Kunio Nakano

Evaluation and application of internal standardization in atomic absorption spectrometry with electrothermal atomization

Abstract A new dual-channel system developed for use in atomic absorption spectrometry is used to assess the internal standard technique for electrothermal atomization. Cobalt was found to be a suitable internal standard for iron determinations, and is used for determination of 7—330 ng Fe ml-1 in water samples. With use of the internal standard technique, fluctuations caused by atomizer variables are reduced and interferences from many cations are also decreased.

Internal standard method in flame atomic absorption spectrometry

Abstract Some selection criteria and experimental considerations for selecting an internal standard in flame atomic absorption spectrometry were studied. Rational criteria for the selection of internal standards include the atomization efficiencies of the elements. An experimental study of the variation of the atomization degree due to a temperature decrease can be made with the help of plots of absorbance against the rate at which the sample solution is introduced. The temperature decrease produced by increasing the rate at which water was introduced using a heated chamber without water-cooled condenser was estimated to vary from 2420 K to 2218 K with 1.0 ml water per minute. Curves for the alkali, alkaline earth, and several other metals were obtained in the air-acetylene flame. The shapes of the curves are critically dependent on the degree of atomization of the metal itself. Elements with curves that have similar slopes can be used as mutual internal standards. Some of the other factors which affect the atomization efficiencies—i.e. changes in fuel and air flow, and matrix composition—were also studied.

Kinetics and mechanism of acid hydrolysis of trichlorotrithioureachromium (III) complex and chloride anation of trans-dichlorotetraquochromium (III) complex ion☆

Abstract The kinetics of an acid hydrolysis (aquation) of the trichlorotrithioureachromium (III) complex and the chloride anation of trans -dichlorotetraquochromium (III) complex ion have been investigated in a strong acid medium. In 9·0 M hydrochloric or 9·0 M perchloric acid, the reaction proceeds in four steps, whereas in the case of 12·0 M hydrochloric acid it proceeds in three steps, where the final product of the reaction is found to be the trichlorotriaquochromium (III) complex. The results for the pseudo first-order rate constants for the equation in 12·0 M hydrochloric acid at 25°C were k 1 = (6·87 ± 0·89) · 10 −3 sec −1 , k 2 = (2·64 ± 0·21) · 10 −3 sec −1 , and k 3 = (2·43 ± 0·12) · 10 −4 sec −1 . For the chloride anation, 8·89 · 10 −4 (l/mole) 2 ·sec −1 was obtained. The results for the energies and entropies of activation for the aquation obtained in 12·0 M hydrochloric acid were 15·7 kcal/mole and −17·6 e.u. for the first step, 15·6 kcal/mole and −20·1 e.u. for the second step, and 15·1 kcal/mole and −26·4 e.u. for the third step, respectively.

Analysis and interpretation of the oxidation reaction of tris(2,2′-bipyridine)chromium(II) complex with hexaamminecobalt(III) ion[1]

Abstract Oxidation of [Cr(bpy)3]2+ with [Co(NH3)6]3+ in an acetic acid-sodium acetate buffer solution under different conditions in excess 2,2′-bipyridine was examined by means of a stopped-flow method. It was found that a simulation procedure with an analogue computer was effective for analyzing the reaction curves for this system. The rate equation for the reaction was found to be: d[Cr(bpy)3 2+ ] d t = k 1 [ Co(NH 3 ) 6 3+ +][Cr(bpy) 3 2+ ] + k 2 [Cr(bpy) 3 2+ ] where k1 is a second-order rate constant for the direct oxidation-reduction between these reactants, and k2 a first-order rate constant for the ligand dissociation of [Cr(bpy)3]2+. The reaction mechanism proposed was as follows: [ Cr(bpy) 3 ] 2+ + [ Co(NH 3 ) 6 ] 3+ → k 1 [ Cr(bpy) 3 ] 3+ + Co 2+ + 6NH 3 [ Cr(bpy) 3 ] 2+ + 2H 2 O → k 2 [ Cr(H 2 O) 2 (bpy) 2 ] 2+ + bpy [ Cr(H 2 O) 2 (bpy) 2 ] 2+ + [Co(NH 3 ) 6 ] 3+ → k 4 [Cr(H 2 O) 2 (bpy) 2 ] 3+ + Co 2+ + 6NH 3 The values of k1 and k2 were 187±4M−1 s−1 and 0.104±0.002 s−1(μ = 0.20, 25°C), respectively.