Discussion A researcher was counting 1 mL fractions and wished to add a maximum of 2 mL of a “safer” cocktail to help comply with local regulations. The sample is a gradient run from 100% to 45% of solution A, the remainder is solution B. We evaluated several safer cocktails, namely ULTIMA Gold™ XR (part number 6013119), ULTIMA Gold AB (part number 6013309) and ULTIMA-Flo™ AP (part number 6013599) using this gradient system and tabulated the results below. The gradient was evaluated by preparing the mixtures indicated in the table and for each mixture, 1 mL was added to 2 mL of cocktail. Since no operating temperature was specified, we checked the stability at 18 °C and 20 °C only. Solution A = 3.5 mM tetrabutylammonium hydrogen sulfate, 35 mM KH2PO4, 0.125 mM EDTA (adjusted to pH 6) Solution B = 50% of Solution A and 50% acetonitrile. Gradient Ratio A:B ULTIMA Gold XR at 20 °C ULTIMA Gold XR ULTIMA Gold AB ULTIMA Gold AB at 18 °C at 20 °C at 18 °C ULTIMA-Flo AP ULTIMA-Flo AP at 20 °C at 18 °C 100:00 Clear Clear Clear Clear Clear Clear 90:10 Clear Clear Clear Clear Clear Clear 80:20 Clear Clear Clear Clear Clear Clear 70:30 Clear Clear Clear Clear Clear Clear 60:40 Clear Clear Clear Clear Clear Clear 50:50 Clear Clear Clear Clear Hazy Clear 45:55 Clear Clear Clear Clear Hazy Clear Recommendation: From the table, it can be seen that both ULTIMA Gold XR and ULTIMA AB are suitable for this application if used between 18 °C and 20 °C. If tritium is the nuclide of interest, we recommend the use of ULTIMA Gold AB since it will give the highest counting efficiency in this system. PerkinElmer, Inc. 940 Winter Street Waltham, MA 02451 USA Phone: (800) 762-4000 or (+1) 203-925-4602 www.perkinelmer.com For a complete listing of our global offices, visit www.perkinelmer.com/lasoffices ©2007 PerkinElmer, Inc. All rights reserved. The PerkinElmer logo and design are registered trademarks of PerkinElmer, Inc. ULTIMA Gold and ULTIMA-Flo are trademarks of PerkinElmer, Inc. or its subsidiaries, in the United States and other countries. All other trademarks not owned by PerkinElmer, Inc. or its subsidiaries that are depicted herein are the property of their respective owners. PerkinElmer reserves the right to change this document at any time without notice and disclaims liability for editorial, pictorial or typographical errors. 007902_06 N O T E Problem A P P L I C A T I O N Cocktail Selection for Tetrabutylammonium Hydrogen Sulfate and Acetonitrile Gradients L S C C O C K TA I L S LSC in Practice