The soluble components transferect from urea resin tablewares used for long period, were discussed in the previous paper. In this paper, the methods of separation and determination of free formaldehyde were studied by liquid chromatography with thermal detector, for a basic study on the toxicity of formaldehyde. The thermal detector was unsatisfactory for determination of formaldehyde in low concentration, because of poor sensitivity. Therefore, the determination were made on the combined use to liquid chromatography and colorimetry with acetylacetone. The chromatographic conditions used were as follows: Apparatus JLC A Type (Nihon Denshi) Fixed phase Dowex 50W-X8 Eluent 0.1N HCl Flow rate of eluent 0.6ml/min Column: for separation 0.8×50cm (room temp.) for detection 0.8×8cm (35°C) Sensitivity ±1/100°C or 3/1000°C cfs Chart speed 60mm/hr Main results of experiments are summarized as follows: (1) The recovery of free formaldehyde (Cf) was 90-100% in the case of addition of formaldehyde. (2) Total formaldehyde (Ct) was determined after steam distillation and combined form formaldehyde (Cc) was calculated from the following formula. Combined HCHO(Cc)ppm=Total HCHO(Ct)-Free HCHO(Cf) (3) Free formaldehyde was determined about 1-87ppm on 12 samples of urea and melamine resin tablewares, and combined formaldehyde was about 0-31ppm.
Effects of urea, monomethylolurea (MMU) and dimethylolurea (DMU) on the toxicity of formaldehyde (HCHO) were investigated. The LD50 values of HCHO varied when mice were pretreated with urea, MMU or DMU. Mice pretreated with these chemicals were more susceptible to the toxic effect of HCHO than the control. Blood uric acid level was significantly increased by subcutaneous injection of HCHO in dogs pretreated with urea, though no significant change was observed in the control. Furthermore, increases of blood urea-nitrogen and creatinine levels in blood and of LDH activity were caused by HCHO in dogs, and these changes were significant after pretreatment with urea.
14C-β-BHC and PCB were administered orally to mice before and after parturition. The radioactivity, accumulated in mothers and its transfer to fetuses or suckling mice, was measured at weekly intervals. The effect of simultaneous dosing of PCB and β-BHC on the transfer of β-BHC was also investigated. The followings were confirmed: (1) 33.2-53.7% of β-BHC dosed to dams from 10 days of pregnancy to parturition were accumulated in mother mice and 1.6-2.2% in fetuses, respectively. (2) More than 90% of the accumulated β-BHC in mother mice was transferred to suckling mice through milk after parturition within one week. (3) 60.0-63.8% of β-BHC dosed during one week after parturition were transferred to suckling mice. (4) No significant effect was observed on the transfer of β-BHC to fetuses or suckling mice by simultaneous dosing of PCB and β-BHC.
We applied a mammalian cell culture method for the screening tests for toxicity. In this paper, toxicity of substances eluted from plastic, especially phthalic acid esters, was tested using colony formation of KB cell. The substances eluted from polystyrene, polyethylene, polypropylene, polyacrylic derivatives, polycarbonates and phenol-formaldehyde resins did not influence on plating efficiency of colony of KB cell. On the other hand, soft type polyvinyl chloride, urea-formaldehyde resin and melamine resin showed remarkable inhibitory effects on the plating efficiency of colony. Toxicity of urea-formaldehyde resin and melamine resin may be attributed to formaldehyde and that of soft type polyvinyl chloride to phthalic acid esters. The toxicity of phthalic acid esters decreased in the order of DOP>DEP>DMP.
It is well known that a growth rate of microorganisms or an yield of microbial metabolites are influenced by types or lots of the products of yeast extract used in culture medium for food hygienic examination. As one of the suspicious principles of these inhibitory effects, succinic acid was isolated from yeast extract tested and its properties were physico-chemically confirmed. Antibiotic activity of the substance against seven representative bacteria was determined. E. coli, B. calidolactis, and S. lutea tested, indicated higher sensitivity to this principle. The activity was almost the same level as that of food preservatives. It is necessary to control the fermentation condition carefully, in the production process of yeast extract for microbiological tests.
The rate of N-nitrososarcosine formation from creatine and sodium nitrite was studied under the condition of pH 3.0 and 37°C, similar to that in the human stomach after ingestion of foods. The initial rate of N-nitrososarcosine formation from creatine and sodium nitrite was calculatedd from the absorbance at 260nm after removing the interfering materials by extraction and thin-layer chromatography. It was proportional to the creatine and nitrite concentration, not to the square of the nitrite concentration under the experimental conditions; rate=k×[creatine]×[NaNO2]. The k value of the reaction from the equation was 0.66×10-3 (mol-1·l·min-1). When [amine] was 20mM and [NaNO2] was 300mM, the amount of N-nitrososarcosine formed from creatine and sodium nitrite was 4% of that of nitrosopiperidine and 0.008% of that of nitrosomorpholine.
Analytical optimum condition for the determination of arsenic by introducing arsine into an atomic absorption spectrophotometer system equipped with an argon-hydrogen flame was examined. The optimum concentrations of reagents in the prepared solution were 3-5N hydrochloric acid, 0.5-2.0% potassium iodide and 0.1-1.0% stannous chloride. The addition of 0.8-2.0g of zinc powder to 20ml of prepared solution was enough to obtain the highest absorbance of arsenic under 0.5kg/cm2 of arsine gas pressure. The absorbance of arsenic was decreased according to the acidity raised by sulfuric acid residue in prepared solution, but recovered by neutralization with ammonia water. The absorbance was interfered with over 5μg of Se4+ and over 500μg of Sb3+ added to the 20ml of prepared solution containing 1μg of arsenic.
The change of the tableware made of synthetic resin by using of electric range cooking was studied. In this paper, the increase of formaldehyde exudation from tablewares was primarily investigate. Furthermore the surface appearance of tablewares were also observed with a reflecting microscope and a surface roughness meter. The following results were obtained: 1. The amount of exuded formaldehyde from tablewares was higher when it was used in an electric range cooking for 2min, than when it was treated by the standard procedure of using water at 80°C or 4% acetic acid at 80°C. 2. In case of phenol resin, formaldehyde exudation did not increased, though the surface change was observed with naked eyes. 3. In case of melamine resin, the average amount of formaldehyde exudation increased to 2.1ppm from 1.3ppm. 4. In case of urea resin, the average amount of formaldehyde exudation increased to 7.1ppm from 2.5ppm. It was over 4ppm fixed as the acceptable level. 5. From old tablewares which were used at home for long period exuded more formaldehyde by electric range cooking. In one case, as high as 71ppm was detected. 6. Formaldehyde exudation was correlated with the surface roughness of tablewares.
Simultaneous determination of cadmium, lead, manganese, copper, and zinc in milk powder by atomic absorption spectrophotometry was investigated. The decomposition of milk powder was carried out with nitric, sulfuric and perchloric acid. By extracting the metals from the decomposed solution with sodium diethyldithiocarbamate-methyl isobuthyl ketone in pH 4 to 6, these metals were found to be determined with high accuracy, partly because the relation. between the concentration of metals in that solvent and the absorbance of spectrophotometry was admitted to be linear in wide range. The contents of these five metals in commercial milk powder were investigated by this method and following results were obtained; cadmium, 0-0.03ppm; lead, 0.1-0.5ppm; manganese, 0.1-0.4ppm; copper, 0.3-1.2ppm; and zinc, 6.3-12.4ppm.
A procedure was investigated for determining residual amounts of five carbamate insecticides, 3-methylphenyl N-methylcarbamate (MTMC), 2-chlorophenyl N-methylcarbamate (CPMC), 2-sec-buthylphenyl N-methylcarbamate (BPMC), 3, 4-dimethylphenyl N-methylcarbamate (MPMC) and 1-naphthyl N-methylcarbamate (NAC), in vegetables. It consisted of benzene extraction, clean up by flolisil and charcoal columns, and trifluoroacetylation. Trifluoroacetylated carbamates were measured by electron-capture-gaschromatography and could be separated from each other on a 5 feet glass column packed with Gaschrom Q coated with 3.5% OV-17. The method has been used for potato, orange, Chinese cabbage, burdock, loquat, melon cucumber and komatsuna. In vegetables and fruits, the limits of detection Were 0.01ppm for MTMC, CPMC and BPMC, and 0.03ppm for MPMC and NAC.
In vitro growth inhibitory effects of glycine and several sodium salts of organic acid were tested using 9 laboratory stock strains, which originally isolated from Vienna sawsages. Consequently, it was found that the presence of 2.0% of glycine and 2.0% of sodium citrate in the culture media considerably inhibited the growth of most of the organisms tested. Experimental Vienna sawsages, supplemented with about 1.0% of glycine and about 1.0% of sodium citrate, followed by their 10min immersion in the solution containing about 1.0% of glycine and about 1.0% of sodium citrate, successfully prolonged their preservation period by 6 days at 10°C storage, when compared with that of the non-treated specimens.