Hesperidin, a bioflavonoid, is an abundant and inexpensive by-product of Citrus cultivation. A deficiency of this substance in the diet has been linked with abnormal capillary leakiness as well as pain in the extremities causing aches, weakness and night leg cramps. No signs of toxicity have been observed with the normal intake of hesperidin or related compounds. Both hesperidin and its aglycone hesperetin have been reported to possess a wide range of pharmacological properties. This paper reviews various aspects of hesperidin and its related compounds, including their occurrence, physical and chemical properties, analysis, pharmacokinetics, safety and toxicity and the marketed products available. A special emphasis has been laid on the pharmacological properties and medicinal uses of these compounds.

Chemistry and pharmacology of the citrus bioflavonoid hesperidin

Validation of bioanalytical LC-MS/MS assays: evaluation of matrix effects.

Matrix-dependent signal suppression or enhancement represents a major drawback in quantitative analysis with liquid chromatography coupled to atmospheric pressure ionization mass spectrometry (LC-API-MS). Because matrix effects (ME) might exert a detrimental impact on important method parameters (limit of detection, limit of quantification, linearity, accuracy, and precision), they have to be tested and evaluated during validation procedure. This review gives a detailed description on when these phenomena might be expected, and how they can be evaluated. The major sources of ME are discussed and illustrated with examples from bioanalytical, pharmaceutical, environmental, and food analysis. Because there is no universal solution for ME, the main strategies to overcome these phenomena are described in detail. Special emphasis is devoted to the sample-preparation procedures as well as to the recent improvements on chromatographic and mass spectrometric conditions. An overview of the main calibration techniques to compensate for ME is also presented. All these solutions can be used alone or in combination to retrieve the performance of the LC-MS for a particular matrix-analyte combination.

An overview of matrix effects in liquid chromatography-mass spectrometry.

Signal suppression/enhancement in high-performance liquid chromatography tandem mass spectrometry

Advances in water chemistry in the last decade have improved our knowledge about the genesis, com- position, and structure of dissolved organic matter, and its effect on the environment. Improvements in analyti- cal technology, for example Fourier-transform ion cyclo- tron (FT-ICR) mass spectrometry (MS), homo and hetero-correlated multidimensional nuclear magnetic res- onance (NMR) spectroscopy, and excitation emission matrix fluorimetry (EEMF) with parallel factor (PARAFAC) analysis for UV-fluorescence spectroscopy have resulted in these advances. Improved purification methods, for example ultrafiltration and reverse osmosis, have enabled facile desalting and concentration of fresh- ly collected DOM samples, thereby complementing the analytical process. Although its molecular weight (MW) remains undefined, DOM is described as a complex mixture of low-MW substances and larger-MW biomo- lecules, for example proteins, polysaccharides, and exo- cellular macromolecules. There is a general consensus that marine DOM originates from terrestrial and marine sources. A combination of diagenetic and microbial processes contributes to its origin, resulting in refractory organic matter which acts as carbon sink in the ocean. Ocean DOM is derived partially from humified products of plants decay dissolved in fresh water and transported to the ocean, and partially from proteinaceous and poly- saccharide material from phytoplankton metabolism, which undergoes in-situ microbial processes, becoming refractory. Some of the DOM interacts with radiation and is, therefore, defined as chromophoric DOM (CDOM). CDOM is classified as terrestrial, marine, anthropogenic, or mixed, depending on its origin. Ter- restrial CDOM reaches the oceans via estuaries, whereas autochthonous CDOM is formed in sea water by micro- bial activity; anthropogenic CDOM is a result of human activity. CDOM also affects the quality of water, by shielding it from solar radiation, and constitutes a car- bon sink pool. Evidence in support of the hypothesis that part of marine DOM is of terrestrial origin, being the result of a long-term carbon sedimentation, has been obtained from several studies discussed herein.

Molecular characterization of dissolved organic matter (DOM): a critical review

A major limitation in quantitative analysis with electrospray ionization mass spectrometry (ESI-MS) is represented by the so-called matrix effects in which the matrix coextracted with the analytes can alter the signal response, causing either suppression or enhancement, resulting in poor analytical accuracy, linearity, and reproducibility. In the direct electron ionization liquid chromatography-mass spectrometry (direct-EI LC-MS) interface the ionization process is based on electron impact ionization, and it occurs in the gas phase and is not influenced by coeluted matrix compounds. In this work we quantitatively evaluated matrix effects on enriched environmental and biological samples, with different extraction procedures, using ESI and direct-EI LC-MS. As expected, the samples analyzed with direct-EI were not affected by matrix composition, whereas with ESI we observed either signal suppression or enhancement, depending on the sample nature.

Overcoming matrix effects in liquid chromatography-mass spectrometry

A new LC/MS method for the determination of organophosphorus pesticides in water, based on the use of direct-electron ionization (EI) interface, is presented. Direct-EI is a new device that, in a very simple fashion, couples a nano-HPLC system with a mass spectrometer equipped with electron ionization capability. The nanoscale liquid flow allows for a direct introduction of eluate into the ion source and, after nebulization, for its ionization under typical EI conditions. Library-matchable EI spectra are generated for a choice of full scan or SIM detection of the analytes. In our case, a selection of organophosphorus pesticides, commonly distributed in local sugar beet cultivation, were considered. The new interface permits a very sensitive detection of the analytes in a wide range of linear response (0.09−9 ng). When applied to a real sample, the method allowed detecting four different pesticides at a concentration level of approximately 3 ng·L-1.

Trace level determination of organophosphorus pesticides in water with the new direct-electron ionization LC/MS interface.

Contamination of water resources by organochlorine pesticides (OCPs) continues to receive widespread attention because of the increasing concern regarding their high persistence and bioaccumulation. These organic pollutants are not amenable by liquid chromatography (LC) coupled to atmospheric pressure ionization-mass spectrometry, which represents the method of choice for the characterization of pesticide residues in water. Gas chromatography−mass spectrometry provides excellent response for OCPs, but it falls short when complex, multiresidue analyses are required. As recently demonstrated, an efficient EI-based LC−MS interface can generate very good spectra for an extremely wide range of small−medium molecular weight molecules of different polarity and can represent a valid tool in solving the analytical challenge of analyzing OCPs by LC−MS. Based on this assumption, we present a new approach for the determination of 12 OCPs in water samples. The method requires a solid-phase extraction preconcentration ...

Organochlorine Pesticides by LC−MS

A new method for the determination of 32 base/neutral and 13 acidic pesticides in water, which has been proven to be particularly amenable to high-performance liquid chromatography, is discussed. A liquid/solid extraction procedure for the isolation of pesticides from aqueous samples is employed. The LC/MS analysis is carried out with a LC-18 reversed-phase packed capillary column coupled with a Hewlett-Packard 5989A quadrupole mass spectrometer using a new microliter flow rate particle beam interface. Mobile-phase flow rates, ranging between 1 and 5 μL/min, pass into the electron impact ion source of the mass spectrometer

Giorgio Famiglini

Papers

An overview of matrix effects in liquid chromatography-mass spectrometry.

Overcoming matrix effects in liquid chromatography-mass spectrometry

Trace level determination of organophosphorus pesticides in water with the new direct-electron ionization LC/MS interface.

Organochlorine Pesticides by LC−MS

Determination of Acidic and Basic/Neutral Pesticides in Water with a New Microliter Flow Rate LC/MS Particle Beam Interface