Fast cleanup method for the analysis of Sudan I-IV and para red in various foods and paprika color (oleoresin) by high-performance liquid chromatography/diode array detection: focus on removal of fat and oil as fatty acid methyl esters prepared by transesterification of acylglycerols

A fast and effective cleanup method was developed for the analysis of Sudan I, II, III, IV, and Para Red (Sudan dyes) in various foods and paprika color (oleoresin) by high-performance liquid chromatography (LC) with a diode array detector (DAD). Removal of fat or oil in fatty sample was a critical point for reducing the volume of the final sample solution in order to obtain a sufficient level of the analytes. Separation of fat or oil from the dyes with a silica gel solid-phase extraction (SPE) column seemed unfeasible, because elution profiles of oil, fat, and the dyes were similar. Finally, fat and oil were separated from the dyes by elution from the SPE column with n-hexane, not as intact compounds but as fatty acid methyl esters prepared by direct transesterification of acylglycerols in fat and oil, leaving the dyes on the column. The dyes were eluted with n-hexane-diethyl ether (9 + 1). Gradient elution with water and tetrahydrofuran was used for separation on a C18 column by LC. Measurement of spectral of 0.5 microg/g of Sudan dyes in foods and 1 microg/g in paprika color (oleoresin) with the DAD was achieved.     

Determination of magnesium stearate in capsule- or tablet-type supplements

A simple method for the determination of magnesium stearate in capsule- or tablet-type supplements was developed. Free stearic acid in the sample was removed by extraction with tetrahydrofuran. The remaining stearate was converted to stearic acid by reaction with a cation-exchange resin. The resulting stearic acid was determined by gas chromatography with a polar column. Esters of stearic acid were not converted to stearic acid and would not cause a positive error in the amount of stearate. The amount of magnesium stearate was calculated based on the stearic acid concentration thus obtained. Magnesium stearate levels in 5 out of 25 supplements exceeded 2500 microg/g, which indicated the possible admixture of magnesium stearate.     

Measurement of atomic capture probabilities of negative pions in metal hydrides

Atomic capture probabilities of negative pions in some metal hydrides were measured. The capture by a hydrogen atom was detected by means of a pair of the annihilation rays of ⁰ which had been produced by the charge-exchange reaction of ^– with the capturing hydrogen nucleus (proton). This method ensures a high sensitivity and reliability of the measurements. The probabilities obtained were in agreement with previous measurements except for palladium hydride, which showed a much smaller probability than that given in the literature. The atomic capture of ^– is well described in the framework of the large mesic molecular model, in which the proportionality constant reflects the chemical states of the capturing atoms and also the neighboring ones.     

Measurements of transfer process in pion capture by a series of alcohols

The transfer of negative pions captured by hydrogen to heavier atoms has been investigated in a series of alcohols by measuring both 2 rays from ⁰ decay and pionic X rays. Capture rates for the pionic hydrogen of different chemical states in the molecule were determined from a comparison between the data for the ordinary compound and the deuterated one. The external transfer in the condensed phase was revealed by the dependence of the capture rate of hydrogen on the number of carbon atoms in the alkyl group. The influence of the chemical structure on the transfer process is discussed with respect to the large difference between the relative transfer rates, _C=1.5±0.2 and _O = 4.5±0.4, corresponding to carbon and oxygen, respectively.