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About

About

I was born in Lisbon, Portugal, in 1983 and graduated from Faculdade de Ciências e Tecnologia Universidade Nova de Lisboa (FCT-UNL) in Physics Engineering in 2006. My undergraduate research consisted in developing and assembly of a specialized X-ray fluorescence spectrometer. This work lead to a Master in Physics Engineering (FCT-UNL, 2007) and a PhD in Atomic Physics (FCT-UNL, 2011) entitled: “Measurement of lead concentration in biological tissues by atomic spectroscopy techniques”.

In 2012, I moved to Albany (New York, USA) as a Postdoc in Analytical Chemistry, to work at the Trace Elements group, Wadsworth Center New York State Department of Health. In the same year I transitioned to a Research Scientist position and became supervisor of the X-ray lab. Here I participated in multiple projects concerning biomonitoring and environmental analysis of trace elements in several matrices (food, cosmetics, medicines, consumer products, human tissues and body fluids) using analytical techniques based on atomic spectrometry, including synchrotron radiation at the Cornell University. I also spent 2 years as a Research Assistant Professor at the University at Albany, State University of New York – School of Public Health, Department of Environmental Health Sciences.

In 2016 I decided to shift my research focus from atomic to nuclear radiation.  I moved to Porto, Portugal, and I am currently working at INESC-TEC developing fiber optic sensors to detect the presence of Radon, a radioactive element, in marine environments.

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001
Publications

2018

Characterization of arsenic in dried baby shrimp (Acetes sp.) using synchrotron-based X-ray spectrometry and LC coupled to ICP-MS/MS

Authors
Guimarães, D; Roberts, AA; Tehrani, MW; Huang, R; Smieska, L; Woll, AR; Lin, S; Parsons, PJ;

Publication
Journal of Analytical Atomic Spectrometry

Abstract
The arsenic content of dried baby shrimp (Acetes sp.) was investigated as part of an independent field study of human exposure to toxic metals/metalloids among the ethnic Chinese community located in Upstate New York. The dried baby shrimp were analyzed in a home environment using a portable X-Ray Fluorescence (XRF) instrument based on monochromatic excitation. Study participants had obtained their dried baby shrimp either from a local Chinese market or prepared them at home. The shrimp are typically between 10-20 mm in size and are consumed whole, without separating the tail from the head. Elevated levels of As were detected using portable XRF, ranging between 5-30 µg g-1. Shrimp samples were taken to the Cornell High Energy Synchrotron Source (CHESS) for Synchrotron Radiation µXRF (SR-µXRF) elemental mapping using a 384-pixel Maia detector system. The Maia detector provided high resolution trace element images for As, Ca, and Br, (among others) and showed localized accumulation of As within the shrimp's cephalothorax (head), and various abdominal segments. As quantification by SR-µXRF was performed using a lobster hepatopancreas reference material pellet (NRC-CNRC TORT-2), with results in good agreement with both portable XRF and ICP-MS. Additional As characterization using µX-ray Absorption Near Edge Spectroscopy (µXANES) with the Maia XRF detector at CHESS identified arsenobetaine and/or arsenocholine as the possible As species present. Further arsenic speciation analysis by LC-ICP-MS/MS confirmed that the majority of As (>95%) is present as the largely non-toxic arsenobetaine species with trace amounts of arsenocholine, methylated As and inorganic As species detected. © The Royal Society of Chemistry.

2017

Assessing arsenic and selenium in a single nail clipping using portable X-ray fluorescence

Authors
Fleming, DEB; Nader, MN; Foran, KA; Groskopf, C; Reno, MC; Ware, CS; Tehrani, M; Guimaraes, D; Parsons, PJ;

Publication
APPLIED RADIATION AND ISOTOPES

Abstract
The feasibility of measuring arsenic and selenium contents in a single nail clipping was investigated using a small-focus portable X-ray fluorescence (XRF) instrument with monochromatic excitation beams. Nail clipping phantoms supplemented with arsenic and selenium to produce materials with 0, 5, 10, 15, and 20 mu g/g were used for calibration purposes. In total, 10 different clippings were analyzed at two different measurement positions. Energy spectra were fit with detection peaks for arsenic K-alpha, selenium K-alpha, arsenic K-beta, selenium K-beta, and bromine K-alpha characteristic X-rays. Data analysis was performed under two distinct conditions of fitting constraint. Calibration lines were established from the amplitude of each of the arsenic and selenium peaks as a function of the elemental contents in the clippings. The slopes of the four calibration lines were consistent between the two conditions of analysis. The calculated minimum detection limit (MDL) of the method, when considering the Ka peak only, ranged from 0.210 +/- 0.002 mu g/g selenium under one condition of analysis to 0.777 +/- 0.009 mu g/g selenium under another. Compared with previous portable XRF nail clipping studies, MDLs were substantially improved for both arsenic and selenium. The new measurement technique had the additional benefits of being short in duration (similar to 3 min) and requiring only a single nail clipping. The mass of the individual clipping used did not appear to play a major role in signal strength, but positioning of the clipping is important.

2016

Quantitative determinations and imaging in different structures of buried human bones from the XVIII-XIXth centuries by energy dispersive X-ray fluorescence - Postmortem evaluation

Authors
Guimaraes, D; Dias, AA; Carvalho, M; Carvalho, ML; Santos, JP; Henriques, FR; Curate, F; Pessanha, S;

Publication
TALANTA

Abstract
In this work, a non-commercial triaxial geometry energy dispersive X-ray Fluorescence (EDXRF) setup and a benchtop mu-XRF system were used to identify postmortem contamination in buried bones. For two of the individuals, unusually high concentrations of Cu and Pb, but also Zn (in one individual) were observed. The pigments of the burial shroud coverings have been identified as the source of contamination. Accurate and precise quantitative results were obtained by nondestructive process using fundamental parameters method taking into account the matrix absorption effects. A total of 30 bones from 13 individuals, buried between the mid-XVlllth to early XIXth centuries, were analyzed to study the elemental composition and elemental distribution. The bones were collected from a church in Almada (Portugal), called Ermida do Espirito Santo, located near the Tagus River and at the sea neighbourhood. The triaxial geometry setup was used to quantify Ca, Fe, Cu, Zn, Br, Sr and Pb of powder pressed bone pellets (n=9 for each bone). Cluster analysis was performed considering the elemental concentrations for the different bones. There was a clear association between some bones regarding Fe, Cu, Zn, Br and Pb content but not a categorization between cortical and trabecular bones. The elemental distribution of Cu, Zn and Pb were assessed by the benchtop p.-analysis, the M4 Tornado, based on a polycapillary system which provides multi-elemental 2D maps. The results showed that contamination was mostly on the surface of the bone confirming that it was related to the burial shroud covering the individuals.

2016

Evaluation of a new optic-enabled portable XRF instrument for measuring toxic metals/metalloids in consumer goods and cultural products

Authors
Guimarães, D; Praamsma, ML; Parsons, PJ;

Publication
Spectrochimica Acta - Part B Atomic Spectroscopy

Abstract
X-ray fluorescence spectrometry (XRF) is a rapid, non-destructive multi-elemental analytical technique used for determining elemental contents ranging from percent down to the µg/g level. Although detection limits are much higher for XRF compared to other laboratory-based methods, such as inductively coupled plasma mass spectrometry (ICP-MS), ICP-optical emission spectrometry (OES) and atomic absorption spectrometry (AAS), its portability and ease of use make it a valuable tool, especially for field-based studies. A growing necessity to monitor human exposure to toxic metals and metalloids in consumer goods, cultural products, foods and other sample types while performing the analysis in situ has led to several important developments in portable XRF technology. In this study, a new portable XRF analyzer based on the use of doubly curved crystal optics (HD Mobile®) was evaluated for detecting toxic elements in foods, medicines, cosmetics and spices used in many Asian communities. Two models of the HD Mobile® (a pre-production and a final production unit) were investigated. Performance parameters including accuracy, precision and detection limits were characterized in a laboratory setting using certified reference materials (CRMs) and standard solutions. Bias estimates for key elements of public health significance such as As, Cd, Hg and Pb ranged from -10% to 11% for the pre-production, and -14% to 16% for the final production model. Five archived public health samples including herbal medicine products, ethnic spices and cosmetic products were analyzed using both XRF instruments. There was good agreement between the pre-production and final production models for the four key elements, such that the data were judged to be fit-for-purpose for the majority of samples analyzed. Detection of the four key elements of interest using the HD Mobile® was confirmed using archived samples for which ICP-OES data were available based on digested sample materials. The HD Mobile® XRF units were shown to be suitable for rapid screening of samples likely to be encountered in field based studies. © 2016 Elsevier B.V.

2015

Radioisotope-based XRF instrumentation for determination of lead in paint: an assessment of the current accuracy and reliability of portable analyzers used in New York State

Authors
Guimarães, D; Cleaver, TM; Martin, SF; Parsons, PJ;

Publication
Anal. Methods

Abstract