Determination of Amino Acids in Tobacco Samples by Capillary Electrophoresis/Indirect Absorbance Detection with Isolation of the Electrolysis Compartment and p-Aminobenzoic Acid as a Background Electrolyte

Abstract

A fast, convenient and sensitive method of capillary zone electrophoresis (CZE) and indirect UV detection was proposed for the determination of 16 amino acids. p-Aminobenzoic acid (PAB) was selected as a background electrolyte (BGE). An isolated cell included a BGE buffer part and an electrode buffer one, which were jointed with a glass frit. The isolated cell can prevent PAB from the electrode reaction and improve the stability of the detection baseline. The separation conditions of amino acids were investigated, such as different BGEs, BGE concentration, buffer pH and electroosmotic flow (EOF) modifiers. Under the selected separation conditions, 14 amino acid peaks could be separated in 12 min. The detection limits of the amino acids were in the range of 1.7 -4.5 μmol/L. The isolated cell is suitable for reagents reacting on the electrodes in capillary electrophoresis. The proposed method has been successfully applied to the determination of the amino acids in tobacco samples.

Indirect electrochemiluminescence detection of lysine and histidine separated by capillary electrophoresis based on charge displacement

“…In addition, the detection limits (S/N = 3) were 0.3 μM and 1.0 μM, respectively. Compared with CE coupled with other indirect detection methods , the linear ranges were equivalent and detection limits were better in our study. The repeatability of the method was investigated by eight consecutive injections of 50 μM Lys and 50 μM His standard solutions, with obtained RSD values of the migration time and indirect ECL intensity < 2% and < 5%, respectively.…”

Determination of seven preservatives in cosmetic products by micellar electrokinetic chromatography

“…Because of these interactions, cationic surfactants form a double layer in which hydrophilic ammonium ions orient towards the bulk solution. According to literature results, a reverse EOF can be generated at CTAB concentrations above 5.0 μM, and the magnitude of the reverse EOF is enhanced by increasing the CTAB concentration . Under the same concentration, CTAB provides a strong reversed effect than dose trimethyl tetradecyl ammonium bromide because of its longer alkyl chain .…”

“…According to literature results, a reverse EOF can be generated at CTAB concentrations above 5.0 lM, and the magnitude of the reverse EOF is enhanced by increasing the CTAB concentration [36]. Under the same concentration, CTAB provides a strong reversed effect than dose trimethyl tetradecyl ammonium bromide because of its longer alkyl chain [36]. The addition of CTAB to background electrolyte also decreased the adsorption of proteins on the capillary wall and generated a high EOF [35].…”

Important electromigration effects of carbon dioxide in capillary electrophoresis at high pH

“…As these kinds of analytes are generally not detectable by direct UV‐absorption, other methods are used that allow their detection without derivatization, most commonly indirect UV‐absorption or conductivity. Indirect UV detection has been used in high‐pH CZE of small inorganic and organic anions 4–8, amino acids 4, 6, 9–14 and sugars 4, 15–22. For this purpose, there are a sufficient number of suitable absorbing probes with satisfactory values of extinction coefficients available.…”

“…For this purpose, there are a sufficient number of suitable absorbing probes with satisfactory values of extinction coefficients available. They are mostly organic aromatic acids as pyridine‐2,6‐dicarboxylic (PDC) 5–7, 10, 15–17, salicylic 11, 12, nicotinic 11, p ‐aminosalicylic (PAS) 11, benzoic 11, 12, p ‐aminobenzoic 11, 14, sorbic 11, 19, ( N , N ‐dimethyl)benzoic 11, phthalic 12 or 1‐naphtylacetic acid 18, or inorganic anions like chromate 8, 23. Conductivity detection in high‐pH BGEs has been used, e.g.…”