Microwave Procedure Research Articles

RAPID AND EFFICIENT GENERATION OF PCR TEMPLATES FROM ESCHERICHIA COLI, SACCHAROMYCES CEREVISIAE AND ORYZA SATIVA USING A MICROWAVE AND BY BOILING

ABSTRACT Simple methods for the preparation of polymerase chain reaction (PCR) templates from Escherichia coli, Saccharomyces cerevisiae and Oryza sativa using a microwave and by boiling are described without the need for any special chemical reagent such as a detergent. The microwave and boiling methods were robust for the preparation of both plasmid and genomic templates of E. coli, as was the boiling approach for S. cerevisiae DNA. The microwave procedure was only suitable for dry yeast colonies with fair efficiency as absence of water (H2O) was critical for a successful PCR. Oryza sativa genomic DNA was amplified with both approaches with satisfactory efficiency. Escherichia coli plasmids can be prepared using a microwave with a yield equivalent to 15–20% of an alkaline lysis mini‐prep. PCR templates were also efficiently generated from Pichia pastoris and Ganoderma lucidum by using the boiling method.

Cloud-Point Extraction for Selective Removal of Gd(III) and La(III) with 8-Hydroxyquinoline

:A less-common extraction procedure, cloud-point extraction, is used with a lipophilic chelating agent (8-hydroxyquinoline) to extract and separate lanthanum(III) and gadolinium(lll) ions from an aqueous solution. Surfactant solutions are used in conjunction with 8-hydroxyquinoline to form a lanthanide complex that is extracted into the micellar phase at a temperature above the cloud-point temperature. The structure of the lipophilic part of the nonionic surfactant, the chelating agent-metal molar ratio, and the cloud-point temperature are identified as factors determining the extraction efficiency and selectivity. With Triton X-114, a selectivity higher than 30 and a decontamination factor of 50 for Gd(IlI) indicate that micelle-mediated cloud-point extraction is promising for the specific separation of actinide ions from nuclear waste. Finally, a microwave procedure is proposed to decrease the duration of the experiment to less than 6 min.

Microwave-assisted sequential extraction of fly ash : Studies on chemical speciation of zinc, copper, arsenic and manganese

Coal fly ash due to its light weight and better mobility, is a significant solid pollutant. A sequential extraction procedure has been applied to determine the environmental mobility of zinc, copper, arsenic and manganesein fly ash. The original procedure of Tessier et al. has been modified using the microwave-assisted technique. The results obtained by summation of extractahle amounts of copper, arsenic and manganese obtained in each step by the microwave procedure range from 88 to 99% of the total content, by microwave-assisted method, as compared to the standard non-certified value of NIST fly ash. For zinc, however, we obtain 117% of the metal content, by microwave-assisted method, as compared to the standard non-certified value of NIST fly ash. The elemental analyses of the individual leachates have been done by flame atomic absorption spectrometry and hydride generation atomic absorption spectroscopy. A drastic reduction in time viz. from 68 h in the original Tessier to <3.5 h in the microwave-assisted method has been obtained.

Comparison of Sample Preparation Procedures for the Determination of Trace Heavy Metals in House Dust, Tobacco and Tea Samples by Atomic Absorption Spectrometry

The effect of wet ashing, dry ashing and microwave procedure for the determination of trace metal levels was investigated in house dust, tobacco and tea samples by atomic absorption spectrometry. The study of sample preparation procedures showed that the microwave method was the best. The recovery of trace metals was very good and precision and accuracy were compatible with standard reference material. The relative standard deviations for all measured metal concentrations were lower than 10%. The digestions of HNO3/H2SO4/HClO4 (4: 1: 1) mixture for house dust, HNO3/H2SO4/H2O2 (2: 2: 2) mixture for tea and HNO3/H2O2 (4: 2) mixture for tobacco were very efficient.

Synthesis by microwave irradiation of a substituted benzoxazine parallel library with preferential relaxant activity for guinea pig trachealis

An efficient, facile, and practical parallel combinatorial synthesis of substituted-benzoxazines under microwave irradiation was described. The procedure involved the use of a microwave oven especially designed for organic synthesis suitable for parallel synthesis of solution libraries. A demonstration 19-membered library of substituted N,N-dimethyl- and N-methyl-benzoxazine amide derivatives, structurally related to the potassium channel opener cromakalim, was generated by both conventional and microwave procedures, achieving a reduction from 7 h to 30–36 min in library generation time for the microwave approach. All the synthesized compounds were tested using the in vitro models of rat aorta and guinea pig trachea rings pre-contracted with phenylephrine and carbachol, respectively. All N,N-dimethyl amide derivatives showed a relaxant activity higher on guinea pig trachea rings than on rat aorta rings.

BOTULINUM TOXIN TYPE A: A NOVEL APPROACH TO THE TREATMENT OF RECURRENT URETHRAL STRICTURES

Recently, investigators have demonstrated that botulinum toxin type A (BTX-A) can be used to prevent scar formation in facial wounds.1 This concept led us to investigate the treatment of recurrent urethral stricture scars using a combination of direct visual internal urethrotomy (DVIU) and BTX-A. MATERIALS AND METHODS Three patients with a history of posterior urethral stricture disease who had undergone failed DVIU were treated with repeat DVIU in combination with BTX-A injection. Etiologies for urethral strictures included radical retropubic prostatectomy in 2 patients with prostate cancer, and Targis microwave procedure (Urologix, Inc., Minneapolis, Minnesota) for benign prostatic hyperplasia in 1. All patients had a combination of stress urinary incontinence and recurrent urethral strictures diagnosed by videourodynamics and cystoscopy, respectively. Intraoperatively, each stricture was radially incised through the fibrous tissue in 4 quadrants until bleeding tissue was reached and a 21Fr or greater cystoscope could be easily passed into the bladder. Using a 25 gauge Williams needle 100 units BTX-A diluted in 2 ml preservative-free saline was injected circumferentially at the base of the scar into the intervening areas between the incisions (fig. 1). All patients had a catheter placed at the end of the procedure that was left indwelling for 2 to 5 days. Patients returned at approximately 4 to 6 weeks for repeat cystoscopy. On repeat cystoscopy a 21Fr cystoscope easily passed through the previous stricture site in 2 of 3 patients, each of whom later underwent successful placement of an artificial urinary sphincter (AUS) to treat the stress urinary incontinence. Nine months following DVIU plus BTX-A injection cystoscopy revealed continued patency of the posterior urethra in 1 patient who had undergone implantation of an AUS (fig. 2). Long-term urethral patency of the other AUS implant was confirmed during operative revision of the AUS 12 months after DVIU plus BTX-A injection. The third patient, who previously had undergone radical retropubic prostatectomy complicated by an anastomotic urinary stricture, had a moderate recurrence of the scar following DVIU plus BTX-A treatment. Repeat cystoscopy 6 weeks postoperatively showed an approximately 10Fr to 12Fr caliber urethral lumen. An 18-week followup cystoscopy demonstrated no further diminution in urethral caliber. Nine months after stricture incision and BTX-A injection the patient continues to void to completion without straining or the need to catheterize.

Improved Microwave Imaging Procedure for Nondestructive Evaluations of Two-Dimensional Structures

An improved microwave procedure for detecting defects in dielectric structures is proposed. The procedure is based on the integral equations of the inverse scattering problem. A hybrid genetic algorithm (GA) is applied in order to minimize the obtained nonlinear functional. Since in nondestructive evaluations the unperturbed object is completely known, it is possible off-line to numerically compute the Green's function for the configuration without defects. Consequently, a very significant computation saving is obtained, since the chromosome of the GA codes only the parameters describing the unknown defect.

Microwave-assisted [3 + 2] cycloadditions of azomethine ylides.

The microwave-assisted intramolecular [3 + 2] cycloaddition reaction of azomethine ylides to activated and nonactivated alkenes and alkynes is described. The procedure allows the synthesis of pyrrolidines and pyrrole products in good to excellent overall yields in short reaction times. It appears from parallel comparative studies that the microwave procedure favors the reaction times and overall purity of the crude reaction mixture. The reactions can also be performed in the absence of solvent. [reaction: see text]

A comparison among different instrumental approaches for bromide analysis in foodstuffs digested by a suitably modified microwave procedure

Cathodic stripping voltammetry (CSV), ion-chromatography (IC) and spectrophotometry (SP) have been tested as instrumental approaches alternative to inductively coupled plasma mass spectrometry (ICP-MS) for the determination of inorganic bromide residues in foodstuffs fumigated with brominated pesticides and digested by a suitably improved microwave procedure proposed previously. They were chosen in view of the fact that the relevant instrumentation is less expensive than that required for ICP-MS and more frequently available in analytical laboratories designed for routine food control. These approaches were compared with one another, as well as with the ICP-MS method previously adopted, not only with regard to their performance, but also in terms of the interferences caused by the composition of final samples coming from the microwave digestion procedure. The results found pointed out unambiguously that IC turns out to be well suited for replacing ICP-MS, thanks to its consistency with the composition of digested samples and its good sensitivity which allows a quite low detection limit for bromides (0.2 mg kg −1) to be achieved. Conversely, CSV and SP performance appears to be significantly affected by interferences caused by the presence in digested samples of chlorides and ammonium ions, respectively.

Effect of cooking on oxalate content of pulses using an enzymatic procedure

An enzymatic method proposed for the determination of oxalate in urine is adapted for the estimation of soluble oxalate content in beans, chickpeas and lentils. Oxalates were extracted in water by refluxing for 2 h. The method is based on the oxidation of oxalate by the oxidase and the determination of the resulting hydrogen peroxide, which in presence of peroxidase, 3-methyl-2 benzotiazinolone and 3-dimethylamino benzoic, gives an indamine compound with an absorption maximum at 590 nm. The linearity (from 0.015 to 0.6 mM) of the method is adequate to the analysis of oxalate contents in pulses, and the inter-day precision of the method expressed as relative standard deviation was good (3.01%), with an accuracy of (98.7±2.5%) estimated by recovery assays. This method is applied to estimate the losses of soluble oxalate as a consequence of cooking. All the cooking procedures reduce the soluble oxalate content, but microwave and industrial procedures are more effective than traditional domestic cooking.

Determination of several elements in duplicate meals from catering establishments using closed vessel microwave digestion with inductively coupled plasma mass spectrometry detection: estimation of daily dietary intake

An estimation of the dietary exposure of French consumers to 21 essential and non-essential mineral elements using duplicate meals (breakfast and lunch) purchased from catering establishments was investigated after digestion by a closed vessel microwave procedure and quantification by ICP-MS. Daily dietary exposure estimates for metals and minerals were compared with the Provisional Tolerable Weekly Intakes (PTWI), the Tolerable Daily Intake (TDI) or the Acceptable Daily Intakes (ADI), as established by the FAO/WHO to estimate the risk of toxicity, and the US Recommended Daily Allowances (US RDA) or the Estimate Safe & Adequate Daily Dietary Intakes (ESADDI). Moreover, comparisons were made with those from previous French studies as well as those from other countries. The estimated mean daily intakes were 11 μg for lithium, 3.42 g for sodium, 192 mg for magnesium, 2.03 mg for aluminium, 3.64 g for potassium, 642 mg for calcium, 154 μg for chromium, 12.3 mg for iron, 2.15 mg for manganese, 4 μg for cobalt, 74 μg for nickel, 925 μg for copper, 10.2 mg for zinc, 147 μg for arsenic, 66 μg for selenium, 112 μg for molybdenum, 3.6 μg for cadmium, 2.32 mg for tin, 3 μg for antimony, 9 μg for mercury and 34 μg for lead. For the non-essential (toxic) elements, aluminium, tin, antimony, cadmium, arsenic, mercury and lead, the daily intake estimates were far below tolerable limits; and similar or somewhat lower than their respective PTWI, ADI, TDI, ESADDI and US RDA for individual minerals and essential trace elements, with good agreement with other country studies. The performance of the multi-elemental ICP-MS technique was also evaluated.

A COMPARISON OF SAMPLE PREPARATION PROCEDURES FOR THE DETERMINATION OF HEAVY METALS IN LICHEN SAMPLES BY GFAAS

ABSTRACT The effect of wet ashing, dry ashing and microwave procedure for the determination of heavy metal (Pb, Cd, Fe, Cu, Mn and Zn) levels was investigated in Lichen samples by GFAAS. The study of sample preparation procedures showed that the microwave method was the best. The recovery of heavy metals was very good and precision and accuracy were compatible with standard reference materials. Palladium and aluminum sulfate were used as a modifier.

Comparison between Total Determination and Extractable Heavy Metals from River Sediments using Conventional and Microwave Accelerated Leaching Tests

In the present study the concentration of heavy metals (Cu, Cr, Ni, Pb and Zn) in sediments collected from different sampling stations of the Leça river (Portugal) was determined, using Flame Atomic Absorption Spectrometry. In order to estimate the potential mobility of metals in these samples, the results of the total digestion were compared with those obtained by single extractions using EDTA and acetic acid as extractant solutions; in all samples studied, Cu and Zn were found to be the most mobile elements; Ni and Pb showed a smaller mobility in presence of either acidic medium and complexing ligands; Cr was found the least mobilizable element, given that the low extractability obtained with the two extractants tested in this work. In the single extraction tests, microwave energy was also employed to replace the conventional treatment and only in the case of the EDTA the results obtained were similar to those of the conventional procedure (recoveries between 90.16 and 98.76%); the precision (RSD, n=3) of the proposed microwave procedure for EDTA extractions was comparable to those of the conventional method with values always lower than 8% for all metals.

CO–CH 4 selectivity enhancement by in situ Pd-catalysed microwave SnO 2 nanoparticles for gas detectors using active filter

Nanosized tin oxide powders were obtained using microwave procedure for their application on gas sensor technology. This technology allows taking advantage of low cost and high volume mass production for the easy in situ introduction of the palladium catalytic additive. The effects of a controlled high palladium catalysation, reaching active filter properties, are reported showing an enhancement of the selectivity for CO and CH 4. In this work, electrical results of the sensor performances are discussed and correlated with their structural parameters and the used technological procedures. Especial emphasis has been devoted to the active filter efficiency deduced from CO consumption measurements. The applicability to the present state of the art in sensor technology of such active-filter catalysed SnO 2 is shown by means of its implementation in micromachined substrates operated in pulsed mode.

Combined osmotic and microwave-vacuum dehydration of apples and strawberries

The combination of osmotic pre-treatment – mainly in sucrose solutions – and microwave-vacuum dehydration of strawberries and apples has been studied. Water removal during osmotic treatment is accompanied by solute uptake from the osmotic solution. The resulting changes in composition bring about better properties of the final product in terms of structure and volume. Compared to the solely microwave-vacuum dried samples, osmotic pre-treatment improved volume retention from 20% to 50% (strawberries) and from approximately 20% to 60% (apples) based on the fresh volume. SEM pictures revealed that the cellular structure is also preserved better, when osmotic pre-treatment is used. Gel formation between pectins, sucrose and in some cases, calcium ions is believed to be the main cause of structure build-up. Vitamin C retention was around 60% with the microwave procedure applied here.

Use of microwave single extractions for metal fractionation in sewage sludge samples

In the present study the original Tessier sequential extraction method has been applied for metal fractionation in sewage sludge samples collected from an urban wastewater treatment plant and from one domestic olive oil factory. The results obtained by this conventional method were compared with those estimated from direct microwave single extractions, in order to reduce the conventional treatment time and simplify the experimental task. Microwave extraction conditions (heating time and power) were specifically optimised for Cu, Cr, Ni, Pb and Zn with the aim of obtaining similar results to that of the original Tessier method. Extractable metal contents obtained by both compared methodologies were measured by flame atomic absorption spectrometry (FAAS). In the three first fractions of the Tessier method, the analytical results were similar to those obtained from microwave single extractions for most of the elements in the two samples studied. In contrast, the fourth fraction could not be directly extracted using the microwave procedure and must be leached from the solid residue of the reducible fraction, using a two-step procedure. The overall extraction efficiency obtained by both single and sequential microwave extractions were similar for all metals (recoveries between 93.9 and 102.3%), except for Cu in the two samples studied and for Cr in the olive oil sludge (OOS) (recoveries <32%). The precision of the proposed microwave single extraction method was <8.5% for all metals in the two samples.

A crack identification microwave procedure based on a genetic algorithm for nondestructive testing

This paper is aimed at exploring the possibility of using a microwave approach based on a genetic algorithm to detect a defect inside a known host object. Starting from the knowledge of the scattered field, the problem solution is recast as a two-step procedure. After defining a cost function depending on the geometric parameters of the crack, a minimization procedure based on a hybrid-coded genetic algorithm is applied. The influence of the noise as well as of the geometry of the defect on the crack detection and reconstruction is investigated. Moreover, the numerical effectiveness of the iterative approach is examined.

Microwave digestion of "residual fuel oil" (NIST SRM 1634b) for the determination of trace elements by inductively coupled plasma-mass spectrometry.

A microwave procedure for the digestion of the NIST 1634b reference material "residual fuel oil" in closed pressurized vessels was developed in an attempt to facilitate routine analysis and obtain reproducible conditions or comparable results. The influence of sample size, reagent composition and volume, microwave power, and duration of heating on the digestion procedure was studied. Pressure and temperature inside the reaction vessels were monitored to determine the progression of the reaction and to develop optimal conditions. A nine-step heating program requiring 36.5 min with microwave power not exceeding 450 W in the pulsed mode was found suitable for the digestion of approximately 250 mg fuel oil with a mixture of nitric acid (5.0 mL) and hydrogen peroxide (2.0 mL). The reproducibility of microwave power was determined in terms of the relative standard deviations (n = 3) for temperature (2.7%) and pressure (4.9%) data. The vapor pressures obtained with 5.0 mL Milli-Q water (heated) in an 80-mL digestion vessel showed good agreement with literature data. The excess acid in the resulting digests was removed by evaporation and the concentrations of 24 elements (Ag, Al, As, Ba, Bi, Ca, Cd, Co, Cr, Cu, Fe, Hg, Mg, Mo, Ni, Pb, Sb, Sn, Sr, Ti, Tl, V, U, and Zn) were determined in the diluted digests by inductively coupled plasma mass spectrometry (ICP-MS). The experimental results were in good agreement with the certified and recommended concentrations for eight elements (Al, As, Co, Cr, Ni, Pb, V, Zn) in solutions obtained after one digestion step. An additional digestion step, consisting of intermediate cooling and venting stages, was required for the accurate determination of Fe. No agreement was reached for Ca and Ba even after two-step digestion. The proposed method of digestion provided precise results with relative standard deviations generally less than 5% for most of the elements determined.

Determination of trace elements and calcium in bone of the human iliac crest by atomic absorption spectrometry

A rapid and reliable analytical method for the determination of trace elements in human bone by atomic absorption spectrometry is reported. Calcium was determined to estimate the homogeneity of samples. Human bone from the iliac crest was obtained at autopsy of adult subjects. Before analysis samples were decomposed by microwave digestion and acid digestion in a Parr bomb. Zinc, rubidium, strontium, calcium and iron were determined by flame atomic absorption spectrometry (FAAS) and aluminium, copper and lead by electrothermal atomic absorption spectrometry (ETAAS) at optimum measurement conditions. The results for the two digestion procedures agreed for zinc, rubidium and calcium within ±5%, for copper within ±7% and for strontium, iron, aluminium and lead within ±10%. The repeatability of measurement (R.S.D.) for determination of calcium and trace elements after microwave digestion and acid digestion in a Parr bomb was tested in one representative autopsy bone sample by six parallel determinations. It was found to be better than ±5% either for microwave digested samples or samples digested in a Parr bomb, for all elements determined by FAAS and ETAAS techniques. The accuracy of the applied digestion procedures was checked by analysis of trace elements in NIST SRM 1486 Bone Meal reference material. Good agreement of the results with certified values was obtained for both digestion procedures. The microwave procedure developed for digestion of small amounts of sample was applied in trace elements analysis of bone biopsy samples from dialysis patients.

Comparison of sample digestion procedures for the determination of trace elements in antarctic krill by GF‐AAS

Two independent digestion procedures for Antarctic krill samples were compared. Dry ashing (DA) and microwave (MW) acid‐assisted digestion were tested for decomposing the samples to determine essential (Cu, Fe, Cr) and toxic elements (Cd, Pb) by graphite furnace‐atomic absorption spectrometry (GF‐AAS). A mixture of HNO3 and H2O2 as digesting agent was used in the microwave procedure. For the dry ashing digestion, the organic matter was oxidated at 480°C in an open system. Both digestion methods were compared in terms of accuracy and applied to the analysis of a certified reference material: MURST‐ISS‐A2 (Antarctic krill). The detection limits for the five elements analysed ranged from 3 to 150 ng g‐1. Both digestion procedures are suitable for the decomposition of krill samples. However, dry ashing is not recommended to determine Pb and Cd because losses can occur.