Alfian Noor

Cerenkov and liquid scintillation analysis of the triple label 86Rb35S33P

Abstract A method was developed for the analysis of 86Rb35S33P as a triple-label. The analysis of the total activity of composite mixtures of the three radionuclides was demonstrated to be quantitative by the liquid scintillation efficiency tracing technique with recoveries between 99.7–100.4%. The activity of 86Rb in the triple label was determined by Cerenkov counting in water with a 52% counting efficiency. The combined activities of 35 S + 33 P were determined by subtracting the activity of 86Rb from the total activity of the triple label. The separate activities of 35S and 33P are obtained by difference after a period of time sufficient for the decay of 33P to negligible levels leaving only residual 35S in the sample. The method described is useful for the analysis of 86Rb35S33P as a triple label for the elements KSP in studies of fertilize use efficiency.

Application of pulse height spectral analysis to double-label counting of 35S−32P

Abstract The characteristics of magnitude and shape of the liquid scintillation pulse height spectra of composite samples of 35 S + 32 P were studied as a function of their 32 P: 35 S activity ratios and fluor quenching properties. Pulse height spectra were characterized via the measurement of the spectral index of the samples (SIS). A linear relation exists between the value of the dual-label activity ratio plotted on a logarithmic scale against the SIS of the composite sample when the sample and fluor cocktail characteristics are maintained constant. This relationship was used to determine the activity ratios of composite radionuclide samples. The separate activities of 35SS and 32 P of composite samples were calculated from the activity ratio and total activity. The method was tested against different mixtures of 35 SS and 32 P in plant matter. The mean % recovery of the calculated activities for 14 measurements of 32 P and 32 SS was 99.2%. The methods described are useful particularly with liquid scintillation counters not equipped with an external standard radiation source.

Pulse height spectral analysis of 3H:14C ratios

Abstract Activity ratios of 3 H: 14 C of isotope-labeled substances are employed commonly in biochemical studies of reaction mechanisms and pathways. The liquid scintillation pulse height spectral index (SIS) of a composite sample of 3 H and 14 C was demonstrated to provide an index to the 3 H: 14 C activity ratio of the sample. Linear and logarithmic relations between the 3 H: 14 C activity ratio and SIS were defined for a given level of quench. When the level of quench is maintained constant, the SIS was demonstrated to be directly correlated to the 3 H: 14 C activity ratios of the sample. A mean recovery of 102.3% was obtained for calculated 3 H: 14 C activity ratios over the range of 0.097:1–9.698:1. The method described provides the 3 H: 14 C activity ratios of samples without the need for determining the separate activities of the individual radionuclides of the dual label.

Heavy metal concentrations in cocoa beans (Theobroma cacao L.) originating from East Luwu, South Sulawesi, Indonesia

Concentrations of some heavy metals (Pb, Cu, Cd, As and Hg) were assessed for cocoa beans (Theobroma cacao L) originating from East Luwu, South Sulawesi, Indonesia after five-day fermentation. Consisting of PB 123, BR 25, and MCC 02 cocoa clones, the spectrophotometric analysis showed that concentrations of Pb, Cd, As and Hg in the cocoa beans over the three clones was below the detection limits of 0.100; 0.050, 0.010 and 0.005 mg/kg. For Cu, they were 19.343; 10.391, and 18.594 mg/kg respectively, but still below the maximum critical levels, established by the European Food Safety Authority (EFSA). Concentrations of those five heavy metals in the bean shells were found to be parallel to those in the cocoa beans, except for Pb.