Decontamination of fenitrothion from aqueous solutions using rGO/MoS2/Fe3O4 magnetic nanosorbent: synthesis, characterization and removal application.

In the present work, rGO/MoS2/Fe3O4 nanocomposite was synthesized and after confirmation of the structure by FTIR, XRD, and FESEM techniques, its performance as nanosorbent was investigated for the removal of fenitrothion pesticide from the aqueous media. The parameters affecting the removal process including agitation time, pH of the reaction medium, adsorbent content, initial analyte concentration as well as desorption parameters were investigated and optimized. Under optimum conditions (pH = 7, adsorbent amount: 30 mg, adsorption and desorption time: 5 min, eluent type and volume: 0.01 M ethanol-acetic acid and 4 mL), the synthesized adsorbent was able to remove fenitrothion pesticide up to 98% with an adsorption capacity of 33.4 mg/g. By investigation of the line equation and the correlation coefficient value, it was found that the adsorption process, in this study, follows the Langmuir model.

Determination of trace amounts of zearalenone in beverage samples with an electrochemical sensor.

A simple and sensitive electrochemical sensor is purposed for the preconcentration and determination of zearalenone using a carbon paste electrode modified with multi-walled carbon nanotubes. A differential pulse voltammetric method is employed to study the behavior of zearalenone on this modified electrode. The analytical procedure consists of a closed-circuit accumulation step onto the modified electrode. An anodic peak, related to the oxidation of accumulated and reduced zearalenone on the electrode surface, was observed at 0.40 V. The calibration curve was linear in the range of 2.0-50.0 ng mL(-1). The limit of detection was found to be 0.58 ng mL(-1), and the relative standard deviations for five replicated determinations at 5.0 and 30.0 ng mL(-1) of zearalenone were 2.71 and 1.44%, respectively. The modified electrode was applied successfully for the analysis of zearalenone in different malt beverage samples.

In vitro evaluation of the effect of core thickness and fabrication stages on the marginal accuracy of an all-ceramic system.

OBJECTIVE: To evaluate the influence of core thickness and fabrication stages on the marginal accuracy of IPS e.max Press crowns. MATERIALS AND METHODS: Twenty IPS e.max Press crowns, 1.5mm thick, were fabricated on metal dies. The crowns had two different core thicknesses, 0.8mm for group A and 1mm for group B, ten for each group. Marginal gap was measured after each stage of core fabrication, veneering and glaze firing. The specimens were not cemented and the measurements were made at four points on metal dies using a stereomicroscope (×120). Data were analyzed by SPSS software and independent t-test. RESULTS: Mean marginal gaps measured after each stage for group A were 13.5 (±1.4) µm, 33.9 (±2.3) µm and 40.5(±1.7) µm, and for group B these figures were 14.9(±2.0) µm, 35.5(±2.2) µm and 41.3(±2.0) µm. There were no statistically significant differences in marginal gap values between the two groups (p>0.1). Significant increase in gap was observed after the veneering stage in both groups (p<0.05). After glazing, no significant increase in gap was detected. CONCLUSION: IPS e.max Press crowns have an acceptable marginal fit. Increasing thickness of core does not increase marginal fitness.

A novel solidified floating organic drop microextraction based on ultrasound-dispersion for separation and preconcentration of palladium in aqueous samples.

A new method of solidified floating organic drop microextraction, based on ultrasound-dispersion prior to flame atomic absorption spectrometry was successfully used for separation and enrichment of trace amounts of palladium in aqueous samples. In this method, palladium (II) was extracted into the fine droplets of 1-undecanol after chelate formation with the water soluble ligand, ammonium pyrrolidinedithiocarbamate. The fine droplets of 1-undecanol were made and dispersed as a cloud in the aqueous sample with the help of ultrasonic waves. Several variable factors that influence the extraction and complex formation, such as pH, concentration of ammonium pyrrolidinedithiocarbamate, sonication time, centrifuging time, type and volume of the extracting solvent were optimized. Under the optimized conditions, a detection limit of 0.60 ng mL(-1) and a good relative standard deviation of +/-2% at 10 ng mL(-1) were obtained (n=7). The proposed method was applied to well water, tap water, wastewater and synthetic samples and spiked recoveries were in the range of 97-105%. The results showed that solidified floating organic drop microextraction based on ultrasound-dispersion combined with flame atomic absorption spectrometry was a rapid, simple, sensitive, low cost, minimum organic solvent consumption and efficient analytical method for the separation and determination of trace amounts of palladium ion.

Flame atomic absorption spectrometry determination of trace amounts of copper after separation and preconcentration onto TDMBAC-treated analcime pyrocatechol-immobilized.

A simple and reliable method has been developed for green separation and preconcentration of trace amounts of copper ions in aqueous solutions for subsequent measurement by flame atomic absorption spectrometry (FAAS). The Cu(2+) ions are adsorbed selectively and quantitatively during the passage of an aqueous solution through TDMBAC-treated analcime pyrocatechol-immobilized. The retained copper ions were desorbed from the column with 5.0mL of 4mol L(-1) nitric acid solutions as eluent and were determined by FAAS. The linear range was 0.2-75ng mL(-1) in the original solution with a correlation coefficient of 0.9987. In this case we can concentrate 0.1microg of copper from 1000mL of solution and the proposed method permits a large enrichment factor (about 200). The detection limit of the proposed method is 0.05ng mL(-1) in the original solution (2sigma(bl)). Determination of copper in standard alloys showed that the proposed method has good accuracy (recovery was more than 97%). The method was successfully applied for recovery and determination of copper in several water samples.

Débridement and closed packing for the treatment of necrotizing pancreatitis.

OBJECTIVE: To evaluate the results of débridement and closed packing for necrotizing pancreatitis and to determine the optimal timing of surgical intervention based on patient outcomes. METHODS: Between February 1990 and November 1996, 64 consecutive patients with necrotizing pancreatitis were treated with necrosectomy followed by closed packing of the cavity with stuffed Penrose and closed suction drains. The mean APACHE II score immediately before surgery was 9, and 31% of the patients had organ failure. Patients were stratified with an outcome score based on death and major complications; this was correlated with the timing of surgical intervention. The data were then subjected to cut-point analysis by sequential group comparison. RESULTS: Patients underwent surgery a median of 31 days after diagnosis. Fifty-six percent had infected necrosis. The mortality rate was 6.2% and was no different in infected or sterile necrosis. Eleven patients required a second surgical procedure and 13 required percutaneous drainage; a single surgical procedure sufficed in 69%. Enteric fistulae occurred in 16% of patients. The mean hospital stay after surgery was 41 days, and the interval until return to regular activities was 147 days. A significant negative correlation between duration of pancreatitis and outcome scores was found, and sequential group comparison demonstrated that the change point at which significantly better outcomes were encountered was day 27. CONCLUSION: Débridement of pancreatic necrosis followed by closed packing and drainage is accomplished with a low mortality rate and reduced rates of complications and second surgical procedures. Although intervention is best deferred until the demarcation of necrosis is complete, delay beyond the fourth week confers no additional advantage.

Effect of computed tomography of the appendix on treatment of patients and use of hospital resources.

BACKGROUND: In patients with clinically suspected appendicitis, computed tomography (CT) is diagnostically accurate. However, the effect of routine CT of the appendix on the treatment of such patients and the use of hospital resources is unknown. METHODS: We performed appendiceal CT on 100 consecutive patients in the emergency department who, on the basis of history, physical examination, and laboratory results, were to be hospitalized for observation for suspected appendicitis or for urgent appendectomy. Outcomes were determined at surgery and by pathological examination in 59 patients, and by clinical follow-up two months later in 41 patients. Treatment plans made before CT were compared with the patients' actual treatment. We also determined the costs of surgery that revealed no appendicitis (from data on 61 patients), one day of observation in the hospital (from data on 350 patient-days in patients with suspected appendicitis), and appendiceal CT (from data on all pelvic CT examinations in 1996). RESULTS: Fifty-three patients had appendicitis, and 47 did not. The interpretations of the appendiceal CT scans were 98 percent accurate. The results of CT led to changes in the treatment of 59 patients. These changes resulted in the prevention of unnecessary appendectomy in 13 patients, admission to the hospital for observation in 18 patients, admission to the hospital for observation before necessary appendectomy in 21 patients, and admission to the hospital for observation before the diagnosis of other conditions by CT in 11 patients. The effects of performing appendiceal CT on the use of hospital resources included the prevention of unnecessary appendectomy in 13 patients (for a savings of $47,281) and the prevention of unnecessary hospital admission for 50 patient-days (for a savings of $20,250). After the cost of 100 appendiceal CT studies ($22,800) was subtracted, the overall savings was $447 per patient. CONCLUSIONS: Routine appendiceal CT performed in patients who present with suspected appendicitis improves patient care and reduces the use of hospital resources.

Helical CT combined with contrast material administered only through the colon for imaging of suspected appendicitis.

OBJECTIVE: Helical CT combined with contrast material administered by mouth and through the colon has been shown to be accurate for appendiceal imaging. This investigation was performed to determine if helical CT combined with contrast material administered only through the colon has comparable accuracy. SUBJECTS AND METHODS: One hundred patients prospectively underwent appendiceal CT imaging with thin-collimation, helical scanning limited to the lower abdomen and upper pelvis after contrast material was administered only through the colon. CT results were correlated with surgical and pathologic findings at appendectomy (56 patients), other surgery (three patients), or clinical follow-up at least 2 months after the CT scan (41 patients). RESULTS: Fifty-three CT scans were interpreted as positive for appendicitis, including 52 true-positives (with surgical-pathologic correlation) and on false-positive (with clinical follow-up). Forty-seven CT scans were interpreted as negative for appendicitis, including 40 true-negatives with clinical follow-up, three true-negatives with appendectomy and pathologic correlation, three true-negatives with other surgery and pathologic correlation, and one false-negative with appendectomy and pathologic correlation. CT had a 98% sensitivity, 98% specificity, 98% positive predictive value, 98% negative predictive value, and 98% accuracy for diagnosing or excluding appendicitis. In 47 normal appendix cases at CT, the appendix was seen in 44 cases (94%), and an alternative diagnosis was identified in 29 cases (62%). CONCLUSION: For diagnosing appendicitis, helical CT combined with contrast material administered only through the colon proved to be as accurate (98%) as helical CT combined with contrast material administered by mouth and through the colon. Helical CT with contrast material administered only through the colon also could be performed immediately and without any of the potential patient risks or discomforts of contrast material administered i.v. or by mouth.