Analysis of volatile bases by high performance liquid chromatography with aerosol-based detection.
The development and performance of two methods are described whereby low levels of volatile bases are quantified by HPLC using either a charged aerosol detector (CAD) or a nano-quantity analyte detector (NQAD). A test set of 12 volatile bases (ammonia, hydrazine, methylamine, ethylamine, diethylamine, triethylamine, isobutylamine, N,N-diisopropylethylamine, morpholine, piperazine, ethylenediamine, and 1,4-diazabicyclo[2.2.2]octane) were analyzed. The studied compounds all exhibit poor UV chromophores and are typically undetectable by aerosol-based detection when using conventional volatile mobile phases. The ability to detect these analytes by CAD or NQAD depended on their propensity towards formation of a low volatility salt between the target analyte and mobile phase modifier. Trifluoroacetic acid (TFA) was found to significantly improve detection of most volatile bases. A low concentration (0.2 mM) of hydrochloric acid was additionally needed to enable detection of ammonia. The compounds were separated under hydrophilic interaction liquid chromatography (HILIC) conditions on a zic-pHILIC column. For all analytes, limits of detection (LOD) were measured in the range of 1-27 ng on column, which is comparable to previously reported detection limits for non-volatile analytes.
Merck Research Laboratories, Merck & Co., Inc., Rahway, NJ 07065, USA. ryan.cohen@merck.com
Ryan D
RD
Cohen
Yong
Y
Liu
Xiaoyi
X
Gong
D000336:Aerosols / Q000737:chemistry*; D000588:Amines / Q000032:analysis; D000641:Ammonia / Q000032:analysis; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D006834:Hydrazines / Q000032:analysis; D006851:Hydrochloric Acid; D057927:Hydrophobic and Hydrophilic Interactions; D057230:Limit of Detection; D036103:Nanotechnology; D000077489:Piperazine; D010879:Piperazines / Q000032:analysis; D014269:Trifluoroacetic Acid; D055549:Volatile Organic Compounds / Q000032:analysis*
D000336:Aerosols; D000588:Amines; D006834:Hydrazines; D010879:Piperazines; D055549:Volatile Organic Compounds; D000077489:Piperazine; C029424:hydrazine; D000641:Ammonia; D014269:Trifluoroacetic Acid; D006851:Hydrochloric Acid