Scintillation spectrometry

Scintillation detection has been used since the earliest days of radioactivity and is still today employed to measure the whole range of radioactive emissions — alpha-and beta-particles, gamma-rays, neutrons and the more exotic leptons and mesons. In this chapter, I will restrict myself exclusively to scintillation as apphed to gamma-ray measurements. 

In Chapter 3, I introduced the idea that primary electrons produced by gamma-ray interaction lose their 

If the electrons are allowed to de-excite by falling back to the valence band, they will emit electromagnetic radiation. If this radiation is in, or near, optical wavelengths, it can be detected by a photomultiplier or other hght-measuring device to provide the detector signal. This is the basis of the scintillation detector. 

If we are to construct a scintillation detector for gamma-ray detection and spectrometry, the scintillator material must have a number of particular properties  

Practical Gamma-ray Spectrometry — 2nd Edition Gordon R. Gilmore 2008 John Wiley Sons, Ltd. ISBN 978-0-470-86196-7 

Butyl-PBD [2-(4-t-butylphenyl)-5-(4-biphenylyl)-1,3,4-oxadiazole] BBOT [2,5-bis(5-r-butylbenzoxazol- 354 367 382  

The great sensitivity of a photomultiplier tube to light is obtained by 

Many new instruments are equipped with a modification of the stan- 

There is one set of adjustments that have thus far been neglected they are the gain controls. In simplest terms the gain is an amplifier circuit that magnifies the size of an incoming signal. For example, a signal may 

Fignre 3-11. /3 spectrum of H. The data for this figure were obtained as described in steps 3-13 to 3-19 of the experimental section. 

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These two methods produce different release profiles in vitro. Figure 5 demonstrates the release kinetics of BCNU from wafers loaded with 2.5% BCNU pressed from materials produced using these two methods. The wafers containing tritiated BCNU were placed into beakers containing 200-ml aliquots of 0.1 M phosphate buffer, pH 7.4, which were placed in a shaking water bath maintained at 37 C. The shaking rate was 20 cycles/min to avoid mechanical disruption of the wafers. The supernatant fluid was sampled periodically, and the BCNU released was determined by liquid scintillation spectrometry. The BCNU was completely released from the wafers prepared by the trituration method within the first 72 hr, whereas it took just about twice as long for the BCNU to be released from wafers... 

Biggin CD, Cook GT, MacKenzie AB, Pates JM (2002) Time-efficient method for the determination of Pb-210, Bi-210, and Po-210 activities in seawater using hquid scintillation spectrometry. Anal Chem 74 671-677... 

Nozaki Y, Zhang J, Takeda A (1997) °Pb and °Po in the equatorial Pacific and Bering Sea the effects of biological productivity and boundary scavenging. Deep-Sea Res II 44 2203-2220 Nozaki Y, Dobashi F, Kato Y, Yamamoto Y (1998) Distribution of Ra isotopes and the °Pb and °Po balance in surface waters of the mid Northern Hemisphere. Deep-Sea Res. 145 1263-1284 Pates JM, Cook GT, MacKenzie AB, Anderson R, Bury SJ (1996) Determination of Th-234 in marine samples by liquid scintillation spectrometry. Anal Chem 68 3783-3788... 

DOE. 1995b. Separation and analysis of actinides by extraction chromatography coupled with alpha liquid scintillation spectrometry. Washington, DC U.S. Department of Energy. NTIS/DE96060013. 

Biggin et al. [115] have described a time efficient method for the determination of 210lead, 210bismuth, and 210polonium activities in seawater using liquid scintillation spectrometry. 

Pates et al. [41] have described a liquid scintillation spectrometry method for the determination of 234thorium in seawater with 230thorium as the yield... 

Krosshaven et al. [64] used scintillation spectrometry employing germanium detectors to measure 137 caesium and strontium in coastal seawaters. 

Groundwater age at each NGMP site has been assessed using multiple tracers. Tritium was analyzed in a 1 L unfiltered unpreserved sample using 70-fold electrolytic enrichment prior to ultra-low level liquid scintillation spectrometry (Morgenstern Taylor 2005). Samples for analysis of CFCs and SF6 (125 ml and 1 L, respectively) were collected in strict... 

The apparent retinal influx clearance,. Kin,retina expressed as mL/(min g retina), of the test substrate labeled with either [3 H] or [14C] from the circulating blood to the retina is determined by integration plot analysis. In brief, rats are anesthetized, followed by injection of the test substrate (e.g., an [3H]-labeled compound, about 10 /u.Ci/head) into the femoral vein. After collection of plasma samples, rats are decapitated and the retinas removed. The retinas are dissolved in 2 N NaOH and subsequently neutralized with 2 N HC1. The radioactivity of retinal cell lysates is measured by liquid scintillation spectrometry. As an index of the retinal distribution characteristics of the radiolabeled test substrate, the apparent retina-to-plasma concentration ratio (Vd) as a function of time is used. This ratio [Vd(Q] (mL/g retina) is defined as the amount of [3H] per gram retina divided by that per milliliter plasma, calculated over the time-period of the experiment. The Kjn,retina can be described by the following relationship ... 

In brief, the rats are anesthetized, followed by an injection of 0.2 mL of the test solution into the common carotid artery. The injection solution consists of a HEPES buffered Ringer s solution (containing 141 mM NaCl, 4 mM KC1, 2.8 mM CaCl2, and 10 mM HEPES, pH 7.4) which contains both the test substrate (e.g., a [3H]-labeled compound, about 10 /xCi) and a reference compound, which is highly extracted by the tissue (e.g., 0.1 /xCi [14C]n-butanol) in the presence or absence of transport inhibitors. If a [14C]-labeled compound is used as a test substrate, [3H]H20 can be selected as a reference compound. Rats are decapitated at 15 s after injection and the retina is removed. The retina is dissolved in 2 N NaOH and subsequently neutralized with 2 N HC1. The radioactivity is measured by liquid scintillation spectrometry. The RUI value, an index of the retinal distribution characteristics of the [3H] test substrate, is estimated using the following relationship ... 

Breakthrough. Eluate radionuclidic purity is determined by Nal scintillation spectrometry on 50 ml of eluate. Samples must be held at least one hour before measurement to allow full decay of Rb-82. To improve sensitivity of measurement, the most prominent 511+514 keV peak is counted. Computations are based upon comparison with an aliquot of Sr-82+Sr-85 solution used to prepare the generator.. Data are expressed in units of yCi Sr-82/ml of eluate/ mCi Rb-82 at end of elution. 

The post-bombardment processing of the activated sample may follow either a nondestructive assay of the radioactivity in the sample (gamma-ray scintillation spectrometry is used most often for this) or a chemical processing of the sample prior to the radioactivity assay. Techniques involving either precipitation, electrodeposition. solvent extraction, and ion exchange or some combination of these form the basts of the radio-chemical separation techniques used in activation analysis. 

Figure 2. Hydrolysis of 14C-cellohexaose (G6) by BS and BI celluloses. The enzymes were purified to homogeneity (3) and incubated with pure uniformly-labeled cellohexaose as described in earlier tests with other celloaextrins (19). Reaction mixtures (0.3 mL) contained 1 mg substrate and cellulose (200 units) in 20mM sodium phosphate, pH 6.2, 0.03% sodium azide. They were incubated at 35°C and at intervals aliquots were removed and chromatographed. Cellodextrins with lower DP (Gt-G5) were located by radioautography and estimated by scintillation spectrometry (19).

Figure il. Photolabeling of human platelet membranes with NI in the presence or absence of 10 M imipramine. Proteins were separated by SDS-PAGE, slices were solubilized in NCS/toluene and counted by scintillation spectrometry. 

Salonen, L. 1993. Measurement of low levels of 222Rn in water with different commercial liquid scintillation counters and pulse shape analysis. In J.E. Noakes, F. Schoenhofer, and H. A. Polach (eds), Advances in Liquid Scintillation Spectrometry 1992, pp. 361-371.Tucson Radiocarbon Publishers, University of Arizona. 

It must also be acknowledged that some targets are not suitable for screens that employ purified proteins. The most convenient assay for PFK activity requires the presence of several additional enzymes that link to generate a product that can be quantified by spectrophotometry. ODC enzyme activity is most commonly measured by trapping [14C]C02 for quantification by scintillation spectrometry. Neither assay is well suited for current HTS formats. It would have been technically difficult to screen for inhibitors of either enzyme without the use of recombinant microorganisms. 

Sediment Slow microbial degradation due to tight bonding of adsorbed Diquat to the clay minerals on the sediment (shake flask-liquid scintillation spectrometry, Simsiman Chesters 1976) t,/2 > 158 d for 1.5 pg/mL of infested sediment-water microcosm to biodegrade (derived from results of Simsiman Chesters 1976 Muir 1991). 

Triton X-100 solution are added to culture dishes to lyse cells by shaking the dish on a shaker for 20 min at room temperature. An aliquot (1 ml) of lysate is analysed by liquid scintillation spectrometry. All values for taurocholate uptake into cell monolayers are corrected for non-specific binding to the collagen... 

The colour quenching effect of carotenoids in liquid scintillation spectrometry has been studied in detail. The most efficient quenchers were lycopene [i/>, -carotene (225)] and echinenone [j8,/3-caroten-4-one (226)]. Use of the external standards ratio method to correct for colour quenching in the radioassay of carotenoids is justified.84... 

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