Characterization of triacylglycerols in the seeds ofAquilegia vulgaris by chromatographic and mass spectrometric methods

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Optimization of the mass spectrometric analysis of triacylglycerols using negative-ion chemical ionization with ammonia

Conditions for the mass spectrometric analysis of triacylglycerols,via direct exposure probe, with ammonia negative-ion chemical ionization were optimized. Triacylglycerols were most favorably ionized, using the reactant gas pressure of approximately 8500 mtorr at the ion source temperature of 200°C with the instrumentation used. Abundant [M-H]⁻ ions were produced under these conditions without the formation of [M+35]⁻ cluster ions, which would interfere with the molecular weight region of triacylglycerols in the spectra. A rapid desorption of the sample from the probe wire is recommended, using a relatively high heating rate (approximately 40 mA s⁻¹), to minimize thermal degradation of unsaturated molecules and the reducing effect of double bonds on the mass spectrometric response of triacylglycerols. Furthermore, the abundance of [M-H]⁻ ion was enhanced by rapid heating, which we found to be important to improve the sensitivity. The appropriate amount of sample applied to the rhenium wire was in the region of 50–300 ng for one determination, i.e., only a few nanograms of a single triacylglycerol is required for production of a reliable spectrum. The reproducibility of the method was good as demonstrated with standards and a raspberry seed oil sample. The described mass spectrometric method is a fast and potentially useful tool for semiquantitative determination of triacylglycerol mixtures of various fats and oils. The discrimination, caused by differences in molecular size and unsaturation of triacylglycerols with 50 to 56 acyl carbons, was negligible under our optimized ionization conditions, thus, no correction factors were needed. These findings have not yet been verified with instruments in other laboratories. However, the present study shows how the analysis of triacylglycerols can be improved, regardless of the instrument, by optimization of the analytical conditions.     

Comparison of UOP-326, voltammetric and gas chromatographic/mass spectrometric methods for the determination of conjugated dienes in Brazilian Naphtha

The content of conjugated dienes is one of the most important factors in determining the quality of gasoline. Owing to their easy polymerization, the presence of these compounds decreases the quality of the product. Although the Brazilian Petroleum Industry still uses the UOP-326 method to determine the content of conjugated dienes, this method has some disadvantages such as long analysis time, incomplete reaction with some conjugated dienes and the interference of primary alcohols. The main objective of this work is to compare and evaluate the three methods (UOP-326, voltammetric and gas chromatographic/mass spectrometric) used for the determination of the conjugated dienes values in naphtha samples. Our results show that the voltammetric and gas chromatographic/mass spectrometric methods can be applied for the determination of conjugated dienes in naphtha samples. However, the voltammetric method is recommended for daily routine analysis because, in addition to being faster and more precise than the UOP-326 method, it is less expensive if compared to the gas chromatographic/mass spectrometric.     

New oxidation pathway of 3,5-di-tert-butyl-4-hydroxytoluene: An ionspray tandem mass spectrometric and gas chromatographic/mass spectrometric study

The autoxidation of 3,5-di-tert-butyl-4-hydroxytoluene (BHT, 1) in bar soap was investigated with ionspray tandem mass spectrometric and on-line gas chromatographic/mass spectrometric methods. The oxidation products of BHT were extracted from the bar soap surface, concentrated, and fractionated with open-column chromatography to remove the impurities. New oxidation products of BHT (BHT phenol-type dimer 7 and others) were identified with the two mass spectrometric methods. The results suggested that oxidation of BHT in bar soap occurred in a way different from that in the previous studies. In the new pathway, oxidation of BHT first generates an excited state of phenol-type dimer 4, and then this species decomposes, due to its high energy, to form dimer 7. The mechanism of oxidation is discussed.     

Isothermal pyrolysis of cellulose: Kinetics and gas chromatographic mass spectrometric analysis of the degradation products

Untreated and fire-retardant-treated white α-cellulose samples were isothermally pyrolyzed in a fluidized bath in a nitrogen environment at 298–360°C. Results were reported in terms of volatilization (based on weight loss-time measurements) and the degradation products (based on gas chromatographic–mass spectrometric analysis). The findings products (based on gas chromatographic–mass spectrometric analysis). The findings on untreated cellulose indicate that: (1) pyrolysis occurs in three distinct phases in the temperature range 276–360°C; (2) there is a single activation energy of 42 kcal/mole over this temperature range; (3) the initial rapid weight loss is not due to the desoprtion of water, but primarily to decomposition of the cellulose; molecules: (4) there is little difference in either the quality or relative quantity of the volatiles generated during the three different phases of pyrolysis. The findings on treated cellulose show that the fire retardant, KHCO₃, does not markedly change the types of degradation products having molecular weights below about 110, althought it does change their relative concentrations. Furthermore, the rate of product generation and the quantity of residual char are increased.     

Characterization of side-chain oxidation products of sitosterol and campesterol by chromatographic and spectroscopic methods

Based on the cholesterol-lowering effects of phytosterols, known since the 1950s, extra phytosterol amounts have been added to certain food products for almost 10 yr. Literature reports on oxidation of phytosterols in general are limited, and data on side-chain oxidation of these compounds are scarce. The aim of this study was to investigate and characterize autoxidation products from a mixture of the two phytosterols sitosterol and campesterol. A commercial mixture of the two sterols was oxidized for 72 h at 120°C in an air-ventilated oven. The oxidation products were separated by preparative TLC and identified and characterized with GC-MS. The following oxidation products were identified from the two phytosterols: 24-methylcholest-5-en-3β,24-diol, 24-methylcholest-5-en-3β,25-diol, 24-methylcholest-4-en-6α-ol-3-one, 24-methylcholest-4-en-6β-ol-3-one, 24-ethylcholest-5-en-3β,24-diol, 24-ethylcholest-5-en-3β, 25-diol, 24-ethylcholest-4-en-6α-ol-3-one, 24-ethylcholest-4-en-6β-ol-3-one. Full-scan mass spectra of these compounds are reported for the first time as their trimethylsilyl-ether derivatives.     

Characterization of triacylglycerols in madeira laurel oil by HPLC-atmospheric pressure chemical ionization-MS

Madeira laurel oil was fractionated by liquid extraction combined with TLC, and TAGs were analyzed by HPLC coupled with atmospheric pressure chemical ionization-MS (APCI-MS). Eluted molecular species compositions of the eluted TAG in the complex natural mixture were determined by GC identification of FAME and byLC-atmospheric pressure chemical ionization (APCI)-MS analysis of the lipid. The APCI-MS spectra of most TAG exhibited [M+H]⁺ and [M−RCOO]⁺ ions, which defined the M.W. and the molecular association of fatty acyl residues, respectively. Despite the relatively high degree of saturation, with a saturated/unsaturated ratio of 0.70, no totally saturated TAG nor mixed asymmetric TAG with two saturated FA (SSM or SSU, where S is saturated, M is monounsaturated, and U is unsaturated) were found. This type of molecular structure provides a possible explanation for the relatively low m.p. (12–15°C) and also the high oxidative resistance observed.     

Positional distribution of Δ5-acids in triacylglycerols from conifer seeds as determined by partial chemical cleavage

The positional distribution of various Δ5-acids in the seed triacylglycerols from several conifer species has been established after partial chemical degradation with Grignard reagent. The species studied were representative of four conifer families and were specially selected for their particularly high Δ5-acid contents. These species were Taxus baccata (Taxaceae; 5,9-18:2 acid, 11.9%), Larix decidua (Pinaceae; 5,9,12-18:3 acid, 28.5%), Sciadopytis verticillata (Taxodiaceae; 5,11,14-20:3 acid, 16.7%), and Juniperus communis (Cupressaceae; 5,11,14,17-20:4 acid, 19.8%). Calculations from the fatty acid compositions of triacylglycerols and of the mixture of 1,2- and 2,3-diacylglycerols generated by the Grignard reagent indicated that, for the four species, there was a considerable enrichment of Δ5-acids (generally more than ten times) in the 1,3-positions as compared to the 2-position, where Δ5-acids represented always less than 2% of total fatty acids esterified to triacylglycerols. This distribution was practically independent from the species (four families studied), the chainlength (18 or 20 carbon atoms), and the number of ethylenic bonds (two to four) in the Δ5-acids. Similar distributions were established for triacylglycerols from the seeds of three pine species that are available on a ton-scale: Pinus pinea, P. koraiensis, and P. pinaster. These observations confirm and extend previous studies conducted with other conifer species by similar techniques or by ¹³C-nuclear magnetic resonance spectroscopy. Consequently, the almost exclusive location of Δ5-acids in the external positions of triacylglycerols is now well established and appears to be a general feature of conifer seed oils.     

Analysis of triacylglycerols by silver-ion high-performance liquid chromatography-atmospheric pressure chemical ionization mass spectrometry

Triacylglycerols of the seed oils rich in α- and/or γ-linolenic acid moieties were separated by silver-ion high-performance liquid chromatography (HPLC) followed by on-line atmospheric pressure chemical ionization-mass spectrometric (APCI-MS) detection. Mass spectra of most triacylglycerols exhibited abundant [M + H]⁺ and [M − RCO₂]⁺ ions, which defined the molecular weight and the molecular association of fatty acyl residues of a triacylglycerol, respectively. Silver ions formed weaker complexes with triacylglycerols containing γ-linolenic acid than with those containing α-linolenic acid, i.e., the elution order of molecules wasXYT _γ>XYT _α’,XT _γ T _α>XT _α T _α>, andT _γ T _γ T _γ>T _γ T _γ T _α>T _γ T _α T _α>T _α T _α T _α, whereT _α=α-linolenic acid,T _γ=γ-linolenic acid, andX, Y=fatty acids different from linolenic acid. Furthermore, silver-ion HPLC resulted in partial separation within equally unsaturated triacylglycerols according to differences in the combined number of acyl carbons. Regioisomeric forms of triacylglycerols were not determined from the seed oil samples, although differences were measured with reference compounds in the relative abundances of [M − RCO₂]⁺ ions formed by a loss of a fatty acyl residue from thesn-2 position and thesn-1/3 positions. Silverion HPLC/APCI-MS provided valuable information for structure elucidation of seed oil triacylglycerols: 43 molecular species were identified from cloudberry seed oil, 39 from evening primrose oil, 79 from borage oil, 44 from alpine currant, and 56 from black currant seed oils. The quantitation requires to be studied further, especially in those cases where several molecular weight species of triacylglycerols eluted in a single chromatographic peak.     

Regiospecific determination of short-chain triacylglycerols in butterfat by normal-phase HPLC with on-line electrospray-tandem mass spectrometry

This study uses normal-phase HPLC with on-line positive ion electrospray mass spectrometry (ESI-MS) to obtain quantitative compositional data on both synthetic and butterfat short-chain TAG. The product ion tandem MS of standards averaged 11.1 times lower in abundance of the ion formed by cleavage of FA from the sn-2-position for the pairs of regioisomers in the TAG classes: L/L/S-L/S/L and L/S/S-S/L/S, where L denotes long and S short acyl chain (C₂−C₆). The molar correction factors, determined for 42 regioisomeric pairs of short-chain TAG of 20 randomized mixture of standards, differed by 1.4–80% as the ratios varied between 0.217 and 5.847. Butterfat TAG were resolved into four fractions on short flash chromatography grade silica gel columns. Pairs of regioisomers in the TAG classes L/S/S-S/L/S with predominance of L/S/S isomers and the sole regioisomers in the TAG classes L/L(M)/S were identified by tandem MS, where M denotes either 8∶0 or 10∶0 acyl chain. The total proportion of L/L(M)/S isomers was estimated at 34.7 and that of L/S/S-S/L/S at 1.0 mol%, including a small proportion of S/S/S. In contrast to previous work, the present data indicate the presence of a small proportion of butyric and caproic acids in the sn-1-position. The overall distribution of the FA in the short-chain TAG of butterfat, calculated from direct MS measurements, was consistent with the results of indirect determinations based on stereospecific analyses of total butterfat.     

Determination of the structure and composition of clinically important polyurethanes by mass spectrometric techniques

Curie-point pyrolysis mass spectrometry (Py-MS) and direct probe pyrolysis high resolution mass spectrometry (Py-HRMS) were used to identify the components and additives used in the synthesis and compounding of Biomer, Lycra Spandex, Tecoflex, and Pellethane. Two types of Biomer were identified (P and Q, our notation) which are composed of poly(tetramethylene glycol) (PTMG) capped with 4,4′-methylenebis(phenylisocyanate) (MDI) and chain-extended with ethylenediamine (EDA). Both forms contain 4,4′-butylidene-bis-(6-t-butyl-m-cresol) antioxidant, and Biomer Q also contains an additive which appears to be a quaternary ammonium chloride salt. Lycra Spandex was found to be identical to Biomer Q, with the exception that a low molecular weight polydimethylsiloxane oil is also present. This silicone oil can be removed by solvent extraction. Tecoflex (type SG80A) is composed of PTMG capped with 4,4′-diisocyanatodicyclohexylmethane and extended with 1,4-butanediol (BD). An industrial grade and a medical grade of Pellethane were analyzed. Both were composed of PTMG capped with MDI and extended with 1,4-butanediol. the industrial grade also contains an antioxidant, possibly butylated diphenylamine.     

One-pot synthesis of fatty acid epoxides from triacylglycerols using enzymes present in oat seeds

In our previous work we used ground oat (Avena sativa) seeds as an inexpensive source of enzymes for the modification of FA or their chemical derivatives. We have extended this work by observing the products derived from an intact fat and three vegetable oils through the concerted action of oat seed enzymes. A modified reversed-phase HPLC protocol was devised that allowed the quantification of FFA, epoxy FA, and acylglycerols without derivatization. It was found that the addition of the surfactant deoxycholate or calcium chloride was needed to observe best hydrolysis of TAG to FA. Without an added oxidant, lipase action produced up to 80% by weight of FA at pH 7–9 with small amounts of DAG and MAG. When the oxidant t-butyl hydroperoxide was added in the presence of deoxycholate, the FA were partially converted to epoxide derivatives (up to 35% by weight). When calcium chloride replaced deoxycholate, only 4% by weight of the product was epoxide derivatives. The highest levels of FA epoxides were generated at pH7, and up to 15% by weight of the product at this pH was epoxymonostearin (monoepoxyoctadecanoylglycerol). The optimal molar amount of t-butyl hydroperoxide to add with deoxycholate for high epoxide formation was 1.4 to 2.8 times the amount of fatty esters in soybean oil. In no instance were oxidized DAG or TAG detected, demonstrating that a highly specific enzymatic process was responsible for epoxide formation. The epoxide products may be used to produce polyols with high viscosity for grease preparations.     

Ring location in cyclopropane fatty acid esters by a mass spectrometric method

Ring location in cyclopropane fatty acid esters is accomplished simply and unequivocally with submilligram samples. The technique involves reductive ring opening with platinum catalyst and hydrogen in glacial acetic acid, to give a mixture of branched-chain and straight-chain acid esters. The sample is analyzed with a combination gas chrmatograph-mass spectrometer. Examination of the spectra obtained from the mixture of branched-chain acid esters permits assignment of the position of the methyl groups, and hence of the ring in the parent compound.     

Characterization of branched-chain fatty acids from fallow deer perinephric triacylglycerols by gas chromatography-mass spectrometry

Branched-chain fatty acids of perinephric triacylglycerols of semi-feral fallow deer (Dama dama dama) were analyzed by high resolution gas chromatography-mass spectrometry. Of the total fatty acids, 15.50% were Branched-chain components including 8.96% iso acids, mostly 14-methylpentacanoic acid, 2.85% anteiso acids and 1.73% of other monomethyl-substituted acids; dimethyl-branched acids with an iso structure (1.05%) and with an anteiso structure (0.18%) were also present. Whereas the predominant iso acids and methyl-substituted iso acids had chain lengths of 13 and 15 carbon atoms, the anteiso acids and methyl-substituted anteiso acids had chain lengths of 14 and 16 carbon atoms. Methyl substitution occurred on the even numbered carbon atoms relative to the carboxyl group. The general composition is also given of the fatty acids comprising the triacylglycerols of subcutaneous (rump area) and perinephric adipose tissue.     

Identification of milk fat triacylglycerols by capillary supercritical fluid chromatography-atmospheric pressure chemical lonization mass spectrometry

Identification of milk fat triacylglycerols was accomplished by capillary supercritical fluid chromatography (SFC) combined with atmospheric pressure chemical ionization mass spectrometry [(APCI)MS]. Supercritical carbon dioxide was the carrier fluid in SFC. Ionization was achieved by introducing vapor of ammonia in methanol into the ionization chamber, which resulted in the formation of abundant [M+18]⁺ and [M-RCOO]⁺ ions of triacylglycerols. These ions defined both the molecular weight and the fatty acid constituents of a triacylglycerol, respectively. SFC on a nonpolar stationary phase provided an efficient separation of triacylglycerols according to the combined number of carbon atoms in the acyl chains of a molecule. In addition to the identification of the major chromatographic peaks representing molecules with 26–54 acyl carbons, minor peaks representing triacylglycerols with an odd number of acyl carbons were separated and identified. Furthermore, compositional information on partially separated isobaric triacylglycerols, which differed substantially in the chain length of the fatty acyl residues, was achieved within some of the peaks. A new finding of the present study was the formation of abundant [M+18]⁺ ions of saturated triacylglycerols in addition to diagnostic fragment ions, being of primary importance in structure elucidation. This extends the applicability of capillary SFC-(APCI)MS in the analysis of both saturated and unsaturated triacylglycerols.     

Cationic copolymerization of phenyl glycidyl ether with lactones. Characterization of the reaction mixture with chromatographic methods

This paper refers to the influence of the catalysts boron trifluoride p-methoxyaniline complex (BF₃ · MA) and boron trifluoride etherate complex (BF₃ · Et₂O) having different reactivity in cationic copolymerization of phenyl glycidyl ether (PGE) with γ-butyrolactone (γ-BL) and ϵ-caprolactone (ϵ-CL), respectively. Reactions were followed by FT-IR, HPLC and SEC. SEC with multiple detection and Two-Dimensional-Chromatography HPLC/SEC were used to characterize the products in view to their copolymer compositions. In the presence of BF₃ · MA a preferred formation of spiroorthoesters (SOE) was observed; the polymerization of SOE under these conditions can be neglected. In case of the more reactive BF₃ · Et₂O the epoxide homopolymerization strongly competes with SOE formation, resulting in a product mixture of epoxide homopolymers (and in the case of ϵ-CL also lactone homopolymers) and copolymers with low lactone content.     

Purification of soybean trypsin inhibitors by means of chromatographic methods

The paper presents comparative studies on chromatographic purification of soybean trypsin inhibitors (STI) applying various polymer matrices. Two types of copolymers were tested: a copolymer of butyl acrylate with ethylene glycol dimethacrylate, and a terpolymer of acrylonitrile and butyl acrylate crosslinked with divinylbenzene. The investigations revealed that a similar purification extent is achieved in affinity chromatography with trypsin attached to both copolymers and in ion exchange chromatography when the matrices are aminated with ethylene diamine. The purification phenomenon was not so high for both unmodified matrices, and quite negligible for matrices hydrophilized by end-capping with tris(hydroxymethyl)aminomethane.     

Analysis of SO3-Sulfonation products of 1-Alkenes by spectrometric methods

The preparation and identification of four types of SO₃-sulfonated products of 1-alkenes are described.¹³C and, to a lesser extent,¹H nuclear magnetic resonance spectra are used to ascertain the structures of 2-alkenesulfonic acids, β-sultones (as 2-methoxyalkanesulfonic acids), γ- and δ-sultones. The mass spectra of some methyl 2-methoxyalkanesulfonates and 4-alkyl-δ-sultones are also studied. Sufficiently volatile mixtures are separated by gas liquid chromatography after methylation of the sulfonic groups.     

Biodesulphurization of a coal by packed-column leaching. Simultaneous thermogravimetric and mass spectrometric analyses

This study has two aims: to improve the biodesulphurization of a semi-anthracite by packed-column leaching by reducing the insoluble sulphate on the coal surface, and to determine whether after the combustion of treated and untreated coal, sulphate sulphur is transformed completely into sulphur dioxide or part remains in the ashes without reacting. Combustion tests were analysed by TG-MS. To reduce the precipitation of salts, two parameters are worked on: solution pH, which is reduced to 1.3, and the idle time between washes (ITBW), which is altered. After 125 days of treatment, comparison with the results of previous studies showed that the precipitated salt content was reduced pyritic desulphurization was increased up to 43%, and total desulphurization to 24%.     

Characterization of ferroelectrics by thermal wave methods

In this work, pyroelectric spatial profiles of SBN crystals, BaTi_1−xSn_xO₃ ceramics, and Pb(Zr,Ti)O₃ thin films were determined from the pyroelectric current spectrum caused by the interaction of thermal waves with the internal electric field and the unknown polarization distribution. For sinusoidal modulation, the pyroelectric current frequency dependence up to 10 MHz and phase shift between pyroelectric current and heat flux were analyzed to reconstruct the polarization distribution by solution of the Fredholm integral equation and by a Tikhonov regularization method for stable MATLAB numerical solutions. For the dynamic method with rectangular modulation, an approximate pyroelectric response in dependence on penetration depth was calculated. In this case, low modulation frequencies are required for the investigation of deep regions. Digital methods of signal processing were used to enable experiments below 1 Hz.