Antonio Di Corcia

Monitoring aromatic surfactants and their biodegradation intermediates in raw and treated sewages by solid-phase extraction and liquid chromatography.

On the basis of solid-phase extraction, a simple procedure for determining simultaneously two aromatic surfactant classes, i.e., linear alkylbenzene sulfonates (LAS) and nonylphenol polyethoxylates (NPEO), as well as their biodegradation intermediates in raw and treated sewages is presented. This procedure involved passing 10 and 100 mL of an influent and effluent water sample, respectively, through a 1-g graphitized carbon black (GCB) extraction cartridge. By exploiting the presence of positively charged active centers on the GCB surface, we succeeded in fractionating the complex mixture of the analytes considered by differential elution. The first fraction contained NPEO and nonylphenol (NP)

Liquid chromatographic-mass spectrometric methods for analyzing antibiotic and antibacterial agents in animal food products.

Public health agencies in many countries rely on detection by mass spectrometry for unambiguous identification of residues of antibiotic and antibacterial agents in animal food products for human consumption. The introduction of relatively inexpensive and robust LC-MS systems has given a strong impulse to develop determinative and confirmatory methods for the above medicines in foodstuffs. This impulse has been also dictated by thermal instability and lack of volatility of many antibiotics and antibacterials that makes the GC-MS technique of difficult application. Analytical methods developed for analyzing components of the major classes of the medicines mentioned above are here reviewed. The discussion is focused on both sample treatment and final LC-MS analysis.

Recent applications of liquid chromatography–mass spectrometry to residue analysis of antimicrobials in food of animal origin

Residual antimicrobials in food constitute a risk to human health. Although epidemiological data on the real magnitude of their adverse effects are very scarce, they indicate that food could be an important vehicle for evolution and dissemination of antimicrobial-resistant bacteria. Public health agencies in many countries rely on detection by mass spectrometry (MS) for unambiguous identification of residues of antimicrobial agents in animal food products for human consumption. The introduction of relatively inexpensive and robust liquid chromatography (LC)–MS systems has given a strong impulse to the development of confirmatory methods for the above medicines in foodstuffs. The initial part of this review, after a brief introduction into the field of antimicrobials, is dedicated to the most important EU regulations and directives for control of residues of these substances in animal products. The main attention in this review is on the sample-treatment and MS detection systems in use today for analysing the most important classes of antimicrobials in various biological matrices (milk, animal tissues, eggs, and honey). As evidenced by this review, reversed-phase LC combined with tandem MS, usually triple-quadrupole MS (QqQMS), is currently the preferred technique in most residue analysis of a single-class of antimicrobials. A recently emerging analytical strategy is that of developing methods for detecting a large variety of veterinary drugs belonging to different classes, including pesticides (multi-class residue analysis). To do this, simple and generic extraction and separation techniques applicable to a broad range of compounds differing in physical and chemical properties have been adopted. Such methods are still based mainly on LC–QqQMS. Emerging alternative MS detection systems are time-of-flight MS, which provides accurate mass of the analyte(s), or Q–linear ion trap (IT) MS that eliminates some limitations of ITMSn.

Reversed-phase high-performance liquid chromatographic determination of linear alkylbenzene sulphonates, nonylphenol polyethoxylates and their carboxylic biotransformation products

Abstract The possibility was investigated of simultaneously determining linear alkylbenzene sulphonates, nonylphenol polyethoxylates and their respective biotransformation products, namely sulphophenyl carboxylates (SPC) and nonylphenoxy carboxylates, by reversed-phase high-performance liquid chromatography with UV and fluorescence detection. Both the ion-suppression and the ion-pair techniques were taken into account for separating the compounds of interest. Each technique exhibited peculiar characteristics of resolution and sensitivity. Differences in the selectivity of the chromatographic system on using either methanol or acetonitrile as organic modifier were also considered. Liquid-solid extraction by an octadecyl-bonded silica (C 18 ) cartridge was employed to isolate all the compounds considered from a sewage treatment plant effluent sample. The recovery of SPC with up to six carbons in the carboxylate chain was unsatisfactory. The SPC distribution appeared to be dominated by the homologues having 5–8 carbon atoms in the carboxylate chain.

Evaluation of graphitized carbon black as a selective adsorbent for extracting acidic organic compounds from water

Abstract By a simple and rapid treatment, graphitized carbon black (GCB) can be made to act as both a reversed phase and an anion exchanger. The base—neutral/acid fractionation of organic species extracted from water with a GCB cartridge can be easily achieved by differential elution, provided that the pKa values of the acidic species are not higher than about 7. A tetramethylammonium hyroxidebasified solvent mixture is the most effective eluent for the rapid elution from a GCB extraction cartridge of any kind of organic acid. The subfractionation of acidic species can be easily performed on the basis of their acidity strength by passing sequentially through a GCB cartridge various solvent mixtures containing suitable phase modifiers. The ability of a GCB extraction cartridge to retain organic acids was unaffected by the ionic strength of the water sample. The influence of fulvic acids dissolved in water on the capability of GCB to extract acidic compounds and isolate them from co-extracted base—neutral species was evaluated. The advantage of using a GCB cartridge over that containing a chemically bonded silica for accurately determining acidic compounds is demonstrated by two practical applications.

Seasonal succession of Cylindrospermopsis raciborskii and Aphanizomenon ovalisporum blooms with cylindrospermopsin occurrence in the volcanic Lake Albano, Central Italy

The cyanobacterial toxin cylindrospermopsin is rapidly spreading in the European temperate Countries. Cylindrospermopsin was detected for the first time in Italy in 2004; in this study, the presence of this toxin in Albano Lake (Central Italy) has been correlated to the cyanobacterial species Cylindrospermopsis raciborskii and Aphanizomenon ovalisporum and their population dynamics. In 2004, these two species succeeded in the lake during spring, summer, and early autumn without overlapping, causing superficial blooms. Cylindrospermopsin was detected in lake samples by LC‐MS/MS and ELISA immunoassay, showing extracellular superficial values ranging from 2.6 to 126 μg/L, and water column values ranging from 0.41 to 18.4 μg/L. Twenty‐six of 30 positive water samples (86%) exceeded the recommended limit of 1 μg/L. Intracellular values up to 42.3 μg/g were measured. Moreover, cylindrospermopsin was detected in tissues from two Salmo trutta trouts (up to 2.7 ng/g) and in a well for drinking water supply (1.6 μg/L). For the first time, two cyanobacterial species producing cylindrospermopsin were detected in the same lake in Italy.

Trace determination of phenols in natural waters extraction by a new graphitized carbon black cartridge followed by liquid chromatography and re-analysis after phenol derivatization

Abstract Based upon solid-phase extraction, a sensitive, selective and robust liquid chromatography (LC) procedure for determining the U.S. EPA eleven priority pollutant phenols in natural waters is presented. The method involves passing 4 and 11, respectively, of drinking and river waters through a reversible cartridge filled with 0.5 g of a new example of graphitized carbon black (Carbograph 4) at flow-rates of about 100 ml/min. After washings, phenols are eluted by reversing the cartridge and back-flushing it with 6 ml of a CH 2 Cl 2 CH 3 OH mixture containing tetrabutylammonium chloride, 10 mmol/1. The eluate is then divided in two equal portions that are taken to dryness. After reconstituting the residue of one portion of the extract with a suitable solution, phenols are separated and quantified by ion-suppression, reversed-phase LC with UV detection. The goal of analyzing phenols with a low probability of false positives can be easily reached by converting phenols in the second portion of the extract to acetyl derivatives. The reaction mixture is then injected into the same analytical column and confirmation of the eventual presence of certain phenols in the sample is obtained by observing the disappearance of the peaks for phenols and the simultaneous appearance of peaks for the corresponding acetyl derivatives. By this method, the presence of 1.3 μg/l of 2-chlorophenol in a surface water sample was ascertained. Recovery of phenols, including phenol itself, were higher than 90%. Conversion of phenols to acetyl derivatives was completed by reacting 40 μl of acetic anhydride for 6 min at 50°C, except for 4,6-dinitro-2-methylphenol (78% reaction yield).

Evaluation of two new examples of graphitized carbon blacks for use in solid-phase extraction cartridges

Abstract The performances of two new examples of graphitized carbon blacks (GCBs), Carbograph 4 and Carbograph 5, filling solid-phase extraction cartridges were evaluated. Compared to an older GCB, Carbograph 1, the two new GCBs exhibited far larger abilities in extracting very polar compounds from both 4 l of drinking water and 1 l of water containing an amount of humic materials equivalent to 20 mg/l dissolved organic content. Like older GCB material, the new examples of GCBs have on their surfaces anion-exchange adsoprtion sites. However, Carbograph 5 partly failed to isolate acidic species from co-extracted non-acidic species by stepwise elution. Moreover, the surface of this sorbent material is more contaminated than those of both Carbograph 1 and 4 by sites able to bind irreversibly particular adsorbates. The extraction efficiencies of the two new GCBs were also compared with those of two recently introduced polystyrene-divinylbenzene (PS-DVB)-based materials. Recovery data showed that the carbonaceous materials were abler than PS-DVB ones in isolating very polar compounds from large water volumes, such as phenol, water-soluble pesticides, and low-molecular-mass biointermediates of linear alkylbenzenesulfonate surfactants. The positive features of including Carbograph 4 extraction cartridges in analytical schemes for determining traces of very polar pollutants in natural waters are demonstrated by three practical applications.

Quantification of phenylurea herbicides and their free and humic acid-associated metabolites in natural waters.

There is increasing interest in and demand for simultaneously monitoring pesticides as well as related degradation products (DPs) in natural waters, as the latter compounds can be even more toxic than the former ones. A method for determining parts per trillion levels of phenylurea herbicides and their DPs, that is their dealkylated forms and aromatic amines, is described. This method is based on solid-phase extraction with a Carbograph 4 cartridge followed by liquid chromatography (LC) with electrospray (ES) mass spectrometric detection. A study aimed at optimizing the response of the ES-MS detector for very weakly basic chloroanilines was conducted. Results showed that ion signal intensities of the above species were dependent on the composition of the LC mobile phase to an astonishing degree. At concentration levels of a few hundred ng/l, laboratory experiments showed that the aromatic amines considered here were mostly associated to dissolved humic acids (HAs) by both reversible and irreversible bindings. The addition of a reducing agent, i.e., NaBH4, succeeded in liberating that fraction of aromatic amines, which being reversibly bound to quinoidal structures of HAs are bioavailable. Analyte recoveries were better than 85% on extraction from 4 l of drinking water (spike level, 25 ng/l), 2 l of ground water (spike level, 50 ng/l) and 0.5 l of river water (spike level, 200 ng/l). Relative standard deviations ranged between 4.6 and 20% for drinking water, 4.3 and 15% for ground water, 5.9 and 13% for river water. Method detection limits calculated for drinking water, groundwater and surface water were between 3 and 11, 6 and 21, 36 and 75 ng/l, respectively.

Rapid determination of simazine and atrazine in water at the parts per trillion (1012) level : Extraction by a miniaturized carbopack B trap followed by high-performance liquid chromatography

A rapid and simple method for the determination of trace amounts of simazine and atrazine in water is described. A 250-ml volume of water is pre-concentrated by passage at a flow-rate of about 30 ml/min through a small trap containing 50 mg of graphitized carbon black (Carbopack B). After washing with 150 microliters of methanol, the two herbicides are desorbed with 700 microliters of dichloromethane-methanol (60:40, v/v). After removal, of the solvent, the extracted sample is fractionated and analysed by reversed-phase high-performance liquid chromatography with UV detection at 220 nm. A single assay can be completed within 40 min from the receipt of the water sample. Recoveries of simazine and atrazine added to 250 ml of water at the level of 50 ng/l were 97.2 and 95.8% and the limits of detection were 0.07 and 0.15 ng. respectively. At the 50 ng/l level in water, the coefficients of variation for simazine and atrazine were 3.7 and 4.0% (n = 7), respectively.