Elsevier

Measurement

Volume 164, November 2020, 108085
Measurement

Microfluidic paper-based device integrated with smartphone for point-of-use colorimetric monitoring of water quality index

https://doi.org/10.1016/j.measurement.2020.108085Get rights and content

Highlights

  • Versatile and low-cost 3D printer method for building point-of-use device was proposed.

  • A disposable µPAD was used for determination of pH, water hardness and total phenols.

  • Smartphones were used for the quantification of analytical interest species.

  • Simple and fast colorimetric method was applied for monitoring the quality index in water samples.

Abstract

The measurements by lab-on-a-chip devices are very interesting regarding the reduction of reagents, time and cost. In this paper, we have described the construction and application of a new device based on colorimetric measurements using a smartphone camera and a microfluidic paper-based device (μPAD), both fixed in supports obtained through 3D printing, employing a polylactic acid filament. The μPAD was evaluated as a water quality index device by colorimetric monitoring of water hardness (Ca2+ and Mg2+), total phenols (catechol), and pH. Under optimized parameters, the proposed method presented a linear range between 20 and 560 mg L−1 for Ca2+ and Mg2+(hardness), 0.20 to 16 mg L−1 of catechol and pH from 4.7 to 12, and limits of detection of 0.083 mg L−1, 0.124 mg L−1 and 0.262, for water hardness, catechol, and pH, respectively. The proposed device was successfully applied for the quality monitoring of the distribution of water samples.

Introduction

The search for fast and accurate analytical devices has led to the development of the point-of-use (POU) detection systems [1]. For a successful POU application, some characteristics are essential, such as simple operation, the facility for remote monitoring (portability), and the ability for the detection of multiple analytes or samples [2]. In this sense, the miniaturization of the devices is also an exciting strategy for achieving the analysis system portability. The control of fluid flow in microscale, or microfluidic transport, allows the handling of small amounts of fluids on microchannels [3]. Microfluidic devices use a lower amount of samples and reagents and offer high analytical frequency, selectivity, sensibility, and portability [4], [5].

Microfluidic devices can be made using different materials, such as glass [6], [7], polymers [4], [8], and paper [9], [10]. The microfluidic paper-based analytical devices (μPADs) highlight to be affordability substrates with low-cost for fabrication [11]. Naturally, the paper has microchannels and hydrophilicity, which allow the transport of the aqueous solutions without external pumping [12]. In this context, hydrophobic barriers are usually created on paper substrates to delimit the transport of samples along channels towards the detection zone when necessary [13]. Different approaches can perform the generation of these barriers as photolithography and wax printing [14]. Therefore, paper-based devices can be applied for microfluidic and quantitative colorimetric detection [12], producing reliable diagnostics in remote regions [14]. On the other hand, the analysis based on images has been the most used, once it can be obtained through smartphone cameras [13], [15], [16], [17], [18], [19].

The noticeable growth in the technology of 3D printing has caused improvements in the ability to prepare solid structures with geometric precision [20], [21], [22], [23]. The 3D printing allows the development of devices by the fused deposition modeling (FDM) technology wherein the material thermoplastic is heated and fused, making possible the 3D printing of microfluidic devices [24], [25]. Different polymers can be used, such as poly-lactic acid (PLA) and acrylonitrile–butadienestyrene (ABS). In this context, PLA has biodegradable characteristics, which can be an important benefit for environmental applications [21], [22].

Water is an essential resource for the permanence of life; therefore, its quality control is very important. The current problems of water quality, most evidenced, have been the water hardness, acidity, and the presence of toxic organic species [26]. Calcium and magnesium ions dissolved in water are factors that define the total water hardness levels [27]. The water that presents hardness less than 60.0 mg L−1 is classified as soft. It is moderately hard from 61.0 to 120 mg L−1 and hard from 121 to 180 mg L−1. When the hardness is more than 181 mg L−1, it is very hard [28]. The Brazilian Ministry of Health reports the allowed maximum limit is 500 mg L−1 [29]. Indeed, hard water can bring problems for home delivery networks and industries, causing low efficiency of the cleaning products, once can generate insoluble salts causing the obstruction of the pipes by salts deposition [30]. Currently, the most traditional water hardness determination is carried out by complexometric titration with EDTA [30].

On the other hand, phenols are toxic and difficult removal, which are generally found in industrial wastewaters. The determination of phenols levels in water is critical since low concentrations (1000 mg L−1) may be lethal if ingested by humans, or prejudicial when inhaled or in contact with the skin and eyes [31], [32], [33]. The lethal dose (LD50) in fish and crustaceans, for example, is between 3.0 and 7.0 mg L−1. For microorganisms such as bacteria, protozoa, and fungi, the limit is approximately 64 mg L−1 [34].

The pH is an important parameter for the water quality control [35], already that pH influences in aquatics ecosystems, with an ideal value between 6.0 and 9.0 [36]. Also, household consumption, manufacture of industrial products and agriculture can be affected by water with pH different from the ideal [37]. According to the United States Environmental Protection Agency (US-EPA), the water drinking standards for supplying are between pH values 6.0 and 9.5 [29].

In this work, a μPAD and its measurement framework have been developed with cutter printer and 3D printer for environmental interest analysis by colorimetric detection of water hardness, phenols and pH using a smartphone. Generally, the monitoring of water quality is evaluated using methods based on spectrophotometry and chromatography. However, the cost and some limitations of these techniques have been boosting new quick and low-cost analytical methods [32]. New apparatus by using daily materials have emerged in the last years. In this context, lab-made equipment coupled to smartphones has been used in several analytical applications [38], [39], [40] for the colorimetric determination as an alternative for different species monitoring [41], [42]. These devices are efficient, and they are a low-cost alternative for the colorimetric determination of species of environmental interest [43]. Other advantages of a green chemical point of view are low chemical consumption and waste generation [44].

Section snippets

Reagents preparation

The reagents used were magnesium sulfate (98.0–102.0%), ammonium hydroxide (NH3 content 27%), potassium ferricyanide (99.0%) and sodium chloride (99.0%) from Synth (São Paulo, Brazil); bromothymol blue (100.0%) and ammonium chloride (99.5%) from Dinâmica (Indaiatuba, Brazil); calcium chloride (99.0–105.0%) dihydrate pyrocatechol (pyrocatechin) (99.0%), eriochrome black T (100.0%) and 4-aminoantipyrine (97.0%), obtained from Sigma Aldrich (St. Louis, MO, USA). The solutions were prepared with

Analytical performance of point-of-use based in µPAD device

The proposed POU device was evaluated for a simple in-situ analysis of potable water quality by monitoring of different indicators: water hardness, total phenols and pH based on colorimetric measurements using a smartphone camera and µPAD. The number of operational steps during analysis is less for POU devices when compared to the classical methods, such as colorimetric titration. Fig. 2 shows the image capture measurement of the developed device.

The proposed method consisted of 3 steps: (a)

Conclusions

We have proposed a new device for a simple in-situ analysis of potable water, which was based on colorimetric measurements using a smartphone camera and µPAD, both fixed in 3D printed supports designed for this purpose. The use of 3D-printing allowed to obtain and to change all measurement framework through the simple changing of the working parameters. The μPAD was obtained quickly by a cutter printer and it allowed a low consumption of reagents and samples. Low-cost presented by µPAD are also

Credit authorship contribution statement

Vinicius Aparecido Oliani Pedro da Silva: Methodology, Data curation, Investigation, Formal analysis, Writing - original draft, Writing - review & editing. Rafaela Cristina de Freitas: Methodology. Paulo Roberto de Oliveira: Data curation, Investigation, Formal analysis, Writing - original draft, Writing - review & editing. Roger Cardoso Moreira: Supervision, Writing - review & editing. Luiz Humberto Marcolino-Júnior: Conceptualization, Supervision, Writing - review & editing. Márcio Fernando

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgments

The authors are grateful for the financial support of Brazilian Funding Agencies. This study was financed in part by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior – Brasil (CAPES), Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) (2017/21898-6, 2017/21097-3 and 2019/01844-4) and Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) (303338/2019-9, 402943/2016-3, and 408309/2018-0) for financial support.

References (62)

  • B. Panda et al.

    Experimental and numerical modelling of mechanical properties of 3D printed honeycomb structures

    Measurement

    (2018)
  • M.I. Veríssimo et al.

    Determination of the total hardness in tap water using acoustic wave sensors

    Sens. Actuators, B

    (2007)
  • M.H. El-Naas et al.

    Biodegradation of phenol by Pseudomonas putida immobilized in polyvinyl alcohol (PVA) gel

    J. Hazard. Mater.

    (2009)
  • W. Zhang et al.

    A smartphone-integrated ready-to-use paper-based sensor with mesoporous carbon-dispersed Pd nanoparticles as a highly active peroxidase mimic for H2O2 detection

    Sens. Actuators, B

    (2018)
  • M.S. Masoud et al.

    Dissociation constants of eriochrome black T and eriochrome blue black RC indicators and the formation constants of their complexes with Fe(III), Co(II), Ni(II), Cu(II), Zn(II), Cd(II), Hg(II), and Pb(II), under different temperatures and in presence of different solvents

    Thermochim Acta

    (2002)
  • S. Karita et al.

    Chelate titrations of Ca2+ and Mg2+ using microfluidic paper-based analytical devices

    Anal. Chim. Acta

    (2016)
  • H.R. Marona et al.

    Spectrophotometric determination of sparfloxacin in pharmaceutical formulations using bromothymol blue

    J. Pharm. Biomed. Anal.

    (2001)
  • Y. He et al.

    3D printed paper-based microfluidic analytical devices

    Micromachines

    (2016)
  • F.R. Caetano et al.

    Combination of electrochemical biosensor and textile threads: A microfluidic device for phenol determination in tap water

    Biosens. Bioelectron.

    (2018)
  • Y. Wang et al.

    A smartphone-based colorimetric reader coupled with a remote server for rapid on-site catechols analysis

    Talanta

    (2016)
  • A. Lopez-Molinero et al.

    Feasibility of digital image colorimetry—application for water calcium hardness determination

    Talanta

    (2013)
  • M. Arciuli et al.

    Bioactive paper platform for colorimetric phenols detection

    Sens. Actuat. B: Chem.

    (2013)
  • Z. Yan et al.

    A novel luminol derivative and its functionalized filter-paper for reversible double-wavelength colorimetric pH detection in fruit juice

    Sens. Actuat. B: Chem.

    (2018)
  • M. Moradi et al.

    A novel pH-sensing indicator based on bacterial cellulose nanofibers and black carrot anthocyanins for monitoring fish freshness

    Carbohydr. Polym.

    (2019)
  • G.M. Whitesides

    The origins and the future of microfluidics

    Nature

    (2006)
  • E.A. Carneiro et al.

    3D-printed Microfluidic Device Based on Cotton Threads for Amperometric Estimation of Antioxidants in Wine Samples

    Electroanalysis

    (2018)
  • M. Boyd-Moss et al.

    Self-contained microfluidic systems: a review

    Lab Chip

    (2016)
  • A.W. Martinez et al.

    Diagnostics for the Developing World: Microfluidic Paper-Based Analytical Devices

    Anal. Chem.

    (2010)
  • W.K.T. Coltro et al.

    Capacitively coupled contactless conductivity detection on microfluidic systems—ten years of development

    Anal. Methods

    (2012)
  • C. Parolo et al.

    based nanobiosensors for diagnostics

    Chem. Soc. Rev.

    (2013)
  • L. Shen et al.

    Point-of-care colorimetric detection with a smartphone

    Lab Chip

    (2012)
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