Amino Acids

Polysorbates are a class of emulsifiers used in some pharmaceuticals and food preparation. They are often used in cosmetics to solubilize essential oils into water-based products. Polysorbates are oily liquids derived from PEG-ylated sorbitan (a derivative of sorbitol) esterified with fatty acids. Surfactants that are esters of plain (non-PEG-ylated) sorbitan with fatty acids are usually referred to by the name Span. It is often required to quantitate Polysorbate (Polysorbate/Tween 20, Polysorbate/Tween 40, Polysorbate 60/Tween 60 and Polysorbate 80) by HPLC in various formulations. Polysorbates exist in form of oligomers.

Amino acids are essential components of numerous formulation. Health supplements can contain various amino acids and vitamins and require quantitation of each ingredients. Amino acids are very polar compounds with limited or no retention in reversed-phase chromatography. The most common approaches are reversed-phase chromatography with ion-pairing reagent and hydrophilic interaction chromatography (HILIC). Underivatized amino acids can be retained by combination of reversed-phase and cation exchange mechanism on Primesep 100 mixed-mode. Retention time is controlled by amount of acetonitrile, buffer and buffer pH. Method does not require ion-pairing reagent. This method is for UV detection. LC/MS, ELSD or Corona CAD can be employed for analysis of amino acids with trifluoroacteic acid or ammonium formate in the mobile phase. This approach can be used for HPLC analysis of all underivatized amino acids.

Dimethyl sulfoxide is important polar aprotic solvent, which is frequently used in pharmaceutical drug manufacturing, desolution, etc. DMSO is used as one of the solvents on protein chemistry due to universal ability to dissolve small molecules like amino acids. Amino acids and DMSO are very polar and have no retention on reversed-phase columns. In this HPLC application DMSO and glycine are separated on Primesep 100 mixed-mode column. DMSO is retained by weak reversed-phase mechanism and very low organic concentration is required in order to achieve any retention. Glycine, like any other underivatized amino acid, is retained by weak reversed-phase and moderate cation-exchange mechanism. Method uses acetonitrile/water/TFA gradient and UV detection.

Primesep 100 separates a mixture of amino acids (tyrosine, phenylalanine), organic acids (benzoic acid, mandelic acid), amines (benzylamine, pyridine), and neutrals (benzonitrile, toluene) in one HPLC run by combining reversed-phase, cation-exchange, and polar interactions. The method is tunable and peak order can be changed significantly by adjusting acetonitrile and trifluoroacetic acid concentrations. The separation method uses a mobile phase mixture of water, acetonitrile (MeCN, ACN) and trifluoracetic acid (TFA) and compatible with UV, mass spec (LC/MS) and evaporative light scattering (ELSD) detection.

11 underivatized amino acids (aspartic acid, glutamic acid, alanine, valine, methionine, isoleucine, cysteine, phenylalanine, histidine, lysine, and arginine) are separated by a Primesep 100 HPLC column by reversed-phase and ion-exchange mechanisms with LC/MS compatible conditions without the use of ion-pair reagents. The HPLC separation uses a TFA (trifluoroacetic acid) gradient in a mobile phase of water acetonitrile (MeCN, ACN with evaporative light scattering detection (ELSD).

Adding on to the previous HPLC separation of amino acids using Bufferless Ion Separation (BLIS) Chromatography; here we have additional amino acids separated on Primesep 200 column using only water and acetonitrile (MeCN, ACN) in the mobile phase.  Primesep 200 is a reverse-phase (RP) column with weak acidic ion-pairing groups embedded. With no buffer present in the mobile phase, detection can be achieved with UV, mass spectrometry (MS), evaporative light scattering detection (ELSD).

Primesep 100 separates a mixture of polar and nonpolar compounds in one analytical run. The amino acid cysteine; amino acid derivatives L-cystine, 2,2-dimethylcystine, and 2-methylcysteine; the polar acid benzoic acid; and the nonpolar neutral toluene are separated by a gradient using a combination of polar and hydrophobic interactions. The separation method uses a mobile phase mixture of water, acetonitrile (MeCN, ACN) and sulfuric acid (H2SO4) with UV detection at 210 nm.