Gas chromatographic separation of PCB and OCP by photocatalytic degradation

A photocatalytic degradation method was developed for polychlorobiphenyl (PCB) and organochloride pesticide (OCP) discrimination and quantification. A mixture of Aroclor 1260 and p,p′-DDT was irradiated at 254 nm by UV lamp (40 W) in the presence of TiO₂ (30 mg mL⁻¹ non-aqueous solution). Comparison of gas chromatograms showed that p,p′-DDT signals decreased significantly after irradiation, while Aroclor 1260s chromatograms did not show any difference before and after irradiation. Detection limits were 0.30 mg L⁻¹ and 0.15 mg L⁻¹ for p,p′-DDT and Aroclor 1260, respectively. The method was applied to spiked egg samples, the recoveries were found as 72% for DDT and 82.01% for Aroclor 1260.     

Sequential solid-phase extraction with cyanopropyl bonded-phase cartridges for trace enrichment of PCBs and chlorinated pesticides from water samples

Summary Gas chromatography of polychlorinated biphenyls and chlorinated pesticides in water samples has been performed after adsorption from a 50–250 mL sample on to a cartridge containing 100 mg cyanopropyl-bonded porous silica. The PCBs are desorbed with 500 μL ethyl acetate, which is concentrated and analysed by gas chromatography with electron-capture detection (GC-ECD). The average recovery of 1 ppb PCB congeners at from distilled water and from Marta river water is ≥95% (standard deviation ≤2.5). The average recovery of 20 ppb Aroclor 1260 from Marta river water was ≥91% (standard deviation ≤3.5). In the separation of the PCBs from the chlorinated pesticides only aldrin, heptachlor and 4,4′-DDD are adsorbed with the PCBs by the CN Sep-Pak cartridge. The method proposed is rapid, simple and reproducible.     

Catalytic dechlorination of Aroclor 1242 by Ni/Fe bimetallic nanoparticles

Ni/Fe bimetallic nanoparticles were synthesized for treatment of Aroclor 1242, in order to evaluate their applicability for in situ remediation of groundwater and soil contaminated by polychlorinated biphenyls (PCBs). Our experimental results indicate that the total PCB concentration changed during the reduction of 3,5-dichlorobiphenyl (PCB 14), and biphenyl was produced as the final product. Initially, the concentration of 3-chlorobiphenyl (PCB 2) was increased in the prophase reaction and then slowly decreased, suggesting that Aroclor 1242 was first adsorbed by Ni/Fe nanoparticles, and then, the higher chlorinated congeners were converted gradually to the lower chlorinated congeners, and finally to biphenyl. The dechlorination efficiency of Aroclor 1242 reached approximately 80% at 25°C in just 5h, then 95.6% and 95.8% in 10h and 24h, respectively. The study revealed that high Ni/Fe nanoparticle dosage and high Ni content in Ni/Fe nanoparticles favor the catalytic dechlorination reaction. Moreover, a comparison of different types of catalysts on the dechlorination of Aroclor 1242 indicated that Ni/Mg and Mg powders showed a greater reactivity than Ni/Fe and Fe nanoparticles, respectively.     

Radioimmunoassay of PCBs in Milk and Blood

A radioimmunoassay was developed capable of determining Aroclor 1260 in milk at levels of from 20 to 80 ppb and in blood from 2 to 16 ppb. The values obtained by radioimmunoassay correlate well with those determined by gas-liquid chromatography (r² = 0.96 for milk and 0.99 for blood) but were lower. Antiserum was produced in rabbits and was specific for 2, 2′, 4, 4′, 5, 5′-hexachlorobiphenyl. It cross-reacted with congeners and isomers in Aroclor 1254 and 1260 to the extent that a 20% decrease in binding was observed with 0.1 ng of either mixture. The method requires preliminary cleanup of the extract on alumina and utilizes 25 % dimethyl sulfoxide in the assay medium to promote solubilization of the substrates.     

Improvements in glass capillary gas chromatographic polychlorobiphenyl analysis

Separation of a 1:1:1:1 calibration mixture of Aroclors 1221, 1016, 1254, and 1260 on soda glass capillaries coated with Apolane (C-87) or Apiezon L is described. Polychlorobiphenyl congener structures are assigned to 112 separated and partially separated zones. The quantitative composition of Aroclor 1221 is reported. The performance of the two stationary phases on different lengths of laboratory and commercially prepared capillaries is compared and found to be very similar. Aroclors 1221, 1016, 1254, and 1260 are employed (1:1:1:1) for the primary calibration mixture because they contain all components of the commercial materials which pollute the environment; they are also easily obtained from the U.S. EPA Repository so that the method can be used in any laboratory by employing the calibration data given here.     

Radioimmunoassay of PCBs in milk and blood

A radioimmunoassay was developed capable of determining Aroclor 1260 in milk at levels of from 20 to 80 ppb and in blood from 2 to 16 ppb. The values obtained by radioimmunoassay correlate well with those determined by gas-liquid chromatography (r2 = 0.96 for milk and 0.99 for blood) but were lower. Antiserum was produced in rabbits and was specific for 2,2',4,4',5,5'-hexachlorobiphenyl. It cross-reacted with congeners and isomers in Aroclor 1254 and 1260 to the extent that a 20% decrease in binding was observed with 0.1 ng of either mixture. The method requires preliminary cleanup of the extract on alumina and utilizes 25% dimethyl sulfoxide in the assay medium to promote solubilization of the substrates.     

Determination of Aroclor 1260 in soil samples by gas chromatography with mass spectrometry and solid‐phase microextraction

A novel fast screening method was developed for the determination of polychlorinated biphenyls that are constituents of the commercial mixture, Aroclor 1260, in soil matrices by gas chromatography with mass spectrometry combined with solid‐phase microextraction. Nonequilibrium headspace solid‐phase microextraction with a 100 μm polydimethylsiloxane fiber was used to extract polychlorinated biphenyls from 0.5 g of soil matrix. The use of 2 mL of saturated potassium dichromate in 6 M sulfuric acid solution improved the reproducibility of the extractions and the mass transfer of the polychlorinated biphenyls from the soil matrix to the microextraction fiber via the headspace. The extraction time was 30 min at 100°C. The percent recoveries, which were evaluated using an Aroclor 1260 standard and liquid injection, were within the range of 54.9–65.7%. Two‐way extracted ion chromatogram data were used to construct calibration curves. The relative error was <±15% and the relative standard deviation was <15%, which are respective measures of the accuracy and precision. The method was validated with certified soil samples and the predicted concentrations for Aroclor 1260 agreed with the certified values. The method was demonstrated to be linear from 10 to 1000 ng/g for Aroclor 1260 in dry soil.     

Simultaneous supercritical-fluid extraction of nine individual aliphatic hydrocarbons, aroclor 1260, aroclor 5460 and four PCB congeners from chicken liver

Summary Supercritical carbon dioxide fluid extraction (SFE) has been used for selective extraction of nine aliphatic hydrocarbons, Aroclor 1260, Aroclor 5460, and four PCB congeners from chicken liver. Alumina was used as adsorbent and methanol as modifier. Recoveries were between 53 and 100% for aliphatic hydrocarbons, 83 and 95% for Aroclor 1260 and Aroclor 5460, and 81 and 98% for PCB congeners.     

Determinations of polychlorinated biphenyl isomers by response factor calibration

Quantitative measurement of polychlorinated biphenyl (PCB) isomers by response factor calibration (RFC) is evaluated with gas chromatography and the Hall electrolytic conductivity detector. The procedure requires neither isomer identification nor reference compounds identical to each measured PCB isomer. Weight percent chlorine is determined for five Aroclor mixtures by RFC and compared within a few percent of expected values. Individual PCB isomers are measured and quantitatively compared for Aroclor mixtures. Also, RFC determinations for ten PCB isomers contained in a test material reference solution are compared to the supplier's stated concentrations. These RFC measurements provide quantitative analyses in the absence of a standard for each measured component.     

Determination of 26 polychlorinated biphenyls congeners in soil samples using microwave-assisted extraction with open vessel and gas chromatography

A procedure focused on microwave-assisted extraction in open vessel (MAE-OV) and gas chromatography with electron capture detection (GC-ECD) was used for the determination of 26 congeners of polychlorinated biphenyls (PCBs) in soil samples. The limit of detection (LOD) and limit of quantification (LOQ) were evaluated for commercial PCBs mixture Aroclor1260. LOD and LOQ were calculated for each PCB congener, in the ranges (0.03–0.27?ng?g^?1) and (0.11–0.70?ng?g^?1), respectively. After optimization, 26 PCBs congeners were successfully extracted from soil samples with recovery amounts ranging between 84.7% and 117.3% for all PCBs congeners. The evaluated method of MAE-OV showed good separation and extraction of all PCBs congeners from soil samples. Extraction parameters such as solvent choice, power and extraction time were investigated. This study indicated that MAE-OV could be an interesting alternative method to extract PCBs from soils, since it is economical, easy, fast and requires low amounts of solvents.     

Ratios of PCB 138, PCB 163, and PCB 164 in aroclor mixtures

The gas chromatographic separation of PCB 138, PCB 163, and PCB 164 in Aroclor mixtures can be achieved by application of a CP-Select for PCBs stationary phase. In technical PCB mixtures with a degree of chlorination exceeding 40% (Aroclor 1242, 1254, 1260, and 1262) these three hexa-chlorobiphenyls were present. The highest concentrations of the PCBs under investigation were found in Aroclor 1260. The ratio PCB 163: PCB 138 increased with an increasing degree of chlorination of technical PCB mixtures.     

A colorimetric chemodosimeter for Pd(II): a method for detecting residual palladium in cross-coupling reactions

A colorimetric chemodosimeter (SQ1) for the detection of trace palladium salts in cross-coupling reactions mediated by palladium is described. Decolorization of SQ1 is affected by nucleophilic attack of ethanethiol in basic DMSO solutions. Thiol addition is determined to have an equilibrium constant (K_eq) of 2.9×10⁶ M⁻¹, with a large entropic and modest enthalpic driving force. This unusual result is attributed to solvent effects arising from a strong coordinative interaction between DMSO and the parent squaraine. Palladium detection is achieved through thiol scavenging from the SQ1-ethanethiol complex leading to a color ‘turn-on’ of the parent squaraine. It was found that untreated samples obtained directly from Suzuki couplings showed no response to the assay. However, treatment of the samples with aqueous nitric acid generates a uniform Pd(NO₃)₂ species, which gives an appropriate response. ‘Naked-eye’ detection of Pd(NO₃)₂ was estimated to be as low as 0.5 ppm in solution and instrument-based detection was tested as low as 100 ppb. The average error over the working range of the assay was determined to be 7%.     

Characterization of three Aroclor mixtures using a new cyanobiphenyl stationary phase

The retention characteristics of all 209 polychlorinated biphenyl (PCB) congeners were determined on a new p,p-cyanobiphenyl stationary phase using gas chromatography with electron capture detection (GC-ECD). Response factors were determined relative to decachlorobiphenyl, PCB 209. Several congeners that coelute on the phases routinely used for PCB analysis are separated on this phase, including the hexachlorobiphenyls 138, 163, and 164. The p,p-cyanobiphenyl stationary phase exhibits altered retention for planar congeners, such that the toxic coplanar PCBs 77, 126, and 169 are eluted free from interference. Of the 209 congeners, 61 were separated using the p,p-cyanobiphenyl phase in conjunction with GC-ECD. When analyzed by gas chromatography with mass selective detection (GC-MSD), the number of congeners determined increased to 133. Therefore GC-MSD was used with the p,p-cyanobiphenyl phase to characterize three PCB mixtures: Aroclor 1242, Aroclor 1254, and Aroclor 1260.     

Dechlorination of DDT, DDD and DDE in soil (slurry) phase using magnesium/palladium system

Mg0/Pd4+ was able to dechlorinate >99% of extractable DDT (initial concentration of 10 mg DDT kg(-1) of soil) and >90% of extractable DDT (initial concentration of 50 mg DDT kg(-1) of soil) in soil slurry. Mg0/Pd4+ was also found to be effective in dechlorinating of 50 mg kg(-1) DDD and DDE, in soil aged for varying time periods. GC-MS analyses revealed the formation of 1,1-diphenylethane as an end product from DDT, DDE and DDD. To the best of our knowledge this is the first report describing the application Mg0/Pd4+ system for remediation of DDT, DDD and DDE contaminated soil. We conclude that reductive dechlorination reaction catalyzed by Mg0/Pd4+ may be a promising system to remediate soil contaminated with DDT and its dechlorinated products such as DDD and DDE.     

A novel method for the determination of a PCB sum value by enzyme immunoassay to overcome the cross-reactivity problem

Many attempts have been made to detect polychlorinated biphenyls (PCBs) by enzyme immunoassay (ELISA). All known ELISAs to PCBs show characteristic cross-reactivity problems. Without any prior information about the composition of the sample, no quantification of the total PCB content is possible. A chemical approach is shown to solve the cross-reactivity problem by the quantitative dechlorination of all PCB congeners to the single compound biphenyl. For the reductive dechlorination palladium on barium sulfate and ammonium formate were used. The dechlorination procedure was optimized to be performed at room temperature in methanol without the exclusion of oxygen or water. For the development of polyclonal biphenyl-antibodies the synthesis of the hapten biphenylhexanoic acid via Grignard cross-coupling is described and an immunization protocol is given. The purity of the used immunological reagents proved to be very crucial. The whole procedure was tested with spiked soil samples. The detection limit for PCBs (Clophen A50) in soil was 1 mg/kg (3.1 μmol/kg). This corresponds to a biphenyl concentration in methanol of 0.1 mg/L (0.6 μmol/L). Received: 25 September 1998 / Revised: 1 December 1998 / Accepted: 4 December 1998     

Extractants for Organochlorine Insecticides and Polychlorinated Biphenyls from Water

A reversed liquid-liquid partition system prepared from Chromosorb W, n-undecane and Carbowax 4000 monostearate was shown to be suitable for extracting organochlorine insecticides and polychlorinated biphenyls (PCBs) from water (with the exception of Aroclor 1260). The performances of the partition system, Amberlite XAD-4, porous poly- urethane foam and the solvent extraction technique when applied to the analysis of four environmental water samples were comparable (except for Aroclor 1260).     

Determination of two oxy-pyrimidine metabolites of diazinon in urine by gas chromatography/mass selective detection and liquid chromatography/electrospray ionization/mass spectrometry/mass spectrometry

An analytical method was developed for the determination in urine of 2 metabolites of diazinon: 6-methyl-2-(1-methylethyl)-4(1H)-pyrimidinone (G-27550) and 2-(1-hydroxy-1-methylethyl)-6-methyl-4(1H)-pyrimidinone (GS-31144). Two of the urine sample preparation procedures presented rely on gas chromatography/mass selective detection (GC/MSD) in the selected ion monitoring mode for determination of G-27550. For fast sample preparation and a limit of quantitation (LOQ) of 1.0 ppb, urine samples were purified by using ENV+ solid-phase extraction (SPE) columns. For analyte confirmation at an LOQ of 0.50 ppb, classical liquid/liquid partitioning was used before further purification in a silica SPE column. An SPE sample preparation procedure and liquid chromatography/electrospray ionization/mass spectrometry/mass spectrometry (LC/ESI/MS/MS) were used for both G-27550 and GS-31144. The limit of detection was 0.01 ng for G-27550 with GC/MSD, and 0.016 ng when LC/ESI/MS/MS was used for both G-27550 and GS-31144. The LOQ was 0.50 ppb for G-27550 when GC/MSD and the partitioning/SPE sample preparation procedure were used, and 1.0 ppb for the SPE only sample preparation procedure. The LOQ was 1.0 ppb for both analytes when LC/ESI/MS/MS was used.     

Development of a quantification methodology for polychlorinated biphenyls by using Kanechlor products as the secondary reference standard

Kanechlor (KC)-300, 400, 500 and 600, Japanese polychlorinated biphenyl (PCB) products, and their equivalent mixture were analyzed by using a gas chromatograph (GC) equipped with an SE-54 capillary column/electron capture detector (ECD) and a GC/mass spectrometer in the selected ion monitoring mode (MS-SIM). All peaks were assigned to the composing congeners based on the data on peak assignment of Clophen A-30, 40, 50, 60 and Aroclor 1016, 1242, 1254, 1260 [1] and on the relative retention time values of 209 PCB congeners [2]. The weight percentage of the congener(s) which corresponds to each peak in the mass chromatograms was calculated by comparison of its height with that of certified reference standard with the same molecular weight. Each weight percentage of PCB congener(s) corresponding to each ECD peak was obtained by summing up the percent contribution values of the PCB congeners co-eluting. The results showed that it was possible to use KC products and their equivalent mixture as secondary reference standards for congener-specific PCB quantification.     

Flow-injection spectrophotometric determination of chloramben

Abstract

A method for the dechlorination of PCB mixtures (Aroclor formulations) to biphenyl was extended to soils. The contaminated sample was mixed with magnesium flakes, potassium hexachloropalladiate (K₂PdCl₆), propan-2-ol and water then permitted to react for up to six hours. Biphenyl, recovered by extraction into hexane, was quantified by gas chromatography with flame ionization detection. The reaction was very efficient in propan-2-ol / water (～95%), surfactant emulsion or sand mixture and virtually complete in soil provided that excess magnesium (2 g) and the K₂PdCl₆ were added to the sample prior to the addition of water. Higher PCB loadings were readily determined in field contaminated soils either by direct determination within the matrix or by standard additions. However, analyte concentrations were appreciably over-estimated in Soxhlet or sonication extracts of a certified reference material that contained sub-ppm levels of analyte. The over-estimation is considered to result from the conversion in part of natural organic matter to biphenyl.     

Validatibility of a capillary isoelectric focusing method for impurity quantitation

A strategy is presented for examining the validatability of a capillary isoelectric focusing (cIEF) method, intended for quantitation of product-related impurities in a protein drug substance, according to guidelines published by the International Conference on Harmonization (ICH). The results of this study demonstrate the suitability of cIEF as an analytical method for the quantitation of two product-related impurities in a protein drug substance: a monodeamidated degradation product and an aggregated form of the parent molecule. A range of impurity levels was generated by spiking the isolated impurity species, into a representative production lot of the drug substance. Six impurity spike levels (0.5-12% impurity for deamidated species and 0.5-8% impurity for aggregated species) were analyzed in triplicate. Measurement of impurity peak area percent in the spiked samples provided the data for computing specificity, accuracy, precision, linearity and limit of quantitation (LOQ) for the impurities. Accuracy, defined as the agreement of peak area percent for impurity species with the theoretical impurity percentage from the spike ratio, was 85-96% for the deamidated species and 73-97% for the aggregated species. A linear relationship was found between the measured area percent and the theoretical percent impurity for both impurity species (coefficient of determination, r2=0.9994 for deamidated species and =0.9827 for aggregated species). Precision (repeatability) studies demonstrated a low relative standard deviation (RSD) value (<6%) at all spike levels for both impurity species. Intermediate precision and reproducibility were evaluated by simulating many of the multivariable testing conditions expected during the life cycle of an analytical method, such as multiple equipment and laboratories. Repeated analyses of the drug substance under these varied conditions, yielded RSD values of <20%, for both impurity species. The LOQ, defined as the lowest impurity level where both accuracy and precision were achieved, was assigned at the 0.5% impurity level for both impurity species. This work illustrates a successful strategy in applying the ICH validation guidelines for impurity analytical methods to a cIEF method. Moreover, the data demonstrate the ability of cIEF to be used reliably as an analytical method for impurity quantitation.