Gas Chromatography-electron Capture Research Articles

Screening of halogenated phenolic compounds in plasma and serum from marine wildlife

The growing knowledge of the impact of halogenated phenolic compounds on hormonal and metabolic systems has led to an increased interest in the exposure and potential effects of these compounds in wildlife. In the present study, a screening procedure was developed to detect and quantify halogenated phenolic compounds in serum and plasma from marine wildlife. A mass spectral library containing selective ion monitoring data was created using gas chromatography electron capture negative ionization mass spectrometry. The selective ion monitoring data in the library were accompanied with retention indices to increase the specificity of each entry in the library. The library together with the developed extraction procedure and optimized instrumental settings can be used for the detection of 52 different halogenated phenolic compounds of environmental concern, including 23 hydroxylated polychlorinated biphenyls and 24 hydroxylated polybrominated diphenyl ethers. The instrument limit of detection for the compounds included in the library ranged from 30 to 320 fg/injection, with a median detection limit of 90 fg/injection. The average recovery of 11 different halogenated phenolic compounds, from four species of marine wildlife, was 66 ± 14%. A full-scan mass spectral library was also created containing an additional seven compounds. Gray seals, long-tailed ducks, and two species of fish from the Baltic Sea were screened for halogenated phenolic compounds using the developed procedure. A total of 33 compounds included in the library were detected and quantified.

Occurrence of a Polychlorinated Biphenyl (PCB) Congener in Surface Water, Sediments and Blackchin Tilapia (<i>Sarotherodon melanotheron</i>) from Ologe Lagoon, Nigeria

Polychlorinated biphenyls (PCBs) are persistent organochlorine chemicals that are toxic to aquatic organisms and humans. PCBs levels were assessed in surface water, sediments and fish from Ologe Lagoon, a major water body receiving treated effluents from Agbara Industrial Estate, using Gas Chromatograph-Electron Capture Detector (GCECD). 2,4,4’-Trichlorobiphenyl (2,4,4’-TCB) was the only PCB congener detected in the assessed matrices. Sediment 2,4,4’-TCB levels ranged from 0.0033±0.00333 to 0.0430 ± 0.00351ng/g. There was a significant (p < 0.05) seasonal variation in the levels in sediments and surface water. The level in surface water from Zone 3 was above USEPA’s safe limit (0.0005 mg/L) in the rainy season. There was no significant (p > 0.05) seasonal difference in the mean concentrations of 2,4,4’-TCB in fish, and the levels were lower than WHO’s safe limit (0.2 mg/kg). Based on the negligible to low levels of 2,4,4’-TCB in S. melanotheron inhabiting the lagoon, the fish was considered safe for consumption. Levels of 2,4,4’- TCB found in the sediments and surface water in this study indicate that levels may change with season, therefore, we recommend that the concentrations of the compound are regularly monitored in order to timely avert toxic levels of bioavailable 2,4,4’-TCB in the water body.Keywords: Polychlorinated biphenyls, Sarotherodon melanotheron, Sediments, Surface water.

Dispersive Liquid-Liquid Microextraction Method for the Simultaneous Determination of Four Isomers of Hexachlorocyclohexane and Six Pyrethroid Pesticides in Milk by Gas Chromatography Electron Capture Detector

In this study, a simple and rapid dispersive liquid-liquid microextraction method was established, and the residuals of four isomers of hexachlorocyclohexane and six kinds of pyrethroid pesticides in milk were simultaneously determined by gas chromatography electron capture detector (GC-ECD). The milk sample was first extracted with acetonitrile and cleaned with primary secondary amine (PSA). Then 0.5 mL of acetonitrile was mixed with 140 μL of cyclohexane and rapidly injected into 3 mL of pure water. After vortexing and centrifugation, the floating phase was removed with a 0.1-mL pipette into the GC-ECD. The type and volume of extraction solvent, volume of disperser solvent, volume of water, vortex time, and amount of salt were optimized. Under optimal extraction conditions, the ten pesticides showed a good linear relationship in a certain concentration range in milk matrix, and the correlation coefficients were greater than 0.99. The limits of detection ranged from 0.07 to 2 μg/kg, and the limits of quantitation ranged from 0.2 to 5 μg/kg. The average recovery rates were between 70.1% and 106.3%, and the relative standard deviations were less than 15.2%. This method can be used for the determination of hexachlorocyclohexane and pyrethroid pesticides in milk and for subsequent research.

Spent Mushroom Compost of Pleurotus ostreatus: A Tool to Treat Soil Contaminated with Endosulfan

Composts especially spent mushroom composts (SMC) have been used for their ability to degrade toxic organic pollutants. Due to extreme toxicity, endosulfan (C9H6Cl6O3S) is categorized as a Category 1 pollutant by the U.S. EPA because of its well-reported carcinogenicity. This study was done to monitor the biodegradation potential of SMC against this pesticide. For this purpose, bioreactors (BRs) system was designed to mimic the field conditions. Soil within all four BRs contaminated with endosulfan was amended with four different treatments of SMC. Quantitative reduction in amount of endosulfan isomers was calculated using Gas Chromatography–Electron Capture Detector. For the monitoring of metabolites formed as a result of biodegradation, Gas Chromatography–Mass Spectrometry was used. Maximum attenuation was observed in BR1 (fresh SMC and soil). In BR2 when fresh SMC was added in sterilized soil, rate of removal was declined as compared to BR1. In another bioreactor BR3, where unsterilized soil was used with sterilized SMC, total reduction in quantity of endosulfan was less than BR1 and BR2. BR4 (abiotic control) showed the least reduction suggesting the role of SMC and soil microbes. Degradation was well described using simple first-order kinetics which revealed that the active microcosm of BR1 manifested least DT50. Denaturation of either SMC(BR3) or soil(BR2) or both (BR4) resulted in less biodegradation than BR1.

Combined Approach for Determining Diuron in Sugarcane and Soil: Ultrasound‐Assisted Extraction, Carbon Nanotube‐Mediated Purification, and Gas Chromatography–Electron Capture Detection

Diuron is a urea herbicide that is frequently detected in surface water, groundwater, and marine waters. However, there are few methods or guidelines reported on ensuring the quality of sugarcane and soil. In this study, a method was developed for detecting diuron to ensure the quality and safety of food and sugar. Mass spectrometry was used to identify 3,4-dichloroaniline as a marker for the thermal decomposition of diuron, and thus, as a representative component for quantitative diuron analysis. This approach can be used to rapidly detect trace amounts of diuron. In addition, ultrasound-assisted extraction (UAE) and carbon nanotube column purification were used in conjunction with gas chromatography-electron capture detection to detect diuron. The method was then evaluated for its accuracy, detection limit, and viability. The effects of extraction solvent, ultrasound time, and ultrasound power on the extraction efficiency of the analyte from sugarcane and soil were also investigated. The efficiency and optimum conditions of UAE were examined through single-factor experiments and Box-Behnken design (BBD). The optimal extraction conditions were identified as follows: acetonitrile as the extraction solvent, extraction temperature of 27°C, extraction time of 3.4min, and ultrasound power of 70 W. Under these conditions, high linearity was achieved for diuron concentrations of 0.01 to 5.0 mg/L, and the purification correlation coefficient was consistently greater than 0.998. Hence, gas chromatography, combined with UAE and BBD, offers superior efficiency extraction, which is sufficiently accurate and precise for pesticide residue analysis. PRACTICAL APPLICATION: We developed an accurate and cost-effective method for detecting diuron (a commonly used herbicide) in soil and sugar samples. We performed experiments to determine the optimum detection conditions for our method. This method can be used for online monitoring of sugar manufacturing processes to ensure food safety and quality.

Occurrence and Toxicological Risk Evaluation of Organochlorine Pesticides from Suburban Soils of Kenya.

The use of organic chemicals in agriculture and manufacturing has raised concerns about the dangers of organochlorine pesticides (OCPs) in the environment. By examining OCPs occurrence in the suburban soils from Kenya, this study revealed the distribution, concentrations, and the threat posed to the environment and human health. A gas chromatography electron capture detector was used to test the pesticides. The hexachlorocyclohexane (HCH) and dichlorodiphenyltrichloroethane (DDT) studied in soils of Kapsabet, Voi, and Nyeri towns showed concentrations ranging from 0.03–52.7, 0.06–22.3, and 0.24–24.3 ng/g respectively. The highest concentration of HCHs was in Kapsabet (0.03–48.1 ng/g), whereas the highest DDTs concentration was in Voi (n.d.–15.5 ng/g). Source identification revealed OCPs pollution originated from recent usage of DDT pesticides to control insect-borne diseases and from the use of lindane in agriculture. Correlation test revealed that total organic carbon influenced the presence of pesticides in the soils. The enantiomeric ratios of α-HCH/γ-HCH were <3 indicating the use of lindane while the ratios of DDE/DDT were <1 suggesting recent input of DDT. The cancer risk assessment showed values close to the set risk level of 10−6, suggesting the likelihood of exposure to cancer was not low enough, and control measures need to be established.

Development of Gas Chromatographic Method with Electron Capture Detector for Determination of Some PCDDs inWheat and Rice Grain Matrix

This study develops a gas chromatographic method coupled to micro-electron capture detector to determine four basic polychlorinated dibenzo- p -dioxins (PCDDs) congeners: 1, 1,2,3,7,8-pentachlorodibenzo- p -dioxin; 2, 2,3,7,8-tetrachlorodibenzo- p -dioxin; 3, 1,2,3,6,7,8-hexachloro-dibenzo- p -dioxin; and 4, 1,2,3,4,6,7,8-heptachlorodibenzo- p -dioxin in wheat and rice. The PCDDs were extracted using 1:1 acetone: n -hexane mixture followed by cleaning with acidic aluminium oxide in polypropylene mini columns and eluted with dichloromethane. In quantitative determinations, the limit of detection for congener 1 of PCDDs was 0.4 ng mL -1 while for other congeners (2–4) it was found to be 1.0 ng mL -1 . The congener 1 was checked at spiking levels of 0.02, 0.05 and 0.1 ng g -1 , and its recovery was 85.96–120.74% and 95.32–116.88% from wheat and rice, respectively. Wheat and rice were also spiked by congers 2–4 at spiking levels of 0.05, 0.1 and 0.5 ng g -1 ; the recovery ranges from wheat were 87.70–115.54%, 85.64–117.88% and 88.40–119.32% for congener 2, 3 and 4, respectively, while from rice the recovery was 77.67–115.68%, 83.18–119.68% and 79.76–131.15% for congener 2, 3 and 4, respectively. The limit of quantification was determined as 0.1 ng g -1 for congener 1 and 0.5 ng g -1 for other three PCDDs (2–4). The intra-day and inter-day RSDs of peak areas ( n = 3) for four congeners (2 ng mL -1 ) were ranged at 2.5–8.1% and 3.1–10.6%, respectively. This study provides a simple and cost-effective gas chromatographic-electron capture detector method to study some basic PCDDs in wheat and rice grains first time in Pakistan with fair precision and accuracy when expensive high resolution gas chromatographic-mass spectrometry method is not accessible.

Purification of 2,4,6-trinitrotoluene by digestion with sodium sulfite and determination of its impurities by gas chromatography–electron capture detector (GC-ECD)

Unwanted compounds in 2,4,6-trinitrotoluene (TNT) explosive, such as dinitrotoluene (DNT) and TNT isomers, can lead to exudation defects in the ammunition. For this reason, separation and analysis of impurities are valuable. Chemical treatment with sulfite solution is an important method for the purification of TNT. In this paper, TNT was purified by sodium sulfite solution with putting flaked TNT in digestion condition to remove existing impurities, and the effect of four main factors, digestion temperature, digestion time, concentration of sulfite solution and reaction time of sulfite with impurities on this purification process, was statistically investigated and optimized using central composite design of experiment (CCD) by Minitab software. Also, the qualification of final product was characterized by gas chromatography–electron capture detector method. Here, some conventional compounds such as 2,6-DNT, 2,4-DNT, 3,4-DNT, 2,4,5-TNT (γ-TNT), 2,3,4-TNT (β-TNT) and aniline derivatives were identified by standard solutions; then their concentrations were quantitatively determined by internal standard calibration method.

Exposure profile of mercury, lead, cadmium, arsenic, antimony, copper, selenium and zinc in maternal blood, cord blood and placenta: the Tohoku Study of Child Development in Japan

BackgroundThe effects of prenatal exposure to toxic elements on birth outcomes and child development have been an area of concern. This study aimed to assess the profile of prenatal exposure to toxic elements, arsenic (As), bismuth (Bi), cadmium (Cd), mercury (total mercury (THg), methylmercury (MHg), inorganic mercury (IHg)), lead (Pb), antimony (Sb) and tin (Sn), and essential trace elements, copper (Cu), selenium (Se) and zinc (Zn), using the maternal blood, cord blood and placenta in the Tohoku Study of Child Development of Japan (N = 594–650).MethodsInductively coupled plasma mass spectrometry was used to determine the concentrations of these elements (except mercury). Levels of THg and MeHg were measured using cold vapour atomic absorption spectrophotometry and a gas chromatograph-electron capture detector, respectively.ResultsMedian concentrations (25th–75th) of As, Cd, Pb, Sb, Sn and THg in the maternal blood were 4.06 (2.68–6.81), 1.18 (0.74–1.79), 10.8 (8.65–13.5), 0.2 (0.06–0.40) and 0.2 (0.1–0.38) ng mL−1 and 5.42 (3.89–7.59) ng g−1, respectively. Median concentrations (25th–75th) of As, Cd, Pb, Sb, Sn and THg in the cord blood were 3.68 (2.58–5.25), 0.53 (0.10–1.25), 9.89 (8.02–12.5), 0.39 (0.06–0.92) and 0.2 (0.2–0.38) ng mL−1 and 9.96 (7.05–13.8) ng g−1, respectively.ConclusionsTHg and Sb levels in the cord blood were twofold higher than those in the maternal blood. Cord blood to maternal blood ratios for As, Cd and Sb widely varied between individuals. To understand the effects of prenatal exposure, further research regarding the variations of placental transfer of elements is necessary.

Representative commodity for six leafy vegetables based on the determination of six pesticide residues by gas chromatography

A residue analytical method was developed for the determination of trichlorfon, chlorpyrifos, dimethoate, β cypermethrin, deltamethrin, and chlorothalonilin in six leafy vegetables by gas chromatography–electron capture detector (GC–ECD) and gas chromatography–flame photometric detector (GC–FPD). The method had a good linearity (R2 ≥ 0.9924) and precision (RSD ≤ 14.0%). The limits of quantification (LOQ) of six pesticides were all 0.01 mg/kg. Average recoveries of six pesticides ranged from 81% to 119%. The developed method was successfully applied to study the initial deposits, degrade characteristics, and terminal residues for six pesticides applied to six leafy vegetables under the same dose of formulation. The half-life of six pesticides was in the range of 0.8–8.8 days. The highest initial deposits, maximal residues, and terminal residues were found on leaf mustard and sweet potato leaves as the same pesticides were applied in different crops. Therefore, leaf mustard can be selected as representative commodity in the same subgroup to realize the residual extrapolation. This conclusion should be considered as a complement on crop classification of China.

Polyunsaturated fatty acids and child neurodevelopment among a population exposed to DDT: a cohort study

BackgroundChild neurodevelopment has been positively linked to maternal intake of polyunsaturated fatty acids (PUFAs) during pregnancy; however, it is unknown if that relationship persists among populations exposed to environmental neurotoxicants.ObjectiveThe aim of this work was to assess whether maternal dietary intake of PUFAs during pregnancy is positively associated with child neurodevelopment, whose mothers were environmentally exposed to 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane (DDT).MethodsA prospective cohort study with 276 mother–child pairs was performed in Mexico. Neurodevelopment was assessed by Bayley Scales II from children age 1 to 30 months. Dietary PUFAs intake was estimated by Food Frequency Questionnaire at 1st and 3rd trimester of pregnancy. DDE (1,1-dichloro-2,2-bis(p-chlorophenyl) ethylene, the main metabolite of DDT) maternal serum levels were determined by electron capture gas chromatography. Longitudinal multivariate linear mixed-effects analysis, which combines mental (MDI) and motor (PDI) Bayley scales in a single model, were performed.ResultsOur results show that in a sample environmentally exposed to DDT, maternal ingestion of DPA during the first trimester of pregnancy was positively associated with MDI (β = 0.10, 95% CI 0.02, 0.18) in children from 1 to 30 months. Likewise, our results suggest that dietary ALA may be also related to MDI.ConclusionDPA may benefit neurodevelopment even in populations exposed to DDT. Our results strengthen the importance of PUFAs intake during the prenatal period.

Dispersive liquid-liquid microextraction of chloroacetic acids from water samples using a syringe-like glass extraction vessel

A syringe-like glass extraction vessel was used for dispersive liquid-liquid microextraction using low-density solvents for the extraction of chloroacetic acids (CAAs, monochloroacetic acid, dichloroacetic acid, and trichloroacetic acid) from water samples. The CAAs were derivatized using n-octanol (extraction solvent) in the presence of sulfuric acid during and after extraction. Gas chromatography–electron capture detection was applied for the detection of n-octyl derivatize of CAAs. The effective parameters on the extraction efficiency, including the volume of extraction solvent, type, and volume of dispersive solvent, sample acidity, salt addition and extraction time were investigated. Also, the time and temperature of the derivatization reaction were optimized. The limits of detection and quantification were in the range of 0.02–6 and 0.05–10 μg L−1, respectively. Tap, river and swimming pool water samples were analyzed by the method. The relative recoveries were from 90 to 119%, with the RSDs being in the range of 2.1–4.7% (n = 3). The satisfactory results revealed the suitability and reliability of the method in determining the CAAs in environmental water samples.

Importance of biogenic volatile organic compounds to acyl peroxy nitrates (APN) production in the southeastern US during SOAS 2013

Abstract. Gas-phase atmospheric concentrations of peroxyacetyl nitrate (PAN), peroxypropionyl nitrate (PPN), and peroxymethacryloyl nitrate (MPAN) were measured on the ground using a gas chromatograph electron capture detector (GC-ECD) during the Southern Oxidants and Aerosols Study (SOAS) 2013 campaign (1 June to 15 July 2013) in Centreville, Alabama, in order to study biosphere–atmosphere interactions. Average levels of PAN, PPN, and MPAN were 169, 5, and 9 pptv, respectively, and the sum accounts for an average of 16 % of NOy during the daytime (10:00 to 16:00 local time). Higher concentrations were seen on average in air that came to the site from the urban NOx sources to the north. PAN levels were the lowest observed in ground measurements over the past two decades in the southeastern US. A multiple regression analysis indicates that biogenic volatile organic compounds (VOCs) account for 66 % of PAN formation during this study. Comparison of this value with a 0-D model simulation of peroxyacetyl radical production indicates that at least 50 % of PAN formation is due to isoprene oxidation. MPAN has a statistical correlation with isoprene hydroxynitrates (IN). Organic aerosol mass increases with gas-phase MPAN and IN concentrations, but the mass of organic nitrates in particles is largely unrelated to MPAN.

MONITORING OF ORGANOCHLORINE PESTICIDE RESIDUES IN OREOCHROMIS NILOTICUS COLLECTED FROM SOME LOCALITIES IN EGYPT

Tilapia nilotica (Oreochomis niloticus) is the major fish species consumed in Egypt, particularly due to its high nutritive value, palatability and relatively low price compared with other kinds of fishes or red meat. In Egypt, tilapia fish is caught directly from river Nile or cultured in a specified aquaculture. Organochlorine pesticides (OCPs) have been extensively used in Egypt and many African countries in the past century for the control of the agricultural pests. A major character of OCPs is their persistent bio-accumulation in the environment, especially in the food chain, where they can get reach to humans. There is few reports had investigated the current scenario of OCPs contamination in fish in Egypt, particularly in Upper Egypt cities such as Sohag. Additionally, fish is consumed cooked in Egypt not raw like many Asian countries. Therefore, this study aimed at monitoring the residue levels of different OCPs in tilapia fish caught from Upper Egypt (Sohag) and compared with either that from northern part of Egypt (Damietta) or with fish cultured in a control location (Abbasa). Additionally, the effect of different cooking methods (boiling, grilling and pan-frying) on the residue levels of OCPs was investigated. The tested OCPs included pp-DDT and its metabolites pp-DDD and pp-DDE; hexachlorohexanes (HCHs) including α HCH and γ HCH; heptachlor and heptachlor epoxide; aldrin and endrin; chlordane, methoxychlor and hexachloride benzene and were detected using electron capture gas chromatography equipped with Ni63 – electron capture detector. The recorded results revealed that tilapia collected from Damietta had the highest incidence of OCPs’ contamination (75%), over than that collected from Sohag (60%) compared to control value (35%). All examined samples had OCPs residues within the maximum permissible limits (MPLs) set by world health organization. Pan-frying had the highest reduction effect on the OCPs’ residues followed by grilling and boiling. The public health significance of the examined OCPs was also discussed.

Determinants of pesticide concentrations in silicone wristbands worn by Latina adolescent girls in a California farmworker community: The COSECHA youth participatory action study

Personal exposure to pesticides has not been well characterized, especially among adolescents. We used silicone wristbands to assess pesticide exposure in 14 to 16 year old Latina girls (N = 97) living in the agricultural Salinas Valley, California, USA and enrolled in the COSECHA (CHAMACOS of Salinas Examining Chemicals in Homes and Agriculture) Study, a youth participatory action study in an agricultural region of California. We determined pesticide concentrations (ng/g/day) in silicone wristbands worn for one week using gas chromatography electron capture detection and employed gas chromatography mass spectrometry to determine the presence or absence of over 1500 chemicals. Predictors of pesticide detections and concentrations were identified using logistic regression, Wilcoxon rank sum tests, and Tobit regression models. The most frequently detected pesticides in wristbands were fipronil sulfide (87%), cypermethrin (56%), dichlorodiphenyldichloroethylene (DDE) (56%), dacthal (53%), and trans-permethrin (52%). Living within 100 m of active agricultural fields, having carpeting in the home, and having an exterminator treat the home in the past six months were associated with higher odds of detecting certain pesticides. Permethrin concentrations were lower for participants who cleaned their homes daily (GM: 1.9 vs. 6.8 ng/g/day, p = 0.01). In multivariable regression models, participants with doormats in the entryway of their home had lower concentrations (p < 0.05) of cypermethrin (87%), permethrin (99%), fipronil sulfide (69%) and DDE (75%). The results suggest that both nearby agricultural pesticide use and individual behaviors are associated with pesticide exposures.

Observing the atmospheric evolution of ozone-depleting substances

The atmospheric observations of ozone-depleting substances (ODSs) have been essential for following their atmospheric response to the production and use restrictions imposed by the Montreal Protocol and its Amendments and Adjustments. ODSs have been used since the first half of the 20th century in industrial and domestic applications. However, their atmospheric growth went unnoticed until the early 1970s, when they were discovered using gas chromatograph-electron capture detection (GC-ECD) instruments. Similar instrumentation formed the basis of global flask and in situ measurements commenced by NOAA and ALE/GAGE/AGAGE in the late 1970s. The combination of these networks, supported by a number of other laboratories, has been essential for following the tropospheric trends of ODSs. Additionally, ground-based remote sensing measurements within NDACC and aircraft-based observation programs have been crucial for measuring the evolution of the ODS abundances over the entire atmosphere. Maintaining these networks at least at their current state is vital for ensuring the on-going verification of the success of the Montreal Protocol.

Detection of halogenated hydrocarbon pollutants using enzymatic reflectance biosensor

A reflectometric biosensor for enzymatic determination of halogenated organic pollutant in environmental water sample was developed. Polyacrylate microspheres modified with succinimide functional groups were employed as the substrate matrix for covalent immobilization of haloalkane dehalogenase (DhlA) enzyme, and ETH5294 Nile Blue chromoionophore (NBC) pH dye was physically immobilized on the acrylic micromatrix to function as an optical proton sensor. The hydrolytic dehalogenation of halocarbon catalyzed by the immobilized DhlA resulting in the release of a halogen and a proton, which protonated the immobilized NBC proton indicator, and a colour change of the biosensor from violet to blue was measured with a reflectance spectrophotometer for indirect quantification of the halogenated hydrocarbon concentration. The enzymatic halocarbon reflectance biosensor exhibited a dynamic linear response range of 1–30 mg L−1 1,2-dichloroethane (DCA) (R2 = 0.9762) with a detection limit of 0.3 mg L−1. The proposed enzymatic biosensor gave rapid response, within 2 min, towards the detection of 50 mg L−1 DCA at 662 nm, and demonstrated stable response up to 6 days of storage period at 4 °C and pH 8.0. Validation between the developed biosensor with standard gas chromatography–electron capture detector (GC-ECD) showed that both methods have a comparable accuracy in detecting halocarbon species.

Organochlorine pesticide residues in sediment and water from Nairobi River, Kenya: levels, distribution, and ecological risk assessment.

Production and use of most organochlorine pesticides (OCPs) was banned through the Stockholm Convention on persistent organic pollutants. However, appreciable amounts are still detected in the environment due to their persistence, illegal use, and releases from contaminated soils and obsolete stocks. The present study investigated the levels of OCP residues in Nairobi River. Sediment and water samples were collected from three sites along the river and screened for 17 OCPs using gas chromatography electron capture detector (GC-ECD). Mean pesticide residues ranged from 0.01 to 41.9μgkg-1 in sediment and below detection limit to 39.7ngL-1 in water. In sediment α-HCH, β-HCH, γ-HCH, heptachlor epoxide, and p,p'-DDD were detected in all samples, while α-HCH, γ-HCH, δ-HCH, heptachlor epoxide, endosulfan I, and endrin were detected in all water samples. Levels of OCPs in water were below the WHO maximum allowable limits for surface water. However, values higher than the sediment quality guidelines for sediment samples in Racecourse Road Bridge and Outering Road Bridge were reported, thus confirming the toxicity to aquatic organisms. Consequently, as these compounds are known to bio-accumulate in fatty tissues, continued use of the river water poses a health risk to animals and humans.

Bioremediation of hexachlorocyclohexane (HCH) in soil using spent mushroom compost of Pleurotus ostreatus

Hexachlorocyclohexane (HCH), a highly chlorinated pesticide, was used worldwide in the 1950s and 1960s. HCH toxic residues are still detected in environmental compartments. Thus, effective, viable and eco-friendly strategy is required for its remediation. In this study, degradation of four HCH isomers was evaluated by amending contaminated soil using four treatments of spent mushroom compost (SMC) of Pleurotus ostraetus. The soil was incubated for 5 weeks and was sampled every seven days. Quantitative attenuation in HCH was calculated using gas chromatography–electron capture detector (GC-ECD) and metabolite was identified using gas chromatography–mass selective detector (GC-MSD). Maximum reduction 58%, 26%, 45%, and 64% for α-, β-, γ- and δ-HCH isomers, respectively, using SMC and soil (both unsterilized) showed that this treatment was the best for bioremediation of HCH in soil. However, when one of the factors, either soil or SMC, was sterilized, a significant reduction in HCH degradation was noticed. The second most reduction of isomers was seen during treatment where unsterilized SMC was added in sterilized soil followed by treatment where SMC was sterilized but soil was not. Abiotic control did not remove any significant quantities of HCH. Simple first-order (SFO) kinetic confirmed that SMC reduced the half-live manifolds as compared to biotic control. Only one metabolite δ-PCCH was identified during the course of study.

Detection of Organochlorine Pesticide (OCPs) Residues and Trace Metals in Some Selected Malt Drinks in Nigeria

In this study we evaluated the trace metals and toxic residues of pesticides in commercial malta drinks sold in Nigeria markets. Residual concentrations of seventeen (17) chlorinated hydrocarbons and trace metals were determined in fifteen samples of three batches each of five selected brands of Malta drink sold in Nigeria markets. Gas Chromatograph-Electron Capture Detector (GC-ECD) and Atomic Absorption Spectrophotometry (AAS) were employed in quantitative analysis. The results revealed that all the malt drink analyzed have one or more OCPs detected. The presence of eleven (11) OCPs residue were detected at varying concentrations. The total burden of OCPs in the samples was in the following order: AMS &gt; DUB &gt; MAG &gt; HIM &gt; MLT. Trace metals results revealed that Cd was below detection limit in all the samples while Pb; Ni and Cr were above World Health Organization and United State Environmental Protection Agency (WHO/USEPA) limits for drinking water.