Journal Critique
Citation:
Chanla, J., Kanna, M., Jakmunee, J., & Somnam, S. Application of Smartphone as a Digital
Image Colorimetric Detector for Batch and Flow-based Acid-Base Titration. Chiang Mai Journal
of Science 46, 5 (Sep 2019), 975 - 986.
Subject Key words
RGB color system, RGB color picker application, indicators, spectrophotometer, pH meter,
titrimetric analysis, equivalence point, endpoint
Research question and hypothesis:
This research focused on the advantages of mobile phone or digital imaging as RGB detector
compared to spectrophotometer and pH meter and its accuracy in batch and flow-based system of
titrimetric analysis. The accuracy, advantages and the ways of using this in determining of acid
and base in various beverages were discussed. Therefore, the scientific question could be, “Is
mobile phone was accurate for detecting RGBs in batch and flow-based system of titrimetric
analysis?” this could be the scientific question as the author of the journal said that it was already
used as an alternative in many analytical measurements and the author suggesting in the end, that
this was accurate and has its advantages in determining acid and base in various beverages
despite the colored sample/real sample. The hypothesis was then carried out by using a highresolution camera with an RGB detector application downloaded to it and by doing various
experiments with it in different samples and then the result was compared to the result of pH
meter and spectrophotometer to prove its accuracy.
Experimental strategy, with materials and methods:
The chemicals that were used by the researchers were freshly prepared de-ionized water and
analytical grade chemicals. KHP and Na2CO3 were used for standardization procedure. 0.1
NaOH was standardized to be used as titrant for the titration of strong acid HCl and weak acid of
CH3COOH. And determination of CH3COOH in vinegar and acidity in juice were also included.
And titration curve of strong acid-weak basic was also done with HCl and NH3 solution. And for
the total alkalinity in water samples, standardization of H2SO4 were used as a titrant. And the
indicators that was used were bromothymol blue, methyl orange, methyl red and
phenolphthalein. Then different buffer solutions at each pH were used to see color change.
The method that was done in titration here were just like what was done in school where there
will be a burette (where titrant were placed), beaker (where titrand were placed) and a stirrer. But
the difference is that there will be an RGB detection box and a technique to be followed which
was the flow-based technique. In RGB detection box, the materials that will be used was a wood
for the box that have the measurement of 10cm x 11cm x 17cm (to avoid ambient light) with a
white paper inside (to provide uniform illumination) and 2.0 cm radius of hole (in front of test
tube that were placed inside the box) for the camera of the phone, a light bulb attached at the top
of the box (to provide light), and a clamp to hold the smartphone. And for the flow-based
technique, a PTFE tubing will be used with a flow rate of 5mL/min using peristaltic pump. This
technique were used to avoid leakage during chemical transfer from beaker to test tube (inside
the detection box) then back to beaker). The way it works is that after the transfer of chemical
from beaker to test tube the tube will be stop then the smartphone will capture its RGB values
using its camera with flash and with the application downloaded free from the PlayStore in
android (RGB color picker) then back to beaker again. The result were compared to the result of
spectrophotometer and pH meter to see accuracy.
For real samples, vinegar and juices. A distilled vinegar and four brands of fruit juice were
prepared. The known volume (1.00mL) of vinegar was pipetted to make a ten-fold dilution. The
juices were filtered through filter paper before pipetted at 10.00mL of sample for titration. Three
drops of phenolphthalein were added to prepared samples and then titrated with a standardized
NaOH. RGB detection were then carried out. And then the result were compared to the result of
pH meter and spectrophotometer. For determination of alkalinity, three brands of mineral water
were bought. Three drops of methyl orange were added to 100.0mL of each sample. Standard
solution of 0.0100 N H2SO4 was used as the titrant. Then RGB detection were carried out. Then
the result were compared to the result from photometric titration using spectrophotometer as the
RGB detector.
CRITIQUE:
The flow of methods was confusing to follow as the methods are broken down randomly. I think
it would be a lot better to follow if the materials that was used and the methods that was done
were separately discussed and arranged in a more uniform way.
Results:
> Table 2, Page 980. In this table, three titration were made to evaluate the accuracy of RGB
detection. And the result will then be compared to the results of potentiometric titration.
> Figure 4, Page 981. This figure shows the result of RGB detection using the smartphone in
three titration done as shown in table 2, page 980. And the result shows the right equivalence
point and endpoint compared to the second derivative that was shown in figures 5-7, page 983984. And therefore, this result suggested that using smartphone as RGB detector was effective
for acid-based titration (not yet for real samples).
> Table 3, Page 984. This table shows the similarity of results of RGB-detection box with pH
meter and Spectrophotometer. And the result shows that the RGB-detection box was also
effective to use to the acid-base titration for the colored sample/real samples (Vinegar and
Juices).
> Table 4, Page 985. This table shows that smartphone as RGB detector in seeing the alkalinity
of a mineral water was also accurate and effective.
CRITIQUE:
The result clear and was in line with what was shown in the methods. It shows accuracy of the
result. Therefore, the result shows relevance and it shows that it was connected with what was
concluded in abstract and in conclusion.
Discussion and Conclusion:
This journal relates in other medical field as it tackles about acid-base titration which was
commonly used in medical field. The key issue here is that smartphone as RGB detector for
batch and flow-based acid-base titration was not used despite its advantages and almost similar
accuracy compared to spectrophotometer and pH meter. It ties with the findings of others as they
stated that mobile phone was already used as an alternative in many analytical measurements and
this pushed the researchers of the journal to test it also for detecting RGBs using the flow-based
technique. The significance of this study is that it tackled about many advantages of using mobile
phone as RGB detector. Stating that it was concise (based on the results in the experiments),
portable, inexpensive, fast and cheap in analysis. And with this knowledge, it would make future
analysis of acid and base RGBs a lot better and affordable as they can improve this known
method further more to the point it will leveled with the result that you will get using the
spectrophotometer (which was more expensive).