Takashi Miyazaki

Determination of bromperidol in serum by automated column-switching high-performance liquid chromatography

A column-switching high-performance liquid chromatographic method with ultraviolet detection is described for the simple and rapid determination of bromperidol, a neuroleptic drug, in dog and human sera. The drug in serum and trifluperidol added to the serum as an internal standard were extracted with hexane-chloroform, and the extract was subjected to automated column-switching high-performance liquid chromatography using a hydrophilic metaacrylate polymer column (TSK gel PW precolumn) for sample clean-up and a reversed-phase column (TSK gel ODS-80TM) for separation. The detection limit of bromperidol is 0.3 ng/ml serum and the recovery of bromperidol added to serum (2.7-16.0 ng/ml) was satisfactory with a standard deviation of 3% or less.

High-performance liquid chromatography of guanidino compounds using benzoin as a pre-column fluorescent derivatization reagent

Abstract A high-performance liquid chromatographic method is described for the simultaneous separation of nine guanidino compounds of biological importance. Guanidino compounds are converted into the corresponding fluorescent derivatives by reaction with benzoin, and separated within 25 min on a reversed-phase column, μBondapak Phenyl, with linear gradient elution using aqueous methanol containing a Tris—hydrochloric acid buffer (pH 8.5). The method is simple, rapid and sensitive; the lower limits of detection for the guanidino compounds are 20–100 fmol in a 100-μl injection volume.

High-performance liquid chromatographic measurement of guanidino compounds of clinical importance in human urine and serum by pre-column fluorescence derivatization using benzoin

High-performance liquid chromatographic microanalyses for guanidino compounds in human physiological fluids have been accomplished by means of a pre-column fluorescence derivatization method using benzoin. The guanidino compounds in urine or deproteinized serum after ultrafiltration are converted to the fluorescent derivatives with benzoin in an alkaline medium, and the derivatives are separated simultaneously within 25 min on a reversed-phase column (mu Bondapak Phenyl) with a linear gradient elution of methanol in aqueous mobile phase (pH 8.5). The method permits the quantitative determination of guanidinosuccinic acid, methylguanidine, taurocyamine and guanidinobutyric acid at concentrations of as low as 8-78 pmol/ml in human urine and serum.

Highly Sensitive Magnetic Nanoparticle Imaging Using Cooled-Cu/HTS-Superconductor Pickup Coils

We developed a highly sensitive measurement system of ac magnetic fields for magnetic nanoparticle imaging (MPI). First, we developed a detection system using pickup coils made of cooled Cu Litz-wire and high-critical-temperature superconductor (HTS) tape. The pickup coils were connected to a resonant capacitor in order to enhance the signal voltage generated in the pickup coils. The magnetic field noise at the resonant frequency of about 9 kHz was as low as 13 fT/Hz1/2 and 12 fT/Hz1/2 for the Cu and HTS coils, respectively. Next, we demonstrated the detection of nanoparticles using the cooled Cu coil and the third harmonic signal generated by the nonlinear magnetization of nanoparticles. An excitation field having a frequency of 3 kHz and root mean square value of 1.6 mT was applied to the magnetic particles, and the third harmonic signal at 9 kHz was detected that reduced the interference from the excitation field. We demonstrated the detection of 100 μg of magnetic nanoparticles. We obtained a clear contour map of the magnetic field from the particles, and could detect the particles located as far as 100 mm under the pickup coil.

Determination of renin activity in human plasma by column-switching high-performance liquid chromatography with fluorescence detection.

A column-switching high-performance liquid chromatographic (HPLC) method with fluorescence detection is described for the determination of the renin activity in human plasma. The method is based on the quantification of the enzymatically produced angiotensin I. Angiotensin I liberated from a synthetic substrate (tridecapeptide of human angiotensinogen) and [Val5]-angiotensin I as an internal standard are converted into fluorescent derivatives by reaction with benzoin. The derivatives are separated from various interfering substances by column-switching HPLC using three reversed-phase columns. The limit of detection (signal-to-noise ratio = 3) of the renin activity is 2.7 pmol of angiotensin I formed per h per ml of plasma, which corresponds to approximately 820 fmol of angiotensin I injected. The column-switching method in combination with pre-column derivatization for the fluorimetric detection permits the sensitive and selective determination of the enzymatically formed angiotensin I. Hence low activities of renin in normal human plasma are readily measured.

Sensitive assay for serum angiotensin-converting enzyme and separation of angiotensin analogues by high-performance liquid chromatography with fluorescence detection

A high-performance liquid chromatographic method is described for the assay of angiotensin-converting enzyme in human serum and for the separation of angiotensins and their analogues after pre-column fluorescence derivatization with benzoin. Angiotensin II, formed enzymatically from angiotensin I, is converted into a fluorescent derivative which is then separated isocratically from the substrate and biological substances in the enzyme reaction mixture on a reversed-phase column (TSK gel ODS-120T). The lower limit of detection for angiotensin II is 0.66 pmol per enzyme assay tube. The method is simple and sensitive, and requires as little as 5 microliter of human serum. Angiotensin analogues can also be separated and quantified by the chromatographic technique, and thus this method permits the use of the analogues of angiotensin I as substrates.

Well-type NaI(Tl) spectrometry for quantitative analysis of 244Cm leached from curium-doped synroc

Abstract The count rates in the 42.8-keV peak of 244Cm are integrated from 32.0 to 52.5 keV, and the net area under this peak is computed. The 244Cm activity is obtained by multiplying this area with the calibration factor, which is measured as a function of the volume of the curium solution. In the static leach test at 90°C, the normalized curium-leach rate does not vary significantly with time, and averages 1.1 × 10−3 g m−3 day−1 with an estimated total uncertainty of 75%.

Narrowband magnetic nanoparticle imaging using cooled pickup coil and gradient field

Magnetic particle imaging (MPI) has been extensively studied for in-vivo biomedical diagnosis. We developed a narrowband MPI system utilizing third harmonic detection. The third harmonic signal from the magnetic nanoparticles (MNPs) was detected with a pickup coil cooled to 77 K, and its output was read out with a resonant circuit. The noise of the detection system was fT/Hz1/2 at a signal frequency of 8.79 kHz. We also introduced the so-called gradient field with a field gradient of 0.3 T/m in order to improve the MPI spatial resolution. We first clarified the properties of MNPs, which provided the basis for MPI using the gradient field. Next, we measured the signal-field map generated from the MNPs when an excitation field with a root mean square value of 1.6 mT and frequency of 2.93 kHz was applied. Using a mathematical technique called singular value decomposition (SVD), we reconstructed an image of the MNP distribution from the measured map. We demonstrated the detection of MNP samples as small as 1 µg at a distance of 50 mm. The spatial resolution of the reconstructed MNP distribution was approximately 10 mm. These results will indicate the feasibility of the system for the application to breast cancer detection.

Characterization of InGaAs Phosphidized by a Plasma Process

Phosphidization of InGaAs is attempted using a remote phosphine plasma. Au Schottky junctions are formed on the phosphidized and Ar-plasma-treated InGaAs layers and their electrical properties are characterized. Traps are investigated by isothermal capacitance transient spectroscopy measurements. Two electron traps are detected and designated as E1 and E2. The energy levels of the E1 and E2 traps are 0.35 eV and 0.48 eV below the conduction band edge, respectively. In the case where InGaAs is treated with PH3-added Ar plasma, a significant reduction in the densities of both E1 and E2 traps occurs in comparison with those of Ar-plasma-treated InGaAs. It is found that phosphorus atoms are effective in suppressing the generation of electron traps in InGaAs.