Browsing by Author "Aguiar, Juliana I. S."
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- Design and development of a mPAD device for magnesium determination in salivaPublication . Aguiar, Juliana I. S.; Mesquita, Raquel B. R.; Rangel, António O. S. S.
- Development of a microfluidic paper-based analytical device for magnesium determination in saliva samplesPublication . Aguiar, Juliana I. S.; Silva, Mafalda T. S.; Ferreira, Helena A. G.; Pinto, Elisabete C. B.; Vasconcelos, Marta W.; Rangel, António O. S. S.; Mesquita, Raquel B. R.In this work, a microfluidic paper-based analytical device (μPAD) was developed for magnesium determination in saliva samples. The idea was to develop a fast and simple method for biological magnesium quantification targeting saliva as an easy to collect and non-invasive alternative to blood or urine samples. The μPAD approach was chosen due to its advantages, namely ideally suited to conduct on-location determinations, and not requiring trained operators or specialized laboratory equipment. The developed μPAD was based on the colorimetric reaction between eriochrome cyanine and magnesium to form an intense orange/reddish colour product. The colour intensity was determined by image processing after digital scanning, made within 10 to 90 min after sample loading. Under optimal conditions, the dynamic concentration range was 82–247 μM, with detection and quantification limits of 62 μM and 81 μM, respectively. The device is stable for up to 3 months when stored in vacuum or in a modified nitrogen atmosphere. An accuracy assessment was made by comparing the results obtained using the developed μPAD with those from atomic absorption spectrometry (AAS). The relative difference between the two sets of results was below 5%.
- Iron determination in natural waters using a synthesised 3-hydroxy-4-pyridione ligand in a newly developed microfluidic paper-based devicePublication . Aguiar, Juliana I. S.; Ribeiro, Susana O.; Leite, Andreia; Rangel, Maria; Rangel, António O. S. S.; Mesquita, Raquel B. R.This work describes the development of an iron sensor based on a microfluidic paper-based technique, to attain iron quantification in natural waters. A new water-soluble naphthalene-3-hydroxy-4-pyridione ligand was used as a colour reagent, as it formed an orange complex with iron. As a newly described ligand, several chemical and physical parameters, namely, the sample and reagent volumes and reagent concentrations, were studied related to the formation of the coloured complex. The microfluidic paper-based analytical device (μPAD) assembly, namely, the use of different types of filter paper and different numbers of layers, was developed to obtain the best performance. Under the optimal conditions, a linear correlation was obtained in the range of 0.25–2.00 mg/L of iron, with a minimum detectable value of 0.07 mg/L. The proposed μPAD method was validated by an analysis of the certified samples and by a comparison of the tested water samples with the inductively coupled plasma (ICP) results (RE < 10%). Then, the μPAD device was successfully applied to the determination of iron in tap water, well water, river water, and seawater, with no need for any prior sample pre-treatment; recovery studies were also performed (average = 100.3% with RSD = 4.2%).
- Quantification of salivary magnesium using a microfluidic paper based analytical device (μPAD)Publication . Silva, Mafalda T. S.; Aguiar, Juliana I. S.; Mesquita, Raquel B. R.; Rangel, António O. S. S.
- Salivary calcium determination with a specially developed microfluidic paper-based device for point-of-care analysisPublication . Aguiar, Juliana I. S.; Rangel, António O. S. S.; Mesquita, Raquel B. R.The calcium monitoring in the body not only anticipates several potential diseases (osteoporosis, kidney stones or high blood pressure) but also helps to improve target therapies and follow-up the patient's health status. Calcium monitoring is essential for the diagnosis of one of the most common endocrine disorders worldwide, namely hyperparathyroidism. So, in this work, a new Point-of-care test (POC-test) using a microfluidic paper-based analytical device (μPAD) for calcium quantification in saliva samples is described. The developed μPAD was based on the colorimetric reaction between calcium and cresolphthalein complexone (CPC) which forms an intense purple colour product. The developed device enabled calcium quantification in the range of 0.27–4.50 mmol/L (11.0–180 mg/L) with a detection limit of 80 µmol/L (3.2 mg/L). The accuracy of the developed μPAD was confirmed by analysing saliva samples (#10) and comparing the results obtained with the atomic absorption spectrometry reference procedure; the relative deviation between the two sets of results was below 10 %. A correlation between salivary calcium content and calcium content in blood was established and it was possible to conclude that salivary calcium concentrations above 1.55 mmol/L is an indicator of hypercalcemia. The developed device was stable for 2 weeks when stored at room temperature in vacuum conditions.
- Use of a rhodamine-based chelator in a microfluidic paper-based analytical device for the in-situ copper quantification in natural watersPublication . Aguiar, Juliana I. S.; Ribeiro, Susana O.; Leite, Andreia; Rangel, Maria; Rangel, António O. S. S.; Mesquita, Raquel B. R.This work describes the development of a microfluidic paper-based analytical device (μPAD) for the determination of copper in fresh and marine waters. A functionalized rhodamine-based chelator was synthesized and used as a chromogenic reagent, forming a highly intense pink complex with the analyte. The aim was to create a paper device that offers optimal performance and provides in-situ, rapid and cost-effective analysis in line with World Health Organization guidelines. The influence on the determination of several physical and chemical parameters was evaluated aiming to achieve the best performance. Under optimised conditions, a linear correlation was established in the range of 0.05–0.50 mg L−1 of copper, with a limit of detection of 10 μg L−1. The accuracy of the proposed method was assessed by comparing the results obtained with the developed μPAD and the results obtained with Inductively Coupled Plasma measurements (RE < 10 %). Recovery studies were also performed using different types of water samples with no need for any prior sample pre-treatment: tap, well, river and seawater. The average recovery percentage of 101 % (RSD = 4.3 %) was obtained, a clear indication of no multiplicative matrix interferences.