Comparison of Columns for the Analysis of Surfactants and...
Transcript of Comparison of Columns for the Analysis of Surfactants and...
Matthew T. Hall and John T. Roy, Ph.D.Impact Analytical - 1910 West St. Andrews Road, Midland, MI 48640-2696
INTRODUCTION• Many surfactants are polar molecules with poor retention by reversed-phase HPLC• Specialty columns are now available for the analysis of surfactants and polar compounds• The objective of this study was to find the best conditions for analyses of these compounds by LC-MS and by HPLC• A single chromatographic column for LC-MS/HPLC analyses will reduce the inventory of columns needed for the deformulation of cleaning products• The optimum chromatographic column will improve efficiency for the analysis of these products
Comparison of Columns for the Analysis ofSurfactants and Other Polar Compounds by HPLC and Liquid Chromatography-Mass Spectrometry
SPECIALTY COLUMN TESTING
COLUMNS &CONDITIONS
Compounds were not observed by UV at 210 nm when the Acclaim column was used
1) Benzenesulfonic acid2) Xylenesulfonic acid
UV missed citric acid, but citric acid is detected by mass spectrometry
Organic Acids by UV at 210 nmMass spectrometry isuseful for detecting compounds without a UV chromophore
1) Citric acid2) Benzenesulfonic acid3) Xylenesulfonic acid
These acids were not observed when using the Acclaim column
UV missed citric acid, but citric acid is detected by mass spectrometry
Organic Acids - Negative ESI-MSAlkyldimethylbenzylammonium Salts -
Postive ESI-MSTotal Ion Chromatogram Positive ESI Mode
Alkyldimethylbenzyl-ammonium salts:C12, C14, C16
All compounds are separated and detected on the three columns
Contains ethoxylatedalcohols, amine oxides, and ternary ammonium compounds
One amine oxide was not observed on the ODS-AQ column
Cleaner B - Positive ESI-MSODS-AQ retains EOalcohols well, yielding poor detection by MS
Cleaner D - Positive ESI-MS
HILIC TESTING
CONCLUSIONS:• Both columns retained some polar compounds well• The columns are complimentary to each other, because compounds poorly separated on one column appear well separated on the other• Additional experience is needed with the HILIC column• Initial separation attempts are favored on specialty columns (Unison CK-18 or ODS-AQ) instead of the HILIC column
• Testing was done on Atlantis Hydrophilic Interaction Chromatography (HILIC) and ODS-AQ columns to determine additional options for the analysis of polar compounds• HILIC has become a popular technique in recent years, and an evaluation was needed to determine the potential of the column for the analysis of polar compounds• Impact Analytical has had little success in the past with the HILIC column, and optimization of chromatographic conditions was desired
Comparison of Columns:HILIC vs. Specialty
Reversed-Phase Columns
• Atlantis HILIC 4.6 x 50 mm, 3µ (90:10 v:v) acetonitrile / 0.1 M ammonium formate, pH 3.0 Conditions recommended by manufacturer
• ODS-AQ 4.6 x 250 mm, 5µ Gradient with 0.1% formic acid in water / acetonitrile
EXPERIMENTAL• Surfactants, polar compounds, and cleaning products were analyzed on three columns that are targeted for these analyses• The Acclaim Surfactant, Unison UK-C18, and ODS-AQ columns were tested• Columns of different dimensions and particle sizes were evaluated in this study, which complicates comparison• Actual stationary phases are proprietary, which limits understanding of separation mechanisms
COLUMNS & CONDITIONSAcclaim Surfactant 4.6 x 150 mm, 5µ Unison UK-C18 4.6 x 150 mm, 3µODS-AQ 4.6 x 250 mm, 5µ
• Gradient with 0.1% formic acid in water/acetonitrile• Detection with UV at 210 nm and electrospray-mass spectrometry (ESI-MS) • Modified conditions previously reported for this evaluation: N.E. Skelly, J. Chromatogr. Sci. 41: 22-25 (2003).
Additional testing of columns for the analysis of cleaning products was initiated to improve the chromatographic separation on the Acclaim Surfactant column. This column was compared to the Unison UK-C18 column that was found to perform well.
Acclaim Surfactant 4.6 x 150 mm, 5µUnison UK-C18 4.6 x 150 mm, 3µ
Gradient with 0.1 M ammonium acetateat pH 5.4 and acetonitrile
Various Acids by Negative ESI-MS
1) Citric acid2) Benzene sulfonic acid3) Xylenesulfonic acid
Citric acid andsulfonic acids arewell separated onboth columns withammomium acetatein the eluent
Ethoxylated Alcohols - Positive ESI-MS
Backgroundinterferences are noted for theanalysis ofethoxylatednonylphenol on the Acclaimcolumn withammomiumacetate in theeluent
Alkyldimethylbenzylammonium Compounds by Positive ESI-MS
Alkyldimethylbenzyl-ammonium compounds are retained well with ammomium acetate in the eluent
Hexadecyldimethyl-ammonium chloride is retained well and is not observed on the Unison CK-18 column eluent
Only thymine and acenaphthene are separated well on this column
ODS-AQ at UV 254 nm
Atlantis at UV 254 nm
Only cytosine and adenine are separated well on this column
Atlantis compared to ODS-AQ forThymine and Acenapthene
Thymine and acenaphthene are separated well on the ODS-AQ column
Atlantis compared to ODS-AQ forCytosine and Adenine
Cytosine and adenine are well separated on the Atlantis HILIC column
ADDITIONAL TESTING:ACCLAIM COLUMN
• The chromatographic conditons employed are important for obtaining good data for polar molecules• The Unison UK-C18 column performed very well for surfactant analyses under the conditions that were evaluated; the ODS-AQ column also performed well• A shorter ODS-AQ is available but has not been evaluated• The ODS-AQ was the longest column tested; the column retains compounds well, which yields poor detection for ethoxylated alcohols• The Acclaim column shows ethoxylated alcohols well, but citric and many other acids may be missed using this column; additional optimization is still required for this column
CONCLUSIONS: SPECIALTYCOLUMN TESTING
THREE-COLUMNCOMPARISON
1) o-phthalic acid 2) isophthalic acid
These acids were not separated when using the Acclaim column
Phthalic Acids - Negative ESI-MS