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At least 37 records · Page 2Linked to original sources
PubMed1977

Rapid spectrophotometric determination of ascorbic acid in citrus fruits.

A new spectrophotometric method has been developed for determining ascorbic acid in citrus fruits. The method is based on interaction between dimethoxydiquinone and ascorbic acid, followed by extraction with chloroform. The resulting chloroform solution gives a maximum absorption at 530 nm, a determination limit of 22.0 microng/ml, and a linear range from 22.0 to 97.5 microng/ml. The molar absorptivity of the chloroform solution was 1.62 x 10(3). The reaction was quantitative over the pH range from 3.0 to 7.0. Ascorbic acid in citrus fruits was successfully determined by this method. Comparison of results with those obtained by using the AOAC method showed excellent agreement; the average recovery for the analysis of orange, grapefruit, and lemon juices was 100 +/- 0.3%.

Ascorbic Acid↗
PubMed1976

[Analysis of thiabendazole in citrus fruits and bananas].

With regard to routine analyses in market control, the authors recommend two methods (according to the expected amounts of active principle) for the determination of thiabendazole residues on citrus fruits and bananas. The ultraviolet spectrophotometric method is preferable in determining thiabendazole contents of more than 1 p.p.m., if the cleaning operations described are respected. For the detection of thiabendazole and for the determination of amounts of less than 1 p.p.m. (the tolerance limit being 0.2 p.p.m. for pomes, berries, stone fruits, kernel fruits and also for potatoes) the thin-layer chromatographic method seems likewise to be suited (also in considering that it is semi-quantitative by nature); especially since the spectrophotometric method yields values by 0.2 p.p.m. too high (due to the measurement of residual absorption of vegetable constituents). The authors are of opinion that such an error must be considered to be too high for contents lower than 1 p.p.m.

Chromatography, Thin Layer↗
PubMed1976

Disappearance of dislodgable residues of five organophosphate pesticides on citrus leaves and fruit during dry and wet weather in Florida.

Citrus leaf discs and fruit taken from trees sprayed at recommended levels and twice recommended levels with ethion, parathion, azinphosmethyl, carbophenothion, and dioxathion were shaken with water and wetting agent for removal of dislodgable residues at 0, 1, 3, 5, 7, 14 and 21 days following treatment. The first portion of the field experiment was performed during a period of no rainfall (April) and the second when there was rainfall (July) in 1973. Four replicates of 50 leaf discs and 4 fruit, respectively, were averaged from each sampling to give data reported. A gas chromatograph equipped with a flame photometric detector was used for analysis. Dislodgable residues found decreased with increasing time following application and samples from the wet period were lower than those from the dry period. Moisture and temperature could account for the differences in the two sampling period.

Citrus↗
PubMed1976

Parathion persistence on South African citrus.

The fate of parathion applied to citrus was affected by rain, sun and wind, but not much by fruit variety, while the application method had an important effect. The formulation influenced the persistence of parathion on leaves and glass in the laboratory, but had no influence on the persistence on leaves or fruit in the field. The deposits of the emulsifiable concentrate and of the wettable powder and oil mixture were higher than that of the wettable powder alone, but since the rates of disappearance were the same, higher harvest-time parathion residues on and in the fruit resulted when the first two formulations were used. The time needed to reach a tolerance value increased for applications made later in the growing season.

Citrus↗
PubMed1979

Acephate and methamidophos residue behavior in Florida citrus, 1976.

The half-life of acephate and its hydrolysate, methamidophos, in the rind of Temple and Valencia oranges, and grapefruit, lemons, and tangerines was 10.3 days and 10.5 days, respectively. Half-lives of acephate and methamidophos in citrus pulp were 15.0 days and 6.1 days, respectively based on 7-, 14-, and 21-day data. Seven days after treatment, acephate and methamidophos reached maximum levels in rind and pulp. Acephate residue levels in rind were less than 3.0 ppm 14 days after treatment; acephate residues in pulp were less than 3.0 ppm throughout the experiment. Methamidophos residue levels averaged less than 0.25 ppm after 21 days.

Absorption↗
PubMed1979

Gas-liquid chromatographic determination of thiourea in citrus peels.

A gas-liquid chromatographic (GLC) method was developed for the detection and determination of thiourea in citrus peels. After the peel is extracted with ethyl ether, the ether extract is adsorbed on sodium sulfate together with water. Thiourea is recoverd from both the sodium sulfate and the peel residue with ethyl acetate-acetone(2+1). The extracted mixture is cleaned on an alumina column, the eluate is concentrated under vacuum, and thiourea is extracted from the concentrate with sodium carbonate solution. GLC was carried out on the prepared benzoyl derivative of thiourea. The average recoveries of thiourea from lemon peel were 85.3, 93.1, and 97.6% at the fortification levels of 1, 10, and 100 ppm, respectively. The detection limit was low as 0.08 ppm.

Chromatography, Gas↗
PubMed1978

Bromacil and diuron residue levels in Florida citrus soils.

The widespread use of herbicides in Florida citrus groves raises the possibility of residue accumulation following repeated applications. To determine residue levels of commonly used herbicides, soil samples were taken from large experimental plots in commercial groves in Polk and Hardee Counties. Bromacil and diuron had been applied in combination at both locations for 7-8 years. Analyses of samples showed low levels of both herbicides at various soil depths to 60 cm. Only a small amount of bromacil was detectable one year after applications, but diuron levels were higher. Continuous applications at recommended rates and frequencies have resulted in maximum bromacil and diuron levels of 3.9 percent and 13.1 percent, respectively, of their total application.

Bromouracil↗
PubMed1978

High pressure liquid chromatographic determination of imazalil residues in citrus fruit.

A high pressure reverse phase liquid chromatographic method is described for determining the fungicide imazalil (1-[2,4-dichlorophenyl)-2-(2-propenyloxy)ethyl]-1H-imidazole) residues in whole citrus fruit, peel, and pulp. Imazalil is extracted from the fruit with ethyl acetate, partitioned into acid and back into ethyl acetate for cleanup, and detected by ultraviolet absorbance at 202 nm. Recovery from whole ground fruit of known amounts of imazalil applied to the surface of intact fruit averaged 84% 24 hr after application and 80% after the fruit had been stored 4 weeks at 15 degrees C.

Chromatography, High Pressure Liquid↗
PubMed1977

Effect of citrus pectin on blood lipids and fecal steroid excretion in man.

Citrus pectin (15 g/day) was added for 3 weeks to metabolically controlled diets in nine subjects. Pectin was consumed with fruit and sugar as a gel in divided doses with meals. Plasma cholesterol concentrations were reduced by a mean of 13% (P less than 0.001). Fecal fat excretion increased by 44% (P less than 0.001); neutral steroids by 17% (P less than 0.001) and fecal bile acids by 33% (P less than 0.02). Plasma triglyceride levels did not change.

Adult↗
PubMed1977

Dislodgeable residues of ethion in Florida citrus and relationships to weather variables.

Five different treatments of ethion on Valencia orange trees were compared for decay rates and for ethion monoxon and ethion dioxon production under different environmental conditions. The oxon metabolite levels observed were low and always below the residue level of ethion itself. There were no significant differences in the decay rates of ethion between treatments. A model of ethion decay utilizing environmental variables as a time base is presented. This model explains 94% of the variation observed in ethion decay during very wet and very dry periods in Florida. The application of these results and general experimental approach to worker safety reentry standards is discussed.

Chromatography, Gas↗