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Cited by 24Water Quality Monitoring and AnalysisBiosensors and Analytical DetectionAnalytical Chemistry and Sensors

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An accurate, precise, and affordable light emitting diode spectrophotometer for drinking water and other testing with limited resources

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Prairie, Michael W., Frisbie, Seth H., Rao, K. Kesava, Saksri, Anyamanee H., Parbat, Shreyas, Mitchell, Erika J.·2020·PLOS ONE
DOI 10.1371/journal.pone.0226761PMC PMC6988917
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Abstract

Spectrophotometers are commonly used to measure the concentrations of a wide variety of analytes in drinking water and other matrixes; however, many laboratories with limited resources cannot afford to buy these very useful instruments. To meet this need, an accurate, precise, and affordable light emitting diode (LED) spectrophotometer was designed and built using best engineering practices and modern circuit design. The cost and performance of this LED spectrophotometer was compared against 4 common commercial spectrophotometers. More specifically, the performance of these spectrophotometers was evaluated from the upper limits of linear range, upper limits of operational range, calibration sensitivities, R2 values, precisions of standards, estimated limits of detection, and percent calibration check standard recoveries for the determinations of iron (Fe), manganese (Mn), and fluoride (F-) in drinking water. This evaluation was done in the United States (U.S.) and India. Our LED spectrophotometer costs $63 United States Dollars (USD) for parts. The 4 commercial spectrophotometers ranged in cost from $2,424 to $7,644 USD. There are no practical differences in the upper limits of linear range, upper limits of operational range, R2 values, precisions of standards, and estimated limits of detection for our LED spectrophotometer and the 4 commercial spectrophotometers. For 2 of the 3 analytes, there is a practical difference in the calibration sensitivities our LED spectrophotometer and the 4 commercial spectrophotometers. More specifically, the calibration sensitivities for Mn and F- using our LED spectrophotometer were 65.2% and 67.0% of those using the 4 commercial spectrophotometers, respectively. In conclusion, this paper describes the design, use, and performance of an accurate, precise, and extremely affordable LED spectrophotometer for drinking water and other testing with limited resources.

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Figures

Fig 1 The requirements, specifications, and component selection of the light emitting diode (LED) spectrophotometer.
Fig 1 The requirements, specifications, and component selection of the light emitting diode (LED) spectrophotometer.CC BY · PubMed Central
Fig 2 A block diagram of the light emitting diode (LED) spectrophotometer.
Fig 2 A block diagram of the light emitting diode (LED) spectrophotometer.CC BY · PubMed Central
Fig 3 A photograph of the light emitting diode (LED) spectrophotometer.
Fig 3 A photograph of the light emitting diode (LED) spectrophotometer.CC BY · PubMed Central
Fig 4 A schematic diagram of the power circuit.
Fig 4 A schematic diagram of the power circuit.CC BY · PubMed Central
Fig 5 A schematic diagram of the light emitting diode (LED) source circuit.
Fig 5 A schematic diagram of the light emitting diode (LED) source circuit.CC BY · PubMed Central
Fig 6 An exploded view of the sample cell holder.
Fig 6 An exploded view of the sample cell holder.CC BY · PubMed Central
Fig 7 A schematic diagram of the photodiode (PD) detector circuit. The signal conditioning chain uses a transimpedance amplifier, a high-pass filter, a DC-restore circuit, a peak detector, and a final stage amplifier.
Fig 7 A schematic diagram of the photodiode (PD) detector circuit. The signal conditioning chain uses a transimpedance amplifier, a high-pass filter, a DC-restore circuit, a peak detector, and a final stage amplifier.CC BY · PubMed Central
Fig 8 The calibration results for the determination of total iron (Fe) by the 1,10-phenanthroline method using a Hach DR-2700, a Hach 2010, and a Thermal Electron Spectronic 20D+ spectrophotometer [36].
Fig 8 The calibration results for the determination of total iron (Fe) by the 1,10-phenanthroline method using a Hach DR-2700, a Hach 2010, and a Thermal Electron Spectronic 20D+ spectrophotometer [36].CC BY · PubMed Central
Fig 9 The calibration results for the determination of total iron (Fe) by the 1,10-phenanthroline method using light emitting diode (LED) spectrophotometer #1 at blank voltages (V0) = 4.364 V, 3.872 V, 3.364 V, and 2.842 V [36].
Fig 9 The calibration results for the determination of total iron (Fe) by the 1,10-phenanthroline method using light emitting diode (LED) spectrophotometer #1 at blank voltages (V0) = 4.364 V, 3.872 V, 3.364 V, and 2.842 V [36].CC BY · PubMed Central
Fig 10 The calibration results for the determination of total iron (Fe) by the 1,10-phenanthroline method using light emitting diode (LED) spectrophotometer #2 at blank voltages (V0) = 4.364 V, 3.872 V, 3.366 V, and 2.846 V [36].
Fig 10 The calibration results for the determination of total iron (Fe) by the 1,10-phenanthroline method using light emitting diode (LED) spectrophotometer #2 at blank voltages (V0) = 4.364 V, 3.872 V, 3.366 V, and 2.846 V [36].CC BY · PubMed Central
Fig 11 The calibration results for the determination of total manganese (Mn) by the 1-(2-pyridylazo)-2-naphthol (PAN) method using a Hach DR-2700, a Hach 2010, and a Thermal Electron Spectronic 20D+ spectrophotometer [37].
Fig 11 The calibration results for the determination of total manganese (Mn) by the 1-(2-pyridylazo)-2-naphthol (PAN) method using a Hach DR-2700, a Hach 2010, and a Thermal Electron Spectronic 20D+ spectrophotometer [37].CC BY · PubMed Central
Fig 12 The calibration results for the determination of total manganese (Mn) by the 1-(2-pyridylazo)-2-naphthol (PAN) method using light emitting diode (LED) spectrophotometer #1 at blank voltages (V0) = 1.989 V, 1.553 V, 1.011 V, and 0.529 V [37].
Fig 12 The calibration results for the determination of total manganese (Mn) by the 1-(2-pyridylazo)-2-naphthol (PAN) method using light emitting diode (LED) spectrophotometer #1 at blank voltages (V0) = 1.989 V, 1.553 V, 1.011 V, and 0.529 V [37].CC BY · PubMed Central
Fig 13 The calibration results for the determination of total fluoride (F−) by the sodium 2-(parasulfophenylazo)-1,8-dihydroxy-3,6-naphthalene disulfonate (SPADNS) method using an Agilent Technologies Cary 60 UV-Vis (ultraviolet-visible) absorption spectrophotometer [36].
Fig 13 The calibration results for the determination of total fluoride (F−) by the sodium 2-(parasulfophenylazo)-1,8-dihydroxy-3,6-naphthalene disulfonate (SPADNS) method using an Agilent Technologies Cary 60 UV-Vis (ultraviolet-visible) absorption spectrophotometer [36].CC BY · PubMed Central
Fig 14 The calibration results for the determination of total fluoride (F−) by the sodium 2-(parasulfophenylazo)-1,8-dihydroxy-3,6-naphthalene disulfonate (SPADNS) method using light emitting diode (LED) spectrophotometer #1 at blank voltages (V0) = 0.358 V, 0.407 V, 0.486 V, 0.525 V, 0.550 V, and 0.627 V [36].
Fig 14 The calibration results for the determination of total fluoride (F−) by the sodium 2-(parasulfophenylazo)-1,8-dihydroxy-3,6-naphthalene disulfonate (SPADNS) method using light emitting diode (LED) spectrophotometer #1 at blank voltages (V0) = 0.358 V, 0.407 V, 0.486 V, 0.525 V, 0.550 V, and 0.627 V [36].CC BY · PubMed Central
Fig 15 The R2 values for the Agilent Technologies Cary 60 UV-Vis (ultraviolet-visible), Hach DR-2700, a Hach 2010, a Thermal Electron Spectronic 20D+, and 2 light emitting diode (LED) spectrophotometers used in this study (Tables 2–4).
Fig 15 The R2 values for the Agilent Technologies Cary 60 UV-Vis (ultraviolet-visible), Hach DR-2700, a Hach 2010, a Thermal Electron Spectronic 20D+, and 2 light emitting diode (LED) spectrophotometers used in this study (Tables 2–4).CC BY · PubMed Central
Fig 16 Bland-Altman plot comparing the Hach DR-2700 and LED spectrophotometer #1 for the determination of total iron (Fe) by the 1,10-phenanthroline method [36].
Fig 16 Bland-Altman plot comparing the Hach DR-2700 and LED spectrophotometer #1 for the determination of total iron (Fe) by the 1,10-phenanthroline method [36].CC BY · PubMed Central
Fig 17 Bland-Altman plot comparing the Hach 2010 and LED spectrophotometer #1 for the determination of total iron (Fe) by the 1,10-phenanthroline method [36].
Fig 17 Bland-Altman plot comparing the Hach 2010 and LED spectrophotometer #1 for the determination of total iron (Fe) by the 1,10-phenanthroline method [36].CC BY · PubMed Central
Fig 18 Bland-Altman plot comparing the Thermal Electron Spectronic 20D+ and LED spectrophotometer #1 for the determination of total iron (Fe) by the 1,10-phenanthroline method [36].
Fig 18 Bland-Altman plot comparing the Thermal Electron Spectronic 20D+ and LED spectrophotometer #1 for the determination of total iron (Fe) by the 1,10-phenanthroline method [36].CC BY · PubMed Central
Fig 19 Bland-Altman plot comparing the Hach DR-2700 and LED spectrophotometer #1 for the determination of total manganese (Mn) by the Hach 1-(2-pyridylazo)-2-naphthol (PAN) method [37].
Fig 19 Bland-Altman plot comparing the Hach DR-2700 and LED spectrophotometer #1 for the determination of total manganese (Mn) by the Hach 1-(2-pyridylazo)-2-naphthol (PAN) method [37].CC BY · PubMed Central
Fig 20 Bland-Altman plot comparing the Hach 2010 and LED spectrophotometer #1 for the determination of total manganese (Mn) by the Hach 1-(2-pyridylazo)-2-naphthol (PAN) method [37].
Fig 20 Bland-Altman plot comparing the Hach 2010 and LED spectrophotometer #1 for the determination of total manganese (Mn) by the Hach 1-(2-pyridylazo)-2-naphthol (PAN) method [37].CC BY · PubMed Central
Fig 21 Bland-Altman plot comparing the Thermal Electron Spectronic 20D+ and LED spectrophotometer #1 for the determination of total manganese (Mn) by the Hach 1-(2-pyridylazo)-2-naphthol (PAN) method [37].
Fig 21 Bland-Altman plot comparing the Thermal Electron Spectronic 20D+ and LED spectrophotometer #1 for the determination of total manganese (Mn) by the Hach 1-(2-pyridylazo)-2-naphthol (PAN) method [37].CC BY · PubMed Central
Fig 22 Bland-Altman plot comparing the Agilent Technologies Cary 60 UV-Vis and LED spectrophotometer #1 for the determination of total fluoride (F−) by the sodium 2-(parasulfophenylazo)-1,8-dihydroxy-3,6-naphthalene disulfonate (SPADNS) method [36].
Fig 22 Bland-Altman plot comparing the Agilent Technologies Cary 60 UV-Vis and LED spectrophotometer #1 for the determination of total fluoride (F−) by the sodium 2-(parasulfophenylazo)-1,8-dihydroxy-3,6-naphthalene disulfonate (SPADNS) method [36].CC BY · PubMed Central

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Research works printed but not linked: 6

  1. Mestha LK, Hubble III FF, Love TL, Skinner G, Mihalyov KJ, Robbins DA, Diehl DM. Low Cost LED Based Spectrophotometer. In: Final Program and Proceedings of ICIS ‘06, International Congress of Imaging Science. Rochester, NY: Society for Imaging Science and Technology; 2006. pp. 95−98.
  2. S Davis, 2004, Electronic design, Power: LDO voltage regulators
  3. P Horowitz, 2015, The art of electronics, 16
  4. GD Christian, 1986, Analytical chemistry, 371
  5. World Health Organization (WHO), 2011, Guidelines for drinking-water quality, 472
  6. World Health Organization (WHO), 2017, Guidelines for drinking-water quality. Fourth edition incorporating the first addendum, 472

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Metadata

Authors
Prairie, M. W., Frisbie, S. H., Rao, K. K., Saksri, A. H., Parbat, S., & Mitchell, E. J.
Affiliations
  • Norwich University (US)
  • Indian Institute of Science Bangalore (IN)
Corresponding author
Frisbie, Seth H.
ORCID
Venue
PLOS ONE
Publisher
Public Library of Science (PLoS)
Published
2020-01-29
Volume
15
Issue
1
Pages
e0226761
ISSN
1932-6203 (ISSN-L)
DOI
10.1371/journal.pone.0226761
PMC
PMC6988917
OpenAlex
W3003391244
Cited by
24
References
44
Citations by year
2026: 1 · 2025: 6 · 2024: 4 · 2023: 2 · 2022: 5 · 2021: 6
FWCI
2.00
Type
journal article
Language
en
Open access
Licence
Locations
  • PLoS ONE (publishedVersion, cc-by)
  • PubMed Central (publishedVersion, cc-by)
  • PubMed (publishedVersion)
  • NOT FOUND REPOSITORY (Indian Institute of Science Bangalore) (acceptedVersion)
  • DOAJ (DOAJ: Directory of Open Access Journals) (submittedVersion, cc-by-sa)
  • Figshare (submittedVersion, cc-by)
Funders
  • Ministry of Education, India
  • Division of Human Resource Development
Topics
  • Physical Sciences › Environmental Science › Waste Management and Disposal › Water Quality Monitoring and Analysis
  • Physical Sciences › Engineering › Biomedical Engineering › Biosensors and Analytical Detection
  • Physical Sciences › Chemistry › Analytical Chemistry › Analytical Chemistry and Sensors
Keywords
low-cost instrumentation, drinking water analysis, iron determination, manganese determination, fluoride determination, calibration sensitivity, detection limit, low-resource laboratories
MeSH terms
Calibration, Fluorides, Humans, Iron, Light, Manganese, Spectrophotometry, Drinking Water

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CoChat. (2026). Citation check: An accurate, precise, and affordable light emitting diode spectrophotometer for drinking water and other testing with limited resources. https://app.cochat.ai/papers/10.1371/journal.pone.0226761
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Prairie, M. W., Frisbie, S. H., Rao, K. K., Saksri, A. H., Parbat, S., & Mitchell, E. J. (2020). An accurate, precise, and affordable light emitting diode spectrophotometer for drinking water and other testing with limited resources. PLOS ONE. https://doi.org/10.1371/journal.pone.0226761