Dear Gautham Sudhakar,

A recent study Trimethylsilyl Derivatization Gas Chromatography/Mass Spectrometry method was used to analyze amino acids in hair.

The study entitled "Quantitation of Amino Acids in Human Hair by Trimethylsilyl Derivatization Gas Chromatography/Mass Spectrometry" and published in Enliven Archive | www.enlivenarchive.org 1 2014 | Volume 1 | Issue 1

Abstract

The distribution of amino acids in hair can divulge information regarding the health (e.g., diabetes) and provide a means for detecting the history of the disease by segmentation of the hair as well as attributes of an individual (e.g., sex and age). Therefore, an nonenzymatic method of hair digestion and profiling is required. In addition to optimizing and validating a method for measuring the distribution of amino acids in human hair, a robust and comprehensive approach to objectively compare the most effective means of extracting and manipulating chromatographic data to obtain the best limits of detection, linearity, and sensitivity are provided.

Data comparisons were made by operating the mass spectrometer in a mode that rapidly switches between total ion current (TIC) and selected ion monitoring (SIM) modes during each sample injection. In this way, any external confounding factors were negated that may otherwise influence the comparison of the linearity and sensitivity between the two modes of operation. The use of SIM, peak areas, and an internal standard provided significantly better sensitivity and limits of detection than using peak heights, TICs, or no internal standard. The sample preparation steps included protein acid hydrolysis using hydrochloric acid and trimethylsilyl (TMS) derivatization using N,O-bis(trimethylsilyl) trifluoroacetamide (BSTFA). The optimal derivatization conditions were acetonitrile as reaction solvent, temperature of 100°C, and a reaction time of 30 min. The method was validated by measuring the amino acid content of myoglobin. This validation was accurate for nine of the fourteen amino acids found in myoglobin and gave detection limits in the range of 0.04–0.1 µmol/L, quantitation limits in the range of 0.1–0.5 µmol/L, recoveries between 80% and 110%, and linear models with coefficients of determination (R2

) greater than 0.99 in the tested range from 1 to 300 µmol/L. The remaining five amino acids of myoglobin were deleteriously affected by acid hydrolysis.

To view the full publication, please use the following link:

http://enlivenarchive.org/bioanalytical-002.pdf

Hoping this will be helpful,

Rafik

Thank you so much Rafik. 

The above mentioned paper by Rashaid et al. does not include the analysis of tryptophan in hair. The amino acid tryptophan is degraded during the common acid hydrolysis used for the isolation of amino acids from peptides or proteins before qualitative and quantitative determination. Usually this is done by hydrolysis in 6 M HCl at 110 °C for 24 h. Alternatives for the isolation of tryptophan from proteins are alkaline hydrolysis or enzymatic hydrolysis.

We use to determine the amino acid composition of human hairs by the classical method developed by Spackman, Stein and Moore (Analyt. Chem. 30, 1958, 1190 ff) after acid hydolysis as described above. The amino acid cystine (Cys) can be determined with this method, but not tryptophan. We determine tryptophan in human hair according to a colorimetric method using the p-dimethylaminobenzaldehyde reaction (K. Schaefer,  Determination of the amino acid tryptophan in protein fibres,  J. Soc. Dyers Col. 113 (10), (1997), 275-280).

Following the administrative order of the Europian Union concerning the determination of cystine you have first to oxidate this amino acid with performic acid-phenol-solution to cysteic acid before hydrolysis because it will be otherwise partial distroyed during hydrolysis with 6 M HCl at 110C.

For the determination of the cystine content of human hair, the acid hydrolysis in 6 M HCl (110 °C, 24 h) is performed in evacuated ampoules (in vacuum) to prevent oxidative degradation of cystine.