Gas Chromatography Equipped With Electron Capture Detector Research Articles

Levels of select organophosphates in human colostrum and mature milk samples in rural region of Faizabad district, Uttar Pradesh, India

Human colostrum and mature milk samples from rural mothers were separately screened for organophosphate pesticides (OPPs). The samples were assessed for the pollution load they are transmitting to the nursing infant to determine potential toxicity. The role of colostrum for toxicity monitoring was assessed in comparison to mature milk as it is the very first infant food. The pesticides were quantified using a Gas Chromatograph equipped with Electron Capture Detector (GC-ECD) and the results were further validated on GC linked with Mass Spectrophotometer (GC-MS) and Fourier transform infrared (FTIR). A total of 33 samples were analyzed out of 40 samples collected. These samples were from 33 mothers. Out of these, 25 were colostrum samples and 8 were mature milk samples. Frequency percentage (N%) of organophosphates analyzed was highest for ethion (23.1% or 6/26) in colostrum and chlorpyrifos (50% or 4/8) in mature milk samples. Frequency percentage in colostrum was 19.2% (5/26) for chlorpyrifos and 3.8% (1/26) for dimethoate; 25.0% (2/8) mature milk samples carried dimethoate and 12.5% (1/8) carried ethion. Mean OPPs in colostrum: dimethoate (85.888 ng/g fat) > ethion (48.000 ng/g fat) > chlorpyrifos (4.003 ng/g fat); and mature milk: ethion (744.925 ng/g fat) > chlorpyrifos (37.274 ng/g fat) > dimethoate (26.752 ng/g fat). MS data revealed the presence of methyl parathion, which was not quantitated. None of the samples exceeded acceptable daily intake standards set by Joint Meeting on Pesticide Residues (JMPR). The study will pave way for further analysis on pesticide toxicology.

Effect of Light Intensity on the Photodegradation of PCB 153 in Aqueous Solution using UV and UV/H2O2

This study examines the photodegradation of PCB 153 under ultraviolet radiation and ultraviolet radiation combined with hydrogen peroxide (H2O2) using a batch tubular recirculating photoreactor equipped with 17 W and 24 W UV-C lamps emitting at 254 nm.PCB 153 solutions with various concentration of 50 ppb, 80 ppb and 100 ppb were prepared for experiments conducted under photolysis (UV only) while 25 μL (0.221 mM), 50 μL (0.441 mM), 75 μL (0.662 mM) of 30% (w/w) H2O2 were individually added to an 80 ppb PCB 153 solution and used as samples for UV/H2O2 experimental runs. Under ultraviolet radiation, the increase of light intensity from 17 W to 24 W increased the degradation from 90.43% to 94.71% of an 80 ppb aqueous PCB 153 solution after 2 hrs of irradiation. The addition of 50 μL (0.441 mM) of 30% wt H2O2 resulted into a drastic decrease of the same concentration of PCB 153. After 30 minutes of irradiation using 17 W UV lamp, 95.95% PCB degradation was observed while complete degradation was attained with the 24 W UV lamp. The pH of the solutions was closely monitored and it was observed that it decreases during photodegration. The decrease of the sample's pH was a result of inorganic chlorides and acidic metabolites formation as measured using High Performance Liquid Chromatography (HPLC) - Conductivity Detector. Likewise, the PCB concentration of irradiated samples was measured using Gas Chromatography equipped with Electron Capture Detector (GC-ECD).

Levels of pesticide residues in irrigation effluent from tomato fields in Owiro Estate, Tanzania

Pesticide residues lindane, chlorpyrifos and endosulfan sulphate were detected in water from the spring source, within field and return channel of vegetable farms in Ngarenanyuki, Tanzania. Extraction of the pesticide residues were conducted by liquid-liquid extraction (LLE) method. The detection and concentrations of pesticide residues were determined by gas chromatography equipped with electron capture detector (GCECD). The percentage detections in return channel and within field were observed to be 67 and 33 respectively whereas no pesticides were detected in the spring source. The average concentrations for lindane, chlorpyrifos and endosulfan sulphate within field and return channel were 3.0, 0.27 and 3.35, and 2.8, 0.06 and 3.13 mg/L, respectively. Absence of residues detection in spring source indicates that the source of pesticides in water from the field and return channel were the applications of pesticides in vegetable farms. This work, thus, seeks to provide information on levels of pesticide residues in water that will assist in a scientific assessment of the impact of pesticides application on public health and ecosystem in Tanzania.Keywords: Organochlorines, Organophosphorous, Water contamination, Ngarenanyuki.

A Method for Quantifying Azoxystrobin Residues in Grapes and Soil Using GC with Electron Capture Detection

A relatively simple method for the determination of azoxystrobin residues in grapes and soil using gas chromatography equipped with electron capture detector (GC-ECD) is described. Samples were extracted with acetone, and further partitioned with dichloromethane and petroleum ether. The extracts were then cleaned up in a glass clean-up column filled with active charcoal and silica gel, and eluted with dichloromethane/ethyl acetate (70:30, v/v). The eluate was collected and concentrated for GC-ECD analysis. The results showed good linearity (r2 = 0.9998) over the concentration range of 6.25–400 ng mL−1. The limits of detection (LOD) and quantification (LOQ) of azoxystrobin were 3 and 10 ng mL−1. Recovery from soil and grape samples was in the range of 83.52–107.36 and 82.21–107.31%, with corresponding relative standard deviations (RSD) of 5.21–9.11 and 4.53–5.90% for the three fortified levels. Inter- and intra-day RSDs were in the range of 0.87–6.76 and 2.01–5.46%. The accuracy and sensitivity of the GC-ECD method was independently confirmed by LC and GC-MS. It was demonstrated that the proposed method was simple and efficient, and particularly suitable for detecting azoxystrobin residues in grapes and soil.

High throughput method for the determination of organochlorine pesticides and polychlorinated biphenyls in human serum

An improved method for the determination of selected organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) in human serum was developed. The method requires low volume of serum (500 μl) and 48–96 samples per day can be prepared by one analyst without special automatic equipment. Initial extraction was performed using 96-well solid-phase extraction disk plates and was followed by a clean-up with silica gel/sulfuric acid. Different denaturation, elution and clean-up conditions were tested. Quantification was carried out by gas chromatography equipped with electron capture detector (GC-ECD) or mass spectrometer (GC–MS). Recoveries of PCB congeners 28, 52, 101, 118, 138, 153 and 180 and OCPs HCB, β-HCH, p, p′-DDE and p, p′-DDT at two spiking levels ( n = 8) varied from 57 to 120%, and intra-day relative standard deviation from 1 to 11%, both depending on spiking level and compound. Inter-day relative standard deviation was <15% in all cases. Limit of quantification (LOQ) for these PCBs ranged from 0.08 to 0.13 ng/ml and for these OCPs from 0.16 to 0.40 ng/ml. The optimized method was applied to the analysis of 1000 serum samples from different places of Spain.

Residues of Diazinon in Growing Chinese cabbage: A study Under Greenhouse Conditions

Chinese cabbage, Braccica campestris has long been consumed as a staple food for Koreans in various forms of fresh, salted, and fermented Kimchi. Cultivation of the crop under greenhouse has become a general practices to fulfill its off-seasonal consumer's demand. However, agricultural practices of the crop have always accompanied with heavy applications of pesticides caused by severe outbreaks of diseases and pose under warm and humid circumferences. Since dissipation patterns of pesticide residues in/on the crop under greenhouse conditions ate quite different from those in the open-air, changes of diazinon, O,O-diethyl O-2-isopropyl-6-methylpyrimidin-4-yl phosphornthioate, in/on the Chinese cabbage applied by foliar spraying under greenhouse were studied. Diazinon 34% EC was applied with dilution of recommended and double dose to the crop. The shoots of crop were harvested immediately after this application and at regular intervals over a 10-day. After sample preparations, the diazinon residue was analyzed using gas chromatography equipped with electron capture detector (GC/ECD). Initially deposited amount of the chemical in/on the crop right after applications with recommended and double doses were 8.3 and 15.2 mg/kg, respectively. The residue levels after 10 days of application were 0.03 and 0.09 mg/kg with 1.3 and 1.5 days of half-life in/on the crop, respectively. In consequent 10 days of pre-harvest interval (PHI) for diazinon EC formulation in/on Chinese cabbage under greenhouse condition was fulfill maximum residue level set by Korea Food and Drug Administration (KFDA, 0.1 mg/kg).

Microwave-assisted extraction or saponification combined with microwave-assisted decomposition applied in pretreatment of soil or mussel samples for the determination of polychlorinated biphenyls

Three microwave-assisted techniques (MAT), namely microwave-assisted extraction (MAE), microwave-assisted saponification (MAS) and microwave-assisted decomposition (MAD), were studied and combined to be used in the samples pretreatment to determine polychlorinated biphenyls (PCBs) in soil, sediment and mussels. MAE was employed for the isolation of PCBs, MAS for the saponification of a mussel matrix, and MAD for the elimination of some organochlorine pesticides (OCPs) such as hexachlorocyclohexane (BHC) and DDT, which usually coexisted with PCBs in environmental samples. It was found that acetone- n-hexane (1:1, v/v), methanol and methanolic 1 M KOH solution were all good extractants for MAE of PCBs (recovery >83%), and 15 g mussel could be completely saponified with 30 ml of methanolic 1 M KOH or ethanolic KOH solution by 2 min microwave heating at 100% power output of 600 W. Moreover, 30 ml methanolic 1 M KOH or ethanolic 1 M KOH solution and 2 min microwave heating brought about a complete decomposition for each of 2∼4 μg α-BHC, β-BHC, γ-BHC, δ-BHC, o- p-DDT, p- p-DDT and p- p-DDD, while p- p-DDE, aldrin and dieldrin could only be partly degraded. Furthermore, compared with that by MAD in methanolic 1 M KOH solution, the degradation products of OCPs by MAD in methanolic 1 M KOH solution yielded more peaks in the chromatogram obtained by gas chromatography equipped with electron capture detector (GC-ECD), which may interfere with the GC-ECD detection of PCBs. Therefore, methanolic 1 M KOH solution was chosen as the extractant for the pretreatment of soil or sediment. As a result, the MAD of OCPs could occur along with the MAE of PCBs. Similarly, the MAD of OCPs could well coincide with the MAS of mussels when methanolic 1 M KOH solution was employed as the saponifier for the pretreatment of mussels. Thus, isolating the analytical targets and eliminating the coexisting interferents could be simultaneously carried out using the combined MAT. In addition, it was found that PCBs are quite stable under the optimized conditions during both the MAE-MAD and MAS-MAD procedures.

Environmental and Biological Monitoring of Organochlorine Residues after the Plague Epidemic in Surat, India - A Preliminary Study

In late August 1994, an outbreak of human pneumonic/bubonic plague was reported in Surat, India. During the epidemic, large amounts of pesticides, such as benzene-hexachloride (BHC) and other organochlorinated compounds were used to control the vector that might have transmitted the plague. In order to evaluate the extent of contamination, both environmental samples (9 water samples and 4 soil samples) and biological samples (5 blood and urine samples) were collected and analyzed for organochlorine residues. Samples were analyzed after hexane extraction by gas chromatography equipped with electron capture detector (GC-ECD), using a PTE-5 capillary column. The results showed that the levels of 1,1′-(2,2-dichloroethenylidene)-bis[4-chlorobenzene] (DDE), a major metabolite of DDT, were low in environmental samples (water, soil), while BHC levels were relatively high in one of the water sample as well as two soil samples. The BHC and DDE levels in the biological samples were not higher than those reported earlier from India, except for serum DDE. Further studies are needed to evaluate the effect of long-term exposure as the present study was based on limited samples.