An environmentally friendly flow system for high-sensitivity spectrophotometric determination of free chlorine in natural waters

A green and highly sensitive analytical procedure was developed for the determination of free chlorine in natural waters, based on the reaction with N,N-diethyl-p-phenylenediamine (DPD). The flow system was designed with solenoid micro-pumps in order to improve mixing conditions by pulsed flows and to minimize reagent consumption as well as waste generation. A 100-cm optical path flow cell based on a liquid core waveguide was employed to increase sensitivity. A linear response was observed within the range 10.0 to 100.0 mu g L(-1), with the detection limit, coefficient of variation and sampling rate estimated as 6.8 mu g (99.7% confidence level), 0.9% (n = 20) and 60 determinations per hour, respectively. The consumption of the most toxic reagent (DPD) was reduced 20,000-fold and 30-fold in comparison to the batch method and flow injection with continuous reagent addition, respectively. The results for natural and tap water samples agreed with those obtained by the reference batch spectrophotometric procedure at the 95% confidence level. (C) 2010 Elsevier By. 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.

Sequential spectrofluorimetric determination of free and total glycerol in biodiesel in a multicommuted flow system

A new procedure for spectrofluorimetric determination of free and total glycerol in biodiesel samples is presented. It is based on the oxidation of glycerol by periodate, forming formaldehyde, which reacts with acetylacetone, producing the luminescent 3,5-diacetyl-1,4-dihydrolutidine. A flow system with solenoid micro-pumps is proposed for solution handling. Free glycerol was extracted off-line from biodiesel samples with water, and total glycerol was converted to free glycerol by saponification with sodium ethylate under sonication. For free glycerol, a linear response was observed from 5 to 70 mg L(-1) with a detection limit of 0.5 mg L(-1), which corresponds to 2 mg kg(-1) in biodiesel. The coefficient of variation was 0.9% (20 mg L(-1), n = 10). For total glycerol, samples were diluted on-line, and the linear response range was 25 to 300 mg L(-1). The detection limit was 1.4 mg L(-1) (2.8 mg kg(-1) in biodiesel) with a coefficient of variation of 1.4% (200 mg L(-1), n = 10). The sampling rate was ca. 35 samples h(-1) and the procedure was applied to determination of free and total glycerol in biodiesel samples from soybean, cottonseed, and castor beans.

Cloud point extraction and concentration of carbaryl from natural waters

An improved procedure is proposed for determination of the pesticide carbaryl in natural waters based on double cloud point extraction. The clean up step was carried out only with Triton X-114 in alkaline medium in order to avoid the use of toxic organic solvents as well as to minimise waste generation. Cloud point preconcentration of the product of the reaction of the analyte with p-aminophenol and cetyltrimethylammonium bromide was explored to increase sensitivity and improve the detection limit. Linear response was achieved within 10 and 500 mu g L-1 and the apparent molar absorptivity was estimated as 4.6 x 105 L mol-1 cm-1. The detection limit was estimated as 7 mu g L-1 at the 99.7% confidence level and the coefficient of variation was 3.4% (n = 8). Recoveries within 91 and 99% were estimated for carbaryl spiked water samples. The results obtained for natural water samples were in agreement with those achieved by the batch of spectrophotometric procedure at the 95% confidence level. The proposed procedure is then a simple, fast, inexpensive and greener alternative for carbaryl determination.

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 flow-cell based on a liquid core waveguide for chemiluminescence measurements

Liquid-core waveguides (LCWs), devices that constrain the emitted radiation minimizing losses during the transport, are an alternative to maximize the amount of detected radiation in luminescence. In this work, the performance of a LCW flow-cell was critically evaluated for chemiluminescence measurements, by using as model the oxidation of luminol by hydrogen peroxide or hypochlorite. An analytical procedure for hypochlorite determination was also developed, with linear response in the range 0.2-3.8 mg/L (2.7-51 mu mol/L), a detection limit estimated as 8 mu g/L (0.64 mu mol/L) at the 99.7% confidence level and luminol consumption of 50 mu g/determination. The coefficients of variation were 3.3% and 1.6% for 0.4 and 1.9 mg/L CIO(-), respectively, with a sampling rate of 164 determinations/h. The procedure was applied to the analysis of Dakin`s solution samples, yielding results in agreement with those obtained by iodometric titration at the 95% confidence level. Copyright (c) 2008 John Wiley & Sons, Ltd.

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.

An improved flow-based procedure for microdetermination of total tannins in beverages with minimized reagent consumption

A flow system designed with solenoid micro-pumps is introduced for spectrophotometric determination of total tannins based on the Folin- Denis reaction. The procedure minimizes the main drawbacks related to the AOAC batch procedure, i.e. interferences from reducing species in the samples, high reagent consumption and waste generation, and low sampling rate. Linear response was observed for tannic acid concentrations in the range 2-100 mg L-1, with a detection limit (99.7% confidence level) of 0.3 mg L-1. The sampling rate and coefficient of variation (n = 10) were estimated as 75 measurements per hour and 1.1%, respectively. Results of determination of total tannin in tea, beer and wine samples were in agreement with those achieved by the batch reference procedure at the 95% confidence level. In comparison to the batch procedure, the reagent consumption and effluent generation were 83 and 60-fold lower, respectively.

A flow-based analytical procedure for salbutamol determination exploiting chemiluminescence in a liquid-core waveguide

Salbutamol is a bronchodilator whose use is restricted due to its anabolic effects. A flow-based procedure for salbutamol determination based on the inhibition of chemiluminescence of the luminol/hypochlorite system was developed. A flow cell constructed with a liquid-core waveguide was employed to constrain the emitted radiation, minimizing losses during transport to detector. Linear response was observed within 2.5 x 10(-6) and 1.0 x 10(-5) mol L-1 with a detection limit estimated as 1 x 10(-7) mol L-1 at the 99.7% confidence level. The coefficient of variation (n = 20), sampling rate, and luminol consumption per determination were estimated as 2.8%, 164 determinations h(-1), and 50 mu g, respectively. Results for pharmaceutical samples were in agreement with those obtained by reference procedures at the 95% confidence level.

Systematic review and cladistic analysis of the genus Eusarcus Perty 1833 (Arachnida, Opiliones, Gonyleptidae)

Eusarcus Perty 1833 is one of the oldest described genera of Pachylinae, comprising 36 species distributed from northeastern to southern Brazil (including the central west region), northeastern Argentina, eastern Paraguay and Uruguay. The genus is reviewed and a new classification is proposed based on a cladistic analysis. A cladistic analysis was performed with the 34 valid species of Eusarcus and 11 species belonging to certain Gonyleptidae subfamilies. The data matrix has 67 characters: 14 from dorsal scutum and pedipalp, 38 from male legs and 15 from male genitalia. Two equally parsimonious trees were found (L=319; C. I.=0.26, R. I.=0.61). Pygophalangodus gemignanii uruguayensis Ringuelet 1955a and Pygophalangodus gemignanii gemignanii Mello-Leitao 1931b are here elevated to the category of species, and the following new combinations are proposed: E. catharinensis (Mello-Leitao 1927); E. berlae (Mello-Leitao 1932); E. gemignanii (Mello-Leitao 1931b); E. signatus(Roewer 1949); E. sooretamae (Soares & Soares 1946a); E. uruguayensis (Ringuelet 1955a). The following generic synonymies are proposed: Eusarcus Perty 1833 (type species E. armatus Perty 1833) = Metagraphinotus Mello-Leitao 1927 (type species M. catharinensis Mello-Leitao 1927), Pareusarcus Roewer 1929 (type species P. corniculatus Roewer 1929), Pygophalangodus Mello-Leitao 1931b (type species P. gemignanii-gemignanii Mello-Leitao 1931b) and Antetriceras Roewer 1949 (type species A. signatus Roewer 1949). The following specific synonymies are proposed: Eusarcus hastatus Sorensen 1884 = Pucrolioides argentina Roewer 1913, E. guimaraensi H. Soares 1945, Jacarepaguana pectinifemur Piza 1943, Canestrinia canalsi Mello-Leitao 1931a, and E. maquinensis H. Soares 1966b; E. armatus Perty 1833 = E. curvispinosus Mello-Leitao 1923b, and Enantiocentron montis Mello-Leitao 1936; Eusarcus catharinensis (Mello-Leitao 1927) = E. antoninae Mello-Leitao 1936, E. perpusillus Mello-Leitao 1945, E. tripos Mello-Leitao 1940, and Metagraphinotus trochanterspinosus Soares & Soares 1947b; E. nigrimaculatus Mello-Leitao 1924 = Pareusarcus centromelos Mello-Leitao 1935a, E. furcatus Roewer 1929, Orguesia armata Roewer 1913, and Pareusarcus corniculatus Roewer 1929; E. oxyacanthus Kollar in Koch 1839a = Enantiocentron doriphorus Mello-Leitao 1932, and E. spinimanu Mello-Leitao 1932; E. pusillus Sorensen 1884 = E. vervloeti B. Soares 1944c; E. berlae Mello-Leitao 1932 = Metagraphinotus arlei Mello-Leitao 1935a. Metapucrolia armata (Sorensen 1895) is revalidated, transferred to Eusarcus and considered as a species inquirenda. A new name, Eusarcus metapucrolia is proposed for this species to avoid homonymy with the type species of Eusarcus, E. armatus Perty 1833. Eusarcus aberrans Mello-Leitao 1939a is considered as a species inquirenda. The male of E. teresincola Soares & Soares 1946a is described. Female of the following species are described: E. bifidus Roewer 1929; E. dubius B. Soares 1943b; E. insperatus B. Soares 1944a; E. schubarti Soares & Soares 1946a; E. sooretamae (Soares & Soares 1946a). The following new species are described from Brazil: E. acrophthalmus (type locality: Bahia, Ilheus, Parataquice); E. alpinus (Rio de Janeiro, Santa Maria Madalena, Parque Estadual do Desengano); E. caparaoensis (Minas Gerais, Alto Caparao, Parque Nacional do Caparao); E. cavernicola (Goias, Sao Domingos, Parque Estadual de Terra Ronca, Lapa da Angelica); E. didactylus (Rio de Janeiro, Teresopolis, Parque Nacional Serra dos Orgaos); E. garibaldiae (Santa Catarina, Itajai); E. geometricus (Rio de Janeiro, Teresopolis, Parque Nacional Serra dos Orgaos); E. manero (Rio de Janeiro, Marica, Itaipuacu); E. matogrossensis (Mato Grosso, Chapada dos Guimaraes); E. mirabilis (Minas Gerais, Marlieria, Parque Estadual Rio Doce); E. sergipanus (Sergipe, Itabaiana, Parque Nacional de Itabaiana) and E. tripectinatus (Minas Gerais, Rio Preto). The holotype of E. curvispinosus is proposed as the neotype of E. armatus Perty 1833, the type material of which has been lost. Lectotypes for the following species were designated: E. aduncus; E. hastatus; E. oxyacanthus.

New familial assignments for three species of Neotropical harvestmen based on cladistic analysis (Arachnida: Opiliones: Laniatores)

We herein propose transfer of the two monotypic genera Globibunus (type-species G. rubrofemoratus Roewer, 1912) and Rivetinus (type-species R. minutus Roewer, 1919) to the subfamily Zamorinae (Agoristenidae) and Ramonus (type-species R. conifrons Roewer, 1956), previous placed in Agoristenidae, to the Prostygninae (Cranaidae) based on several characteristics of male genitalia. These transfers are corroborated by a cladistic analysis, which also recovered the three currently recognized agoristenid subfamilies.