A simple analytical platform based on thin-layer chromatography coupled with paper-based analytical device for determination of total capsaicinoids in chilli samples.

A new analytical platform based on the use of thin-layer chromatography (TLC) coupled with paper-based analytical device (PAD) was developed for the determination of total capsaicinoids in chilli samples. This newly developed TLC-PAD is simple and low-cost without any requirement of special instrument or skillful person. The analysis consisted of two steps, i.e., extraction of capsaicinoids from chilli samples by using ethanol as solvent and separation of capsaicinoids by thin-layer chromatography (TLC) and elution of capsaicinoids from the TLC plate with in situ colorimetric detection of capsaicinoids on the PAD. For colorimetric detection, Folin-Ciocalteu reagent was used to detect phenolic functional group of capsaicinoids yielding the blue color. The blue color on the PAD was imaged by a scanner followed by evaluation of its grayscale intensity value by ImageJ program. This newly developed TLC-PAD method provided a linear range from 50 to 1000mgL-1 capsaicinoids with the limit of detection as low as 50mgL-1 capsaicinoids. The proposed method was applied to determine capsaicinoids in dried chilli and seasoning powder samples and the results were in good agreement with those obtained by HPLC method.

Paper-based analytical device for sampling, on-site preconcentration and detection of ppb lead in water.

A simple and cost effectiveness procedure based on a paper based analytical device (PAD) for sampling, on-site preconcentration and determination of Pb(II) in water samples was developed. The inkjet printing method was used for patterning of PAD. Colorimetric assay was developed on a PAD for Pb(II) detection in µgL(-1) level. This µgL(-1) level detection limit was achieved by in situ- and on-site preconcentration of Pb(II) onto adsorption filter paper disc with a home-made holder before color development. Water sample was loaded onto a circular filter paper coated with zirconium silicate in 3% sodium carboxymethylcellulose for Pb(II) preconcentration. Subsequently, sodium rhodizonate in tartrate buffer solution (pH 2.8) was used as colorimetric reagent for direct Pb(II) detection on a PAD. Detection was achieved by measuring the pink color and recorded by scanner or digital camera. ImageJ software was used for measuring grey scale values. The calibration curve was linear in the range of 10µgL(-1) and 100µgL(-1), with a detection limit of 10µgL(-1). The developed method was successfully applied to the determination of Pb(II) in drinking water, tap water and surface water near electronic waste storage and the results were compared with those by graphite furnace atomic absorption spectroscopy (GF-AAS) with good agreement.

Separation of silver nanoparticles by hollow fiber flow field-flow fractionation: Addition of tannic acid into carrier liquid as a modifier.

A homemade hollow fiber flow-field fractionation (Hf-FlFFF) coupled with inductively coupled plasma mass spectrometry (ICP-MS) was set-up for silver nanoparticles (AgNPs) separation by using polysulfone hollow fiber membrane (30,000 MW cutoff) as a separation channel. Tannic acid and citrate stabilized AgNPs were synthesized and introduced into Hf-FlFFF. The effects of carrier liquid and stabilizing agent on retention behavior of AgNPs were investigated. Different elution behaviors were observed as follows: with 0.02% (w/v) FL-70, all of AgNPs were eluted from Hf-FlFFF but differences in retention behaviors were observed for AgNPs with tannic acid and citrate stabilizing agents; and with 30mM TRIS buffer, only tannic acid stabilized AgNPs were eluted from Hf-FlFFF, whereas citrate stabilized AgNPs were not eluted. In this work, tannic acid addition into carrier liquid was proposed to modify the surface of AgNPs and the surface of the membrane, and thereby adjusting the retention behaviors of AgNPs. Various concentrations of tannic acid were added into FL-70 and TRIS buffer. With the use of 0.1mM tannic acid in 30mM TRIS buffer as the carrier liquid, retention behaviors of both tannic acid stabilized- and citrate stabilized-AgNPs were similar and with similar fractionation recovery.

Discrimination of geographical origin of rice based on multi-element fingerprinting by high resolution inductively coupled plasma mass spectrometry.

Rice is a staple food for nearly half the world's population. The discrimination of geographical origin of rice in order to its authenticity is essential to prevent mislabeling and adulteration problems. The multi-element fingerprinting has a great potential for the differentiation of rice grains. A study of the capability of the high resolution inductively coupled plasma mass spectrometry (HR-ICP-MS) methodology for multi-element fingerprinting of rice has been carried out. A total of 31 Thai jasmine rice and 5 foreign (France, India, Italy, Japan and Pakistan) rice samples were analysed by high resolution ICP-MS after acid digestion. Accuracy of the whole procedure was verified by the analysis of rice flour standard reference material (NIST SRM 1568a). The concentrations of 21 elements were evaluated and used as chemical indicator to discriminate the origin of rice samples. The classification of rice samples was carried out based on elemental composition by a radar plot and multivariate data analysis, including principal component analysis (PCA) and discriminant analysis (DA). Thai jasmine rice can be differentiated from foreign rice samples by radar plots and multivariate data analysis. Furthermore, the DA can differentiate Thai jasmine rice samples according to each region of origin (northern, northeastern or central regions of Thailand). Therefore, multi-element fingerprinting combined with the use of multivariate statistical techniques can be considered as a powerful tool for rice authentication.

Application of TLC and LA ICP SF MS for speciation of S, Ni and V in petroleum samples.

A coupling of thin layer chromatography with laser ablation ICP SF MS was developed for the fractionation of Ni, V, Fe and S in crude oil and its fractions (saturate, aromatic, resin and asphaltene). The detection limits were 18 ng g(-1) and 23 ng g(-1) for nickel and vanadium, respectively, and a sample could be characterized in terms of the metal distribution as a function of species polarity within 10 min. The method was used to characterize the metal distribution in crude oils of different origins and their different fractions.

Mechanisms of red blood cells agglutination in antibody-treated paper.

Recent reports on using bio-active paper and bio-active thread to determine human blood type have shown a tremendous potential of using these low-cost materials to build bio-sensors for blood diagnosis. In this work we focus on understanding the mechanisms of red blood cell agglutination in the antibody-loaded paper. We semi-quantitatively evaluate the percentage of antibody molecules that are adsorbed on cellulose fibres and can potentially immobilize red blood cells on the fibre surface, and the percentage of the molecules that can desorb from the cellulose fibre surface into the blood sample and cause haemagglutination reaction in the bulk of a blood sample. Our results show that 34 to 42% of antibody molecules in the papers treated with commercial blood grouping antibodies can desorb from the fibre surface. When specific antibody molecules are released into the blood sample via desorption, haemagglutination reaction occurs in the blood sample. The reaction bridges the red cells in the blood sample bulk to the layer of red cells immobilized on the fibre surface by the adsorbed antibody molecules. The desorbed antibody also causes agglutinated lumps of red blood cells to form. These lumps cannot pass through the pores of the filter paper. The immobilization and filtration of agglutinated red cells give reproducible identification of positive haemagglutination reaction. Results from this study provide information for designing new bio-active paper-based devices for human blood typing with improved sensitivity and specificity.

Flow field-flow fractionation with off-line electrothermal atomic absorption spectrometry for size characterization of silver nanoparticles.

Flow field-flow fractionation (Fl-FFF) with off-line electrothermal atomic absorption spectrometry (ETAAS) detection was developed and employed for particle size characterization of Ag NPs stabilized by citrate, pectin, and alginate. Citrate stabilized-Ag NPs were prepared from sodium borohydride reduction of silver nitrate. Sodium citrate was used as the capping agent to stabilize Ag NPs and prevent the aggregation process. Pectin stabilized- and alginate stabilized-Ag NPs were prepared from ascorbic acid reduction of silver nitrate. Pectin and alginate were used as the capping agent for pectin stabilized- and alginate stabilized-Ag NPs, respectively. Three types of Ag NPs were characterized by using FlFFF, zeta potentiometer, and TEM technique. The mean particle sizes of Ag NPs as characterized by FlFFF were 9 nm, 19 nm, and 45 nm for citrate stabilized-, pectin stabilized-, and alginate stabilized-Ag NPs, respectively, in deionized water. Further, FlFFF with ETAAS detection was employed to observe the aggregation of Ag NPs of various types in environmental water in the absence and presence of humic acid. Citrate stabilized-Ag NPs underwent aggregation more rapid than the pectin stabilized- and alginate stabilized-Ag NPs as the latter two types were sterically stabilized. Further, humic acid could prolong the stability of Ag NPs in the environment.

Particle size characterization of titanium dioxide in sunscreen products using sedimentation field-flow fractionation-inductively coupled plasma-mass spectrometry.

Sedimentation field-flow fractionation-inductively coupled plasma-mass spectrometry (SdFFF-ICP-MS) was successfully applied to investigate particle size distribution of titanium dioxide (TiO(2)) in sunscreen samples after hexane extraction to remove organic components from the samples. Three brands of sunscreen products of various sun protection factor (SPF) value were used as samples. Different particle size distribution profiles were observed for sunscreen samples of various brands and SPF values; however, the particle size distributions of titanium dioxide in most sunscreen samples investigated in this work were larger than 100 nm. The titanium dioxide concentrations were higher for the products of higher SPF values. By comparing the results obtained from online SdFFF-ICP-MS and those from the off-line ICP-MS determination of titanium after acid digestion, ICP-MS was found to effectively atomize and ionize the titanium dioxide particle without the need for acid digestion of the samples. Therefore, the online coupling between SdFFF and ICP-MS could be effectively used to provide quantitative information of titanium dioxide concentrations across particle size distribution profiles.

Flow field-flow fractionation: a versatile approach for size characterization of alpha-tocopherol-induced enlargement of gold nanoparticles.

Flow field-flow fractionation (FlFFF) was used for size characterization of gold nanoparticles. The measured particle sizes obtained from FlFFF for the commercial 10 nm gold nanoparticle standard and the gold nanoparticles synthesized in the laboratory were in good agreement with those measured by transmission electron microscopy (TEM). Further, the capability of alpha-tocopherol to induce enlargement of gold nanoparticles by catalysis of the reduction of AuCl(4)(-) by citrate was observed by monitoring the changes in particle size of gold nanoparticles using FlFFF. The effects of alpha-tocopherol and incubation time on enlargement of the gold nanoparticles were examined. Higher concentrations of alpha-tocopherol resulted in larger nanoparticles. At fixed alpha-tocopherol concentration, larger nanoparticles were formed at longer incubation times.

Characterization of binding and bioaccessibility of Cr in Cr-enriched yeast by sequential extraction followed by two-dimensional liquid chromatography with mass spectrometric detection.

Sequential extraction (water, Driselase, protease XIV) and extraction with simulated gastric and intestinal fluids were proposed to characterize the binding and the bioaccessibility of chromium in two commercial food supplements obtained by incorporation of this element into yeast. Chromium in Cr-enriched yeast was found to be hardly extractable with water, Driselase, or simulated gastric fluid (recoveries of approximately 10-20%), but proteolysis or gastrointestinal fluid digestion released more than half of the chromium present. Fractionation with size-exclusion chromatography with Cr-specific detection by inductively coupled plasma mass spectrometry (ICP MS) allowed the distinction of two fractions: one below approximately 1 kDa and one 1-5 kDa; they contained the entirety of the released Cr with proportions varying as a function of the extracting solution and the origin of sample. When collected and investigated by reversed-phase high-performance liquid chromatography-ICP MS, the low molecular mass fraction was found to release Cr(III), whereas the heavier one showed most of Cr bound in fairly stable hydrophobic complexes. However, an attempt of their identification by electrospray ionization MS/MS and matrix-assisted laser desorption ionization MS was not successful.

Toward better understanding of salt-induced hen egg white protein aggregation using field-flow fractionation.

Field-flow fractionation techniques including sedimentation field-flow fractionation (SdFFF) and flow field-flow fractionation (FlFFF) were applied to investigate hen egg white protein aggregation. The thermally induced aggregation of hen egg white protein was observed at temperatures of 60 degrees C and higher. Particle size and size distribution of hen egg white protein aggregates were characterized by SdFFF to investigate parameters affecting ZnCl 2-induced aggregation of hen egg white protein. At a fixed concentration of 1.0 M ZnCl 2 and an incubation time of 15 min, the mean particle diameters of the aggregates were determined to be 0.43, 0.67, and 0.80 mum for hen egg white protein contents of 5, 6.25, and 7.5% (w/v), respectively. With the incubation time of 15 min, increasing the concentration of ZnCl 2 from 0.5 to 1.0 and to 1.5 M caused the mean particle diameter of the aggregates to grow from 0.37 to 0.42 and to 0.68 mum, respectively at 5% (w/v) hen egg white protein. Upon prolonged contact time, larger aggregates were formed. Furthermore, FlFFF was employed as a novel approach to determine the efficiency of protein utilization for aggregation. The pH values as well as ZnCl 2 and protein concentrations influenced the efficiency of protein utilization for aggregation. With the optimum condition, that is, a protein concentration higher than 2% (w/v) and a pH greater than 5, the efficiency of protein utilization was approximately 65%.

Flow field-flow fractionation-inductively coupled optical emission spectrometric investigation of the size-based distribution of iron complexed to phytic and tannic acids in a food suspension: implications for iron availability.

Flow field-flow fractionation-inductively coupled plasma optical emission spectrometry (FlFFF-ICP-OES) was applied to achieve the size-based fractionation of iron in a food suspension in order to gain insights into iron availability. The binding of iron with phytic and tannic acids, employed as model inhibitors of iron availability in foods, was investigated at pH 2.0 (representing stomach fluid), pH 5.0 (the transition stage in the upper part of the duodenum), and pH 7.0 (the small intestine). In the presence of phytic acid, iron was found as a free ion or it was associated with molecules smaller than 1 kDa at pH 2.0. Iron associated with molecules larger than 1 kDa when the pH of the mixture was raised to 5.0 and 7.0. In the presence of tannic acid, iron was again mostly associated with molecules smaller than 1 kDa at pH 2.0. However, at pH 5.0, iron and tannic acid associated in large molecules (approximately 25 kDa), while at pH 7.0, most of the iron was associated with macromolecules larger than 500 kDa. Iron size-based distributions of kale extract and tea infusion containing phytic and tannic acids, respectively, were also examined at the three pH values, with and without enzymatic digestion. Without enzymatic digestion of the kale extract and the tea infusion at pH 2.0, most of the iron was released as free ions or associated with molecules smaller than 1 kDa. At other pH values, most of the iron in the kale extract and the tea infusion was found to bind with ~2 kDa and >500 kDa macromolecules, respectively. Upon enzymatic gastrointestinal digestion, the iron was not observed to bind to macromolecules >1 kDa but <500 kDa, due to the enzymatic breakdown of large molecules to smaller ones (<1 kDa).

Reuse of waste silica as adsorbent for metal removal by iron oxide modification.

Silica gel is widely used in research laboratories, especially for the purification of organic compounds. Consequently, waste silica gel is generated in increasing amounts. In this work, waste silica was modified by coating its surface with iron oxide aiming to obtain an effective adsorbent for metal removal from wastewater. In the preparation of the adsorbent, the optimal pretreatment temperature and iron concentration were investigated. The coated waste silica was characterized for BET surface area, pore size, specific pore volume and iron content. Iron oxide-coated waste silica was tested for the adsorption of Pb(II), Cu(II), Cd(II) and Ni(II) from solutions in a batch system. The effect of contact time, pH and salt concentration on metal adsorption was investigated. It was found that the adsorption of metals occurred rapidly and reached equilibrium within 30 min. The pH suitable for metal adsorption was between 6 and 7 and leaching of iron from the coating was observed only at pH 3 or lower. The presence of salt reduced the adsorption efficiency of the adsorbent. The adsorption behavior followed both Langmuir and Freundlich isotherms (25 degrees C). Finally, the efficacy of the adsorbents was investigated using aqueous lab waste where removal efficiencies ranging from 62 to 89% were achieved when the initial metal concentrations ranged from 13 to 42 mg L(-1).

A multisyringe flow-through sequential extraction system for on-line monitoring of orthophosphate in soils and sediments.

A fully automated flow-through microcolumn fractionation system with on-line post-extraction derivatization is proposed for monitoring of orthophosphate in solid samples of environmental relevance. The system integrates dynamic sequential extraction using 1.0moll(-1) NH(4)Cl, 0.1moll(-1) NaOH and 0.5moll(-1) HCl as extractants according to the Hieltjes-Lijklema (HL) scheme for fractionation of phosphorus associated with different geological phases, and on-line processing of the extracts via the Molybdenum Blue (MB) reaction by exploiting multisyringe flow injection as the interface between the solid containing microcolumn and the flow-through detector. The proposed flow assembly, capitalizing on the features of the multicommutation concept, implies several advantages as compared to fractionation analysis in the batch mode in terms of saving of extractants and MB reagents, shortening of the operational times from days to hours, highly temporal resolution of the leaching process and the capability for immediate decision for stopping or proceeding with the ongoing extraction. Very importantly, accurate determination of the various orthophosphate pools is ensured by minimization of the hydrolysis of extracted organic phosphorus and condensed inorganic phosphates within the time frame of the assay. The potential of the novel system for accommodation of the harmonized protocol from the Standards, Measurement and Testing (SMT) Program of the Commission of the European Communities for inorganic phosphorus fractionation was also addressed. Under the optimized conditions, the lowest detectable concentration at the 3sigma level was

Enhancement effect study of some organic acids on the calcium availability of vegetables: application of the dynamic in vitro simulated gastrointestinal digestion method with continuous-flow dialysis.

The effect of added organic acids on the calcium availability of vegetables was investigated using the dialysis profiles obtained from an in vitro simulated gastrointestinal digestion with continuous-flow dialysis method. Citric acid was the most effective enhancer followed by tartaric, malic, and ascorbic acids. For amaranth, which has a low calcium availability (5.4%), a significant increase of availability was observed with increasing concentrations of all acids studied. With the continuous-flow dialysis approach, organic acids could be observed to promote the dialyzability even at an elevated intestinal pH. An enhancement effect from added organic acids was not clearly observed for Chinese kale, which itself contains a high amount of available calcium (52.9%).

Development of a simple extraction cell with bi-directional continuous flow coupled on-line to ICP-MS for assessment of elemental associations in solid samples.

A continuous-flow system comprising a novel, custom-built extraction module and hyphenated with inductively coupled plasma-mass spectrometric (ICP-MS) detection is proposed for assessing metal mobilities and geochemical associations in soil compartments as based on using the three step BCR (now the Measurements and Testing Programme of the European Commission) sequential extraction scheme. Employing a peristaltic pump as liquid driver, alternate directional flows of the extractants are used to overcome compression of the solid particles within the extraction unit to ensure a steady partitioning flow rate and thus to maintain constant operationally defined extraction conditions. The proposed flow set-up is proven to allow for trouble-free handling of soil samples up to 1 g and flow rates < or =10 mL min(-1). The miniaturized extraction system was coupled to ICP-MS through a flow injection interface in order to discretely introduce appropriate extract volumes to the detector at a given time and with a given dilution factor. The proposed hyphenated method demonstrates excellent performance for on-line monitoring of major and trace elements (Ca, Mn, Fe, Ni, Pb, Zn and Cd) released when applying the various extracting reagents as addressed in the BCR scheme, that is, 0.11 M CH(3)COOH, 0.1 NH(2)OH.HCl and 30% H(2)O(2), even when a well recognized matrix-sensitive detector, such as ICP-MS, is used. As a result of the enhanced temporal resolution of the ongoing extraction, insights into the breaking down of phases and into the kinetics of the metal release are obtained. With the simultaneous multielement detection capability of ICP-MS, the dynamic fractionation system presents itself as an efficient front-end for evaluation of actual elemental association by interelement comparison of metals leached concurrently during the extraction time. Thus, the intimate elemental association between Cd and Zn in contaminated soils could be assessed.

Observation of salt-induced beta-lactoglobulin aggregation using sedimentation field-flow fractionation.

Sedimentation field-flow fractionation (SdFFF) was applied in order to characterize particle sizes of beta-lactoglobulin aggregates induced by Ca2+ or Zn2+. Aggregation induced by Zn2+ was faster than that induced by Ca2+. Effects of Zn2+ and beta-lactoglobulin concentrations, as well as contact time, on the aggregation of beta-lactoglobulin were examined. All factors exhibited a combined effect on the size of aggregates, whereby larger aggregates were obtained at increased concentrations of Zn2+ and beta-lactoglobulin. At fixed concentrations of 2% (w/v) beta-lactoglobulin and 10 mM Zn2+, the particle size of the aggregates increased from 0.19 microm (at 15 min) to 0.38 microm (at 2880 min). Further, a hyphenated technique of SdFFF and inductively coupled plasma-optical emission spectrometry (ICP-OES) was used to examine whether intermolecular ionic bridges take part in salt-induced beta-lactoglobulin aggregation. With SdFFF-ICP-OES, protein-cation-protein cross-linkages were observed for beta-lactoglobulin aggregation induced by Zn2+, but not for that induced by Ca2+.

Iron fractionation for corrosion products from natural gas pipelines by continuous-flow sequential extraction.

The forms and quantities of iron species in corrosion product samples from natural gas pipelines were examined, using a continuous-flow sequential extraction system. Sequential extraction consists of four steps that dissolve water soluble iron (FeSO4), acid soluble iron (FeCO3), reducible iron (Fe-(oxyhydr)oxides) and oxidisable iron (FeS2) fractions, respectively. Selectivity of extracting reagents for particular iron species was evaluated by determination of co-extracted anions, using ion chromatography, and evolved CO2, using indirect flame atomic absorption spectrometer (FAAS). Iron was found predominantly in the reducible fraction (61-99%), indicating that Fe-(oxyhydr)oxides are the major constituents of the corrosion products.

On-line dynamic fractionation and automatic determination of inorganic phosphorus in environmental solid substrates exploiting sequential injection microcolumn extraction and flow injection analysis.

Sequential injection microcolumn extraction (SI-MCE) based on the implementation of a soil-containing microcartridge as external reactor in a sequential injection network is, for the first time, proposed for dynamic fractionation of macronutrients in environmental solids, as exemplified by the partitioning of inorganic phosphorus in agricultural soils. The on-line fractionation method capitalises on the accurate metering and sequential exposure of the various extractants to the solid sample by application of programmable flow as precisely coordinated by a syringe pump. Three different soil phase associations for phosphorus, that is, exchangeable, Al- and Fe-bound, and Ca-bound fractions, were elucidated by accommodation in the flow manifold of the three steps of the Hieltjes-Lijklema (HL) scheme involving the use of 1.0M NH4Cl, 0.1M NaOH and 0.5M HCl, respectively, as sequential leaching reagents. The precise timing and versatility of SI for tailoring various operational extraction modes were utilized for investigating the extractability and the extent of phosphorus re-distribution for variable partitioning times. Automatic spectrophotometric determination of soluble reactive phosphorus in soil extracts was performed by a flow injection (FI) analyser based on the Molybdenum Blue (MB) chemistry. The 3sigma detection limit was 0.02 mg P L(-1) while the linear dynamic range extended up to 20 mg P L(-1) regardless of the extracting media. Despite the variable chemical composition of the HL extracts, a single FI set-up was assembled with no need for either manifold re-configuration or modification of chemical composition of reagents. The mobilization of trace elements, such as Cd, often present in grazed pastures as a result of the application of phosphate fertilizers, was also explored in the HL fractions by electrothermal atomic absorption spectrometry.

Dynamic continuous-flow dialysis method to simulate intestinal digestion for in vitro estimation of mineral bioavailability of food.

A system for dynamic continuous-flow dialysis during intestinal digestion for an in vitro simulation of gastrointestinal digestion is presented as an alternative to human and animal in vivo methods for estimation of the bioavailability of minerals. The method is based on the in vitro batch dialysis method described by Miller, which was developed into a continuous-flow system of a simple design to perform dynamic dialysis in the intestinal digestion stage. A flow dialysis system has the advantages of simulation being close to in vivo physiological conditions because pH change during dialysis is gradual and dialyzed components are continuously removed. The proposed new design performed dialysis during a continuous flow of dialyzing solution (NaHCO(3)) around a dialysis bag containing peptic digest, which is placed inside a glass dialysis chamber. Gradual change of dialysis pH, similar to that occurring in the gastrointestinal tract, was obtained by optimization of flow rate and concentration of NaHCO(3). The dialysate collected in fractions was analyzed to determine dialyzed minerals and pH change in the course of dialysis. The method was tested by determination of calcium bioavailability of powder milk and calcium carbonate tablets.