Rapid identification and semi-quantitative determination of polymer additives by desorption electrospray ionization/time-of-flight mass spectrometry

A fast and simple method for the direct qualitative and semi-quantitative determination of a set of four polymer additives in plastic samples by desorption electrospray ionization time-of-flight mass spectrometry (DESI-TOF-MS) is presented. After evaluation of crucial DESI parameters such as composition of spray solutions and spray voltages, a series of lab-made polypropylene samples containing Chimassorb 81 (2-hydroxy-4-n-octoxybenzophenone), Tinuvin 328 (2-(2-hydroxy-3, 5-ditert-pentylphenyl)-benzotriazole), Tinuvin 326 (2-(2-hydroxy-3-tert-butyl-5-methylphenyl)-5-chloro benzotriazole), and Tinuvin 770 (bis(2,2,6,6,-tetramethyl-4-piperidyl)sebaceate) in concentrations between 0.02% and 0.2% were analyzed, resulting in calibration graphs with R ² better than 0.994. To demonstrate the applicability of the developed method for the investigation of real samples, liners for in-ground swimming pools and polypropylene granules were analyzed with respect to their content in the selected polymer additives. Two alternative methods, both well established in the fields of polymer additive analysis, namely HPLC with UV detection (after previous extraction) and thermodesorption gas chromatography/mass spectrometry have been employed for evaluation of the results from the DESI experiments.     

Role of the UV absorber as a matrix in matrix‐assisted laser desorption/ionization mass spectrometric analysis of a mixture of a UV absorber and a stabilizer

A mixture of a UV absorber (Tinuvin 234 or Tinuvin 329) and a UV stabilizer (Tinuvin 770) was analyzed using matrix‐assisted laser desorption/ionization mass spectrometry (MALDI‐MS) without any matrix. Fragmentation patterns of the UV absorbers and stabilizer were also investigated. The mass spectra showed the [M+H]⁺ ions and some fragment ions. Tinuvin 234, Tinuvin 329, and Tinuvin 770 generated three (m/z 119, 370, 432), one (m/z 252), and two (m/z 124 and 140) fragment ions, repectively. These fragment ions can be used to identify the chemical structures of the UV absorbers and stabilizer. Since the UV absorber performed a role as the matrix, the ion abundance of the UV stabilizer was enhanced by mixing with the UV absorber. When organic materials extracted from polypropylene (PP) containing the UV absorber and stabilizer were directly analyzed using MALDI‐MS without any matrix, the protonated molecule of the UV stabilizer was detected in abundance but the product ions of the UV absorber were not observed. When 2,5‐dihydroxybenzoic acid was used as a matrix, the protonated molecule of the UV absorber was observed. Copyright © 2010 John Wiley & Sons, Ltd.     

The photo-oxidation of polyolefins containing a hindered piperidine compound

The rate of oxygen absorption by unstabilised PE and PP, as well as by the same polymers stabilised with bis-(2,2,6,6-tetramethyl-4-piperidinyl) sebacate (Tinuvin 770), has been determined during photo-oxidation at several temperatures and uv light intensities. In addition, the rate of stabiliser conversion has been measured under various irradiation conditions, including outdoor exposure. The activation energy of the conversion of Tinuvin 770 appears to be much less than that of the photo-oxidation of PE. When stabilised with 0·1% Tinuvin 770, PE and PP differ with respect to the dependence on light intensity of their rates of oxygen uptake. The consequences of these results for the interpretation of accelerated ageing tests are discussed.     

The photo-stabilising action of metal chelates in polypropylene: Part IX—Practical synergism with other commercial systems and the importance of calcium stearate

The photo-stabilising action of three metal chelates (Cyasorb UV 1084, Irganox 1425 and Irgastab 2002) in a number of synergistic formulations with three commercial stabilising systems (Weston 618, Cyasorb UV 531 and Tinuvin 770), in polypropylene films has been examined. The results show that, although antagonistic effects are observed at some mass ratios, synergistic effects prevail at others. The effects are a function of the particular formulation.The addition of calcium stearate to the stabilising mixture can have marked effects on the observed behaviour. Thus, an antagonistic effect can become synergistic if calcium stearate is used in the formulation. The results have scientific and technological implications as calcium stearate is often used as a processing aid in the stabilisation of polypropylene.     

SYNTHESIS AND EVALUATION OF A NEW PHOTOSTABILIZER—2, 2, 6, 6-TETRAMETHYL-4-PIPERIDINYL SALICYLATE FOR POLYMERS

A new photostabilizer--2,2,6,6-tetramethyl-4-piperidinylsalicylate (TMPS) has been syn-thesized by ester-exchange reaction between 2,2, 6, 6-tetramethyl-4-piperidinol and methylsalicylate.The photostabilizing effect of TMPS and Tinuvin 770, PDS on the photodegradation of cis-1,4-polybutadiene has been investigated for comparison. The results observed show that the mosteffective stabilizer of the three is TMPS. The reason of the good photostabilizing effect of TMPSwas discussed by fluorescence spectra.     

Optimization of mass spectrometry acquisition parameters for determination of polycarbonate additives,degradation products,and colorants migrating from food contact materials to chocolate

The interest towards “substances of emerging concerns” referred to objects intended to come into contact with food is recently growing. Such substances can be found in traces in simulants and in food products put in contact with plastic materials. In this context, it is important to set up analytical systems characterized by high sensitivity and to improve detection parameters to enhance signals. This work was aimed at optimizing a method based on UHPLC coupled to high resolution mass spectrometry to quantify the most common plastic additives, and able to detect the presence of polymers degradation products and coloring agents migrating from plastic re‐usable containers. The optimization of mass spectrometric parameter settings for quantitative analysis of additives has been achieved by a chemometric approach, using a full factorial and d‐optimal experimental designs, allowing to evaluate possible interactions between the investigated parameters. Results showed that the optimized method was characterized by improved features in terms of sensitivity respect to existing methods and was successfully applied to the analysis of a complex model food system such as chocolate put in contact with 14 polycarbonate tableware samples. A new procedure for sample pre‐treatment was carried out and validated, showing high reliability. Results reported, for the first time, the presence of several molecules migrating to chocolate, in particular belonging to plastic additives, such Cyasorb UV5411, Tinuvin 234, Uvitex OB, and oligomers, whose amount was found to be correlated to age and degree of damage of the containers.     

Quantitative Analysis of Polymer Additives with MALDI-TOF MS Using an Internal Standard Approach

MALDI-TOF MS is used for the qualitative analysis of seven different polymer additives directly from the polymer without tedious sample pretreatment. Additionally, by using a solid sample preparation technique, which avoids the concentration gradient problems known to occur with dried droplets and by adding tetraphenylporphyrine as an internal standard to the matrix, it is possible to perform quantitative analysis of additives directly from the polymer sample. Calibration curves for Tinuvin 770, Tinuvin 622, Irganox 1024, Irganox 1010, Irgafos 168, and Chimassorb 944 are presented, showing coefficients of determination between 0.911 and 0.990.     

Comprehensive on-line HPLC-GC for screening potential migrants from polypropylene into food: The effect of pulsed light decontamination as an example

High performance liquid chromatography (HPLC) was used for the fractionation of extracts from polypropylene (PP) films and coupled on-line to gas chromatography (GC) with automated transfer of the complete HPLC fractions (comprehensive on-line HPLC-GC, i.e. HPLCxGC). Flame ionization detection (FID) was used for the estimation of concentrations, mass spectrometry (MS) for identification work. This method was applied to investigate whether pulsed light (PL) treatment for the microbiological decontamination of polypropylene packaging materials produces reaction products requiring an evaluation to meet regulatory requirements. To demonstrate the safety of PL treatments with regard to the formation of reaction products, i.e. that no component is formed that could endanger human health, basically comprehensive analysis of components potentially migrating into food is required, but comprehensiveness cannot be proven and remains an approximation. The threshold concentration in the film was estimated either from the conventional European non-detection limit of 0.01 mg/kg food or the concept of the threshold of toxicological concern (TTC) for an unknown substance, i.e. an exposure to 0.15 μg per person and day. PL treatment of the films containing Irgafos 168 produced several new components exceeding these limits, i.e. a toxicological safety assessment would probably be required. No such peaks were detected for Tinuvin 326, Irganox 1076 and Chimassorb 81. No degradation of the polymer was detected.     

一种新型的高聚物的光稳定剂——4-(水杨酸)2,2,6,6-四甲基哌啶醇酯的合成及其光稳定能力的评价

<正> 自1967年日本Sankyo公司发现2,2,6,6-四甲基哌啶化合物具有良好的光稳定能力以来,对该类化合物的研究与开发工作已取得很大的进展。不同结构的衍生物作为正式商品不断问世,同时作为添加剂已在许多大品种烯类聚合物制品中得到广泛的应用,然而它作为一种光稳定剂其稳定效能在某些方面仍不能令人满意,如对紫外辐射屏蔽作用,由于它在300—350 nm波长范围内只有较小的克分子吸收系数,因此是不够理想     

固相萃取-高效液相色谱法同时测定食品塑料包装材料中9种光稳定剂

建立了同时测定食品塑料包装材料中9种紫外光稳定剂含量的高效液相色谱方法。样品用甲醇-乙酸乙酯混合溶剂超声提取,经固相萃取小柱净化后,以ZORBAX SB-C18柱(250 mm×4.6 mm, 5 μm)为分离色谱柱,甲醇和水为流动相,梯度洗脱,以310 nm为检测波长进行定性、定量分析。该方法前处理简单、易操作,9种紫外光稳定剂分离效果良好。9种紫外光稳定剂在0.2～10 mg/L范围内呈良好的线性关系,线性相关系数大于0.999;方法检出限为0.05～0.1 mg/L;实际样品中的加标回收率为70.2%～89.0%,相对标准偏差为0.4%～4.5%。该方法简单、准确,能够满足食品塑料包装材料中紫外光稳定剂的检测要求。     

Silk Fibroin‐Based Fibrous Anal Fistula Plug with Drug Delivery Function

The aim of this work is to develop a drug‐loaded silk fibroin fibrous membrane (DSFM) that can be attached to the surface of an anal fistula plug to improve the treatment of Crohn's disease (CD). Curcumin (CUR) and 5‐aminosalicylic acid (5‐ASA)‐loaded silk fibroin (SF) membranes are coaxially electrospun onto the surface of a braided silk filament plug. The membranes show a predominant structure of random coil and silk I conformation. The concentration of CUR/5‐ASA (weight ratio of 1/1) in the SF solution is optimized to 0.4, 0.9, and 1.9 wt%. The morphologies, secondary structures, and in vitro drug release properties of the membranes are examined. Sectional images of fibers in the membranes show core–shell structures. The coaxial electrospinning process does not alter the chemical characteristics of the drugs. The dual‐drugs encapsulated in the membranes are released in a steady and sustainable manner, and the cumulative release rate is improved by the increased drug loading. The membranes exhibit no cytotoxicity, thereafter increase the viability of human fibroblasts on the DSFMs. These SF membranes with core–shell structure and functional encapsulation of CUR and 5‐ASA should be useful for further studies toward the treatment of CD.     

Determination of glycyrrhetinic acid in human plasma by high-performance liquid chromatography.

A high-performance liquid chromatographic (HPLC) method has been developed for measuring 18 beta-glycyrrhetinic acid (GRA) in human plasma in the range of 0.1-3 micrograms/ml. The acetate ester of GRA is added to the plasma as an internal standard, plasma proteins are denatured with urea to release GRA, and the GRA and the internal standard are extracted in an ion-pairing solid-phase extraction process. An isocratic, reversed-phase HPLC separation is used, followed by ultraviolet absorbance detection at 248 nm. The results from the analysis of five GRA-fortified plasma pools show a mean relative standard deviation of 7% and are accurate to within 10%. With evaporative concentration of the extract, the limit of detection for GRA in plasma is approximately 10 ng/ml.     

Photo-stabilising action of metal chelate stabilisers in polypropylene: Part VII—Additive interactions

The interactions of three metal chelates (nickel (II) 2,2′-thiobis (4-tertoctyl-phenolato), n-butylamine (Cyasorb UV 1084) and the nickel and calcium derivatives of bis(ethyl-3,5-di-tert-butyl-4-hydroxybenzyl) phosphonate (Irgastab 2002 and Irganox 1425)) with other commercial additives, in the stabilisation of polypropylene film, are examined using normal and second-order derivative ultraviolet and infra-red spectroscopic techniques. It is shown that the observed behaviour is dependent on the particular additive, the processing history of the polymer and the metal chelate concerned, and is therefore highly complex. All three chelates show antagonism with a hindered piperidine, bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate (Tinuvin 770), in unprocessed polymer, whereas one of the chelates behaves synergistically with this additive in processed samples. The chelates also show antagonism with a primary antioxidant, tris((3-(3′,5′-di-tert-butyl-4-hydroxybenzyl)-2′'-aceto-ethyl)) isocyanurate (Goodrite 3125), whereas, with a secondary antioxidant, distearyl pent-aerithrityl diphosphite (Weston 618), their behaviour is synergistic in both unprocessed and processed polymer. Two of the chelates show synergism with 2-hydroxy-4-n-octoxybenzophenone (Cyasorb UV 531), the remaining chelate showing antagonism. Mixtures containing a three-additive system show a more complex behaviour. The results are explained in terms of hydroperoxide decomposition, inhibition, stabiliser dispersion, ultraviolet stability and additive compatibility.     

Surface-Anchored Hindered-Amine Light Stabilizers for Improved UV Stability of Polyolefins

Abstract

Hindered-amine light stabilizers (HALS) were surface anchored to polyolefin films by reacting the HALS, namely, 1,2,2,6,6-pentamethyl-4-piperidinol and 1,2,2,6,6-pentamethyl-4-aminopiperidine, with succinic anhydride functionalized polyolefin surfaces. The photostability of polyolefin films with surface-anchored HALS were compared with films stabilized with commercial HALS (Tinuvin 770) by melt blending. It is shown that the photostabilizing efficiency of surface-anchored HALS is superior that of melt-blended polyolefins.     

Conducting polymer membranes for low activity potentiometric ion sensing

Conducting polymer (CP) films, used as ion-sensing membranes under open circuit potentiometric conditions, are usually characterised with rather high detection limit, in the range of 10⁻⁴-10⁻⁵ mol dm⁻³. This effect is unfavourable, not only from the point of view of CP applications in potentiometry as ion sensitive membranes, but also when these materials are used as ion-to-electron transducers (solid contacts) for ion-selective electrodes. The theoretical considerations presented underline the crucial role of spontaneous processes of polymer charging/discharging—the source of observed high detection limit of sensors comprising CP layer under zero current conditions. Although the mechanism of occurring process is different from that observed for plastic, solvent polymeric based ion-selective electrodes, the ultimate result—alteration of activity of electrolyte at the membrane/solution interface leading to elevation of the detection limit—is the same.The method of estimation of parameters characterising spontaneous charge transfer processes is presented. The values obtained can be used to calculate the resulting polymer/solution interface activity of electrolyte ions, thus the detection limit of CP membrane can be theoretically predicted.A method of lowering of the detection limit of conducting polymer membranes, applying galvanostatic polarisation to compensate the spontaneous process of polymer charging/discharging, is presented.The experimental results obtained for poly(pyrrole), poly(N-methylpyrrole) and poly(3,4-ethylenedioxythiophene) are in good accordance with predictions of the presented model.     

Extraction of polypropylene additives and their analysis by HPLC

Summary The polypropylene additives were extracted by dissolution-precipitation and Soxhlet. The Soxhlet method was adapted for the extraction of phosphorous antioxidants. The RP HPLC method with quaternary gradient elution separated five chemical groups of additives: lower molecular mass di-tert-butyl phenol (D.T.B.P.), hindered amine light stabilizers (Tinuvin 326), hindered phenolic antioxidants (Irganox 1010) and phosphorous antioxidants (Irgafos 168 and Ultranox 626) with their degradation products.     

Comparison of GC and HPLC Methods for Quantitative Analysis of Tinuvin 622 After Saponification in Polyethylene

This study describes the sample preparation and two chromatographic techniques for determination of Tinuvin 622 in polyethylene. The first part of the two methods consisting of dissolving the polyethylene in boiling xylene is followed by addition of a methanolic solution of potassium hydroxide. The polymeric light stabilizer, Tinuvin 622, is thereby saponified to 4-hydroxy-2,2,6,6-tetramethyl-1-piperidineethanol (diol). Addition of the methanolic solution of the saponification reagent simultaneously precipitates the polyethylene matrix. Then the diol is quantified using either gas chromatography (GC) or high performance liquid chromatography (HPLC). For GC, a Macherey Nagel Optima-17 capillary column (30m×0.25mm ID, film thickness 0.25µm) is used. Nitrogen is used as carrier gas and make-up gas. The detection system is a flame ionization detector. For HPLC, an octadecyl silane (ODS) column (30cm×4mm, particle size 5µm) and a mobile phase methanol: water mixture (3:97, v/v) are used. Detection of analyte is carried out at 215nm. Both methods can be used to determine Tinuvin 622 in polyethylene in the concentration range of 0.02–1%, which represents the usual application concentration.     

Molecularly imprinted microspheres for the anticancer drug aminoglutethimide: Synthesis,characterization, and solid‐phase extraction applications in human urine samples

Molecularly imprinted microspheres (MIMs) for the anticancer drug aminoglutethimide (AG) were synthesized by aqueous suspension polymerization. The expected size and diameter of MIMs are controlled easily by changing one of the surfactant types, ratio of organic‐to‐water phase or stirring rate during polymerization. The obtained MIMs exhibit specific affinity toward AG with imprinting factor of 3.11 evaluated with a chromatographic model. The resultant MIMs were used as the SPE materials for the extraction of AG from human urine. A molecularly imprinted SPE (MISPE) method coupled with HPLC has been developed for the extraction and detection of AG in urine. Our results showed that most impurities from urine can be removed effectively after a washing step and the AG has been enriched effectively after MISPE operation with the recovery of >90% (n = 3). The developed MISPE–HPLC method could be used for enrichment and detection of AG in human urine.     

Mechanisms of antioxidant action: Nitrosamines as heat and light stabilisers for polypropylene

N-Nitrosamines are shown to be very effective melt stabilisers for polypropylene and one of these, derived from the hindered amine light stabiliser, Tinuvin 770, is almost twice as effective as the latter. The mechanism is believed to involve the formation of two kinds of nitroxyl radical, the first derived from the amine and the second formed by the reaction of nitric oxide with alkyl, and possibly alkoxyl, radicals. Nitrosamines which do not dissociate to NO are neither melt stabilisers nor uv stabilisers.     

Determination of [S,S']-ethylenediaminedisuccinic acid by high-performance liquid chromatography

A new high-performance liquid chromatography (HPLC) method for the determination of ethylenediaminedisuccinic acid (EDDS) is presented. Free EDDS(4-) and EDDS complexes with divalent metals undergo conversion to the Fe(III) complex in the presence of Fe(III)Cl(3). Fe(III)EDDS is separated by HPLC on an ion exchange column using (NH(4))(2)SO(4) eluent with detection at 258 nm. The detection limit is 0.01 microM. The method is applied to natural waters and soil solution samples. A background of natural water results in a reduction in EDDS peak area. The method is suited for EDDS analysis in samples with well-defined, simple matrices such as those used in laboratory experiments or biodegradation studies.