Conical Centrifuge Tube Research Articles

Age-dependent effects of acute stress on the behavior, blood parameters, immunity, and enteric nerves of mice

The impact of stress on mental and digestive health has been extensively studied, with chronic stress being associated with various disorders. However, age-related differences in the response to acute stress, both behaviorally and physiologically, remain poorly understood. Therefore, this study aimed to develop a model to detect transient stress in mice of different ages. The stressor employed in our experiments was a restraint stress procedure, where mice were subjected to brief periods of immobilization to induce an acute stress response. Male C3H/HeN mice aged 3, 6, 12, and 30 weeks were subjected to acute restrain stress (ARS) by being placed in a 50 ml conical centrifuge tube for 15 min. Subsequently, their behavior, organ tissues, hematological parameters, cortisol concentration, and immune responses were assessed. Following ARS, the increased in time and entries into the center by the 12-week-old mice following stress. In comparison to mice of other ages, those aged 6 weeks demonstrated notable elevations in erythrocytes, platelets, hemoglobin, and hematocrit, all of which were influenced by the time-dependent changes and the recovery process of ARS. Blood corticosterone levels were substantially elevated in all age groups after ARS. Furthermore, ARS induced a notable increase in leukocytes, basophils, residential macrophages, and CD4+ T cells in all age groups except for 3-week-old mice. However, the number of monocyte-derived macrophages and CD8+ T cells did not change significantly. Additionally, mice aged 3 and 6 weeks demonstrated an increase in GFAP+ cells following ARS, whereas NeuN+ cells decreased across all ages. These results suggest that ARS has varying effects on the behavior, cortisol concentration, and quantity of blood cells as well as hepatic immune cells in mice of different ages. These age-dependent responses shed light on the complex interplay between stress and physiological systems and contribute to the broader understanding of stress-related diseases.

Small-Scale Cultivation and Transfection of ExpiCHO and HEK293E Cells in Single-Use Orbitally Shaken Bioreactors.

Chinese hamster ovary (CHO) and human embryonic kidney 293 (HEK293) cells are the two most important mammalian hosts for the production of recombinant proteins. In this chapter, the suspension cultivation and transfection of these cells in small-scale, single-use orbitally shaken bioreactors, TubeSpin™ bioreactor 50 [orbitally shaken reactor 50 (OSR50)], and TubeSpin™ bioreactor 600 [orbitally shaken reactor 600 (OSR600)] are described. These are conical centrifuge tubes with nominal volumes of 50mL and 600mL, respectively, that have been redesigned with a ventilated cap for the cultivation of animal cells in suspension at working volumes up to 20mL and 400mL, respectively.

Detection and Quantification of X and Y sperms in Enriched Sahiwal Semen diluted in PBS using Raman Spectroscopy

The present study was undertaken to enrich X-sperms in Sahiwal bull semen by percoll density gradient method and to detect X and Y sperms in enriched semen by Raman spectroscopy. The experiment was performed at Semen Production Centre, CVASc, GBPUAT, Pantnagar, Uttarakhand. Ejaculates were collected by AV method from Sahiwal bull. X-sperm enrichment was done by the Percoll density gradient method. Three types of gradients were prepared i.e. 7 layers (70-10%), 7 layers (80-20%) and 3 layers (30%, 50% and 70%). Semen (1ml or 3ml) was placed over the gradient in a conical centrifuge tube. Centrifugation was done at 750 g (22-24°C) for 15 min. The pellets thus obtained were diluted in PBS medium. Raman spectroscopy was performed in different groups viz. fresh semen (Control), 3 layers (70%, 50% and 30% GI), 7 layers (70-10% GII), and 7 layers (80-20% GIII). Raman peaks (DNA specific) were not much clear for PBS diluted semen samples though intensities were highest for 7 layers (70-10%) among all groups. Thus semen enriched by the percoll-density gradient method (7 layers i.e. 70-10%) can be used to increase female calf birth after A.I.

Frequency of Leaks from Conical Centrifuge Tubes.

Threaded conical centrifuge tubes are ubiquitous in biological laboratories and are frequently used for the storage/transport of potentially biohazardous samples. However, limited data are available on how frequently and from where these tubes leak. These data are valuable for laboratory biorisk management and to inform future studies on risks arising from the routine use of laboratory consumables. The frequency of leaks from threaded conical centrifuge tubes was tested using a Glo Germ solution as a tracer. Conical tubes (15 and 50 mL) from several brands were filled, inverted, and placed on their side on the benchtop. After 1 h, the presence or absence of leaks on the benchtop surface, tube threads, and exterior was recorded. We observed that liquid leaked out of tubes that were apparently properly threaded in 2% of 15 mL tubes (confidence interval [95% CI] 1.4-2.6) and 1.4% of 50 mL tubes (95% CI 0.2-1.5). After opening, liquid was found on the threads on the outside of the tube in 20% of 15 mL tubes (95% CI 10-31) and 14% of 50 mL tubes (95% CI 1-28). We did not find sufficient evidence that differences in leak rates among brands were practically significant. The fact that leaks were not uncommonly observed from conical centrifuge tubes suggests that mitigations for any hazard posed by a leak should be a component of every biorisk management strategy for protocols involving the manipulation of hazardous substances in these tubes. Further research should be conducted on other activities that could cause tubes to leak (such as centrifugation or vortexing) and should be completed to understand the risks associated with this consumable. Research into the costs and benefits of mitigating the risk of leaks from conical tubes is recommended.

Effect of Aging on Hardness of Glass Ionomer, Resin-Modified Glass Ionomer, Giomer and Compomer Dental Restorative Materials

Objective: To assess deionized water's aging effect on the hardness of four direct tooth colored dental filling materials i.e., Glass Ionomer Cement, Resin Modified Glass Ionomer, Giomer and Compomer.Study Design: An in vitro experimental study performed in triplicates.Place and Duration of Study: The study was carried out at PG Laboratory, Department of Science of Dental Materials, Army Medical College, Rawalpindi, Pakistan from February 2023 to August 2023.Methods: Three disc-shaped samples (n=3) of 10 mm diameter and 1 mm thickness of each restorative material were prepared using stainless steel molds per manufacturer's instructions. These disc-shaped samples were then suspended in a 15 mL conical centrifuge tube containing 10 mL deionized water, followed by incubation in a Forced Convection Laboratory Oven at 37 C where these were allowed to age over a period of 1-2 years. Vickers Hardness of each sample was then checked at two-time intervals, i.e., after 24 h setting and after 2.5 years of ageing through the Micro Vickers Hardness Tester calibrated at 1Kgf (9.80 N) with dwell time of 10 seconds and light intensity 10. Results: After one day (24 h) aging in deionized water, maximum mean Vickers hardness number (VHN) was exhibited by Compomer (539.83±58.08 VHN) and least by GIC (175.75±24.47 VHN). After aging the sample for 912 days, maximum mean VHN was observed for GIC (420.67±99.66 VHN) and least by Compomer (354.33±9.22 VHN). Conclusion: RMGIC sustains its hardness on aging, hardness of GIC increases while that of Giomer and Compomer decreases upon aging.
 How to cite this: Gul H, Nayyer M, Junaid Y, Pasha M, Ejaz T, Liaqat U, Hassan SH. Effect of Aging on Hardness of Glass Ionomer, ResinModified Glass Ionomer, Giomer and Compomer Dental Restorative Materials. Life and Science. 2023; 4(4): 438-444. doi: http://doi.org/10.37185/LnS.1.1.437

Endoparasites of Leopardus pardalis (Carnivora, Felidae) rescued in the State of Rio de Janeiro.

Wild cats play an important role as top predators in the food chain and act as ecosystem regulators. However, in recent decades, many studies have demonstrated the potential effects of parasitic diseases on wild carnivore populations, including cats. This study reports on the endoparasites found in an injured and rescued specimen of Leopardus pardalis in the state of Rio de Janeiro. Fecal samples were collected and processed using five coproparasitological techniques: a simple flotation centrifugation, a zinc sulfate flotation centrifugation, a formalin-ether sedimentation centrifugation, a conical centrifuge tube technique, and a modified Ziehl-Neelsen staining technique for fecal smears. Helminth eggs belonging to the families Trichuridae and Diphyllobothriidae and the genus Toxocara were found in both sedimentation flotation techniques. Protozoan oocysts belonging to the genus Cryptosporidium were identified by modified Ziehl-Neelsen staining. These findings show that ocelots can harbor potentially zoonotic and pathogenic endoparasites. Further studies on the helminths and protofauna of these animals are necessary.

Artificial Membrane Feeding Mosquitoes in the Laboratory with Glytube.

Artificial membrane feeders are devices that replace vertebrate hosts when blood feeding mosquitoes. Created using readily available materials found in mosquito laboratories, Glytube is one of the simplest artificial membrane feeders that scientists can use to provide a blood meal to female mosquitoes in the laboratory. Glytube was optimized for blood feeding the main epidemiologically important species, such as Aedes aegypti, Aedes albopictus, Culex quinquefasciatus, and Anopheles aquasalis Although the Glytube can be used without modifications to blood feed mosquito females, some researchers have modified the device to improve its assembly and to adapt it to different feeding assays that do not involve a basic blood meal, broadening its utility. Here, I describe how to transform a 50-mL conical centrifuge tube into a convenient, versatile, and cost-effective artificial membrane blood feeder.

Membrane Feeding Devices to Blood Feed Mosquitoes in the Laboratory.

Husbandry protocols for medically important mosquito species in the laboratory have the blood feeding procedure as an inherent step in the maintenance routine for egg production. Artificial feeders have become the main solution for delivering blood meals to these hematophagous insects, circumventing the need for vertebrate hosts. Mimicking the skin, these devices both heat the blood and hold a membrane through which the blood can be ingested by mosquitoes. Several commercial and noncommercial artificial mosquito feeders are available, but obstacles like high cost and complex assembly can restrict their routine use. To address this issue, a number of feeders have been designed that can be built with common materials found in the laboratory. They are cheaper and more accessible, but the absence of built-in temperature control and heating units can limit their efficacy. One of the most accessible mosquito feeders is the Glytube. It consists of a 50-mL conical centrifuge tube with heated glycerol that delivers blood through a membrane. The Glytube has been used successfully to model mosquito blood feeding. Recently, 3D printing has emerged as an alternative method to create customized artificial feeders. This technology is expected to facilitate access to and reduce the cost of these devices with open-source 3D model files that can be shared among laboratories maintaining mosquitoes worldwide.

Ultrasonic-assisted preparation of eucalyptus oil nanoemulsion: Process optimization, in vitro digestive stability, and anti-Escherichia coli activity

Eucalyptus oil (EO) is a natural and effective antimicrobial agent; however, it has disadvantages such as poor water solubility and instability. The aim of this study was to investigate the effect of process vessels and preparation process parameters on the particle size of the emulsion droplets using ultrasonic technique and response surface methodology to prepare eucalyptus oil nanoemulsion (EONE). The optimal sonication process parameters in conical centrifuge tubes were confirmed: sonication distance of 0.9 cm, sonication amplitude of 18%, and sonication time of 2 min. Under these conditions, the particle size of EONE was 18.96 ± 4.66 nm, the polydispersity index was 0.39 ± 0.09, and the zeta potential was −31.17 ± 2.15 mV. In addition, the changes in particle size, potential, micromorphology, and anti-Escherichia coli activity of EONE during digestion were investigated by in vitro simulated digestion. The emulsion was stable in simulated salivary fluid, tended to aggregate in simulated gastric fluid, and increased in particle size and potential value in simulated intestinal fluid. EONE showed higher anti-E. coli activity than EO by simulated digestion. These results provide a useful reference for the in vivo antimicrobial application of the essential oil.

Entomopathogenic nematode dispensing robot: NEMABOT

Entomopathogenic nematodes (EPN) are obligate endoparasites of many insect species and they are important biocontrol agents. Application strategies that improve precision and reduce labor would increase their potential in many cropping systems. We developed a unique robotic system to apply EPNs to a surface area precisely. The robotic system picks up EPNs from a suspension in a reservoir with a peristaltic pump and transfers them to an exact point with an exact amount. Four suspensions were prepared with four concentrations of EPNs; 0.1, 0.2, 0.4 and 0.8 g of commercial EPN product per 2 L of water. All suspensions were applied in three different amounts of water (25, 50 and 100 mL per application). In total, 12 different applications were conducted with the robot. Conical falcon centrifuge tubes were used to collect applied EPNs. Five samples (10 µl) were taken from collected 25, 50 and 100 mL EPN suspensions and the average nematode number in the samples were scaled to the whole suspension. Results of the experiments showed that all robot applications, except 25 mL–0.1 g dose, were not significantly different from those of the control treatment, application with a pipette.. Thus, the robotic system has been found to make consistent applications.

201 Effect of mild restraint stress on lipopolysaccharide-induced preterm labor in murine model

Prenatal stress leads to a pro-inflammatory state that may prime the immune system to respond aggressively to bacterial stimuli. This robust inflammatory response may be a mechanism for preterm delivery in individuals with high levels of chronic stress. The objective of this study was to assess the impact of antenatal stress on the responsivity of mice to lipopolysaccharide (LPS)-induced preterm labor. Nulliparous mice (n=39) underwent timed breeding at 8-10 weeks of age. Dams were then randomly assigned to either stress or control groups. The mice assigned to stress underwent daily 2-hour periods of restraint in a ventilated clear 50-mL conical centrifuge tube from E1-E15. On E15.5, mice from each group were randomly assigned to a 150-microliter intraperitoneal injection with either 15 micrograms LPS (E. coli O111:B4) or phosphate buffered saline (PBS). This low dose of LPS typically induces preterm labor in about 50% of mice. Mice were monitored in individual cages for the next 48 hours. The primary outcome was the number of dams exhibiting preterm labor (defined as bleeding or delivery of at least 1 fetus) within 48 hours. Mice were then sacrificed and uterine gross pathology inspected. Secondary outcomes were maternal death and presence of resorbed fetuses in the uteri. Outcomes were compared with Fisher’s Exact Test with a significant p-value of .05. In total, 10/10 of the mice exposed to antenatal stress and 7/12 of the control mice demonstrated preterm labor when exposed to low-dose LPS (Figure 1). Fisher’s Exact Test showed the rate of preterm labor after low-dose LPS injection was significantly higher in mice exposed to antenatal stress (p=.04). There were no maternal deaths observed. Two mice in the control-PBS group demonstrated resorbed fetuses. None of the other groups demonstrated resorbed fetuses (p=.52). Chronic mild restraint stress increases the sensitivity of mice to low-dose LPS-induced preterm labor. These data provide insight into a potential cause of increased preterm delivery rates among populations experiencing high rates of chronic stress.

202 Effect of mild chronic restraint stress on gestational weight gain in murine model

To assess the effect of restraint stress on gestational weight gain in a murine model. Nulliparous female mice, divided among C57BL/6 (n=14), DBA/2 (n=11), and B6D2F1/J (n=9) strains were bred at 8-10 weeks of age with B6D2F1/J males. Detection of a copulation plug was used to determine embryonic day (E) 0.5. Dams were then randomly assigned to either stress or control groups. The mice assigned to stress underwent daily 2-hour periods of restraint in a ventilated clear 50-mL conical centrifuge tube from E1.5-E15.5. The primary outcome was the difference between weight on day E15.5 compared to day E0.5. Pregnancy was confirmed by either preterm delivery from E15.5-E17.5 or by inspection of the uterus after sacrifice on E17.5. Mean weight gain for each strain was compared between the control and stress groups using independent sample t-tests. Values of p < .05 were considered statistically significant. Mean gestational weight gain is presented in Figure 1. DBA/2 and B6D2F1/J mice exposed to restraint stress demonstrated significantly lower gestational weight gain than their respective controls (p=.001 and p=.005, respectively). There was not a significant difference in gestational weight gain in stressed C57BL/6 mice compared to controls (p=.70). Mild chronic restraint stress results in decreased gestational weight gain in DBA/2 and B6D2F1/J mice but not in C57BL/6 mice.

Influence of Pine Bark Tannin on Bacterial Pathogens Growth and Nitrogen Compounds on Changes in Composted Poultry Litter

ABSTRACT To study the antimicrobial and uric acid-preserving activity of pine bark tannin on poultry litter composting, antibiotic-free wood chip-based poultry litter was distributed (11 g) to 50-mL conical centrifuge tubes and immediately amended with 1.3 mL0.4 M sodium phosphate buffer (control) or with 1.3 mL condensed tannins from pine bark (Pinus palustris; 9 % tannin wt/vol in water). All tubes (n = 3 tubes/treatment) were inoculated with a novobiocin and naladixic acid-resistant Salmo-nella typhimurium (STNN) to achieve 3.0 log10 CFU/g and incubated at 37oC for 3 days to simulate an initial compost period. Wildtype E. coli and the challenge STNN strain as well as concentrations of ammonia, uric acid and urea were measured on days 0 and 3. Pine bark tannin treatment decreased (p 0.05). Ammonia accumulation decreased (p 0.05). Results suggest that pine bark tannin treatment may preserve uric acid and reduce ammonia volatilization in composted litter while aiding Salmonella control.

Resveratrol Protects against Restraint Stress Effects on Stomach and Spleen in Adult Male Mice.

Simple SummaryThe current project was designed to examine the effects of restraint stress on body weights, food and water consumption, and pathophysiology of the stomach and spleen in adult mice, and potential roles of the phenolic compound resveratrol during treatment. We found that restraint stress (which is known to be a mixture of psychologic and physical stress) caused a reduction in body weight, food and water consumption, and morphologic changes in the stomach and spleen, which could lead to gastritis or ulcers and splenomegaly, while treatment with resveratrol prevented the negative alterations to the stomach and spleen.The objectives were to investigate whether restraint stress (which is known as a mixture of psychologic and physical stress) exerts negative effects on the stomach and spleen, and whether the phenolic compound resveratrol (RES) exerts any protective roles. Fifty adult male mice were divided into five groups, with 10 mice per group as follows: control (C), restraint stress (RS), RS with vehicle (RS + V), RS with 2 mg/kg of resveratrol (RS + 2 mg RES), and RS with 20 mg/kg of resveratrol (RS + 20 mg RES). Mice were restrained in conical centrifuge tubes for 4 h daily to establish the RS model. RS + 2 mg RES, RS + 20 mg RES, and RS + V groups were given an oral dose of resveratrol or vehicle for 15 consecutive days, while the control group was not exposed to restraint stress. Herein, we showed that restraint stress decreased body weight and food and water consumption in stressed groups RS and RS + V compared to controls, while the groups treated with resveratrol showed improvements. Moreover, restraint stress caused acute damage to the morphology of gastric cells and reduced the quantitative distribution of parietal cells along with their decreased size and diameter, pointing to gastritis or ulcer. Furthermore, the antibody against the apoptosis-inducing factor (AIF) was highly attached in the RS groups. Splenic size, weight, and length were also greatly augmented in the stressed groups compared to the controls, while these phenomena were not observed in the RS + 2 mg RES group. Our findings proved significant ameliorating effects of resveratrol against restraint stress in adult male mice.

Ultrasound-assisted Solid-liquid Trap Phase Extraction based on Functionalized Multi Wall Carbon Nanotubes for Preconcentration and Separation of Nickel in Petrochemical Waste Water

In this study, a novel sorbent based on phenylsulfonic acid functionalized multiwall carbon nanotubes (MWCNTs-Ph-SO3H) was used for preconcentration and separation of trace Ni(II) ions in petrochemical wastewater samples by ultrasound-assisted solid-liquid trap phase extraction. In this work, a mixture of MWCNTs-Ph-SO3H as a nanosorbent and ionic liquid (1-hexyl-3-methylimidazolium hexafluorophosphate, IL) dispersed in acetone was rapidly injected by a syringe into 50 mL of a sample containing Ni(II). The metal was extracted by sulfonate group as (RSO3)2-Ni at optimized pH. After shaking and centrifuging, the nanoparticles of sorbent were trapped in IL phase and settled down in a conical centrifuge tube (IL/MWCNTs-Ph-SO3H). Hydrophobic IL was used to fast trap the Ni(II) loaded sorbent from the sample solution. Under the optimized conditions, the linear range (peak area), limit of detection and enrichment factor were obtained as 1.5–165 μg/L, 0.35 μg/L and 50, respectively.

A new enzymatic method for extracting diatoms from organs of suspected drowning cases using papain: Optimal digestion and first practical application

Diatom analysis is very effective for positive diagnosis of water inhalation in drowning. However, conventional strong acid diatom testing is laborious and potentially dangerous. We propose a simple, fast, and safe protocol using inexpensive reagents such as papain, SDS, and 5 N HCl for extracting diatoms from lung, kidney, and liver tissues. First, we determined optimal conditions for papain digestion using porcine tissues. Papain digestion was clearly superior to Proteinase K digestion. Next, for assessing the assay effectiveness in practical cases, the papain digestion protocol was applied to 80 tissue samples from 20 suspected drowning victims. Left and right lung tissues (1 g each) were digested in 15-mL conical centrifuge tubes. Kidney and liver tissues (10 g each) were extracted in 175-mL conical centrifuge bottles. Papain dissolved all organs sufficiently and permitted clear visualization of diatoms, although papain’s solubilization activity was still inferior to strong acid digestion. The proposed enzymatic method requires only a low-speed centrifuge and water bath. Diatoms typically can be extracted from tissue samples within 3–5 h. The cost of protease is reduced some 6-fold by using papain in place of Proteinase K. Thus, the proposed method can be useful as a less-laborious, less-hazardous, and less-costly minimal test when the conventional strong acid digestion method is not performed due to personnel, equipment, budgetary limitation, or environmental and safety considerations.

A lead analysis based on amine functionalized bimodal mesoporous silica nanoparticles in human biological samples by ultrasound assisted-ionic liquid trap-micro solid phase extraction

A simple and applied method based on ultrasound assisted-Ionic liquid trap-micro solid phase extraction (USA-ILT-μSPE) was demonstrated for preconcentration/separation of lead (Pb) in human blood and urine samples. By proposed method, the amine-functionalized bimodal mesoporous silica nanoparticles (NH2-UVM7) as solid phase sorbent was used for lead analysis in human biological samples at pH ≈ 7.0. After shaking/centrifuging of sample, the Pb (II) was extracted with NH2-UVM7 without any chelating agents, trapped in ionic liquid phase and settled down in conical centrifuge tube as a residual solution [Pb→:NH2-UVM7]. Finally, the lead ions was back extracted from residual solution and determined by atom trap flame atomic absorption spectrometry (AT-FAAS). Under the optimal conditions, the linear range (LR), limit of detection (LOD) and preconcentration factor (PF) were obtained (10–950 μg L−1; 2.0–210 μg L−1), (2.8 μg L−1; 0.6 μg L−1) and (19.8; 99.7) for human blood and urine samples, respectively (% RSD < 1, intra-day). The reusability and adsorption capacity of the sorbent were also obtained 24 and 213.8 mg g−1, respectively. Validation of methodology was confirmed by certified reference materials (NIST, CRM).

Microbiota Modulate Anxiety-Like Behavior and Endocrine Abnormalities in Hypothalamic-Pituitary-Adrenal Axis.

Intestinal microbes are an important system in the human body, with significant effects on behavior. An increasing body of research indicates that intestinal microbes affect brain function and neurogenesis, including sensitivity to stress. To investigate the effects of microbial colonization on behavior, we examined behavioral changes associated with hormones and hormone receptors in the hypothalamic-pituitary-adrenal (HPA) axis under stress. We tested germ-free (GF) mice and specific pathogen-free (SPF) mice, divided into four groups. A chronic restraint stress (CRS) protocol was utilized to induce external pressure in two stress groups by restraining mice in a conical centrifuge tube for 4 h per day for 21 days. After CRS, Initially, GF restraint-stressed mice explored more time than SPF restraint-stressed mice in the center and total distance of the OFT. Moreover, the CRH, ACTH, CORT, and ALD levels in HPA axis of GF restraint-stressed mice exhibited a significantly greater increase than those of SPF restraint-stressed mice. Finally, the Crhr1 mRNA levels of GF CRS mice were increased compared with SPF CRS mice. However, the Nr3c2 mRNA levels of GF CRS mice were decreased compared with SPF CRS mice. All results revealed that SPF mice exhibited more anxiety-like behavior than GF mice under the same external stress. Moreover, we also found that GF mice exhibited significant differences in, hormones, and hormone receptors compared with SPF mice. In conclusion, Imbalances of the HPA axis caused by intestinal microbes could affect the neuroendocrine system in the brain, resulting in an anxiety-like behavioral phenotype. This study suggested that intervention into intestinal microflora may provide a new approach for treating stress-related diseases.

Extraction and preconcentration of triazine pesticides using rapid, simple, and disperser solventless microextraction technique followed by gas chromatography–nitrogen phosphorous detection

In this study, a simple, rapid, and efficient microextraction method followed by gas chromatography–nitrogen‐phosphorous detection has been applied for the extraction, preconcentration and determination of some triazine pesticides in edible oil samples. In this method, initially the oil sample is dissolved in hexane and then a few microliter of a less soluble organic solvent in hexane (extraction solvent) is added. The mixture is rapidly aspirated into a glass syringe and then is injected into a conical centrifuge tube for predetermined cycles to form a cloudy solution. Some experimental parameters that influence the extraction efficiency, such as type and volume of the extraction solvent, extraction numbers, and centrifuging rate and time are examined and optimized. Under optimum extraction conditions, the method showed low limits of detection and quantification between 0.02 to 0.09 and 0.07 to 0.30 μg/L, respectively. Extraction recoveries were in the range of 74–96%.Practical applications:This paper describes an analytical method that can be used by oil manufacturers for quality control purposes. A disperser solventless microextraction method and GC‐NPD were used to monitor triazine pesticides in different edible oils and propazine was found in corn oil.Triazine pesticides often contaminate the seeds and hence will be transferred into the oils during the extraction process. For trace determination of triazines in edible oil, 1 mL edible oil was diluted with 4 mL n‐hexane in conical tube and 40 µL DMSO was added. The mixture was rapidly aspirated into a 10‐mL glass syringe and then injected into the tube (4 times) to form a cloudy solution. The method showed low limits of detection and quantification between 0.02 to 0.09 and 0.07 to 0.30 µg/L, respectively. Extraction recoveries were in the range of 74–96%.

DESENVOLVIMENTO DE AMOSTRADOR PASSIVO SENSÍVEL PARA MONITORAMENTO DE POLUIÇÃO ATMOSFÉRICA POR DIÓXIDO DE NITROGÊNIO

A passive sampler constructed with a new type of material and used for measurement of ambient nitrogen dioxide is presented. The sampler was constructed with parts of two 50 mL conical centrifuge tubes. The procedure is based on NO2 uptaken on cellulose filter impregnated with triethanolamine. After sampling, the analyte is solubilized and placed to react with Griess-Saltzman solution. The absorbance of the formed complex is determined at 540 nm. A mean relative standard deviation of 9,72% was obtained using samplers exposed in triplicate, and a determination coefficient (R-2) of 0,979 was achieved in parallel measurements using the samplers and a commercial NOx monitor. Advantages of the technique include ease of use, the ready availability of components, and excellent sensitivity.