An economical system for liquid scintillation counting

Small glass shell vials (12 × 35 mm minivials), containing 2.0 ml of a dioxane-based scintillation solution plus a ¹⁴C-labeled sample, were placed in a conventional glass, 20-ml count vial and assayed in a scintillation spectrometer. Statistical comparison of counts recorded from ¹⁴C samples prepared both in the minivial system and conventional 20-ml count vials indicated that the two systems were equivalent with sample volumes of 10 and 100 μliters (1600-cpm solution) and 10 μliters (60-cpm solution). Conventional 20-ml glass or plastic count vials were both acceptable as containers for the minivials.There were no significant differences in the counts from samples in minivials placed on-center and off-center in the container vial. Cost per sample was reduced from 24.8 cents (conventional glass vials) to 4.7 cents (minivial system).     

Triple-label beta liquid scintillation counting.

The detection of radioactive compounds by liquid scintillation has revolutionized modern biology, yet few investigators make full use of the power of this technique. Even though multiple isotope counting is considerably more difficult than single isotope counting, many experimental designs would benefit from using more than one isotope. The development of accurate isotope counting techniques enabling the simultaneous use of three beta-emitting tracers has facilitated studies in our laboratory using the multiple tracer indicator dilution technique for assessing rates of transmembrane transport and cellular metabolism. The details of sample preparation, and of stabilizing the liquid scintillation spectra of the tracers, are critical to obtaining good accuracy. Reproducibility is enhanced by obtaining detailed efficiency/quench curves for each particular set of tracers and solvent media. The numerical methods for multiple-isotope quantitation depend on avoiding error propagation (inherent to successive subtraction techniques) by using matrix inversion. Experimental data obtained from triple-label beta counting illustrate reproducibility and good accuracy even when the relative amounts of different tracers in samples of protein/electrolyte solutions, plasma, and blood are changed.     

Anomalous liquid scintillation counting of chromium-51

Unusual behavior of chromium-51 in liquid scintillation cocktail is described. Rapidly declining count rate is attributed to first-order binding of chromate to glass vials.     

Preparation of 14C-labeled algal samples for liquid scintillation counting

Four commonly used techniques for preparation of ¹⁴C-labeled algal samples on membranes for liquid scintillation counting were compared and a simple technique for apparent net assimilation measurement from aqueous samples was introduced. All four techniques yielded similar radioactivities from the test cultures and are thus suitable for measurements of ¹⁴C algal samples. The possibly carcinogenic solvent dioxane was not necessary with PCS scintillation cocktail for dissolving radioactivity from algae on filters.     

A thermostable cocktail for the liquid scintillation counting of heterogeneous media

Considerable analytical errors arise in the liquid scintillation counting of heterogeneous media as a consequence of gel instability. With large sample numbers, a major causative factor of this instability is temperature changes during the counting period. An emulsifier-scintillation cocktail has been designed to provide stable counting conditions for heterogeneous media over a temperature range of 10–30°C, i.e., the wide range of temperature likely to be encountered in liquid scintillation counters lacking sample cooling facilities. A comparison was made with a conventional commercially available emulsifier-scintillator.     

Measurement of 131 I and 125 I by liquid scintillation counting

When aqueous samples are made miscible with a toluene scintillation solution by means of Bio-Solv BBS-3, high ¹²⁵I and ¹³¹I efficiencies can be achieved over a considerable range of “impurity” quenching, and adequate isotope separations can be achieved using liquid scintillation counters with “linear,” “pseudologarithmic,” or “logarithmic” amplification. Using an example of each sort of counter, we have graphically outlined the two somewhat different procedures for choosing the best instrument settings for single- and double-isotope counting. “Linear” instruments, despite a slightly more complex procedure for selection of settings, may offer the advantage, in double-isotope counting, of somewhat greater isotope separations because of the greater attenuation of photo-electron spectra.     

Low background scintillation counting

Counting radioactive samples with Beckman Instrument's Ready Caps, using a restricted energy window, LL-UL = 400-1000, resulted in machine backgrounds of under 2 cpm and efficiencies of counting relative to liquid scintillation cocktails (LSC) of 51%, 65%, 57%, 62%, and 1% for 32P, 125I, 14C, 35S and 3H, respectively. Signal-to-noise ratios from a quantitative molecular hybridization technique were increased 8-10 fold. There may be a general application for this product in experiments yielding low amounts of radioactivity in liquid samples.     

The surfactant Bio-Solv-BBS-3 as a scintillator in liquid scintillation counting

When the surfactant mixture Bio-Solv-BBS-3 is added to a scintillation solvent it acts as a primary scintillator in response to β emissions (and Compton electrons from γs). The fluorescence excitation threshold is higher and fluorescence yield is lower than those of the primary scintillators usually employed in scintillation counting. Presence of a surfactant in a sample containing ¹⁴C or more energetic βs will be counted at higher efficiency than would be indicated by a quench correction curve (efficiency vs sample channels ratios or external standard channels ratios) derived from standards not containing surfactant.     

A new combustion system for rapid preparation of biological samples for liquid scintillation counting.

A combustion tube equipped with two oxygen supply nozzles was developed for preparation of biological samples for liquid scintillation analysis. By using this new combustion system, relatively large quantities of biological tissues were easily burned within a few minutes and [¹⁴C]O₂ and/or [³H]₂O thus produced were promptly and quantitatively recovered. This system proved to have several advantageous characteristics, i.e., simple construction, easy and safe operation and no need of a catalyst such as cupric oxide for complete combustion.