Derivatization Yield Research Articles

Chromatographic trace analysis of some organic compounds in the environment using derivatization—sorption concentration techniques : I. Gas chromatographic analysis of acrylates in air

Derivatization-sorption concentration techniques for the gas chromatographic analysis of acrylates are described. Acrylates are accumulated and derivatized in the trapping absorber. The sorption and derivatization yield of thioethers is 71 ± 2.6%. Two different procedures are recommended: (1) direct selective derivatization—sorption, and (2) universal sorption of all organic compounds in the first step, followed by a thermal desorption and selective derivatization in the second step.

Gas chromatographic determination of isocitric and malic acid in the presence of a large excess of citric acid

Derivatization yields of different esters (methyl, ethyl, n-propyl, isopropyl, n-butyl and isobutyl) of citric, malic and isocitric acids with various acylating agents, such as acetic anhydride, propionic anhydride, trifluoroacetic anhydride and heptafluorobutyric anhydride, were investigated. The formation of acylated malic and isocitric acid esters is rapid and quantitative whereas the acylation of citric acid esters was slow and partial in most instances. It was found that selective analytical conditions can be achieved with the O-heptafluorobutyryl n-butyl esters. The analytical applicability of the separation and determination of the malic, isocitric and citric acid contents of model solutions and of pressed lemon juice is discussed. Concentrations of 1.2 × 10 −3 −9.0 × 10 −3g per 100 g of isocitric acid and 4.2 × 10 −3 −3.5 × 10 −2 g per 100 g of malic acid in the presence of 9.3 × 10 −1 g per 100 g of citric acid were measured with relative standard deviations of 7.5 and 4.2%, respectively.

Gas chromatographic analysis of norcantharidin and related compounds using derivatization to imides

Derivatization to imides has been studied for determining α,β-diacids or corresponding anhydrides (e.g. norcantharidin) as well as for analysing primary amines by gas chromatography. 2-Naphthylaniline, n-heptylamine, cyclohexamine, 2,5-dimethoxyaniline, 2,4,5-trichloroaniline, 3,5-dichloroaniline, aniline and benzylaniline were used as derivatization reagents. 1H-nuclear magnetic resonance and mass spectrometry data were obtained for the norcantharidin N-imides synthesized. Factors such as derivatization yields, linearity, reproducibility and sensitivity were evaluated. The influences of reaction temperature and solvent were investigated.

Immobilisierung von geschützten nucleosiden und mononucleotiden an funktionalisierte perlcopolymerisationsprodukte aus methylacrylat und 1,4-bis(vinyloxy)butan

Protected nucleic acid components were coupled to eight differently functionalized bead copolymers, prepared from methyl acrylate and 1,4-bis(vinyloxy)butane, via amid-, urea-, phosphotriester- or carboxylic acid ester linkages. The immobilization was performed by methods used in nucleic acid chemistry. The obtained gels carry 1 to 300 μmol per gram of nucleoside or nucleotide derivatives. The yield of derivatization was found to be first of all determined by steric effects of the gel matrix, the size of the nucleic acid component and the route of synthesis selected. Anchor groups, arranged via long spacers, were not effective for the immobilization of nucleic acid components. A “carboxylate-gel” which can immobilize 300 μmol per gram of a nucleoside derivative may serve as support in the solid phase synthesis of oligonucleotides in large scale.

Liquid chromatographic determination of the enantiomeric composition of amphetamine and related drugs by diastereomeric derivatization.

A procedure is described for the derivatization of amphetamine and methamphetamine enantiomers with 4-nitrophenylsulfonyl-(S)-prolyl chloride. The resulting diastereomeric amphetamine derivatives were resolved by a reversed-phase procedure. The derivatization yield was maximized in the 95% range using a five-fold molar excess of the chiral derivatizing agent and an approximate 18 to 1 ratio of base (NaHCO3) to total acid generated in the reaction.

Ethylation of inorganic anions, phenols and carboxylic acids for gas chromatographic determination

Some inorganic anions, phenols and carboxylic acids were converted into their ethyl derivatives by reaction with diethyl sulphate, and the ethyl derivatives then determined by gas chromatography with flame ionization detection. For phenols and carboxylic acids, 18-crown-6 was employed as a catalyst for the derivatization reaction. It was observed that 18-crown-6 significantly increases the derivatization yields of phenols and carboxylic acids. From a comparison of this ethylation procedure with the corresponding methylation using dimethyl sulphate, it is concluded that ethylation is more suitable for the determination of sulphide, iodide, phenols and carboxylic acids.

Quantitative gas chromatographic determination of low-molecular-weight straight-chain carboxylic acids as their p-bromophenacyl esters after extractive alkylation in acidic medium

The measurement of acetate by gas chromatography at low concentrations in biological fluids is a difficult task. A significant improvement can be brought about by derivatization of acids as p-bromophenacyl esters. By such a procedure, the determination of low-molecular-weight straight-chain carboxylic acids (acetic, propionic and butyric acids) was enhanced with respect to sensitivity and specificity. The volatile fatty acids were esterified by means of an extractive alkylation mechanism in acidic conditions from ageous solutions. Tetrahexylammonium was used as counter-ion and and the alkylating agent was a, p-dibromoacetophenone. The phenacylation reaction was studied with respect to pH, concentration of counter-ion and kinetics. The yield of derivatization was ca. 70% after 2 h at 42°C. A mass spectrometry study was performed in order to ascertain the structure of derivatives using electron impact and chemical ionization. The gas-liquid chromatrographic behaviour of the p-bromephenacyl esters of acetic, propionic and butyric acids was studied on an OV-225 packed column and an OV-1 capillary column. Flame ionization detection was shown to be linear between 0.2 and 4 nmol injected, with a quantitative limit of detection of 31 pmol ( i.e. 1.8 ng of acetic acid).

Gas chromatographic determination of trace amounts of inorganic mercury

A procedure for the gas chromatographic (GC) determination of trace amounts of inorganic mercury is described. Hg 2+ is converted into diphenylmercury (DPM) with tetraphenylborate and the DPM is extracted with toluene. The derivatization yield was measured radiochemically and by GC and was found to be between 95 and 100% for amounts of Hg 2+ in the range 50 ng–10 μg, and was not affected by K + and Cl − ions or matrix effects due to decomposed tissue. At the nanogram level, derivatization at a low pH is advisable, which may be restricted by the instability of the reagent in acidic medium. DPM was determined by GC on specially pre-treated columns with OV-17 or ethylene glycol succinate as the liquid phase. The detection limit was 45 pg of Hg 2+ (absolute) using a tritium electron-capture detector.

Gas—liquid chromatographic analysis of nucleic acid components

The aim of this investigation was to develop a quantitative gas—liquid chromatographic method of analysis for the components of nucleic acids ( i.e., purine and pyrimidine bases, nucleosides, or nucleotides), and to apply this method to the analysis of biological material. The N-methyl derivatives of the purine and pyramidine bases, prepared by thermal dissociation of their tetramethylammonium salts were found to be unsuited for quantitative analysis due to the formation of multiple chromatographic peaks for cytosine, adenine, and guanine. The trimethylsilyl (TMS) derivatives of the bases were found to be far superior to the N-methyl compounds. Bis(trimethylsilyl)acetamide(BSA) was evaluated and found to be good reagent for silylation of the bases. The optimum derivatization conditions were heating the bases in a closed tube at 150° for 45 min, with a 100 molar excess of BSA to total bases, and a 3:1 v/v acetonitrile/BSA ratio. Calibration curves for the five main bases (U, T, C, A, and G) were prepared and found to be linear over a sample weight range 25–2000 μg of base. The relative standard deviations ranged from 1.1% for uracil 3.1% for cytosine. The minimum detectable amount (MDA) using the hydrogen flame ionization detector, was determined to be 3 or 5 × 10 −9 g i or ca. 3 × 10 −11 moles of each base injected. Comparative studies were made of BSA as a silylation reagent with bis(trimethylsilyl)trifluoroacetamide (BSTFA), and reagent solutions of 0.1 v/v% TMCS in BSA, and 1.0 v/v% TMCS in BSA. There were no significant differences in regard to analytical derivatization yield with any of this reagents. Important advantages of BSTFA include “cleaner” chromatograms with fewer extraneous peaks and complete miscibility of BSTFA in the solvent. A column of 8 w/w% SE-30 on 100–120 mesh Supelcoport provided good resolution and stability for the TMS bases and was superior to all chromatographic columns investigated. Application of the developed method to the analysis of biological materials was accomplished using perchloric acid hydrolysis and anion-exchange removal of the bases from biological background prior to derivatization and GLC analysis. The combined hydrolysis and purification procedures were shown to give a recovery of the bases of ca. 82 % with the recovery of the four bases being equivalent (± 1.5 %). Base ratio analysis of purified yeast RNA showed that the method was precise giving an average relative standard deviation of 3.0 %. Experiments are in progress on the analysis of microgram amounts of RNA and DNA.