Scintillators, liquid

From Packard Ultima Gold scintillation liquid. 

Gas ionization, solid scintillation, liquid scintillation and semiconductor detectors, autoradiography. Single and multichannel pulse height analysers. Coincidence and anticoincidence circuits. 

The radioactivity in each tube is quantified in a modified scintillation liquid counter. 

Elution with H20 five times 2 ml, collect in five counter tubes containing 15 ml scintillation liquid. 14C-galactose is eluted. 

Separation apply 100 pi from the assay and blank supernatants onto one column each. Wash the columns five times with 2 ml of H20 (discard the eluate, containing 14C-galactose). Elute 14C-galactose-l-phosphate with 2.5 ml of 100 mM HC1 into a counter vial containing 15 ml of scintillation liquid. Repeat the elution with... 

Test of the separation efficiency of the DEAE cellulose every new charge of DEAE cellulose (CL form) should be tested. Dry 10 pi each of 14C-galactose-1-phosphate and UDP-14C-galactose with nitrogen and dissolve in 300 pi H20, each. Put 100 pi of each in a counter vial containing 15 ml scintillation liquid (= 100%), 100 pi of each on columns with 1 ml DEAE cellulose, and 100 pi of both substances on a third column (mix). 

II. Purity test of 14C-galactose-l-phosphate dry 10 pi of 14C-galactose-l-phosphate with nitrogen, dissolve in 200 pi of H20. Put 100 pi in a counter vial with 15 ml scintillation liquid (= 100%) and apply 100 pi on a DEAE column. Elute stepwise as described in a) and b) above. Contamination, eluted with 100 mM HC1, should not exceed 0.1-0.2% of the total radioactivity eluted. 

Allow the samples and blanks to precipitate for about 15 min at room temperature and centrifuge for 5-10 min at 2000 xg. Decant the supernatant carefully and resuspend the pellet in 3 ml ethanol (66%), then centrifuge for 5-10 min at 2000 xg. Resuspend the pellet in 2.5 ml acetone then centrifuge for 10 min at 2000 xg. Decant the supernatant carefully and dry the pellet in a vacuum or under gaseous nitrogen. Dissolve the pellet in 0.5 ml H20 and add it to 10 ml scintillation liquid in counter vials. Rinse the centrifugation tube twice with 0.5 ml H20 each and add to the sample in the scintillation liquid. 

To extract the liberated fatty acids, 1.5 ml of 0.1 mM carbonate-bicarbonate buffer, pH 10.5 is added and the mixture is shaken for 10 s. Centrifugation for 45 min at 1500 xgin a swing-out rotor will separate the water from the lower organic phase. In a scintillation vial, 2 ml of the upper water phase are mixed with 50 pi of glacial acetic acid containing 500 pg ferric acid before the scintillation liquid is added (16 ml of Ecoscint toluene (7 1 volume). Liquid scintillation counting is done for 5 min and the LPL activity is calculated from the difference in counts between the blank and the sample vials [40]. 

Quantitation requires a phosphoimager which may not be readily available. Alternatively, the relevant regions of the silica gel may be scraped from the TLC into scintillation liquid followed by p-scintillation counting, but this is tedious and can lead to loss of material and is consequently inaccurate. 

For counting low-energy j3 radiation, the crystal is substituted by a scintillating liquid, and the sample is dissolved in the liquid (internal-source liquid scintillation counting). The method is also used to measure weak X-ray and y-ray emitters. Under these conditions, self-absorption of the radiation in the sample, absorption of the radiation in the air and the window of the detector, and backscattering of p particles are avoided. 

There are also liquid scintillation counters that use a scintillation liquid instead of a crystal. The sample to be counted is dissolved in the scintillating liquid. This method is suitable for a and P counting. 

In medical installations, the use of radioactive isotopes for diagnosis and therapy has significantly increased in the past years. Nonencapsulated radioactive elements are used for different purposes such as in diagnosis by tracers, treatment of thyroid or blood disorder, and in medical research. These activities produce some solid radioactive wastes like cotton, rubber gloves, syringes, etc., as well as liquid wastes, mainly scintillation liquids. Another type of waste is the encapsulated sources that are used for cancer treatment these elements must be changed when their activity decays below a certain level. 

After 60 min. of incubation at 25°C the reaction is terminated by filtration at Tomtec unifilter. The filters are washed twice with ice cold assay buffer. The filters are dried for 1.5 hours at 50°C, 35 pi scintillation liquid is added and bound radioactivity is counted in Wallac Tri-Lux scintillation counters. 

Attach the backing tape to the bottom of the dried plate and add 25 pL scintillation liquid buffer in all wells using a multichannel pipette. 

Liquid scintillation detectors operate on the principle of interaction of radiations with a special type of scintillating liquid that emits light upon interaction with radiation. The light is then processed in the same manner as in the case of a solid detector, as discussed below. 

Transfer 25 pi of each of the fractions to scintillation vials. Add 5 ml of scintillation liquid to the vial and count in a scintillation counter to determine the amount of labelled mRNA in each fraction. Plot the counts (see Fig. 5.4). 

Measure the activity of both the top and the bottom solutions by scintillation-counting techniques using a suitable scintillation liquid. Calculate the total activity of the HHO added to the top compartment initially by mass balance, taking into account the volume of the sinter, V. ... 

Many of the quenching problems discussed above can be lessened if an experiment is carefully planned. A wide variety of sample preparation methods and scintillation liquids are available for use. Some of the more common techniques are mentioned below. 

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