SEARCH · PubMed Health

Results for “Distillation”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,369 records · Page 76Linked to original sources

PubMed2004

Two-phase partition chromatography using soybean oil eliminates pesticide residues in aqueous ginseng extract.

This study was carried out to develop a cost-, labor- and efficiency-effective elimination method of pesticide residues in ginseng extract. A two-phase partition method between soybean oil and distilled water or aqueous ginseng extract was employed for the elimination of pesticide residues. Content of the pesticides was determined by gas chromatography with electron capture or nitrogen phosphorus detector. A total of 15 pesticides representing four categories (organochlorine, organophosphorus, carbamate, pyrethroid) were spiked (ca. 2 ppm) to 2 ml soybean oil in a test tube and the oil was mixed with 6 ml distilled water or 10% aqueous ginseng extract. The test tubes were then vortexed (2 min) and centrifuged at 3000 rpm for 15 min to separate the oil and aqueous layers. Each layer was harvested and subjected to quantitative analysis of pesticides. The average distribution ratio of the pesticides to the oil layer was 94.4 +/- 6.7% in the mixture of the oil and distilled water, and 105.5 +/- 6.6% in the mixture of the oil and ginseng extract. No significant qualitative and quantitative change of ginsenosides, the active ingredients of Panax ginseng, was observed in the ginseng extract before and after the oil treatment. These results suggest that two-phase partition chromatography between soybean oil and the aqueous phase is a cost-, labor- and efficiency-effective reliable method for the elimination of pesticide residues in ginseng extract.

Chemical Phenomena↗

PubMed2004

Methyl methacrylate in poly(methyl methacrylate)--validation of direct injection gas chromatography.

Gas chromatography (GC) was investigated for the determination of residual methyl methacrylate (MMA) in heat-processed poly(methyl methacrylate) (PMMA) denture base material emphasizing recovery and validation. Standard solutions of MMA and emulsion-polymerized PMMA in dichloromethane were analysed, before and after distillation by a room-temperature air stream into a liquid nitrogen trap, and in the presence of PMMA by direct injection. Quantitative NMR analysis using dimethyl sulphoxide as internal calibration standard in deuterated chloroform solutions provided validation. Good concordance was observed between results under all conditions; no problems arose from direct injection of PMMA solution for GC. Good straight line responses in log-log plots were generally observed. For GC and MMA: log-log calibration curve (slope: 0.9552 +/- 0.0051, r2: 0.9992, n = 32) indicated some non-linearity (t = 8.875, p approximately 4 x 10(-10)). Distillation gave slope: 0.9751 +/- 0.0213 (NS versus unity; t = 1.172, p > 0.25). For PMMA solutions, distillation (r2: 0.9301) gave greater scatter than direct injection (r2: 0.9704). For NMR: log-log plot of calculated versus actual MMA (slope: 0.9363 +/- 0.0157, r2: 0.9969, n = 13) again indicated non-linearity (t = 4.0682, p = 0.0019). PMMA solutions gave slope: 0.9477 +/- 0.0328, r2 = 0.9858 (NS versus unity; t = 1.5941, p = 0.13). Determination of MMA in PMMA by GC is recommended.

Calibration↗

PubMed2006

Liquid chromatograpic-mass spectrometric analysis of phenolics and free radical scavenging activity of rosemary extract from different raw material.

The antioxidant activity of rosemary (Rosmarinus officinalis) extract from different raw materials has been studied. Extracts were prepared from wild or drip-irrigated plants, as well as from the by-product resulting from the distillation of the aromatic essential oil. The radical scavenging activity of rosemary extracts was compared with that of antioxidants widely used in food, such as BHT and delta-tocopherol, using an optimization of the method based on the reduction of the radical 2,2-diphenyl-1-picrylhydrazyl (DPPH). The results pointed the excellent antioxidant activity of the crude fresh rosemary extracts, which was almost identical to that of pure delta-tocopherol, and higher than that of BHT; extracts prepared from distilled rosemary showed the lowest activity, although they are also of interest due to the low cost of the raw material. High performance liquid chromatography (HPLC) combined with diode array (DAD) and electrospray (ESI)-ion trap-MS detection was used to separate and identify the compounds present in the rosemary extracts. Rosmarinic acid, carnosic acid and seven of their terpene-type metabolites, and seven flavones were identified. The drying and/or distillation treatments used with the plant material strongly affected the content of the two compounds of higher antioxidant activity: rosmarinic acid and carnosic acid.

Abietanes↗

PubMed2005

Molecular interaction in alginate beads reinforced with sodium starch glycolate or magnesium aluminum silicate, and their physical characteristics.

Diclofenac calcium-alginate (DCA) beads were reinforced with different amounts of sodium starch glycolate (SSG) or magnesium aluminum silicate (MAS) and were prepared using ionotropic gelation method. Complex formation of sodium alginate (SA) and SSG or MAS in calcium-alginate beads was revealed using FTIR spectroscopy. Differential scanning calorimetric study indicated that diclofenac sodium (DS) in amorphous form was dispersed in the matrix of DCA beads. The thermal behavior of SSG-DCA and MAS-DCA beads was similar to the control bead. Both additives can improve the entrapment efficiency of DCA beads. The swelling and water uptake of the beads depended on the properties of incorporated additives. The SSG-DCA beads showed a higher water uptake and swelling than MAS-DCA beads. Moreover, the swelling of the beads showed a good correlation with the square root of time. The release kinetic of the beads in pH 6.8 phosphate buffer was swelling controlled mechanism, while that in distilled water followed Higuchi's model. The slower release rate and the longer lag time in pH 6.8 phosphate buffer was obtained from the SSG-DCA and MAS-DCA beads because of complex formation between SA and SSG or MAS. However, SSG in the beads could increase the release of DS from the beads in distilled water because it acted as a channeling agent. In contrast, MAS retarded the release of DS from the beads in distilled water due to the stronger matrix formation.

Alginates↗

PubMed2006

Well-ordered mesoporous bioactive glasses (MBG): a promising bioactive drug delivery system.

The local drug release system is considered to be an alternative to treat the bone infection. In this paper, well-ordered mesoporous bioactive glasses (MBG) with high specific surface area have been synthesized in aqueous solution by a two-step acid-catalyzed self-assembly process combined with hydrothermal treatment. Gentamicin was encapsulated into the MBG by adsorption method and in vitro release of gentamicin from MBG was performed in distilled water and modified simulated body fluid (SBF), respectively. The results showed that the amount of drug loading of MBG was three times more than that of conventional sol-gel 58S. The outcomes of drug release in distilled water and in SBF showed that M58S effectively decreased the initial burst. During the release period, gentamicin was released from the M58S at a much lower release rate as compared to that from 58S after soaking in distilled water and SBF. Furthermore, the drug release was sensitive to the pH and ionic concentration of the release medium suggesting possible controls of the release rate. In addition, in contrast to conventional sol-gel 58S, M58S had higher ability to induce hydroxyapatite (HAp) formation. Therefore, well-ordered mesoporous bioactive glasses might be used as a bioactive drug release system for preparation of bone implant materials.

Drug Delivery Systems↗

PubMed2004

Water-mediated lysis of lens epithelial cells attached to lens capsule.

PURPOSE: To investigate the effect of distilled deionized water (DDW) on lens epithelial cells (LECs) attached to the lens capsule. SETTING: Wound Healing Research Laboratory, Center for Vision Research, Westmead Hospital, Sydney, NSW, Australia. METHODS: Anterior capsulotomy specimens taken during routine cataract surgery were divided in half. One half was immersed in DDW and the other half in culture medium (control) for 1 to 5 minutes and photographed at intervals by phase-contrast microscopy. In further experiments, the capsules were exposed to DDW for 1 or 2 minutes and placed in culture for 1 week to determine whether LECs survive treatment and are capable of repopulating the lens capsule. RESULTS: Distilled-deionized water induced marked swelling of the cytoplasm within 60 seconds of treatment. At 120 seconds, there was disruption of the plasma membranes, with few intact cells remaining. In the control capsules, confluent monolayers of LECs covered the entire capsule surface with a halo of LECs growing on the surrounding plastic well. Viable LECs were observed in 1 of 3 capsules treated for 1 minute with DDW. These did not reach confluence or grow off the capsule onto the surrounding well. No viable LECs were seen on capsules exposed to DDW for 2 minutes. CONCLUSIONS: Short exposure of LECs to DDW induced extensive and rapid cell lysis. Distilled-deonized water may be a useful agent for instillation in the capsular bag during sealed-capsule irrigation to prevent posterior capsule opacification.

Cataract Extraction↗

PubMed2006

Removal of heavy metals from kaolin using an upward electrokinetic soil remedial (UESR) technology.

An upward electrokinetic soil remedial (UESR) technology was proposed to remove heavy metals from contaminated kaolin. Unlike conventional electrokinetic treatment that uses boreholes or trenches for horizontal migration of heavy metals, the UESR technology, applying vertical non-uniform electric fields, caused upward transportation of heavy metals to the top surface of the treated soil. The effects of current density, treatment duration, cell diameter, and different cathode chamber influent (distilled water or 0.01 M nitric acid) were studied. The removal efficiencies of heavy metals positively correlated to current density and treatment duration. Higher heavy metals removal efficiency was observed for the reactor cell with smaller diameter. A substantial amount of heavy metals was accumulated in the nearest to cathode 2 cm layer of kaolin when distilled water was continuously supplied to the cathode chamber. Heavy metals accumulated in this layer of kaolin can be easily excavated and disposed off. The main part of the removed heavy metals was dissolved in cathode chamber influent and moved away with cathode chamber effluent when 0.01 M nitric acid was used, instead of distilled water. Energy saving treatment by UESR technology with highest metal removal efficiencies was provided by two regimes: (1) by application of 0.01 M nitric acid as cathode chamber influent, cell diameter of 100 mm, duration of 18 days, and constant voltage of 3.5 V (19.7 k Wh/m(3) of kaolin) and (2) by application of 0.01 M nitric acid as cathode chamber influent, cell diameter of 100 cm, duration of 6 days, and constant current density of 0.191 mA/cm(2) (19.1 k Wh/m(3) of kaolin).

Algorithms↗

PubMed2006

Removal efficiency of calcium hydroxide intracanal medicament with two calcium chelators: volumetric analysis using spiral CT, an in vitro study.

The vehicles used to carry calcium hydroxide intracanal medicament are many and may affect the retrieval. Access cavities were prepared in 40 single rooted anterior teeth, cleaning and shaping was done and filled with either Metapex or pure calcium hydroxide powder in distilled water. After 7 days the calcium hydroxide was retrieved using either 17% EDTA or 10% citric acid in combination with ultrasonic agitation. Volume analysis was done using spiral computed tomography. The percentage difference was calculated and statistically analyzed using Kruskal-Wallis and Mann-Whitney U test. 10% citric acid showed better removal efficiency than 17% EDTA for Metapex (p = 0.003). The 17% EDTA showed excellent removal efficiency of powder form of calcium hydroxide in distilled water than Metapex (p < 0.001). Ten percent citric acid removed powder form of calcium hydroxide in distilled water better than Metapex (p = 0.05).

Calcium Hydroxide↗

PubMed2004

Spinacia oleracea L. protects against gamma radiations: a study on glutathione and lipid peroxidation in mouse liver.

The present study deals with the protective effect of Spinacia oleracea L. against radiation-induced oxidative stress, which is evaluated in terms of lipid peroxidation (LPO) product and tissue levels of glutathione. Swiss albino male mice aged 6-8 weeks, weighing 22+/-3 g, each were selected from an inbred colony and divided into four groups. One group served as normal and a second group (extract of S. oleracea L. (SE) treated un-irradiated) were administered methanolic (50%) SE at a dose of 1100mg/kg body wt./day dissolved in distilled water. A third group (untreated-irradiated) was administered distilled water orally, which served as control. A fourth group (SE pre-treated irradiated) was administered methanolic (50%) SE at a dose of 1100 mg/kg body wt./day dissolved in distilled water. Two groups, one untreated-irradiated and another S. oleracea pre-treated irradiated were exposed to 5 Gy of gamma radiation at a rate of 1.07 Gy/min with a source-to-surface distance of 77.5 cm. The animals were autopsied at 1, 3, 7, 15, and 30 days post-exposure. LPO increased after irradiation up to day 15 in the untreated-irradiated group and up to day 7 in SE pre-treated irradiated mice. LPO values were significantly lower in the SE pre-treated irradiated group as compared to their respective untreated-irradiated group at all intervals, which reached normal values from day 7 onward. The percentage of protection observed in the SE pre-treated irradiated group was, 22.22%, 24.8%, 33.25%, 42.84% and 26.36% at 1, 3, 7, 15, 30 days post-exposure, respectively. Radiation-induced glutathione depletion was checked after 7 days' exposure in SE pre-treated irradiated as compared to untreated-irradiated in which recovery started after day 15. Values were significantly higher in the SE pre-treated irradiated group from their respective untreated-irradiated group at all intervals. The percentage of protection observed in the SE pre-treated irradiated group was, 29.41%, 42.68%, 43.55%, 53.81%, 39.28% at 1, 3, 7, 15, 30 days post-exposure, respectively. It is found that radiation-induced augmentation in malondialdehyde contents and depletion in glutathione changes in liver can be altered by S. oleracea L. The protection may be attributed to the combined effects of its constituents rather than to any single factor as the leaves are rich in carotenoid content (beta-carotene, lutein, Zeaxanthine), ascorbic acid, flavonoids and p-coumaric acid. Thus Spinacia, showing protection in liver, may prove promising as a rich source of antioxidants because its use is cost-effective, especially for peoples in adverse and hazardous circumstances who are living in poverty.

Animals↗

PubMed2006

Effect of bleaching agents on the microhardness of tooth-colored restorative materials.

STATEMENT OF PROBLEM: There is no consensus concerning the effect of bleaching gels on microhardness of restorative materials. Information about the effect of whitening strips on microhardness of restorative materials is also limited. PURPOSE: The purpose of this study was to evaluate the effect of a bleaching gel and a whitening strip on the microhardness of 3 tooth-colored restorative materials. MATERIAL AND METHODS: Forty cylindrical specimens (6 x 2 mm) of each restorative material, including a nanohybrid composite resin (Grandio), a polyacid-modified composite resin (Dyract eXtra), and a glass-ionomer cement (Ionofil Molar AC), were prepared and stored in distilled water at 37 degrees C for 24 hours. The specimens were then polished using medium, fine, and superfine polishing disks and stored in 37 degrees C distilled water for 7 days. Specimens were divided into 4 groups (n=10). One group was selected for baseline Vickers hardness measurements (load 100 g, dwell time 20 seconds) of the top surfaces. The other 3 groups were treated for 21 days with 1 of the following: distilled water (control), bleaching gel (10% carbamide peroxide), or whitening strip (14% hydrogen peroxide). The top surfaces of the treated specimens were also subjected to the same hardness testing performed for the baseline specimens. Data were analyzed with 2-way analysis of variance and Tukey Honestly Significant Difference tests (alpha=.05). RESULTS: There were no significant differences in microhardness between the test groups of each restorative material. However, significant differences in microhardness were observed among restorative materials. For all test groups, composite resin showed the highest hardness values, whereas glass-ionomer cement presented the lowest (P<.05). CONCLUSION: The bleaching products used in this study did not adversely affect the microhardness of the restorative materials.

Acrylic Resins↗

PubMed2006

Surface detail, compressive strength, and dimensional accuracy of gypsum casts after repeated immersion in hypochlorite solution.

STATEMENT OF PROBLEM: One method used to disinfect a dental cast is immersion in a disinfecting solution. Repeated immersion of a cast in disinfectant may affect surface detail as well as other physical properties. PURPOSE: The purpose of this study was to evaluate the changes in surface detail quality, dimensional accuracy, and wet compressive strength of dental casts as a result of repeated disinfection in slurry containing 0.525% sodium hypochlorite solution. MATERIAL AND METHODS: Two different test specimen configurations were used, one for evaluating surface detail quality and dimensional accuracy and the other for compressive strength. Sixty specimens each were made of type III and type IV dental stone (Excalibur). Thirty specimens were immersed in slurry, a supernatant solution of calcium sulfate in distilled water (control casts), and 30 in slurry with sodium hypochlorite (test casts) solutions for 30 minutes and air dried for 24 hours. This process was repeated 7 times before testing. Linear dimensional change, surface detail quality, and wet compressive strength were determined according to American National Standards Institute/American Dental Association (ANSI/ADA) standards. The data were analyzed using 2-way analysis of variance and 2-sample independent t tests (alpha=.05). RESULTS: For specimens prepared with type III and type IV stone, treatment by immersion in slurry (control casts) and in slurry with sodium hypochlorite (test casts) resulted in an increase (P<.0001) in linear dimensional change. The type IV casts treated with slurry with sodium hypochlorite showed significantly less (P<.0001) mean linear dimensional change (0.025%) compared with type III stone casts (0.063%), and the values remained within the ANSI/ADA specified standards. Both test solutions caused some degree of erosion or damage to the surface quality of casts made from type III and type IV stones. However, the difference between the control and test casts was not significant. Slurry with 0.525% sodium hypochlorite solution decreased the compressive strength of both types of stones significantly (P<.001) compared with distilled water slurry. However, the values remained close to ANSI/ADA standards. CONCLUSION: The results demonstrated that repeated immersion of type III and type IV stone specimens in slurry with distilled water and slurry with 0.525% sodium hypochlorite, along with drying in air, caused a significant increase in linear dimension and a significant decrease in wet compressive strength. Although both the solutions caused some degree of damage to surface details for type III and type IV stones, the difference was not significant.

Calcium Sulfate↗

PubMed2006

Impact of water quality on setting of irreversible hydrocolloid impression materials.

STATEMENT OF PROBLEM: Setting of irreversible hydrocolloid impression materials is based on the ionic reaction between carboxylic groups and calcium ions and may, therefore, be affected by ionic species present in the mixing water. The impact of this phenomenon on the clinical performance of these materials has not been well documented. PURPOSE: The purpose of this study was to compare the setting behavior of irreversible hydrocolloid impression materials when mixed with tap and distilled water, and to determine the impact of typical cations present in tap water and their concentrations on the setting process. MATERIAL AND METHODS: Six brands of irreversible hydrocolloid impression materials (Kromopan 100, Xantalgin Select FS, Alginoplast, Elastic Plus, Ypeen, and Ypeen Premium) were mixed with tap and distilled water (control) according to manufacturers' recommendations. Elastic Plus was also mixed with aqueous solutions containing various concentrations of NaCl, CaCl(2), and AlCl(3) to determine the role of typical cations on setting. Using a controlled shear stress oscillatory rheometer, time changes of storage (G') and loss (G'') moduli during setting were measured at 23 degrees C and used to determine the working and setting times and rigidity of set impression materials. The sample size (n=3) for each material/mixing system was increased to 8 to increase reliability of measurements in systems where the effect of mixing water was low or variance of results was high. The data were analyzed (alpha=.05) using a t test (tap water), a 1-way ANOVA, a Tukey post hoc test (shear stress), and a nested ANOVA and Fisher Least Significant Difference post hoc analysis (cation and cation concentration). RESULTS: Statistical analysis showed significant (P<.001) acceleration in the setting rate for Kromopan 100, the working time of which was shorter with tap water by 23.4 seconds and the setting time, by 32.8 seconds. Similar significant reductions (in seconds) in both working and setting times, respectively, were found with Xantalgin Select FS (12.0, P<.001 and 23.6, P<.002), Alginoplast (24.3, P<.001 and 44.7, P<.005), and Elastic Plus (23.0, P<.001 and 22.0, P<.002), when compared with the same materials mixed with distilled water. At the same time, the rigidity of the set impression materials mixed with tap water increased by approximately 10%. With Ypeen Premium, the setting time decreased significantly by 20.0 seconds (P<.001) with tap water, while the working time and rigidity did not change. The setting behavior of Ypeen was not significantly affected by water quality. Acceleration of the setting reactions and increase in impression rigidity depended (P<.001) primarily on concentration and valency of cations present in mixing water. CONCLUSION: Setting of irreversible hydrocolloid impression materials can be significantly accelerated when tap water with high water hardness is used for mixing or when the mixing water contains higher concentrations of cations such as Na(+), Ca(2+), and Al(3+).

Aluminum↗

PubMedDate not supplied

Neurotoxicity of intrathecally administered bupivacaine involves the posterior roots/posterior white matter and is milder than lidocaine in rats.

BACKGROUND AND OBJECTIVES: Clinical and laboratory studies suggest that lidocaine is more neurotoxic than bupivacaine. However, histological evidence of their comparative neurotoxicity is sparse. We thus pathologically and functionally compared the intrathecal neurotoxicity of these agents. METHODS: Rats received 0.12 microL/g body weight lidocaine (0%, 2%, 10%, or 20%) or bupivacaine (0%, 0.5%, 2.5%, or 5%) in distilled water via an intrathecal catheter. The influence of high osmolarity was also examined using 5% bupivacaine in 20% glucose solution (5% BG) and a control 25% glucose solution. The L3 spinal cord, the posterior and anterior roots, and the cauda equina were examined by light and electron microscopy. Walking behavior and sensory threshold were investigated as neurofunctional tests. RESULTS: The posterior root and posterior white matter showed axonal degeneration in rats treated with 10% and 20% lidocaine and 5% bupivacaine in distilled water (5% BDW) and in 5% BG, but not in rats treated with 2% lidocaine, 0.5% and 2.5% bupivacaine, distilled water, or 25% glucose solution. The histological damages were more severe in 20% lidocaine-treated rats than in 5% bupivacaine-treated rats. The damage of posterior white matter was observed only when the posterior root was severely injured. No significant difference of histological findings was observed between 5% BDW and 5% BG. Functional abnormalities were found only in rats treated with 20% lidocaine. CONCLUSIONS: The neurotoxic lesions caused by bupivacaine and lidocaine were indistinguishable in the primary site and the extending pattern, such as axonal degeneration originating from the posterior roots and extending to the posterior white matter. The intrathecal neurotoxicity is greater in lidocaine than in bupivacaine.

Anesthesia Recovery Period↗

PubMed1980

The AAS determination of copper and zinc levels in the serum of hemodialysis patients.

An electrothermal atomic absorption technique for the determination of subnanogram amounts of copper and zinc in aqueous and blood serum matrices has been evaluated. The technique has been utilized to study the effect of dialysis (artificial kidney) on the levels of these trace elements in the serum of hemodialysis patients. The present results confirm a previous study (1) which was conducted on representative samples that were taken from the continuous flow of the dialysis fluid (dialysate). Matrix effects have been minimized by using serum controls (obtained from a pool made of the tested serum samples), small sample size, and background correction. Before dialysis, values of copper for patients who were dialysed against tap water (tap-water patients) and distilled water (distilled-water patients) were: (mean +/- SD) 1297 +/- 59 and 1064 +/- 137 micrograms/L, respectively; after dialysis: 1539 +/- 98 and 1120 +/- 129 micrograms/L, respectively. Zinc levels were less affected by the dialysis process; before dialysis: tap-water patients, 952 +/- 131 micrograms/L; distilled-water patients, 932 +/- 119 micrograms/L; after dialysis: 1001 +/- 137 micrograms/L, and 934 +/- 121 micrograms/L, respectively. Because the method is sensitive, accurate, and precise, it can be utilized to study trace levels of copper and zinc in serum when limitations of sample volume exist as in the present case or with pediatric patients.

Copper↗

PubMed2000

Sample preparation for the analysis of flavors and off-flavors in foods.

Off-flavors in foods may originate from environmental pollutants, the growth of microorganisms, oxidation of lipids, or endogenous enzymatic decomposition in the foods. The chromatographic analysis of flavors and off-flavors in foods usually requires that the samples first be processed to remove as many interfering compounds as possible. For analysis of foods by gas chromatography (GC), sample preparation may include mincing, homogenation, centrifugation, distillation, simple solvent extraction, supercritical fluid extraction, pressurized-fluid extraction, microwave-assisted extraction, Soxhlet extraction, or methylation. For high-performance liquid chromatography of amines in fish, cheese, sausage and olive oil or aldehydes in fruit juice, sample preparation may include solvent extraction and derivatization. Headspace GC analysis of orange juice, fish, dehydrated potatoes, and milk requires almost no sample preparation. Purge-and-trap GC analysis of dairy products, seafoods, and garlic may require heating, microwave-mediated distillation, purging the sample with inert gases and trapping the analytes with Tenax or C18, thermal desorption, cryofocusing, or elution with ethyl acetate. Solid-phase microextraction GC analysis of spices, milk and fish can involve microwave-mediated distillation, and usually requires adsorption on poly(dimethyl)siloxane or electrodeposition on fibers followed by thermal desorption. For short-path thermal desorption GC analysis of spices, herbs, coffee, peanuts, candy, mushrooms, beverages, olive oil, honey, and milk, samples are placed in a glass-lined stainless steel thermal desorption tube, which is purged with helium and then heated gradually to desorb the volatiles for analysis. Few of the methods that are available for analysis of food flavors and off-flavors can be described simultaneously as cheap, easy and good.

Flavoring Agents↗

PubMed1999

Determination of sorbic acid in urine by gas chromatography-mass spectrometry.

The average daily uptake of the common food preservative sorbic acid is estimated to range from 0.01 to 1.1 mg kg-1. Sorbic acid mainly is metabolised to carbon dioxide. Minor amounts are converted to trans,trans-muconic acid (ttMA) as well as excreted unchanged into the urine. Since urinary ttMA is a biomarker for the occupational and environmental exposure to benzene, there is an additional need for monitoring the uptake of sorbic acid, particularly at low, environmental benzene exposure levels. For this purpose, a simple, robust and rapid method for the determination of sorbic acid in urine at trace levels was developed. After addition of 10 ml of water and 5 ml of 8 M hydrochloric acid to 10 ml of the thawed urine, the sample was water steam distilled using an automated distillation device. A total of 100 ml of the distillate were solid-phase extracted. After washing, the sorbic acid was eluted with 4 ml methanol. The eluate was reduced under a stream of nitrogen to a volume of 300 microliters. After addition of 500 microliters boron trifluoride in methanol and incubation for 1 h at 60 degrees C, the resulting sorbic acid methyl ester was extracted three times with 1 ml heptane. To the combined heptane layers, sorbic acid ethyl ester was added as an internal standard. After reducing to a volume of 100 microliters in a stream of nitrogen, the final analysis was performed by GC-MS using the fragment ions m/z 126 for the analyte and m/z 140 for the internal standard. The limit of detection was 0.7 ng ml-1 urine and the R.S.D. of 69 duplicate determinations was 7.5%. In a controlled, experimental study and in a field study, we were able to show that urinary sorbic acid is a marker for the dietary uptake of sorbic acid and that sorbic acid is converted to ttMA. On average, 0.1% of the dietary sorbic acid is excreted unchanged into the urine. Excretion is complete within 24 h. We found that, on average, 0.23% of the oral dose of sorbic acid is excreted as urinary ttMA. There was a significant correlation between urinary excretions of sorbic acid and ttMA (r = 0.74, n = 69). We conclude that urinary sorbic acid can be used to correct the urinary ttMA level in order to determine the portion related to benzene exposure. This appears to be necessary particularly at low, environmental benzene levels.

Adolescent↗

PubMed1997

Fractionation and bioassay of human odor types.

Human urine samples were fractionated to examine the contribution of volatiles to the individual body odor. The samples were obtained from 4 male donors and fractionated using a vacuum technique. The volatiles from the chemical fractions were analyzed using the CLSA technique and gas chromatography. Thereafter, these fractions were tested in a computer-controlled olfactometer by trained rats. Although the rats were able to discriminate the distillation residue, they could not recognize the urine odor in the distilled fraction. The results of gas chromatography indicate a continuous release of volatile constituents in the distillation residue.

Adult↗

PubMed2001

Aqueous leaching properties and environmental implications of cadmium, lead and zinc trimercaptotriazine (TMT) compounds.

2,4,6-Trimercaptotriazine, trisodium salt nonahydrate (TMT-55) is a commercial product that is widely used to chemically precipitate cadmium, lead, zinc and other heavy metals from wastewaters and contaminated natural waters. When mixed with aqueous solutions of TMT-55, aqueous solutions of either reagent-grade zinc, cadmium, or lead salts precipitate crystalline "Zn-TMT", amorphous or crystalline "Cd-TMT" or amorphous "Pb-TMT" (M3[S3C3N3]2.nH2O, where M=Cd2+, Pb2+, and Zn2+ and n> or = 0) that may eventually crystallize if stored in air. Laboratory aqueous leaching studies over 78-106 days using pH 3 HCl, distilled water (pH 6) and pH 9-10 NaOH evaluated the stability of the Cd-, Pb-, and Zn-TMT precipitates. Under pH 3 conditions, the amorphous Cd- and Pb-TMT compounds converted to their crystalline forms and amorphous Cd-TMT also crystallized in distilled water. Otherwise, no decomposition products were detected in the leached solid residues. When compared with the aqueous solubilities of corresponding sulfides and most hydroxides, the TMT compounds were significantly more soluble in distilled water and pH 3 HCl.

Cadmium↗