Determination of Polychlorinated Biphenyls and Chlorinated Pesticides in Environmental Biological Samples Using Focused Microwave-assisted Extraction

Abstract

Organochlorine compounds such as polychlorinated biphenyls (PCBs) and chlorinated pesticides have been analysed in environmental biological samples using focused microwave-assisted extraction (FMW). The analytical procedure is presented and the results for two Standard Reference Materials, a cod liver oil and a freeze-dried mussel tissue, are reported. The average recoveries for the sum of the PCBs are between 93% and 106%, and for the sum of the chlorinated pesticides are between 109 to 115% for all the certified compounds analysed. The developped analytical procedure is highly reproducible with an average standard deviation of 8% for the sum of the PCBs and 9.7% for the sum of the chlorinated pesticides in the two matrices.     

Analysis of Polychlorinated Biphenyl Mixtures and Establishment of a Parameter Useful for PCB‐Degradation Studies

Abstract

A prerequisite for the study of polychlorinated biphenyls (PCBs) is a reliable analytical determination of the substances involved. For this purpose a gas chromatographic (GC) separation method with detection by mass spectrometry (MS) was optimized. In addition, a new parameter—the “weighted average chlorination level”—was established. This forms the basis for a systematic investigation of the reductive dechlorination of PCBs by metals.     

Synthesis of New Benzoxaphosphole Derivatives from the Reaction of Dialkylphosphonates and Trisdialkylaminophosphines with 2,6-Bis(benzylidene)cyclohexanones

The reaction of 2,6-bis(benzylidene)cyclohexanones with dialkylphosphonates and tris(dialkylamino)phosphines afforded the new benzoxaphosphole derivatives (5a–5d) and (9a–9f). The biological activity of the newly synthesized compounds was also examined. Possible reaction mechanisms are considered, and the structural assignments are based on analytical and spectroscopic results. The structure of the new benzoxaphosphole 5a was confirmed by a single crystal X-ray determination.     

Reaction of 2-Thioxo-4-Thiazolidinones Toward Lawesson's Reagent,Phosphorus Pentasulfide,Dialkylaminophosphines, and Phosphorus Ylides

Abstract

2-Thioxo—3-allyl-4-thiazolidinone 1a reacts with Lawesson's reagent (LR, 2) to give the ethylenic product 5 through a coupling reaction along with the dithioxo compound 6. Coupling reaction products of types 8 and 9 are also produced upon reacting thiazolidinones 1 and with the appropriate tris(diallkylamino) phosphine reagent (3 a,b). Reaction of the thiazolidinone 1a with the ylidenetriphenylphosphorane reagents 4 a–c proceeds according to the Wittig mechanism yielding ethylenes 10a–c, respectively. Structural elucidations for the new products were based upon compatible analytical and spectroscopic measurements as well a confirmatory single crystal X-ray structure for 5.

Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the related elements to view the free supplemental file.     

Determination of Aluminium with 8-Hydroxyquinoline-5-Sulfonic Acid in Presence of A Cationic Surfactant by First and Second Derivative Synchronous Fluorimetry

Abstract

An analytical method has been developed for the fluorimetric determination of nanogram amounts of aluminium in solution. The method is based on the reaction of aluminium with B-hydroxyquinoli-ne-5-sulfonic acid in presence of hexadeciltrimethylammonium bromide as a surfactant agent. Synchronous scanned first and second derivative fluorimetry has been employed to increase the sensitivity of the method. The influence of reaction variables as well as instrumental parameters is discussed. The interference of various foreign ions has also been examined and in some cases eliminated or reduced by addition of 1, 10-phenanthroline.     

Preparation of Calix[4]arene Alkylamine Derivatives by Mannich Reaction and use as Phase-Transfer Catalysts for Esterification Reaction

In this study, 5,11,17,23-tetrakis[(N-ethylpiperazine)methyl]-25,26,27,28-tetrahydroxycalix[4]arene (3) and 5,11,17,23-tetrakis[(4-carboethoxy-N-piperidino) methyl]-25,26,27,28-tetrahydroxycalix[4]arene (4) were synthesized in one step according to the Mannich reaction by the treatment of calix[4]arene with a secondary amine (N-ethylpiperazine, ethyl-4-piperidincarboxylate) and formaldehyde. The calix[4]arene derivatives (3, 4) were characterized by a combination of FTIR, ¹H NMR and elemental analyses. The synthesized compounds were used in an esterification reaction as the phase transfer catalyst. The catalytic efficiency of the calix[4]arenes 3 and 4 was evaluated by carrying out the ester-forming reaction of alkali metal carboxylates (sodium butyrate or sodium caprylate) with p-nitrobenzyl bromide. It was observed that the ester-forming reaction of alkali metal carboxylates with p-nitrobenzyl bromide, using calix[4]arene-based catalyst 3 as a phase-transfer catalyst in dichloromethan, provided the best yields.     

On the Redox Reaction of 1,2-Bis(diphenylphosphino) Alkanes Toward o-, and p-Quinones

Abstract

The reaction of 1,2-bis(diphenylphosphino)ethane with substituted o-benzo-quinones afforded new bis(6-hydroxycyclohexa-2,4-dienone) derivatives. Treatment of the same reagent with o-naphthoquinone, phenanthrenequinone, and acenaphthenequinone gave the respective bis(diphenylphosphoryl)ethylidenes or diacenaphthylenone derivatives. On the other hand, p-quinones react with 1,2-bis(diphenylphosphino)methane to yield the corresponding 4-hydroxycyclohexa-2,5-dien-1-ones. Possible reaction mechanisms are considered and the structural assignments are based on compatible analytical and spectroscopic data.     

Application of Novel Glycosides Prepared with Odorless Benzenethiols in Glycosylation Reaction

p‐Dodecylbenzenethiol (1) and p‐octyloxybenzenethiol (2) were synthesized as new odorless benzenethiols. Moreover, preparation of novel 1‐thioglycosides using 1 and 2 as well as their application for glycosylation reactions was performed. As a result, it was found that these 1‐thio‐glycosides were excellent glycosyl donors, and especially 2‐thio‐sialoside prepared from 1 and 2 afforded the best result to date in terms of α‐ and β‐selectivity in the sialylation where only the single C‐3 hydroxyl group of acceptor D‐galactopyranoside was free. All procedures from the preparation of thioglycosides to glycosylation reaction were attainable under completely odorless conditions.     

Molecular Shape Analysis of a Maillard Reaction Intermediate

Abstract

The Maillard (browning) reaction involving the polycondensation of sugars and amino acids is believed to be an important abiotic pathway for humic substance formation in nature. However, a major drawback is that the Maillard reaction is extremely slow at temperatures encountered under normal environmental conditions. In order to elucidate some details of this process molecular shape analysis was applied to investigate the initial reaction between D-glucose and glycine to form the Amadori compound fructosylglycine which is an intermediate product in the Maillard reaction. The structure of the Amadori compound was optimized at a quantum mechanical level and its ground state electron energy calculated. Molecular Iso-Density Contours (MIDCO's), electron density contour surfaces of constant electron density, were constructed for D-glucose, glycine and fructosylglycine in order to study the steric conditions for the reaction. The calculations indicate that the Amadori compound and water on one hand and the separate entities D-glucose and glycine on the other hand are very similiar to each other in terms of their ground state energy. This agrees with the experimental observation that the reaction between D-glucose and glycine to form the Amadori compound is slow.     

Reaction of ruthenacarborane with trifluoroacetoxymercuroferracarborane

The reaction of exo-nido-ruthenacarborane exo-nido-5,6,10-[Cl(Ph₃P)₂Ru]-5,6,10-(-H)₃-10-H-7,8-C₂B₉H₈ (1) with the 8-trifluoroacetoxymercury derivative of ferracarborane 3-(⁵-Cp)-4-SMe₂-8-CF₃COOHg-3,1,2-FeC₂B₉H₉ (2) was studied. It was demonstrated for the first time that metallacarborane 2 can be used as a mercurating agent. The reaction afforded 5",6",10"-exo-nido-[Cl(Ph₃P)₂Ru]-5",6",10"-(-H)₃-10"-{3-(⁵-Cp)-4-SMe₂-3,1,2-FeC₂B₉H₉-8-Hg}-7",8"-C₂B₉H₈ (3) existing as two isomers. The structure of trans isomer 3a was established by X-ray diffraction analysis.     

Kinetic Method for the Determination of α‐Methyldopa in Pharmaceutical Preparations: Analytical Procedure and Reaction Mechanism Considerations

Abstract

A reliable and very simple kinetic method is proposed for the determination of α‐methyldopa in pharmaceutical preparations. It is based of the oxidation of α‐methyldopa, a catechol derivative, to quinone, by the ferric ion in the presence of salicylic acid and HCl. The deep blue complex formed between iron(III) and salicylate (λ_max 525 nm) allows the reaction to be watched as absorbance decreases with the reduction of the ferric ions to ferrous with the consequent dissociation of the complex. Four pharmaceutical preparations were analyzed and the results were compared with those obtained with the spectrophotometric United States Pharmacopeia method. The statistical t‐Student and the F‐tests were applied to compare the results obtained with the two independent methods. In all cases complete agreement, in terms of accuracy and precision, was observed with a confidence level of 95% (α=0.05). Considering the four samples analyzed, using the proposed method, and five determinations for each sample, the observed mean relative standard deviation (RSD) is about 0.8%. The concentration range studied was from about 2×10^?4 mol L^?1 to 18×10^?4 mol L^?1 (about 40 µg/mL to 360 µg/mL) in the final solution and it is quite adequate for the analytical procedure at 25.0±0.1°C. A typical coefficient of determination, r², of the calibration curve, is 0.9994. For the kinetic pseudo first order curves a typical observed r² is 0.99998. The Arrhenius activation energy was found to be 84.2±3.4 kJ mol^?1. A schematic mechanism of the reaction is proposed.     

Studies on Organophosphorus Compounds XI: The Reaction of Phosphorus Reagents With Hydrazonoyl Halides,Hydrazonoyl Azides,and Shiff's Bases

N-(chloro-furan-2-yl)methylene-N′-(4-nitrophenyl)hydrazone (I) reacted with triethylphosphite to produce the phosphonate derivative III. The tetrazine derivative VI was produced by the interaction of I with diethyl-phosphite. Hydrazonoyl azide derivatives VIIIa–c reacted with triphenyl phosphine to form the iminophosphorane derivatives Xa–c. On the other hand, the azide derivative VIIIc reacted with the phosphonium ylide XI to form the 1,2,3-triazole adduct XIII. The reaction of triethyl phosphite with Shiff's bases XIVa–c yielded the corresponding phosphonates XVa–c. The structures of the newly prepared compounds were confirmed with the analytical and spectroscopic evidences.     

Reaction of Orthometallated Perfluorocumyl Alkoxides with Sulfinyl Derivatives: Synthetic and Mechanistic Aspects

Abstract

The reaction of 1,1,1,3,3,3-hexafluoro-2-(p-tert-butyl)phenyl-2-propanol with n-butyl-lithium/N,N,N′,N′-tetramethylethylenediamine (TMEDA) provides dilithioderivative 1b, which, upon reaction with thionyl chloride, gave cyclic and acyclic sulfites 3 and 4 as precursors of the sulfurane 2b with simultaneous formation of cyclic sulfinate 5. This ester was utilized for the preparation of asymmetrical spirosulfuranes 7 or ortho-perfluorocumylaryl(alkyl) sulfoxides 8. Attempts to obtain it as an optically active species are also mentioned.     

Potentiometric Titration of Trace Concentrations of Penicillamine Using Ion Selective Electrodes

Abstract

Penicillamine (PA) has shown promise as a therapeutic agent in the treatment of rheumatoid arthritis (RA), and a sensitive analytical procedure applicable to physiological fluids is needed. PA is a metal chelating agent which forms very strong complexes with heavy metal ions (e.g., Hg²⁺, Cu²⁺, Pb²⁺). This characteristic has been applied to the analytical problem presented. The method developed is based on potentiometric titration of the ligand with a metal ion solution utilizing for endpoint detection an indicator electrode selective for this metal ion. The procedure described used lead (II) as the titrant and a lead (II) selective electrode. Demonstrated precision was ±2.0% when 7.5 μg PA was determined in 50 ml solution.     

Reaction of Dimethyl Acetylenedicarboxylate With 2-Mercaptoperimidine and 2-Mercaptobenzimidazole

A mixture of equimolar quantities of dimethyl acetylenedicarboxylate ( 2 ) with either 2-mercaptoperimidine ( 1 ) or 2-mercaptobenzimidazole ( 5 ) was heated in absolute benzene in the presence of triphenylphosphine as a catalyst under reflux conditions for 1 h (the reaction was monitored by TLC until the consumption of the starting materials). The solvent was concentrated under vacuum and the residue was subjected to chromatographic plates using toluene-ethylacetate (2:1) as an eluent. The products in each reaction were separated as two migrating zones. Each zone was removed from the plate and recrystallized from the appropriate solvent. The products of the first reaction are 10-methoxy-11-oxo-11H-8-thia-7,11a-diaza-benzo[de]anthracene-9-carboxylic acid methyl ester ( 3 ) and 8-thia-7,10a-diaza-cyclopenta[a]phenalene-9,10-dicarboxylic acid dimethyl ester ( 4 ), while the products of the second reaction are 3-methoxy-4-oxo-4H-1-thia-4a,9-diaza-fluorene-2-carboxylic acid methyl ester ( 10 ) and benzo[4, 5]imidazo[2,1-b]thiazole-2,3-dicarboxylic acid dimethyl ester ( 11 ). The mechanisms of the observed reactions are suggested.     

Monitoring of Polychlorinated Biphenyls in Surface Water Using Liquid Extraction,GC/MS,and GC/ECD

Abstract

A rapid and reliable analytical method, at trace level concentration was developed and validated for monitoring polychlorinated biphenyls (PCBs) in Jordanian surface water. The method combines the advantage of liquid extraction together with gas chromatography‐mass spectrometry (GC/MS) and gas chromatography‐electron capture detector (GC/ECD). The performance of the method was evaluated by analyzing certified reference material (CRM) of the analytes and applied on real water samples collected from different sites in Jordan. A mixture of 60∶40 dichloromethan‐petroleum ether was chosen as a convenient binary solvent for liquid–liquid extraction. The GC conditions for GC/MS were optimized using He as a carrier gas, temperature programming, and chlorpropham as an internal standard (IS).

The conditions for GC/ECD were performed using N₂ gas and a temperature program from 160 to 280°C with different increasing rates. The method of GC/MS in the selective ion mode (SIM) gave linear relationships for all PCBs tested between 0.60–6.0 µg/l with R ²=0.9934 (n=7×18). Recoveries from spiked water samples ranged between 87.6 and 91.4%. The mean accuracy and precision obtained were 4.9% and 2.16%, respectively. The mean of detection limit was 0.14±0.04 µg/l. In GC/ECD, linear relationships for all PCBs examined over the range of 0.3–2.4 µg/l was verified as characterized by a linear regression equation and correlation coefficient, R ²=0.9915 (n=12). The average precision and accuracy were 4.86% and 5.21%, respectively. Analyses results clarified that none of the examined Jordanian water samples contained any of the searched for PCBs within the detection limit achieved.     

Phosphanyl Ureas as Ligands for Ethylene Oligomerization: A Cascade Reaction

The phosphanyl urea ligands MeNHC(O)NMePR ₂ ( 1 : R = Ph and 2 : R = 2,4-tBu ₂ C ₆ H ₃ O) form effective ethylene oligomerization catalysts with [Ni(cod) ₂ ] (cod = 1,5 cyclooctadiene). Whereas the primary product with 1 is butene, 2 initiates a cascade reaction leading to hexenes and octenes. In the first reaction cycle ethylene is dimerized to butene, which serves as feedstock for the second dimerization cycle to the final products hexenes and octenes.     

CH3S与HCS双自由基反应的密度泛函理论研究

应用量子化学从头算和密度泛函理论(DFT)对CH₃S与HCS双自由基单重态反应进行了研究. 在MPW1PW91/ 6-311G(d,p)水平上优化了反应通道上各驻点(反应物、中间体、过渡态和产物)的几何构型, 用内禀反应坐标(IRC)计算和频率分析方法对过渡态进行了验证. 在QCISD(t)/6-311＋＋G(d,p)水平上计算各物种的单点能, 并对总能量进行了零点能校正. 研究结果表明, CH₃S与HCS反应为多通道反应, 有4条可能的反应通道, 反应物首先通过S…S弱相互作用形成具有竞争反应机理的五元环硫-硫偶合中间体a和链状硫-硫偶合中间体c, 再由此经过氢迁移、离解、异构化等不同机理得到主要产物P1 (2CH₂S), 次要产物P2 (CH₃SH＋CS), P3 (CH₄＋CS₂)和P4 [CH₂(SH)CSH]. 根据势能面分析, 所有反应均为放热反应, 生成P1的反应热为－165.55 kJ•mol^－1. 通道R→a→TSa/b→b→P1为标题反应的主通道, 其速控步骤a→TSa/b→b在200～2000 K温度区间内的速率常数可以表示为k₁^CVT/SCT＝1.75×10¹⁰T^0.65exp(－907.6/T) s^－1. P3及P4的生成需要越过很高的活化能垒, 是动力学禁阻步骤, 但在反应体系中加入合适催化剂, 改变其反应机理, 有可能使生成CH₂(SH)CSH, CH₄及CS₂的反应易于进行.     

The Reaction of Benzothiazolesulfenamide with Phospiiorus-Containing Reagents

Abstract

T. Sigeru reported the reaction of 2-benzothiazolesulfen-amide with phosphites, but other P-reagents have not been used.

we found that this compound can react with tris(dialkylamino)phosphines or bis(dialkylamino)phosphites to give products (I). No S-N bond cleavage was observed in the reaction performed as described by T. Sigeru. In the presence of subetituent in amino group, the reaction proceeds differently.     

Bioaccumulative Behaviour of Some PCB Congeners in Lake Geneva Brown Trout (Salmo trutta lacustris L)

Abstract

The bioaccumulation of PCBs has been studied for 60 Brown trout in Lake Geneva (Switzerland). The contamination level (1–3 ppm in wet weight, 10–30 ppm in lipid weight) is rather high.

Bioaccumulation curves (concentration as a function of the weight of the fish) have been established for 6 congeners and total PCBs. The total concentration of PCBs in wet weight increased with the weight of the fish; highly-chlorinated congeners (I.U.P.A.C. nr. 180, 2,3,4,5,2′,4′,5′-heptachlorobiphenyl) presented a faster, and lightly-chlorinated (I.U.P.A.C. nr. 28, 2,4,4′-trichlorobiphenyl) a slower, bioaccumulation tendency.

The total concentration of PCBs in lipid weight was constant, the concentration of congener 28 increasing and of congener 180 decreasing with the weight of the fish. This is attributed to the antagonistic effects of “growth and lipid dilution” and of the decrease of elimination kinetics as a function of the weight (and age) of the fish.

The partitioning theory and the pharmacokinetic approach are complementary methods for analysing this field data.