The feasibility of the optical monitoring of biological fluids, for example, albumin in serum, in a microfabricated silicon flow cell has been demonstrated. This module couples a fiber-optic reflection probe (one emitting fiber and six receiving fibers) to a small-volume silicon flow-cell (in µl range) for reflection-absorption measurements. The coupling efficiency of light between the optical fibers in such a system has been calculated (7.07%), and its optimum values (19.5% - 19.6%) as a function of the cover glass thickness and the silicon channel depth predicted.
A sensitive method was developed for the capillary electrophoretic determination of I(VII). In a 5×10-2 M malonate buffer solution (pH 4) containing low concentrations of I(VII) and 1×10-2 M Mo(VI), a stable [IMo6O24]5- complex was formed at room temperature. Since the heteropoly anion showed an approximately eight-fold increase in the molar-absorption coefficient than the free IO4- anion, the complex-formation reaction was applied to the sensitive capillary electrophoretic determination of I(VII) with UV detection at 220 nm. A simultaneous determination of I(VII) and I(V) was also possible, since both peaks due to [IMo6O24]5- and IO3- were well-separated in the electropherogram. For I(VII) and I(V), linear calibration curves were obtained in the concentration ranges of 2×10-6 - 2×10-4 M and 5×10-5 - 2×10-3 M, respectively.
The multielement determination of major-to-ultratrace elements in river sediment reference material (NIES No.16) and marine sediment reference material (NIES No.12) was investigated by inductively coupled plasma atomic emission spectrometry (ICP-AES) and inductively coupled plasma mass spectrometry (ICP-MS). The sediment samples were decomposed by alkali fusion with lithium metaborate (LiBO2) in a platinum crucible, and the residues were dissolved in 1 M nitric acid. The digested sample solutions were subjected to the analysis by ICP-AES and ICP-MS after appropriate dilution. In consequence, 42 elements were determined over a wide concentration range, for example, from Si 23.8% to Lu 0.29 µg g-1 in the case of marine sediment reference material.
A sensitive and rapid method for electrothermal vaporization-inductively coupled plasma atomic emission spectrometry (ETV-ICP-AES) determination of La3+ and Eu3+ after separation/preconcentration by a micro-column packed with immobilized 1-phenyl-3-methyl-4-bonzoyl-5-pyrazone (PMBP) on microcrystalline naphthalene has been developed. Various influencing factors, such as the acidity of the aqueous solution, flow rate, volume of the sample, dimension of the micro-column on the separation and the preconcentration of the analyte, have been studied, and the working parameters were optimized experimentally. The choice of the solvent for dissolving the concentrated material and the effects of diverse ions have also been discussed in detail. The detection limits for ETV-ICP-AES determinations of La and Eu with PMBP as a chemical modifier are 160 pg and 30 pg, respectively, under optimized experimental conditions. Relative standard deviations of 4.2% and 3.1% have been obtained after eight replicate determinations at the 10 ng/ml level for La and Eu, respectively. The La and Eu contents in the standard reference material of “Vehicle Exhaust Particulates” (NIES No.8) and “Citrus Leaves” (NIST SRM 1752) determined by the proposed method are in good agreement with the reference values.
The concentrations of all rare-earth elements (REEs: La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu) in oceanic basalt glasses were measured by an ion-microprobe method. A resolving power of 9300 at 1% peak height was attained by an ion-source slit set at 60 µm and a collector slit at 50 µm; the accelerating voltage was 10 kV for secondary ions in order to separate heavy REEs from the oxides of light REEs with adequate flat-topped peaks. Using NIST SRM612 glass (which is doped with ∼50 ppm of all REEs), the transmission of secondary ion was estimated to be about 30% and a sensitivity of 10 cps/ppm 171Yb/1nA O2- was obtained. A background level of 0.3 cps (at 3σ) coupled with the sensitivity suggests a detection limit of ∼6 ppb for glass matrix samples. The secondary ion yields of REEs (A+/Ba+) are consistent with those (A+/Ca+) in the literature. The observed contents of REEs in oceanic basalt glasses agree well with those measured by ICP-MS after chemical dissolution within a 10 - 20% error, except for La, Ce and Pr. The discrepancy of the light REEs is attributable to unresolved interference into mass numbers 139, 140 and 141, which may cause an excess abundance of each element. The contents of La, Ce and Pr were corrected by an empirical relationship between the relative intensity of mass number 124 and the excess of elements.
Scanning electrode quartz crystal analysis (SEQCA) in the back-scanning mode is described. Although qualitative map-ping of the mass distribution on a quartz plate is possible in air or non-conducting liquids by means of SEQCA in the fore-scanning mode, mapping is difficult in an electrolyte solution (e.g. ≥10 mM NaCl), which behaves as an electrode due to its ionic conductivity. On the other hand, because the back-scanning mode does not suffer from the ionic conductivity of a solution, mapping is possible even in a 0.1 M NaCl solution. This technique is applied to electrochemical measurements. An electrode on a quartz plate is partially masked, and polypyrrole is deposited on the bare region by electropolymerization from an electrolyte solution containing pyrrole. The deposited polypyrrole can be located in the elec-trolyte solution by means of SEQCA in the back-scanning mode.
The electrochemiluminescence (ECL) of N-(4-aminobutyl)-N-ethylisoluminol (ABEI) in a hydrogen peroxide solution was investigated by electrochemical techniques in the frequency domain. Parallel Pt wire electrodes in a flow-type spiral cell were used for ECL measurements. A superoxide ion, O2-, was generated by electrooxidation on Pt, and ABEI fluo-resced by a reaction with O2-. An ECL impedance L, which is the ratio of the luminescence amplitude to the current in the frequency domain, is proposed in the present paper. The theoretical expression of L was derived to be L=a1/(1+j w/k), where a1 is a constant and k is the reaction rate constant of ABEI and O2-. By comparing the above equation with the experimental results, the rate constant k was determined.
The extraction properties and the selectivity of silica modified with zirconium phosphate (SiZrP) and propylimidazol (SiIm) for cadmium, lead and mercury were evaluated. The optimization of these parameters was carried out by a complete 23 factorial design (consisting of two levels and three factors), using the intensity of energy dispersive X-ray fluorescence (EDXRF) as response factor. SiZrP adsorbed the three metallic species, while SiIm adsorbed mercury selectively. This difference was assigned to the particular adsorption process involved in each instance. The interaction factor between pH and silica type was significant, suggesting that an unidimensional study could not have optimized the system. Using small amounts of the adsorbent matrices (0.2 g) resulted in better sensitivity, as well as an important saving of chemicals.
Two kinds of zirconia-containing mixed oxide gels (zirconia-silica and zirconia-magnesia) were synthesized as rigid microparticulates by means of the sol-gel process. The physical and chemical characteristics, such as the particle-size distribution, the specific surface area, the crystal structures and the acid-base properties of the oxides, were examined. The molar ratio of Si/Zr and Mg/Zr on the surface of the two mixed oxides was estimated, respectively, by means of electron spectroscopy. The chromatographic performance of zirconia-silica and zirconia-magnesia was compared to that of silica and zirconia with pyridine and phenol as solutes. The separations of nitroanilines and toluidines were achieved on the two mixed oxides under normal-phase liquid chromatographic conditions, respectively.
The solvent extraction of copper(II) with 3-phenylpropanoic, 4-phenylbutanoic, and 2-phenylbutanoic acids was carried out using 1-octanol and benzene as solvents at 25°C and at an aqueous ionic strength of 0.1 mol dm-3 (NaClO4). Each extraction equilibrium for these systems was determined in detail by a slope analysis and curve-fitting method. In the aqueous solution, the formation constants of copper(II) with these phenylcarboxylate anions were potentiometrically determined. The present results have been compared with the previous results for the extraction of copper(II) with phenyl-acetic acid using 1-octanol and benzene as solvents. Between the partition constants of CuA2 and HA (HA: phenylcar-boxylic acid), the following relationship was set up: log KD,CuA2=1.8log KD,HA-1.5 for four kinds of phenylcarboxylic acids in the 1-octanol systems. Although a remarkable difference in the extracted species between the benzene and 1-octanol systems was observed, the extraction constants of dimeric copper(II) species and dimerization constants in these extrac-tion equilibria were found to show a high correlation between the 1-octanol and benzene systems. The dimerization constants of copper(II) carboxylates in the 1-octanol systems increased with the number of carbon atoms in the acids: phenyl-acetic<3-phenylpropanoic<4-phenylbutanoic=2-phenylbutanoic acids, and the extraction constants of the dimeric species, Cu2A4(HA)2 in the benzene systems decreased in the order: 2-phenylbutanoic>phenylacetic>3-phenyl-propanoic>4-phenylbutanoic acids. In the systems using 1-octanol and benzene, 2-phenylbutanoic acid was superior to the other phenylcarboxylic acids as an extractant for copper(II).
A trace level concentration of Mn(II) was quantitatively extracted at pH 6.0 with 1×10-4 M of hexaacetatocalix(6)arene in hexane. Manganese(II) from the organic phase was stripped with 2 M sulfuric acid and determined as its iodo complex spectrophotometrically at 545 nm. The various parameters influencing extraction, such as pH, reagent concentration, nature of diluents, stripping agents, and effects of diverse ions, were studied to determine the optimum conditions for the separation of Mn(II). Manganese(II) was separated from Fe(III), Th(IV), Cr(III) as well as alkali and alkaline earth elements which are generally associated with it in a complex mixture. The method was extended for an analysis of Mn in real samples, such as minerals, alloys and pharmaceutical samples. The method is reproducible with a relative standard deviation of ±1.2%.
Two new stationary phases, cone bis(undecenyloxy)-p-t-butyl calixcrown-5 polysiloxanes (PSO-C-cc-5) and partial cone 5,11,17,23-t-butyl-25,27-diethoxy-26,28-diundecenyl calixarene polysiloxane (PSO-PC-cE), are synthesized and used as stationary phases in capillary column gas chromatography. Their chromatographic characteristics, such as column efficiency, capacity factor, average polarity, operation temperature range, and peak asymmetry were measured. Their column efficiency is over 3000 plates m-1, and their average polarities are between that of OV-1701 and SE-54. Their maximum allowable operating temperature is up to 310°C. Then, 33 aromatic compounds and positional isomers were used to test the separation abilities of the two stationary phases. The results indicate that the synthetic calixarene stationary possess good separation ability for aromatic compounds and positional isomers. It is noticeable that the retention behavior of several positional isomers on the PSO-C-cc-5 column are different from that on PSO-PC-cE col-umn. The separation mechanism is also discussed.