Exploring expressly designed ligands to develop expedite flow methods for onboard metal speciation in coastal high energy water systems

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Polymer inclusion membranes (PIMs) as an alternative for on-line solid phase extraction (SPE) in flow analysis

Publication . Ribas, Tânia C. F.; Croft, Charles F.; Mesquita, Raquel B. R.; Almeida, M. Inês G. S.; Kolev, Spas D.; Rangel, António O. S. S.

2018-03Conference object

Open access

Monitoring glucose, calcium, and magnesium levels in saliva as a non-invasive analysis by sequential injection multiparametric determination

Publication . Machado, Ana; Maneiras, Rui; Bordalo, Adriano A.; Mesquita, Raquel B. R.

2018Conference object

Open access

Sequential injection system with in-line solid phase extraction and soil minicolumn for determination of zinc and copper in soil leachates

Publication . Paluch, Justyna; Mesquita, Raquel B. R.; Cerdà, Victor; Kozak, Joanna; Wieczorek, Marcin; Rangel, António O. S. S.

A sequential injection (SI) system equipped with in-line solid phase extraction column and in-line soil minicolumn is proposed for determination of zinc and copper in soil leachates. The spectrophotometric determination (560 nm) is based on the reaction of both analytes with 1-(2-Pyridylazo)-2-naphthol (PAN). Zinc is determined after retaining copper on a cationic resin (Chelex100) whereas copper is determined from the difference of the absorbance measured for both analytes, introduced into the system with the use of a different channel, and zinc absorbance. The influence of several potential interferences was studied. Using the developed method, zinc and copper were determined within the concentration ranges of 0.005–0.300 and 0.011–0.200 mg L−1, and with a relative standard deviation lower than 6.0% and 5.1%, respectively. The detection limits are 1.4 and 3.0 μg/L for determination of zinc and copper, respectively. The developed SI method was verified by the determination of both analytes in synthetic and certified reference materials of water samples, and applied to the determination of the analytes in rain water and soil leachates from laboratory scale soil core column and in-line soil mini-column.

2018-01-30Journal article

Restricted access

Development of a robust, fast screening method for the potentiometric determination of iodide in urine and salt samples

Publication . Machado, Ana; Mesquita, Raquel B. R.; Oliveira, Sara; Bordalo, Adriano A.

In this work, a potentiometric flow injection method is described for the fast bi-parametric determination of iodide and iodate in urine and salt samples. The developed methodology aimed for iodine speciation with a potentially portable system (running on batteries). The iodate reduction to iodide was effectively attained in line within the same manifold. The iodide determination was accomplished in the dynamic range of 2.50×10−6– 1.00×10−3 M and the total iodine dynamic range, resulted from iodide plus iodate, was 3.50×10−6– 2.00×10−3 M. The calculated limits of detection were 1.39×10−6 M and 1.77×10−6 M for iodide and iodate, respectively. A determination rate of 21 h−1 for the bi-parametric iodide and iodate determination was obtained for sample injection. The urine samples (RSD < 5.8% for iodide and RSD < 7.0% for iodate) results were in agreement with those obtained by the classic Sandell-Kolthoff reaction colorimetric reference procedure (RD < 7.0%) and standard samples from Centers for Disease Control and Prevention, Atlanta, USA (CDC) international inter-laboratory EQUIP program. The developed flow method was also successfully applied to the iodide and iodate determination in salt samples (RSD < 3.1% for iodate and iodide), with comparable results to conventional procedures. No significant interferences were observed interference percentage < 9% for both determinations.

2017Journal article

Restricted access

A greener alternative for inline nitrate reduction in the sequential injection determination of NOx in natural waters: replacement of cadmium reduction by UV radiation

Publication . Machado, Ana; Marshall, Graham; Bordalo, Adriano A.; Mesquita, Raquel B. R.

The use of sequential injection analysis (SIA) for key nutrient determination in water has been previously described using a copperised cadmium column to attain nitrate reduction to nitrite prior to determination, yielding hazardous waste. Here, a greener alternative is proposed for nitrate reduction using a UV lamp, aiming to avoid the use of cadmium. This method was based on the colorimetric Griess reaction for nitrite determination, after the UV reduction of nitrate. The reduction was performed inline during the determination of nitrite, minimizing both effluent production and the overall determination rate. Its application to natural waters, namely river water, proved to be effective as the results were comparable to those obtained with the reference procedure. Furthermore, certified reference samples were analysed, and an average of 3% relative deviation was observed. A limit of detection of 5.30 mM was achieved, enabling the nitrate determination in the dynamic range of 25-500 mM with a determination rate of 24 h(-1), and with a recovery percentage rate around 100%.

2017Journal article

Restricted access