Naphthalene Sulfonic Acid Research Articles

Preparation and photo-physical characterisation of nanocomposites obtained by intercalation and co-intercalation of organic chromophores into hydrotalcite-like compounds

Several chromophores with donor–acceptor properties and containing a carboxylic or sulfonic group [coumarin-3-carboxylic acid (3-CCA), 9-anthracenecarboxylic acid (9-ACA), 4-benzoylbenzoic acid (4-BBA) and 2-naphthalenesulfonic acid (2-NSA)] have been intercalated into Mg–Al hydrotalcite-like compounds, both via anion exchange procedures and by using the “memory effect” of the hydrotalcites. The obtained intercalation compounds have been characterised by X-ray diffractometry, thermal analysis and chemical composition. Data obtained indicate that the guest species are accommodated in the interlayer region as a monofilm of interdigitaded anions with the C–COO− or C–SO3− bond almost perpendicular to the layer plane. The pairs of chromophores investigated, 3-CCA–9-ACA and 4-BBA–2-NSA, can give rise to energy transfer processes because of the characteristics of their excited states. Co-intercalation of the above-mentioned pairs of chromophores has been achieved with different synthetic procedures. The mono-intercalated and co-intercalated systems were investigated by absorption and emission spectroscopy and by laser flash photolysis. The absorption spectrum of MgAl-9-ACA shows an unexpected band around 490 nm that was attributed to an aggregate. The fluorescence characteristics of the various co-intercalated samples depend on the excitation wavelength and on the preparation methods, which control the relative amounts of the two fluorophores in the interlayer region. In all the samples containing 9-ACA excitation around 500 nm generates an emission attributed to the anthracene aggregate. In mono-intercalated and co-intercalated samples, the fluorescence decays satisfactorily fit bi-exponential and tri-exponential functions, respectively. Laser flash photolysis experiments showed that excitation of the intercalated chromophores produces transients which can be attributed to the guest triplets and, in the case of co-intercalated 4-BBA–2-NSA composite, the probable occurrence of an energy transfer process.

Stability Constant of the EuCl2+ Complex in Several Ionic Strength Media

The stability constant of the EuCl2 + complex was determined in perchloric acid media at 0.2, 0.5, and 1.0 M ionic strength by means of a solvent extraction method with dinonyl naphthalene sulfonic acid at 30°C. The values for β1,Cl were: 2.1 ± 0.1, 1.45 ± 0.01, and 0.84 ± 0.07, respectively, for each of the media. The Bronsted–Guggenheim–Scatchard specific ion interaction theory (SIT) was applied to these data and to some literature data to calculate a β1,Cl of 23.9 at infinite dilution. The calculated specific ion interaction coefficient e for the pair EuCl2 +, ClO4− was 0.52. Species-distribution diagrams have been analyzed.

Synthesis and Antibacterial Activity of 2-Naphthalenesulfonic Acid Azolides

Synthesis and Antibacterial Activity of 2-Naphthalenesulfonic Acid Azolides

Development of generic liquid chromatography-mass spectrometry methods using experimental design

Standard approaches to development of liquid chromatography-mass spectrometry (LC-MS) methods, either ion-pairing or reversed-phase liquid chromatography, have been through trial and error or intentional variation of experimental factors. These approaches to method optimization fail to take into account interactions between experimental factors and therefore the results may not be optimal for the combination of experimental factors. Another approach to optimization is through the use of chemometrics. Chemometric approaches can be more efficient than trial and error or intentional variation because chemometrics make use of multivariate designs; experimental factors are varied simultaneously at the various levels. Therefore chemometrics can take into account interactions between factors. The goal of this study was to develop a generic ion-pair LC-MS method for the analysis of acidic compounds using a chemometric approach called design of experiments (DOE). Four acidic compounds which cover three classes of acidic functional groups: 1-naphthyl phosphate ( 1), 1-naphthalenesulfonic acid ( 2), 2-naphthalenesulfonic acid ( 3), and (1-naphthoxy)acetic acid ( 4) were used as model compounds to develop the generic method. This study illustrates that LC-MS conditions can be optimized efficiently with minimal amount of experimentation using a chemometric approach to experimental design.

Adsorption and corrosion inhibitive properties of some organic molecules on iron electrode in sulfuric acid

Adsorption and corrosion inhibitive properties of three different organic molecules: 2-naphthalenesulfonic acid, 2,7-naphthalenedisulfonic acid and 2-naphthol-3,6-disulfonic acid are investigated on Armco-iron electrode cathodically polarized, in 0.5 mol dm −3 H 2SO 4 solution. The examinations show that the three organic molecules behave as a cathodic corrosion inhibitors. The inhibitive efficiency, changes with the number of functional groups substituted on benzene ring and increases with concentration. The experimentally obtained adsorption isoterms follow the Frumkin equation [ θ/ n(1− θ) n ]exp(−2 aθ)= Bc and the best fit is obtained for n=2 (for 2-NSA) and n=3 (for 2,7-NDSA and 2N-3,6-DSA). The calculated values for the parameter a are 2.1–2.9 and Gibbs energies are 17–21 kJ mol −1. The adsorption rate constants are very small, proving that iron surface permanently changes due to the corrosion processes.

Redox behavior of polyaniline as influenced by aromatic sulphonate anions: cyclic voltammetry and molecular modeling

We have investigated the influence of aromatic sulphonate anions on the redox behavior of polyaniline (PANI) by doping PANI, synthesized from sulphuric acid, with p-toluene sulphonic acid (pTSA), naphthalene sulphonic acid (NSA) and 5-sulphosalicylic acid (5-SSA). The contribution arising exclusively due to the anions was evaluated by keeping the concentration and the pH of the dopant solution constant at a value of 0.1 M and 2 respectively. The three aromatic sulphonate anions influenced the redox behavior of PANI differently. For instance, in the presence of NSA anions, PANI prefers to be in the protonated leucoemeraldine form, whereas at the same pH, PANI in the presence of sulphate, 5-SSA or pTSA anions, prefers to be in the unprotonated leucoemeraldine form. Interestingly, the presence of NSA gave highest stability to PANI against degradation due to hydrolysis. In order to rationalise these observations, molecular modeling (MM) studies were conducted. Using the molecular mechanics method, the energy of interaction between the dopant anion and the various forms of the polymer, namely, the leuco, emeraldine base, emeraldine salt and pernigraniline were estimated in order to take into account any factors other than just the basicity of the anion (e.g. non-covalent bonding interactions) that could contribute to the redox behavior of PANI. We have tried, for the first time, to correlate the redox peak positions with the interaction energies. The results of MM studies on this system are in good agreement with our experiments.

Modeling of Phosphoric Acid Purification by Liquid-Liquid Extraction

Phosphoric acid is an important industrial chemical. It is mainly produced by the wet process which consists of an attack of the phosphate rock by sulphuric acid leading to a complex solution containing a large number of impurities such as metal ions like Fe 3+ , Al 3+ , Mg 2+ , Cd 2+ , etc, which can effectively be recovered by solvent extraction process. In this present work a model of the liquid-liquid extraction process is presented. It is mainly based on thermodynamics, where two different routes have been tested for the modeling of the complexation process. The method has been tested using a model system with Al 3+ as the contaminant, dodecyl naphthalene sulphonic acid (HDDNSA) as the complexing agent and kerosene as the diluent. The study has also investigated the influence of various parameters such as the pH of the aqueous phase and the initial concentration of the phosphoric acid.

Synthesis of β-cyclodextrin derivative bearing a cyclohexylamino moiety and its inclusion complexation with organic dye molecules

A novel β-cyclodextrin derivative bearing a cyclohexylamino moiety ( 3) was synthesized by reaction of cyclohexylamine with mono-[6- O-( p-tolylsulfonyl)]-β-cyclodextrin and its binding ability for 1:1 inclusion complexation with a series of naphthalene derivatives and AR was evaluated in phosphate buffer solution (pH=7.2, 0.1 mol dm −3) at 25°C by spectrofluormetric titrations. The results obtained indicate that the modification dramatically enhanced the original binding ability of natural β-cyclodextrin by a factor 2.52–28.4, except for 2-naphthalenesulfonic acid sodium (2-NS) and demonstrated that the pH values and salt intensity of the solution also directly influenced the molecular binding ability of the compound ( 3). The binding abilities and molecular selectivities of model substrates by modified β-cyclodextrin ( 3) are discussed from the viewpoints of size/shape-fit and geometry compensation between host cyclodextrins and guest dye molecules.

Adsorption of an anionic dispersant on lignite

Since coal is not a homogeneous substance but a mixture of carbonaceous materials and mineral matter, it has a variety of surface properties. Therefore, it is not easy to control the properties of coal suspensions by simply adjusting variables, such as pH and/or electrolyte. A chemical agent needs to be added to control the properties of the coal suspensions. The aim of this investigation is to determine the adsorption behavior of an anionic dispersant in the presence of a wetting agent using some Turkish lignite samples. The presence of a wetting agent in the dispersant adsorption behavior is important, since usage of a wetting agent in the preparation of coal–water slurries which are acceptable for potential industrial users is of great importance. The effects of dispersant concentration, temperature and pH on the dispersant adsorption were studied systematically, and the experimental results are presented. Pellupur B69 as a dispersant, commercial mixture of formaldehyde condensate sodium salt of naphthalene sulphonic acid, and Texapon N25 as a wetting agent, a sodium lauryl ether sulfate, have been used.

Electromagnetic interference shielding characteristics of fabric complexes coated with conductive polypyrrole and thermally evaporated Ag

Through the chemical coating of polypyrrole (PPy) doped with naphthalene sulfonic acid (NSA) on electrically insulating poly (ethylene terephthalate) (PET) woven fabric, PPy–NSA/PET complexes were synthesized. By using the electrochemical coating of PPy doped anthraquinone-2-sulfonic acid (AQSA) on PPy–NSA/PET complexes, PPy–AQSA/PPy–NSA/PET complexes were synthesized. The silver (Ag) was thermally vacuum evaporated on the surface of PPy–AQSA/PPy–NSA/PET complexes (Ag|PPy–AQSA/PPy–NSA/PET). Electromagnetic interference (EMI) shielding efficiency (SE) and dc conductivity (σdc) of fabric complexes were measured for EMI shielding characteristics and theoretical simulation. The measurement of EMI SE in the frequency range from 50 MHz to 1.5 GHz was performed by using ASTM D4935-99 method. The EMI shielding characteristics such as transmittance, reflectance and absorbance were obtained from the S (scattering)-parameter analysis. We control the contribution of the absorbance or the reflectance to total EMI SE through the coating of conductive PPy and the evaporation Ag.

Electrochemical Reduction of Benzaldehyde as its Girard-P Derivative at the Mercury Electrode and Differential-Pulse Polarographic Determination of Benzaldehyde

The polarographic behaviour of benzaldehyde as its Girard-P derivative was studied using various electrochemical techniques and a method for the determination of benzaldehyde (10−6 − 8 × 10−5 M) by differential-pulse polarography, based on the in situ formation of its Girard-P derivative in aqueous solution at pH 2.5, is proposed. The relative standard deviation was 1.7% (ten determinations at the 5 × 10−5 M level). The applicability of this method is checked in benzyl alcohol and synthetic samples containing, o-aminophenol, 2-amino pyridine, o-cresol, amylic alcohol, salicylic acid, 4-aminobenzoic acid and naphthalene sulfonic acid.

An investigation of some factors affecting the dispersant adsorption of lignite

To obtain commercially suitable coal–water slurry (CWS), usage of the appropriate type and amount of chemical additives is necessary from various points of view. Since the properties of coal change from one type to another, it is not possible to find an universal dispersing agent, which is acceptable for all types of coals. Examination of the adsorption behavior of the dispersant and the amount of dispersant which is really necessary to make coal particles disperse in water is very important because of the adverse effect of an excess amount of dispersant on the flow and sedimentation properties of CWS, and the high cost of dispersants. The main objective of our research is to represent how some factors, such as air-oxidation, demineralization, stirring speed, particle size distribution, concentration of slurry and addition stage of dispersant, affect the dispersant adsorption characteristic of formaldehyde condensate sodium salt of naphthalene sulfonic acid. These factors were investigated by using Turkish lignite samples and, consequently, the influence of these factors on the dispersant adsorption behavior was determined and discussed.

Determination of naphthalenesulfonic acid isomers by large-volume on-line derivatization and gas chromatography–mass spectrometry

This work presents a modified method to analyze polar and water-soluble naphthalene monosulfonic acid (NS) isomers in industrial effluents and river water samples. The method involves extraction of samples by a styrene–divinylbenzene copolymer solid-phase extraction cartridge, and on-line derivatization in the GC injection port using a large-volume (10 μl) sample injection with tetrabutylammonium salts. The analytes were then identified and quantitatively determined by GC–MS. The large-volume injection-port derivatization technique provides sensitivity, fast and reproducible results for NS isomers, to quantitation at 0.05 μg/l in 200 ml of water sample. Enhanced extracted mass chromatograms of molecular ion and [M−56] + ion of butylated NS isomers by electron impact ionization MS allows us to determine residues at trace levels in environmental samples. Recoveries of the NS isomers in spiked water samples ranged from 70 to 82% with RSDs around 10%. Naphthalene-2-sulfonic acid was found as a major pollutant and propagated in surface water and industrial effluents.

Protein structure information from mass spectrometry? Selective titration of arginine residues by sulfonates

Noncovalently bound complexes between basic sites of peptides/proteins and sulfonates are studied using Matrix Assisted Laser Desorption/Ionization (MALDI) Mass Spectrometry. Reactive sulfonate dyes such as Cibacron Blue F3G-A are known to bind to protonated amino groups on the exterior of a protein. In this work, we examine a wide range of other sulfonates with distinctly simpler structure and more predictable reactivity. Naphthalene-sulfonic acid derivatives were found to bind to arginine only, as opposed to expected binding to all basic sites (Arg, Lys and His). Detailed control experiments were designed to unambigously confirm this selectivity and to rule out nonspecific adduct formation in the gas phase. The data show that the number of complex adducts found equals the number of accessible arginine sites on the surface of folded peptides and proteins, plus the N-terminus. Lys and His are not complexed nor are buried residues with hindered access. MALDI-MS can therefore provide fast information related to the exposed surface of these biomolecules. Additional titration experiments with 1-anilino-naphthalene-8-sulfonic acid (ANS) revealed that this fluorescent dye, which was often hypothesized to bind to so-called molten globule states of proteins, behaved exactly like all other naphthalene-sulfonic acids. ANS binding thus occurs largely through the sulfonate group.

Conductivity and EMI shielding efficiency of polypyrrole and metal compounds coated on (non) woven fabrics

We synthesized polypyrrole (PPy) and metal (AgPd) compounds coated on woven polyethylene teraphthalate (PET) and nonwoven polyester (PE) fabrics. PPy coated on PET or PE fabrics was chemically polymerized by using naphthalene sulfonic acid (NSA) as a dopant and electrochemically synthesized by using anthraquinon-2-sulfonic acid (AQSA) as a dopant. Temperature dependences of de conductivity [σ dc (T)] of PPy-NSA/fabric and PPy-AQSA/fabric complexes are compared. The electromagnetic interference (EMI) shielding efficiency (SE) of PPy/fabric complexes is in the range of 20 ∼ 80 dB depending on the thickness and conductivity.

Electrical, magnetic, and structural properties of chemically and electrochemically synthesized polypyrroles

We report the results of temperature-dependent dc conductivity ( σ dc( T)), EPR (electron paramagnetic resonance) magnetic susceptibility, and XPS (X-ray photoelectron spectroscopy) experiments for chemically and electrochemically synthesized polypyrrole (PPy) samples. For chemically synthesized dodecylbenzenesulfonic acid (DBSA) or naphthalenesulfonic acid (NSA) doped PPy samples (PPy-DBSA or PPy-NSA, respectively) soluble in m-cresol solvent, dc conductivity and its temperature dependence show the strong localization behavior, while those of electrochemically synthesized PPy doped with hexafluorophosphate (PPy-PF 6) are in the critical regime. Pauli susceptibility ( χ p) and the density of states are obtained from the temperature dependence of EPR magnetic susceptibility. The density of states of chemically synthesized PPy is one-third of that of electrochemically synthesized PPy. From the analysis of the area ratio of carbon 1s XPS peak, the disorder effect due to interchain links or side chains of PPy-DBSA ( m-cresol) samples is ∼22%, while that of PPy-PF 6 samples is ∼33%. This result indicates that the percent of interchain links or side chains of chemically synthesized PPy-DBSA ( m-cresol) samples is reduced by ∼10% compared to that of electrochemically synthesized PPy-PF 6 samples. We analyze that the side chains or interchain links of chemically synthesized PPy samples are relatively reduced due to the synthesis method using large size dopants, and subsequently the interchain interaction weakens. The results of EPR experiments of PPy-DBSA ( m-cresol) samples with different doping levels are discussed.

Physical Characterization of Electrochemically and Chemically Synthesized Polypyrroles

The results of temperature-dependent dc conductivity, EPR magnetic susceptibility, and X-ray photoelectron spectroscopy (XPS) experiments are compared for electrochemically and chemically synthesized polypyrrole (PPy) samples. For chemically synthesized PPy samples soluble in organic solvent with large size dopants such as dodecylbenzenesulfonic acid (DBSA) or naphthalenesulfonic acid (NSA), dc conductivity (σdc) is ≤0.1 S/cm at room temperature, and its temperature dependence [σdc(T)] shows strong localization behavior, while σdc(T) of the electrochemically synthesized PPy samples doped with hexafluorophosphate (PF6) is in the critical or the metallic regime. The density of states of chemically prepared PPy−DBSA samples is less than one-fourth that of electrochemically synthesized PPy−PF6 samples. The g values and temperature dependence of the line width obtained from EPR experiments show that the paramagnetic signals in both electrochemically and chemically synthesized PPy samples are mainly due to the polarons in π-conjugated polymer chains. We observe the existence of one dopant per three pyrrole rings in PPy−DBSA and PPy−PF6 samples. From the XPS experiments, one-fifth of the pyrrole rings of chemically prepared PPy−DBSA are incorporated into interchain links or side chains, while for electrochemically prepared PPy−PF6, one-third of the pyrrole units are in side chains or cross-links. We analyze that the side chains or cross-links of chemically synthesized PPy samples are relatively reduced, and subsequently the interchain interaction weakens. For chemically synthesized PPy samples, the synthesis method using large size dopants is one of the important roles for the reduction of side chains or cross-links and for the increase of solubility. The weakness of the interchain interaction and the reduction of side chains or interchain links for PPy systems play an important role for charge transport.

Chemical synthesis and characterization of polypyrrole coated on porous membranes and its electrochemical stability

Microporous membranes coated with polypyrrole (PPy) are developed for electrodes in electrokinetic membrane separation processes. The fabrication method is based upon the oxidative chemical polymerization of pyrrole associated with the phase inversion principle, using an optional dopant (2-naphthalenesulfonic acid, NSA or p-toluenesulfonic acid, TSA) and FeCl 3 as an oxidant. The electrochemical properties of PPy films formed on various substrates such as a porous nylon filter, a silanized alumina membrane, a filter paper, and a track-etched polycarbonate membrane are characterized. For applications as membrane electrodes, the electrochemical stability of PPy-coated membranes is investigated under a potentiostat condition. The cyclic voltammograms (CV) in conjunction with conductivity measurements reveal the conductivity decay of PPy due to an anomalously high current density. A simple treatment with aq. 0.5 M H 2SO 4 at an elevated temperature improves the stability against aging time and electrochemical oxidation, showing an increase in the half life of conductivity during the aging experiments.

Endothelin-1 inactivating peptidase in the human kidney and urine.

Recently, an apparently novel, specific endothelin-1 inactivating metalloendopeptidase (ET-1 peptidase) has been isolated from the rat kidney. In this study we attempted to determine whether the same or a similar peptidase is present in the human kidney, and whether the enzyme is excreted into the urine. The urinary ET-1 peptidase could serve as an indirect index of the renal endothelin system, both in physiology and pathophysiology. Kidney specimens were obtained from part of nephrectomized kidneys unaffected by any neoplastic process from six adult patients. The enzyme was purified using differential centrifugation, detergent solubilization of the membrane proteins, ultrafiltration and nondenaturing gel electrophoresis. The enzyme activity assays were performed at pH 5.5 and 37 degrees C in the presence of increasing concentrations of unlabelled peptides and inhibitors using a fixed amount of [125I]ET-1 as substrate. The degradation extent was quantified with trichloroacetic acid precipitation and high performance liquid chromatography. The degrading activity of ET-1 was determined in urine samples from adult patients with hypertension, children with chronic renal failure and those with stable renal allograft ET-1 peptidase from the human kidney displays characteristics close to that of the rat ET-1 peptidase we have recently described (J. Hypertens 1994; 12:1155-1162). The enzyme, a membrane-bound metalloendopeptidase, exhibits low electro- phoretical mobility on nondenaturing gel (Rf 0.08); it is an apparently heterologous structure comprising three enzymatically inactive subunits, it has a pH optimum at 5.5, a nanomolar range affinity to the ET-1 (KM 180 nmol/l) that is hydrolysed to two main degradation products, and a 10-100-fold lower affinity to big ET-1 (KM 11.5 micromol/l), endothelin 11 21 fragment (KM 15.3 micromol/l), endothelin antagonist Trp-Leu-Asp-Ile-Ile-Trp (KM 3.1 micromol/I), gastrin (KM 2.2 micromol/l) and cholecystokinin (KM 4.0 micromol/l). Substance P, neuropeptide Y, atrial natriuretic peptide, bradykinin, angiotensin II and enkephalin were poor substrates for the enzyme. The most powerful inhibitors of the ET-1 peptidase included thiorphan (IC50 0.28 nmol/l), phosphoramidon (IC50 0.55 nmol/l), phenanthroline (IC50 11.5 micromol/l), cyclosporin (IC50 400 micromol/l), phosphate (IC50 1.2 mmol/l), citrate (IC50 0.6 mmol/l) and aniline naphthalene sulphonic acid (IC50 0.25 mmol/l). Our data suggest that three ET-1 degrading peptidases with optimal activity at pH 4.5, 5.5 and 7.0, respectively, are excreted into the urine. The enzyme with a pH optimum 4.5 is of lysosomal origin whereas the two other enzymes correspond by their pH optima to the renal ET-1 peptidase and neutral endopeptidase. We have found statistically significant increases (P < 0.001) in the activity of both lysosomal and ET-1 peptidase in the urine in patients with hypertension and in children with chronic renal failure compared with healthy subjects or children with stable renal allograft Human kidney contains an acidic, highly specific endothelin-1 inactivating metalloendopeptidase that may have a key role in the regulation of concentrations of renal and circulating endothelins. The enzyme is excreted into the urine where its activity seems to be increased in patients with hypertension and chronic renal failure; it may potentially serve as an indirect index of the renal endothelin system.

Tracing polar benzene- and naphthalenesulfonates in untreated industrial effluents and water treatment works by ion-pair chromatography-fluorescence and electrospray-mass spectrometry

This paper presents a protocol for the determination of a class of polar, ionic and highly water-soluble organic pollutants: benzene- and naphthalenesulfonic acids, compounds widely used in chemical, pharmaceutical, tannery, paper and textile industries. This protocol involves the use of a solid-phase extraction (SPE) followed by ion-pair chromatography-electrospray-mass spectrometry (IPC-ESI-MS). In this work two polymeric solid-phase extraction cartridges (Isolute ENV+ and Lichrolut EN) were compared, with the more effective being Isolute ENV+ sorbent. Recoveries and breakthrough volumes were calculated by loading volumes of 150, 200 and 300 ml of spiked ground water through the SPE columns. To enhance the effectiveness of the methodology, 1 ml of water containing 5 mM TEA was added before eluting with methanol. Average recoveries ranging from 70 to 100% were obtained for a variety of 13 analytes (only two naphthalenesulfonate compounds had recoveries below 50%.). Determination of benzene- and naphthalenesulfonates was accomplished by ion-pair chromatography-fluorescence detection (IPC-FLD). The ESI-MS parameters were optimized to achieve maximum sensitivity. [M–H] − ion was the base peak using low energies (fragmentor voltage: 80 V). Significant fragmentation of the quasi-molecular [M–H] − ion occurs at higher fragmentor voltages, leading to [M–SO 2H] −, [M–SO 3H] − and [SO 3] − as diagnostic ions, but with some sensitivity losses (more than two orders of magnitude when 150 V are applied as fragmentor voltage). Collision-induced dissociation (CID) of the parent ions for the benzene- and naphthalenesulfonates studied gave the [SO 3] − fragment ion common to sulfonated compounds, it has been shown to be characteristic of aromatic sulfonated compounds and could be used as a diagnostic tool to indicate the presence of these compounds. Limits of detection (signal-to-noise ratio = 3) ranging from 0.03 pg to 0.05 ng, were achieved when 150 ml of ground water were processed and quantified by IPC-FLD. In IPC-ESI-MS, time-scheduled SIM mode with post-column addition of 0.2 m min −1 of methanol was used. LODs range from 0.6 pg to 0.13 ng. In summary, with the development of a methodology based on SPE followed by IPC-ESI-MS, good sensitivity, structural information and unequivocal identification can be achieved. This protocol was applied to the analysis of surface waters, untreated industrial waste waters and wastewater treatment works effluents and influents. In the case of tannery effluent samples, isomers of naphthalenesulfonic acid were found as major pollutants in concentrations up to 0.8 and 1.0 mg l −1, for 1-naphthalenesulfonate and 2-naphthalenesulfonate, respectively. The main contaminants in wastewater treatment work samples were 2,6-naphthalenedisulfonate, 1-hydroxy-3,6-naphthalenedisulfonate, 3-nitrobenzenesulfonate, 1-naphthalenesulfonate and 2-naphthalenesulfonate, with levels of ug/l.