Rapid and sensitive determination of the conversion of UV-cured acrylic ester resins by pyrolysis-gas chromatography in the presence of an organic alkali.

The double-bond conversion of UV-cured resins prepared from pentaerythritol triacrylate (PETA) was determined by pyrolysis-gas chromatography in the presence of an organic alkali, tetramethylammonium hydroxide (TMAH). The pyrogram of the uncured prepolymer compound, consisting of PETA and a photoinitiator, 2,2-dimethoxy-2-phenylacetophenone, contained specific products reflecting the original acrylate structure, such as methyl acrylate (MA) and methyl ethers of pentaerithritol. Meanwhile, in pyrograms of the UV-cured PETA, the yields of MA considerably decreased. The double-bond conversions of the cured resins, irradiated with various UV dosages, were calculated based on the relative yields of MA among specific products in the pyrograms. The conversions determined by this approach were analyzed by comparing them with those estimated by Fourier-transform infrared spectroscopy.     

Simple and rapid determination of trace amounts of gold(III), palladium(II), and platinum(IV) in industrial waste solutions after recovery of noble metals by combined use of GFAAS and anion-exchange separation.

A simple and rapid method for the analysis of trace amounts of gold(III), palladium(II), and platinum(IV) by the combined use of graphite furnace atomic absorption spectrometry and anion-exchange separation was proposed, and successfully applied to the rapid determination of metals in industrial waste solutions obtained from the final process of noble-metal recovery factories, because noble metals can be selectively and quantitatively separated to a high degree by using a small column containing only a 0.7 g-portion of a common anion-exchange resin and a dilute thiourea solution.     

Microchannel-assisted thermal-lens spectrometry for microchip analysis

We present a new method for homocysteine quantitation in human plasma based on in-capillary reaction of homocysteine with 2,2′-dipyridyl disulfide. Homocysteine is in this so-called thiol-exchange reaction quantitatively transformed in mixed disulfide concomitantly with formation of an equimolar amount of 2-thiopyridone that is further separated by micellar electrokinetic chromatography and determined specifically at 343 nm. The concentration of homocysteine is thus estimated indirectly from the result of 2-thiopyridone determination. The linear detection range for concentration versus peak area for the assay was from 0.03–3 mM (correlation coefficient 0.994) with a detection limit of 6 μM and a limit of quantitation 20 μM. The inter-day reproducibility of the peak area and the migration time were 1.37% and 0.05%, respectively. The method is simple, relatively rapid and can be easily automated. Moreover the common capillary electrophoresis apparatus with a UV detector can be used to distinguish between normal and pathological hyperhomocysteinemia plasma samples.     

Simple and rapid spectrophotometric determination of iron after preconcentration as its 1,10-phenanthroline complex on the natural polymer "chitin"

Preconcentration by collection of metal complexes on chitin has been applied to the spectrophotometric determination of iron in water. The iron is collected as its 1,10-phenanthroline (phen) complex on a column of chitin in the presence of tetraphenylborate as counter-ion. The iron(II)-phen complex retained on the chitin is eluted with an acetone-1M acetic acid mixture (8:2 v/v), and the absorbance of the eluate is measured at 512 nm. Beer's law is obeyed over the concentration range 1.1-11.2 mug of iron in 10 ml of eluate. In the presence of EDTA as masking agent, Ca, Mg, Al, Mn, Zn, Cd and Pb do not interfere in concentrations up to 100 times that of iron(II) and Co, Ni and Cu do not interfere in concentrations up to 20 times that of iron(II). Common inorganic anions do not interfere in concentrations up to 10,000 times that of iron(II). The proposed method has been applied to determination of iron in tap water.     

Spectrophotometric determination of traces of hydrogen peroxide with the Ti(IV)-xylenol orange and the Ti(IV)-chromazurol S reagents

The formation of mixed ligand complexes in Ti(IV)-xylenol orange (XO)-H₂O₂ and Ti(IV)-chromazurol S (CAS)-H₂O₂ systems was studied by spectrophotometry. The former system gave constant absorbance (λ_max = 562 nm) under the condition of [XO]/[Ti(IV)] = 1 in the pH 2–4 region. In the latter system, a distinct maximum at 557 nm was observed when [CAS]/[Ti(IV)] = 4 in the pH range of 4.5–5.2. In both cases, the absorbance at λ_max was stable for a long time and proportional to the concentration of hydrogen peroxide. From those facts, the usefulness of the mixtures of Ti(IV)-XO and Ti(IV)-CAS as the colorimetric reagents for the determination of hydrogen peroxide can be expected. The conditions for the use of the Ti(IV)-XO and the Ti(IV)-CAS reagents were examined in detail, and both reagents were found to be available for trace analysis of hydrogen peroxide with high sensitivity.