The purpose of this review is to describe definitions, estimation and applications about figures of merit to represent uncertainty of measurements in instrumental analyses, among which are limits of detection, decision and quantitation, and precision profiles, adopted in ISO 11843-7, JIS Z 8462-7 or Japanese Pharmacopoeia. These quantities are illustrated by some examples: absolute calibrations, internal standard methods, isocratic elution and gradient elution of liquid chromatography, and daily inspections of gas chromatography-mass spectrometry systems. Standard deviations (SDs) of measurements underlie the above concepts and a method for estimating the SDs which can obviate the need for repetition of measurements with real samples is briefly explained. The above examples are analyzed with available computer software.

Amperometric flow injection analysis (FIA) biosensors were developed by using various biomolecules-modified carbon felt (CF) as a working electrode unit of flow-through electrochemical cell-based FIA detector. The CF is a micro-electrode ensemble of micro-carbon fiber (ca. 7 μm diameter) that possesses a three-dimensional random structure. The CF has high conductivity and a large effective surface area, which allows large measurable current density and high electrolytic efficiency. In addition, a high porosity of CF (> 90 %) permits a low diffusion barrier of solution-flow. Four enzymes (tyrosinase, peroxidase, glucose oxidase, uricase), heme proteins (myoglobin, hemoglobin) and hemin were immobilized on the CF surface by chemical modification and physical adsorption. The developed FIA biosensors are divided into the following categories: 1) Tyrosinase (polyphenol oxidase)-modified CF for highly sensitive amperometric flow determination of phenol and catechol compounds, based on signal amplification due to the enzymatic/electrochemical redox recycling; 2) Peroxidase-modified CF for the amperometric flow determination of H₂O₂ based on direct electron transfer (DET)-based bioelectrocatalysis; 3) Oxidases (glucose oxidase and uricase)-modified CF-based enzyme reactors coupled with peroxidase-CF for amperometric flow determination of glucose and uric acid; 4) Hemin-modified CF for amperometric flow determination of dissolved oxygen (DO), based on an electrocatalytic activity of hemin for the reduction of DO; 5) Heme-proteins-modified CFs for the amperometric flow determination of respiratory toxins (N₃⁻ and CN⁻), based on reversible inhibition of toxins on bioelectrocatalytic activity of heme-proteins for the reduction of DO. These FIA biosensors do not need any indication reagents, sample-pretreatment and column separation, because biomolecules immobilized on the CF surface possesses highly selective bio-specificity and specific bio-affinities, which allows simple and consecutive analysis of many samples. Therefore, in future, these FIA biosensors can be expected to be applied to on-line automated analysis systems coupled with advanced IoT and AI technology.

In the conventional multiphase flow, immiscible multiphase flow, having a liquid-liquid interface, two immiscible liquids are merged in the flow path to form a liquid-liquid interface. The two-phase separation mixed solution has the property of phase-separating from one phase to two phases by changing the temperature/pressure, and phase-separates into the upper and the lower phases in the batch-type vessel. By changing the phase while sending this mixed solution to a micro-space region, a liquid-liquid interface is formed and a multiphase flow is obtained. This flow is called phase-separation multiphase flow. The circular flow in the micro-space, which is one of the phase-separation multiphase flows, is interesting and has been applied to chromatography, extraction, mixing, and reaction space. Here, the author comprehensively introduces our previous research reports on phase-separation multiphase flow from an academic and technical perspective.

In recent years, research on mid-infrared plasmonics, which enables qualitative and quantitative analyses of substances by vibration spectroscopy, has been studied all over the world. We have developed new plasmonic materials for constructing a breakthrough mid-infrared sensor, such as new alloy materials based on dielectric permittivity analysis for plasmonic materials, surface enhanced infrared absorption (SEIRA) with a transmissive plasmon material, metal hole array (MHA), and metal-insulator-metal nanostructure (MIM) type meta-surface structure for the mid-infrared light source/detector. This comprehensive paper summarizes the global trends of these plasmonic materials and our researches.

Recently, many three-dimensional tissue models (Organ-on-a-chip devices) that mimic the human cellular microenvironment have been developed. Because blood vessels are exposed to blood flow, their in-vivo functions cannot be evaluated with the conventional static mono-culture of vascular endothelial cells. Therefore, the development of microvascular models is particularly important. The microvascular model has a structure that mimics tissue composed of multiple types of cells, as opposed to a single type of cells cultured under static planar conditions, and can be used for bioassays with mechanical stimulation. Here, I introduce the author's past study in the development of bioassay devices for vascular and lymphatic permeability and absorption, pulmonary hypertension microdevices, and blood cell differentiation microdevices, and their applications to bioanalytical chemistry.

The epidermal growth factor receptor (EGFR) T790M mutation, a missense mutation from CpG cytosine to thymine, in non-small cell lung cancer is a drug-resistant mutation induced by the administration of tyrosine kinase inhibitors (TKIs). It is important to detect this mutation with high sensitivity, as effective therapies have been developed for patients with this mutation. We confirmed that cytosine at this mutation point is methylated in various tissues, and the 5-methylcytosine is readily deaminated by hydrolysis and converted to thymine, which is detected as an artifact. We have developed a new method to estimate the artifact in formalin fixed paraffin-embedded (FFPE) specimens by evaluating a mutant ratio of other 5-methylcytosine, enabling sensitive and accurate detection of the T790M mutation.

We proposed a high-throughput screening method for the interaction between metal ions and drugs using an ion-selective electrode (ISE). This method is based on measuring of the decrease in the potential response for residual free ions resulting from interactions with drugs. The home-made device with an electrode cell (cell volume: 500 μL) enabled us to measure an adequate potential response and to wash the electrode in a simple and quick operation. The method was applied to investigating the interaction behaviors between metal ions and fifty-seven drugs. By optimizing the concentrations of metal ions, drug and buffer solution, we were able to screen 44 drugs for interactions with Cu²⁺ and 13 drugs for interaction, with Ca²⁺ at pH 7.4. There are no limits to target drugs because this method measures only free-metal ions, i.e., a highly versatile method. The advantages of our method potentially provide new knowledge which is useful in the fields of biochemistry, pharmacology and drug discovery.

A sensing membrane for selenium(IV) was fabricated by retaining tris(2,4-pentanedionato)gallium(III) (Ga(acac)₃) in a glass-fiber filter. From a sample solution containing selenium(IV), gaseous hydrogen selenide was generated by reducing-vaporization and was passed through the membrane while turning the color to reddish pink. The color difference (ΔE*(ab)) before and after the reaction was measured by a reflection spectrometer. The ΔE*(ab) value increased with the increase of the selenium(IV) concentration. From the reflective spectra of reacted membranes; gallium(III) selenide (Ga₂Se₃) was suggested to be formed. Most of the coexisting cations showed no significant interference to the reaction, besides a large amount of arsenic(V) and antimony(III) suppressed the color change. Since adding iron(II) salt resulted in enhancing the color difference, 10 mg dm⁻³ of iron(II) was used as an accelerating additive. In order to investigate the influence of ligands in gallium(III) complexes, several gallium(III) compounds were retained in a filter, and examined as sensing materials. The complexes of β-diketones and dithiocarbamates had appropriate sensing activity, while inorganic salts, like gallium(III) sulfate or nitrate, showed no color change. This suggests that ligands having larger pKa values are effective for the reaction. The complexes of monobasic, dibasic and tribasic carboxylic acids showed decreased color differences in this order, and those of multidentate ligands, e.g., EDTA, exhibited no color change. These results showed excessively stable gallium(III) complexes have no reactivity to hydrogen selenide. Visual detection of 0.01 mg dm⁻³ selenium(IV) was achieved in the presence of 10 mg dm⁻³ iron(II) in a 50 cm³ sample solution.

A closed lipid bilayer membrane with a diameter of one micrometer or more in water is called as giant vesicle and it is attracting attention as a cell mimicry reaction space because its structure and size are similar to those of living cells. When utilizing giant vesicles from a cell model perspective, biomolecules are needed to be encapsulated inside giant vesicles under conditions close to the cytoplasm. In recent years, the development of this encapsulation technology has been accelerating. The origin of this trend is a preparation method of giant unilamellar vesicles using a water-in-oil emulsion, published by a research group at Harvard University in 2003. The preparation method can only be performed on a desktop centrifuge. Here, we report on the experimental results of this preparation method using different oil for the water-in-oil emulsion.