scholarly journals Supplementary material to "Multifactor colorimetric analysis on pH-indicator papers: an optimized approach for direct determination of ambient aerosol pH"

2019 ◽  
Author(s):  
Guo Li ◽  
Hang Su ◽  
Nan Ma ◽  
Guangjie Zheng ◽  
Uwe Kuhn ◽  
...  
Keyword(s):  
Direct Determination ◽  
Colorimetric Analysis ◽  
Ph Indicator ◽  
Ambient Aerosol ◽  
Supplementary Material

Multifactor colorimetric analysis on pH-indicator papers: an optimized approach for direct determination of ambient aerosol pH

2020 ◽  
Author(s):  
Guo Li ◽  
Hang Su ◽  
Nan Ma ◽  
Guangjie Zheng ◽  
Uwe Kuhn ◽  
...  
Keyword(s):  
Direct Determination ◽  
Heterogeneous Reactions ◽  
High Time Resolution ◽  
Colorimetric Analysis ◽  
Ph Indicator ◽  
Ambient Aerosols ◽  
Detection Range ◽  
Ambient Aerosol ◽  
The Impact

<p>Direct measurement of the acidity (pH) of ambient aerosol particles/droplets has long been a challenge for atmospheric scientists.  A novel and facile method was introduced recently by Craig et al. (2018), where the pH of size-resolved aerosol droplets was directly measured by two types of pH-indicator papers (pH ranges: 0 – 2.5 and 2.5 – 4.5) combined with RGB-based colorimetric analyses using a model of G-B (G minus B) versus pH<sup>2</sup>.  Given the wide pH range of ambient aerosols, we optimize the RGB-based colorimetric analysis on pH papers with a wider detection range (pH ~ 0 to 6).  Here, we propose a new model to establish the linear relationship between RGB values and pH: pH<sub>predict</sub> = a×R<sub>normal</sub> + b×G<sub>normal</sub> + c×B<sub>normal</sub>.  This model shows a wider applicability and higher accuracy than those in previous studies, and is thus recommended in future RGB-based colorimetric analyses on pH papers.  Moreover, we identify one type of pH paper (Hydrion<sup>®</sup> Brilliant pH dip stiks, Lot Nr. 3110, Sigma-Aldrich) that is more applicable for ambient aerosols in terms of its wide pH detection range (0 to 6) and strong anti-interference capacity.  The determined minimum sample mass (~ 180 µg) highlights its potential to predict aerosol pH with a high time resolution (e.g., ≤ 1 hour).  We further show that the routinely adopted way of using pH color charts to predict aerosol pH may be biased by the mismatch between the standard colors on the color charts and the real colors of investigated samples.  Thus, instead of using the producer-provided color chart, we suggest an in-situ calibration of pH papers with standard pH buffers.</p><p>Reference:</p><p>Craig, et al., Direct determination of aerosol pH: Size-resolved measurements of submicrometer and supermicrometer aqueous particles. Analytical Chemistry, 90 (19), 11232-11239, 2018.</p><p>Cheng, et al., Reactive nitrogen chemistry in aerosol water as a source of sulfate during haze events in China. Science Advances, 2 (12), e1601530, 10.1126/sciadv.1601530, 2016.</p><p>Zheng, et al., Exploring the severe winter haze in Beijing: The impact of synoptic weather, regional transport and heterogeneous reactions. Atmospheric Chemistry and Physics, 15, 2969-2983, 2015.</p><p>Li, et al., Multifactor colorimetric analysis on pH-indicator papers: an optimized approach for direct determination of ambient aerosol pH, Atmos. Meas. Tech. Discuss., https://doi.org/10.5194/amt-2019-394, in review, 2019.</p>

scholarly journals Multifactor colorimetric analysis on pH-indicator papers: an optimized approach for direct determination of ambient aerosol pH

2019 ◽  
Author(s):  
Guo Li ◽  
Hang Su ◽  
Nan Ma ◽  
Guangjie Zheng ◽  
Uwe Kuhn ◽  
...  
Keyword(s):  
Direct Determination ◽  
High Time Resolution ◽  
Colorimetric Analysis ◽  
Ph Indicator ◽  
Ambient Aerosols ◽  
Detection Range ◽  
Ambient Aerosol ◽  
In Situ Calibration ◽  
Wide Ph Range ◽  
Ph Range

Abstract. Direct measurement of the acidity (pH) of ambient aerosol particles/droplets has long been a challenge for atmospheric scientists. A novel and facile method was introduced recently by Craig et al. (2018), where the pH of size-resolved aerosol droplets was directly measured by two types of pH-indicator papers (pH ranges: 0–2.5 and 2.5–4.5) combined with RGB-based colorimetric analyses using a model of G − B (G minus B) versus pH2. Given the wide pH range of ambient aerosols, we optimize the RGB-based colorimetric analysis on pH papers with a wider detection range (pH ~ 0 to 6). Here, we propose a new model to establish the linear relationship between RGB values and pH: pHpredict = a × Rnormal + b × Gnormal + c × Bnormal. This model shows a wider applicability and higher accuracy than those in previous studies, and is thus recommended in future RGB-based colorimetric analyses on pH papers. Moreover, we identify one type of pH paper (Hydrion® Brilliant pH dip stiks, Lot Nr. 3110, Sigma-Aldrich) that is more applicable for ambient aerosols in terms of its wide pH detection range (0 to 6) and strong anti-interference capacity. The determined minimum sample mass (~ 180 μg) highlights its potential to predict aerosol pH with a high time resolution (e.g., ≤ 1 hour). We further show that the routinely adopted way of using pH color charts to predict aerosol pH may be biased by the mismatch between the standard colors on the color charts and the real colors of investigated samples. Thus, instead of using the producer-provided color chart, we suggest an in-situ calibration of pH papers with standard pH buffers.

scholarly journals Multifactor colorimetric analysis on pH-indicator papers: an optimized approach for direct determination of ambient aerosol pH

2020 ◽  
Vol 13 (11) ◽  
pp. 6053-6065
Author(s):  
Guo Li ◽  
Hang Su ◽  
Nan Ma ◽  
Guangjie Zheng ◽  
Uwe Kuhn ◽  
...  
Keyword(s):  
Direct Determination ◽  
Colorimetric Analysis ◽  
Ph Indicator ◽  
Particle Size Range ◽  
Ambient Aerosols ◽  
Detection Range ◽  
Ambient Aerosol ◽  
Custom Made ◽  
Wide Ph Range ◽  
Ph Range

Abstract. Direct measurement of the acidity (pH) of ambient aerosol particles/droplets has long been a challenge for atmospheric scientists. A novel and facile method was introduced recently by Craig et al. (2018), where the pH of size-resolved aerosol droplets was directly measured by two types of pH-indicator papers (pH ranges: 0–2.5 and 2.5–4.5) combined with RGB-based colorimetric analyses using a model of G−B (G minus B) vs. pH2. Given the wide pH range of ambient aerosols, we optimize the RGB-based colorimetric analysis on pH papers with a wider detection range (pH ∼ 0 to 6). Here, we propose a new model to establish the linear relationship between RGB values and pH: pHpredict = a⋅Rnormal+b⋅Gnormal+c⋅Bnormal. This model shows a wider applicability and higher accuracy than those in previous studies and is thus recommended in future RGB-based colorimetric analyses on pH papers. Moreover, we identify one type of pH paper (Hydrion® Brilliant pH dip stiks, lot no. 3110, Sigma-Aldrich) that is more applicable for ambient aerosols in terms of its wide pH detection range (0 to 6) and strong anti-interference capacity. Custom-made impactors are used to collect lab-generated aerosols on this type of pH paper. Preliminary tests show that, with a collected particle size range of ∼ 0.4–2.2 µm, the pH paper method can be used to predict aerosol pH with an overall uncertainty ≤ 0.5 units. Based on laboratory tests, a relatively short sampling time (∼ 1 to 4 h) is speculated for pH prediction of ambient aerosols. More importantly, our design of the impactors minimizes potential influences of changed environmental conditions during pH paper photographing processes on the predicted aerosol pH. We further show that the routinely adopted way of using pH color charts to predict aerosol pH may be biased by the mismatch between the standard colors on the color charts and the real colors of investigated samples. Thus, instead of using the producer-provided color charts, we suggest an in situ calibration of pH papers with standard pH buffers.

The Direct Determination of I131 in Heterogeneous Fecal Specimens

1961 ◽  
Vol 41 (4) ◽  
pp. 380-384 ◽  
Author(s):  
Arthur F. Dratz ◽  
James C. Coberly
Keyword(s):  
Direct Determination

A New Method for Direct Determination of the Recoilless Fraction with Application to Magnetic Nanoparticles

2002 ◽  
Vol 721 ◽  
Author(s):  
Monica Sorescu
Keyword(s):  
Room Temperature ◽  
Average Particle Size ◽  
Direct Determination ◽  
Average Particle ◽  
Lattice Method ◽  
Recoilless Fraction ◽  
Single Room ◽  
Magnetite Particles ◽  
Physical Mixtures

AbstractWe propose a two-lattice method for direct determination of the recoilless fraction using a single room-temperature transmission Mössbauer measurement. The method is first demonstrated for the case of iron and metallic glass two-foil system and is next generalized for the case of physical mixtures of two powders. We further apply this method to determine the recoilless fraction of hematite and magnetite particles. Finally, we provide direct measurement of the recoilless fraction in nanohematite and nanomagnetite with an average particle size of 19 nm.

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