Hitoshi Watarai
Institute for NanoScience Design, Osaka University, Toyonaka, Osaka, 560-8531, Japan e-mail: watarai@chem.sci.osaka-u.ac.jp
In modern analytical chemistry, the analysis of microparticles and interface is important subject due to the requirements from various fields of bio-science, environmental chemistry and nano-technology [1]. Here, I would like to introduce recent development of new magneto-analytical chemistry, which aims to create novel detection, separation and imaging methods of microparticles by applying various types of magnetic fields. Also, some topics in chiroptical analysis of liquid-liquid interfaces will be introduced.
1. Magnetophoretic analysis of microparticles
The migration velocity of micropaticles and microdroplets in liquid media under the magnetic field gradient has been developed as the magnetophoretic velocimetry. The analysis of the migration velocity afforded us the magnetic susceptibility of the particle and the interfacial magnetic susceptibility of the particles as well. From the interfacial magnetic susceptibility, the interfacial concentration of a paramagnetic ion on a single particle was absolutely determined [2].
2. Magnetic force mass analysis in atmospheric condition [3]
Mass spectrometry (MS) always requires sample molecules to be ionized. We have developed a new principle of MS, which needs no ionization, since it utilizes a magnetophoretic modulation on falling particles in an atmospheric condition. The magnetic mass analysis can provide the magnetic susceptibility and the mass of a single microparticle, simultaneously.
3. Dynamic force analysis of chemical bonding [4] and chemical equilibria [5]
Magnetic or electromagnetic force was used to pull molecules bound to a microparticles and capillary or glass wall as linker molecules. The dissociation or conformational change of the linker molecules was measured by optical microscope or
SERS spectra, and the bond dissociation dynamics and conformational equilibria were evaluated.
4. Faraday rotation imaging of chiral liquids
The analytical application of Faraday rotation to make a new imaging technique has been investigated using pulsed magnetic field [6]. The Faraday rotation imaging method can provide the optical images due to the magnetic susceptibility, the σ-electron and
 electron percentages, and the natural optical chirality of the samples.
5. Chiroptical analysis of molecular aggregates at liquid-liquid interfaces
Characteristic features of liquid-liquid interfaces were utilized for the development of chiral analysis of diluted interfacial active analytes, chiral alcohols, by using a centrifugal liquid membrane/circular dichroism method.
[1] H. Watarai, M. Suwa and Y. Iiguni, Anal. Bioanal. Chem.
, 378 (2004)1693.
[2] M. Suwa and H. Watarai, Anal. Sci.
, 24 (2008) 133.
[3] M. Arase, M. Suwa and H. Watarai, Anal. Chem.
, 78 (2006) 6660.
[4] Y. Iiguni and H. Watarai, Analyst , 135 (2010) 1426.
[5] T. Goto and H. Watarai, Langmuir , 26 (2010) 4848.
[6] K. Miyamoto, K. Isai, M. Suwa and H. Watarai, J. Am. Chem. Soc.
131 (2009) 6328.