Determination of hexamethylene-based isocyanates in spray-painting operations. Part 1. Evaluation of a polyurethane foam sponge sampler

A polyurethane foam (PUF) sponge was mounted in a cassette sampler and evaluated as a sorbent for the collection of hexamethylene diisocyanate (HDI) monomer and HDI-based oligomers. Recovery studies indicated 112 +/- 34% average recovery of HDI monomer and 92 +/- 9% and 97 +/- 25% average recovery of HDI-based oligomers when using impregnated PUF sponges. The PUF sponge was also evaluated during actual spray-painting operations. In a series of side-by-side sampling events, an impinger filled with 1-(2-methoxyphenyl)piperazine (MOP) in toluene was compared directly with a cassette sampler containing a PUF sponge impregnated with MOP or 1-(9-anthracenylmethyl)piperazine (MAP) in dimethyl sulfoxide (DMSO). For the analysis of HDI-based oligomer, there is no significant difference (p < 0.05, n = 7) in the air concentration when sampling with either the PUF sponge cassette or the impinger. The results are significant because they indicate that a PUF sponge, which is more convenient than an impinger, may be used for the collection of HDI-based oligomer generated during spray-painting operations.     

流动注射-毛细管电泳分流式电动进样歧视效应特征的研究

以碱性药物盐酸伪麻黄碱和酸性药物布洛芬为对象研究了分流式电动进样(一种用于流动注射-毛细管电泳(FI-CE)联用系统的新进样方法)歧视效应的特性。结果发现:在样品介质与运行缓冲液一致的条件下,FI-CE分流式电动进样产生的歧视效应与电动进样相似,但获得的校正曲线的线性明显优于电动进样,而与没有歧视效应的压力进样所获得的线性相似。利用这些特征提高了同时测定复方布洛芬片中少量组分盐酸伪麻黄碱和主要组分布洛芬的分析性能。在24次/h的采样频率下,盐酸伪麻黄碱的检测限为0.7 mg/L,比采用压力进样的毛细管电泳法所得的检测限低30%。连续进样11次分析含有13.1 mg/L盐酸伪麻黄碱和81.4 mg/L布洛芬的试样溶液,峰面积的相对标准偏差分别为2.8%(盐酸伪麻黄碱)和1.2%(布洛芬),明显优于采用压力进样的毛细管电泳法。用该法测定了两批复方布洛芬片中两种组分的含量,所得结果与高效液相色谱法的测定结果一致。     

Study on characteristics of bias caused by FI-CE split flow electrokinetic injection

The characteristics of bias caused by split-flow electrokinetic injection (SEKI), a new type of sample injection method used in coupled flow injection-capillary electrophoresis system (FI-CE), was investigated using pseudoephedrine hydrochloride, a basic drug, and ibuprofen, an acidic drug, as model analytes. It was found that bias imposed by SEKI under the condition of continuous sample matrix/running buffer was similar to that done by electrokinetic injection (EKI). The linearity of calibration curve provided by SEKI was similar to that offered by non-bias hydrodynamic injection (HDI) but significantly better than that obtained by EKI. These features were exploited to improve analytical performances in simultaneous determination of the minor ingredient of pseudoephedrine hydrochloride and the major ingredient of ibuprofen in a pharmaceutical preparation. Detectability of 0.7 mg/l for pseudoephedrine hydrochloride was achieved at a sample throughput rate of 24 times per hour, which is 30% lower than that obtained by HDI-based conventional CE. Relative standard deviations (RSDs) of 2.8% for the minor ingredient and 1.2% for the major ingredient were produced in 11 runs of a test solution containing 13.1 mg/l pseudoephedrine hydrochloride and 81.4 mg/l ibuprofen. This is an improvement compared to that obtained by HDI-based conventional CE. Analytical results for two batches of compound ibuprofen tablets by the SEKI-based FI-CE approach were in good agreement with that obtained by a conventional high performance liquid chromatographic method. __________ Translated from Chinese Journal of Chromatography, 2005, 23(2) (in Chinese)     

Determination of (E)-10-hydroxy-2-decenoic acid content in pure royal jelly: a comparison between a new CZE method and HPLC

A new CZE method was developed and compared with HPLC for the determination of (E)-10-hydroxy-2-decenoic acid (10-HDA) in royal jelly (RJ) samples of different geographical origin. The results obtained with the CZE method were highly correlated with those of HPLC (p < 0.01). Under optimized conditions, CZE employed minimal amounts of 50 mM tetraborate buffer as BGE, without the addition of organic solvents, EOF or pH modifiers. The CZE method showed a wide linear response range (0.006-0.808 mg 10-HDA/mL), a good sensitivity (LOD and LOQ were 0.002 and 0.004 mg/mL, respectively) and a satisfactory instrumental repeatability with respect to migration time and peak area (RSD% less than 1.0 and 2.0% on migration time for intra- and interday assay, respectively and less than 2.0 and for 4.0% on peak area for intra- and interday assay, respectively). The 10-HDA content in RJ ranged from 0.8 to 3.2 g/100 g of RJ and a significant difference (p < 0.05) was found between the Italian and extra-European average values: 2.5 and 1.6 g/100 g of RJ, respectively, according to the CZE data. The possibility of application of CZE for routine analyses on RJ and RJ based products to verify their authenticity is highlighted here.     

Use of experimental design and effective mobility calculations to develop a method for the determination of antimicrobials by capillary electrophoresis

A capillary zone electrophoresis (CZE) method for the determination of chloramphenicol (CLP), danofloxacin (DANO), ciprofloxacin (CIPRO), enrofloxacin (ENRO), sulfamethazine (SMZ), sulfaquinoxaline (SQX) and sulfamethoxazole (SMX) is described. For the development, the effective mobilities were estimated and a central composite design was performed. The method was in-house validated for CLP, CIPRO, ENRO and SMX determination in pharmaceuticals. In comparison with the HPLC method recommended by the United States Pharmacopoeia, this CZE method exhibited the same performance, with the advantage that seven different antimicrobials in pharmaceutical formulations could be simultaneously determined.     

Capillary zone electrophoresis determination of carbohydrate-deficient transferrin using the new CEofix reagents under high-resolution conditions

Capillary zone electrophoresis (CZE) with a dynamic double coating based on the new CEofix reagents is shown to provide high-resolution separations of serum transferrin (Tf) isoforms, a prerequisite for the monitoring of unusual and complex Tf patterns, including those seen with genetic variants and disorders of glycosylation. A 50 microm I.D. fused-silica capillary of 60 cm total length, an applied voltage of 20 kV and a capillary temperature of 30 degrees C results in 15 min CZE runs of high assay precision and thus provides a robust approach for the determination of carbohydrate-deficient transferrin (CDT, sum of asialo-Tf and disialo-Tf in relation to total Tf) in human serum. Except for selected samples of patients with severe liver diseases and sera with high levels of paraproteins, interference-free Tf patterns are detected. Compared with the use of the previous CEofix reagents for CDT under the same instrumental conditions, the resolution between disialo-Tf and trisialo-Tf is significantly higher (1.7 versus 1.4). The CDT levels of reference and patient sera are comparable, suggesting that the new assay can be applied for screening and confirmation analyses. The high-resolution CZE assay represents an attractive alternative to HPLC and can be regarded as a candidate of a reference method for CDT.     

Determination of aristolochic acid by capillary zone electrophoresis

A simple and rapid capillary zone electrophoresis (CZE) method for the determination of aristolochic acid (AA) in dietary supplements and selected herbs is described. A clear separation of AA from other sample constituents was achieved within 5 minutes without any sample clean up. A mixture of 20 mM-morpholinethanesulphonic acid+10 mM-BisTrisPropane+0.2% hydroxyethylcelullose in 10% methanol serves as a background electrolyte. The linearity, accuracy, intra-assay and detection limit of the developed method are 200–6000 ng/mL, 95–103%, 3.5%, and 50 ng/ml, respectively. Ease of use, sufficient sensitivity and low running cost are the most important attributes of the CZE method. The proposed CZE method was compared with HPLC.     

Analysis of melamine resins by capillary zone electrophoresis with electrospray ionization-mass spectrometric detection

A method for the determination of the major components of (methoxymethyl)melamine resins, with quantitative analysis of unreacted melamine by capillary zone electrophoresis (CZE) using electrospray ionization-mass spectrometry (ESI-MS) is presented. Using a low background electrolyte (BGE) pH, components are separated according to their charge/ionic radius ratio with a distinctly different separation selectivity compared to the HPLC methods commonly employed in melamine-resin analysis. The use of a time-of-flight mass spectrometer (TOF-MS) was concluded to be necessary, as the complex samples studied required maximum sensitivity and resolution, which is clearly superior for TOF-MS detectors over their quadrupole counterparts. A standard curve of free melamine was determined with an R(2) = 0.999 over a concentration range of an order of magnitude. This method offers the unique separation selectivity of CZE as well as a quicker analysis time, especially for dimers compared to the HPLC methods used to date.     

Kinetic dissection of individual steps in the poly(C)-directed oligoguanylate synthesis from guanosine 5'-monophosphate 2-methylimidazolide

A kinetic study of oligoguanylate synthesis on a polycytidylate template, poly(C), as a function of the concentration of the activated monomer, guanosine 5'-monophosphate 2-methylimidazolide, 2-MeImpG, is reported. Reactions were run with 0.005-0.045 M 2-MeImpG in the presence of 0.05 M poly(C) at 23 degrees C. The kinetic results are consistent with a reaction scheme (eq 1) that consists of a series of consecutive steps, each step representing the addition of one molecule of 2-MeImpG to the growing oligomer. This scheme allows the calculation of second-order rate constants for every step by analyzing the time-dependent growth of each oligomer. Computer simulations of the course of reaction based on the determined rate constants and eq 1 are in excellent agreement with the product distributions seen in the HPLC profiles. In accord with an earlier study (Fakhrai, H.; Inoue, T.; Orgel, L. E. Tetrahedron 1984, 40, 39), rate constants, ki, for the formation of the tetramer and longer oligomers up to the 16-mer were found to be independent of length and somewhat higher than k3 (formation of trimer), which in turn is much higher than k2 (formation of dimer). The ki (i > or = 4), k3, and k2 values are not true second-order rate constants but vary with monomer concentration. Mechanistic models for the dimerization (Scheme I) and elongation reactions (Scheme II) are proposed that are consistent with our results. These models take into account that the monomer associates with the template in a cooperative manner. Our kinetic analysis allowed the determination of rate constants for the elementary processes of covalent bond formation between two monomers (dimerization) and between an oligomer and a monomer (elongation) on the template. A major conclusion from our study is that bond formation between two monomer units or between a primer and a monomer is assisted by the presence of additional next-neighbor monomer units. This is consistent with recent findings with hairpin oligonucleotides (Wu, T.; Orgel, L. E. J. Am. Chem. Soc. 1992, 114, 317). Our study is the first of its kind that shows the feasibility of a thorough kinetic analysis of a template-directed oligomerization and provides a detailed mechanistic model of these reactions.     

Quantitative analysis of hindered amine light stabilizers by CZE with UV detection and quadrupole TOF mass spectrometric detection

The current work describes the development of a CZE method with quadrupole QTOF‐MS detection and UV detection for the quantitation of Cyasorb 3529, a common hindered amine light stabilizer (HALS), in polymer materials. Analysis of real polymer samples revealed that the oligomer composition of Cyasorb 3529 changes during processing, a fact hampering the development of a straightforward method for quantitation based on calibration with a Cyasorb 3529 standard. To overcome this obstacle in‐depth investigations of the oligomer composition of this HALS using QTOF‐MS and QTOF‐MS/MS had to be performed whereby 22 new oligomer structures, in addition to the ten structures already described, were identified. Finally, a CZE method for quantitative analysis of this HALS was developed starting with a comprehensive characterization of a Cyasorb 3529 standard using CZE‐QTOF‐MS, subsequently allowing the correct assignment of most Cyasorb 3529 oligomers in an electropherogram with UV detection. Employing the latter detection technique and hexamethyl‐melamine as internal standard, peak areas obtained for the melamine could be correlated with those from the triazine ring, the UV‐absorbing unit present in the HALS. This approach finally allowed proper quantitation of the single oligomers of Cyasorb 3529, an imperative for the quantitative assessment of this HALS in real polymer samples.     

Structural study of PLGA [copoly (DL-lactic/glycolic acid)], a biodegradable polymer for parenteral sustained release preparations, by tandem mass spectrometry.

A copoly (DL-lactic/glycolic acid) (PLGA), with a weight-average molecular weight of about 8400, has been characterized using fast atom bombardment (FAB)-tandem mass spectrometry in order to determine the sequence. Because of the large molecular size, PLGA was partially hydrolyzed and the terminal hydroxyl groups in the resulting oligomer mixture acetylated as the indicator. The FAB spectrum of this sample showed a complex ion signal pattern containing monomer to octamer. Diagnostic product ions containing useful information for sequence determination were observed in collision-induced dissociation-MS/MS and MS/MS/MS of these oligomer ions. The results of analysis for dimers through pentamers showed that they have random sequences of lactic and glycolic acid, suggesting that the whole structure of PLGA also has a random sequence.     

Improved capillary electrophoresis method for the determination of carbohydrate-deficient transferrin in patient sera

Capillary zone electrophoresis (CZE) with a dynamic double coating formed by charged polymeric reagents represents an effective tool for the separation of iron-saturated transferrin (Tf) isoforms and thus the determination of carbohydrate-deficient transferrin (CDT, sum of asialo-, monosialo- and disialo-Tf in relation to total Tf) in human serum. Using the CEofix-CDT reagents, a 50 microm inner diameter (ID) capillary of 60 cm total length and the P/ACE MDQ under optimized instrumental conditions (20 kV and 30 degrees C) is demonstrated to provide outstanding assay precision for the determination of CDT in human serum. For CDT levels of 1.0% and 4.5%, precision relative standard deviation (RSD) values (n = 8) were determined to be < 3.0% and < 1.5%, respectively. During the first year of operation under routine conditions, more than 600 patient samples were analyzed in a total of 62 sets of runs. Except for selected samples of patients with severe liver diseases, interference-free Tf patterns were detected. Asialo-Tf was not detected in control sera and in patient sera with a CDT level < 1.70%, but became detectable in 89.6% of sera with > 2.3% disialo-Tf. Monosialo-Tf was only detected in two sera containing > 13.3% CDT. The optimized CZE assay was applied to confirm positive CDT results produced by an immunoassay during long-term monitoring of a patient which led to the determination of the elimination kinetics of asialo-Tf, disialo-Tf, and CDT after an episode of high alcohol consumption (estimated apparent half lifes of 4.86, 7.24, and 6.74 days, respectively). The optimized CZE assay with an upper reference limit for CDT of 1.70% represents an attractive alternative to high-performance liquid chromatography (HPLC). It features simpler sample preparation, faster analysis time, and higher isoform resolution compared to the most recent HPLC approach and can thus be regarded as a new candidate of a reference method for CDT.     

毛细管区带电泳法快速测定复方布洛芬片的有效成分

 研究了用毛细管区带电泳法快速测定复方布洛芬片中布洛芬和伪麻黄碱含量的方法。在０．０２５ｍｏｌ／Ｌ的磷酸盐缓冲液（ｐＨ８．１）中，上述两组分可在３ｍｉｎ内得以完全分离，用紫外检测器在２１０ｎｍ处检测，并以外标法定量。１１次测定含有９．５ｍｇ／Ｌ盐酸伪麻黄碱和６６．７ｍｇ／Ｌ布洛芬的试样溶液，相对标准偏差为２．９％（伪麻黄碱）和１．９％（布洛芬），回收率为１０３．１％（伪麻黄碱）和９７．６％（布洛芬）。应用毛细管区带电泳法测定复方布洛芬片剂的含量，所得结果与ＨＰＬＣ法一致。     

Studies on thermoplastic polyurethanes based on new diphenylethane-derivative diols. II. Synthesis and characterization of segmented polyurethanes from HDI and MDI

Various new thermoplastic segmented polyurethanes were synthesized by a one-step melt polymerization from aliphatic-aromatic α,ω-diols containing sulfur in the aliphatic chain, including 4,4′-(ethane-1,2-diyl)bis(benzenethioethanol), 4,4′-(ethane-1,2-diyl)bis(benzenethiopropanol) and 4,4′-(ethane-1,2-diyl)bis(benzenethiodecanol) as chain extenders, hexane-1,6-diyl diisocyanate (HDI) or 4,4′-diphenylmethane diisocyanate (MDI) and 20-80 mol% poly(oxytetramethylene)diol (PTMO) with molecular weight of 1000 g/mol as a soft segment. The reaction was conducted at the molar ratio of NCO/OH = 1 and 1.05, and in the case of the HDI-based polyurethanes in the presence of dibutyltin dilaurate as a catalyst. The effect of the diisocyanate used on the structure and some physicochemical, thermal and mechanical properties of the segmented polyurethanes were studied. The structures of these polyurethanes were examined by FTIR and X-ray diffraction analysis. The thermal properties were investigated by differential scanning calorimetry and thermogravimetric analysis. Shore hardness and tensile properties were also determined. All the synthesized polymers showed partially crystalline structures. The MDI-based polyurethanes were products with lower crystallinity, higher glass-transition temperature (T_g) and better thermal stability in comparison with the HDI-based ones. The MDI series polymers also exhibited higher tensile strength (up to ∼36 MPa vs. ∼23 MPa) and elongation at break (up to ∼3900% vs. ∼900%), but lower hardness than the analogous HDI series polyurethanes. In both series of the polymers an increase in PTMO soft-segment content was associated with decreased crystallinity, T_g, hardness and tensile strength. An increase in PTMO content also involved an increase in elongation at break.     

Oligomer-oligomer versus oligomer-monomer C(2)-C(2)' coupling reactions in polypyrrole growth.

The C(2)-C(2)' coupling reactions of oligopyrrole radical-cations of increasing length generated by electrochemical oxidation have been modeled by transition state calculations. The modeling approach takes into account solvent effects and (i) shows that the coupling distance in the transition state decreases with oligomer length, (ii) demonstrates that dimerization rates in the gas phase decrease with oligomer length but increase in water, (iii) suggests that in a less solvating medium the dimerization rates could be equivalent, (iv) indicates that in all solvents quaterpyrrole and sexipyrrole formation is faster through a coupling reaction between oligomer and monomer radical-cations than two oligomer radical-cations, and (v) suggests that for the formation of a long oligopyrrole from oligopyrrole-pyrrole reactions the mechanism might involve the coupling of the oligopyrrole dication with a non-oxidized pyrrole unit instead of the coupling of two radical-cations or that of the oligopyrrole dication with a pyrrole radical-cation.     

毛细管区带电泳法快速测定复方布洛芬片的有效成分

研究了用毛细管区带电泳法快速测定复方布洛芬片中布洛芬和伪麻黄碱含量的方法。在０．０２５ｍｏｌ／Ｌ的磷酸盐缓冲液（ｐＨ８．１）中，上述两组分可在３ｍｉｎ内得以完全分离，用紫外检测器在２１０ｎｍ处检测，并以外标法定量。１１次测定含有９．５ｍｇ／Ｌ盐酸伪麻黄碱和６６．７ｍｇ／Ｌ布洛芬的试样溶液，相对标准偏差为２．９％（伪麻黄碱）和１．９％（布洛芬），回收率为１０３．１％（伪麻黄碱）和９７．６％（布洛芬）。应用毛细管区带电泳法测定复方布洛芬片剂的含量，所得结果与ＨＰＬＣ法一致。     

Electrochemiluminescent Determination of Methamphetatiime

Methamphetamine (MAPA) is a kind of anesthesia, which determination is paid more attention to recently. MAPA has been determined by GC, GC-MS, polarization fluoroimmunometry,HPLC and capillary zone electrophoresis (CZE)^[1] and so on. There is still a need for rapid, inexpensive but sensitive methods for the determination of drugs.     

Determination of nonsteroidal anti-inflammatory drugs in human specimens by capillary zone electrophoresis and micellar electrokinetic chromatography

Therapeutic drug monitoring of anti-inflammatory drugs is necessary for the identification of the agents that cause toxic events and for the decision on the treatment for intoxication. Recently, capillary electrophoresis (CE) has been developed for the simple and rapid analyses of a variety of chemical agents. Micellar electrokinetic chromatography (MEKC) can separate acidic, neutral and basic anti-inflammatory drugs in serum. Furthermore, serum samples are directly applied to the CE system without any pretreatments, and some anti-inflammatory drugs can be separated from serum albumin in the MEKC analysis. On the other hand, capillary zone electrophoresis (CZE) enables us to determine a few microg/mL levels of acidic anti-inflammatory drugs with simple running buffer and stacking technique. A rapid and simultaneous determination of several analgesic anti-inflammatory agents, including ibuprofen, acetaminophen, indomethacin, and salicylic acid in human serum has been developed by using CZE. Therefore, the CZE and MEKC analysis may become a potentially useful alternative to high-performance liquid chromatography (HPLC) and fluorescence polarization immunoassay (FPIA) for therapeutic drug monitoring, particularly in serum of patients suffering from intoxication by overdosage of nonsteroidal anti-inflammatory agents.     

Enhanced methylation rate within a foldable molecular receptor

A N,N-(dimethylamino)pyridine monomer is incorporated into the backbone of a m-phenyleneethynylene oligomer such that the pyridine nitrogen is located on the interior surface of the binding cavity in the folded structure of the oligomer. For an oligomer having a chain length of 13 monomer units, competitive inhibition experiments reveal that methyl iodide binds weakly within the oligomer cavity with an association constant K(a) = 2 M(-1), and the oligomer-methyl iodide complex reacts with unimolecular rate constant k(u) = 0.082 s(-1) to provide the methylated product. The effective molarity is calculated to be 230 M by comparison of k(u) for the 13-mer with the second-order rate constant for a 3-mer that is too short to fold and thus unable to bind methyl iodide.     

Use of capillary electrophoresis in drug quality assessment of synthetic porcine secretin

The purity profile for porcine secretin attributable to contamination by equilibrium products such as aspartoyl(3) secretin has been shown to be dependent on the pH of the analytical system. Capillary zone electrophoresis (CZE) methods have been developed for the efficient separation of synthetic porcine secretin, its equilibrium products and other impurities in aqueous solutions at both acidic and alkaline pH. These conditions are more representative of those used for the reconstitution and administration of porcine secretin, and good results cannot be achieved using HPLC due to poor peak shape above pH 5.8. The influence of various CZE operational parameters was systematically examined. The methods were validated for accuracy, precision, linearity, LOD and LOQ. A comparative evaluation of the stability of test solutions was determined using CZE and HPLC over a range of pH values. HPLC and CZE methods produced similar results at low pH.