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Minimizing Carry-over for High Throughput Analysis
Poster Title: Minimizing Carry-over for High Throughput Analysis
Submitted on 28 Aug 2015
Author(s): Christian Berchtold1, Reto Bolliger2, Guenter Boehm2, Götz Schlotterbeck1
Affiliations: 1FHNW Fachhochschule Nordwestschweiz, Hochschule für Life Sciences Gründenstrasse 40 CH-4132 Muttenz; 2CTC Analytics AG Industriestrasse 20 CH-4222 Zwingen; Switzerland
This poster was presented at HPLC 2015
Poster Views: 2,195
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Poster Information
Abstract: Methods
A LC-MS system consisting of an Agilent 1260 Infinity HPLC and Agilent 6120 Quadrupol LC-MS equipped with a multimode ion source (set on ESI mode) was used. A PAL RTC sample preparation system with a LC/MS-Tool, high pressure injection valve (VICI C72VC-6676D-CTC) with a 2 µL loop was used. For separation a high throughput gradient HPLC method of 2 minutes cycle time was established using an Agilent Zorbax SB C18 Column (3 µm, 2.1x50mm) for chlorhexidine injections.

The PAL RTC offers five major wash tasks for carry-over minimization, such as post clean solvent 1 and 2, valve clean solvent 1 and 2, and stator wash. Solvent 2 is chosen according to analyte and matrix solvability, since it is used as the major wash step directly after each run. In contrast, solvent 1 is used to maintain reproducible conditions for subsequent analyses (therefore usually the eluent at starting conditions is used). The parameters of each wash step have been systematically screened using an on-column injection of chlorhexidine followed by fresh blanks. For chlorhexidine a mixture of water/methanol/acetonitrile/2-propanol containing 1% formic acid (for solvent 2) resulted in minimal carry-over.. A total of 5 strokes and 200 µL solvent 2 and two strokes and 90 µL solvent 1 for post clean and valve clean have been used respectively. Usinging this conditions a carryover of less than 20 ppm has been observed usuing wash cycles of less than 2 minutes for chlorhexidin. An optimized auto sampler wash protocol was developed and general guidelines for method development for HT LC-MS applications were established. The coloumn has been identified as the main source of carry-over.
Summary: Minimal carry-over is a prerequisite for high throughput analysis. However, minimized carry-over and cycle time are competing and a careful optimization is mandatory. In this study the influence of wash conditions on carry-over of various compounds was investigated. A strategy to minimize carry-over was developed. The influences of different wash tasks were investigated. Finally the contribution of different system components such as injector valve or column was studied.Report abuse »
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