[Trace Analysis of Lead in Copper Gluconate by Atomic Absorption Spectrometry after Separation by Co-Precipitation with Bismuth].

In order to determine trace amounts of lead in copper gluconate by atomic absorption spectrometry (AAS), the authors investigated a separation and pre-concentration procedure using a co-precipitation technique with bismuth. After ashing 2.0 g of the sample by means of a dry process, the ash was dissolved in (1→100) nitric acid and 75 µg of bismuth was added. Lead was co-precipitated by using an ammonium solution controlled to pH 9.5-10.5. The precipitate was left at room temperature for over 15 minutes to age, and then washed with a (3→100) ammonium solution three times. The precipitate was dissolved in (1→100) nitric acid and then analyzed by AAS. The quantification limit of this method was 0.5 mg/kg, and the trueness, repeatability and intermediate precision were 99.6%, 4.2% and 4.2% at the spiked concentration of 0.5 mg/kg, and 94.4%, 2.8% and 4.0% at the spiked concentration of 5.0 mg/kg, respectively. Thus, the present method for trace analysis of lead in copper gluconate was validated.

[Performance study of analytical method for ethoxyquin in fruit].

A performance study of an analytical method of ethoxyquin (ET) in apples and pears was conducted. In the proposed method, the sample was homogenized with thiourea and ET was extracted with acetone instead of hexane used in the official analytical method for ET, in order to improve the extraction efficiency. Furthermore, dibutyl hydroxytoluene was added in the test solution to prevent the decomposition of ET. For evaluation of the method. ET spiked into apples and pears at the level of 0.2 microgram/g was determined in replicate in six laboratories. Mean recoveries from apple, pear and Japanese pear were 85.3, 83.0 and 83.9%, respectively. Repeatability relative standard deviation values were 3.8-4.7% and reproducibility relative standard deviation values were 7.8-11.3%. The detection limits were 0.001-0.025 microgram/g in the six laboratories; this value may reflect instrument performance. ET spiked into apples and pears at the level of 0.2 microgram/g was detected by both LC/MS and GC/MS.

[Analytical method of volatile substances in styrene polymers by head-space gas chromatography using o-dichlorobenzene].

A quantitative analytical method for 8 volatile substances (such as styrene) in styrene polymers that are not soluble in tetrahydrofuran (THF) and dimethylformamide was developed. The sample was chopped finely and a 0.1 g portion was weighed in a head-space vial. To this was added 2 mL of o-dichlorobenzene (DCB) including 50 µg/mL of internal standard. The vial was sealed and heated at 140℃ for 1 hour and then 1 mL of the head-space gas was injected into a gas chromatograph using an automatic sampler. Samples of syndiotactic polystyrene, styrene block copolymer and modified polyphenylenether were dissolved or dispersed in DCB. Separation and accuracy of the method were satisfactory. Recoveries were 95-113% at the spiked concentration of 300 µg/g. The method was confirmed to be suitable for general styrene polymers that are soluble in THF. Equivalent results were obtained with this method and the method in "Specifications and Standards for Food, Food Additives, etc. " for general purpose polystyrene, high impact polystyrene, styrene/acrylonitrile resin and acrylonitrile/butadiene/styrene resin.