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Rationale: Synthesis of copolymer is one of the major approaches to establish sophisticated polymers. In copolymer analysis in mass spectrometry (MS), an increase in the number of monomer unit species and/or the polymer molecular weight results in complex mass spectra, and a method is required to solve this problem. Methods: In this study, electrospray ionization‐ion mobility spectrometry‐mass spectrometry was employed to analyze styrene/methyl methacrylate/n‐butyl acrylate (St/MMA/nBA) terpolymers via Kendrick mass defect (KMD) analysis. An expanded Fourier transform‐based noise reduction method for the copolymer was developed to improve the decrease in the signal/noise ratio observed in the higher m/z region. Results: Low‐mass terpolymers (0.7 kDa) were identified by comparing the observed and theoretical results using a two‐dimensional KMD plot. For the 1.5 kDa terpolymer, the signal overlap, of which KMD value was not matched with the theoretical one, was interpreted by the shift from the theoretical value in the KMD plot. For the 3.0 kDa terpolymers, the compositional candidates were determined by the prediction based on the compositional information of low‐mass terpolymers previously analyzed. The 4.5 kDa terpolymer was interpreted after the expanded noise filtering. Conclusions: The terpolymers, whose molecular weight was up to 4.5 kDa, were successfully characterized at a molecular level. The dependency of the St/MMA/nBA composition on molecular weight was observed; that is, the nBA content decreased with an increase in the molecular weight. [ABSTRACT FROM AUTHOR]

Rationale: Analyzing polymer end groups using pyrolysis (Py) gas chromatography/mass spectrometry (GC/MS) in multi‐component polymer samples is not an easy task because of the insufficient sensitivity, selectivity, and mass resolution of conventional Py‐GC/MS systems. Methods: A new Py‐GC/MS system using an atmospheric pressure chemical ionization (APCI) source combined with high‐resolution time‐of‐flight mass spectrometry (TOFMS) was used for end‐group analysis of a methyl methacrylate (MMA)‐styrene (St)‐butyl acrylate (BA) terpolymer (P (MMA‐St‐BA)), which was radically polymerized using 2,2′‐azobis(2‐methylbutyronitrile) (AMBN) as an initiator. Results: Five possible pyrolyzates, comprising an AMBN fragment and a monomer unit, formed during the initiation reactions from one of the three types of end groups, were selectively detected and exclusively identified in their respective extracted ion chromatograms for molecule‐related ions, such as M+ and [M + H]+, with a narrow mass window of ±2 milli m/z units. Conclusions: It was demonstrated that Py‐APCI‐TOFMS is a powerful technique to characterize in detail the complex end groups in multi‐component polymer samples, because of the soft ionization nature of APCI and the high mass resolution of TOFMS. [ABSTRACT FROM AUTHOR]

Increasing the J-factor for atomized flow is expected to reduce porosity in high-pressure die casting (HPDC) products. Casting experiments were conducted to confirm changes in the amount of porosity in two parts of a piston and a wheel with increasing J-factor. As a result, the amount of porosity was reduced in the piston, but increased in the wheel under high J-factor conditions. To clarify the mechanism, a multiphase flow analysis system was developed to calculate turbulent flow using large eddy simulation. The developed system visualizes the state of small voids and vortex structures in molten metal during HPDC. In the piston, the formation of vortex tubes from the thick parts to the overflow promoted void discharge and reduced the number of voids in the thick parts. In the wheel, voids formed by the vortices in the hub part were transferred to the rim part, which is the final filling area, resulting in an increase in voids. From these results, it was possible to clarify the process from the generation to discharge of voids in molten metal flow by analyzing the microscopic state of atomized flow in the die cavity. [ABSTRACT FROM AUTHOR]

Recently, we have developed ultralow-temperature high-performance liquid chromatography (HPLC) at −196 °C using liquid nitrogen-based mobile phases. In this study, a retention model for ultralow-temperature HPLC, in which adsorption exchange and “pseudo partition” modes are combined, is proposed to describe the effect of the mobile phase composition on the retention of analytes. The experimental results agreed well with the equation of the proposed model. It was revealed that, in the low and high additive concentration regions, adsorption exchange and pseudo partition retention, respectively, dominate the analyte retention. The difference in the retention behavior between bare-silica and octadecylsilyl-modified silica (ODS) columns was also studied. Retention of alkanes in the ODS column was greater than that in the bare-silica one. Addition of both ethane and ethylene to the mobile phase in the ODS column afforded the elution of propylene, which was not eluted with the bare-silica column at −196 °C. [ABSTRACT FROM AUTHOR]

A method for separating water-insoluble and neutral synthetic polymers using non-aqueous capillary zone electrophoresis (NACZE) was developed. The non-aqueous solvent system comprising a mixture of tetrahydrofuran, acetonitrile, and ethanol containing cetyltrimethylammonium chloride was used for solubilizing and conferring positive charges to the polymers. A mixture of polystyrene (PS, M n = 6500) and polybutadiene (PBD, M n = 5900) was successfully separated by the NACZE method using cationic surfactants. Evaluation of the effect of the molecular weight of the polymers on the electrophoretic behavior demonstrated that PSs with different molecular weights ( M n = 6500, 10,200, 19,600, 200,000) were co-eluted as a single peak. That is, the apparent electrophoretic mobility of the PSs was independent of the molecular weight. In contrast, evaluation of PBD and polycarbonate (PC) demonstrated that the solubility of polymers in the medium affected the apparent electrophoretic mobility of the polymers, where low solubility resulted in reduced apparent electrophoretic mobility. Using the proposed method, poly(styrene- co -methylmethacrylate)s with different compositions were successfully separated. [ABSTRACT FROM AUTHOR]

Significant peak width reductions, or peak height enhancements, of angiotensins were observed when a high voltage was applied to hydrophilic interaction pressurized capillary electrochromatography using gradient elution with mobile phases containing perchloric acid. The investigation using a contactless conductivity detector revealed that perchloric acid was adsorbed on the surface of the stationary phase, when the acetonitrile content in the mobile phase was high, and released from the stationary phase by increasing the water content during a gradient procedure. The released perchloric acid formed a highly concentrated zone moving from the column inlet to the outlet. The electrochromatographic behavior of the analytes, primarily electrophoretic migration, was changed in this zone. As a consequence of the significant variation in migration velocity of the analytes, the sample band width was reduced similar fashion to on-capillary concentration in capillary electrophoresis. Using this result, the reduction of band width and enhancement in separation efficiency was demonstrated in reversed-phase pressurized electrochromatography, in which the conductivity of the mobile phase was significantly altered using a step gradient. The resolution between benzoic acid and 1-naphthalene sulfonic acid was successfully improved from 2.7 to 4.3 by using the band width reduction method based on field-amplified stacking. [ABSTRACT FROM AUTHOR]

A method for evaluating the interactions between metal ions and nonionic surfactants in aqueous solutions containing high-concentration HCl, using gas pressure-driven low-pressure high-performance liquid chromatography (LP-HPLC) as a highly acid-resistant HPLC system, was developed. To construct the LP-HPLC for this purpose, poly(styrene- co-divinylbenzene)-based low-flow-resistance monolithic columns tolerant to highly acidic conditions were prepared using low-conversion thermal polymerization. Thermal polymerization at 65 °C for 1.5 h (monomer conversions, 33 % for styrene and 59 % for divinylbenzene) allowed preparation of a column with both high separation efficiency (around 60,000 plates m for alkylbenzenes) and a quite low back pressure of 0.14 MPa at a linear flow rate of 1 mm s (2.8 × 10 m in permeability). The base column prepared under the above conditions was coated with a nonionic surfactant, polyoxyethylene nonylphenyl ether (PONPE, average oxyethylene unit numbers ( n) = 3, 7.5, 15, and 20), and used for evaluation of the interactions between PONPEs and metal ions in 6 M HCl. The interactions between PONPEs and Au(III), Ga(III), Fe(III), Zn(II), and Cu(II) were successfully evaluated using both breakthrough and chromatographic methods. Furthermore, a study of the effect of the polyoxyethylene (POE) chain length revealed that the use of PONPE with the longer POE moiety enhanced the magnitude of the interaction together with the increase in the amount of oxyethylene (OE) units coated on the monolith. Moreover, the interactions of metal ions with a single OE unit were almost constant in the range of n = 7.5-20, whereas the suppression of the interaction between Au(III) with the shortest PONPE chain ( n = 3) was also observed. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

A method of simultaneous separation of water- and fat-soluble vitamins using pressure-assisted CEC with a methacrylate-based capillary monolithic column was developed. In the proposed method, water-soluble vitamins were mainly separated electrophoretically, while fat soluble-ones were separated chromatographically by the interaction with a methacrylate-based monolith. A mixture of six water-soluble and four fat-soluble vitamins was separated simultaneously within 20 min with an isocratic elution using 1 M formic acid (pH 1.9)/acetonitrile (30:70, v/v) containing 10 mM ammonium formate as a mobile phase. When the method was applied to a commercial multivitamin tablet and a spiked one, the vitamins were successfully analyzed, and no influence of the matrix contained in the tablet was observed. [ABSTRACT FROM AUTHOR]

Voltage-induced impedance variation of the minicolumn (i.d. 0.53 mm, length 2 mm) packed with cation exchanger was investigated to develop a sensing method. An aqueous sample solution containing the metal cations was continuously supplied to the minicolumn during the impedance measurement with the simultaneous application of both alternating current voltage (amplitude, 1.0 V; frequency, 200 kHz to 6 Hz) and direct current (DC) offset voltage (0.1 to 1.0 V). On a complex plane plot, the profile of the column impedance consisted of a semicircle (200 kHz to 100 Hz) and a straight line (<100 Hz), of which slope varied with the magnitude of the applied DC offset voltage ( VDC). The slope– VDC relation depended on the kind of the metal cation and its concentration; in particular, the slope– VDC relations of monovalent cations (Na+ and K+) and divalent ones (Mg2+ and Ca2+) were significantly different. With the change in the concentration of minor divalent salt of MgCl2 or CaCl2 (60 to 140 μM) in the sample solution containing 10 mM NaCl, the slopes showed almost linear relationships between those with application of VDC = 0.1 V and 1.0 V both for magnesium and calcium additions. In the case of plural addition of both MgCl2 and CaCl2 to the solution, the data points in the slope0.1 V–slope1.0 V plot were located between the two proportional lines for single additions of magnesium and calcium, reflecting both the mixing ratio and net concentrations of the divalent cations. Thus, simulations determination of Mg2+ and Ca2+ can be attained on the basis of the slope0.1 V–slope1.0 V relation obtained by the impedance measurements of the minicolumn. Actually, the contents of both magnesium and calcium cations in the bottled mineral waters determined simultaneously using the proposed method were almost equivalent to those obtained by the atomic absorption spectrometric measurement. [ABSTRACT FROM AUTHOR]

Abstract: Three types of thiol compounds (n-octadecanethiol, thiophenol, and 2-phenylethanethiol) were used to modify the gold-coated polystyrene particles (dp. 5μm) to prepare a stationary phase for capillary liquid chromatography through the formation of self-assembled monolayer. The column with n-octadecanethiol-modified gold-coated polystyrene particles (C18-Au) demonstrated the higher affinity to phenanthrene and anthracene than small aromatics compared to the ODS column. In addition, the shape selectivity between phenanthrene and anthracene in the C18-Au column was much higher than that in the ODS column (separation factors: 1.82 and 1.14, respectively). The relationship between the retention factor and acetonitrile content in the mobile phase revealed that the retention behaviors in the C18-Au column was more sensitive on the acetonitrile content than those in the ODS column. Relatively higher affinity for phenanthrene and anthracene was commonly observed in all the three thiol-modified Au columns than that for the conventional ODS column, whereas separations of benzene and nitro- and chlorobenzenes were quite different among the three thiol-modified Au and ODS columns. [Copyright &y& Elsevier]

Abstract: The dual gradient column, in which both the chemical property of the stationary phase and the flow velocity in the mobile phase are heterogeneous longitudinally along the column, is developed to obtain the mobile phase gradient-like elution in an isocratic condition. Here, the step-wise dual gradient columns were prepared by connecting an inlet column (I.D. 50μm, packed with ODS) serially to an outlet column (I.D. 100–200μm, packed with the mixture of ODS and C1 [9:1]). The retention behavior of alkylbenzenes was able to be controlled in the dual gradient column depending on the variation in the flow velocity. Moreover, the change in retention behavior induced by the flow velocity variation for the dual gradient columns was quite different from that by the variation in organic modifier content of the mobile phase in isocratic elution for a single gradient column and can induce the similar effect with an ordinary gradient elution in a mobile phase composition. [Copyright &y& Elsevier]

A pressurized gradient capillary electrochromatograph using a splitter was constructed. The variation in flow rate during gradient elution was investigated and separations of peptides using an Amide stationary phase were demonstrated. The flow rate, which is one of the important factors to control chromatographic behavior, was increased during the gradient elution, and the mismatching of mobile phase between the column and the resistance tubing derived three variation patterns in the flow rate. The electrophoretic migration in electrochromatography could enhance in separation of peptides. The separated peak number of tryptic digest of bovine serum albumin was increased from 30 to 40 by the application of +5 kV. [Copyright &y& Elsevier]

The behavior of neutral sample solutes in pressurized flow driven electrochromatography using a mixed stationary phase, which consisted of ODS and anion-exchange (ODS–SAX), was studied. Applications of both positive and negative voltage on a column induced increases in retention factors of sample solutes. The direction of an electroosmotic flow under applications of positive and negative voltage were the same, therefore, the sign of the surface charge density under positive and negative voltage was opposite. We proposed a new equation for the relationship between applied voltage and surface charge density, and the practical electroosmotic flow conformed to this equation. Studying the electroosmotic flow using our proposed equation revealed that the applied negative voltage accelerates the protonation of the quaternary ammonium group and dissociation of the silanol group on packing materials. The retention behavior of a neutral solute was affected by the existence of the charged functional groups. We propose that this phenomenon is applicable to the control of the retention behavior of a sample solute using an electric field. [Copyright &y& Elsevier]

• Py-GC-APCI-TOFMS was used to identify five polymer species in a mixed sample. • Polyethylene and polypropylene species were distinguished in the polymer mixture. • Unique fragmentation/ionization of APCI enables discrimination of similar species. • High mass resolution of TOFMS allows accurate identification of individual species. • Py-GC-APCI-TOFMS is a promising tool to characterize environmental microplastics. Pyrolysis-gas chromatography coupled with atmospheric pressure chemical ionization-high resolution time-of-flight mass spectrometry (Py-GC-APCI-TOFMS) was applied for the reliable identification of polymer species in a complex mixture to establish this system as a platform for environmental microplastic analysis. The method was evaluated on a model sample of mixed microplastics comprised of five major polymers: polyethylene (PE), polypropylene (PP), poly(vinyl chloride) (PVC), polystyrene (PSt), and poly(ethylene terephthalate) (PET). The representative ions in the mass spectra of the pyrolyzates were identified by Py-GC-APCI-TOFMS measurements of the individual polymer species. The unique APCI ionization/fragmentation process and the high mass resolution of TOFMS were exploited to confirm the presence of the respective polymer species in the extracted ion chromatograms (EICs) of the mixed sample for the selected key ions. PE and PP were successfully and uniquely identified in the mixed sample by focusing on specific fragment ions of the pyrolyzates formed during APCI (m/z 114.093 ± 0.020 and m/z 156.139 ± 0.020, respectively). The resultant EICs allowed for the specific analysis of these species, even in the presence of interfering species produced from the other polymers. Similar processes were applied to the detection of PVC, PSt, and PET in the mixed sample. These results demonstrated that Py-GC-APCI-TOFMS is a promising tool to characterize a complex mixture of environmental microplastics. [ABSTRACT FROM AUTHOR]

Rationale: We recently developed the characterization method for synthetic polymers weighing more than a few tens of kilodalton using electrospray ionization‐ion mobility spectrometry‐tandem mass spectrometry, in which the m/z value of the most abundant peak was used for characterization. However, the identification of the most abundant peak from the isotopic peaks was often difficult due to the background noise. Methods: Here, we employed a noise reduction method using Fourier transform (FT) filtering. In the power spectrum obtained using FT of the mass spectrum of the multiple charged analytes, the significant signals in the low‐frequency region and at frequency z are observed for the analytes of z charges. When the signals in both regions were used for inversed FT (i.e., the signals in other regions were zero padded), a noise‐filtered mass spectrum was obtained. Results: In the analysis of poly(methylmethacrylate)s weighing 13–17 kDa, mass spectra without noise filtering with relatively high‐intensity noise (than signal) were complicated to identify the most abundant peak. On the contrary, the most abundant peak was clearly identified from the mass spectra after FT‐based noise filtering, and end group composition was estimated successfully. Conclusions: The proposed FT‐based noise filtering for the mass spectrum is effective to characterize multiply charged synthetic polymers weighing more than a few tens of kilodalton using electrospray ionization‐ion mobility spectrometry‐tandem mass spectrometry. [ABSTRACT FROM AUTHOR]

The original article can be found online at https://doi.org/10.1007/s40962-023-01015-8. Publisher's Note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. [Extracted from the article]

Polymers with large molecular weight are difficult to interpret using electrospray ionization-mass spectrometry (ESI-MS) due to the generation of various highly multiply charged analytes. Although ESI-ion mobility spectrometry (IMS)-MS is effective in reducing the complexity of the mass spectrum, this approach is insufficient for analyzing highly multiply charged polymers. In this study, we propose a method combining tandem mass spectrometry (quadrupole and high-resolution time-of-flight MS, QMS/TOFMS), IMS, and collision-induced charge stripping (CICS) for analyzing large intact polymers (∼40 kDa), which are highly multiply charged. The number of charges can be estimated from a Fourier transform power spectrum of a mass spectrum when the charge number is less than approximately 20. Interpretations of the spectra of poly(ethylene oxide)s (PEOs) weighing 20 kDa, poly(methyl methacrylate)s weighing 22 kDa, and methoxy-PEO-maleimide weighing 40 kDa were successfully demonstrated with isotope level and polymerization degree level separations, respectively. In the proposed method, a mixture can be analyzed for relatively small (a few kDa) and large (a few tens of kDa) polymers simultaneously without any sample pretreatment. [ABSTRACT FROM AUTHOR]

Multiplex high-performance liquid chromatograph-mass spectrometry (HPLC-MS), in which multiple HPLCs and one MS are hyphenated, is an approach for high throughput analysis in HPLC-MS. A general multiplex HPLC-MS method employs a column-switching technology, and only one HPLC is connected to one MS at a time. In the present study, we propose a novel multiplex HPLC-MS system for simultaneous HPLC-MS analyses. In this study, multiple HPLCs are hyphenated with one MS without a column-switching mechanism, and a mixed-chromatogram is observed by the MS. Here, we employ a frequency division multiplexing (FDM) technique used in communication engineering to extract any chromatogram from the mixed-chromatogram. When a modulator (chopper or ion-gate type) is set between each ion source and the MS, each modulator blocks each sample stream with an individual frequency. In theory, each chromatogram can be extracted from the mixed-chromatogram via a signal processing based on a Fourier transform (FT), frequency-based signal extraction, and reversed FT. In the actual experiment, two HPLCs are hyphenated with one MS (2HPLC-1MS). The use of chopper type modulators leads to the extraction and restoration of each chromatogram from the mixed-chromatogram. However, each restored-chromatogram involves signal interference. On the other hand, the ion-gate modulation system successfully resulted in restored-chromatograms without interference. The potential of the novel multiplex HPLC-MS system based on FDM is confirmed with respect to the simultaneous and continuous analyses of plural samples. [ABSTRACT FROM AUTHOR]

Low-temperature high-performance liquid chromatography, in which a loop injector, column, and detection cell were refrigerated at -35ºC, using liquid carbon dioxide as the mobile phase was developed. Small organic compounds (polyaromatic hydrocarbons, alkylbenzenes, and quinones) were separated by low-temperature high-performance liquid chromatography at temperatures from -35 to -5ºC. The combination of liquid carbon dioxide mobile phase with an octadecyl-silica (C18) column provided reversed phase mode separation, and a bare silica-gel column resulted in normal phase mode separation. In both the cases, nonlinear behavior at approximately -15ºC was found in the relationship between the temperature and the retention factors of the analytes (van't Hoff plots). In contrast to general trends in high-performance liquid chromatography, the decrease in temperature enhanced the separation efficiency of both the columns. [ABSTRACT FROM AUTHOR]

A novel analytical pyrolysis device suitable for the measurements of the less volatile pyrolyzates was developed. This device is comprised of a pyrolysis unit based on the vertical microfurnace pyrolyzer and a movable pyrolysis tube made of stainless steel. The upper side of the pyrolysis tube is first set at the heated center of the pyrolysis unit. A polymer sample in a sample cup is introduced into the heated center and pyrolyzed under the flow of nitrogen carrier gas. The pyrolyzates are then transferred to the bottom side of the pyrolysis tube which is cooled down by air blow and the less volatile pyrolyzates are condensed. After that the pyrolysis tube is moved down out of the pyrolysis unit and blocked from the hot zone by moving the three port valve. Finally the trapped pyrolyzates are flushed by an appropriate solvent into a collection vial. The recovered pyrolyzates in the solution can be then subjected to the measurements suitable for less volatile products such as matrix-assisted laser desorption/ionization mass spectrometry. Moreover, this device is also on-line connected to the injection port of a high performance liquid chromatographic system, which is also appropriate for the measurements of oligomeric products. The basic performance of the developed device was tested by using some polymer samples forming less volatile pyrolyzates such as poly(butylene terephthalate) and poly(2,6-dimethyl-1,4-phenylene ether). In addition, the usefulness of this method was demonstrated through the characterization of the crosslinking sequences in a photocured resin combined with the thermally-assisted hydrolysis and methylation reaction. [ABSTRACT FROM AUTHOR]

Abstract: A methacrylate-based anion-exchange monolithic column was prepared by a single-step UV photo-copolymerization of [2-(methacryloyloxy)ethyl]-trimethyl ammonium chloride, butylmethacrylate, and ethylene dimethacrylate at a low temperature of −15°C. The anion-exchange column exhibited good separation efficiency for the small inorganic anions of NO2 −, Br−, NO3 −, and I− in the isocratic mode. Under the conditions optimized using a mobile phase of 50% ACN containing 100mM of NaCl, the theoretical plate heights of the anions were within the range of 12.2–15.6μm (N, 64,000–82,000m−1; k, 0.2–1.6); and a value of 9.4μm (N, 110,000m−1) was achieved for t 0. The flow resistance of the column was acceptably low with a permeability of 2.7×10−13 m2. Fast gradient elution at a flow rate of 32mm/s resulted in rapid and precise separation of the inorganic anions of IO3 −, NO2 −, Br−, NO3 −, and I− within 20s. [Copyright &y& Elsevier]

Abstract: A particulate formation-laser scattering detector (PFLSD) was developed and used for evaluating the crystallization efficiency of inorganic polyphosphates (PPs) that reacted with either magnesium or calcium cations. As the solutions for reactive crystallization, 0.5M ammonium buffer (pH 9.6) containing either 0.15M MgCl2 or 0.15M CaCl2 (MAP: magnesium ammonium phosphate and HAP: hydroxyapatite solution) were used. In the case of mono- and diphosphate (P1 and P2), the significant dependences of the particulate formation efficiency on various types of both P1/P2 and MAP/HAP reaction solutions were observed with the direct sample injection mode. The PFLSD was hyphenated with the anion-exchange chromatography and the dependence of the particulate formation efficiency on the polymerization degree (n p) of PP oligomers, separated chromatographically, was evaluated sequentially. The significant suppression of the particulate formation for PP oligomers was clearly confirmed, i.e., the MAP and HAP reaction solutions did not produce the particulates of the PP oligomers having an n p value of more than 3 and 5, respectively. As the overall tendency, the particulate formation efficiency in the case of the HAP solution was superior to that in the case of the MAP solution. [Copyright &y& Elsevier]

A phenomenon was found whereby the application of an alternating voltage to a capillary column can vary the capacity factor of a sample solute. The alternating voltage induced variation in the capacity factor was studied using an anion exchange mini-bed (a short capillary column 12 mm long). The capacity factor varied according to both the amplitude and frequency of an applied alternating voltage. The variation greatly depended on the kinds of sample solutes and packing materials. A new separation mode for capillary electrochromatography using an alternating voltage, that is, alternating voltage capillary electrochromatography (AV-CEC), was proposed as an application of this phenomenon to control the retention of a sample solute. The chromatographic behavior of three organic acids (benzoic acid, phthalic acid, and salicylic acid) was studied in AV-CEC using an anion exchange column. [ABSTRACT FROM AUTHOR]

The Kendrick mass defect (KMD) analysis of multiply charged polymeric distributions has recently revealed a surprising isotopic split in their KMD plots—namely a 1/z difference between KMDs of isotopes of an oligomer at charge state z. Relying on the KMD analysis of actual and simulated distributions of poly(ethylene oxide) (PEO), the isotopic split is mathematically accounted for and found to go with an isotopic misalignment in certain cases. It is demonstrated that the divisibility (resp. indivisibility) of the nominal mass of the repeating unit (R) by z is the condition for homolog ions to line up horizontally (resp. misaligned obliquely) in a KMD plot. Computing KMDs using a fractional base unit R/z eventually corrects the misalignments for the associated charge state while using the least common multiple of all the charge states as the divisor realigns all the points at once. The isotopic split itself can be removed by using either a new charge-dependent KMD plot compatible with any fractional base unit or the remainders of KM (RKM) recently developed for low-resolution data all found to be linked in a unified theory. These original applications of the fractional base units and the RKM plots are of importance theoretically to satisfy the basics of a mass defect analysis and practically for a correct data handling of single stage and tandem mass spectra of multiply charged homo- and copolymers.ᅟ [ABSTRACT FROM AUTHOR]

Both the separation behavior and the structure of a polymer monolith column depends on both the reaction solution composition and the polymerization conditions. In photoinitiated low-temperature polymerization, polymerization temperature, irradiation intensity, and polymerization time were key factors to control the monolith characteristics. In this study, the effect of polymerization time on the chromatographic, material, and chemical characteristics of poly(butyl methacrylate-co-ethylene dimethacrylate) monoliths was studied using pyrolysis-gas chromatography, Raman spectroscopy, inverse size exclusion chromatography, scanning electron microscopy, and chromatographic methods. Both butyl methacrylate and ethylene dimethacrylate monomers were incorporated into the monolith as the polymerization time increased, and it resulted in increases in both the flow resistance (decrease in both permeability and total/through pore porosities) and retention factors. The longer polymerization time led to lower relative amounts of free methacrylate functional groups in the monolith, i.e. cross-linking was enhanced. The increase of the polymerization time from 8 to 12 min significantly reduced the separation efficiency for the retained analyte, whereas an increase in the fraction of the mesoporosity was observed. [ABSTRACT FROM AUTHOR]

A new preparation method has been developed that uses silica-oligomer for the sub-micron silica-gel layer for the open-tubular capillary column (OTC). The silica-gel layer has a unique sub-micron cell structure, which was observed by scanning electron microscope, and this structure contributes to increasing its total surface area. Using ultrashort (2 cm long) OTCs modified with docosyl methyl dichloro silane, separation of neutral compounds has been demonstrated. The column shows a good performance, such as theoretical plate number 71,000 plates/m. The column gives a relatively high capacity factor, such as 1.85 for fluorine. [ABSTRACT FROM AUTHOR]