Laser Light-scattering Detector Research Articles

Molar mass determination via linear regression from SEC measurements: The case of polylactide, polycaprolactone and poly(2,2‐dimethylthrimethylene carbonate)

AbstractMolar mass correction coefficients (cc) were determined for calculating the absolute molar masses of polylactide (PLA), polycaprolactone (PCL), and poly(2,2‐dimethyltrimethylene carbonate) (PDTC) in the range of 2,5–190 kg/mol, using calibration based on polystyrene standards (PS). Linear PLAs, PCLs, and PDTCs with a wide range of molar masses were synthesized using tin (II) octoate and diol as a catalyst/initiator system. Size Exclusion Chromatography (SEC) coupled with a Refractive Index detector (SEC‐RI) or a Multi‐Angle Laser Light Scattering detector (SEC‐MALLS) was utilized to determine the relative molar mass or absolute molar mass of the samples under investigation. Additionally, for comparison, the absolute molar mass of low molar mass PLA, PCL, or PDTC was calculated based on end‐group analysis using the 1H NMR method. Correction coefficients were subsequently calculated by comparing the molar mass obtained from SEC‐MALLS and SEC‐RI. The calculated correction coefficients ranged from 0.40 to 0.87 and increased with the rising molar mass of the polymers. The derived equation could be used to evaluate the absolute molar masses from PS standards over a broad range for the analyzed polymers.

A branched structure provides kraft lignins a denser morphology and a high molar mass for a given hydrodynamic radius

AbstractSize exclusion chromatography with multi-angle laser light-scattering detectors was applied for acetylated softwood and hardwood kraft lignins (Ac-SKL and Ac-HKL) and 8-O-4′ type of linear polymeric lignin model (Ac-M-8O4′) to compare their swelling behaviors. The plot of molar mass (MM) vs. retention time for Ac-M-8O4′ was similar to that of polystyrene, which revealed that Ac-M-8O4′ exhibited swelling behavior that was similar to that of polystyrene. However, the MM values of both Ac-KLs were larger than those of polystyrene standards at any retention time. This difference indicated that both Ac-KLs had a more compact structure than those of polystyrene and Ac-M-8O4′. One hypothesis is that the larger MM of both Ac-KLs stems from their branched structures. To verify this hypothesis, the frequency of 5-5′ interunit linkage in lignin samples was determined by1H NMR after nitrobenzene oxidation. A linear relationship between MM and 5-5′ abundance was observed in the high MM region.

Characterization of sulfated polysaccharide from Laurencia obtusa and its apoptotic, gastroprotective and antioxidant activities

This study was designed to characterize the physico-chemical properties of the sulfated polysaccharide (SP) isolated from the red alga Laurencia obtusa and to evaluate its apoptotic, gastroprotective and antioxidant activities.The different macromolecular characteristics of SP were determined by size exclusion chromatography combined with multi-angle laser light-scattering detection (SEC-MALLS), Fourier transform infrared spectroscopy (FTIR) analysis and nuclear magnetic resonance spectroscopy (1H NMR and 13C NMR). The native molecular weight of the extracted polysaccharide is high (≥336,900 g·mol−1). It showed high amounts of sulfated groups (28.2%) and low levels of proteins. It was found to be a potent inducer of apoptosis on acute monocytic leukaemia THP-1cell lines with EC50 value of 53 μg·mL−1. Furthermore, a significant gastroprotective effect (p < 0.01) was also observed with a gastric ulcer inhibition of 63.44%, 78.42% and 82.15% at the doses 25, 50 and 100 mg·kg−1, respectively. In addition, SP significantly increased glutathione levels (GSH) and decreased the concentration of thiobarbituric acid-reactive substances (TBARS) in EtOH/HCl-damaged gastric mucosa in rats; it also exhibited an important antioxidant activity in vitro. Therefore, SP, derived from the red alga Laurencia obtusa, may have a potential therapeutic effect against acute myeloid leukaemia and a beneficial potential as gastroprotective and antioxidant natural product.

Determination of the absolute molar mass of acetylated eucalyptus kraft lignin by two types of size-exclusion chromatography combined with multi-angle laser light-scattering detectors

Abstract The molar mass (MM) and polydispersity indices (PDI) of acetylated hardwood kraft lignin (Ac-HWKL) and Ac-HWKL fractions were measured by size-exclusion chromatography with multi-angle laser light scattering (SEC-MALLS). The detectors worked at LL658 nm and LL785 nm. The MM of Ac-HWKL measured at 785 nm was much smaller than that measured at 658 nm. The number-average (Mn) and weight-average (Mw) molar masses of Ac-HWKL determined at 785 nm were approximately 6.2 and 6.5 times larger, respectively, than the values estimated using a conventional calibration curve created with authentic polystyrene standards in tetrahydrofuran (THF). Based on the Mw of Ac-HWKL fractions, the Mark-Houwink-Sakurada equation for Ac-HWKL was established to be [η]/ml g−1=0.320 M0.24 in THF and [η]/ml g−1=0.142 M0.26 in dimethyl sulfoxide (DMSO). These results demonstrate that Ac-HWKL has a more compact structure in an organic solvent than polystyrene.

Synthesis and properties of highly soluble branched polyimide based on 2,4,6-triaminopyrimidine

A series of novel soluble polyimides was synthesized from commercially available 2,4,6-triaminopyrimidine (TAP), 2,2-bis(3,4-dicarboxylphenyl) hexafluoropropane dianhydride (6FDA), α,ω-aminopropylpoly(dimethylsiloxane) and 1,3-bis(3-aminophenoxy)benzene. TAP is the branched monomer, and polymerization process had been improved in three ways by using TAP to prepare soluble polyimides. The polyimides were characterized by Fourier transform infrared spectra, proton nuclear magnetic resonance, ultraviolet–visible spectrometer analysis, wide-angle X-ray diffraction, and size-exclusion chromatography with multiangle laser light-scattering detection. The branched polyimides showed excellent solubility both in strong polar solvents and in common low-boiling point solvents. Differential scanning calorimetric and thermogravimetric analyses showed high glass transition temperatures and excellent thermal stability for branched polyimides with moderate content of TAP. Polyimide membranes were formed at relatively low temperature, and the mechanical properties were tested. These results ensure that soluble polyimides with moderate content of TAP showed outstanding combined features and are desirable candidate materials for advanced applications.

Migration of nanoparticles from plastic packaging materials containing carbon black into foodstuffs

Carbon black was investigated to assess and quantify the possibility that nanoparticles might migrate out of plastic materials used in the food packaging industry. Two types of carbon black were incorporated in low-density polyethylene (LDPE) and polystyrene (PS) at 2.5% and 5.0% loading (w/w), and then subjected to migration studies. The samples were exposed to different food simulants according to European Union Plastics Regulation 10/2011, simulating long-term storage with aqueous and fatty foodstuffs. Asymmetric flow field-flow fractionation (AF4) coupled to a multi-angle laser light-scattering (MALLS) detector was used to separate, characterise and quantify the potential release of nanoparticles. The AF4 method was successful in differentiating carbon black from other matrix components, such as extracted polymer chains, in the migration solution. At a detection limit of 12 µg kg−1, carbon black did not migrate from the packaging material into food simulants. The experimental findings are in agreement with theoretical considerations based on migration modelling. From both the experimental findings and theoretical considerations, it can be concluded that carbon black does not migrate into food once it is incorporated into a plastics food contact material.

Mapping Phase Diagrams of Polymer Solutions by a Combination of Microfluidic Solution Droplets and Laser Light-Scattering Detection

Conventional mapping of a phase diagram of a polymer in a solvent requires a substantial amount of polymer (e.g., at least of the order of ∼100 mg of narrowly distributed samples with different molar masses) and may take months or even years to reach the true two phase equilibrium at each given temperature, especially when the polymer concentration is high. This is why good phase diagrams of polymer solutions are rare in the literature. To solve such a problem, we developed a Teflon microfluidic device to prepare and store a series of droplets (∼10 nL) at different polymer concentrations inside a glass capillary. The phase transition inside each polymer solution droplet sealed and isolated in immiscible fluorohydrocarbon could be quickly and precisely monitored by a newly developed small angle laser light scattering detector. Using poly(vinyl acetate) (PVAc) in isobutyl alcohol and in benzene as two examples, we demonstrated that a combination of microfluidic device and small angle light scattering enables us to map the phase diagram of a polymer in a given solvent within hours by using only a few mg of the sample because (1) each droplet contains no more than ∼10 μg polymer and (2) the phase-transition induced interchain association inside each droplet can be quickly and sensitively detected. We have demonstrated that two sets of a total of eight precisely mapped phase diagrams of four PVAc fractions in the two solvents can be reasonably scaled together to form a master curve.

Lipids of adult brown shrimp,Crangon crangon: seasonal variations in fatty acids class composition

Sea food is very rich in lipids. The brown shrimp,Crangon crangonis a most popular and very valuable taxon in the White Sea, in the Mediterranean and in the Black Seas. The aim of this study was to determine the seasonal variations of lipids inC. crangonmuscle tissue using gas chromatography–mass spectrometry. The lipids were separated into groups: neutral lipids (triacylglycerols, free fatty acids, sterols) and polar lipids (phospholipids), by high performance liquid chromatography with a laser light-scattering detector. Fatty acids were identified using the GC-MS technique. The mainly fatty acids were 16:0, 18:0 (saturated FAs), 16:1, 18:1 (monounsaturated FAs), 20:4 (ARA), 20:5 (EPA) and 22:6 (DHA). The largest amounts of fatty acids in the muscle were observed in spring; these were the result of collecting food after winter and before reproduction. The muscle lipid content was 32.2 ± 1.8 mg g−1. The summer was the poorest season and the lipid value was 7.7 ±0.4 mg g−1. The levels of muscle neutral lipids (NL) oscillated between 80% (autumn) and 90% (spring). The temperature and salinity has a significant influence on content and profile of fatty acids. This work will help to understand the biology, the seasonal variation in lipid mass, lipid classes content and fatty acids profile in the abdominal muscle ofC. crangon.

Synthesis, characterization and properties of TAP-6FDA hyperbranched polyimides with different branching degrees

A series of hyperbranched polyimides were successfully synthesized by condensation polymerization of A2-type dianhydride monomer 2,2-bis(3,4-dicarboxylphenyl) hexafluoropropane dianhydride (6FDA) and B′B2-type triamine monomer 2,4,6-triaminopyrimidine (TAP). Polymers with different branching degrees (DB) and terminated groups were obtained by changing the monomer addition order and the monomer molar ratio. Fourier transform infrared spectroscopy and 1H NMR were used to verify the structure of the prepared polyimides, which indicated that the amino group still existed in all the products. The DB of the polymers indicated by 1H NMR increased from 30% to 79% with the molar ratio of TAP:6FDA decreasing from 1:1 to 1:2. The absolute molecular weights were measured by size-exclusion chromatography with multi-angle laser light-scattering detection, which suggested that the highest molecular weight would be obtained when the molar ratio of amino groups:anhydride groups of the monomers was 3:3.2. With the DB increasing, the d-spacing values indicated by wide angle X-ray diffraction increased from 5.15 Å to 5.68 Å and the UV − visible spectra of the polymers exhibited decreasing cut-off wavelengths. The 5% weight loss temperature in nitrogen increased with decreasing content of TAP monomer, and the glass transition temperatures of the obtained polyimides decreased from 282 °C to 258 °C with increasing DB. © 2013 Society of Chemical Industry

The lipid composition of the abdominal muscle of shrimpCrangon crangonfrom the Gulf of Gdansk in spring and winter periods

The composition of fatty acids and sterols ofCrangon crangonabdomen muscle was determined during two periods in the year 2010/2011. For determination of lipids classes, especially of fatty acids and sterols, high performance liquid chromatography with a laser light-scattering detector and gas chromatography–mass spectrometry were applied. Diversity and variety of saturated and unsaturated fatty acids was the highest during the spring period. Twenty-seven free fatty acids with from nine to 24 carbon atoms were determined in the spring periods. Among this fraction, 14 saturated and 13 unsaturated fatty acids (eight mono- and five polyunsaturated) were present. Only seven saturated and four unsaturated free fatty acids (14:2, 17:1, 16:1 and 18:1) were identified in December 2010. Arachidonic acid (20:4) and eicosapentaenoic acid (20:5) were detected in these two periods, and during the spring season an additional essential fatty acid—docosahexaenoic acid (22:6)—was present, which was not detected in the winter period. The number of identified sterols was correlated with phytoplankton, which was abundant during April 2011. Also, the sterol fraction in winter periods was very poor—only cholesterol was detected.

Identification of Lipid Components in the Abdominal Muscle of Fall-CaughtCrangon crangonfrom a Coastal Area of the Baltic Sea

The main aim of this work was to determine the principal lipid classes and compositions of fatty acids (FFAs) in triacylglycerols (TAGs) and phospholipids in adult shrimps Crangon crangon from coastal areas of the Gulf of Gdansk (Baltic Sea, Poland). High performance liquid chromatography with a laser light-scattering detector (HPLC-LLSD) was used to separate the lipid classes. The FFA composition was determined with gas chromatography-mass spectrometry (GC-MS) and matrix-assisted laser-desorption time-of-flight mass spectrometry (MALDI-TOF-MS). The following lipid classes were separated using HPLC-LLSD: TAGs, FFAs, sterols (ST) and polar lipids (PL). The HPLC-LLSD analysis showed the dominance of sterols, which were missing from MALDI-TOF-MS, sterols made up 2.5 mg g-1 of the total lipids on the basis of this analysis. TAGs and FFAs were the next most abundant lipid classes, accounting 1.9 mg g-1 and 2.0 mg g-1 of the total lipids, respectively.

GPC-低角度光散乱測定法による非線状ブロック共重合体の絶対分子特性化

低角度光散乱光度計付きGPC (GPC-LALLS)を用いて，新たに導出した解析式により非線状ブロック共重合体の絶対分子特性化を行った．ブロック共重合体の二つの組成分布を考慮してこの解析式を求めた．一つ目は異なった分子量におけるそれであり，二つ目は同じ分子量内でのそれである．スチレン基を片末端にもつポリスチレンマクロモノマーとポリイソプレンマクロモノマーを逐次リビングアニオン重合して(PSt)n-star-(PIs)mヘテロアーム星型共重合体を合成した．PSt-graft-ポリ(n-ヘキシルイソシアナート)グラフト共重合体を逐次分解して，グラフト鎖数が異なるグラフト共重合体を合成した．これら非線状ブロック共重合体の絶対分子量をGPC-LALLSにより決定し，組成分布をRIとUV検出器の併用により決定した．(PSt)n-star-(PIs)mの三次元分子量分布や腕鎖数分布も決定した．

Distribution of the number of arms of (PSt)f−n-star-(PIs)n hetero-star block copolymers prepared via anionic living polymerization of macromonomers

The distributions of the number of arms (DNA) of (polystyrene)6.2-star-polyisoprene ((PSt)6.2-star-PIs) and (PSt)7.6-star-(PIs)6.3 hetero-star block copolymers and its precursors prepared via anionic living polymerization of macromonomers have been determined by plotting a weight fraction of the number of arms against the number of arms. Three-dimensional molecular weight distributions (3D-MwD) of the two hetero-star block copolymers and its precursors were also determined by plotting a weight fraction at the ith elution volume against the corresponding molecular weight (Mi) and ith elution volume using GPC in conjunction with a low-angle laser light-scattering detector, a refractive index detector, and an ultraviolet detector. A non-linear relationship between the ith elution volume and Mi of (PSt)6.2-star-PIs was observed and explained from a gstar perspective. The present paper describes the analytical method for determination of the DNA using the MwD. The DNAs of the six samples were found to be narrow and similar to the MwDs of the corresponding samples. The synthetic mechanism of the hetero-star block copolymers was discussed from a DNA perspective.

Composition and Molecular Size of Clostridium botulinum Type A Toxin–Hemagglutinin Complex

Pickett and Perrow have expressed several concerns regarding our recent publication on the stoichiometry of the Clostridium botulinum type A-Hall (Allergan) neurotoxin complex [1, 2]. These concerns demonstrate a misunderstanding regarding the purpose of our publication, which was focused on determining the subunit composition and homogeneity of this complex. Although the results in our publication were obtained with the C. botulinum type A neurotoxin complex used to manufacture BOTOX , it was not our goal to compare various type A neurotoxin complex products currently in clinical use. Based on current literature, knowledge regarding the number of each subunit present in the intact C. botulinum type A neurotoxin complex is extremely limited, even though the complex was purified to homogeneity more than 50 years ago [3, 4]. To date multiple reports exist in the literature suggesting that the 900 kDa complex is a dimer of a 500 kDa complex although there is limited evidence to support this [5, 6]. We established a quantitative procedure to determine the relative subunit composition and to confirm the molecular mass of our neurotoxin complex. As discussed in detail in our publication, we ensured that the established procedure was appropriate for this purpose by verifying both the recovery of the complex subunits as well as the overall consistency of the method. In addition, we clearly described our assumptions regarding the interpretation of the electropherograms, including our approach for handling the co-elution of the HA48 and the light chain subunits. We are, therefore, confident that our capillary electrophoresis method provides a valid procedure for quantifying the subunit stoichiometry of the neurotoxin complex. In contrast, sodium dodecyl sulfate-poly-acrylamide gel electrophoresis (SDS–PAGE) combined with mass spectrometry, as suggested by Pickett and Perrow, would not be suitable for this purpose since such an approach would only provide the molecular mass and the identity of proteins, and provide little if any information regarding the subunit stoichiometry. Analytical methods that evaluate the neurotoxin complex under denaturing conditions, including the capillary electrophoresis method described by us, cannot be used to establish whether the subunits form a single protein complex. We therefore, confirmed the integrity of the neurotoxin complex by size-exclusion HPLC in conjunction with multi-angle laser light-scattering detection. The molecular mass obtained for the neurotoxin complex shows that the different subunits identified in the electropherograms are part of a single complex and the results support the proposed subunit composition. The close agreement between the neurotoxin complex molecular mass values obtained by us and the complex mass values reported in earlier publications, while perhaps ‘‘unremarkable’’, confirms that the Allergan type A neurotoxin complex used to manufacture BOTOX consists of a homogeneous *900 kDa species containing one 150 kDa neurotoxin molecule per complex.

Crystal Structures of NADH:FMN Oxidoreductase (EmoB) at Different Stages of Catalysis

EDTA has become a major organic pollutant in the environment because of its extreme usage and resistance to biodegradation. Recently, two critical enzymes, EDTA monooxygenase (EmoA) and NADH:FMN oxidoreductase (EmoB), belonging to the newly established two-component flavin-diffusible monooxygenase family, were identified in the EDTA degradation pathway in Mesorhizobium sp. BNC1. EmoA is an FMNH2-dependent enzyme that requires EmoB to provide FMNH2 for the conversion of EDTA to ethylenediaminediacetate. To understand the molecular basis of this FMN-mediated reaction, the crystal structures of the apo-form, FMN.FMN complex, and FMN.NADH complex of EmoB were determined at 2.5 angstroms resolution. The structure of EmoB is a homotetramer consisting of four alpha/beta-single-domain monomers of five parallel beta-strands flanked by five alpha-helices, which is quite different from those of other known two-component flavin-diffusible monooxygenase family members, such as PheA2 and HpaC, in terms of both tertiary and quaternary structures. For the first time, the crystal structures of both the FMN.FMN and FMN.NADH complexes of an NADH:FMN oxidoreductase were determined. Two stacked isoalloxazine rings and nicotinamide/isoalloxazine rings were at a proper distance for hydride transfer. The structures indicated a ping-pong reaction mechanism, which was confirmed by activity assays. Thus, the structural data offer detailed mechanistic information for hydride transfer between NADH to an enzyme-bound FMN and between the bound FMNH2 and a diffusible FMN.

Asymmetrical flow field-flow fractionation coupled to multiangle laser light scattering detector: optimization of crossflow rate, carrier characteristics, and injected mass in alginate separation.

The coupling of the flow field-flow fractionation (FlFFF) to differential refractive index (DRI) and multiangle laser light scattering (LS) detectors is a powerful tool for characterizing charged polysaccharides such as alginate. However, the correct interpretation of the experimental results and extrapolation of meaningful molecular parameters by using an analytical tool with such a level of complexity requires improvement of the knowledge of the alginate behavior in the channel and careful optimization of the operating conditions. Therefore, the influence of the critical operating parameters, such as crossflow rate, carrier composition and concentration, and sample load, on the alginate retention was carefully evaluated. Combined information obtained simultaneously by DRI and LS detectors over the wide range of the crossflow rate, carrier liquid concentration, and injected amount, allowed to set the appropriate combination of optimal parameters. It was found that the crossflow rate of 0.25 mL/min, carrier solution containing 5x10(-2 )mol/L ammonium or sodium chloride, and 50-100 microg of injected sample mass were necessary to achieve complete separation and determination of the meaningful molecular characteristics. The values of the weight-average hydrodynamic radius (R(Hw)), radius of gyration (R(G)), and molar mass (M), obtained under the optimal conditions were in good agreement to those found for alginates in the literature.

Anionic Living Polymerization of Macromonomers: Preparation of (A)n-star-(B)1Star Block Copolymers and Some Properties of the Products Obtained

(4-Vinylbenzyl)polystyrene macromonomer (PStM, Mn = 5.45 × 103, Mw/Mn = 1.03) was living-anionically polymerized by sec-BuLi to produce the (PSt)n- star polymer under high vacuum at room temperature. Then, isoprene (Is) was sequentially copolymerized by (PSt)n- to yield the (PSt)6.1-s-(PIs)1 star block copolymer (Mn = 6.39 × 104, Mw/Mn = 1.04) having a narrow PIs composition distribution. Similarly, the (PIs)6.6-s-(PSt)1 star block copolymer (Mn = 10.8 × 104, Mw/Mn = 1.04) was prepared using (4-vinylbenzyl)polyisoprene macromonomer (PIsM, Mn = 5.19 × 103, Mw/Mn = 1.04). The synthetic route by which the PIs- carbanions copolymerize PStM was found to be unsuitable for preparing (PIs)1-star-(PSt)n. The resultant star polymers and star block copolymers were characterized by a special analysis using a gel permeation chromatograph equipped with a low-angle laser light-scattering detector. The living mechanism of the macromonomers polymerization was discussed from the viewpoint of initiation efficiency. The asym...

マクロモノマーのアニオンリビング重合により合成された星型高分子の腕鎖数分布

From a number fraction (nf) of the number of arms (f) for (PSt)f star polymers prepared via anionic living polymerization of polystyrene macromonomers (PStM), the distribution in number of arms, (f∼nf) has been determined. From a number fraction of polymer (Nf, i) having a degree of polymerization (i), each distribution in a degree of polymerization of (PSt)f, (i∼Nf, i) was first calculated using Nf, i=∑i=j+k (N(f-1), jN1, k) and (i∼N1, i) of the PStM, and then the distribution in a degree of polymerization of (PSt)<f>, (i∼N<f>, i)cal was calculated by N<f>, ical=∑fnfNf, i, where <f> is an average number of arms. By comparing the resultant (i∼N<f>, i)cal with (i∼N<f>, i)obs determined by GPC equipped with a low-angle laser light-scattering detector, each (f∼nf) of the five (PSt)f star polymers was determined. From the polymerization time dependence of the resultant (f∼nf) and polymerization conditions, a non-linear polymerization rate constant and its mechanism were discussed.

Simultaneous determination of protein aggregation, degradation, and absolute molecular weight by size exclusion chromatography–multiangle laser light scattering

The feasibility of size exclusion chromotography (SEC)–multiangle laser-light scattering as a technique to investigate aggregation and degradation of glycosylated and nonglycosylated proteins, and antibodies under various conditions such as addition of detergent, changes in pH, and variation of protein concentration and heat stress temperature was examined. Separation of proteins and their aggregates was performed using SEC–high-performance liquid chromatography. Detection of analytes was carried out with on-line UV, refractive index, and multiangle laser light-scattering detectors. Quantification and molecular weight determination were performed using commercial software. Aggregation and degradation were examined under various conditions and quantitative results are presented for bovine serum albumin, choriogonadotropin, glyceraldehyde-3-phosphate dehydrogenase, Herceptin, and ReoPro. This method can simultaneously determine both the quantities and the molecular weights of macromolecules from a single injection. The determination of molecular weight is absolute which avoids misleading results caused by molecular shape or interactions with the column matrix. This technique is valuable not only for assessing the extent of aggregation but also for effectively monitoring molecule degradation as evidenced by molecular weight reduction and change in monomer amount.

Problematyka zwiazana z niektorymi kierunkami zastosowania polidimetylosiloksanow oraz mozliwosci analizy tych zwiazkow

The fields of polydimethylsiloxanes (PDMS) applications for food contact and in pharmaceuticals were presented. An importance of a choice of the proper only linear PDMS characterized with the appropriate polymerization degree, as only permissible according to the regulations being in force, was stressed. Speciation analysis and analytical methods (limit of detection and specificity, Scheme I, Table 1 and 2), allowing the proper differentiation of the substances studied, were discussed. Especially the method of liquid chromatography with laser light scattering detector (LLSD) applied was considered. It should fulfill the best the requirements of analysis of PDMS discussed.