A simple and systematic procedure for determination of 1,2-dibromo-3-chloropropane (DBCP), 1,3-dichloropropene (DCP), chlorobutol (TCB) and seven related compounds in citrus fruits was established. Since these compounds have extremely high volatility, the distillation apparatus for volatile oil determination was used. These compounds were trapped into cyclohexane (more than 94.2–98.4% at spiking levels of 0.5–50 ppm) by this distillation. The distillate was purified by Florisil column chromatography. All compounds except TCB were eluted with n-hexane:ether(93:7) and TCB was eluted with ether. Each eluate was injected into an ECD-gas chromatograph directly for determination. Their recoveries from lemon, orange and grapefruit were within 91.5–98.6% at the spiking levels of 0.01–1 ppm.
The most important parameters necessary for the precise control of the separation of monoethanolamine, diethanolamine, and triethanolamine on column distillation apparatus are their initial concentrations in the mixtures fed to the columns. Currently, the use of a solid-state optical sensor, which makes it possible to determine the desired ratio in a mode close to the real-time regime. The technical parameters for the sensitivity and speed achieved by the sensor are determined in the determination of monoethanolamine, diethanolamine, and triethanolamine, as well as the sensor parameters and conditions of use, which enable the sensor to effectively solve the tasks. In particular, the concentration of the mixture of analytes in the sensor chamber is 500 mg / m3, the thickness of the sensitive coating is about 0.5 μm, the operating temperature is 45÷50 ° C, the time for one cycle of measuring the diethanolamine/triethanolamine ratio is 150 ÷ 180 seconds.
Abstract
A dichromate-spectrophotometric method for the determination of ethanol in wine was compared in a collaborative, matched pair study with the AOAC dichromate-titrimetric method, 11.008-11.011. Both methods require distillation of the sample into dichromate. The titrimetric method measures ethanol by titrating the excess dichromate with ferrous ammonium sulfate after conversion of ethanol to acetic acid; the spectrophotometric method directly measures the reduced dichromate formed after oxidation. In addition to comparing the 2 methods, the collaborative study also compared the use of 2 types of assemblies for obtaining the ethanol distillate: the Scott-type, which is used in 11.008-11.011, and the electric Kirk-type. Results of the collaborative study indicated that the repeatability and reproducibility of the official titrimetric method were generally far superior to those of the spectrophotometric method; therefore, adoption of the spectrophotometric method is not recommended. Comparison of titrimetric method results obtained using the 2 types of stills indicated that repeatability and reproducibility were somewhat better when Scott apparatus was used, but measurements using Kirk-type compared well in the range of ethanol concentrations found in table and fortified wines. The Kirk-type distillation apparatus has been adopted official first action as an alternative to Scott apparatus in the dichromate oxidation method for ethanol in wine, 11.008-11.011.
It is now possible to determine proper motions of high-velocity objects in such a way as to obtain with some accuracy the velocity vector relevant to the Sun. If a potential field of the Galaxy is assumed, one can compute an actual orbit. A determination of the velocity of the globular clusterωCentauri has recently been completed at Greenwich, and it is found that the orbit is strongly retrograde in the Galaxy. Similar calculations may be made, though with less certainty, in the case of RR Lyrae variable stars.
Simple Determination of Minute Amounts of Chloride Ion in Plating Solutions Using a Simple Distillation Apparatus for Total-Cyanide Analysis