Water by liquid scintillation counting

Higuchi, H., M. Uesugi, K. Satoh, and N. Ohashi, 1984. Determination of radium in water by liquid scintillation counting after preconcentration with ion exchange resin. Anal. Chem. 56 761-763. 

To determine the concentration of tritium (3H) in water by liquid scintillation counting. 

A COMPARISON OF ANALYTICAL METHODS FOR SCREENING GROSS ALPHA AND BETA RADIOACTIVITY IN WATER BY LIQUID SCINTILLATION COUNTING AND GAS FLOW PROPORTIONAL COUNTING... 

In municipalities where the water supplies are from deep-bored wells, samples of household water were collected for Rn-222 analyses. The water samples were analysed by liquid scintillation counting. The method for sampling and sample preparation were adopted from Partridge et al (1979). 

For the quantitation of in vivo absorption of 5Ca2+, 200 jd 1 of radioactive solutions were administered by gastric gavage to male mice kept on a deionized water diet during the previous 18 hours. After 4 hours blood was obtained by axillary incision and Ca2+ was extracted with TCA and determined by liquid scintillation counting (26). 

The initial mixture and each time point are then assayed for doxorubicin and lipid. Lipid concentrations can be quantified by the phosphate assay (see above) or by liquid scintillation counting of an appropriate radiolabel. Doxorubicin is quantified by an absorbance assay (see below). The percent uptake at any time point (e.g., t = 30 minutes) is determined by %-uptake = [(D/L), =30minutes] x 100/[(D/L) inuiai]. Doxorubicin can be assayed by both a fluorescence assay and an absorbance assay, but we find the latter to be more accurate. The standard curve consists of four to five cuvettes containing 0 to 150 nmol doxorubicin in a volume of 0.1 mL samples to be assayed are of the same volume. To each tube is added 0.9 mL of 1% (v/v) Triton X-100 (in water) solution. For saturated lipid systems such as DSPC/Chol, the tubes should be heated in a boiling water bath for 10 to 15 seconds, until the detergent turns cloudy. Samples are allowed to cool, and absorbance is read at 480 nm on a UV/Visible spectrophotometer. 

Tritium is measured by liquid scintillation counting of a portion of a distilled sample. Several reagents (such as sodium sulphite and silver iodide) can be added in the distillation to prevent interference by radioiodine. The allowed concentration of tritium in water for human consumption is relatively high thus the method presented here is normally adequate for routine determinations. However, if required, lower concentrations of tritium in water can be determined by electrolytic enrichment. The principles of the tritium determination procedure are as follows. 

Measurement Techniques. Light isotopes Concentrations of were determined radiometrically after synthesis of propane (13) in a proportional counter after about twenty-fold electrolytical enrichment of (14), The C content of large samples (. 5 g C) were determined by liquid scintillation counting after synthesis of benzene (15) fi-om CO2 which was extracted fi-om the water sample after acidification. The C content of small samples (<0.5 g C) were measured by accelerator mass spectrometry (AMS) W the Isotrace Laboratory of the University of Toronto. The C, and isotopic... 

Assay Procedures. Tissues, feces, urine samples, and sample fractions were assayed for radioactivity (RA) by liquid scintillation counting essentially as described by Magnussen et al. (9). Tissues were assayed for parent tilmicosin by methanol extraction, purification by liquid-liquid partitioning, and measurement by high performance liquid chromatography (HPLC) on a reversed phase phenyl column with detection by UV absorption at 280 nm. Elution was with a nonlinear gradient of mobile phase consisting of water, acetonitrile, and dibutyl ammonium phosphate at pH 2.5. 

In brief, this involved spiking homogenized tissues with non-radiolabeled reference compounds, methanol extraction, hexane-water partitioning followed by reverse phase chromatography (XAD-2 and C-18 HPLC). The activity in each fraction was quantified by liquid scintillation counting. 

M phosphate buffer, pH 4.6, by sonication. Enzyme, activator sample, and distilled water are added to a final volume of 0.2 ml. After incubation at 37°C for 1 h, 1 ml of chloroform/methanol (2 1 by volume) is added, and the liberated [ HJgalactose, which partitions into the upper phase, is determined by liquid scintillation counting. 

Isotope studies were conducted to determine the biochemical pathway of enhanced diazinon metabolism observed in paddy water of treated fields. In these studies, diazinon labelled at 4-position on the pyrimidine ring was incubated with paddy water from diazinon-treated and untreated fields as described earlier (17). The enclosed C02-free system was utilized to measure the C02 production, and the radioactivity in the evolved C02 was assayed by liquid scintillation counting (17). Diazinon residues were analyzed by gas-liquid chromatography after extraction with hexane. The results are summarized in Figure 1. Water from treated rice fields was capable of metabolizing 4-carbon atom on the pyrimdine ring, releasing more than 66% of the added radioactivity as C02 within five days of incubation. Such rapid metabolism was not observed with water from untreated field. 

Amino acid derivatives are best extracted from silica gel layers with methanol or with a mixture of methanol/ 25% NH3 (95 5) (7,10,17] or chloroform/methanol/ acetic acid (7 2 2) [77]. Peptides are extractable with acetone/water (1 1) [78], and amine derivatives are extractable with less polar solvents, e.g. ethyl acetate, benzene/acetic acid (99 1), benzene/triethylamine (95 5) [10,17], or with dioxane if, as well as fluorescence, radioactivity is to be measured by liquid scintillation counting [80]. Chloroform is suitable for the extraction of Dns-amino adds from polyamide sheets [40]. Exdt-ation and emission wavelengths are, if possible, adjusted to those of the individual Dns-deiivatives however, for almost every compound, exdtation can generally be achieved using the 365 nm mercury line. 

Automatic sample preparation methods for the determination of oarbon-14 and/or tritium, and carbon-14 and/or sulfur-36 in dual labelled samples by liquid scintillation counting are presented. The sample is burnt in a stream of oxygen, and the combustion products carrying radioisotopes are subsequently separated and collected for radioactivity determination. Tritium is measured as water, carbon-14 as "carbamate" and sulfur-35 as sulfuric acid. The procedures run automatically, they are free of memory effect and cross contamination, and provide quantitative recovery. 

Surfactant retention (adsorption plus any other phenomena that might cause retention) was measured by injecting a surfactant solution containing radiolabeled sodium dihexyl sulfosuccinate into a column packed with contaminated Hill field soil. Tritiated water was used as a conservative tracer. Figure 13 shows the effluent concentration from the column for both these labeled molecules as measured by liquid scintillation counting. The almost identical breakthrough and elution of these molecules indicate very low adsorption of the surfactant on this soil. 

---