A very sensitive and specific analytical procedure for determining nonionic polyethoxylate surfactants, such as aliphatic ethoxylate alcohols (AEOs) and nonylphenol polyethoxylates (NPEOs), in aqueous environmental samples using electrospray liquid chromatography/mass spectrometry is presented, This procedure involves passing 10, 100, 1000, and 4000 mt of raw sewage, treated sewage, river water, and drinking water samples,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 isolating AEOs and NPEOs from both surfactants and biointermediates acidic in nature by differential elution, Recoveries of the analytes ranged between 85 and 97%, irrespective of the aqueous matrix in which they were dissolved. Chromatography was adjusted for eluting all the oligomers of NPEO and of the various AEO homologues as single peaks, This chromatographic condition enhances detection levels and simplifies quantification of the analytes. The limit of detection (signal-to-noise ratio = 3) was estimated to be about 20 pg/component injected into the column or 0.6, 0.02, 0.002, and 0.0002 mu g/L of each analyte in the influents and effluents of sewage treatment plants, river water, and drinking water, respectively, This procedure was employed for assessing the concentrations of the analytes in seven influent and seven effluent samples of three mechanical-biological treatment plants, The analysis of a municipal water sample revealed the presence of the analytes at parts-per-trillion levels

A very sensitive and specific analytical procedure for determining 20 acidic pesticides in aqueous environmental samples using pneumatically assisted electrospray (ES) LC/MS is presented. This procedure involves passing 1-and 4-L river water and drinking water samples, respectively, through a 1-g graphitized carbon black (GCB) extraction cartridge. By exploiting the presence of positively charged active centers on the GCB surface, isolation of the acidic pesticides from base/neutral species was made possible by differential elution. Recoveries of the analytes were higher than 85%, irrespective of the aqueous matrix in which they were dissolved. Adoption of the ion pair technique by addition of 0.1 mmol/L K2HPO4 and 0.2 mmol/L tetrabutylammonium fluoride to the mobile phase allowed analytes to be analyzed as preformed ions. A conventional 4.6-mm-i.d. reversed-phase LC C-18 column operating with a 1 mL/min flow of the mobile phase was used for chromatographing the analytes. A flow of 30 μL/min of the column effluent was diverted to the ES source, while the rest of the mobile phase was delivered to a UV detector set at 220-nm wavelength. The effects of the nature of the ion pair forming agent and its counterion as well as its concentration in the mobile phase on the response of the ES/MS detector were investigated. The effects of varying the skimmer cone voltage on the production of diagnostic fragments and the response of the MS detector were also evaluated. For the analytes considered, the response of the mass detector was linearly related to the amount of the analytes injected between 2.5 and 200 ng. A certain variation of the ion signal for the analytes considered occurred after several hours of continuous use of the LC/ES/MS instrumentation. For routine use, then, analyte quantitation could be better performed by the UV trace method while entrusting unambiguous identification of the analytes to the MS detector. The limits of sensitivity (signal-to-noise ratio = 3) of the method for the pesticides considered in drinking water and surface water samples were estimated to be about 2-6 and 8-25 ng/L, respectively

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The aim of metabolic untargeted profiling is to detect and identify unknown compounds in a biological matrix to achieve the most comprehensive metabolic coverage. In phytochemical mixtures, however, the complexity of the sample could present significant difficulties in compound identification. In this case, the optimization of both the chromatographic and the mass-spectrometric conditions is supposed to be crucial for the detection and identification of the largest number of compounds. In this work, a systematic investigation of different chromatographic and mass-spectrometric conditions is presented to achieve a comprehensive untargeted profiling of a strawberry extract (Fragaria × ananassa). To fulfill this aim, an ultra-high-pressure liquid chromatography system coupled via an electrospray source to a hybrid quadrupole-Orbitrap mass spectrometer was used. Spectra were acquired in data-dependent mode, and several parameters were investigated to acquire the largest possible number of both mass spectrometry (MS) features and MS mass spectra for unique metabolites. The main classes of polyphenols studied were flavonoids, phenolic acids, dihydrochalcones, ellagitannins, and proanthocyanidins. Method optimization allowed to us identify and tentatively identify 18 and 113 compounds, respectively, among which 74 have never been reported before in strawberries and, to the best of our knowledge, 22 of them have never been reported before. The results show the importance of an extended investigation of the chromatographic and mass-spectrometric method before a complete untargeted profiling of complex phytochemical mixtures.