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Potentiometric multi-syringe flow injection system for determination of exchangeable potassium in soils with in-line extraction

Almeida, M. Inês G.S.; Segundo, Marcela A.; Lima, José L.F.C.; Rangel, António O.S.S.
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Publicado em //2006 ENG
Relevância na Pesquisa
1471.8619%
A multi-syringe flow injection system for the potentiometric determination of exchangeable potassium in soil samples is proposed. Firstly, a manifold was devised to allow determination in soil extracts prepared off-line. It was possible to analyze samples prepared in extractants with different composition (Mehlich or Morgan) without physical or chemical modification of the manifold. A linear dynamic concentration range of 6–391 mg L−1 was obtained, allowing the direct introduction of soil extract without dilution. A determination frequency of 50 h−1 was achieved, with good repeatability for 10 consecutive injections of soil extracts (RSDb3.0%). The in-line preparation of soil extract was implemented by automatic addition of extractant solution to a previously weighed portion of soil, followed by in-line filtration. Good repeatability was attained as the variance of the extraction procedure was not significantly different from the variance obtained in consecutive measurements of the same extract. Furthermore, results comparable to those obtained by off-line extraction and determination by flame emission spectrometry were attained for the two soil samples tested. Using this procedure, a determination frequency of 13 h−1 and a sampling rate of 4 h−1 were achieved.

The application of multicommutated flow techniques to the determination of iron

Pons, Carmen; Forteza, Rafael; Rangel, António O.S.S.; Cerdà, Víctor
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Publicado em //2006 ENG
Relevância na Pesquisa
1076.488%
New flow techniques such as multicommutated flow-injection analysis (MCFIA), multi-syringe FIA (MSFIA) and multi-pumping flow systems (MPFSs) have been developed. The low reagent consumption achieved by these techniques should be highlighted, as they can be regarded as environmentally friendly alternatives to conventional FIA. We present several applications of these novel flow techniques to the determination of iron.

Sample introduction in multi-syringe flow injection systems: comparison between time-based and volume-based strategies

Segundo, Marcela A.; Oliveira, Hugo M.; Lima, José L. F. C.; Almeida, M. Inês G. S.; Rangel, António O. S. S.
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Publicado em //2005 ENG
Relevância na Pesquisa
1171.8619%
In multi-syringe flowinjection analysis (MSFIA), devices as selection, injection or commutation valves must be incorporated to the manifold to provide access to sample and standard solutions. Therefore, the definition of sample amount can be either volume or time-based. In the present work, four configurations for sample introduction (two for each approach) were tested in order to establish if the different strategies affect the analytical signal in MSFIA systems. The mean absorbance value from ten consecutive injections of a bromothymol blue solution obtained for the time-based strategy was lower than that provided by the volume-based approach as the exact volume delivered by each configuration was different from the “theoretical” volume. For time-based configurations, the exact volume delivered is 2–5% lower than the theoretical value while for volume-based configurations, the volume delivered was between 6 and 46% larger than the theoretical volume. Moreover, for time-based sampling, the order of steps in the analytical cycle was of utmost importance since any alteration in the flow direction affected the volume delivered in the subsequent step in the analytical cycle. The influence of the two sampling approaches was also evaluated in the MSFIA systems for the spectrophotometric determination of phenolic compounds and the potentiometric determination of chloride. There was no evidence that the use of either volume or time-based sampling would improve the analytical features of these determinations when real samples were tested.

Spectrophotometric determination of iron and boron in soil extracts using a multi-syringe flow injection system

Gomes, D. M. C.; Segundo, M. A.; Lima, J. L. F. C.; Rangel, A. O. S. S.
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Publicado em //2005 ENG
Relevância na Pesquisa
1174.1767%
In the last decade, significant advances in flow analysis have been reported, namely the extensive use of computer-controlled devices to enhance the autonomy and performance of analysers. In the present work, computer-controlled multi-syringe flow injection systems are proposed to perform the spectrophotometric determination of available iron and boron in soil extracts. The methodologies were based on the formation of ferroin complex (determination of iron) and azomethine-H reaction (determination of boron). Both determinations were performed in manifolds with similar configurations by changing the reagents present in the different syringes. In the determination of iron, elimination of Schlieren effect in the detection system was achieved through the binary sampling approach, where a three-way valve was actuated to intercalate small slugs of sample and reagent, promoting better mixing conditions for solutions with different values of refractive index. In the determination of boron, in-line sample blank measurement was attained by omitting the introduction of reagent through software control, without manifold reconfiguration. Linear calibration curves were established between 0.50 and 10.0 mg Fe l−1 and between 0.20 and 4.0 mgBl−1. No systematic difference was found when soil extracts were analysed by the proposed methodologies and compared to the respective reference procedures.

Multi-syringe flow injection system with in-line microwave digestion for the determination of phosphorus

Almeida, M. Inês G.S.; Segundo, Marcela A.; Lima, José L.F.C.; Rangel, António O.S.S.
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Publicado em //2004 ENG
Relevância na Pesquisa
1055.0014%
A multi-syringe system for spectrophotometric determination of total phosphorus involving in-line digestion is proposed. Sample and digestion solution were dispensed and directed towards a digestion vessel located inside a domestic microwave oven (MWO) where sample digestion took place. Afterwards, the digested sample was merged with the necessary reagents for the colorimetric determination based on the molybdenum blue method. Several digestion conditions were studied regarding composition of digestion solution, digestion time and power set on theMWO. The system was applied to waste water samples and results shown a good agreement with the reference method. Repeatable results (R.S.D. < 2.41%) and determination frequency of 12 h−1 were obtained.

A multi-syringe flow injection system for the spectrophotometric determination of trace levels of iron in waters using a liquid waveguide capillary cell and different chelating resins and reaction chemistries

Páscoa, Ricardo N. M. J.; Tóth, Ildikó V.; Rangel, António O.S.S.
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Publicado em //2009 ENG
Relevância na Pesquisa
1575.7725%
A method integrating a long waveguide capillary cell with a preconcentration resin in a multi-syringe flow injection analysis (MSFIA) system for iron determination in waters was developed. The determination of iron is based on a colorimetric reaction and two reagents were tested, ferrozine and ammonium thiocyanate. A liquid waveguide capillary cell (1.0 m pathlength, 550 μm i.d. and 250 μL internal volume) with a preconcentration resin were used to improve the sensitivity of the determination. Two different preconcentration resins were also tested, Chelex 100 and NTA Superflow. The developed method employing the NTA Superflow with ferrozine colorimetric reagent provided a detection limit of 0.05 μg L−1 with a linear response up to 8 μg L−1 and a sample throughput rate of 12 per hour. The developed system presents low reagents/sample consumptions. The accuracy was assessed using a certified reference water sample.

Multi-syringe flow injection system for the determination of available phosphorus in soil samples

Almeida, M. Inês G. S.; Segundo, Marcela A.; Lima, José L. F. C.; Rangel, António O. S. S.
Fonte: Taylor & Francis Publicador: Taylor & Francis
Tipo: Artigo de Revista Científica
Publicado em //2005 ENG
Relevância na Pesquisa
1579.6553%
Considering the importance of monitoring the levels of nutrients present in soils and their availability to plants, an automatic methodology is proposed based on multi-syringe flow injection analysis (MSFIA) for the spectrophotometric determination of available phosphorus in soil extracts. This fully computerized flow technique allowed the development of a flow network where sample and reagents were intercalated and sent further towards the detection system. The colorimetric determination was based on the molybdenum blue method with ascorbic acid as reducing reagent and the Egner–Riehm method was applied to extract phosphorus from soil samples. A linear calibration curve was obtained between 0.75 and 15.0mgL-1. A determination frequency of 15 h-1 was achieved, with good repeatability for 12 consecutive injections of soil extracts (RSD<1.7%). The results obtained from 12 soil samples were statistically comparable to those attained by the usual batch method.

A multi-syringe flow injection system using a long liquid waveguide capillary flow cell and a chelating resin for the ultra trace determination of iron in waters

Páscoa, Ricardo N. M. J.; Tóth, Ildikó V.; Rangel, António O. S. S.
Fonte: Japanese Association for Flow Injection Analysis Publicador: Japanese Association for Flow Injection Analysis
Tipo: Artigo de Revista Científica
Publicado em //2008 ENG
Relevância na Pesquisa
832.6977%

A multi-syringe flow system for monitoring moderately fast chemical reactions

Cerdà,Víctor; Ubide,Carlos; Zuriarrain,Juan
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/11/2012 EN
Relevância na Pesquisa
1264.98836%
The zone stopping mode of the multi-syringe flow injection analysis (MSFIA) technique was exploited for monitoring of moderately fast reactions. The performance of MSFIA relies on the use of both efficient mixing chambers (cross unions) and a motor that propels a bar pushing up a number of syringes to provide dead times of about 20 ms. The well-known bromine generation from a bromate-bromide mixture in acidic medium is used as chemical system. The rate constant found (3.9 ± 0.7 mol-3 L³ s-1) agrees to values given in literature. Reagents in statu nascendi were also produced and used at once. As an example, bromine was generated and immediately used in the bromination of salicylic acid, avoiding the handling of dangerous chemicals; the rate constant found (5.5 ± 0.8 mmol-1 L s-1) agrees to the values given in literature. The methodology is an easy alternative to the traditional stopped-flow apparatus used in moderately fast reactions.