APCI surface water

Applications With the current use of soft ionisation techniques in LC-MS, i.e. ESI and APCI, the application of MS/MS is almost obligatory for confirmatory purposes. However, an alternative mass-spectrometric strategy may be based on the use of oaToF-MS, which enables accurate mass determination at 5 ppm. This allows calculation of the elemental composition of an unknown analyte. In combination with retention time data, UV spectra and the isotope pattern in the mass spectrum, this should permit straightforward identification of unknown analytes. Hogenboom et al. [132] used such an approach for identification and confirmation of analytes by means of on-line SPE-LC-ESI-oaToFMS. Off-line SPE-LC-APCI-MS has been used to determine fluorescence whitening agents (FWAs) in surface waters of a Catalan industrialised area [138]. Similarly, Alonso et al. [139] used off-line SPE-LC-DAD-ISP-MS for the analysis of industrial textile waters. SPE functions here mainly as a preconcentration device. 

In one study, however, atmospheric pressure chemical ionisation (APCI)-MS was applied for the simultaneous determination of LAS and octylphenol ethoxylates (OPEO) in surface waters after preconcentration by solid-phase extraction (SPE) on Cis cartridges [1]. In the chromatogram from a Ci-reversed phase (RP) column, peaks arising from both the anionic LAS and the non-ionic OPEO were detected after positive ionisation, while in negative ionisation mode, OPEO were discriminated and only the anionic surfactant was observed. Surprisingly, the relative sensitivity for detection of LAS was approximately five times higher in positive ion mode, which led the authors to the conclusion that this ionisation mode was desirable for quantitative work. 

Gardinali PR, Zhao X. 2002. Trace determination of caffeine in surface water samples by liquid chromatography-atmospheric pressure chemical ionization-mass spectrometry (LC-APCI-MS). Environ Int 28 521. 

Lopez de Alda and Barcelo [14] reported the determination of natural and synthetic estrogens and progestogens in influents and effluents from a sewage treatment plant (STP), surface water, and drinking water. The estrogens were determined as [M-H] in negative-ion ESI, the progestogens as [M-i-Na] in positive-ion mode ESI or APCI. Detection limits of <1 ng/1 water have been achieved. 

The analyses of environmental samples confirmed the ubiquitious presence of surfactants in surface and sea water as a result of the surfactants discharged with STP effluents. Analysis of River Elbe (Germany) water samples by GC-MS and APCl-LC-MS and MS/MS confirmed qualitatively the presence of nonpolar and polar organic pollutants of AEO, NPEO, CDEA and aromatic sulfonic acid type, respectively [226], After Cjg and/or SAX SPE anionic and non-ionic surfactants were qualitatively and quantitatively analysed in surface water samples by APCI-LC-MS in the negative or positive mode, respectively. Alkylphenol ethoxylates (APEOs) could be confirmed in river water at levels of 5.6 pg L [331]. 

Surface water samples from Southeastern regions of France and from the St. Lawrence River in Canada were monitored by APCI-LC-MS and MS/MS in the positive mode. Diuron and isoproturon were confirmed by MS/MS. Results obtained by LC-MS and ion trap LC-MS/MS were found to be comparable [374]. A substance-specific robust APCI-LC-MS/MS method using short columns for trace analysis of phenylureas was elaborated and vaUdated. Despite the low quantity of sample applied (15 mL) detection limits of < 5 pg L in full-scan and < 750 ng L in SIM mode, respectively, could be achieved. Product ion spectra were obtained from [M-i-H] parent ions and by means of a pesticide MS/MS Hbrary... 

A number of LC—MS/MS based methods have been developed for their trace analysis in environmental samples. For water analysis, LC—ESI—MS/MS is the technique of choice however, in recent studies, UHPLC separation and APCI ionization has become increasingly popular. Pedrouzo et al. [78] developed a new UHPLC—MS/MS method using solventless stir-bar sorptive extraction to investigate four UV filters, dihydroxy methoxybenzophenone (DHMB), benzophenone-3 (BP-3), octocrylene (OC), and ethylhexyl dimethyl-aminobenzoate (OD-PABA) in surface water and wastewater. Detection limits of 2.5 ng/1 and 10 ng/1, respectively, were achieved. Recently, Wick, Fink, and Temes combined LC—ESI—MS/MS and LC—APCI—MS/MS after SPE extraction for the determination of five UV filters in wastewater and surface water [79]. Quantification limits achieved ranged from 0.5 to 5 ng/I and 2.5 to 50 ng/I in surface water and wastewater, respectively. An innovative method, more simple and rapid, based on the direct analysis of the surface of a polydimethylsiloxane-coated stir bar previously used to extract the UV filters from water was developed by Flaunschmidt et al. [80]. With this direct analysis in real time (DART) —MS method, seven UV filters were... 

The mobile phases used to provide separations that interface cleanly with the MS are of great importance. Both isocratic and gradient elution can be used. High purity (HPLC grade) water, acetonitrile, and Ci to C4 alcohols are compatible with APTelectrospray and APCI. Less polar solvents such as hexane, cyclohexane, toluene, and ethyl acetate are also compatible with APCI. In general, it is advisable to always have an organic solvent present in the mobile phase to reduce surface tension, which enhances the formation of smaller, more uniform droplets and also aids vaporization and ionization and hence provides greater sensitivity. 

P.G.M. Kienhuis, R.B. Geerdink, LC-MS-MS analysis of surface and waste water with APCI, Trends Anal Chem, 19 (2000) 249 and 460. 

To optimize the whole analytical procedure, extraction and detection SPE and ESI-LC-MS and MS/MS were studied with polar pesticides hke atrazine and some of their transformation products such as deisopropylatrazine, hydroxyatra-zine and deethylatrazine. Detection hmits in surface and estuarine water were in the range 0.2 to 8 ng L . [536]. The apphcation of ESI and APCI developed as tech-... 

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