scholarly journals Fluorescein thiocarbamyl amino acids as internal standards for migration time correction in capillary sieving electrophoresis

2009 ◽  
Vol 1216 (15) ◽  
pp. 3418-3420 ◽  
Author(s):  
Haley R. Pugsley ◽  
Kristian E. Swearingen ◽  
Norman J. Dovichi
Keyword(s):  
Amino Acids ◽  
Migration Time ◽  
Internal Standards ◽  
Time Correction

scholarly journals Towards adaptive method for peak migration time correction: discretization period in electropherograms

Chemija ◽  
2020 ◽  
Vol 31 (3) ◽  
Author(s):  
Tomas Drevinskas ◽  
Audrius Maruška ◽  
Gintarė Naujokaitytė ◽  
Laimutis Telksnys ◽  
Mihkel Kaljurand ◽  
...  
Keyword(s):  
Capillary Electrophoresis ◽  
Adaptive Method ◽  
Reference Points ◽  
Migration Time ◽  
Time Shift ◽  
Internal Standards ◽  
Relative Standard ◽  
Adaptive Peak ◽  
Time Correction ◽  
Computationally Intensive

Capillary electrophoresis often causes unrepeatable peak migration times in the electropherogram due to changes of electroosmosis, yet in some cases this separation technique does not have a replacement alternative. Some attempts to overcome this issue have been performed introducing internal standards into the sample and compensating peak shifting in time. However, existing vector calculation-based methods are computationally intensive for portable instrumentation and usually limited to post-processing applications with 1 or 2 markers. In this work, an original approach of compensating peak migration time shift via signal discretization period correction is proposed. Using the proposed method, the number of reference points or markers that are used for compensation is extended. This method is effective in compensating migration time of peaks in real samples, where high sample injection volumes are used. Using 4 reference peaks in compensation, the method was capable of reducing the relative standard deviation of migration time of the peaks in the electropherograms more than 15 times. Corrected signal discretization periods indicated very high correlations with recorded separation currents, what can be perspective developing an adaptive peak migration time compensation method in capillary electrophoresis.

Migration time correction for the analysis of derivatized amino acids and oligosaccharides by micellar capillary electrochromatography

2000 ◽  
Vol 869 (1-2) ◽  
pp. 375-384 ◽  
Author(s):  
Xing-Fang Li ◽  
Hongji Ren ◽  
Xiaochun Le ◽  
Ming Qi ◽  
Ian D. Ireland ◽  
...  
Keyword(s):  
Amino Acids ◽  
Capillary Electrochromatography ◽  
Migration Time ◽  
Time Correction

Capillary Gas Chromatographic Analysis of Amino Acids by Enantiomer Labeling

1987 ◽  
Vol 70 (2) ◽  
pp. 234-240
Author(s):  
Ernst Bayer ◽  
Hartmut Frank ◽  
Jürgen Gerhardt ◽  
Graeme Nicholson
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Sea Water ◽  
Biological Fluids ◽  
Chemical Properties ◽  
Internal Standard ◽  
Optical Isomers ◽  
Internal Standards ◽  
Sample Enrichment ◽  
Physical And Chemical

Abstract The optical isomers of amino acids can be easily separated by gas chromatography using capillary columns coated with the chiral polysiloxane peptide, Chirasil-Val. Quantitative trace amino acid analysis in complex mixtures such as biological fluids, sea water, or protein hydrolysates can be achieved by enantiomer labeling: The D-amino acid enantiomers, which do not occur naturally, are added to the sample prior to analysis as internal standards. Because the D-enantiomers show the same physical and chemical properties as the natural L-enantiomers, they are ideal standard references. In routine analysis, the derivatization is achieved with a new automated derivatization robot. The D-standard serves as overall internal standard for the whole analytical procedure from sample enrichment to derivatization, chromatography, and response of the detector.

scholarly journals Validation and Application of Biocrates AbsoluteIDQ® p180 Targeted Metabolomics Kit Using Human Milk

Nutrients ◽  
2019 ◽  
Vol 11 (8) ◽  
pp. 1733 ◽  
Author(s):  
Hampel ◽  
Shahab-Ferdows ◽  
Hossain ◽  
Islam ◽  
Ahmed ◽  
...  
Keyword(s):  
Amino Acids ◽  
Human Milk ◽  
Biogenic Amines ◽  
Milk Composition ◽  
Milk Analysis ◽  
Analysis Tool ◽  
Targeted Metabolomics ◽  
Internal Standards ◽  
Liquid Chromatography Tandem Mass ◽  
Height For Age

Human-milk-targeted metabolomics analysis offers novel insights into milk composition and relationships with maternal and infant phenotypes and nutritional status. The Biocrates AbsoluteIDQ® p180 kit, targeting 40 acylcarnitines, 42 amino acids/biogenic amines, 91 phospholipids, 15 sphingolipids, and sum of hexoses, was evaluated for human milk using the AB Sciex 5500 QTRAP mass-spectrometer in liquid chromatography-tandem mass-spectrometry (LC-MS/MS) and flow-injection analysis (FIA) mode. Milk (<6 months lactation) from (A) Bangladeshi apparently healthy mothers (body mass index (BMI) > 18.5; n = 12) and (B) Bangladeshi mothers of stunted infants (height-for-age Z (HAZ)-score <−2; n = 13) was analyzed. Overall, 123 of the possible 188 metabolites were detected in milk. New internal standards and adjusted calibrator levels were used for improved precision and concentration ranges for milk metabolites. Recoveries ranged between 43% and 120% (coefficient of variation (CV): 2.4%–24.1%, 6 replicates). Milk consumed by stunted infants vs. that from mothers with BMI > 18.5 was lower in 6 amino acids/biogenic amines but higher in isovalerylcarnitine, two phospholipids, and one sphingomyelin (p < 0.05 for all). Associations between milk metabolites differed between groups. The AbsoluteIDQ® p180 kit is a rapid analysis tool suitable for human milk analysis and reduces analytical bias by allowing the same technique for different specimens. More research is needed to examine milk metabolite relationships with maternal and infant phenotypes.

scholarly journals GC-MS Discrimination of Citrulline from Ornithine and Homocitrulline from Lysine by Chemical Derivatization: Evidence of Formation of N5-Carboxy-ornithine and N6-Carboxy-lysine

Molecules ◽  
2021 ◽  
Vol 26 (8) ◽  
pp. 2301
Author(s):  
Svetlana Baskal ◽  
Alexander Bollenbach ◽  
Dimitrios Tsikas
Keyword(s):  
Amino Acids ◽  
Biological Samples ◽  
Methyl Esters ◽  
Gas Chromatography Mass Spectrometry ◽  
Reaction Products ◽  
Internal Standards ◽  
In Situ Preparation ◽  
Synthetic Amino Acids ◽  
Carboxylic Groups

Derivatization of amino acids by 2 M HCl/CH3OH (60 min, 80 °C) followed by derivatization of the intermediate methyl esters with pentafluoropropionic anhydride (PFPA) in ethyl acetate (30 min, 65 °C) is a useful two-step derivatization procedure (procedure A) for their quantitative measurement in biological samples by gas chromatography-mass spectrometry (GC-MS) as methyl ester pentafluoropropionic (PFP) derivatives, (Me)m-(PFP)n. This procedure allows in situ preparation of trideutero-methyl esters PFP derivatives, (d3Me)m-(PFP)n, from synthetic amino acids and 2 M HCl/CD3OD for use as internal standards. However, procedure A converts citrulline (Cit) to ornithine (Orn) and homocitrulline (hCit) to lysine (Lys) due to the instability of their carbamide groups under the acidic conditions of the esterification step. In the present study, we investigated whether reversing the order of the two-step derivatization may allow discrimination and simultaneous analysis of these amino acids. Pentafluoropropionylation (30 min, 65 °C) and subsequent methyl esterification (30 min, 80 °C), i.e., procedure B, of Cit resulted in the formation of six open and cyclic reaction products. The most abundant product is likely to be N5-Carboxy-Orn. The second most abundant product was confirmed to be Orn. The most abundant reaction product of hCit was confirmed to be Lys, with the minor reaction product likely being N6-Carboxy-Lys. Mechanisms are proposed for the formation of the reaction products of Cit and hCit via procedure B. It is assumed that at the first derivatization step, amino acids form (N,O)-PFP derivatives including mixed anhydrides. At the second derivatization step, the Cit-(PFP)4 and hCit-(PFP)4 are esterified on their C1-Carboxylic groups and on their activated Nureido groups. Procedure B also allows in situ preparation of (d3Me)m-(PFP)n from synthetic amino acids for use as internal standards. It is demonstrated that the derivatization procedure B enables discrimination between Cit and Orn, and between hCit and Lys. The utility of procedure B to measure simultaneously these amino acids in biological samples such as plasma and urine remains to be demonstrated. Further work is required to optimize the derivatization conditions of procedure B for biological amino acids.

scholarly journals Two-Step Derivatization of Amino Acids for Stable-Isotope Dilution GC–MS Analysis: Long-Term Stability of Methyl Ester-Pentafluoropropionic Derivatives in Toluene Extracts

Molecules ◽  
2021 ◽  
Vol 26 (6) ◽  
pp. 1726 ◽  
Author(s):  
Svetlana Baskal ◽  
Alexander Bollenbach ◽  
Dimitrios Tsikas
Keyword(s):  
Amino Acids ◽  
Methyl Ester ◽  
Stable Isotope ◽  
Internal Standards ◽  
Term Stability ◽  
Long Term Stability ◽  
Endogenous Amino Acids ◽  
Derivatives Of

Analysis of amino acids by gas chromatography-mass spectrometry (GC–MS) requires at least one derivatization step to enable solubility in GC–MS-compatible water-immiscible organic solvents such as toluene, to make them volatile to introduce into the gas chromatograph and thermally stable enough for separation in the GC column and introduction into the ion-source, and finally to increase their ionization by increasing their electronegativity using F-rich reagents. In this work we investigated the long-term stability of the methyl esters pentafluoropropionic (Me-PFP) derivatives of 21 urinary amino acids prepared by a two-step derivatization procedure and extraction by toluene. In situ prepared trideuteromethyl ester pentafluoropropionic derivatives were used as internal standards. GC–MS analysis (injection of 1 µL aliquots and quantification by selected-ion monitoring of specific mass fragments) was performed on days 1, 2, 8, and 15. Measured peak areas and calculated peak area ratios were used to evaluate the stability of the derivatives of endogenous amino acids and their internal standards, as well as the precision and the accuracy of the method. All analyses were performed under routine conditions. Me-PFP derivatives of endogenous amino acids and their stable-isotope labelled analogs were stable in toluene for 14 days. The peak area values of the derivatives of most amino acids and their internal standards were slightly higher on days 8 and 15 compared to days 1 and 2, yet the peak area ratio values of endogenous amino acids to their internal standards did not change. Our study indicates that Me-PFP derivatives of amino acids from human urine samples can easily be prepared, are stable at least for 14 days in the extraction solvent toluene, and allow for precise and accurate quantitative measurements by GC–MS using in situ prepared deuterium-labelled methyl ester as internal standard.

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