Diversity of free-living marine nematodes (Enoplida) from Baja California assessed by integrative taxonomy

We used morphological and molecular approaches to evaluate the diversity of free-living marine nematodes (order Enoplida) at four coastal sites in the Gulf of California and three on the Pacific coast of Baja California, Mexico. We identified 22 morphological species belonging to six families, of which Thoracostomopsidae and Oncholaimidae were the most diverse. The genus Mesacanthion (Thoracostomopsidae) was the most widespread and diverse. Five allopatric species, genetically and morphologically differentiated, were found in two localities in the Gulf of California (M. sp1 and M. sp2) and three in the Pacific coast (M. sp3, M. sp4 and M. sp5). Overall, we produced 19 and 20 sequences for the 18S and 28S genes, respectively. Neither gene displayed intraspecific polymorphisms, which allowed us to establish that some morphological variation was likely either ontogenetic or due to phenotypic plasticity. Although 18S and 28S phylogenies were topologically congruent (incongruence length difference test, P > 0.05), divergences between species were much higher in the 28S gene. Moreover, this gene possessed a stronger phylogenetic signal to resolve relationships involving Rhabdodemania and Bathylaimus. On the other hand, the close relationship of Pareurystomina (Enchilidiidae) with oncholaimids warrants further study. The 28S sequences (D2D3 domain) may be better suited for DNA barcoding of marine nematodes than those from the 18S rDNA, particularly for differentiating closely related or cryptic species. Finally, our results underline the relevance of adopting an integrative approach encompassing morphological and molecular analyses to improve the assessment of marine nematode diversity and advance their taxonomy.

Direct Solid-Phase Optical Measurements in Flow Systems: A Review

Measurements based on absorption, reflectance, or luminescence of molecular species or complex ions can be carried out directly on a solid support simultaneously to the retention of the analyte. The use of this strategy in flow-based systems is advantageous in view of the reproducible handling of solutions in retention and elution steps of the analyte. This approach can be exploited to increase sensitivity, minimize reagent consumption as well as waste generation, improve selectivity or for simultaneous determination based on selective retention or differences in sorption rates of the analytes. This review focuses on the main characteristics of direct solid-phase measurements in flow systems, including the discussion of advantages and limitations and practical guidelines to the successful implementation of this approach. Selected applications in diverse fields, such as pharmaceutical, food, and environmental analysis are discussed.

Exploitation of a single interface flow system for on-line aqueous biphasic extraction

The exploitation of aqueous biphasic extraction is proposed for the first time in flow analysis This extraction strategy stands out for being environmentally attractive since it is based in the utilization of two immiscible phases that are intrinsically aqueous The organic solvents of the traditional liquid-liquid extractions ale no longer used, being replaced by non-toxic, non-flammable and non-volatile ones. A single interface flow analysis (SIFA) system was implemented to carry out the extraction process due to its favourable operational characteristics that include the high automation level and simplicity of operation, the establishment of a dynamic interface where the mass transfer occurred between the two immiscible aqueous phases, and the versatile control over the extraction process namely the extraction time The application selected to demonstrate the feasibility of SIFA to perform this aqueous biphasic extraction was the pre-concentration of lead. After extraction, lead reacted with 8-hydroxyquinoline-5-sulfonic acid and the resulting product was determined by a fluorimetric detector included in the flow manifold. Therefore, the SIFA single interface was used both as extraction (enrichment) and reaction interface. (C) 2010 Elsevier B.V All rights reserved.

Downscaling a multicommuted flow injection analysis system for the photometric determination of iodate in table salt

In this work a downscaled multicommuted flow injection analysis setup for photometric determination is described. The setup consists of a flow system module and a LED based photometer, with a total internal volume of about 170 mu L The system was tested by developing an analytical procedure for the photometric determination of iodate in table salt using N,N-diethyl-henylenediamine (DPD) as the chromogenic reagent. Accuracy was accessed by applying the paired r-test between results obtained using the proposed procedure and a reference method, and no significant difference at the 95% confidence level was observed. Other profitable features, such as a low reagent consumption of 7.3 mu g DPD per determination: a linear response ranging from 0.1 up to 3.0 m IO(3)(-), a relative standard deviation of 0.9% (n = 11) for samples containing 0.5 m IO(3)(-), a detection limit of 17 mu g L(-1) IO(3)(-), a sampling throughput of 117 determination per hour, and a waste generation 600 mu L per determination, were also achieved. (C) 2010 Elsevier B.V. All rights reserved.

A greener and highly sensitive flow-based procedure for carbaryl determination exploiting long pathlength spectrophotometry and photochemical waste degradation

An environmentally friendly analytical procedure with high sensitivity for determination of carbaryl pesticide in natural waters was developed. The flow system was designed with solenoid micro-pumps in order to improve mixing conditions and minimize reagent consumption as well as waste generation. A long pathlength (100 cm) flow cell based on a liquid core waveguide (LCW) was employed to increase the sensitivity in detection of the indophenol formed from the reaction between carbaryl and p-aminophenol (PAP). A clean-up step based on cloud-point extraction was explored to remove the interfering organic matter, avoiding the use of toxic organic solvents. A linear response was observed within the range 5-200 mu g L(-1) and the detection limit, coefficient of variation and sampling rate were estimated as 1.7 mu g L(-1) (99.7% confidence level), 0.7% (n=20) and 55 determinations per hour, respectively. The reagents consumption was 1.9 mu g of PAP and 5.7 mu g of potassium metaperiodate, with volume of 2.6 mL of effluent per determination. The proposed procedure was selective for the determination of carbaryl, without interference from other carbamate pesticides. Recoveries within 84% and 104% were estimated for carbaryl spiked to water samples and the results obtained were also in agreement with those found by a batch spectrophotometric procedure at the 95% confidence level. The waste of the analytical procedure was treated with potassium persulphate and ultraviolet irradiation, yielding a colorless residue and a decrease of 94% of total organic carbon. In addition, the residue after treatment was not toxic for Vibrio fischeri bacteria. (c) 2010 Elsevier B.V. All rights reserved.

A flow-based procedure with solenoid micro-pumps for the spectrophotometric determination of uric acid in urine

The determination of uric acid in urine shows clinical importance, once it can be related to human organism dysfunctions, such as gout. An analytical procedure employing a multicommuted flow system was developed for the determination of uric acid in urine samples. Cu(II) ions are reduced by uric acid to Cu(I) that can be quantified by spectrophotometry in the presence of 2,2`-biquinoline 4,4`-dicarboxylic acid (BCA). The analytical response was linear between 10 and 100 mu mol L(-1) uric acid with a detection limit of 3.0 mu mol L(-1) (99.7% confidence level). Coefficient of variation of 1.2% and sampling rate of 150 determinations per hour were achieved. Per determination, 32 mu g of CuSO(4) and 200 mu g of BCA were consumed, generating 2.0 mL of waste. Recoveries from 91 to 112% were estimated and the results for 7 urine samples agreed with those obtained by the commercially available enzymatic kit for determination of uric acid. The procedure required 100-fold dilution of urine samples, minimizing sample consumption and interfering effects. In order to avoid the manual dilution step, on-line sample dilution was achieved by a simple system reconfiguration attaining a sampling rate of 95 h(-1). (C) 2009 Elsevier B.V. All rights reserved.

Single interface flow analysis with accuracy assessment

Single interface flow systems (SIFA) present some noteworthy advantages when compared to other flow systems, such as a simpler configuration, a more straightforward operation and control and an undemanding optimisation routine. Moreover, the plain reaction zone establishment, which relies strictly on the mutual inter-dispersion of the adjoining solutions, could be exploited to set up multiple sequential reaction schemes providing supplementary information regarding the species under determination. In this context, strategies for accuracy assessment could be favourably implemented. To this end, the sample could be processed by two quasi-independent analytical methods and the final result would be calculated after considering the two different methods. Intrinsically more precise and accurate results would be then gathered. In order to demonstrate the feasibility of the approach, a SIFA system with spectrophotometric detection was designed for the determination of lansoprazole in pharmaceutical formulations. Two reaction interfaces with two distinct pi-acceptors, chloranilic acid (CIA) and 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ) were implemented. Linear working concentration ranges between 2.71 x 10(-4) to 8.12 x 10(-4) mol L(-1) and 2.17 x 10(-4) to 8.12 x 10(-4) mol L(-1) were obtained for DDQ and CIA methods, respectively. When compared with the results furnished by the reference procedure, the results showed relative deviations lower than 2.7%. Furthermore. the repeatability was good, with r.s.d. lower than 3.8% and 4.7% for DDQ and CIA methods, respectively. Determination rate was about 30 h(-1). (C) 2009 Elsevier B.V. All rights reserved.

Exploiting pi-acceptors for the determination of thyroid hormones (T3 and T4) using a single interface flow system

A fully automated methodology was developed for the determination of the thyroid hormones levothyroxine (T4) and liothyronine (T3). The proposed method exploits the formation of highly coloured charge-transfer (CT) complexes between these compounds, acting as electron donors, and pi-acceptors such as chloranilic acid (CIA) and 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ). For automation of the analytical procedure a simple, fast and versatile single interface flow system (SIFA)was implemented guaranteeing a simplified performance optimisation, low maintenance and a cost-effective operation. Moreover, the single reaction interface assured a convenient and straightforward approach for implementing job`s method of continuous variations used to establish the stoichiometry of the formed CT complexes. Linear calibration plots for levothyroxine and liothyronine concentrations ranging from 5.0 x 10(-5) to 2.5 x 10(-4) mol L(-1) and 1.0 x 10(-5) to 1.0 x 10(-4) mol L(-1), respectively, were obtained, with good precision (R.S.D. <4.6% and <3.9%) and with a determination frequency of 26 h(-1) for both drugs. The results obtained for pharmaceutical formulations were statistically comparable to the declared hormone amount with relative deviations lower than 2.1%. The accuracy was confirmed by carrying out recovery studies, which furnished recovery values ranging from 96.3% to 103.7% for levothyroxine and 100.1% for liothyronine. (C) 2009 Elsevier B.V. All rights reserved.

Cadmium telluride nanocrystals as luminescent sensitizers in flow analysis

A fully automated multipumping flow system (MPFS) using water-soluble CdTe quantum dots (QD) as sensitizers is proposed for the chemiluminometric determination of the anti-diabetic drugs gliclazide and glipizide in pharmaceutical formulations. The nanocrystals acted as enhancers of the weak CL emission produced upon oxidation of sulphite by Ce(IV) in acidic medium, thus improving sensitivity and expanding the dynamical analytical concentration range. By interacting with the QD, the two analytes prevented their sensitizing effect yielding a chemiluminescence quenching of the Ce(IV)-SO(3)(2-)CdTe QD system. The pulsed flow inherent to MPFS assured a fast and efficient mixing of all solutions inside the flow cell, circumventing the need for a reaction coil and facilitating the monitoring of the short-lived generated chemiluminescent species. QD crystal size, concentration and spectral region for measurement were investigated. (C) 2011 Elsevier B.V. All rights reserved.

Single reaction interface flow system for chemiluminescent monitoring of mannitol based on its hydroxyl radical scavenger activity

A single reaction interface flow analysis (SIFA) system for the monitoring of mannitol in pharmaceutical formulations and human urine is presented. The developed approach takes advantage of the mannitol scavenger aptitude to inhibit the chemiluminescent reaction between luminol and myoglobin in the absence of H(2)O(2). The SIFA system facilitated the fully automation of the developed methodology, allowing the in-line reproducible handling of chemical species with a very short lifetime as is the case of the hydroxyl radical generated in the abovementioned luminol/myoglobin reaction. The proposed methodology allowed the determination of mannitol concentrations between 25 mmol L(-1) and 1 mol L(-1), with good precision (R.S.D. < 4.7%, n = 3) and a sampling frequency of about 60 h(-1). The procedure was applied to the determination of mannitol in pharmaceuticals and in human urine samples Without any pretreatment process. The results obtained for pharmaceutical formulations were statistically comparable to those provided by the reference method (R.D. < 4.6%); recoveries values obtained in the analysis of spiked urine samples (between 94.9 and 105.3% of the added amount) were also satisfactory. (C) 2008 Elsevier B.V. All rights reserved.

Liquid-liquid microextraction without phase separation in a multicommuted flow system for diltiazem determination in pharmaceuticals

Liquid-liquid microextraction without phase segmentation was implemented in a multicommuted flow system for determination of the anti-hypertensive diltiazem. The procedure was based on ion pair formation between the drug and the dye bromothymol blue at pH 3.5. The detection was performed without phase separation in a glass tube coupled to a fiber-optics spectrophotometer. The total volume of chloroform was reduced to 50 mu L in comparison with 10 mL consumed in batch. A linear response was observed between 9 and 120 mu mol L(-1), with a detection limit of 0.9 mu mol L(-1) (99.7% confidence level). The coefficient of variation (n = 10), sampling rate and extraction efficiency were estimated as 0.6%, 78 determinations per hour and 61%, respectively. About 30 mu g of bromothymol blue was consumed and the waste volume was 380 mu L per determination. The results for pharmaceutical samples agreed with those obtained by the reference procedure at the 95% confidence level. (C) 2011 Elsevier B.V. All rights reserved.

A critical evaluation of a long pathlength cell for flow-based spectrophotometric measurements

Coupling of a flow cell based on a liquid core waveguide (LCW) to flow systems for spectro photometric measurements was critically evaluated. Flow-based systems with and without chemical reactions were exploited to estimate the increase in analytical signal in comparison to those obtained with a conventional I cm cell under different experimental conditions. The Schlieren effect associated to intense concentration gradients in the sample zone was investigated with model solutions that do not absorb visible electromagnetic radiation. The effect of radiation scattering was lower than the expected by considering the increase in the optical path, being the magnitude of the perturbation up to 40% higher for the 100-cm LCW cell. Several alternatives for compensation of the Schlieren effect were experimentally investigated. The potentiality of the LCW for turbidimetric measurements and coupling to monosegmented flow analysis was also evaluated. (C) 2008 Elsevier B.V. All rights reserved.

Exploiting Mn(III)/EDTA complex in a flow system with solenoid micro-pumps coupled to long pathlength spectrophotometry for fast manganese determination

The formation of the Mn(III)/EDTA complex in a flow system with solenoid micro-pumps was exploited for fast manganese determination in freshwater. Manganese(II) was oxidized in a solid-phase reactor containing lead dioxide immobilized on polyester. Long pathlength spectrophotometry was exploited to increase sensitivity, aiming to reach the threshold limit established by environmental legislation. A linear response was observed from 25 to 1500 mu g L(-1), with a detection limit of 6 mu g L(-1) (99.7% confidence level). Sample throughput and coefficient of variation were 36 samples/h and 2.6% (n = 10), respectively. EDTA consumption and waste generation were estimated as 500 mu g and 3 mL per determination, respectively. The amount of Pb in the residue corresponds to 250 mu g per determination and a solid-phase reactor could be used for up to 1600 determinations. Adsorption in active charcoal avoided interferences caused by organic matter and the developed procedure was successfully applied for determination of manganese in freshwater samples. Results were in agreement with those attained by GFAAS at the 95% confidence level. (C) 2010 Elsevier B.V. All rights reserved.

A multicommuted flow system with solenoid micro-pumps for paraquat determination in natural waters

A flow system designed with solenoid micro-pumps is proposed for the determination of paraquat in natural waters. The procedure involves the reaction of paraquat with dehydroascorbic acid followed by spectrophotometric measurements. The proposed procedure minimizes the main drawbacks related to the standard chromatographic procedure and to flow analysis and manual methods with spectrophotometric detection based on the reaction with sodium dithionite, i.e. high solvent consumption and waste generation and low sampling rate for chromatography and high instability of the reagent in the spectrophotometric procedures. A home-made 10-cm optical-path flow cell was employed for improving sensitivity and detection limit. Linear response was observed for paraquat concentrations in the range 0.10-5.0 mg L-1. The detection limit (99.7% confidence level), sampling rate and coefficient of variation (n = 10) were estimated as 22 mu g L-1, 63 measurements per hour and 1.0%, respectively. Results of determination of paraquat in natural water samples were in agreement with those achieved by the chromatographic reference procedure at the 95% confidence level. (c) 2008 Elsevier B.V. All rights reserved.

An improved procedure for flow-based turbidimetric sulphate determination based on a liquid core waveguide and pulsed flows

An improved flow-based procedure is proposed for turbidimetric sulphate determination in waters. The flow system was designed with solenoid micro-pumps in order to improve mixing conditions and minimize reagent consumption as well as waste generation. Stable baselines were observed in view of the pulsed flow characteristic of the systems designed with solenoid micro-pumps, thus making the use of washing solutions unnecessary. The nucleation process was improved by stopping the flow prior to the measurement, thus avoiding the need of sulphate addition. When a 1-cm optical path flow cell was employed, linear response was achieved within 20-200 mg L(-1), described by the equation S = -0.0767 + 0.00438C (mg L(-1)), r = 0.999. The detection limit was estimated as 3 mg L(-1) at the 99.7% confidence level and the coefficient of variation was 2.4% (n = 20). The sampling rate was estimated as 33 determinations per hour. A long pathlength (100-cm) flow cell based on a liquid core waveguide was exploited to increase sensitivity in turbidimetry. Baseline drifts were avoided by a periodical washing step with EDTA in alkaline medium. Linear response was observed within 7-16 mg L(-1), described by the equation S = -0.865 + 0.132C (mg L(-1)), r = 0.999. The detection limit was estimated as 150 mu g L(-1) at the 99.7% confidence level and the coefficient of variation was 3.0% (n = 20). The sampling rate was estimated as 25 determinations per hour. The results obtained for freshwater and rain water samples were in agreement with those achieved by batch turbidimetry at the 95% confidence level. (C) 2008 Elsevier B.V All rights reserved.