I have studied the development of atmospheric gas determination systems
by flow analysis. The target gases are collected into
collection/reaction solutions then determined via conductivity,
fluorometry, or spectrophotometry. Some gases are determined during the
actual gas collection. Miniaturization of lab on chip gas collection
effected not only small reagent consumption but also high
collection/concentration efficiency. The systems I have developed have
been applied to field gas measurements at volcanic craters, septic
tanks and tidal flats.
Recently, I have studied breath gas analysis, fiber optic sensor for
atmospheric gases, urine analysis and capillary scale detection
techniques. The details are following.
Research Topics (Click each topic for jump)
scale fluorescence detector
Breath gas contains as many as ~3000 compounds. There is equilibrium between
breath gas and blood within the small capillaries in the lungs.
A clinical diagnosis can be
made based on the concentrations of some of the gases measured in a
breath sample, similar to the way in which blood alcohol measurements
are taken. Breath gas contains water vapor
(saturated at 37 °C), several % of CO2 and many other
components that cause difficulties in breath gas analysis. We have developed specific
sensors for the determination of ammonia, acetone, and isoprene.
Breath Isoprene Analysis
isoprene with an ozone-induced chemiluminescence (CL) method. Breath samples are collected
into a sample balloon and loaded onto a column which selectively retains any isoprene in the sample.
By doing this there was not
only a greatly increased sensitivity but many of the interferences
listed before can be avoided. Breath samples from
various people at various times of the day were collected and analyzed
for their isoprene concentration. The comparison of the results
from a gas chromatography (GC – FID/MS) method shows that our CL method has
reasonable agreement for the volunteers. (Analytical Chemistry,
Click figure for high-resolution pdf file.
The gases, which are invisible, are coming without recognize. Most of
them are hazard for our health. In the history, we had the terrible air
pollution problem (i.e. London smog (1952)). Atmospheric
gas analyses are interested not only for environmental pollution
monitoring but also for environmental science. Because atmospheric
gases play important roles in the natural elements cycles and so on.
Many kinds of trace gas analyzer (i.e. HCHO, NH3, SO2,
H2O2) were developed in our group. These are
ultra high sensitive (pert per billion (ppb) or pert per trillion (ppt)
levels gases can be detected.), portable, selective.
Optic Gas Sensor for Simultaneous NO2, O3 and
Relative Humidity Analysis
gas sensor was proposed for gas analysis. The surface of thin
layer chromatography (TLC) plate was used for gas collection and
reaction. The chemical, 8 – amino – 1 – naphthol – 5 – sulfonic
acid (ANS) was impregnated to TLC plate. This chemical responded
to NO2 and O3 with brown and pink color
generation, respectively. These color development was monitored
with 442 and 525 nm light emitted diodes (LEDs). Light
transmittance of TLC plate was changed by relative humidity,
also. This was monitored with infla-red LED (IR-LED).
Herein, fiber optic sensor for NO2, O3 and
relative humidity was developed and applied to real atmospheric
determination. The sensor can analyze part per billion levels of
NO2 and O3 gas with 5 min gas collection. (Analytical
for high-resolution pdf file
Parts per Million Levels of Gaseous NO2 by a Optical Fiber
Transducer Based on Calixarenes
Alkylated calixarenes has been demonstrated as novel NO2 gas
sensor. Upon reacting with gaseous NO2, alkylated
calixarenes form stable calixarene-NO+ (nitrosonium)
complexes that have a deep purple color. This specific and
selective formation of the colored complex was used to develop a fiber
optic based colorimetric NO2 sensor. For a 5 min
sample, the limit of detection was 0.54 ppmv with 1,3-alternate O-hexyl
calixarene. With calixarenes however, such a reaction is
potentially reversible - color formed upon reaction with NO2
can be reversed by flushing the sensing plate by purified air. While we
found that the removal of the developed color can be accelerated by
simultaneous heating and suction, permitting the reuse of the same
sensing area multiple times, we also observed that the sensitivity
gradually decreased. The nitrosonium calixarene derivative tends to
transform to the nitrated form; this process is catalyzed by light.
Several methylated calixarenes were synthesized and tested but a fully
satisfactory solution has proven elusive. (Talanta, in
for high-resolution pdf file
Urine is also strongly related with the condition of our body. Urine,
which is easily collected, has been analyzed for clinical diagnosis,
drug test and chemical exposure assessment for several decades.
However, urine concentrations are highly variable through time. These
are caused the amount of water intake, sweat and the properties of the
foods eaten. The effect of the concentration variation should be
corrected for urine analysis. There is the golden standard method
to solve the variation problems. It is called “Creatinine adjustment”.
Creatinine is a metabolic byproduct created from creatine, which is
related with the energy storage cycle of the muscles in our body.
Urinary creatinine has specific property as standard like enough amount
(~1.5 g/L), not interfered from biological factor and small variation.
Measurement of Urinary Creatinine
Rapid, low cost and accurate creatinine analysis system is proposed for
chemical assessment. Creatinine and alkaline picric acid develop
red-yellow dye (Jaffé reaction). Zone-fluidic analysis (ZF) was
combined with kinetic spectrophotometry to avoid urine color
interference. The system can analyze 72 times in one hour.
And obtained results are well matched with LC- UV / MS
methods. (Analytical Biochemistry, 2008.)
for high-resolution pdf file
of Creatinine Adjustment for Urinary Excretion in Lactating Mothers
Creatinine adjustment is widely used for
the estimation of 24 hr urinary excretion from spot urine
samples. We have compared creatinine adjustment values and real
24 hr values. Creatinine adjustment was applied to perchlorate,
iodine, selenium, and thiocyanate collected from lactating
mothers. Creatinine has been analyzed with automated analyzer,
which is described on above. Iodine and selenium was analyzed
with ICP –MS. Perchlorate and thiocyanate was analyzed with IC –
MS/MS. There were poor relationships between estimates and actual
measured. Also, I have collected all spot samples for 5 days in
series. Creatinine excretion and iodine excretion was not stable
because these were affected by the meal taken. (Environmental
Science and Technology, 2008.)
for high-resolution pdf file
Capillary Scale Fluorescence
There has been a
significant interest in capillary scale separation and detection
techniques during present decade. The capillary scale analysis
gave high and rapid separation efficiency with low reagent and
sample consumption. However, the detection techniques in this
scale have the difficulties because of low amount of analyte. We
have tried highly sensitive fluorescence detection with capillary
Scale Liquid Core Waveguide Based Fluorescence Detector for Liquid
Chromatography and Flow Analysis
Fluorescence detection technique is highly sensitive method for
chemical analysis. We have developed liquid core waveguide (LCW)
based capillary scale fluorescence detector. The fluorescence was
excited in Teflon AF coated capillary by high power UV-LED or “Blu-ray”
laser diode. Emitted light was transferred in the capillary to
the photo detector, like photodiode, miniature photo multiplier tube
(m-PMT). With “Blu-ray” laser diode (405 nm), the Coumarin-30 dye
was detected with 3 fmol of limit of detection (LOD). (Talanta,
for high-resolution pdf file
Kumamoto University, Japan, Ph. D (Science), 2005.
Kumamoto University, Japan, M. D. (Science), 2002.
Kumamoto University, Japan, B. D., 2000.
– 2008 JSPS Post Doctoral Research
Fellow for research abroad
2007 – 2008 University of Texas at Arlington
– 2006 JSPS Post Doctoral Research
Shin-Ichi Ohira, Eranda Wanigasekara,
Dmitry M. Rudkevich, Purnendu K. Dasgupta, “Sensing Parts per Million
Levels of Gaseous NO2 by a Optical Fiber Transducer Based on
Calixarenes”, Talanta, in print.
Shin-Ichi Ohira, Andrea B. Kirk, Purnendu
K. Dasgupta, “Automated Measurement of Urinary Creatinine by
Multichannel Kinetic Spectrophotometry”, Analytical Biochemistry, 384
(2), pp.238 – 244
Shin-Ichi Ohira, Andrea B. Kirk, Jason V.
Dyke, Purnendu K. Dasgupta, “Creatinine Adjustment of Spot Urine
Samples and 24 h Excretion of Iodine, Selenium, Perchlorate, and
Thiocyanate”, Environmental Science and Technology, 42 (24),
pp.9419 – 9423 (2008).
Purnendu K. Dasgupta, Andrea B. Kirk, Jason V. Dyke, Shin-Ichi
Ohira, “Intake of Iodine and Perchlorate and Excretion in
Human Milk”, Environmental Science and Technology, 42 (21),
pp.8115 – 8121 (2008).
Masanobu Mori, Tomotaka Iwata, Tatsuya Satori, Shin-Ichi Ohira,
Hideyuki Itabashi, Kazuhiko Tanaka, “Ion-Exclusion/Cation-Exchange
Chromatographic Determination of Common Inorganic Ions in Human Saliva
by Using an Eluent Containing Zwitterionic Surfactant”, Journal of
Chromatography A, 1213, pp.125 – 129 (2008). DOI:10.1016/j.chroma.2008.08.001
Song, Villanueva-Fierro Ignacio, Shin-Ichi Ohira,
Purnendu K. Dasgupta, “Capillary Scale Liquid Core Waveguide Based
Fluorescence Detector for Liquid Chromatography and Flow Analysis”, Talanta,
77 (2), pp.901 – 908 (2008). DOI:10.1016/j.talanta.2008.07.047
Sawalha, Mrinal K. Sengupta, Shin-Ichi Ohira, Ademola D.
Idowu, Thomas E. Gill, Lila Rojo, Melanie Barnes, Purnendu K. Dasgupta,
“Measurement of Soil/Dust Arsenic by
Gas-Phase Chemiluminescence”, Talanta, 77 (1), pp.372 –
379 (2008). DOI:10.1016/j.talanta.2008.06.037
Shin-Ichi Ohira, Kei Toda, “Micro Gas
Analyzers for Environmental and Medical Applications”, Analytica
Chimica Acta, 619 (2), pp.143 – 156 (2008).
Toda, Yuki Hato, Shin-Ichi Ohira, Takao Namihira, “Micro
Gas Analysis System for Measurement of Nitric Oxide and Nitrogen
Dioxide: Respiratory Treatment and Environmental Mobile Monitoring”,
Analytica Chimica Acta, 603(1), pp. 60 – 66 (2007).
Jianzhong Li, William A. Lonneman, Purnendu K. Dasgupta, Kei Toda, “Can
Breath Isoprene be Measured by Ozone Chemiluminescence?”, Analytical
Chemistry, 79(7), pp. 2641 – 2649 (2007).
(Accelerated articles) DOI: 10.1021/ac062334y
Kiyoshi Someya, Kei Toda, “In situ Gas Generation for Micro Gas
Analysis System”, Analytica Chimica Acta, 588(1), pp.
147 – 152 (2007). DOI:10.1016/j.aca.2007.01.069
Toda, Shin-Ichi Ohira, Yu-ki Hato, Takao Namihira,
“Sequential Multiple Analyses of Atmospheric Nitrous Acid and Nitrogen
Oxides”, Talanta, 71(4), pp. 1652 – 1660 (2007).DOI:10.1016/j.talanta.2006.07.054
Abul Kalam Azad, Shin-Ichi Ohira, Kei Toda, “Single
Column Trapping/Separation and Chemiluminescence Detection for On-Site
Measurement of Methyl Mercaptan and Dimethyl Sulfide”, Analytical
Chemistry, 78 (17), pp. 6252 – 6259 (2006). DOI :10.1021/ac060928v
Kei Toda, “Ion Chromatographic Measurement of Sulfide, Methanethiplate,
Sulfite and Sulfate in Aqueous and Air Samples”, Journal of
Chromatography A, 1121 (2), pp. 280 – 284 (2006).
Md. Abul Kalam Azad, Rika Kuraoka, Takayoshi Tanaka, Kotaro Mori, Kei
Toda, “Long-term and Mobilic Monitoring of Atmospheric Sulfur Dioxide
and Hydrogen Sulfide at Mt. Aso and Kumamoto City”, Bunseki Kagaku,
55 (2), pp. 109 – 116 (2006). (Written in Japanese) DOI :10.2116/bunsekikagaku.55.109
“Study on the Measurement of Atmospheric Gaseous Sulfur Compounds by
means of Miniature Diffusion Scrubbers”, Bunseki Kadgaku, 55
(1), pp. 61 – 62 (2006). (Written in Japanese) LINK
Kei Toda, “Miniature Liquid Flow Sensor and Feedback Control of
Electroosmotic and Peumatic Flows for a Micro Gas Analysis System”,
Analytical Sciences, 22 (1), pp. 61 – 65 (2006).
Toda, Shin-Ichi Ohira, Md Abul Kalam Azad, “Portable
Instrument for On-site Measurement of Odorous Sulfur Gases”,
Proceeding of 2nd International Conference on Environmental Science and
Technology, 2006(1), pp. 485 – 489 (2006). LINK
Namihira, Shunsuke Sakai, Koji Matsunaga, Douyan Wang, Tsuyoshi Kiyan,
Hidenori Akiyama, Kazuhumi Okamoto, Shin-Ichi Ohira, Kei
Toda, “Temperature Measurement of Pulsed Arc Discharge”, Proceedings
of 16th International Conference on Gas Discharges and their
Applications, Xi'an, China, 2, pp. 657 – 660 (2006).
Kei Toda, “Micro Gas Analysis System for Measurement of Atmospheric
Hydrogen Sulfide and Sulfur Dioxide”, Lab on a Chip, 5
(12), pp. 1375 – 1379 (2005). DOI :10.1039/b511281h
Abul Kalam Azad, Shin-Ichi Ohira, Mitsutomo Oda, Kei
Toda, “On-site Measurements of Hydrogen Sulfide and Sulfur Dioxide
Emissions from Tidal Flat Sediments of Ariake Sea, Japan”, Atmospheric
Environment, 39 (33), pp. 6077 – 6087 (2005). DOI
Kei Toda, Shin-Ichi
Ohira, Misuzu Ikeda, “Micro-Gas Analysis System
(µGAS) Comprising a Microchannel Scrubber and a Micro-Fluorescence
Detector for Measurement of Hydrogen Sulfide”,
Analytica Chimica Acta, 511(1), pp. 3 – 10 (2004).
Toda, Shin-Ichi Ohira, Takayoshi Tanaka, Tomohiko
Nishimura, Purnendu K. Dasgupta, “Field Instrument for Simultaneous
Large Dynamic Range Measurement of Atmospheric Hydrogen Sulfide,
Methanethiol and Sulfur Dioxide”, Environmental Science and
Technology, 38 (5), pp. 1529 – 1536 (2004). DOI: 10.1021/es034450d
Toda, Ken-Ichi Yoshioka, Shin-Ichi Ohira, Jianzhong Li,
Purnendu K. Dasgupta, “Trace Gas Measurement with an Integrated Porous
Tube Collector/Long-path Absorbance Detector” Analytical Chemistry,
75 (16), pp. 4050 – 4056 (2003). DOI: 10.1021/ac0341719
Kei Toda, Shin-Ichiro Ikebe, Purnendu K. Dasgupta, ”Hybrid
Microfabricated Device for Field Measurement of Atmospheric Sulfur
Dioxide”, Analytical Chemistry, 74 (22), pp. 5890 –
5896 (2002). DOI:
Toda, Purnendu K. Dasgupta, Jianzhong Li, Gary A. Tarver, Gregory M.
Zarus, Shin-ichi Ohira, “Measurement of Atmospheric
Hydrogen Sulfide by Continuous Flow Fluorometry”, Analytical
Sciences, 17, pp. i407 – i410 (2001). LINK
Toda, Hiroshi Inoue, Shin-Ichi Ohira, Isao Sanemasa,
“High Sensitive Micro Detector for Sulfur Dioxide”, Ryusan to Kogyo
, 52 (10), pp. 129 – 134 (1999). (Written in Japanese)
Prof. Kei Toda (Kumamoto
The Japan Society for