Acid Silver Nitrate Research Articles

Green synthesis, characterization, and biological evaluation of gold and silver nanoparticles using Mentha spicata essential oil

Green synthesis of bioactive nanoparticles (NPs) is getting more attractive in various fields of science including the food industry. This study investigates the green synthesizing and characterization of gold NPs (AuNPs) and silver NPs (AgNPs) produced using Mentha spicata L. (M. spicata) essential oil as well as their antibacterial, antioxidant, and in vitro cytotoxic effects. The essential oil was mixed with both Chloroauric acid (HAuCl4) and aqueous silver nitrate (AgNO3) solutions separately and incubated at room temperature for 24 h. The chemical composition of the essential oil was identified by gas chromatography coupled with a mass spectrometer detector (GC–MS). Au and Ag nanoparticles were characterized using UV–Vis spectroscopy, transmission electron microscopy, scanning electron microscopy, dynamic light scattering (DLS), X-ray diffraction (XRD) and Fourier transform infrared (FTIR). The cytotoxicity of both types of nanoparticles was evaluated using MTT assay on cancerous HEPG-2cell line by exposing them to various concentrations of both NPs for 24 h. The antimicrobial effect was evaluated by the well-diffusion technique. The antioxidant effect was determined by DPPH and ABTS tests. According to the results of GC–MS analysis, 18 components were identified, including carvone (78.76%) and limonene (11.50%). UV–visible spectroscopy showed a strong absorption peak of 563 nm and 485 nm, indicating the formation of Au NPs and Ag NPs, respectively. TEM and DLS demonstrated that AuNPs and AgNPs were predominantly spherical shaped with average sizes of 19.61 nm and 24 nm, respectively. FTIR analysis showed that biologically active compounds such as monoterpenes could assist in the formation and stabilization of both types of NPs. Additionally, XRD provided more accurate results, revealing a nano-metal structure. Silver nanoparticles exhibited better antimicrobial activity against the bacteria than AuNPs. Zones of inhibition ranging 9.0–16.0 mm were recorded for the AgNPs, while zones of 8.0–10.33 mm were observed AuNPs. In the ABTS assay, the AuNPs and AgNPs showed a dose-dependent activity and synthesized nanoparticles exhibited higher antioxidant activity than MSEO in both assays. Mentha spicata essential oil can be successfully used for the green production of Au NPs and Ag NPs. Both green synthesized NPs show antibacterial, antioxidant, and in vitro cytotoxic activity.

Single layer synthesis of silver nanoparticles with controlled filling fraction and average particle size

Single-layer silver nanoparticles have been grown on quartz substrates by a one-pot synthesis method using tannic acid as a reducing agent. The area filling fraction and average nanoparticle sizes were found to depend on the tannic acid pre-treatment and silver nitrate reduction times. Increasing these two parameters enabled single-layer silver nanoparticles to be fabricated with area filling fractions and average nanoparticle sizes that were controlled from 7.2% to 50%, and from 25 nm to 40 nm, respectively. The silver nanoparticles were anchored onto the quartz surface by a tannic acid layer bonded to silanol groups. Localized surface plasmonic resonance from the silver nanoparticles was observed where the peak wavelength was controlled by the synthesis conditions. Surface enhanced Raman scattering, and surface enhanced photoluminescence were also observed. Our one-pot method to produce single-layer silver nanoparticles offers a promising approach for applications in plasmonic microdevices and biosensors.

Au/Ag nanoparticles-decorated TiO2 with enhanced catalytic activity for nitroarenes reduction

A straightforward and environmentally-friendly approach for the fabrication of TiO2 supported nano-Au and Ag catalysts with enhanced activity in nitroarenes reduction is presented. The immobilization of the metal nanoparticles (NPs) onto TiO2 was performed through a first step of metal precursors adsorption (tetrachloroauric(III) acid trihydrate or silver(I) nitrate) onto TiO2, followed by a step of in situ metal cations reduction using three types of reducing agents: citric acid, NaBH4 and simulated sunlight irradiation. The type of reducing agent influenced the size, the oxidation state and loading of the grafted metal NPs. The Au-based nanocomposites contained Au NPs with sizes ranging between 19.3 and 28.2 nm and Au loadings in the range of 7.2–19.8 wt%. NaBH4 was the best reducing agent for the Au NPs immobilization onto TiO2, leading to the highest Au loading (19.8 wt%) and lowest Au+/Au0 ratio (0.07). In the case of the Ag-based materials, citric acid revealed to be the best reducing agent for the Ag NPs immobilization onto TiO2, leading to ultrasmall grafted NPs, 10.1 wt% Ag loading and the highest amount of metallic silver (Ag+/Ag0 ratio = 0.03).The catalytic performance of the Au/Ag-based TiO2 nanocomposites was evaluated in the reduction of 4-nitrophenol (4-NP) and 4-nitroaniline (4-NA) in aqueous medium, at room temperature, using NaBH4 as reducing agent (substrate:reducing agent:catalyst weight ratio = 0.007:1.89:1). The Au- and Ag-based nanocomposites (prepared with NaBH4 and citric acid, respectively) led to 100% conversion of 4-NP within 260 and 40 s, respectively, with rate constants (k) of 19.1 × 10−3 and 94.2 × 10−3 s−1 (pseudo-first-order kinetics), respectively, demonstrating the higher performance of the Ag-based catalyst. In contrast, in the case of the 4-NA reduction, the highest catalytic performance was achieved for the Au-based material, promoting the total substrate conversion within 90 s (k = 29.4 ×10−3 s−1), while for the Ag-based catalyst the total 4-NA conversion was achieved within 120 s (k = 16.6 ×10−3 and 27.5 ×10−3 s−1). Both catalysts were reused in nine consecutive cycles in both 4-NP and 4-NA reduction, with the Au-based material presenting higher stability, especially for 4-NA reduction, with only a small reaction time increment.

Brief descriptions of the principles of prominent methods used to study the penetration of materials into human hair and a review of examples of their use.

Consumers are attracted to the latest fashion trends and different looks. This drives the search for novel hair treatments. Some chemicals present in hair treatment products can penetrate the hair shaft. These materials can either nourish or injure the hair cortex. Different techniques have been used to investigate the mechanism of molecule penetration and the conditions under which penetration occurs. This article reviews the techniques applied for this purpose. Various microscopy techniques are used to capture clear and colourful images to determine the diffusion pathways and the exact location of the molecules under study. However, the laborious sample preparation often leads to sample destruction since cross-sectioning is often required. While various other techniques have been successfully used for investigating the penetration methods, most of these require different amounts of work to be put in for sample preparation and instrumentation. Several spectroscopic techniques have been used to study the penetration of the molecules because of the high levels of accuracy and the quick response time of these techniques. Moreover, the samples are not damaged during the investigation.

Reversible Silver Electroplating and Electrostripping in the Gel Electrolyte for Smart Mirror

The smart glass which can be switched between the colored state and the transparent state has been widely investigated for control of light intensity and thermal energy saving. However, it has a drawback that the colored portion absorbs light and radiates heat inside. Recently, the smart silver mirror has been reported by Kobayashi [1] and our group [2], which can switch between the mirror state and the transparent state reversibly. the electroplated silver metal mirror state has an advantage to reflect light without radiating heat to the inside. From this point, the smart silver mirror would be expected as an alternative to the smart glass. Since the electrolyte solution has been used in the smart silver mirror devices reported so far, the gelation of the electrolyte solution is needed in order to eliminate the possibility of liquid leakage and evaporation. We reported that addition of polymethyl methacrylate (PMMA) into the plating electrolyte solution didn’t affect the device performance even when the diffusion rate of silver ions became slow due to increase in viscosity. In this report, crosslink points were created by modifying both ends of PMMA with carboxyl groups as a functional group. The crosslinkage of the plating electrolyte solution three-dimensionally has been performed by oxazoline.The plating electrolyte solution used in this experiment was prepared as follows. First, citric acid monohydrate and silver nitrate were dissolved in the solvent acetonitrile and 1-ethyl-3-methylimidazolium bis (trifluoromethanesulfonyl) imide in the same amount as acetonitrile. The telechelic polymer having functional groups at both ends was synthesized by the following method. [3] Methyl methacrylate (MMA) as a monomer, 4-cyano-4-(thiobenzoylthio) pentanoic acid as a raft agent and 4,4'-azobis (4-cyanovaleric acid) (ACVA) as an initiator were reacted in dry DMF solvent at 80 ℃. After reacting for 6 hours, a product having a carboxyl group at one end was obtained. The resulting polymer was reacted with ACVA in dry DMF solvent at 80 ℃. After reacting for 24 hours, a telechelic polymer having a carboxyl group at both ends was obtained. The crosslinking reaction was tried by adding a compound having an epoxy group or an oxazoline group into the plating electrolyte solution including the telechelic polymer. The polymer with carboxyl groups at both ends was reacted with triglycidyl isocyanurate at room temperature for 24 hours and at 70℃ for 4 hours, but the reaction did not proceed. Instead of epoxy group, the coupling reaction between the oxazoline group and the carboxyl group was carried out. 1,3-bis(4,5-dihydro-2-oxazolyl) benzene was reacted at 75℃ for 4 hours. The state of the gelled solution after the reaction was confirmed by upsetting the sample bottle. Comparing with the states before and after the coupling, the viscosity increased significantly after the coupling. It shows that the coupling reaction between the oxazoline group and the carboxyl group occurred. However, after a while, the solution had flowed through the wall of the sample bottle and was not completely gelled. This is because there are only two crosslinking points with oxazoline. If the amount of the polymer addition further increases, it becomes a highly viscous liquid before the reaction. The high viscosity makes it difficult when the solution is injected into the device using a needle. Therefore, the viscosity before the reaction is required to keep low. In the present, we will try to synthesize trioxazoline having three oxazoline groups and perform electrochemical measurement in the plating bath after crosslinking.Reference[1] S. Araki, et al, Adv. Mater., 24, OP122(2012).[2] A. Aoki et al, Sol. Energy Mater. Sol. Cells, 200, 109922(2019).[3] N. Greving, et al, Macromol. Chem. Phys., 213, 1465(2012).

Self-healable and dual-functional guar gum-grafted-polyacrylamidoglycolic acid-based hydrogels with nano-silver for wound dressings

Dual-functional carbohydrate polymer-based silver nanocomposite (AgNC) hydrogels with self-healing, injectable, and bacterial inactivation properties have attracted particular attention in the wound dressing field. In this study, a rapid formation of AgNC hydrogels were prepared via in situ addition of guar gum-grafted-polyacrylamidoglycolic acid (GG-g-PAGA) polymer and silver nitrate (AgNO3) and sodium borohydride (NaBH4). The GG-g-PAGA polymer and its AgNC hydrogels were analyzed by FTIR, 1H and 13C NMR, UV–vis spectra, FE-SEM, EDX, and FE-TEM. The GG-g-PAGA@AgNC hydrogels exhibited self-healing ability, injectability, stretchability, flowability, high swelling, porosity, upright mechanical behavior, and biodegradability. Moreover, their bacterial inactivation and cytotoxicity were tested against wound pathogens and skin fibroblast cells, respectively. Therefore, incorporating GG-g-PAGA@AgNC hydrogels could be a versatile strategy to speed up wound healing processes, but a clinical trial is still required for its medical applications.

Tapping Opportunity of Tiny-Shaped Particles and Role of Precursor in Developing Shaped Particles

Metallic colloids are frequently used in industry and provide understanding of science at microns to nanometers scales along with their applicability for various technologically important applications. Present investigations deal with morphology and structure of gold, silver and their binary composition while processing certain amounts of their solutions in a newly designed process and tapping opportunities of developing tiny-shaped particles. At tuned ratio of pulse OFF to ON time and when gold solution was processed, several tiny-shaped particles developed at the solution’s surface. Such tiny particles exert force at the tip of each converting their structure of smooth element where steady-state immersing behavior directed them toward a common centre resulting into bind them for developing different geometric anisotropic shaped particles. Under identical parameters along with pulse time, processing solutions of silver nitrate and binary composition of chloroauric acid-silver nitrate result in the development of tiny particles having no specific shape where their assembling is under the mixed behavior of forces resulting in distorted particles. Elongation and deformation of gold and silver atoms while developing different structures are because of the plastically driven behavior of their electrons. In three-dimensional structures where atoms do not undergo transition to elongate, they retain the structure as it is, which is known as hcp structure or two-dimensional structure. Different nature of precursors along with morphology and structure of particles are discussed in this paper opening abundant avenues for research.

Synthesis of gold nanorods with a longitudinal surface plasmon resonance peak of around 1250 nm

We prepared gold nanorods and joined them to chemicals such as tetrachloauric (III) acid trihydrate, silver nitrate, hydroquinone, hexadecyltrimethylammonium bromide, sodium hydroxide and sodium borohydride using the seed-mediated method. The combination of hydroquinone, with or without salicylic acid, influences the size of the gold nanorods, and this is demonstrated by the results of TEM images, UV–vis spectra and the value of the longitudinal surface plasmon resonance peak with respect to the UV–vis spectra. By changing the Ag+ ion and hydroquinone concentration and the combination of hydroquinone and salicylic acid, the size of the gold nanorods can be controlled and this is manifested by longitudinal surface plasmon resonance peaks forming between 875 and 1278 nm. In particular, sample E2 achieved a longitudinal surface plasmon peak at 1273 nm and an aspect ratio of more than 10 by modifying the hydroquinone to 2.5 mM and salicylic acid to 0.5 mM concentration in the growth solution.

Phosphate-assisted one-pot synthesis of silver phosphate–mesoporous silica composite from sodium silicate and silver nitrate

A facile one-pot method for silver phosphate–mesoporous silica composite was reported. In the synthesis procedure, sodium silicate was firstly added dropwise to acidic Pluronic P123 and silver nitrate aqueous solution, followed by addition of phosphate to adjust the pH to near-neutral. Through the salting-out and flocculation effect of phosphate, tiny silver phosphate particles and silicate oligomers were formed and mixed together to build the composite material. It was a new type of mesoporous silica composite which had a structure similar to SBA-15. And it was found to have higher photocatalytic activity than pure silver phosphate in the degradation of methyl orange under ultraviolet light irradiation.

Formation of colloidal silver nanoparticles stabilized by Na +–poly(γ-glutamic acid)–silver nitrate complex via chemical reduction process

Macromolecular and polyanionic Na +–poly(γ-glutamic acid) (PGA) silver nitrate complex acted as both a metal ion provider and a particle protector to fabricate nanosized silver colloids under chemical reduction by dextrose. The formation and size of particles have been characterized from transmission electron microscopy (TEM), dynamic light scattering analysis and UV–vis spectrophotometer. The results showed that the average particle size was 17.2 ± 3.4 to 37.3 ± 5.5 nm, apparently depending on the complex concentration. It was found that the rate constant and conversion of silver nanoparticles were proportional to the concentration of PGA. The growth mechanism of nanosized silver colloid was fully discussed. In addition, the in vitro cytotoxicity evaluated by L929 fibroblasts proliferation and antibacterial activity against Gram-positive strain (methicillin-resistant S. aureus (MRSA)) and Gram-negative strain ( P. aeruginosa) bacteria have been assessed.

Preparation and the mechanisms of formation of silver particles of different morphologies in homogeneous solutions

Uniform, well-dispersed silver particles of various morphologies have been prepared by reducing highly acidic silver nitrate solutions with ascorbic acid in the presence of a sodium naphthalene sulfonate–formaldehyde copolymer as dispersing agent. By varying the temperature of the reaction, the free acid content, the addition rate of the reductant, and the aging time, both isometric and anisotropic silver particles could be obtained. It was found that the latter were formed by aggregation of nanosize subunits, which were identified by electron microscopy and X-ray diffractometry.

Adsorption of Silver onto Activated Carbon from Acidic Media: Nitrate and Sulfate Media

Adsorption of silver from acidic silver nitrate and sulfate media onto a peat-based activated carbon was studied. The effects of pH, temperature, and zinc nitrate and zinc sulfate addition on the adsorption kinetics and capacities were investigated. An XRD study showed that Ag(I) was reduced to Ag(0) on the carbon surface during the adsorption process. Low pH, high zinc salt concentration, and temperature are detrimental to the adsorption of silver. Second-order reactions were involved in the process of silver adsorption with respect to Ag(I). Hydroquinone-like surface oxygen functional groups were probably involved in the reduction reaction of Ag(I) → Ag(0). The addition of butanol to the solution appreciably reduced the adsorption rate and capacity of silver on the activated carbon. This indicates that graphene layer surfaces might also be involved in the Ag(I) → Ag(0) reaction because of the enrichment of π-electrons on the basal planes.

Two modes of nanoleakage expression in single-step adhesives.

Self-etch adhesives that etch, prime, and bond simultaneously should not exhibit incomplete resin infiltration within hybrid layers. We hypothesized that nanoleakage patterns in these systems are artifacts caused by mineral dissolution in mildly acidic silver nitrate. Resin-dentin interfaces bonded with four single-step, self-etch adhesives were examined for nanoleakage by conventional (pH 4.2) and basic ammoniacal (pH 9.5) silver nitrate and prepared for transmission electron microscopy. All adhesives exhibited a reticular mode of nanoleakage within hybrid layers when conventional silver nitrate was used. With ammoniacal silver nitrate, an additional spotted pattern of nanoleakage was observed within adhesive and hybrid layers. The reticular mode of nanoleakage in self-etch adhesives probably represents sites of incomplete water removal that leads to regional suboptimal polymerization. The spotted pattern identified with the use of ammoniacal silver nitrate probably represents potentially permeable regions in the adhesive and hybrid layers that result from the interaction of the basic diamine silver ions with acidic/hydrophilic resin components.

Morphological and immunocytochemical analyses on the effects of diet-induced hypocalcemia on enamel maturation in the rat incisor.

During the maturation stage of amelogenesis, the loss of matrix proteins combined with an accentuated but regulated influx of calcium and phosphate ions into the enamel layer results in the "hardest" tissue of the body. The aim of the present investigation was to examine the effects of chronic hypocalcemia on the maturation of enamel. Twenty-one-day old male Wistar rats were given a calcium-free diet and deionized water for 28 days, while control animals received a normal chow. The rats were perfused with aldehyde and the mandibular incisors were processed for histochemical and ultrastructural analyses and for postembedding colloidal gold immunolabeling with antibodies to amelogenin, ameloblastin, and albumin. The maturation stage enamel organ in hypocalcemic rats exhibited areas with an apparent increase in cell number and the presence of cyst-like structures. In both cases the cells expressed signals for ameloblastin and amelogenin. The content of the cysts was periodic acid-Schiff- and periodic acid-silver nitrate-methanamine-positive and immunolabeled for amelogenin, ameloblastin, and albumin. Masses of a similar material were also found at the enamel surface in depressions of the ameloblast layer. In addition, there were accumulations of glycoproteinaceous matrix at the interface between ameloblasts and enamel. In decalcified specimens, the superficial portion of the enamel matrix sometimes exhibited the presence of tubular crystal "ghosts." The basal lamina, normally separating ameloblasts and enamel during the maturation stage, was missing in some areas. Enamel crystals extended within membrane invaginations at the apical surface of ameloblasts in these areas. Immunolabeling for amelogenin, ameloblastin, and albumin over enamel was variable and showed a heterogeneous distribution. In contrast, enamel in control rats exhibited a homogeneous labeling for amelogenin, a concentration of ameloblastin at the surface, and weak reactivity for albumin. These results suggest that diet-induced chronic hypocalcemia interferes with both cellular and extracellular events during enamel maturation.

Fluorescence detection of proteins in sodium dodecyl sulfate-polyacrylamide gels using environmentally benign, nonfixative, saline solution

SYPRO Tangerine stain is an environmentally benign alternative to conventional protein stains that does not require solvents such as methanol or acetic acid for effective protein visualization. Instead, proteins can be stained in a wide range of buffers, including phosphate-buffered saline or simply 150 mM NaCl using an easy, one-step procedure that does not require destaining. Stained proteins can be excited by ultraviolet light of about 300 nm or with visible light of about 490 nm. The fluorescence emission maximum of the dye is approximately 640 nm. Noncovalent binding of SYPRO Tangerine dye is mediated by sodium dodecyl sulfate (SDS) and to a lesser extent by hydrophobic amino acid residues in proteins. This is in stark contrast to acidic silver nitrate staining, which interacts predominantly with lysine residues or Coomassie Blue R, which in turn interacts primarily with arginine and lysine residues. The sensitivity of SYPRO Tangerine stain is similar to that of the SYPRO Red and SYPRO Orange stains - about 4—10 ng per protein band. This detection sensitivity is comparable to colloidal Coomassie blue staining and rapid silver staining procedures. Since proteins stained with SYPRO Tangerine dye are not fixed, they can easily be eluted from gels or utilized in zymographic assays, provided that SDS does not inactivate the protein of interest. This is demonstrated with in-gel detection of rabbit liver esterase activity using α-naphthyl acetate and Fast Blue BB dye as well as Escherichia coli β-glucuronidase activity using ELF-97 β-D-glucuronide. The dye is also suitable for staining proteins in gels prior to their transfer to membranes by electroblotting. Gentle staining conditions are expected to improve protein recovery after electroelution and to reduce the potential for artifactual protein modifications such as the alkylation of lysine and esterification of glutamate residues, which complicate interpretation of peptide fragment profiles generated by mass spectrometry.

Fluorescence detection of proteins in sodium dodecyl sulfate-polyacrylamide gels using environmentally benign, nonfixative, saline solution.

SYPRO Tangerine stain is an environmentally benign alternative to conventional protein stains that does not require solvents such as methanol or acetic acid for effective protein visualization. Instead, proteins can be stained in a wide range of buffers, including phosphate-buffered saline or simply 150 mM NaCl using an easy, one-step procedure that does not require destaining. Stained proteins can be excited by ultraviolet light of about 300 nm or with visible light of about 490 nm. The fluorescence emission maximum of the dye is approximately 640 nm. Noncovalent binding of SYPRO Tangerine dye is mediated by sodium dodecyl sulfate (SDS) and to a lesser extent by hydrophobic amino acid residues in proteins. This is in stark contrast to acidic silver nitrate staining, which interacts predominantly with lysine residues or Coomassie Blue R, which in turn interacts primarily with arginine and lysine residues. The sensitivity of SYPRO Tangerine stain is similar to that of the SYPRO Red and SYPRO Orange stains - about 4-10 ng per protein band. This detection sensitivity is comparable to colloidal Coomassie blue staining and rapid silver staining procedures. Since proteins stained with SYPRO Tangerine dye are not fixed, they can easily be eluted from gels or utilized in zymographic assays, provided that SDS does not inactivate the protein of interest. This is demonstrated with in-gel detection of rabbit liver esterase activity using alpha-naphthyl acetate and Fast Blue BB dye as well as Escherichia coli beta-glucuronidase activity using ELF-97 beta-D-glucuronide. The dye is also suitable for staining proteins in gels prior to their transfer to membranes by electroblotting. Gentle staining conditions are expected to improve protein recovery after electroelution and to reduce the potential for artifactual protein modifications such as the alkylation of lysine and esterification of glutamate residues, which complicate interpretation of peptide fragment profiles generated by mass spectrometry.

Alloy Formation of Gold−Silver Nanoparticles and the Dependence of the Plasmon Absorption on Their Composition

Gold−silver alloy nanoparticles with varying mole fractions are prepared in aqueous solution by the co-reduction of chlorauric acid HAuCl4 and silver nitrate AgNO3 with sodium citrate. As the optical absorption spectra of their solutions show only one plasmon absorption it is concluded that mixing of gold and silver leads to a homogeneous formation of alloy nanoparticles. The maximum of the plasmon band blue-shifts linearly with increasing silver content. This fact cannot be explained by a simple linear combination of the dielectric constants of gold and silver within the Mie theory. On the other hand, the extinction coefficient is found to decrease exponentially rather than linearly with increasing gold mole fraction xAu. Furthermore, the size distribution of the alloy nanoparticles is examined using transmission electron microscopy (TEM). High-resolution TEM (HRTEM) also confirms the formation of homogeneous gold−silver alloy nanocrystals.

Pitfalls in the supramolecular assembly of silver(I) coordination compounds

The syntheses and crystal structures of (6-methylnicotinic acid) (6- methylnicotinato)silver(I), di (6-methylnicotinic acid) silver(I) nitrate, (2-chloro-6-methylnicotinato) silver(I), di (2-chloro-6-methylnicotinic acid) silver(I) nitrate, and (2-methylni-cotinic acid) (2-methylnicotinato) silver(I) are described. These coordination complexes were synthesized under the same conditions and with very similar ligands but their resulting structures are quite different, in part due to the degree of protonation of the nicotinic acid ligand(s). The structures vary from coordination polymers to hydrogen-bonded coordination dimers, to linear structures linked by anion-carboxylic acid hydrogen bonds. This study illustrates some of the difficulties involved in predicting hydrogen-bonded networks in transition-metal systems which contain carboxylic acid moieties and coordinatively unsaturated metal ions.

Further compositional analyses of flax: Mucilage, trypsin inhibitors and hydrocyanic acid

AbstractRegistered Canadian cultivars of flax, and laboratory‐prepared and commercially obtained samples of linseed meal (LM), were used to determine extract viscosity and mucilage, trypsin inhibitors and hydrocyanic acid (HCN) concentrations. The mucilage readily leached out from the seed coat (hull) fragments soaked in water, leaving behind pentagon‐shaped cells that could be seen clearly in scanning electron micrographs. Extract viscosity significantly varied in the laboratory‐prepared (23–48 cS) and commercially obtained (30–68 cS) samples of LM and may be used to obtain an indirect, qualitative estimate of flax mucilage. Mucilage was extracted from whole seed in 5.0–5.3% yields and contained 20–24% protein (about 10% ash and 30% total carbohydrates). Laboratory‐prepared LM (raw) contained 42–51 units of trypsin inhibitor activity, commercially obtained samples, 14–37 units, and raw rapeseed and soybean meals, 99 and 1650 units, respectively. Picric acid tests (qualitative) showed only traces of HCN in ten cultivars of freshly ground flax. The acid silver nitrate titration procedure measured HCN quantitatively, but showed its presence only in three of the five cultivars investigated. HCN was conveniently measured by a colorimetric procedure (barbituric acidpyridine reaction), which may be used to screen flax cultivars. HCN content of flax was significantly influenced by environments (growth location and season) and, to a less extent, by cultivar.

Determination of fluorine and iodine in biological materials

Fluorine and iodine were determined in some biological reference materials. Radiochemical neutron activation analysis was used for iodine and ion-selective potentiometry for fluorine. The two elements were separated from the matrix elements by pyrohydrolysis in the presence of vanadium(V) oxide. The volatile compounds were absorbed in sodium hydroxide solution for the determination of fluorine and in acidic silver nitrate solution for the determination of iodine. This method gives low detection limits with small sample sizes.