Analysis of the substituent distribution in the glucosyl units and along the polymer chain of hydroxypropylmethyl celluloses and statistical evaluation

Three hydroxypropylmethyl celluloses (HPMC 1, 2, 3; DS_Me=2.06, 1.99, 2.04; MS_HP=0.21, 0.19, 0.21) have been analyzed with respect to their methyl and hydroxypropyl pattern in the glucosyl units and along the polymer chain. The determination of the methyl pattern in the glycosyl unit was performed by GLC/MS after hydrolysis, reduction, and acetylation, while the distribution of hydroxypropyl residues in the monomers could be analyzed with higher sensitivity including a permethylation step prior to hydrolysis. To determine the distribution of the substituents along the polymer chain, a method developed for hydroxyethylmethyl cellulose (HEMC) was applied. This method comprises random partial acid hydrolysis after perdeuteromethylation and reductive amination with propylamine, followed by N- and O-alkylation, yielding completely alkylated and permanently charged oligosaccharide derivatives. These compounds could be quantitatively analyzed by means of matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS), since all discrimination effects related to the hydroxyalkyl groups are leveled off by the sample preparation procedure in combination with the choice of a MALDI-TOF instrument. Methyl data deviate to some extent from the random distribution calculated from the monomer composition, but in contrast to methyl cellulose (MC) or HEMC, it is not heterogeneous, but more regular. The distribution of HP groups is random within experimental error as has been found for HEMC as well.     

Methylation with sodium naphthalenide for the analysis of substituent distribution of trimethylsilyl celluloses and their evaluation

The substitution pattern of trimethylsilyl celluloses silylated withhexamethyldisilazane and N,N-dibutylamino­trimethylsilane was determined bymethylation analysis. Methylation with sodium hydride/methyl iodide wasaccompanied by significant desilylation because sodium hydride is alwayscontaminated with sodium hydroxide. Sodium naphthalenide prepared in tetrahydrofuran under anhydrous reaction conditions alloweda reduction of the extent of desilylation to less than 10 percent. In allcases preferred silylation of the 6-position was found. Celluloses silylatedwith hexamethyldisilazane and N,N-dibutylaminotrimethylsilane had almostidentical substituent distributions. Lower reaction temperature resulted inhigher regioselectivity.     

Degrees of polymerization (DP) and DP distribution of cellouronic acids prepared from alkali-treated celluloses and ball-milled native celluloses by TEMPO-mediated oxidation

Various cellulose II samples, ball-milled native celluloses and ball-milled wood saw dust were subjected to 2,2,6,6-tetramethypyperidine-1-oxyl radical (TEMPO)-mediated oxidation to prepare cellouronic acid Na salts (CUAs). The TEMPO-oxidized products obtained were analyzed by ¹³C-NMR and size-exclusion chromatography (SEC). When the cellulose II samples with degrees of polymerization (DP) of 220–680 were used as the starting materials, the CUAs obtained had weight-average DP (DPw) values of only 38–79. Thus, significant depolymerization occurs on cellulose chains during the TEMPO-mediated oxidation. These DP values of CUAs correspond to the cellulose II crystal sizes along the chain direction in the original cellulose II samples, but not necessarily to their leveling-off DP values. CUAs can be obtained also from ball-milled native celluloses in good yields by TEMPO-mediated oxidation, although their DPw values are lower than about 80. On the other hand, CUA with DPw of about 170 was obtained from ball-milled wood saw dust.     

Validation of a robust and rapid liquid chromatography tandem mass spectrometric method for the quantitative analysis of navitoclax

The Bcl-2 family small molecule inhibitor navitoclax is being clinically evaluated to treat multiple cancers including lymphoid malignancies and small cell lung cancer. A sensitive and reliable method was developed to quantitate navitoclax in human plasma using liquid chromatography with tandem mass spectrometry with which to perform detailed pharmacokinetic studies. Sample preparation involved protein precipitation using acetonitrile. Separation of navitoclax and the internal standard, navitoclax-d8, was achieved with a Waters Acquity UPLC BEH C₁₈ column using isocratic flow over a 3 min total analytical run time. A SCIEX 4500 triple quadrupole mass spectrometer operated in positive electrospray ionization mode was used for the detection of navitoclax. The assay range was 5–5,000 ng/ml and proved to be accurate (89.5–104.9%) and precise (CV ≤ 11%). Long-term frozen plasma stability for navitoclax at −70°C was at least 43 months. The method was applied for the measurement of total plasma concentration of navitoclax in a patient receiving a 250 mg daily oral dose.     

Rapid screening of polysaccharide-based plasma volume expanders dextran and hydroxyethyl starch in human urine by liquid chromatography-tandem mass spectrometry

The increasing number of samples and target substances in doping control requires continuously improved screening methods, combining high-throughput analysis, simplified sample preparation, robustness and reliability. Hence, a rapid screening procedure based on liquid chromatography-electrospray ionization-tandem mass spectrometry with in-source collision-induced dissociation was developed. The detection of the polysaccharide-based plasma volume expanders dextran and hydroxyethyl starch (HES) in human urine was established without further sample preparation. The in-source fragmentation strategy of the approach represented a valuable tool in the analysis of the polysaccharide-based compounds, allowing the use of tandem mass spectrometry. After direct injection of urine specimens, analytes were chromatographically separated on a monolithic reverse-phase column and detected via multiple reaction monitoring of diagnostic ions at detection limits of 10 microg/mL for HES and 30 microg/mL for dextran. Validation was performed regarding the parameters specificity, linearity, precision (8-18%) and accuracy (77-105%) and the method was applied to the investigation of approximately 400 doping control samples and seven dextran and two hydroxyethyl starch post-administration samples. The approach demonstrated its capability as a rapid screening tool for the detection of dextran and hydroxyethyl starch and represents an alternative to existing screening procedures since time consuming hydrolysis or derivatization steps were omitted.     

Charge and substituent effects on the stability of porphyrin/G‐quadruplex adducts

The adduct ions of two tetramolecular G‐quadruplexes formed from the d(TGGGGT) and d(TTGGGGGT) single strands with a group of cationic porphyrins, with different charges and substituents, and one neutral porphyrin, were investigated by ESI‐MS and ESI‐MS/MS in the negative ion mode. Formation of [Q + nNH₄⁺+P^p+‐(z + n + p)H⁺]^z‐ adduct ions (where Q = quadruplex, n = number of quartets minus 1, P = porphyrin and p⁺ =0,1,2,3,4) indicates that the porphyrins are bound outside the quadruplexes providing an additional stabilization to those structures. The fragmentation pathways of the [Q + nNH₄⁺+P^p+‐(z + n + p)H⁺]^z‐ adduct ions depend on the number of positive charges (p⁺) of the porphyrins and on the overall complex charge (z^‐), but do not show a significant dependence on the type of the substituent groups in the porphyrins. Formation of the ‘unfilled’ ions [Q + P^p+‐(z + p)H⁺]^z‐ predominates for porphyrins with a higher number of positive charges. Strand separation with the formation of [T + P^p+‐(z‐2 + p)H⁺]^(z‐2)‐ and (SS‐2H⁺)^2‐ ions, where T = [d(TG₄T)]₃ and [d(T₂G₅T)]₃ and SS = d(TG₄T) and d(T₂G₅T) is only observed for the complexes with a higher overall negative charge. Porphyrin loss with the formation of [Q + nNH₄⁺‐(z + n)H⁺]^z‐ ions occurs predominantly for the neutral and monocharged porphyrins. The predominant formation of the ‘unfilled’ ions, [Q + P^p+‐(z + n)H⁺]^z‐, for porphyrins with a higher number of charges shows that these porphyrins can prevent strand separation and preserve, at least partially, the quadruplex structure. Copyright © 2012 John Wiley & Sons, Ltd.     

Protective effects on ovalbumin-induced mouse asthma models and qualitative and quantitative analysis of multiple compounds in Gerberae Piloselloidis Herba

Gerberae Piloselloidis Herba is widely used to treat cough and asthma in China. However, its effects on allergic asthma as related to its chemical compositions have not been fully elucidated, and there is a scarcity of methods to determine multi-component contents for quality control. In this study, protective effects of Gerberae Piloselloidis Herba on ovalbumin-induced asthma models were investigated, while qualitative and quantitative analyses of multiple constituents in Gerberae Piloselloidis Herba were conducted by using an ultrahigh-performance liquid chromatography–Q Exactive hybrid quadrupole-orbitrap high-resolution accurate mass spectrometry and an ultrahigh-performance liquid chromatography–photodiode array detection. The results showed that Gerberae Piloselloidis Herba could significantly mitigate asthma symptoms, reduce eosinophils counts in the bronchoalveolar lavage fluid, as well as decrease IgE, IL-5, and IL-13 concentration, and inflammatory cellular infiltration in lung tissues. A total of 51 compounds were tentatively identified, in which the content of 10 representative compounds was determined in 24 batches of Gerberae Piloselloidis Herba by using an ultrahigh-performance liquid chromatography method with good linearity, precision, repeatability, accuracy, and stability. This research presents a comprehensive strategy combining biological activity evaluation with chemical profiling, providing a useful and comprehensive reference for further application and quality control of Gerberae Piloselloidis Herba.     

Classification of the distribution of trace impurities by spark source mass spectrometry analysis

Spark source mass spectrometry in combination with principal component analysis and clustering analysis was used to investigate the trace element distributions in metallic samples. The analysis of Zn and Cu samples and a comparison with direct imaging secondary ion microscopy demonstrated the consistency of the approach.On leave from Department of Chemistry, Nanjing Normal University, Nanjing, People's Republic of China.     

Secondary ion and laser ablation mass spectrometry for the quantitative characterization of styrene-butadiene copolymers

Styrene-butadiene copolymers were analyzed by static secondary ion mass spectrometry (S-SIMS) and laser ablation Fourier transform ion cyclotron resonance mass spectrometry (LA-FTICRMS) to obtain quantitative information based on specific ions. Silver deposition was performed on polystyrene, butadiene rubber and styrene-butadiene rubber. Under these experimental conditions, new secondary ions were detected, in particular silver-cationized butadiene [M(butadiene) - Ag](+) and styrene [M(styrene) - Ag](+) monomers. In contrast, LA-FTICRMS experiments did not require pretreatment. At high laser power density, UV photons (193, 266 and 355 nm) allowed the detection of styrene and butadiene monomers at m/z 104 and 54, respectively. The use of the observed ions by SIMS or LA-FTICRMS ensures that quantitative information on the relative distribution of each monomer is obtained. However, the silver coating thickness in the SIMS experiment seems to have an important influence on the quantitative information obtained. For LA-FTICRMS experiments, the best results are obtained at a wavelength of 355 nm.     

全二维气相色谱-飞行时间质谱对催化裂化汽油的定性与定量分析

采用全二维气相色谱-飞行时间质谱(GC×GC-TOF MS)对催化裂化汽油全馏分进行了定性与定量分析,建立了相应的分析方法.结果表明,汽油族组成中的烷烃、烯烃、环烷烃、芳烃在全二维点阵谱图中呈分区域、带状的分布特点.GC×GC-TOF MS根据催化裂化汽油组分内分子的沸点及极性差异对其进行两个维度分离,极大地避免了普通色谱法分析过程中沸点相似化合物共流的弊端,实现催化裂化汽油组分的精确分离和准确定性分析.通过引入响应因子,修正了不同性质的烃类在电离源上电离效率的差异,使得TOF对催化裂化汽油族组成的定量结果与普通气相色谱法的定量结果的相关性较好,且应用GC×GC-TOF MS方法获得了催化裂化汽油更为精确的族组成信息.GC×GC-TOF MS为催化裂化汽油精确表征提供了一种有效方法.     

Simultaneous quantitative analysis of polyphenolic compounds in human plasma by liquid chromatography tandem mass spectrometry

A diet rich in polyphenolic compounds has recognized health benefits, and as such is routinely monitored as part of dietary intervention studies. A method for the simultaneous determination of 36 phenolic compounds, including phenolic acids and flavonoids, using liquid chromatography and tandem mass spectrometry is described here. The target analytes were quantified based on their specific mass spectral fragments using a selected reaction monitoring approach. A C18 column with embedded aromatic functionality ensured separation of all phenolic compounds studied which included several pairs of isomers. Sample preparation involved the use of β‐glucuronidase to release the phenolic compounds from their conjugated forms. The intra‐day and inter‐day precision and accuracy was less than 7% for all phenolic compounds studied. Recoveries, where plasma was spiked with three different concentrations of the analytes, ranged from 95–115%. The limits of detection and quantification were 0.23–3.89 and 1.15–7.79 nM, respectively. The method was successfully applied to real samples and the range reported for each phenolic compound, with the exception of hydroferulic acid, nordihydroguaiaretic acid, methylgallate, and m‐coumaric acid, was at least an order of magnitude higher than the limit of quantification for the method.     

The Applicability of Enzymes in Cellulose Ether Analysis

Summary: Six methyl cellulose (MC) samples, one with a DS of 1.32 and five with a DS between 1.83 and 1.88, were degraded with five different enzymes or enzyme preparations containing endoglucanases. The main goal was to investigate whether enzymes could be used for determination of heterogeneity of the substituent distribution along the cellulose chain. To obtain information about the heterogeneity it was necessary to gather information on how the enzymes affect hydrolysis. Monomer composition and methyl distribution in the polymer chain were analyzed after total or partial random hydrolysis and appropriate derivatization by GC and MS, respectively, and used as reference data for the evaluation of the enzymatic hydrolysis. Size exclusion chromatography with multi angle light scattering and refractive index detection (SEC-MALLS/RI) was used to estimate molar mass distribution of the MCs before and after hydrolysis. Electrospray and matrix assisted laser desorption/ionization (ESI and MALDI) in combination with various MS analyzers were compared with respect to quantification of the degradation products directly and after perdeuteromethylation. Methyl group distribution in the oligomeric fractions and the average DS/DP were calculated from ESI mass spectra. With help of the reference analysis, patterns could be corrected for the unspecific contribution of end groups. By labelling and ESI-MSⁿ, our knowledge about the tolerance of the enzyme's sub-sites with respect to the number of methyl groups could be improved. A novel standard addition method in combination with electrospray ionization ion trap mass spectrometry (ESI-IT MS) was used to determine the amount of formed oligomers.     

羟乙基淀粉的羟乙基取代位置的研究

将羟乙基淀粉进行甲基化-水解-还原乙酰化反应，产生羟乙基葡萄糖的部分甲基化糖醇乙酸酯衍生物，应用气相色谱/化学电离质谱（GC/CIMS）和气相色谱/电子轰击质谱/质谱（GC/EIMS/MS）联用技术研究了羟乙基在淀粉糖环上的取代位置，发现G-2位取代的量是总取代量的82.0％。     

Multi-ion quantitative mass spectrometry by orthogonal projection method with periodic signal of electrostatic ion beam trap

In this article, orthogonal projection method (OPM) is introduced which could perform multi-ion quantitative MS with signal of electrostatic ion beam trap (EIBT), and its application has been demonstrated by numerical modeling. To acquire periodic current signal, a model of EIBT with cylindrical-detector is set up to simulate ions' oscillatory motion. Whereafter, OPM is introduced and applied for quantitative MS with sampling time being as short as 200 μs. Comparing with fast Fourier transform (FFT), the MS acquired by OPM is characterized by a more readable spectrum, a much shortened sampling time and the ability to do quantitative analysis. Within the optimum sampling time range, quantitative MS could be performed with accuracy of over 90%. It is found that the lower limit and the upper limit of the optimum sampling time range are all proportional to M(3/2)/δM and its relation is specified by linear regression. Aided by the results of FFT, OPM is applied to a compound tested signal induced by three kinds of ions. It shows that OPM could be performed respectively to each kind of ions without interference from other component of the signal. The resolving power acquired by OPM is about 75 000 with sampling time as short as 10 ms, and the quantitative result that acquired is quite accurate.     

X射线荧光光谱定量分析中超轻元素的处理方法

探讨了X射线荧光光谱定量分析中超轻元素的处理方法。在用deJongh-Norrish方程进行定量分析时,对通常不能用X射线荧光光谱直接测定的超轻元素作为消去组分处理以计算理论α系数,然后再以100%减去测量组分和已知组分浓度总和的方法来获得较为准确的分析结果。用此法分析了铌酸钾锂晶体中的Li~2O和两种含硼玻璃中的B~2O~3,分别得到了与等离子体发射光谱法和化学滴定法相符的结果,其中B~2O~3的结果优于文献报道的散射系数法和直接测定法的结果。     

A rapid ultra-performance liquid chromatography-electrospray ionization tandem mass spectrometric method for the qualitative and quantitative analysis of the constituents of the flower of Trollius ledibouri Reichb

A rapid ultra-performance liquid chromatography-electrospray ionization tandem mass spectrometric (UPLC–ESI-MS/MS) method was developed for the qualitative and quantitative determination of the constituents of the flower of Trollius ledibouri Reichb. The analysis was performed on an AcQuity UPLC™ BEH C₁₈ column using gradient elution with a mobile phase of 0.1% acetic acid and acetonitrile over 20 min. A tandem quadrupole spectrometer operating in either full scan mode or in MS/MS mode for multiple reaction monitoring (MRM) was used for the qualitative and quantitative analysis of the constituents, respectively. According to the mass spectrometric fragmentation mechanism and UPLC–ESI-MS/MS data, the chemical structures of 15 constituents of the flower of T. ledibouri Reichb. were identified on-line without time-consuming isolation and four of them, 2″-O-β-l-galactopyranosylorientin, 2″-O-β-arabinopyranosylorientin, orientin and vitexin, were quantified. The limits of quantification of these four flavonoids were 540, 321, 515 and 220 μg g⁻¹ plant material, respectively. Four commercial samples from different sources were analyzed. The UPLC–ESI-MS/MS method for analyzing the constituents can be used to evaluate the quality of the flower of T. ledibouri Reichb.     

Readily hydrolysable cellulose esters as intermediates for the regioselective derivatization of cellulose; II. Soluble,highly substituted cellulose trifluoroacetates

Cellulose trifluoroacetate (CTFA) with DS values of 1.5 and 2.1 and DP values ranging from 170 to 800 have been prepared free from impurities of the reaction mixture (weakly bound trifluoroacetic acid) and of the procedure of isolation (diethyl ether). The CTFAs are soluble in DMSO, DMF, pyridine, and THF and thermostable up to 250 °C. A convenient synthetic method for CTFAs with DS 1.5 involves the acylation of cellulose with mixtures of trifluoroacetic acid (TFA) and trifluoroacetic anhydride (TFAA, 33% v/v) at room temperature for 4 h and subsequent treatment of the crude polymer at 150 °C and 80 Pa for 40 min. The preparation of CTFAs with DS-values up to 2.1 requires the addition of chloroform and 16 h reaction time.¹³ C-NMR studies as well as HPLC analyses after methylation and chain degradation show a preferred trifluoroacetylation of the primary hydroxy groups of the cellulose. The extent of depolymerization during the trifluoroacetylation was investigated for various cellulose materials. The cleavage of the trifluoroacetyl groups is possible by treating the derivative with a protic medium like water. Total hydrolysis of CTFA dissolved in DMF with water (room temperature) takes 6 min. The first paper on this topic was concerned with cellulose formates (Schnabelrauchet al., 1992).     

Quantification of enantiomers by mass spectrometry based on chemical derivatization and spectral shape deformation quantitative theory

A facile mass spectrometric kinetic method for quantitative analysis of chiral compounds was developed by integrating mass spectrometry based on chemical derivatization and the spectral shape deformation quantitative theory. Chemical derivatization was employed to introduce diastereomeric environments to the chiral compounds of interest, resulting in different abundance distribution patterns of fragment ions of the derivatization products of enantiomers in mass spectrometry. The quantitative information of the chiral compounds of interest was extracted from complex mass spectral data by an advanced calibration model derived based on the spectral shape deformation quantitative theory. The performance of the proposed method was tested on the quantitative analysis of R‐propranolol in propranolol tablets. Experimental results demonstrated that it could achieve accurate and precise concentration ratio predictions for R‐propranolol with an average relative predictive error (ARPE) of about 4%, considerably better than the corresponding results of the mass spectrometric method based on chemical derivatization and the univariate ratiometric model (ARPE: about 12%). The limit of detection (LOD) and limit of quantification (LOQ) of the proposed method for the concentration ratio of R‐propranolol were estimated to be 1.5% and 6.0%, respectively. The proposed method is complementary to the existing methods designed for the quantification of enantiomers such as the Cooks kinetic method.