Measurement of the response-ratio of an ionization chamber filled with dry air to that filled with P-10 gas in the calibration of gas monitors.
We developed a new method to determine the response ratio of an ionization chamber (Ohkura ionization chamber: type I-4096 01/06) filled with dry air to that filled with P-10 gas. The response-ratio was obtained by comparing the output currents of the ionization chamber after introduction of radioactive gasses of identical activities contained in two small vessels. The obtained ratio was 0.690 ± 0.003, which agreed with the results obtained by other methods.
Activity measurement of 85Kr diluted by a large volume balloon technique.
The National Metrology Institute of Japan (NMIJ) participated in the CCRI(II) Key-comparison of (85)Kr activity measurement. The absolute internal gas-counting method was used, with a set of proportional counters of different length. The original (85)Kr gas was diluted by a factor of 2x10(5) in order to achieve the suitable activity concentration for the proportional counters. A new dilution method was introduced, based on a large-volume balloon and gravimetric determination of the dilution volume with small uncertainties.
Development of new analytical methods for the determination of caffeine content in aqueous solution of green coffee beans
BackgroundThis study was conducted to develop fast and cost effective methods for the determination of caffeine in green coffee beans. In the present work direct determination of caffeine in aqueous solution of green coffee bean was performed using FT-IR-ATR and fluorescence spectrophotometry. Caffeine was also directly determined in dimethylformamide solution using NIR spectroscopy with univariate calibration technique.ResultsThe percentage of caffeine for the same sample of green coffee beans was determined using the three newly developed methods. The caffeine content of the green coffee beans was found to be 1.52 ± 0.09 (% w/w) using FT-IR-ATR, 1.50 ± 0.14 (% w/w) using NIR and 1.50 ± 0.05 (% w/w) using fluorescence spectroscopy. The means of the three methods were compared by applying one way analysis of variance and at p = 0.05 significance level the means were not significantly different. The percentage of caffeine in the same sample of green coffee bean was also determined by using the literature reported UV/Vis spectrophotometric method for comparison and found to be 1.40 ± 0.02 (% w/w).ConclusionNew simple, rapid and inexpensive methods were developed for direct determination of caffeine content in aqueous solution of green coffee beans using FT-IR-ATR and fluorescence spectrophotometries. NIR spectrophotometry can also be used as alternative choice of caffeine determination using reduced amount of organic solvent (dimethylformamide) and univariate calibration technique. These analytical methods may therefore, be recommended for the rapid, simple, safe and cost effective determination of caffeine in green coffee beans.