Mass spectrometry trimethylsilyl derivatives

Deliberate partial trimethylsilylation may be used as a means of distinguishing between various monosaccharides,199 and the nature of minor components formed on trimethylsilylation has been studied by mass spectrometry. Trimethylsilylation has been used in the separation of deuterated monosaccharides,200-203 and such deuterated trimethylsilyl derivatives as penta-0-(trimethyl-dliquid chromatography and mass spectrometry.143... 

Molecular ions were observed by gas chromatography-mass spectrometry (GC-MS) analysis for trifluoroacetyl 58 and trimethylsilyl 60 derivatives of mesocarb (sydnocarb) 59 (Section 5.03.12) <1999JMP1079>. Unlike the silyl derivative 60 and sydnones <1996CHEC-II(4)165>, no [M+—NO] ion was observed for trifluoroacetyl derivative 58. The characteristic ions PhCH2(Me)CH+ (m/z 119) and PhCH2+ (tn/z 91) were observed for both derivatives 58 and 60. 

The volatility of the trimethylsilyl derivatives of the aldonolactones and related carbohydrates has made these derivatives suitable for use in mass spectrometry.161,162 Petersson and coworkers161,162 reported the mass spectra of a variety of trimethylsilyl derivatives of aldonolactones, including the spectrum of 54. 

On studying the KDO content of LPS from Xanthomonas sinensis, Volk and coworkers64 found that only one KDO residue per LPS chain is present in this organism. Moreover, the authors observed the formation of 4,7- and 4,8-anhydro derivatives (39 and 40) of KDO (see Scheme 14) under the conditions used for mild hydrolysis of the LPS with acetic acid. Free KDO was also shown to yield the anhydro derivatives under analogous conditions. The structures of these unusual side-products were identified by mass spectrometry, as follows. Reduction of 39 and 40 with sodium borohydride gave the two epimeric mixtu.es, 41 and 42. These were subjected to periodate treatment followed by borohydride reduction, the products separated by paper electrophoresis, and their trimethylsilyl ether derivatives analyzed by... 

Gas chromatography-mass spectrometry has also been used to detect sorbitol [37]. The components were converted to the trimethylsilyl derivatives and separated on a capillary column. Sorbofviranose, sorbopyranose, fructofuranose, fructopyranose, sorbitol, and 5-keto-sorbose were able to be identified in sorbose using the technique... 

Several methyl pento- and hexo-pyranosides have been studied as trifluoroacetates in connection with mass spectrometry,391 and the retention times of 41 glycosides as their trifluoroacetates have been compared with those of the O-trimethylsilyl and O-acetyl derivatives.387 In a study on sake, the separation of ethyl D-glucosides as these three derivatives was also compared.299... 

Similarly, there is an increasing degree of consistency of methodological approach between laboratories. For instance, a recent survey of those undertaking qualitative urinary organic acid analysis revealed that more than 90% (83 of 91) of laboratories indicated that they extracted the samples with ethylacetate or ethylacetate/ether, formed trimethylsilyl derivatives and employed gas chromatography-mass spectrometry as a means of analysis. 

Fig. 5.1.3 Sterol analysis in patients with defective cholesterol biosynthesis. Gas chromatography-mass spectrometry analysis of trimethylsilyl derivatives of sterols extracted from primary skin fibroblasts of a control subject, a Smith-Lemli-Opitz syndrome (SLOS) patient, and a Con-radi-Hunermann syndrome (CDPX2) patient, and lymphoblasts of a desmosterolosis patient cultured in lipoprotein-deficient medium reveals the accumulation of sterol intermediates indicative of a defect in cholesterol biosynthesis. Similar spectra can be obtained by sterol analysis of the plasma of such patients...

Several enzymes catalyze stepwise removal of amino acids from one or the other end of a peptide chain. Carboxypeptidases232 remove amino acids from the carboxyl-terminal end, while aminopeptidases attack the opposite end. Using chromatographic methods, the amino acids released by these enzymes may be examined at various times and some idea of the sequence of amino acids at the chain ends may be obtained. A dipeptidyl aminopeptidase from bovine spleen cuts dipeptides one at a time from the amino terminus of a chain. These can be converted to volatile trimethylsilyl derivatives and identified by mass spectrometry.233 If the chain is shortened by one residue using the Edman degradation (Section 3) and the dipeptidyl aminopeptidase is again used, a different set of dipeptides that overlaps the first will be obtained and a sequence can be deduced. Carboxypeptidase Y can be used with MALDI mass spectrometry to deduce the C-terminal amino acid sequence for a peptide. However, He and Leu cannot be distinquished. 

There are a number of gas chromatographic procedures for the determination of the catecholamines. Methods generally accepted are making the trimethylsilyl ether derivative of the alcoholic group after using diazomethane to prepare the methyl ester and the heptafluorobutyryl derivative. The ethyl esters have been used for the separation of HVA and isoHVA and mass spectrometry applied to study their characterization. 

Analysis of Freshly Cyclized 2,3-di-O-methyl-D-arabinose. The system 3,4-di-O-methyl-D-mannitol (2)—sodium metaperiodate meets the foregoing specifications. 3,4-Di-O-methylmannitol was rapidly cleaved by periodate to 2,3-di-O-methyl-D-arabinose (3), which is resistant to further oxidation (19). We prepared the crystalline / -anomer of this sugar (the a-anomer had previously been crystallized (20)) and showed that on a suitable GLC column the trimethylsilyl derivatives of the four ring forms could be separated (Figure 9). The individual peaks were characterized by preparative GLC and mass spectrometry. This allowed the analysis of the mixtures of anomeric forms generated in kinetic experiments (see p. 34). 

The relationship between structure and paper-chromatographic mobility of aldono-1,4-lactones has been discussed.65 Butanone, saturated with water, is suitable for the preparative separation of lactones on cellulose columns free acids and reducing sugars move very slowly in this system. Separation of aldono-1,4-lactones and of aldonic acids as their O-(trimethylsilyl) derivatives has been accomplished.66 The mass spectra of such derivatives are characteristic, so that it is possible to identify aldonic acids67 and lactones68 by means of combined gas chromatography-mass spectrometry. 

G. Peterson, Mass spectrometry of aldonic and deoxyaldonic acids as trimethylsilyl derivatives, Tetrahedron, 26 (1970) 3413-3428. 

Melphalan has been converted to its trimethylsilyl derivative with bis(trimethylsilyl)acetamide and has been analyzed by GC on a 1.8 m x 3 mm column packed with 2.5% (w/w) SE-54 on acid-washed, silanized Chromosorb W (80-100 mesh) at 210° (injector temperature, 250° flame ionization detector temperature, 215°) using nitrogen as the carrier at 30 ml/min. The order of elution from a partly hydrolyzed mixture was melphalan, mono-hydroxy-derivative VI and di-hydroxy-derivative VII (Scheme III). The same elution order was obtained on a SE-30 column it was reversed on a more polar liquid phase (OV-17). Identification of the peaks was done by mass spectrometry [52]. 

For example, glucose would be more likely to char and decompose inside the injector of a gas chromatograph, rather than to vaporize and flow through the column with the gas phase. The trimethylsilyl derivative of glucose is more volatile, however, and it vaporizes at a low enough temperature to survive gas chromatography and mass spectrometry. 

The use of mass spectrometry is clearly the most unambiguous approach to elucidate the structures of low-molecular-weight PBN adducts. Abe et al. [130] have previously analyzed the structures of trimethylsilyl derivatives of adducts of PBN and POBN. Of interest was the detection of the bis-trimethylsilylated hydroxyl adduct of POBN. From the mass-spectral data, the POBN/ OH adduct... 

In the human female, whose pituitary hormones may be suppressed by the use of oral contraceptives, the ratio of testosterone to creatinine in urine may be used. Alternatively, a method suitable for both males and females is to measure the ratio of total testosterone to epitestosterone using gas chromatography—mass spectrometry. In this method, the bis(trimethylsilyl) derivative is formed and the intensity of the molecular ions at m/z 432, under electron impact conditions for both of the steroid derivatives, is used to determine the ratio (M. Donike and J. Zimmermann, J. Chromat, 1980, 202, 483-486). The internationally accepted limit for the ratio is currently 6. 

Gas Chromatography-Mass Spectrometry. Prepare methoxime derivatives by heating the extract from the thin-layer chromatographic plate with 100 xl of an 8% solution of methoxyamine hydrochloride in dry pyridine at 60° for 30 minutes, and evaporate in a rotary film evaporator. Silylate by dissolving the residue in 100 Lll of chloroform, adding 100 Lll of A,0-bis(trimethylsilyl)acetamide and 20 Lll of trimethylchlorosilane, then seal, and heat for 2 hours at 60°. When only 5a-estrane-3P,17a-diol is to be confirmed the methoxime formation can be omitted. Prepare a 2-cm column of Sephadex LH-20 in a Pasteur pipette with a cotton wool plug, using a... 

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