Trace metal enrichment by automated on-line column preconcentration for flow-injection atomic absorption spectrometry

An on-line column preconcentration technique for flow-injection atomic absorption spectrometry was developed. Diverse metal ions (Cd²⁺, Zn²⁺, Cu²⁺, Mn²⁺, Pb²⁺, Fe³⁺ and Cr³⁺) in solution were concentrated quantitatively by a microcolumn (7-mm × 4-mm i.d.) packed with Muromac A-1, which is an iminodiacetate chelate resin, in a flow-injection system. From the pH dependence of the uptake of the ions, all the divalent metals examined were recovered quantitatively in the pH range 3–5 and the trivalent metals were recovered at a maximum pH of 1. Enrichment factors using 20-ml samples were in the range 90–180-fold for the seven elements and the sampling rate was 13 h^?1. The 3σ detection limits were in the range 0.14–2.1 μg l^?1 and the relative standard deviations for replicate measurements (n=3–4) were in the range 0.7–1.7%. The method was compared with flame and graphite furnace atomic absorption spectrometry. Application to the determination of cadmium and copper in several standard reference materials is described.     

Diffusion controlled formation of husk-like microcapsules

 Solid microspheres consisting of thermal heterocomplex molecules made from heating a mixture of aspartic acid and proline were transformed into husk-like microcapsules in their aqueous suspensions when pH value increased. The thickness of the outer shell of the husk-like microcapsule decreased as pH increased. Formation of the husk-like microcapsules is discussed to be due to both diffusion of the constituent molecules from the inside of the microspheres and conformational changes of those molecules in the process. Received: 16 October 1996 Accepted: 16 January 1997     

Effects of low-LET radiations on CR-39 track detector

The effects of Co-60 gamma-rays and about 25-MeV pulsed electrons have been investigated on CR-39 plastic nuclear track detector. The bulk etch rate was measured as a function of the absorbed dose under three different irradiation conditions; gamma-ray exposure in air at the dose rate of 6 kGy/h, that in vacuum and electron shower in air at 126 kGy/h on average. It was found that the bulk etch rate (V) increased nearly exponentially with the dose (D); V=V₀exp(kD), and the characteristic parameter (k) was 35, 9 and 12 MGy⁻¹, respectively. It is considered that a lack of oxygen in damage formation processes could occur momentarily during a short electron pulse, just similarly to the vacuum effect of reduction in track etch rates in outgassed CR-39 plastic.     

Vibration measurement by vibrating-plate holograms

If a hologram of a vibrating object is recorded on a photographic plate which vibrates synchronously with the object, the reconstructed image produces equi-amplitude fringes of the object vibration, the amplitude of which is reduced by a constant determined from the amplitude of the plate vibration. This phenomenon can be used as a method to extend the measurable range of vibration amplitudes, and some experimental results are shown.     

X-ray photoelectron spectroscopic observation of nitrogen-containing gases adsorbed at high pressures on some transition metals

The chemisorbed species formed by reaction of nitrogen-containing gases (NO, N₂O, N₂ and dry air) on some transition metals (Ni, Cu, Ti, Co and Pd) at high pressures (1–200 torr) are examined by XPS. At least four adsorption species are observed on the surface at ambient temperature. They can be assigned to ?NO₃ (407.3 eV), ?NO₂ (404.5 eV), ?NO (400.0 eV) and the nitrogen bound directly to metal, which shows a characteristic energy value for each metal. This feature differs from the reported results of low pressure adsorption experiments. Relative abundances among the chemisorbed species vary with individual metals and gases.     

Thermal properties and solubility of poly-1,4,5,8-naphthalenetetracarboxydiimides containing 1,3,5-triazine rings

Aromatic polyimides were synthesized by polymerization of 1,4,5,8-naphthalenetetracarboxylic dianhydride and 2-dialkylamino-4,6-dihydrazino-1,3,5-triazines by a solution polymerization method followed by cyclodehydration. The polyimides had number-average molecular weights over 13,000–16,000 or viscosity values of 0.23–0.65 dl/g. The x-ray diffraction diagram of polyimide I showed a crystal pattern, but the pattern became less pronounced with increasing length of the polymer side chain, and thus polyimide V showed a typical amorphous pattern. Study of the thermal stability of the polyimides by thermogravimetric analysis showed that a steep weight loss occurred in the range 380–410°C. Among the polyimides, I had only poor solubility in organic solvent, while IV and V were soluble even in general organic solvents such as tetrahydrofuran and dioxane.     

Dynamic range of a thermoplastic photoconductor hologram

A thermoplastic photoconductor material is well-known as a hologram recording material. The dynamic ranges of a thermoplastic hologram are studied in two softening methods. One is the conventional heating method, and the other is the newly developed solvent vapor method. It is found that the solvent vapor method makes the dynamic range ten times as wide as the heating method, and in the solvent vapor method exposure time and charging voltage hardly affect the final diffraction efficiency.