light will pass to the adjacent sublayers. Two polynomials are derived from this readily understood formulation to calculate the reflectance or the transmittance of a layer of finite thickness. The algorithms given describe the reflectance and transmittance encountered in practical measurements with large amounts of substance per spot, as well as with small amounts. There are no restrictions with respect to nonideal scattering or reflection by the adsorbent layer support.     

Artificial neural networks for quantification in unresolved capillary electrophoresis peaks

The application of the combination of experimental design (ED) and artificial neural networks (ANNs) for the quantification of overlapped peaks in capillary zone electrophoresis is described. When the total separation cannot be achieved by separation techniques, the use of ED-ANN can be a suitable approach. The unstability of EOF causes peak shift that has to be corrected in order to apply ED-ANN methods. In this work, normalization procedure of electropherograms with consequent application of ANNs for quantification purpose was developed. Both, spectra and electropherograms can be used as multivariate data. In general, both kinds of data were found to be suitable for unresolved peaks quantification by ED-ANN approach.     

Quantitation in capillary electrophoresis-mass spectrometry

CE-MS has evolved into a strong alternative to LC-MS. Most of CE-MS applications deal with characterization and identification. However, quantitative aspects have gained importance in, e.g., pharmaceutical and biotechnological applications. Here we summarize and evaluate various methodological aspects in order to achieve sensitive and reproducible results. Similar to LC-MS, aspects of matrix influence on the electrospray process need to be carefully addressed when quantitative results are intended by CE-MS. Due to a more complicated coupling special emphasis needs to be put on the CE-MS interface. Generally linearity over more than three orders of magnitude can be achieved by CE-ESI-MS. Furthermore, a literature survey has been performed in order to give an overview over quantitative measurements performed by CE-MS. The precision can be doubled when changing from a structural related to an isotopically labeled internal standard. Thus a level of precision better than 5% RSD can be achieved.     

Qualitative supercritical fluid extraction coupled to capillary gas chromatography

The usefulness and ease of utilizing supercritical fluid extraction (SFE) directly coupled to capillary gas chromatography (GC) as quantitative or qualitative analytical problem-solving tools will be demonstrated. As an alternative to conventional liquid solvent extractions, SFE presents itself as a means to achieve high extraction efficiencies of different compounds in complex solid matrices in very rapid tims frames. Moreover, SFE has an additional advantage of being able to achieve distinct extraction selectivities as a function of the solubilizing power of the supercritical fluid extracting phase. For on-line SFE/GC, the extraction effluent is directly transferred to the analytical chromatograph. On-line SFE/GC involves the decompression of pressurized extraction effluent directly into a heated, unmodified capillary split injection port of the GC. In this respect, SFE introduction into GC can be used as an alternative means of GC injection, comparable to such modes of injection as pyrolysis and thermal desorption. This paper will show applications of SFE/GC where mass spectrometric detection together with flame ionization detection was used for component identification from environmental, tobacco, and petroleum matrices.     

Quantitative HPTLC determination of prostaglandin E1

Direct in situ determination of PGE₁ in dioxane/water (1:1) at concentrations between 50 μg/ml and 1 mg/ml is described. HPTLC of PGE₁ was carried out on HPTLC Kieselgel 60 o.F. plates; application (200 nl) was with a Nano-Appllcator and ethyl acetate/formic acid (400:5, v/v) served as mobile phase. The spots were located by dipping the plates into a 3% cupric acetate solution in 15% aqueous phosphoric acid, followed by heating at 120°C for 15 min. The plates were then evaluated directly at λ = 345 nm by chromatogram spectrometry. The coefficient of variation is 3.6%.     

Application of HPLC to measure vanadium in environmental,biological and clinical matrices

Vanadate and vanadium compounds exist in many environmental, biological and clinical matrices, and despite the need only limited progress has been made on the analysis of vanadium compounds. The vanadium coordination chemistry of different oxidation states is known, and the result of the characterization and speciation analysis depends on the subsequent chemistry and the methods of analysis. Many studies have used a range of methods for the characterization and determination of metal ions in a variety of materials. One successful technique is high performance liquid chromatography (HPLC) that has been used mainly for measuring total vanadium level and metal speciation. Some cases have been reported where complexes of different oxidation states of vanadium have been separated by HPLC. Specifically reversed phase (RP) HPLC has frequently been used for the measurement of vanadium. Other HPLC methods such as normal phase, anion-exchange, cation-exchange, size exclusion and other RP-HPLC modes such as, ion-pair and micellar have been used to separate selected vanadium compounds. We will present a review that summarizes and critically analyzes the reported methods for analysis of vanadium salts and vanadium compounds in different sample matrices. We will compare various HPLC methods and modes including sample preparation, chelating reagents, mobile phase and detection methods. The comparison will allow us to identify the best analytical HPLC method and mode for measuring vanadium levels and what information such methods provide with regard to speciation and quantitation of the vanadium compounds.     

Diffusion changes in patients with systemic lupus erythematosus

BACKGROUND AND PURPOSE: Systemic lupus erythematosus (SLE) is an autoimmune disease in which almost all the organs are involved. Neuropsychiatric SLE is of one of the major concerns in the clinical evaluation of this disease. Routine magnetic resonance imaging (MRI) findings are often nonspecific or negative. In this study, we explored the use of diffusion tensor imaging in assisting with the diagnosis of SLE. METHODS: Data from 34 SLE patients (age range, 18-73 years) and 29 age-matched volunteers (age range, 29-64 years) were analyzed. MRI was performed on a 1.5-T clinical MR scanner with a quadrature head coil. The average diffusion constant (D(av)) and diffusion anisotropy maps [fractional anisotropy (FA)] were determined on a pixel-by-pixel basis. Regional diffusion measurements were made by region of interest in the genu and splenium of the corpus callosum (CC), anterior and posterior limb of the internal capsule (IC) and frontal lobe and thalamus. The diffusion distribution was fitted to a triple-Gaussian model. The mean of the brain tissue distribution was determined as a mean diffusion constant for the whole brain (BD(av)). Student's t test was used to determine the diffusion difference between SLE patients and control subjects. The SLE patients were separated into two groups according to their MRI results. A P value lower than .05 was considered to be statistically significant. RESULTS: Twenty of the 34 SLE patients with abnormal MRI results showed findings dominated by nonspecific white matter disease. The BD(av) and D(av) values of the frontal lobe, splenium CC and anterior IC were significantly higher in all SLE patients as compared with the control subjects. The SLE patients with normal MRI results also showed higher BD(av) and D(av) values in the frontal lobe, splenium and anterior and posterior limbs of the IC as compared with the control subjects. There was no significant difference in the D(av) values of the thalamus between the SLE patients and the control subjects. The BD(av) value in the SLE patient group was robustly correlated with the D(av) values of the frontal lobe, splenium and thalamus. These correlations were found to be similarly significant for the SLE patients with normal MRI findings. The diffusion anisotropy measurements showed that splenium CC had the highest FA value in both the control subjects and SLE patients. Overall, SLE patients had lower FA values in the genu and splenium CC as compared with the control subjects. In the group of patients with normal MRI findings, the FA values of the genu and splenium CC as well as the anterior IC were also lower than those in the control subjects. Pearson's correlation statistics revealed robust correlations between the measurements of D(av) and FA values in the SLE patient group. CONCLUSION: Quantitative diffusion imaging and diffusion anisotropy showed early changes in the brains of the SLE patients. Increased BD(av) and D(av) values of the frontal lobe as well as decreased anisotropy in the genu CC and anterior IC may represent preclinical signs of central nervous system involvement of SLE even when the routine MRI findings are negative or nonspecific. Quantitative diffusion analysis may prove to be useful in detecting the initial brain involvement of SLE and may enable monitoring of early disease progression and treatment efficacy.