Sohxlet Extraction Research Articles

N-AlKanes Base Exploration as Potential Petroleum Source Rocks in ILullemmeden Basin (Sokoto Basin) North west Nigeria

The aim of this work is to investigate the potential petroleum shales of Dukamaje formation in Sokoto basin for their petroleum potentials. A total of sixteen samples were obtained from different parts of the basin. The samples were subjected to sohxlet extraction to extract the bitumen. The bitumen was subjected to column chromatography and aliphatic and aromatic fractions were collected from each sample by using DCM and n-hexane as solvents. The fractions were subjected to GC/MS analyses with the application of SIM method (selected ion monitoring) which revealed the wide variety of hydrocarbons compounds including n-alkanes, hopanes, sterenes, phenanthrenes, methyl-phenanthrenes and triaromatic steroids. Interpretation biomarker parameters revealed that the rocks under studies are endowed with organic matter. Also biomarker correlation parameters were employed to compute the quantity of organic matter, type of organic matter, thermal maturity of the organic matter and to assess the depositional environment of the rocks samples. The biomarker parameters indicated that the source organic matter is mostly from marine environment, the depositional condition found to be anoxic reducing condition. The shales are reach in organic matter and the shales are found to be partially matured.

Evaluation of Ibuprofen Emulsion Formulated Using Moringa Oleifera Seed Oil

This study was carried out to evaluate the physicochemical properties of ibuprofen emulsions formulated using Moringa oleifera seed oil as the oil phase. Moringa oleifera seeds were de-hulled, dried ad pulverized into powder. A 100 g quantity was extracted by Sohxlet extraction using petroleum ether. The extracted moringa seed oil was characterized based on refractive index, specific gravity, ash and moisture content. It was used to prepare ibuprofen emulsions using the wet gum method. The prepared emulsions were evaluated based on physicochemical properties such as pH, viscosity and organoleptic properties. The extracted oil was golden yellow in colour with characteristic odour. It has refractive index, density, and specific gravity of 1.461±0.002, 0.92±0.01 g/dm, and 0.92±0.01 respectively. The ash and moisture contents were 2.86% and 6.42% respectively. The pH of the prepared ibuprofen emulsions were between 4. 9±0.00 and 5.2±0.01 even after 4 weeks of stability study. The viscosity of the emulsions ranged from 1500±0.00-2500±0.01 mPas even after 4 weeks stability study. All the emulsions were the oil-in-water type. Stable ibuprofen emulsions were formulated using moringa seed oil as the oil phase and either acacia or Tween 80 as the emulsifying agent. The emulsions were comparable in physicochemical properties and stability to those prepared using arachis oil as the oil phase.

Acute Toxicity Test and Behavioural Activity of Aqueous and Ethanol Dried Leaf Extracts of Solenostemon monostachyus In Mice

Background: The leaves of Solenostemon monostachyus have been traditionally used for various medicinal purposes, including CNS related ailments.
 Objective: To evaluate the median lethal dose (LD50), behavioural activity with possible mechanism(s) of action of aqueous dried leaf extract (AESM) and ethanol dried leaf extract (EESM) of Solenostemon monostachyus
 Method: The aqueous and ethanol extracts were obtained using sohxlet extraction and 80% ethanol respectively. The LD50 of the extracts was determined orally (p.o.) and intraperitoneally (i.p.). The effects of the AESM and EESM (200, 400, 800 mg/kg, p.o., n=6) on novelty-induced behaviours (NIB) were evaluated using the open field test. Possible mechanism(s) were evaluated using antagonists: flumazenil, naloxone and cyproheptadine at 2 mg/kg each, atropine and yohimbine at 1 mg/kg each.
 Results: The LD50 values obtained for AESM and EESM were 3808 and 2154 mg/kg p.o. respectively, while i.p.,values were 490 and 693 mg/kg respectively. AESM and EESM (200, 400, 800 mg/kg, p.o.) significantly (p < 0.05) reduced the NIB. The probable pathways could be majorly facilitated through adrenergic, and GABAergic pathways, though the serotonergic, opioidergic and muscarinic pathways may be implicated. These pathways, except the muscarinic pathway may be implicated in the action of EESM.
 Conclusion: The aqueous and ethanol dried leaf extracts of S. monostachyus showed slight and moderate toxicity respectively, suppressed CNS which could be mediated mainly through antagonism of adrenergic and augmentation of GABAergic neurotransmission, while cholinergic (except EESM), opioidergic and serotonergic pathways may be involved.

Antimicrobial, Antioxidant and Cytotoxic Activities of Cosmos Caudatus extracts

This study aims to investigate the in-vitro antimicrobial potential of Cosmos caudatus against pathogenic bacteria, its antioxidant activity and cytotoxic effect on cancer cell lines. In vitro antimicrobial activities of ethanol and water extracts of Cosmos caudatus herb against pathogenic bacteria, Staphylococcus aureus, Salmonella sp., Pseudomonas aeruginosa and Escherichia coli were tested by agar well diffusion. Antioxidant properties of the extracts was evaluated by 2,2-diphenyl-1-picryl-hydrazyl radical scavenging activity method. Additionally, cytotoxic activity of the extracts on HCT 116 colorectal carcinoma cell line was determined by (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay. Vero cells were used as a control. The quantification of these extracts showed that this plant is rich in secondary metabolites. Moreover, the conventional soxhlet extraction technique was more effective than maceration and ultrasonic assisted extraction technique. In antioxidants assay, both the ethanolic and water extracts through ultrasonic extraction method exhibited the highest DPPH free radical scavenging capacity compared to maceration and sohxlet extraction method. In antimicrobial assay, both the water and ethanol extracts showed no inhibitory action against the tested pathogenic bacteria. For anticancer activity, the F2, F7 and F8 fractions showed potent dose dependent cytotoxicity on Human Colorectal Carcinoma Cells with IC50 value of 15.53 ± 0.4, 32.72 ± 0.3 and 34.16 ± 1.4 μg/mL, respectively.

Determination of bioactive compounds in methanol leaf extract of Hyptis lanceolata Poir. using gas chromatography and mass spectrometry (GC-MS) technique

Hyptis lanceolata Poir. is a medicinal plant wildly distributed in parts of Nigeria. The plant is used in traditional medicine for the cure of skin infections and as an analgesic in Nigeria. The plant is underutilized and documentation of its chemical composition is poor. The leaves of the plant were subjected to sohxlet extraction using methanol as solvent. The extracts were further subjected to Gas Chomatography and Mass Spectrometry (GC-MS) to determine the presence of bioactive compounds. GC-MS analysis of the methanolic extract of the plant showed the presence of eight compounds. The major compounds include α-Linolenic acid (45.86%), dihomo ƴ-linolenic acid (30.50%), squalene (8.27%) and Imidodicarbonimidic diamide, N,N-dimethyl- (6.61%). Previous studies have shown these compounds to be efficient in the treatment of several ailments, hence the presence of these compounds support the use of this plant in traditional medicinal. It is recommended that the methanol extract of the plant be subjected to further pharmacological and phytochemical studies in order to achieve the full potentials of the plant.

Combined activity of Azadirachta indica and Dodonea viscose leaves extract on some selected pathogens

The study was undertaken to investigate the antimicrobial activity both individually and in combination of two Nigerian plants (Azadirachta indica and Dodonea viscosa) against a variety of pathogenic bacteria. Five bacterial species namely; Staphylococcus aureus, Escherichia coli, Salmonella typhi, Klebsiella pneumoniae and Pseudomonas aeruginosa were selected for the assays. The powdered plant materials of the two plants were extracted using sohxlet extraction technique with methanol water and petroleum ether as solvents. The crude extracts of the two plants were subjected to phytochemical screening for qualitative detection of plant secondary metabolites. The extracts were further tested for antibacterial activity against the selected pathogens singly and then combined using agar well diffusion method. Antibacterial activity of the two plants singly indicates that the methanolic extract possess the highest antibacterial activity at a concentration of 50mg/ml with an inhibition zone of 23.3±0.5mm compared to aqueous extract with 21.7±0.5mm inhibition zone at a concentration of 50mg/ml. The least activity was observed with the petroleum ether extract with an inhibition zone of 7.3±0.5mm at a concentration of 12.5mg/ml. Combination of the plants extracts exhibited lower antibacterial activity on the test isolates compared to single plants as evidenced by the production of lower inhibition zones.
 Key words: Azadirachta indica, Dodonea viscosa, pathogens, antimicrobial activity, synergistic effect

Oil extraction from butter fruit (<i>Dacryodes edulis</i>) seeds and its optimization via response surface and artificial neural network

In this study, oil was extracted from butter fruit ( Dacrydes edulis ). To model and optimize the process conditions of oil extraction, Response Surface Methodology (RSM) and Artificial Neural Network (ANN) were used. Physicochemical analysis of the oil was carried out in order to determine the suitable of oil for industrial applications. Dacryodes edulis seeds were collected from Ikot Abasi Village in Eket Local Government of Akwa Ibom State, Nigeria. The seed was washed with clean water to remove dirt, and open with a sharp stainless knife to remove the seed from the pulp. The seeds were cut into small pieces and sundried for 5 days and were grinded into powder. Oil extraction from the powder seed was carried out using Sohxlet extraction method. The experiment was designed using Box-Behnken Design approach on three levels, three factors which generated 17 experimental runs. Independent factors considered were extraction time (X 1 ), solvent volume (X 2 ) and sample weight (X 3 ). The accuracy of the regression model obtained from the optimization software was determined using the co-efficient of determination (R 2 ). Results showed the highest oil yield of 17.878% (w/w) was obtained at solvent volume of 200 ml, sample weight of 50 g and extraction time of 55 min, respectively. However, response surface methodology predicted an oil yield of 17.826% (w/w), while the artificial neural network predicted 17.875% (w/w) at the same variables condition. The predicted values were validated in triplicate, and an average of 17.46% (w/w) and 17.72% (w/w) were obtained for RSM and ANN, respectively. The predicted values obtained were well within the range predicted. The coefficient of determination, which determines the model accuracy, was obtained to be 0.8454 for RSM and 0.8712 for ANN. Physicochemical analysis of the oil showed the oil is highly unsaturated with high saponification value and high iodine value. The study concluded that Dacryodes edulis seeds are found to be rich in oil and the oil can be applicable in industries as raw materials for products formation. Keywords: Dacryodes edulis seeds, response surface, artificial neural network, optimization, extraction, physicochemical properties

Chemical and Microbial Quality Assessments of Some Economic Important Artisanal Fresh Water Fish Species (Tilapia zilli, Clarias gariepinus, Chrysichthys nigrodigitatus and S. melanotheron) in Selected Coastal Markets of Lagos State, Nigeria)

Nutritional qualities of some selected fresh water fish species sold for consumption in the Badagry, Epe, Ikorodu and Ojo areas of Lagos state, Nigeria was assessed to ascertain the wholesomeness and health risk associated with consuming the most common sort after fish in these locations. A total of 100 fish samples, Red belly Tilapia (T. zilli), African Mud Catfish (C. gariepinus), Silver Catfish (C. nigrodigitatus) and Black Chin Tilapia (S. melanotheron) (25 specimens each) with a weight ranges between 50-180 g, were collected from different locations. The samples were iced and taken to the Biochemistry and Pharmaceutical laboratory sections of the College of Medicine University of Lagos, Idi-Araba, Lagos, Nigeria. The iced samples were maintained in alternate layers of ice until spoilage was noticed. Chemical analysis was conducted using Spectrophotometer, Atomic Absorption Spectrophotometer, Sohxlet Extraction Apparatus, Thiobarbituric Acid (TBA), The Acid Value (AV), Peroxide Value (PV), Iodine value, Free Fatty Acids (FFA) and Saponification value were determined. The result indicates higher TBA (8.79 ± 0.05), (7.59 ± 0.06), (7.46 ± 0.04) and (6.99 ± 0.05) for T. zilli, C. nigrodigitatus, S. melanotheron and C. gariepinus respectively in Ojo Lagoon, higher iodine value (9.69 ± 0.01) for T. zilli in Ojo Lagoon; (8.75 ± 0.21), (9.35 ± 0.07) and (8.45 ± 0.07) for C. nigrodigitatus, S. melanotheron and C. gariepinus respectively in Epe Lagoon and the acid values (3.31 ± 0.04), (2.45 ± 0.04) and (3.79 ± 0.04) for T. zilli, C. nigrodigitatus and S. melanotheron respectively in Badagry Lagoon and (2.25 ± 0.04) in Ojo Lagoon were within the standard limits. Higher mean mould load recorded were (1.22×104), (1.78×103), (1.90×103) for C. gariepinus, S. melanotheron and T. zilli respectively in Ikorodu Lagoon, while (3.47×103) was recorded for C. nigrodigitatus in Badagry Lagoon. The results indicated a notable quality improvement leading to a high quality fish in terms of the taste, colour, odour, shelf life and market value. The high iodine value recorded in this study from different locations suggests that the fish species contain high level of unsaturated oil and as such could reduce the risk of heart diseases, high cholesterol, depression, anxiety, low immunity, cancer, eye disorders and ulcers in humans when consumed. None of the fish samples exceeded the mould load limit for fish thereby exhibiting no risk on public health; therefore the fish are wholesome and safe for human consumption.

Influence of extraction conditions on the recovery lipids extracted from the dry biomass of duckweed Lemna minor

Previous studies on the composition of lipid content of higher aquatic plants can be found in the literature. The present work aims to study the effect of various solvent extraction systems on the recovery of lipids extracted from the dry biomass of Lemna minor, using the same polar solvent (ethanol) and variating the non-polar solvent as follow: methanol-ethanol, chloroform-ethanol, hexane-ethanol, diethyl ether-ethanol, petroleum ether-ethanol at different volume ratio. The goal is to select a Sohxlet extraction method that shortens the extraction duration and increases the lipid recovery using various solvents. To intensify the extraction process, homogenization was used as a cell disruption method. It is shown that the yield of total lipids is increased by using homogenization from 4.6% to 6.0%. When studying the influence of the solvent system, the highest yield of total lipids was obtained by using hexane-ethanol with a volume ration of 1:1 (8.0% total lipids by dry mass). The yield of lipids recovered from dry biomass of Lemna minor increases by increasing the extraction time. The optimum extraction time was found to be no more than 300 minutes. The composition of the lipid fraction is mainly represented by sterols, fatty acids and triglycerides.

Recovery and reuse of discontinuous carbon fibres by solvolysis: Realignment and properties of remanufactured materials

Discontinuous carbon fibre tows were recovered after solvolysis of an aeronautic type composite made with RTM6 epoxy resin. A Sohxlet extraction method was used to quantify the organic residue on the fibre tows and showed that less than 3 wt% was remaining on the surface. The recovered tows were therefore reused directly to manufacture a plate with randomly distributed carbon fibres and then three plates with realigned carbon fibres. The latter were then characterised and tested and the results obtained were compared to the material manufactured using the same type of virgin fibres by the same method. The materials made from recycled carbon fibres showed very good properties in comparison to the virgin fibre material, despite the presence of flaws such as quality of the fibre surface after solvolysis, alignment and voids). This is the first time in the open literature that carbon fibres recovered from solvolysis were reused in this way together with characterisation of the resulting materials.

Double bond-functionalized POSS: dispersion and crosslinking in polyethylene-based hybrid obtained by reactive processing

Polyethylene-based organic inorganic hybrids were prepared by one-step reactive melt mixing using a mono-functionalized nanofiller, i.e., allyl-heptaisobutyl-substituted polyhedral oligomeric silsesquioxane (1POSS) and a multi-functionalized octavinyl polyhedral oligomeric silsesquioxane (8POSS). The hybrids were also prepared in dicumyl peroxide (DCP) presence and morphological, spectroscopical and calorimetric analysis were carried out. Moreover, rheological measurement and Sohxlet extraction were performed on investigated samples. It was inferred that double bonds of POSS functional groups were triggered by radicals coming from the peroxide decomposition or from the degradation reactions occurring during preparation. The type of the functional groups (mono- or multi-reactive) of the POSS is a leading factor, along with radicals content in the systems, in the formation of a polymeric network. In particular, the presence of multi-reactive groups in 8POSS molecules results in a successful POSS grafting/crosslinking in the polymeric backbone: the covalent bonds formation between nanofillers and matrix during processing improves POSS dispersion within the polyolefin matrix and leads to a network structure formation.

Effects of ultrahigh pressure extraction on yield and antioxidant activity of chlorogenic acid and cynaroside extracted from flower buds of Lonicera japonica

The present study was designed to establish and optimize a new method for extracting chlorogenic acid and cynaroside from Lonicera japonica Thunb. through orthogonal experimental designl. A new ultrahigh pressure extraction (UPE) technology was applied to extract chlorogenic acid and cynaroside from L. japonica. The influential factors, including solvent type, ethanol concentration, extraction pressure, time, and temperature, and the solid/liquid ratio, have been studied to optimize the extraction process. The optimal conditions for the UPE were developed by quantitative analysis of the extraction products by HPLC-DAD in comparison with standard samples. In addition, the microstructures of the medicinal materials before and after extraction were studied by scanning electron microscopy (SEM). Furthermore, the extraction efficiency of different extraction methods and the 2, 2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activities of the extracts were investigated. The optimal conditions for extracting chlorogenic acid and cynaroside were as follows: ethanol concentration, 60%; extraction pressure, 400 MPa; extraction time, 2 min; extraction temperature, 30 °C; and the solid/liquid ratio, 1 : 50. Under these conditions, the yields of chlorogenic acid and cynaroside were raised to 4.863% and 0.080%, respectively. Compared with other extraction methods, such as heat reflux extraction (HRE), ultrasonic extraction (UE), and Sohxlet extraction (SE), the UPE method showed several advantages, including higher extraction yield, shorter extraction time, lower energy consumption, and higher purity of the extracts. This study could help better utilize L. japonica flower buds as a readily accessible source of natural antioxidants in food and pharmaceutical industries.

Evaluation of the acute and sub acute toxicity of Annona senegalensis root bark extracts

ObjectiveTo investigate the safety profile of Annona senegalensis (A. senegalensis). MethodsDried powdered root-bark of A. senegalensis was prepared by Sohxlet extraction using methanol-methylene chloride (1:1) solution and concentrated to obtain the methanol-methylene chloride extract (MME). MME was fractionated to obtain the n-hexane (HF), ethylacetate (EF) and methanol (MF) fractions. Acute toxicity (LD50) test was performed with MME, HF, EF and MF in mice by oral route. The sub acute toxicity studies were performed in rats after 14 days of MME administration while haematological and biochemical parameters were monitored. ResultsMedium lethal (LD50) values of 1 296, 3 808, 1 265 and 2 154 mg/kg were obtained for the MME, MF, HF and EF, respectively. The sub-acute toxicity studies indicated a significant (P<0.05) increase in the body weight of both the treated rats and the control. The haematological tests indicated no change in the packed cell volume values but a significant (P<0.05) increase in the total WBC count at 100 and 400 mg/kg doses. The differential analysis showed a decrease in the nutrophils and a non-significant increase in the lymphocyte counts. The liver transaminase enzymes, alanin transaminase and aspartate transaminase showed no significant increase compared to the control. Histopathological examination of the liver sections also indicted no obvious signs of hepatotoxicity except with the 400 mg/kg dose that showed degeneration and necrosis of the hepatocytes. ConclusionsThese results indicated that the root bark extracts of A. Senegalensis are safe at the lower doses tested, and calls for caution in use at higher doses in treatment.

Extraction of steroid saponins from Paris polyphylla Sm. var. yunnanensis using novel ultrahigh pressure extraction technology

A new method of ultrahigh pressure extraction (UPE) was used to extract steroid saponins from Paris polyphylla SM. var. yunnanensis (chonglou) at room temperature. The microstructure of the drug before and after the extraction was studied by scanning electron microscopy (SEM). The mechanism of UPE is discussed and demonstrated based on the results of SEM investigation. The influence of several factors, including solvent type, solvent concentration, UPE pressure, UPE time, and liquid-to-solid ratio, has been studied in order to optimize the extraction process. The optimum extraction takes place with an ethanol concentration of 90%, a pressure of 400 MPa, an extraction time of 2 min, and a liquid-to-solid ratio of 40: 1. In comparison with usual room-temperature extraction at normal pressure, ultrasound-assisted extraction, microwave-assisted extraction, and Sohxlet extraction, the UPE method shows higher efficiency at room temperature.

Spectroscopic determination of poly-aromatic compounds in petroleum contaminated soils

The determination of poly-aromatic hydrocarbons (PAHs) in the soil is of interest because of their carcinogenic and mutagenic activity in biological systems. The present study deals with the rapid application of infrared, fluorescence, synchronous luminescence spectrometries and gas chromatography to detect organic pollutants and their quantity in the soil. Sohxlet extraction followed by column separation was used to isolate organic pollutants. Although several solvent mixtures were used as eluents for the column, the solvent mixture, hexane:dichloromethane (50:50) efficiently extracts the aromatic compounds. Total petroleum hydrocarbons (TPH) measured by IR were found at high concentrations (30810.0 ppm) in the contaminated soil compared with the reference soil (30.0 ppm). Furthermore, the fluorescence results reveal that almost one-fourth of the 30810.0 ppm are aromatic hydrocarbons. In addition, the presence of PAHs such as naphthalene, acenaphthene, fluorene, fluoranthene, phenanthrene, pyrene, benzo(a)pyrene, chrysene, and dibenzo(a,h)anthracene in the polluted soil was determined by using synchronous study.

Forward-and-back dynamic ultrasound-assisted extraction of fat from bakery products

A dynamic ultrasound-assisted extraction method prior to the gravimetric determination of total fat content in bakery products is proposed. An open approach in which forward-and-back extractant steps and cycles of extract draining and filling of the sample chamber with fresh extractant was used, which provided the best results as compared with both an open system with forward-and-back of a single extractant volume and an one-direction open system. Recoveries from 99.7 to 100.7% compared with Sohxlet extraction were obtained. The repeatability and within laboratory reproducibility, expressed as relative standard deviation (R.S.D.), were 2.04 and 2.74%, respectively. As compared with conventional Soxhlet, the extraction time was shortened more than five times—from 16 to 3 h—in the case of cookies and more of eight times—from 8 to 1 h—in the case of snacks. Thirteen or 25 ml of hexane was required for total extraction in 10 or 20 cycles, depending on the sample.

Evaluation of the anti-asthmatic property of Asystasia gangetica leaf extracts

The leaf of Asystasia gangetica T. Adams (Acanthaceae) is used in many parts of Nigeria for the management of asthma. This study was aimed at investigating the anti-asthmatic property of hexane, ethylacetate, and methanol extracts of the leaves of Asystasia gangetica, obtained by successive sohxlet extraction. The results indicated that the extracts did not exhibit contractile or relaxant activity in isolated tissue preparations; however, they inhibited the contraction evoked by spasmogens; the IC 50 were calculated, where possible. The extracts relaxed histamine-precontracted tracheal strips in the following degree of potency—ethylacetate extract>hexane extract=methanol extract. The extracts also exhibited anti-inflammatory activity in the order of magnitude—methanol extract>hexane extract>ethylacetate extract. Acute toxicity test estimated an i.p. LD 50 of 2150 mg/kg in mice for methanol extract while phytochemical screening showed the presence of carbohydrates, proteins, alkaloids, tannins, steroidal aglycones, saponins, flavonoids, reducing sugars, and triterpenoids, with the methanol extract having the highest number of constituents. The study justified the use of the leaf of Asystasia gangetica in the management of asthma in Nigerian folk medicine.

Identification of the surface characteristics of carbon blacks by pyrolysis GC–MASS

Subtle differences in surface characteristics on carbon blacks are investigated by using Curie-point Pyrolysis Gas Chromatography Mass Spectrometry (CP–PGC–MASS). The PGC–MASS diagrams of carbon blacks are assigned as the fingerprints for distinguishing differences in surface properties. For carbon black-N220 pyrolyzed below 445°C, only one aromatic ring hydrocarbons are found in PGC–MS diagrams, whereas, when pyrolyzation temperatures exceed 445°C, two ring aromatic hydrocarbons are also found. Toluene Sohxlet extraction of the carbon blacks will not cause a significant change of surface properties, however toluene will remain as a contaminant on the surface even for those samples dried for 24 h at 200°C before PGC–MASS measurements. A new surface structure model of carbon black is proposed based on the PGC–MASS results.

Characterization of commercially available coffee filter papers

Abstract Commercially available coffee filter papers were evaluated for extractable materials to determine differences between chlorine bleached, peroxide beached and unbleached products. Organic species were determined by initial Sohxlet extraction followed by GC/MS analysis for semi‐volatile organics, dibenzofurans and dioxins. Inorganic species were initially extracted with heated water. Representative inorganics were determined either by atomic absorbtion spectroscopy or ion selective electrodes as the method of analysis. No direct relationship between bleaching method and the presence of halo‐genated materials in the final filter product was observed. Only in one cases was a single dioxin isomer detected. Three semi‐volatile species not consistent with natural products were detected in any of the filter papers. Both a chlorine bleached and unbleached paper were found to contained a single brominated species whereas tributyl phosphate, a plasticizer for cellulose esters and plastics was found in a sin...