Tetrabutylammonium-Induced Coacervation in Vesicular Solutions of Alkyl Carboxylic Acids for the Extraction of Organic Compounds

The potential of the tetrabutylammonium-induced liquid-liquid-phase separation in alkyl carboxylic acid vesicular solutions for the extraction of organic compounds prior to liquid chromatography was examined for the first time. The behavior of the coacervates yielded from octanoic to oleic acids as a function of the pH and salts was investigated. The time required for phase separation depended on the length of the carboxylic acid alkyl chain and the experimental procedure (i.e., standing, sonication, centrifugation, stirring, etc.). Theoretical preconcentration factors were a function of both surfactant concentration and the length of the alkyl chain, and they greatly surpassed those obtained with other surfactant-mediated separations (e.g., surfactant-rich phases from dodecanesulfonic acid or Triton X-114). Parameters affecting the extraction efficiency were assessed. Analytes in a wide polarity/charge range, (e.g., PAHs, surfactants, chlorophenols, bisphenols, phthalates, herbicides, amines, dyes, and photographic developers) were extracted with high efficiencies on the basis of the different types of interactions that the vesicular coacervates can establish (i.e., hydrophobic and ionic interactions, hydrogen bonds, and formation of mixed aggregates). The coacervates were compatible with the chromatographic determination of analytes following UV or MS detection. Their suitability for working under real conditions was checked by applying them to the extraction of nonionic surfactants [alkylphenol ethoxylates (octyl and nonyl) and alcohol ethoxylates (C12-C16)] from raw and treated sewage and to river water samples. Analytes in the coacervate were separated and quantified by liquid chromatography-ion trap mass spectrometry. No cleanup steps were necessary. Recoveries of the target compounds in the environmental water samples ranged from 89 to 103%.

Determination of cationic surfactants in pharmaceuticals based on competitive aggregation in ternary amphiphile mixtures

The surfactant to dye binding degree (SDBD) method was extended for the first time to the determination of cationic amphiphiles. For this purpose, Cresyl Violet (CV) and sodium dodecylsulphate (SDS) were selected as dye and reactant surfactant, respectively. This chemical system was used for the determination of cationic surfactants in pharmaceuticals. The approach was based on the competition established between the dye and cationic analytes to form mixed aggregates with the anionic surfactant (SDS-CV and SDS-analyte), which resulted in an increase of the amount of SDS required to reach a given SDS-CV binding degree. The feasibility of the proposed method to determine quaternary ammonium surfactants belonging to different structural groups (alkyldimethylbenzylammonium chlorides, alkyltrimethylammonium bromides and alkylpyridinium chlorides) in a wide variety of pharmaceutical formulations (solutions, creams and powders) was proved. The analytical features of the SDBD method (versatility, high precision and selectivity, ruggedness, rapidity, simplicity and low cost) made it an advantageous alternative to the conventional methods used in cationic surfactant quality control.

Allogeneic stem cell transplantation in patients with myelodysplastic syndrome: outcome analysis according to the International Prognostic Scoring System

We determined the outcome of patients with myelodysplastic syndrome (MDS) and secondary acute myeloid leukemia (sAML) after allogeneic stem cell transplantation according to their international prognostic scoring system (IPSS) risk categories at diagnosis. A total of 11 females and 7 males, with a median age of 45 years, were transplanted. With a median follow-up of 60 months, the 6-year actuarial event-free survival (EFS) for Less Advanced (Low and Intermediate-1 risk IPSS) and Advanced (Intermediate-2 and High risk IPSS) MDS was 71.4% and 43.6%, respectively (p=0.002). We did not observe a difference in EFS depending on cytogenetics at diagnosis (good risk 53.8% Vs intermediate and high risk 53.3%, p=ns), neither on the type of conditioning regimen used (myeloablative 50% Vs reduced intensity 52.2%, p=ns). Our results support that IPSS score at diagnosis may be used to predict EFS in patients with MDS undergoing allogeneic SCT.

Supramolecular systems-based extraction-separation techniques coupled to mass spectrometry

The combination of supramolecular chemistry and MS has not only been fruitful in the field of gas-phase fundamental studies of host-guest complexes and supramolecular assemblies. Mass spectrometric analysis has also benefited from the ability of supramolecular systems to behave as pseudophases in which solutes partition from the bulk solvent phase. Supramolecular systems-based extraction and concentration schemes and separation techniques have been widely used in different fields of analytical chemistry and are ideally suited for coupling with MS. This review describes the present status of the application of supramolecular chemistry in mass spectrometric analysis and includes topics such as the use of coacervative liquid-liquid extraction and hemimicelle/admicelle-based SPE of organic compounds prior to chromatography and electrophoresis. It also discusses the recent advances in enantioselective analysis using CD in electrophoresis- and chromatography-MS. The potential and analytical challenges of these approaches in environmental and bioanalytical chemistry, where one can expect significant developments in the future, are outlined.

Transient elastography: a valid alternative to biopsy in patients with chronic liver disease

BACKGROUND

Transient elastography is a novel and non-invasive technique for the evaluation of fibrosis in chronic liver disease. Few studies that exist value the efficacy of transient elastography, mainly in hepatitis C virus-infected patients.

AIM

To evaluate the effectiveness, objectivity, reproducibility and safety of this technique.

METHODS

We included 103 consecutive patients who underwent a liver biopsy in the last 48 months with a wide spectrum of chronic liver diseases. Median stiffness value (expressed as kilopascals - kPa) was kept as representative of the liver elastic modulus. All biopsy specimens were analysed by the same pathologist according to the METAVIR scoring system.

RESULTS

Median value of stiffness in patients with mild or moderate fibrosis (FI and FII), and severe fibrosis or cirrhosis (FIII and FIV) was of 7, 4 +/- 5 and 16, 4 +/- 10 kPa, respectively, with a significant difference between them (P < 0.05). The areas under the receiver operating characteristic curves showed the optimal liver stiffness cut-off values for each group.

CONCLUSIONS

We found a positive correlation between the liver stiffness found by transient elastography and fibrosis stage on biopsy in all patients, independently of the liver disease aetiology. Transient elastography is an easy, quick to perform and safe non-invasive procedure, reliable for assessing liver fibrosis.

Determination of alkylphenols and alkylphenol carboxylates in wastewater and river samples by hemimicelle-based extraction and liquid chromatography–ion trap mass spectrometry

Sodium dodecyl sulfate (SDS)-coated alumina and cetylpyridinium chloride (CPC)-coated silica were investigated as new sorbents for the concentration of alkylphenol polyethoxylate (APE) biodegradation products from wastewater and river water samples. Octylphenol (OP), nonylphenol (NP), octylphenol carboxylic acid (OPC) and nonylphenol carboxylic acid (NPC) were quantitatively retained on both supramolecular sorbents on the basis of the formation of mixed hemimicelles and admicelles. SDS hemimicelles-based SPE was proposed for the extraction/concentration of the target compounds prior to their separation and quantitation by liquid chromatography/electrospray ionization in negative mode, ion trap mass spectrometry. No clean-up steps or evaporation of the eluent were required. The recovery of APE metabolites from sewage and river water ranged between 87 and 100%. Concentration factors of about 500, using sample volumes of 1 l, were achieved. Detection limits were between 75 and 193 ng/l. The approach developed was applied to the determination of alklylphenols and alkylphenol carboxylic acids in raw and treated sewage and river samples. The concentrations of APE metabolites found ranged between 0.8 and 78 microg/l.

Analysis of linear alkylbenzene sulfonate homologues in environmental water samples by mixed admicelle-based extraction and liquid chromatography/mass spectrometry

Hemimicelles and admicelles of cetyltrimethylammonium bromide (CTAB) and cetylpyridinium chloride (CPC), adsorbed onto silica, were tested as sorbents for the solid phase extraction (SPE) of linear alkylbenzene sulfonate (LAS) homologues from environmental water samples. LASs were quantitatively retained on both surfactants due to high hydrophobic and ionic interactions, which led to the formation of analyte-extractant mixed aggregates. Parameters affecting the SPE of LASs were optimised. Recoveries of analytes from wastewater influent and effluent and river water samples ranged between 86 and 110%. Combination of SPE with liquid chromatography/mass spectrometry provided detection limits for the different LAS homologues of about 4 ng L(-1). The precision of the method, expressed as relative standard deviation, ranged from 5 to 9%. The method was applied to the analysis of LASs in wastewater and river samples using sample volumes between 10 and 25 mL. The LAS concentrations found ranged from 9 to 503 microg L(-1). No cleaning step was required to get accurate results.

Pharmaceutical quality control of acid and neutral drugs based on competitive self-assembly in amphiphilic systems

An aggregation parameter-based methodology for determining acid and neutral drugs in pharmaceutical dosage forms is presented. The method is based on competitive self-assembly in ternary dye-surfactant-drug aqueous mixtures. Dyes bearing charge of opposite sign to that of surfactants bind to surfactant to form mixed dye-surfactant aggregates, which are monitored from changes in the spectra features of the dye. The drug competes with the dye to interact with the surfactant to form drug-surfactant aggregates, which results in a decrease in the surfactant to dye binding degree proportional to the drug concentration in the aqueous solution. Coomassie Brilliant Blue G (CBBG) and didodecyldimethylammonium bromide (DDABr) were the dye and surfactant reactant used, respectively. The suitability of the surfactant to dye binding degree (SDBD) method to determine drugs with very different molecular structure: propionic (flurbiprofen, ibuprofen, naproxen and ketoprofen) and acetic (diclofenac, felbinac and zomepirac) acids, indolines (indomethacin and sulindac), glycyrrhetinic acid derivatives (carbenoxolone and enoxolone), salicylates (diflunisal and phenyl salicylate), oxicams (meloxicam, piroxicam and tenoxicam), pyrazolones (phenylbutazone and sulfinpyrazone) and hydrocortisones (dexamethasone and prednisolone) has been proved. The proposed method was successfully applied to the determination of drugs in commercial formulates (effervescent granulates, tablets, suppositories, gels and blisters) with a minimum sample treatment (dilution of liquid samples and dissolution of solid samples).

Hemimicelle-based solid-phase extraction of estrogens from environmental water samples

Hemimicelles and admicelles of sodium dodecyl sulfate (SDS) on alumina and cetyltrimethyl ammonium bromide (CTAB) on silica were evaluated for the concentration and purification of the priority estrogens estrone (E(1)), 17beta-estradiol (E(2)) and ethynylestradiol (EE(2)) from sewage and river samples. Retention was based on analyte-sorbent hydrophobic and cation-pi interactions. Parameters affecting the SPE of estrogens on both types of sorbents were comparatively investigated. Adsolubilization was quantitative for SDS hemimicelles/admicelles and CTAB admicelles. SDS hemimicelle-coated alumina was the sorbent selected on the basis of the lower elution volume required and the higher sample flow rate allowed. Combination of estrogen adsolubilization-based SPE with liquid chromatography-diode array/fluorescence detection permitted the quantification of the target compounds with detection limits ranging from 20 to 100 ng l(-1). The relative standard deviation ranged from 3 to 8%. The approach developed was applied to the determination of estrogens in raw and treated sewage and river samples. The recovery found for estrogens in these environmental matrices was between 85 and 105%.

Rapidly-progressive liver failure secondary to melanoma infiltration

We describe the case of a 51-year-old man with a history of intraocular melanoma treated with radiotherapy 2 years previously. The patient was diagnosed with mild hypertransaminasemia that progressed to acute liver failure and death in a period of one month. Radiological investigations such as spiral computed tomography and abdominal ultrasonography failed to give an etiologic diagnosis. Autopsy revealed melanoma with diffuse infiltration of the hepatic parenchyma. Because diagnosis is usually delayed, the prognosis of intraocular melanoma is poor. In 40% of cases metastases are present at diagnosis, and the most frequently affected organ is the liver (93-95%). Presentation as acute liver failure can appear after a long disease-free period. For this reason, periodic laboratory tests and hepatic ultrasound examination are recommended in patients diagnosed with this malignancy.

Determination of bisphenols in sewage based on supramolecular solid-phase extraction/liquid chromatography/fluorimetry

Supramolecular sorbents (hemimicelles/admicelles) are proposed for the extraction/preconcentration of bisphenols from aqueous environmental samples prior to their liquid chromatography/fluorimetric determination. A comparative study on the use of cetyltrimethylammonium bromide (CTABr)-coated silica and sodium dodecyl sulphate (SDS)-coated gamma-alumina as sorbent materials, is presented. Bisphenol A (BPA) and bisphenol F (BPF) were quantitatively retained on CTABr admicelles. Addition of tetrabutylammonium chloride (TBAC) to water samples was required to completely retain bisphenols on SDS-gamma-alumina. Retention on both sorbents occurred through hydrophobic and pi-cation interactions between the quaternary ammonium head group of the cationic amphiphile (CTABr or TBAC) and the aromatic rings of the target analytes. TBAC-SDS-gamma-alumina was the sorbent selected for the SPE of bisphenols on the basis of the lower elution volume required (1 ml of methanol) and the greater breakthrough volume allowed (400 ml), which permitted to reach practical detection limits of 10 and 15 ng/l for BPF and BPA, respectively. The proposed method was used to quantify bisphenol A and bisphenol B in wastewater samples from four sewage treatment plants. Recoveries obtained ranged between about 99 and 105% for raw wastewater and between 96 and 106% for treated wastewater.

Stability of benzalkonium surfactants on hemimicelle-based solid-phase extraction cartridges

The capability of hemimicelle-based solid-phase extraction cartridges for the preservation of organic compounds after their concentration from water samples was investigated for the first time. The approach is illustrated by studying the stability of benzalkonium homologue (C12, C14 and C16) surfactants (BAS) on monolayers of dodecyl sulphate (SDS) hemimicelles formed on alumina. The stability study included storage of cartridges at room temperature, at 4 and -20 degrees C, during a period of up to 3 months. The influence of water matrix components was also investigated from parallel experiments using spiked distilled, river and wastewater samples. Complete recovery of BAS was obtained for all storage conditions tested. Recoveries were independent on the alkyl chain length of BAS homologues and water matrix. The SPE of BAS on the SDS hemimicelles had a strong stabilizing effect for the target compounds and their analysis can be accomplished after at least 3 months without the necessity of special storage conditions for cartridges. Because of the lack of data, an additional stability study was carried out for BAS in an aqueous matrix using traditional preservation methods such as acidification (pH 2)/refrigeration, addition of formaldehyde (5%)/refrigeration, and freezing (-20 degrees C). Only combination of chemical addition (e.g. nitric acid or formaldehyde)/refrigeration was found effective to preserve BAS in the short term (e.g. for a week), then losses up to 40% were observed for these target compounds after a month.

Determination of non-ionic polyethoxylated surfactants in wastewater and river water by mixed hemimicelle extraction and liquid chromatography–ion trap mass spectrometry

The capability of hemimicelles-based solid phase extraction (SPE)/liquid chromatography/atmospheric pressure chemical ionisation in positive mode, ion trap mass spectrometry (LC/(APCl+-IT)-MS) for the concentration, separation and quantitation of non-ionic surfactants has been investigated. Concentration was based on the formation of mixed aggregates of analytes [alkylphenol ethoxylates (APE, octyl and nonyl) and alkyl ethoxylates (AE, C12-C16)] with the anionic surfactant sodium dodecyl sulphate (SDS) that is adsorbed on alumina. Parameters affecting SPE were investigated on the basis that hemimicelles are dynamic entities in equilibrium with the aqueous phase. The performance of ion trap mass spectrometry for MS and MS/MS quantitation of non-ionic homologues was assessed. Recoveries of analytes from wastewater influent and effluent and river water samples ranged between 91 and 98% and were found independent on the length of the alkyl chain under the optimised conditions. Anionic surfactants did not interfere to the levels found in environmental samples. The detection limits ranged between 14 and 111 ng/l for wastewater influent, 10 and 40 for wastewater effluent and 4 and 35 for river water, after concentration of 250, 500 and 750 ml of sample, respectively. The approach was applied to the determination of AE and APE in influent and effluent samples from four wastewater treatment plants and four river samples. The concentrations of individual non-ionic surfactants found ranged between 0.3 and 373 microg/l.

Determination of aromatic hydrotropic drugs in pharmaceutical preparations by the surfactant-binding degree method

An aggregation parameter-based analytical approach, the surfactant-dye binding degree (SDBD) method, was used, for the first time, to determine aromatic hydrotropic compounds. The anionic dye Coomassie Brilliant Blue G (CBBG) was used as inductor of didodecyldimethylammonium bromide (DDABr) aggregates, whose formation was monitored from changes in the spectral features of the dye. Interactions between hydrotrope and DDABr molecules resulted in a decrease of the degree of binding of the cationic surfactant to CBBG, which was proportional to the concentration of hydrotrope in the aqueous solution. The CBBG-DDABr-hydrotrope chemical system was found to fit to the mathematical expression previously derived for the determination of amphiphilic compounds. The hydrotrope-surfactant bond strength determined the sensitivity achieved for the determination of hydrotropic compounds, which was highly dependent on the molecular structure of the analyte. The high precision (the relative standard deviation for 7 mg l(-1) of salicylic acid was 0.8%), rapidity (measurements were performed in a few minutes) and low cost (in both instrumentation and reactants) of the proposed method, made it especially suitable for quality control. The practical analytical applicability of the SDBD method for the control of hydrotropic drugs in pharmaceutical preparations was demonstrated by quantifying salicylic acid and acetyl salicylic acid in liquid (solutions) and solid (tablets, granulates, unguents, gels and creams) samples, which were directly analyzed after dissolution of the samples.

Determination of non-ionic polyethoxylated surfactants in sewage sludge by coacervative extraction and ion trap liquid chromatography-mass spectrometry

Alkylphenol polyethoxylates (APE, nonyl and octyl) and alcohol ethoxylates (AE, C12-C16) were analysed in sewage sludge by extraction with sodium dodecane sulphonate (SDoS), that undergoes coacervation under acid conditions, followed by quantitation with liquid chromatography/atmospheric pressure chemical ionisation ion/trap mass spectrometry, in positive ion mode. Coacervative extraction was optimised using an aged, fortified dehydrated sludge. Recoveries ranged from 78 to nearly 100% irrespective of the sludge matrix analysed. The method provided good agreement between the ethoxamer distribution of surfactants after extraction from sludge and that in the original surfactant. Detection limits for polyethoxylated surfactants in the sludge were 0.09-0.38 mg/kg. The procedure was used to assess the concentrations of APE and AE in activated and dehydrated sludge from two sewage treatment plants. Polyethoxylates were found in all samples in the concentration ranges 11-151, 100-138 and 23-141 mg/kg for octylphenol, nonylphenol and individual AE homologues, respectively. The method did not require clean-up or preconcentration steps.

Evaluation and Optimization of an On-Line Admicelle-Based Extraction-Liquid Chromatography Approach for the Analysis of Ionic Organic Compounds

Admicelles-based solid-phase extraction (SPE) was on-line coupled with liquid chromatography/electrospray ionization/ion trap mass spectrometry, and it was proposed for the extraction of ionic organic compounds based on the formation of surfactant-analyte ion pairs. The approach was illustrated by studying the preconcentration of quaternary ammonium herbicides (quats) on sodium dodecyl sulfate (SDS) admicelles produced on alumina. Optimization of the parameters affecting SPE were studied on the basis that admicelles are dynamic entities in equilibrium with the aqueous phase. Some general guidelines could be established for method development from the results obtained. Factors influencing on-line operation were elucidated. On-line regeneration of the sorbent in each run was easily achieved by disruption of SDS admicelles with methanol and posterior coating of the alumina with SDS. The recovery of quats from drinking water samples were found quantitative for paraquat, diquat, and difenzoquat and above to 70% for chlormequat and mepiquat. Concentration factors of about 250, using sample volumes of 50 mL, were achieved. The detection limits ranged from 10 to 30 ng/L. The approach developed permits compliance with the directives of the European Community for drinking waters (100 ng/L) and goes deeply into the basis of solid-phase extractions that use surfactant-coated mineral oxide as sorbents.

Differentiation and quantification of linear alkyl benzenesulfonate isomers by liquid chromatography-ion-trap mass spectrometry

Discrimination and quantitation of the 20 positional isomers of C10-C13 linear alkyl benzenesulfonates (LASs), based on the use of reversed-phase liquid chromatography-electrospray ionisation in negative ion mode ion-trap mass spectrometry, was undertaken. Discrimination was achieved by LAS MS-MS analysis into the ion trap, by monitoring specific fragment ions resulting from the benzylic cleavage of the carbon alkyl chain on both side of the LAS phenyl group. Parameters affecting the electrospray ionisation source and the ion-trap operation were optimised. Calibration curves for the different isomers were established and this permitted their quantitation by mass spectrometry for the first time. MS-MS responses were dependent on both the position of the phenyl group on the alkyl chain and the length of this alkyl chain, these responses being higher for the external isomers and the longer alkyl chain homologues. The precision, expressed as relative standard deviation ranged between 9 and 13%. Detection limits for LAS isomers were between 0.03 and 0.07 mg/l and therefore the method is sensitive enough to be applied to environmental samples.

Potential of coacervation processes for the extraction of amphiphiles (linear alkyl benzenesulphonates) from sewage sludge samples prior to liquid chromatography

A new approach was developed for the monitoring of linear alkyl (C10-C13) benzenesulphonates (LASs) in sewage sludge. It was based on their extraction with the anionic surfactant sodium dodecanesulphonate (SDoS) that undergoes coacervation under acid conditions. The target compounds formed mixed aggregates with SDoS by ideal hydrophobic interactions which made possible the breakdown of LAS-sludge interactions and provided high extraction yields. Variables affecting extraction were optimised using a fortified dehydrated sludge. Recoveries for LASs were found independent on the length of alkyl chain. Liquid chromatography-fluorimetry was used for separation and detection of LAS homologues. Detection limit for LAS in the sludge was 5 mg/kg. Concentration levels of total LASs in activated and dehydrated sludge collected from two different sewage treatment plants were in the range 0.26-0.56 g/kg with LAS homologues ranging from 29 to 223 mg/kg. The method did not require clean-up or preconcentration steps.

Ion trap LC/MS characterisation of toxic polar organic pollutants in colour photographic wastewaters and monitoring of their chemical degradation

Liquid chromatography/electrospray ionisation-ion trap mass spectrometry (LC/ESI-ITMS) with positive mode of operation was successfully applied to the characterisation of aromatic amines and chelating agents in colour photographic wastewaters. In addition to residual ingredients, monomers and dimers of sulphonated aromatic amines were the main toxic polar organic pollutants found. Oxidation of wastewater components by the Fenton-like reagent (Fe3+ + H2O2) was investigated by continuously pumping a solution of hydrogen peroxide. Iron concentration, present in the wastewater as ferric carboxylate complexes, was typically above 1 g l(-1), and therefore addition of Fe3+ was not necessary for treatment. Operating variables like reagent feeding concentration and flowrate, temperature and pH were studied. The overall chemical oxygen demand (COD) removal reached 90% after 7.5 h of treatment when the dosage of hydrogen peroxide was 230 g per litre of effluent, the pH was about 4 and the temperature was 60 degrees C. The absence of toxics in the treated effluents was confirmed by the Photobacterium phosphoreum luminescence reduction test. Monitoring of the chemical degradation of aromatic amines and chelating agents by LC/ESI-ITMS proved that the Fenton's like reagent was effective in degrading them. Propylenediamine tetraacetic acid (PDTA) was found to be the more recalcitrant compound, however about 97% of degradation was achieved after 7.5 hours of treatment.