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J Riu

Publications and source records attributed to J Riu.

8 recordsLinked to original sources
PubMed2001

LC-MS determination of linear alkylbenzene sulfonates and their carboxylic degradation products in influent and effluent water samples and sludges from sewage-treatment plants.

Linear alkylbenzene sulfonates (LAS) have been determined in samples of the influent and the effluent, and in the sludge, from sewage-treatment plants (STP). LAS and sulfophenyl carboxylate compounds (SPC) were isolated by solid-phase extraction (SPE) with the polymeric phase Isolute ENV, then determined by liquid chromatography-electrospray mass spectrometry (LC-ESI-MS). The method enabled unequivocal identification of C10-C13 LAS by monitoring the ion at m/z 183 and the base peak corresponding to the [M-H]- ion. Average recoveries varied from 77-93% and the linear range of the method varied from 0.2 to 10 microg L(-1), with a limit of detection ranging from 10 ng L(-1) to 1.5 microg L(-1) when 200 mL waste water were preconcentrated. For sewage sludge, recoveries varied from 58 to 90% and the linear range was between 0.2 and 100 microg L(-1), with a detection limit ranging from 0.4 to 120 microg kg(-1) when 2.5 g sewage sludge was extracted. Unequivocal identification and determination of some metabolites of the LAS, the sulfophenyl carboxylate compounds (SPC), was achieved by monitoring [M-H]- ions.

Alkanesulfonic Acids↗
PubMed2001

Robust linear regression taking into account errors in the predictor and response variables.

We developed a robust regression technique that is a generalization of the least median of squares (LMS) technique to the field in which the errors in both the predictor and the response variables are taken into account. This simple generalization is limited in the sense that the resulting straight line is found by using only two points from the initial data set. In this way a simulation step is added by using the Monte Carlo method to generate the best robust regression line. We call this new technique 'bivariate least median of squares' (BLMS), following the notation of the LMS method. We checked the robustness of the new regression technique by calculating its breakdown point, which was 50%. This confirms the robustness of the BLMS regression line. In order to show its applicability to the chemical field we tested it on simulated data sets and real data sets with outliers. The BLMS robust regression line was not affected by many types of outlying points in the data sets.

Journal Article↗
PubMed2001

Determination of linear alkylbenzene sulfonates and their polar carboxylic degradation products in sewage treatment plants by automated solid-phase extraction followed by capillary electrophoresis-mass spectrometry.

Linear alkylbenzene sulfonates (LAS) were determined by solid-phase extraction (SPE), followed by capillary electrophoresis and mass spectrometry detection (CE-MS). The linear range of the proposed method varied from 33 to 316 and from 215 to 2057 micrograms L-1, depending on the compound, with limits of detection ranging from 4.4 to 23 micrograms L-1 when 200 ml of wastewater were preconcentrated. The analysis and confirmation of the polar carboxylic metabolites of LAS, the sulfophenyl carboxylic acids (SPC) was also achieved, and their presence was detected in both, influent and effluents of the sewage treatment plant (STP). [M - H]- ions were used for CE-MS confirmation and quantification. CE-MS diagnostic ions were the same ones used in LC-electrospray (ESI)-MS and corresponded to m/z 297, 311, 325 and 339 for C10LAS, C11LAS, C12LAS and C13LAS, respectively. For SPC identification, diagnostic ions corresponded to m/z 215 to 369 (with 14 mass unit steps) for C2 to C13SPC, respectively. LAS were determined in wastewater samples of the influent and effluent of three sewage treatment plants (STP), two of them using biological treatment with secondary settlement and receiving mainly domestic wastewater whereas one of the plants was operated with physiochemical treatment and received mainly industrial wastewater. The concentration levels of total LAS varied from 1000 to 1900 micrograms L-1 in the influents of STP, whereas in the effluents the concentrations varied from 125 to 360 micrograms L-1.

Journal Article↗
PubMed2001

Identification of surfactant degradation products as toxic organic compounds present in sewage sludge.

A cost-effective strategy combining chemical analysis and bioassays for the identification of polar toxic compounds in sewage sludge is reported. ToxAlert 100 bioluminescence inhibition assay was used in combination with chemical analysis involving extraction, clean-up, chromatographic separation and mass spectrometry detection. This methodology was applied to real samples of sludge from three wastewater treatment plants (WWTP) located in Catalonia (Spain) during a 3 month period. In the first step, sewage sludge was lyophilized, treated by sonication with a mixture of methanol and chloroform and finally cleaned up using a sequential solid phase extraction (SSPE) with an octadecylsilica cartridge (C18) in series with a polymeric Lichrolut EN cartridge (Lic EN). In the second step, the toxicity of each fraction of the sludge sample was investigated using the ToxAlert 100. The unequivocal identification and quantification of polar organic cytotoxic substances present in the fractionated extracts were determined by liquid chromatography-mass spectrometry (LC-MS). Major toxic compounds identified were: non-ionic polyethoxylated surfactants (nonylphenol polyethoxylates, alcohol polyethoxylates), their intermediates (polyethylene glycol polyethoxylated, nonylphenol carboxylates and polyethoxylated alcohol carboxylates), linear alkylbenzenesulfonates and heavy metals. The toxic response (in terms of bioluminescence inhibition using ToxAlert 100), defined by the 50% effective concentration (EC50), and the toxicity units (TU) for every standard non-ionic surfactant were calculated. The results provided the identification of polar cytotoxic compounds as well as the evaluation of their contribution to the total toxicity observed in sewage sludge.

Biodegradation, Environmental↗
PubMed2000

Inter-laboratory comparison of liquid chromatographic techniques and enzyme-linked immunosorbent assay for the determination of surfactants in wastewaters.

Seven laboratories participated in an inter-laboratory comparison exercise within the framework of the PRISTINE, SANDRINE and INEXsPORT European Union Projects. Solid-phase extraction (SPE) methodologies were used for the extraction of target analytes from wastewaters. The analytical strategies were based on liquid chromatography (LC) coupled to mass spectrometric (MS) or to fluorescent (FL) detection in all cases with the exception of one laboratory using a test-tube enzyme-linked immunosorbent assay kit. Samples were spiked with the surfactants nonylphenolpolyglycol ether, coconut diethanolamide, linear alkylbenzene sulfonate, nonylphenolpolyglycol ether sulfate, alkylpolyglycol ether and secondary alkane sulfonate. After enrichment on previously conditioned SPE cartridges, the SPE cartridges were distributed among the participating laboratories without the information about the amount of spiked surfactants. In addition, SPE cartridges loaded with a real-world environmental sample containing a tannery wastewater were also analyzed. The results of the programme showed that SPE followed by LC-MS techniques are reliable for the surfactants determination at submicrogram to microgram per liter levels in wastewaters. Inter-laboratory precision values were calculated as the reproducibility relative standard deviation (RSD(R)) which was determined from the reproducibility standard deviation (sR) and the average concentration at a particular concentration level. When data from all laboratories were pooled, the RSD(R) values ranged from 5.1 to 28.3% for the determination of target analytes. The most accurate result corresponded to that given for linear alkylbenzene sulfonates. Taking into account that different methodologies were used (including non-chromatographic techniques) and the complexity of the samples analyzed, it can be considered that acceptable reproducibility values were obtained in this inter-laboratory study.

Chromatography, Liquid↗
PubMed2000

Determination of linear alkylbenzenesulfonates in wastewater treatment plants and coastal waters by automated solid-phase extraction followed by capillary electrophoresis-UV detection and confirmation by capillary electrophoresis-mass spectrometry.

Linear alkylbenzenesulfonates (LASs) were determined in wastewaters and coastal waters by solid-phase extraction, using two different sample preparation protocols depending on the sample treated, followed by capillary electrophoresis and ultraviolet detection (CE-UV). The linear range of the proposed method varied from 3 to 53 and from 25 to 495 microg/l, depending on the compound, with a limit of detection of 1 microg/l when 250 ml of coastal water was preconcentrated. [M-H]- ions were used for CE-MS confirmation after quantification by CE-UV. CE-MS diagnostic ions were the same ones used in LC-electrospray (ESI) MS and corresponded to m/z 297, 311, 325 and 339 for C10, C11, C12 and C13 LASs, respectively. LASs were determined in wastewater samples of the influent and effluent of three wastewater treatment plants (WWTPs), two of them using biological treatment with secondary settlement and receiving mainly domestic wastewaters whereas one of the plants was operated with physicochemical treatment and received mainly industrial wastewaters. LASs were also analyzed in two samples from coastal waters of the bay of Cadiz (Spain) receiving untreated domestic effluents. All samples were also analyzed by LC-ESI-MS and the results are compared with the CE-UV method developed in this work. The concentration levels of total LASs varied from 988 to 1309 microg/l in the influents of WWTPs, whereas in the effluents the concentrations varied from 136 to 197 microg/l. The levels of LASs in coastal wastewaters of the bay of Cadiz varied from 739 to 911 microg/l, indicating that the wastewaters discharged into the bay did not undergo any treatment at all.

Alkanesulfonic Acids↗
PubMed2000

Analysis of polar hydrophilic aromatic sulfonates in waste water treatment plants by CE/MS and LC/MS.

The present work describes the development and optimization of a capillary (zone) electrophoresis/mass spectrometric (CE/MS) analysis method for polar hydrophilic aromatic sulfonates (ASs). The compounds were detected by negative ion electrospray ionization (NIESI) and selected ion monitoring (SIM). In comparison with CE/UV, for CE/MS a lower-concentration volatile ammonium acetate buffer (5 mM) without organic modifier and a higher separation voltage were better suited for separation. Sensitivity of CE/MS was slightly better than for CF/UV, with the limit of detection (LOD) ranging between 0.1 and 0.4 mg l(-1). For verification of the CE/MS results, ASs were also analysed by ion-pair liquid chromatography/diode array UV detection coupled in series with electrospray mass spectrometry (IPC/DAD/ESI-MS). Real water samples of different waste water treatment plants (WWTPs) in Catalonia (NE Spain) were extracted by solid-phase extraction (SPE) with LiChrolut EN and analysed with CE/MS and LC/MS. ASs were found in influent and effluent water samples of the WWTPs in the microg l(-1) concentration range. LC/MS offered a higher separation efficiency and sensitivity than CE/MS. Therefore with LC/MS more compounds could be identified in the WWTPs. The persistency of the ASs was distinct: some compounds were well degraded during the water treatment process, while others were quite persistent.

Arylsulfonates↗