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Bucharest, Romania

Petroviciu I.,National Research Institute for Conservation and Restoration INCCR | Albu F.,Science Labormed Pharma SA | Medvedovici A.,University of Bucharest
Microchemical Journal | Year: 2010

Identification of dyes in historic textiles was until recently only based on reversed phase liquid chromatography and diode-array detection (RPLC-DAD). Although in the last years mass spectrometry (MS) is increasingly used as a detection system for liquid chromatography, most applications in the field are directed to identification of the molecular ions or in studies dedicated to degradation products which may be used as markers in RPLC-DAD. In the present work, an analytical protocol for the identification of dyes using RPLC/ESI/MS is presented. Atmospheric pressure electrospray ionization (ESI) was applied, in the negative ion monitoring mode. Both single stage and tandem MS (MS/MS) approaches were considered. An ion trap was used as mass analyzer. Experiments are based on the characterization of standards (natural dyes and/or dyed fibers) with the mass spectrometer sequentially working in the following modes: single MS/full scan, followed by plotting chromatograms through ion extraction (IEC) according to mass/charge ratios corresponding to molecular ions; single MS/selected ion monitoring (SIM) mode; tandem MS/single reaction monitoring (SRM) mode; tandem MS/multiple reactions monitoring (MRM) or product ion scanning modes. A faster chromatographic separation could be applied as MS detection readily balanced the selectivity of the analytical process. In a case study, 11 dyes from 3 biological sources were detected in a 0.5 mg historic sample. © 2009 Elsevier B.V. All rights reserved.

Medvedovici A.,University of Bucharest | Albu F.,Science Labormed Pharma SA | David V.,University of Bucharest
Journal of Liquid Chromatography and Related Technologies | Year: 2010

Hyphenation of mass spectrometry (MS) to liquid chromatography (LC) represents a powerful tool for qualitative and quantitative characterization of target compounds in very complex matrixes of biological origins. In spite of many advantages due to recent advances and innovations in the area of instrumentation and dedicated software support, some difficulties are still encountered in its current applications. The large variety of functional principles and technical solutions applied for hyphenation of the two techniques, for ion sources, ion extraction and focusing, mass analysis, and ion counting makes it more difficult to obtain perfect agreement between the intrinsic characteristics of the laboratory-available instrumentation and the declared goals of specific determination. This review covers a part of the literature data dealing with the shortcomings of LC/MS in bioanalysis. The following topics are discussed: structural identification and confirmation in LC/MS; precision of the instrumental response over short and long term periods; non-linear response functions; adduct formation in atmospheric pressure ion sources; and carryover effects. Most of the problems arising in LC/MS are related to phenomena occurring during ionization. Obviously, the structural characteristics of the analyzed compounds play an important role, although the principles of ionization within the source and the supporting technical solutions and constructive designs add their own particular features. The complex influence of residual sample matrixes over ionization yields of target compounds and internal standards needs to be studied through proper experimental procedures, in order to control both precision and instrumental response function in analysis of biological samples. Copyright © Taylor & Francis Group, LLC.

Tanase A.,University of Bucharest | Miu A.,Science Labormed Pharma SA
Revue Roumaine de Chimie | Year: 2012

A simple and high throughput method suitable for routine determination of nickel in magnesium stearate (as pharmaceutical excipient) by GF-AAS with pyrolytic graphite coated tube transversely heated, after simple dissolution of the sample in acidified ethanol, without mineralisation, has been validated. The validation approach directly refers to linearity, detection and quantification limits, characteristic mass, selectivity (matrix effect), precision (repeatability and intermediate precision), accuracy and robustness. Linearity of response was verified for concentrations ranging from 0 to 12 ng/mL of nickel in standard solution in ethanol and was characterized by a correlation coefficient R of 0.9999. Detection limit of the proposed method was found to be 0.84 ng/mL (corresponding to 0.42 μg/g of nickel in the real sample), and the quantification limit was 2.54 ng/mL (corresponding to 1.27 μg/g of nickel in the real sample). The characteristic mass was m0 = 13.62 ± 0.67 pg of nickel. Repeatability and intermediate precision of the method are characterized by relative standard deviations ranging between 2.7 - 6.6% and 5.0 - 9.3%, respectively. Accuracy expressed as recovery gave values ranging between 98.6% and 100.5%. The overall recovery was 99.6%. The robustness was tested by varying the temperatures used for programming the graphite furnace stages and the experimental results were statistically compared through of F-test and Student f-test.

Medvedovici A.,University of Bucharest | Udrescu S.,Science Labormed Pharma SA | David V.,University of Bucharest
Biomedical Chromatography | Year: 2013

Limonene, considered a green solvent, was successfully used to extract simvastatin, lovastatin, and their hydroxy-acid metabolites from human plasma samples. The extraction process was followed by the direct injection of a large volume aliquot (100 μL) from the limonene layer into a Zorbax SB-C18 Rapid Resolution chromatographic column (50mm length×4.6mm i.d. × 1.8μm d.p.), operated under gradient elution reversed-phase separation mechanism. Tandem mass spectrometry operated under the multiple reaction monitoring mode was used for detection, providing low quantitation limits in the 0.25-0.5ng/mL concentration interval. This method was validated and used for quantitation of simvastatin and its hydroxy acid metabolite in incurred plasma samples obtained from two volunteers participating in a bioequivalence study, using lovastatin and its hydroxy analog as internal standards. The results were statistically compared with those produced by means of an alternative RPLC-tandem MS using protein precipitation with acetonitrile. The quality attributes of the two methods are comparatively discussed. The agreement between the quality characteristics of the two methods and the experimental results obtained on real samples may be considered as a consistent basis for the simultaneous use of limonene as extraction medium and injection diluent for hydrophobic compounds in bioanalytical approaches. © 2012 John Wiley & Sons, Ltd.

Petroviciu I.,National Museum of Romanian History | Petroviciu I.,University of Bucharest | Medvedovici A.,University of Bucharest | Albu F.,Science Labormed Pharma SA | And 2 more authors.
Romanian Reports in Physics | Year: 2012

An analytical protocol for the identification of natural dyes in historic textiles by LC-MS and LC-MS/MS was recently developed for the first time in Romania. The present study discusses the application of this approach in the identification of dyes and biological sources in very low amounts of fibers from textiles in local collections.

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