Volatile aroma components were extracted from freshly prepared apple juice. In three cultivars investigated (Elstar, Jonagold, Jonagored), the aroma contents of organically produced apples were ...significantly lower compared to conventionally produced apples.
Summary
Volatile aroma components and contents of organically and conventionally produced apples of the cultivars Elstar, Jonagold, Jonagored and Braeburn were studied. In three cultivars investigated, the aroma contents of organically produced apples were significantly lower (Elstar 16%, Jonagold 29%, Jonagored 68%). For Braeburn, no statistically significant difference was observed. In particular, the main aroma components were present at much lower concentrations in organically produced apples. In all apple cultivars, these were hexanal, trans‐2‐hexenal, 2‐methylbutylacetate and hexylacetate. twenty‐three aroma components were identified in total, in different relative ratios in the different apple cultivars: saturated esters, saturated and unsaturated aldehydes and alcohols. Some components identified in the conventionally produced cultivars were not present in the organically produced cultivars at all. The aroma components were extracted from juice freshly prepared from the apples by stir bar sorptive extraction (SBSE) technique and characterised by FID gas chromatography and EI/CI TOF mass spectrometry.
Chemical degradation of guar gum solutions via the addition of a strong oxidant is a common process step in hydraulic fracturing. Unfortunately, this degradation step leads to the formation of an ...insoluble precipitate which clogs the porous rock formation, reducing efficiency, reducing oil recovery potential, and increasing energy costs. The chemical composition, particle size, and molecular weight distributions of the oxidatively degraded guar (“broken guar”) are largely unknown, making it difficult to develop mitigation strategies. In this work, broken guar gum solutions are systematically analyzed to understand the origin of the observed residue. Our results indicate that cellulose fibers and proteins, rather than galactomannan oligomers, are the two major components (>50%) of the solid residue (the water‐insoluble fraction of broken guar). This finding suggests that removal of the cellulose fiber and proteins from the guar source material may be a potential residue mitigation strategy. Separately, we provide evidence for a potential second mitigation strategy employing chemical additives to reduce aggregation of the insoluble species, effectively reducing their potential to cause formation damage.
Aqueous solutions of guar gum were cleaved by ammonium persulfate and analyzed by monad and protein analyses. Surprisingly, insoluble cellulose fibers and proteins, rather than galactomannan oligomers, were the major components of the water‐insoluble fraction.
Three hydroxypropyl methylcellulose samples (HPMC1–3, DS
Me
= 1.45, 1.29, and 1.36; MS
HP
= 0.28, 0.46, and 0.84) were analyzed with respect to their methyl and hydroxypropyl substitution pattern ...in the polymer chains. Ionization yield of HPMC oligomers in electrospray ionization ion trap mass spectrometry (ESI-IT-MS) is strongly influenced by the hydroxypropyl pattern. Therefore, a sample derivatization procedure, as well as suitable measurement conditions that enable relative quantification were elaborated. Analysis was performed by negative ESI-IT-MS after per(deutero)methylation, partial depolymerization, and reductive amination with
m
-aminobenzoic acid. Measurement parameters like solvent,
trap drive
, and voltages of the ion transportation unit were studied with regard to the suitability for quantitative evaluation. Using direct infusion of the samples, strong influence of trap drive and octopole settings was observed. Optimized measurement conditions were used for the determination of the HP pattern of the permethylated samples by direct infusion. The methyl pattern was determined from the perdeuteromethylated samples by high-performance liquid chromatography–electrospray tandem mass spectrometry. For HPMC1, substituents were both found to fit the random distribution model. The other two samples showed pronounced heterogeneity which could be interpreted in more detail by extracting methyl subpatterns depending on the number of HP groups.
Figure
Determination of the substituent distribution in hydroxypropyl methylcellulose oligomers by ESI-IT-MS (negative mode) after labeling with m-aminobenzoic acid
•LC × LC-HRMS methods developed for the characterization of complex polyether polyols.•Various isomeric distributions of castor oil ethoxylates were resolved using LC × LC.•LC–MS/MS revealed ...characteristic fragmentation patterns of such isomers.•Differentiation based on terminal or internal positioning of fatty-acid moieties.
Polyether polyols are often used in formulated systems, but their complete characterization is challenging, because of simultaneous heterogeneities in chemical composition, molecular weight and functionality. One-dimensional liquid chromatography–mass spectrometry is commonly used to characterize polyether polyols. However, the separation power of this technique is not sufficient to resolve the complexity of such samples entirely. In this study, comprehensive two-dimensional liquid chromatography hyphenated with high-resolution mass spectrometry (LC × LC-HRMS) was used for the characterization of (i) castor oil ethoxylates (COEs) reacted with different mole equivalents of ethylene oxide and (ii) a blended formulation consisting of glycerol ethoxylate, glycerol propoxylate and glycerol ethoxylate-random-propoxylate copolymers. Retention in the first (hydrophilic-interaction-chromatography) dimension was mainly governed by degree of ethoxylation, while the second reversed-phase dimension resolved the samples based on degree of propoxylation (blended formulation) or alkyl chain length (COEs). For different COE samples, we observed the separation of isomer distributions of various di-, tri- and tetra-esters, and such positional isomers were studied by tandem mass spectrometry (LC–MS/MS). This revealed characteristic fragmentation patterns, which allowed discrimination of the isomers based on terminal or internal positioning of the fatty-acid moieties and provided insight in the LC × LC retention behavior of such species.
A GC-MS method for the determination of bisphenol-A (BPA) in water has been developed and validated for a concentration range of 5.0 m 514.8 ng/L. In contrast to hitherto published methods we report ...validation data in detail for the entire applicable concentration range of the developed method. The method employs liquid/liquid extraction for analyte and internal standard isolation and concentration. The D 8 -BPA analog is used as surrogate standard to increase method accuracy and precision. The identity confirmation of BPA is performed using the ion intensity ratios of the molecular ion and the M-15 fragment. Trifluoroacetylation of BPA and D 8 -BPA is employed in order to obtain less polar derivatives. As a result of the derivatization narrow and symmetrical gas chromatographic peaks are obtained which allow the quantification of very small amounts of BPA. The relative recoveries of BPA are greater than ninety percent over the entire validated concentration range. The method quantification limit is 5.0 ng/L BPA, which is the lowest validated concentration. The impact of suspended particulate matter frequently present in surface water samples on the quantification results could be demonstrated. It was shown that false positive results can be obtained due to losses of the surrogate standard by adsorption on the particulates present.
The alditol acetate method is a common procedure for sugar analysis, also applied to determine the substituent distribution in monomer units of polysaccharide ethers like methyl cellulose by gas ...liquid chromatography. Consisting of several preparation and work-up steps this procedure is both time consuming and prone to side reactions that promote discrimination of single constituents, especially when no peralkylation step is performed prior to hydrolysis. As a consequence results scatter in dependence on individual treatment and conditions. In the context of this work these critical points were overcome by strict but simplified work-up procedures and using acid instead of alkaline catalyzed acetylation. Under the acidic conditions the tedious removal of borate is no longer necessary and a reduced time requirement was achieved as well as good reproducibility. Comparison with independent reference methods excluded a systematic error of the method and confirmed the results obtained. Without peralkylation, i.e. in the presence of free hydroxyl groups, another fast modification of the method using DMSO as solvent, no removal of borate, and 1-methylimidazole as catalyst for acetylation was found to produce a systematic error.
Hydroxyethylmethyl celluloses (MSHE 0.15–0.26, DSMe 1.49–1.82) and hydroxyethyl celluloses (MSHE 1.89–3.03) are analyzed with respect to their substituent distribution in the polymer chains. The ...cellulose ethers are peralkylated and partially hydrolyzed, and are analyzed by electrospray ionization‐ion trap‐mass spectrometry (ESI‐IT‐MS). The randomness of the partial hydrolysis is proven. Quantitative evaluation of their mass spectra becomes possible after labeling the oligosaccharides at the reducing end. Reductive amination with o‐aminobenzoic acid gives better results than hydrazone formation with cationic Girard's T reagent. Syringe pump infusion gives more‐accurate results compared with liquid chromatography (LC)‐ESI‐MS. Profiles of the substituent distribution in the oligosaccharide fractions of DP 2–DP 7 are compared with the theoretical random distribution of glucosyl units in the chain.
Substituent distribution of hydroxyethyl groups in cellulose ethers in the polymer chain is important to understand the properties. A new sample preparation allows the analysis of hydroxyethyl(methyl)‐celluloses (HEMCs) and HECs in a wide molar degree of substitution (MS) range by electrospray ionization‐ion trap‐mass spectrometry (ESI‐IT‐MS).
Substituent patterns in oligosaccharide derivatives obtained from methyl cellulose were determined up to DP10 by electrospray ionization mass spectrometry employing separation of the oligomer ...fractions by HPLC. Oligosaccharides were labeled with meta-aminobenzoic acid after perdeuteromethylation and partial hydrolysis of methyl cellulose, enabling simultaneous quantification according to DP by HPLC/UV. Control of the HPLC-method was performed with a defined oligomer mixture obtained from β-cyclodextrin. Results from LC-ESI-MS are discussed in comparison with those from syringe pump injection and compared to a calculated pattern for a random distribution. Programing of instrumental parameters optimized for each DP and avoidance of competition of successively eluting analytes in the electrospray process allowed extension of the established method for determination of the substitution pattern of cellulose derivatives along the polymer chain from DP5 to DP10 and thus a significant gain of information.
Substituent patterns in oligosaccharide derivatives obtained from methyl cellulose were determined up to DP10 by electrospray ionization mass spectrometry employing separation of the oligomer ...fractions by HPLC. Oligosaccharides were labeled with
meta-aminobenzoic acid after perdeuteromethylation and partial hydrolysis of methyl cellulose, enabling simultaneous quantification according to DP by HPLC/UV. Control of the HPLC-method was performed with a defined oligomer mixture obtained from β-cyclodextrin.
Results from LC-ESI-MS are discussed in comparison with those from syringe pump injection and compared to a calculated pattern for a random distribution. Programing of instrumental parameters optimized for each DP and avoidance of competition of successively eluting analytes in the electrospray process allowed extension of the established method for determination of the substitution pattern of cellulose derivatives along the polymer chain from DP5 to DP10 and thus a significant gain of information.
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