Setting up of recovery profiles: A tool to perform the compliance with recovery requirements for residue analysis

The use of the recovery term has presented some confusion in Analytical Chemistry. Recent IUPAC recommendations propose to distinguish between two terms: recovery or recovery factor, ℜ, and apparent recovery, ℜ*. Apparent recovery includes recovery factor and a new recovery term proposed in this paper, named calibration recovery, ℜ^C, which depends of the type of systematic error due to the matrix effect (constant and/or proportional) and is related to the applied calibration methodology. This paper highlights the dependence of the calibration recovery on the sample analyte concentration and, for extension, of the apparent recovery, defines the recovery profile, and makes evident the need to determine a “fit for purpose” analyte concentration interval to comply with a regulated recovery requirements. An approach to estimate the calibration recovery and its associated uncertainty in relation to the above-mentioned dependence is presented. The usefulness of the proposed methodology has been shown in the quantification of a pesticide by GC-ECD for assessing dermal exposure.     

Instantaneous strain recovery elasticity and endothermic heat change in nylon-6 monofilaments and silicone rubbers

The instantaneous elastic moduli for a nylon-6 monofilament were derived on strain recoveries right after creep, stress relaxation, and rapid elongation,E _c ,E _s andE _e , respectively. It was found that during strain recoveryE _s (>E _e ) andE _e increase monotonically with increasing load,m ₁, on the sample. The extrapolated value of E_s atm ₁=0 g is almost equal to Young's modulus, 4.06 GPa. The value ofE _c also increased with increasingm ₁, and atm ₁=600 g (1.93 t cm^–2) reached about 14 GPa. The endothermic heat change right after creep, stress relaxation or rapid elongation,Q, was negligibly small. For comparison,E _s ,E _c andQ were also investigated for silicone rubber. It was found thatE _s (53.8 M Pa at the draw ratioD=1.2) decreased abruptly atD=1.3. In the range ofD=1.4–1.9,E _s was only 22.6 MPa. In the case of stress relaxation,Q increased with increasingD from 4 J mol^–1 (atD=1.2) to 56 J mol^–1 (atD=1.9). FurthermoreE _c (5.58 MPa atm ₁=133.8 g (429.4 kg cm^–2)) increased gradually with increasing m₁ and attained 16.6 MPa atm ₁=548.4 g (1.76 t cm^–2). In the case of creep,Q was in the range of 0–11.5 J mol^–1 and larger when larger loads,m ₂ were removed during the later stages of creep.Dedicated to Professor Bernhard Wunderlich on the occasion of his 65th birthdayThe author wishes to thank Mr. Keizi Igarashi and Mr. Tetsuya Yasui for helping in the experiments.     

Recovery of pyridine from aqueous solution by membrane pervaporation

Three different membranes, based on poly(dimethylsiloxane) (PDMS), cation-exchange material and poly(vinyl alcohol) (PVA) respectively, were tudied for the separation of pyridine-water mixtures by pervaporation. The PDMS membrane was preferentially permeable to pyridine and the other two were selective towards water. Three membranes showed different permeation performance, allowing the application of the technique to the separation of feeds of different composition. The temperature profile of the permeability suggests that it is possible to carry out the operation at an elevated temperature in order to achieve high productivity. A combination of the three types of membranes was designed for the production of anhydrous pyridine from dilute pyridine aqueous solution by pervaporation.     

<Emphasis Type="Italic">L</Emphasis>-Carnitine Supplementation: A New Paradigm for its Role in Exercise

Summary. Early research investigating the effects of L-carnitine supplementation has examined its role in substrate metabolism and in acute exercise performance. These studies have yielded equivocal findings, partially due to difficulties in increasing muscle carnitine concentrations. However, recent studies have proposed that L-carnitine may play a different role in exercise physiology, and preliminary results have been encouraging. Current investigations have theorized that L-carnitine supplementation facilitates exercise recovery. Proposed mechanism is as follows: 1) increased serum carnitine concentration enhances capillary endothelial function; 2) increased blood flow and reduced hypoxia mitigate the cascade of ensuing, destructive chemical events following exercise; 3) thus allowing reduced structural damage of skeletal muscle mediated by more intact receptors in muscle needed for improved protein signaling. This paradigm explains decreased markers of purine catabolism, free radical formation, and muscle tissue disruption after resistance exercise and the increased repair of muscle proteins following long-term L-carnitine supplementation.     

Integrated production of ethanol fuel and protein from Coastal Bermudagrass

The herbaceous crops that may provide fermentable carbohydrates for production of fuels and chemicals also contain 10–20% protein. Protein coproduction with biomass-derived fuels and chemicals has important advantages: (1) food and fuel production can be integrated, and (2) protein is a high-value product that may significantly improve overall process economics. We report the results of an integrated approach to producing protein and fermentable sugars from one herbaceous species, Coastal Bermudagrass (CBG). The ammonia fiber explosion (AFEX) process makes possible over 90% conversion of cellulose and hemicellulose to simple sugars (about 650 mg reducing sugars/g dry CBG) at 5 IU cellulase/g vs < 20% conversion for untreated CBG. The AFEX treatment also improves protein extraction from CBG; over 80% protein recovery is possible from AFEX-treated CBG vs about 30% recovery from untreated CBG.     

Shape analysis based critical Eotvos numbers for buoyancy induced partial detachment of oil drops from hydrophilic surfaces

Removal of oil drops from solid surfaces immersed in an aqueous medium is of interest in many applications. It has been shown that drop shape analysis can be used to predict conditions at which the stability limit of a lighter than water oil drop on a solid surface immersed in an aqueous bath is reached (Adv. Colloid Interface Sci. 98 (2002) 265). However the above analysis is restricted to cases where the contact angle made by the drop is below 90degrees and when the surface conditions result in a 'pinned' contact line. In this paper, it is shown that drop shape analysis can be used to predict the critical conditions at which drop stability limit is reached for drop contact angles of 90degrees and above, which is encountered with 'hydrophilic' surfaces. This critical condition can predict the occurrence of partial oil drop detachment, before complete removal due to 'roll-up', which occurs when the hydrophilic surface is adequately smooth which prevents 'pinning' of the contact line. The critical conditions at which partial drop detachment occurs can also be approximately predicted from simple force balances. It has been shown (Adv. Colloid Interface Sci. 98 (2002) 265) that for contact angles less than 90degrees, the critical limit based on shape analysis appears to resolve the differences that arise due to alternate expressions for capillary retention force. This paper shows that even for contact angles above 90degrees, the critical conditions predicted from the shape analysis resolves the differences in the predictions from the alternate force balances. Drop shape analysis used in this paper is based on the 'Arc-length' form of Young-Laplace or 'drop shape' equation, which is different from the 'Y vs X' form of the above equation that is used in Adv. Colloid Interface Sci. 98 (2002) 265. The above drop shape equation is solved by a fourth order Runge-Kutta technique and it is shown that for angles less than 90degrees, the two forms of the drop shape equation, predict almost identical values of the critical Eotvos number. This paper highlights the competing effects of interfacial tension lowering induced drop instability and 'roll-up', a term that is used to describe the retraction of the contact line of an oil drop on a surface, in being the primary c ause for drop detachment.     

SHAPE MEMORY EFFECT OF PU IONOMERS WITH IONIC GROUPS ON HARD-SEGMENTS

SMPU （shape memory polyurethane） non-ionomers and ionomers, synthesized with poly（c-caprolactone） （PCL）, 4, 4＇-diphenylmethane diisocyanate （MDI）, 1,4-butanediol （BDO）, dimethylolpropionic acid （DMPA） were measured with cyclic tensile test and strain recovery test. The relations between the structure and shape memory effect of these two series were studied with respect to the ionic group content and the effect of neutralization. The resulting data indicate that, with the introduction of asymmetrical extender, the stress at 100% elongation is decreased for PU non-ionomer and ionomer series, especially lowered sharply for non-ionomer series; the fixation ratio of ionomer series is not affected obviously by the ionic group content; the total recovery ratio of ionomer series is decreased greatly. After sufficient relaxation time for samples stretched beforehand, the switching temperature is raised slightly, whereas the recovery ratio measured with strain recovery test method is lowered with increased DMPA content. The characterization with FT-IR, DSC, DMA elucidated that, the ordered hard domain of the two series is disrupted with the introduction of DMPA which causes more hard segments to dissolve in soft phase; ionic groups on hard segment enhance the cohesion between hard segments especially at high ionic group content and significantly facilitate the phase separation compared with the corresponding non-ionomer at moderate ionic group content.     

A nanoscale vesicular polydiacetylene sensor for organic amines by fluorescence recovery

We report a nanoscale lipid membrane-based sensor of conjugated polydiacetylene (PDA) vesicles for fluorescence detection of organic amines. The vesicle sensor was constructed by incorporation of a BODIPY fluorescent dye into the PDA vesicles. The fluorescent properties of the resulting vesicles can be manipulated by adjusting lipid components, and are controlled by environmental and solution conditions. The fluorescence of the BODIPY dye was significantly quenched in the polymerization of diacetylene lipid vesicles by a UV irradiation process. However, it was sufficiently recovered by external stimuli such as a hike of solution pH. The fluorescence recovery process was reversible, and a decrease in solution pH resulted in repeated quenching. The reported system transforms an external stimulus into a large fluorescence intensity change, demonstrating great potential in developing new signal reporting method for biosensor design. The quench-recovery phenomenon of the BODIPY-PDA is believed to be related to the energy transfer between the dye and the PDA conjugate backbone. The vesicle sensor was applied for detecting an organic amine, triethylamine (TEA) and a large linear relationship was obtained between the increase in fluorescence intensity and the concentrations of TEA. The detection limit of TEA by vesicle sensors using fluorescence recovery was found to be 10 μM.     

A comparative study of solvent extraction of total petroleum hydrocarbons in soil

Three non-specific methods for the extraction of total petroleum hydrocarbons (TPH) from soil into organic solvent were compared. The techniques used for sample preparation were Soxhlet extraction, closed-vessel microwave-assisted extraction, and CEN shake extraction. The total concentrations of extracted compounds in the boiling point range of C10–C40 were determined by gas chromatography with flame ionization detection. The best recovery (99%) and repeatability (±3%) from standard oil mixtures were obtained with microwave-assisted extraction. However, the different extraction methods exhibited different behaviour when spiked soil samples were extracted. The best repeatability was obtained with CEN shake extraction (±6%) but the repeatability values for Soxhlet and microwave-assisted methods were quite high (>20%). However, the larger uncertainties of the latter extraction methods does not necessarily limit the applicability of these methods to the determination of petroleum hydrocarbons in soil, as in the assessment of soil contamination the expanded uncertainty of the result is usually not limited by analytical uncertainty, but rather by the uncertainty of the primary sampling stage. However, distinctive variation found in the chromatographic profiles illustrates that discretion should be obeyed when chromatograms obtained after application of different extraction methods on petroleum contaminated samples are to be used in the fingerprinting or age dating studies. Otherwise, misleading conclusions concerning the age of spillage could be drawn.     

The circular chemistry conceptual framework: A way forward to sustainability in industry 4.0

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