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LS 6000 Scintillation System User’s Manual

PN 247971-F

6-8

Isotope/DPM Libraries

Setting Up A Quench Curve

6.2 Setting Up A Quench Curve

The DPM Library

The DPM Library can store the quench curves for any isotope stored in the Isotope Library

under liquid scintillator. The stored quench curves are available for use by any User Program.

If Low Level is present on the instrument, a separate DPM Library is created for Low Level

Standards. Up to 30 sets of quench curves can be stored between these two libraries.

A single label quench curve for

H, a single label quench curve for

C, and a dual label

quench curve for

C are stored in the Standard DPM Library. These factory installed

quench curves give results accurate to ±5%. If more accurate results are required, then

additional quench curves

H and

C can be stored in the DPM Library under a different

name or the factory installed curves can be deleted.

A quench curve must be set up for each isotope for which dpm calculations are desired. If the

same isotopes are used in single, dual and triple label experiments, the quench curves can be

set up and stored at the same time. The standards for each isotope are counted only once and

quench curves for single, dual and triple label studies are stored. A background quench curve

may also be stored. This background quench curve is subtracted from the standard quench

curves set up at the time the back-ground curve is set up. A separate background quench

curve may be stored for each quench curve, provided the quench curves are set up at separate

times.

Color Quench Correction (if installed) is calibrated at the factory. This monitor is always on

and is applied to the single label quench curves for the 5 factored isotopes in the Isotope

Library:

S, and

125

I. It automatically corrects for any color quench in samples

of these isotopes.

Setting Up a New Quench Curve

Setting up a quench curve is done infrequently and care must be taken to ensure its accuracy.

Quench curves for up to ten isotopes can be set up and stored in the DPM Library at a single

session. Prepare standards for each isotope desired.

A brief review of the steps for storing a quench curve are:

1. Prepare a set of standards with a known amount of dpm.

2. Count the standards before addition of the quenching agent, using the preset counting

program in DPM Setup program in the instrument.

3. Remove any standards that are not within a statistically acceptable range.

4. Add quenching agent to each standard.

5. Set up the DPM program on the instrument and count the quenched standards using the

preset counting program.

6. Edit the resulting curve as necessary.

Preparing the Standards

Standard quench sets are available from Beckman Instruments, Inc. for

H and

C. Do not

use commercial quench sets to set up low level quench curves. If you are using a prepared

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