Determination of very-long-chain fatty acids in serum by gas chromatography-nitrogen-phosphorus detection following cyanomethylation

Derivatization in mass spectrometry-3. Alkylation (arylation)

The review is devoted to alkylation (arylation) as a widely employed derivatization procedure for the protection of OH (carboxylic acids, phosphoric acids, sulfonic acids, alcohols, polyols, phenols, enols), SH (thiols) and NH (amines, amides) groups in order to increase volatility, to improve the chromatographic properties and, if possible, mass spectral properties of derivatives. Chemical aspects of derivatization and various alkylation (arylation) reagents and reaction procedures are described. Specific mass spectral (electron ionization, chemical ionization) features of derivatives helpful in identification, structure elucidation, profiling and quantitative determination of the above-mentioned polar compounds by coupled gas chromatography or high-performance liquid chromatography are discussed. Some common analytical applications of the procedures in organic chemistry, clinical chemistry, environmental chemistry etc. are briefly summarized.

Diagnostic patterns of very-long-chain fatty acids in plasma of patients with X-linked adrenoleukodystrophy

Pattern recognition analysis on the levels of the very-long-chain fatty acids (VLCFAs) in plasma is described for the visual discrimination of X-linked adrenoleukodystrophy (X-ALD) patients from normal healthy group. Plasma VLCFA compositions of 58 normal subjects and 16 X-ALD patients were examined by gas chromatography as their methyl esters to determine the area percentages of behenic acid (C22:0), lignoceric acid (C24:0) and hexacosanoic acid (C26:0) in the total fatty acids, and the concentration (microg/ml) of C26:0. When star symbol plotting was applied to the VLCFA values of C22:0 (%), C24:0 (%), C26:0 (%), C24:0/C22:0, C26:0/C22:0 and C26:0 (microg/ml) after normalization to the corresponding median values in normal group, the resulting deformed hexagonal star pattern was characteristic of each patient. Therefore, simple visual comparison with the equilateral hexagon of normal group average as the control pattern enabled one readily to discriminate X-ALD patients from the normal group. Additionally, canonical discriminant analysis performed on the six unnormalized VLCFA values correctly classified 74 plasma specimens into two separate clusters according to normal subject or X-ALD patient in the canonical plot.

Sensitive determination of bisphenol A in environmental water by gas chromatography with nitrogen-phosphorus detection after cyanomethylation

A new technique is proposed for the determination of bisphenol A in environmental water. The sample preparation consists of a single-step extraction of bisphenol A from a water sample with methylene chloride and the cyanomethyl derivatization of bisphenol A. 2,2'-Biphenol is used as an internal standard. Bisphenol A and biphenol can be quantitatively converted to their corresponding cyanomethyl ethers, which are then measured by gas chromatography with nitrogen-phosphorus detection. Peak shape and quantification of bisphenol A are excellent, with linear calibration curves over a range of 0.1-100 ng/ml. The detection limit is 0.1 ng/ml in water samples. The average recovery and RSD at a concentration of 5 ng/ml are 89.3 and 4.5%, respectively. The procedure is applicable to the quantification of bisphenol A in tap water, raw water and stream water.

A rapid screening procedure for the diagnosis of peroxisomal disorders: quantification of very long-chain fatty acids, as dimethylaminoethyl esters, in plasma and blood spots, by electrospray tandem mass spectrometry

A rapid method with potential to screen for many of the peroxisomal disorders using 5 microl of plasma or a 3-mm blood spot (3.6 microl blood impregnated on filter paper) is described. Fatty acids are liberated from plasma or blood spots and converted to dimethylaminoethyl esters. Trideuterated fatty acids, added as internal standards, are used to quantify eicosanoic (C20:0), docosanoic (C22:0), tetracosanoic (C24:0) and hexacosanoic (C26:0) acids by electrospray tandem mass spectrometry. The C26:0/C22:0 and C24:0/C22:0 ratios are significantly greater in the plasma of patients with peroxisomal disorders compared to controls. The C20:0/C22:0 ratio is elevated in the plasma of peroxisomal patients who accumulate phytanic acid. Blood spots collected from four peroxisomal patients between 2 and 10 days after birth and stored for up to 17 years, were shown to give between 33% and 233% higher C26:0/C22:0 ratios compared to age-matched controls.

Gas chromatographic-mass spectrometric determination of plasma saturated fatty acids using pentafluorophenyldimethylsilyl derivatization

An improved method for the detection of 11 saturated fatty acids (SFAs) including C12:0-C26:0 (even numbers only), C17:0, C19:0 and C23:0 in human plasma by gas chromatography-mass spectrometry (GC-MS) with a stable isotope internal standard as d3-stearic acid is described. This procedure was based on acidic treatment, liquid-liquid extraction, and chemical derivatization prior to instrumental analysis. Eleven pentafluorophenyldimethylsilyl-SFA derivatives were well separated without any interfering peaks in plasma samples. The characteristic ions at M-15, constituting the base peaks in the electron impact mass spectra for 11 SFAs, permitted their sensitive detection by GC-MS in the selected ion monitoring (SIM) mode. The SIM responses were linear with correlation coefficients varying from 0.993 to 0.999 in the concentration range of 0.05 to approximately 50 microg/ml for the 11 SFAs. The detection limits for SIM of the SFAs varied in the range of 0.05 to approximately 10.0 pg. When applied to the plasma samples of normal subjects and patients with X-linked adenoleukodystrophy, which is one of the hereditary peroxisomal disorders, the present method enabled us to determine the SFAs with good sensitivity and good overall precision and accuracy within the concentration ranges of 0.14 to approximately 82.35 micromol/l.

Dimethylaminoethyl esters for trace, rapid analysis of fatty acids by electrospray tandem mass spectrometry

The development of a new derivative, the dimethylaminoethyl ester, for the analysis of fatty acids by electrospray tandem mass spectrometry is described. Qualitative and quantitative analyses of long to very long chain fatty acids in plasma, blood, urine and wax were performed. Branched chain, unsaturated, dicarboxylic, hydroxy, amino and keto acids were studied. The quantitative analysis method using the new derivative is simple, rapid and precise with small sample size. It has good potential as a screening method for biologically important fatty acids. Copyright 1999 John Wiley & Sons, Ltd.