scholarly journals Microfluidic ion stripper for removal of trifluoroacetic acid from mobile phases used in HILIC-MS of intact proteins

2021 ◽  
Author(s):  
Sam Wouters ◽  
Sebastiaan Eeltink ◽  
Rob Haselberg ◽  
Govert W. Somsen ◽  
Andrea F. G. Gargano
Keyword(s):  
Trifluoroacetic Acid ◽  
Adduct Formation ◽  
Ionization Mass ◽  
Intact Proteins ◽  
Mobile Phases ◽  
Column Removal ◽  
Ionization Suppression ◽  
Peak Areas ◽  
Shape Characteristics ◽  
Exchange Membrane

AbstractTrifluoroacetic acid (TFA) is commonly used as mobile phase additive to improve retention and peak shape characteristics in hydrophilic interaction liquid chromatography (HILIC) of intact proteins. However, when using electrospray ionization-mass spectrometry (ESI-MS) detection, TFA may cause ionization suppression and adduct formation, leading to reduced analyte sensitivity. To address this, we describe a membrane-based microfluidic chip with multiple parallel channels for the selective post-column removal of TFA anions from HILIC. An anion-exchange membrane was used to physically separate the column effluent from a stripper flow solution comprising acetonitrile, formic acid, and propionic acid. The exchange of ions allowed the post-column removal of TFA used during HILIC separation of model proteins. The multichannel design of the device allows the use of flow rates of 0.2 mL/min without the need for a flow splitter, using mobile phases containing 0.1% TFA (13 mM). Separation selectivity and efficiency were maintained (with minor band broadening effects) while increasing the signal intensity and peak areas by improving ionization and reducing TFA adduct formation. Graphical abstract

Determination of Nitroaromatic Photodecomposition Products of Tecnazene Using Liquid Chromatography with Amperometric Detection

2002 ◽  
Vol 67 (8) ◽  
pp. 1181-1192 ◽  
Author(s):  
Pavel Kubáň ◽  
Hugh Flowers
Keyword(s):  
Reference Electrode ◽  
Amperometric Detection ◽  
Nitroaromatic Compounds ◽  
Decomposition Products ◽  
Mobile Phases ◽  
Peak Areas ◽  
Standard Solution ◽  
High Concentrations ◽  
Liquid Chromatographic

Isocratic liquid chromatographic methods with mobile phases consisting of 20 mmol l-1 sulfuric acid and 60% acetonitrile (for 9 quickly eluted nitroaromatic compounds) or 75% acetonitrile (for 2 strongly retained nitrobenzenes) at a flow rate of 1.2 ml min-1 using a DC amperometric detection with a glassy carbon working electrode at -0.5 V vs Ag/AgCl reference electrode have been developed for the determination of 11 nitroaromatic compounds. The overall repeatability of the retention times was better than 0.5% and the repeatability of the peak areas ranged from 1.2 to 8.3% (n = 7) based on the manual injection of 300 μl of standard solution. Limits of detection (LODs for 3.S/N) of 25-250 nmol l-1 were obtained. The developed methods have been applied to the determination of nitroaromatic decomposition products in the UV-irradiated samples of a tecnazene (1,2,4,5-tetrachloro-3-nitrobenzene) solution. Due to the high selectivity of the DC amperometric detection in reductive mode, no interferences occurred in the analyses of UV-irradiated tecnazene solutions although high concentrations of other compounds (e.g., phenols, chlorophenols, inorganic anions, and carboxylic acids) were present.

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