Influence of long-range forces and capillarity on the function of underwater superoleophobic wrinkled surfaces

Underwater superoleophobic surfaces can be considered a particular type of lubricant-infused surface, that have anti-fouling properties by virtue of a trapped water layer that repels oils. However, as their function relies on a water layer being trapped in the surface roughness, it is crucial to understand the factors that determine the layer stability. In this work, the forces that are responsible for the stability of thin liquid films within structured surfaces were quantified, and the conclusions were tested against the performance of wrinkled surfaces as underwater superoleophobic coatings. Here, the system studied was a family of wrinkled surfaces made of hydrophilic poly(4-vinylpyridine) (P4VP), whereby the wrinkle width could be controllably tuned in the range 90 nm to 8000 nm. The van der Waals free energy was quantified and the capillary forces trapping water in the surface micro- and nano-wrinkle structure were estimated. P4VP surfaces with micro-scale wrinkles had underwater superoleophobic properties, and low adhesion to different oils with droplet roll-off angle below 6° ± 1°. Despite the van der Waals free energy of the system pointing to the dewetting of a water film under oil on top of a smooth P4VP film, the wrinkled structure is sufficient to induce a Cassie state with a trapped water layer. The micro-scale wrinkles (average width 4-12 μm) were found to be particularly effective in the trapping of the water in a Cassie non-adhesive state. The P4VP wrinkled surfaces are superamphiphobic, as when they were first infused with oil, and then exposed to a droplet of water under oil, they exhibited superhydrophobic behavior. The P4VP wrinkles have the additional useful feature of being transparent underwater, which makes them useful candidates for the protection of underwater cameras and sensors.

Marine Antifouling Behavior of Lubricant-Infused Nanowrinkled Polymeric Surfaces

A new family of polymeric, lubricant-infused, nanostructured wrinkled surfaces was designed that effectively retains inert nontoxic silicone oil, after draining by spin-coating and vigorous shear for 2 weeks. The wrinkled surfaces were fabricated using three different polymers (Teflon AF, polystyrene, and poly(4-vinylpyridine)) and two shrinkable substrates (Polyshrink and shrinkwrap), and Teflon on Polyshrink was found to be the most effective system. The volume of trapped lubricant was quantified by adding Nile red to the silicone oil before infusion and then extracting the oil and Nile red from the surfaces in heptane and measuring by fluorimetry. Higher volumes of lubricant induced lower roll-off angles for water droplets, and in turn induced better antifouling performance. The infused surfaces displayed stability in seawater and inhibited growth of Pseudoalteromonas spp. bacteria up to 99%, with as little as 0.9 μL cm^-2 of the silicone oil infused. Field tests in the waters of Sydney Harbor over 7 weeks showed that silicone oil infusion inhibited the attachment of algae, but the algal attachment increased as the silicone oil was slowly depleted over time. The infused wrinkled surfaces have high transparency and are moldable, making them suited to protect the windows of underwater sensors and cameras.

Fouling-release and chemical activity effects of a siloxane-based material on tunicates

The antifouling performance of a siloxane-based elastomeric impression material (EIM) was compared to that of two silicone fouling-release coatings, Intersleek 757 and RTV-11. In field immersion trials, the EIM caused the greatest reduction in fouling by the solitary tunicate Ciona intestinalis and caused the longest delay in the progression of fouling by two species of colonial tunicate. However, in pseudobarnacle adhesion tests, the EIM had higher attachment strengths. Further laboratory analyses showed that the EIM leached alkylphenol ethoxylates (APEs) that were toxic to C. intestinalis larvae. The EIM thus showed the longest duration of chemical activity measured to date for a siloxane-based coating (4 months), supporting investigations of fouling-release coatings that release targeted biocides. However, due to potential widespread effects of APEs, the current EIM formulation should not be considered as an environmentally-safe antifoulant. Thus, the data also emphasize consideration of both immediate and long-term effects of potentially toxic constituents released from fouling-release coatings.

In Situ Confocal Raman Microscopy of Hydrated Early Stages of Bacterial Biofilm Formation on Various Surfaces in a Flow Cell

Bacterial biofilms are precursors to biofouling by other microorganisms. Understanding their initiation may allow us to design better ways to inhibit them, and thus to inhibit subsequent biofouling. In this study, the ability of confocal Raman microscopy to follow the initiation of biofouling by a marine bacterium, Pseudoalteromonas sp. NCIMB 2021 (NCIMB 2021), in a flow cell, using optical and confocal Raman microscopy, was investigated. The base of the flow cell comprised a cover glass. The cell was inoculated and the bacteria attached to, and grew on, the cover glass. Bright field images and Raman spectra were collected directly from the hydrated biofilms over several days. Although macroscopically the laser had no effect on the biofilm, within the first 24 h cells migrated away from the position of the laser beam. In the absence of flow, a buildup of extracellular substances occurred at the base of the biofilm. When different coatings were applied to cover glasses before they were assembled into the flow cells, the growth rate, structure, and composition of the resulting biofilm was affected. In particular, the ratio of Resonance Raman peaks from cytochrome c (CC) in the extracellular polymeric substances, to the Raman phenylalanine (Phe) peak from protein in the bacteria, depended on both the nature of the surface and the age of the biofilm. The ratios were highest for 24 h colonies on a hydrophobic surface. Absorption of a surfactant with an ethyleneoxy chain into the hydrophobic coating created a surface similar to that given with a simple PEG coating, where bacteria grew in colonies away from the surface rather than along the surface, and CC:Phe ratios were initially low but increased at least fivefold in the first 48 h.

Interactions of protamine with the marine bacterium, Pseudoalteromonas sp. NCIMB 2021

Pseudoalteromonas sp. NCIMB 2021 (NCIMB 2021) was grown in synthetic seawater (SSW) containing pyruvate, in the presence (SSW(++) ) and absence (SSW(-) ) of divalent cations. Cultures contained single cells. Addition of the cationic antibacterial peptide (CAP), protamine, did not inhibit, but rather increased, the growth of NCIMB 2021 in SSW(++) and caused the bacteria to grow in chains. Bacterial growth was assessed using turbidity, cell counts and the sodium salt of resazurin. In SSW(-) , NCIMB 2021 was no longer resistant to protamine. The minimum inhibitory concentration (MIC) was 5 mg ml(-1) .

SIGNIFICANCE AND IMPACT OF THE STUDY

Protamine is a cationic antimicrobial peptide (CAP), which is active against a variety of bacteria. This is the first in-depth study of the interaction of protamine with a marine bacterium, Pseudoalteromonas sp. NCIMB 2021. Our results show that protamine is only active in seawater in the absence of divalent cations. In the presence of the divalent cations, Mg(2+) and Ca(2+) , protamine enhances the growth of Pseudoalteromonas sp. NCIMB 2021 and produces chains rather than individual cells. These are important considerations when deciding on applications for protamine and in terms of understanding its mechanism of action.

A comparison of Pseudomonas aeruginosa biofilm development on ZnSe and TiO2 using attenuated total reflection Fourier transform infrared spectroscopy

The growth of Pseudomonas aeruginosa PAO1 biofilms on ZnSe internal reflection elements (IREs) was compared with their growth on TiO(2)-coated ZnSe over several days using attenuated total reflection Fourier transform infrared (ATR-FT-IR) spectroscopy. The effect of the TiO(2) coating on the IR spectra of reference compounds and cell suspensions was determined to aid in the interpretation of the data. The presence of TiO(2) on the surface of a ZnSe IRE tripled the size of the amide II peak and facilitated the detection of pyoverdin production due to its increased adsorption on the coated surface. A 50% increase in the length of the lag phase was observed for PAO1 growth on TiO(2)-coated surfaces as compared to growth on ZnSe. Biofilms on both surfaces exhibited a growth maximum for all components, followed by restructuring at the surface characterized by a decrease in the signal. The composition of biofilms grown on TiO(2) was relatively constant after the restructuring phase, while the extracellular polymeric substance (EPS) component of the biofilms grown on ZnSe gradually increased. The peak due to the carbohydrate component of EPS was much larger in the spectra of biofilms than in those of planktonic cells. The increase of the pyoverdin signal over time in the spectra of the biofilms on TiO(2) closely followed the overall increase in biomass. However, no signal from pyoverdin was detected in the presence of ferric ions.

Tuning the surface-enhanced Raman scattering effect to different molecular groups by switching the silver colloid solution pH

Silver colloids were produced for surface-enhanced Raman scattering (SERS) experiments using hydroxylamine hydrochloride as the reduction agent. The roles of hydroxylamine hydrochloride and bulk solution pH values in the formation of functional groups on the surface of silver colloids and in determining the dimensions of silver colloids were examined using Raman, Fourier transform infrared (FT-IR) and ultraviolet-visible (UV-Vis) spectroscopy, atomic force microscopy (AFM), and zeta-size measurements. The spectrum of hydroxylamine hydrochloride reduced silver colloids was compared with the spectrum of sodium borohydride reduced colloids. The effect of colloid solution pH on SERS results was demonstrated using analyte molecules with biological significance, such as ribonucleic acid, egg albumin, L-alpha-phosphatidylcholine, and glucose. In general, it was shown that at high pH values the SERS effect was more pronounced due to the surface functional groups and colloid dimensions, and sharp, high spectral intensity values were obtained. At low pH values, protonation and rapid aggregation of colloids occurred and the surface chemistry was different. Depending on the analyte, bands were shifted, broadened, and/or the enhancement effect was reduced. Using Pseudomonas aeruginosa PAO1 and Streptococcus mutans it was also shown that by changing the solution bulk pH value, it was possible to enhance the response from different molecular groups in the bacteria and obtain different spectra from the same bacteria strain and the process was reversible. It was concluded that it is possible to produce site- or molecule-specific metal colloids and to tune the SERS effect to certain functional groups of analytes by means of the pH of colloidal suspension.

A confocal Raman microscopy study of the distribution of a carotene-containing yeast in a living Pseudomonas aeruginosa biofilm

The distribution of a carotene-containing yeast (CCY) in a biofilm formed by a small colony variant (SCV) of Pseudomonas aeruginosa PA01 was followed by confocal Raman microspectroscopy (CRM). SCV PA01 and CCY cells were distinguished by their spectral signatures, and the distribution of the overall biomass was monitored by the C-H bending or stretching signal. The distributions of total biomass, PA01, and CCY cells were compared at various times and positions within the biofilm. The distribution of the CCY was very heterogeneous. It was found in the water channels as well as in regions within biofilm colonies. Many of the yeast cells observed within the biofilm colonies under conditions of low or stopped flow were removed when medium was flowing, suggesting that the yeast was not held in the matrix as tightly as were the bacteria.

Effect of whey and soy protein supplementation combined with resistance training in young adults

The purpose was to compare changes in lean tissue mass, strength, and myofibrillar protein catabolism resulting from combining whey protein or soy protein with resistance training. Twenty-seven untrained healthy subjects (18 female, 9 male) age 18 to 35 y were randomly assigned (double blind) to supplement with whey protein (W; 1.2 g/kg body mass whey protein + 0.3 g/kg body mass sucrose power, N = 9: 6 female, 3 male), soy protein (S; 1.2 g/kg body mass soy protein + 0.3 g/kg body mass sucrose powder, N= 9: 6 female, 3 male) or placebo (P; 1.2 g/kg body mass maltodextrine + 0.3 g/kg body mass sucrose powder, N = 9: 6 female, 3 male) for 6 wk. Before and after training, measurements were taken for lean tissue mass (dual energy X-ray absorptiometry), strength (1-RM for bench press and hack squat), and an indicator of myofibrillar protein catabolism (urinary 3-methylhistidine). Results showed that protein supplementation during resistance training, independent of source, increased lean tissue mass and strength over isocaloric placebo and resistance training (P < 0.05). We conclude that young adults who supplement with protein during a structured resistance training program experience minimal beneficial effects in lean tissue mass and strength.

Analysis of creatine, creatinine, creatine-d3 and creatinine-d3 in urine, plasma, and red blood cells by HPLC and GC–MS to follow the fate of ingested creatine-d3

Creatine, which is increasingly being used as an oral supplement, is naturally present in the body. Studies on the fate of a particular dose of creatine require that the creatine be labeled, and for studies in humans the use of a stable isotopic label is desirable. The concentrations of total creatine and total creatinine were determined using HPLC. Creatine and creatinine were then separated using cation exchange chromatography and each fraction was derivatized with trifluoroacetic anhydride and the ratio of the deuterated:undeuterated species determined using GC-MS. Ratios of creatine:creatine-d(3), and creatinine:creatinine-d(3), and the concentrations of each of these species, were able to be determined in urine, plasma and red blood cells. Thus, the uptake of labeled creatine into plasma and red blood cells and its excretion in urine could be followed for a subject who ingested creatine-d(3). Creatine-d(3) was found in the plasma and red blood cells 10 min after ingestion, while creatine-d(3) and creatinine-d(3) were found in the urine collected after the first hour.

A clinical trial of creatine in ALS

BACKGROUND

Mitochondrial dysfunction occurs early in the course of ALS, and the mitochondria may be an important site for therapeutic intervention. Creatine stabilizes the mitochondrial transition pore, and is important in mitochondrial ATP production. In a transgenic mouse model of ALS, administration of creatine prolongs survival and preserves motor function and motor neurons.

METHODS

The authors conducted a randomized double-blind, placebo controlled trial on 104 patients with ALS from 14 sites to evaluate the efficacy of creatine supplementation in ALS. The primary outcome measure was maximum voluntary isometric contraction of eight upper extremity muscles, with secondary outcomes including grip strength, ALS Functional Rating Scale-Revised, and motor unit number estimates. Patients were treated for 6 months, and evaluated monthly.

RESULTS

Creatine was tolerated well, but no benefit of creatine could be demonstrated in any outcome measure. CI analysis showed that the study, although powered to detect a 50% or greater change in rate of decline of muscle strength, actually made an effect size of greater than 23% unlikely. It was also demonstrated that motor unit number estimation was performed with acceptable reproducibility and tolerability, and may be a useful outcome measure in future clinical trials.

CONCLUSION

Any beneficial effect of creatine at 5 g per day in ALS must be small. Other agents should be considered in future studies of therapeutic agents to address mitochondrial dysfunction in ALS. In addition, motor unit number estimation may be a useful outcome measure for future clinical trials in ALS.

Elevation of Creatine in Red Blood Cells in Vegetarians and Nonvegetarians After Creatine Supplementation

The purpose of this study was to examine the effect of a 5-day creatine (CR) supplementation period on red blood cell (RBC) CR uptake in vegetarian and nonvegetarian young women. Blood samples were collected from lacto-ovo vegetarians (VG, n = 6, age 21.8 ± 1.9 yrs) and nonvegetarians (NV, n = 6, age 21.7 ± 1.9 yrs) before and after a 5-day CR loading period (0. 3 g CR/kg lean body mass/day), and from a control group of nonvegetarians (NV, n = 5, age 22.0 ± 0.7 yrs) who did not supplement with creatine. RBC and plasma samples were analyzed for the presence of creatine. Significant increases (p < .05) in RBC and plasma CR levels were found for vegetarians and nonvegetarians following supplementation. The initial RBC CR content was significantly lower (p < .05) in the vegetarian group. There was no significant difference between vegetarians and nonvegetarians in final RBC CR content, suggesting that a ceiling had been reached. As the uptake into both muscle and RBC is moderated by creatine transporter proteins, analysis of the uptake of CR into RBC may reflect the uptake of CR into muscle, offering an alternative to biopsies. Key words: plasma, erythrocyte, loading

Separation methods applicable to urinary creatine and creatinine

Urinary creatinine has been analyzed for many years as an indicator of glomerular filtration rate. More recently, interest in studying the uptake of creatine as a result of creatine supplementation, a practice increasingly common among bodybuilders and athletes, has lead to a need to measure urinary creatine concentrations. Creatine levels are of the same order of magnitude as creatinine levels when subjects have recently ingested creatine, while somewhat elevated urinary creatine concentrations in non-supplementing subjects can be an indication of a degenerative disease of the muscle. Urinary creatine and creatinine can be analyzed by HPLC using a variety of columns. Detection methods include absorption, fluorescence after post-column derivatization, and mass spectrometry, and some methods have been automated. Capillary zone electrophoresis and micellar electrokinetic capillary chromatography have also been used to analyze urinary creatine and creatinine. Creatine and creatinine have also been analyzed in serum and tissue using HPLC and CE, and many of these separations could also be applicable to urinary analysis.

Effect of glutamine supplementation combined with resistance training in young adults

The purpose of this study was to assess the effect of oral glutamine supplementation combined with resistance training in young adults. A group of 31 subjects, aged 18-24 years, were randomly allocated to groups (double blind) to receive either glutamine (0.9 g x kg lean tissue mass(-1) x day(-1); n = 17) or a placebo (0.9 g maltodextrin x kg lean tissue mass(-1) x day(-1); n = 14 during 6 weeks of total body resistance training. Exercises were performed for four to five sets of 6-12 repetitions at intensities ranging from 60% to 90% 1 repetition maximum (1 RM). Before and after training, measurements were taken of 1 RM squat and bench press strength, peak knee extension torque (using an isokinetic dynamometer), lean tissue mass (dual energy X-ray absorptiometry) and muscle protein degradation (urinary 3-methylhistidine by high performance liquid chromatography). Repeated measures ANOVA showed that strength, torque, lean tissue mass and 3-methylhistidine increased with training (P < 0.05), with no significant difference between groups. Both groups increased their 1 RM squat by approximately 30% and 1 RM bench press by approximately 14%. The glutamine group showed increases of 6% for knee extension torque, 2% for lean tissue mass and 41% for urinary levels of 3-methylhistidine. The placebo group increased knee extension torque by 5%, lean tissue mass by 1.7% and 3-methylhistidine by 56%. We conclude that glutamine supplementation during resistance training has no significant effect on muscle performance, body composition or muscle protein degradation in young healthy adults.

The effect of whey protein supplementation with and without creatine monohydrate combined with resistance training on lean tissue mass and muscle strength

Our purpose was to assess muscular adaptations during 6 weeks of resistance training in 36 males randomly assigned to supplementation with whey protein (W; 1.2 g/kg/day), whey protein and creatine monohydrate (WC; 0.1 g/kg/day), or placebo (P; 1.2 g/kg/day maltodextrin). Measures included lean tissue mass by dual energy x-ray absorptiometry, bench press and squat strength (1-repetition maximum), and knee extension/flexion peak torque. Lean tissue mass increased to a greater extent with training in WC compared to the other groups, and in the W compared to the P group (p < .05). Bench press strength increased to a greater extent for WC compared to W and P (p < .05). Knee extension peak torque increased with training for WC and W (p < .05), but not for P. All other measures increased to a similar extent across groups. Continued training without supplementation for an additional 6 weeks resulted in maintenance of strength and lean tissue mass in all groups. Males that supplemented with whey protein while resistance training demonstrated greater improvement in knee extension peak torque and lean tissue mass than males engaged in training alone. Males that supplemented with a combination of whey protein and creatine had greater increases in lean tissue mass and bench press than those who supplemented with only whey protein or placebo. However, not all strength measures were improved with supplementation, since subjects who supplemented with creatine and/or whey protein had similar increases in squat strength and knee flexion peak torque compared to subjects who received placebo.

The effect of 7 days of creatine supplementation on 24-hour urinary creatine excretion

Since the discovery that oral ingestion of creatine leads to an increase in intramuscular creatine, its supplementation has become widespread. However, the dosage necessary to maximize retention and create significant increases in intramuscular creatine is poorly understood. In this study, 24-hour urinary creatine and creatinine levels of 20 university men's football players and 20 university men's hockey players involved in a resistance-exercise program and supplementing with creatine were collected and analyzed. In a double-blind, randomized design, 10 football players and 10 hockey players were randomly assigned to either the supplement or placebo group. Subjects provided a 24-hour urine sample twice during the study: once prior to supplementation (baseline) and the second 7 days after daily supplementation and resistance exercise. Creatine dosage was 0.1 g x kg(-1) lean body mass. The quantity of creatine ingested was compared with the amount excreted in the urine of those subjects supplementing with creatine and with placebo. Creatinine levels were compared between the first and second urine collection and between groups. Creatine and creatinine concentrations were determined using high-performance liquid chromatography. In 24-hours, 46% of the ingested creatine was excreted. There was no change in creatine levels for placebo subjects. Creatinine levels remained the same within groups at the first and second collection times (p < 0.05). Our findings indicate that when supplementing with dosages of 0.1 g x kg(-1) lean body mass or between 6 and 8 g at a time, approximately half of the ingested creatine gets excreted. Because there was no change in urinary creatinine, it can be assumed that enhanced degradation of creatine did not occur.

Interactions of Pyrene-Labeled Silica Particles

Silica spheres were prepared by the Stöber method, and the method of labeling with pyrene, using aminopropylysilane as the linking agent, was optimized. Excimers between particles were formed when high concentrations of label were used. Both surfactant and polyelectrolyte addition were able to cause floc formation when added to suspensions of the silica, but only the surfactant changed the I(1)/I(3) ratio and diminished excimer formation. Copyright 2000 Academic Press.

Analysis of creatine and creatinine in urine by capillary electrophoresis

Creatine is found in the urine of subjects ingesting creatine monohydrate as an ergogenic aid. Creatinine, the catabolic breakdown product of creatine, is a major constituent of normal urine. It is of interest to follow the excretion of creatine and creatinine in urine as a function of time after creatine ingestion. In this study, creatine and creatinine were analyzed in urine by capillary electrophoresis. The optimization of the method was discussed, with the best results being obtained using a 30 mM phosphate-150 mM sodium dodecyl sulfate buffer at pH 6, with the detector set at 214 nm and an applied voltage of 15 kV across a 45 cm capillary. Verification of the method was provided by HPLC analysis and spiking. The application of the method was demonstrated by analysis of creatine and creatinine in urine samples collected in a 24-h period following creatine ingestion.

A capillary electrophoretic determination of the kinetics of tetradecanedisulfate hydrolysis

Capillary electrophoresis was used to follow the decrease in concentration of tetradecanedisulfate as a function of time during its hydrolysis in 0.5 M sulfuric acid solution at 60, 75, and 90°C. The hydrolyses were mostly carried out at premicellar concentrations of surfactant, from 1 to 7.5 mM. Large increases of rate occurred at higher concentrations (at least 15 mM). The reaction was found to be first order in tetradecanedisulfate. The activation energy and entropy of activation were calculated to be 97 kJ mol-1 and -55 J K-1 mol-1, respectively.Key words: capillary electrophoresis, surfactant, acid hydrolysis, tetradecanedisulfate, activation energy, entropy of activation.

Article

Capillary zone electrophoresis (CZE) was used to study the preparation of 1,2-decanedisulfate from 1,2-decanediol and determine the stability of the two-headed surfactant and the corresponding hydroxydecanesulfates under both acidic and basic conditions. The optimum buffer for the CZE determination was found to be diethylbarbiturate. Resolution of the hydroxydecanesulfate constitutional isomers was facilitated by the addition of magnesium ions. Decanedisulfate was stable in base but hydrolyzed in acid. The hydroxysulfates hydrolyzed much more rapidly, and in both acid and base. Mechanisms were postulated based on differential rates of formation and hydrolysis of the hydroxydecanesulfate constitutional isomers.Key words: capillary zone electrophoresis, decanedisulfate, hydroxydecanesulfate, hydrolysis, surfactant.

Fiber optic sensor for Ca2+ based on an induced change in the conformation of the protein calmodulin

A fiber optic sensor that exploits the natural selectivity of the Ca(2+)-binding protein calmodulin (CaM) is described. In this sensor, a dialysis membrane is used to entrap a fluorescein-labeled CaM (F-CaM) solution at the common end of a bifurcated fiber optic bundle. Ca2+ ions in a sample solution can diffuse through the membrane and bind to the F-CaM. Upon binding with Ca2+, CaM undergoes a conformational change that induces a change in the fluorescence of the attached fluorescein tag. This change in fluorescence can be related to the concentration of Ca2+ in the sample solution. The detection limit for the sensor is 5 x 10(-8) M Ca2+. The sensor has no interference by Mg2+ at concentrations as high as 10(-2) M.

A tensammetric study of the adsorption of cationic polymers and copolymers

The tensammograms of several sets of cationic polyacrylamide copolymers are discussed and compared. Tensammograms are not affected by molecular weight, but plots of capacitive current at a chosen potential versus charge density give regular curves. Key words: tensammetry, cationic, polyacrylamide, charge density.

Determination of the charge density of acrylamide/acrylate copolymers by tensammetry

The charge densities of acrylamide/acrylate copolymers can be determined using tensammetry. The tensammograms were run using 20 ppm solutions of polymer in 0.1 M tetraethylammonium chloride. A standard curve of desorption peak height versus mol% anionicity was useful in the range 10–50%. A second standard curve of the potential at which the capacitive current measured 1 μA versus mol% anionicity allowed the determination of charge density in the range 0–15%. Keywords: tensammetry, polyaerylamide, charge density, tetraethylammonium, desortion peaks.

A tensammetric study of polyacrylamides, including their determination

Phase-sensitive tensammetry is shown to be a convenient and useful way to analyse polyacrylamides and associated derivatives (pams) in dilute aqueous solutions. Standard curves were obtained with ranges varying from 9 to 25 ppm and limits of detection varying from 0.7 to 2 ppm. Ways to change the range and sensitivity are discussed and demonstrated. Typical interferences and their effects are tabulated, and the analysis of pams in coal washings is discussed. The analysis of certain mixtures of polyacrylamides is shown to be possible.

Determination of polyacrylamides by maximum suppression

The use of polarographic maximum suppression methods for determining polyacrylamides and polyacrylic acid-based polymers was investigated. Using the oxygen, Co2+, and Hg2+ maxima these polymers were determined at the low ppm level. The effectiveness of polymers as maximum suppressors was dependent on the charge of the polymer and that of the electrode at the potential at which the polarographic wave occurred. The maximum suppression of various binary mixtures of polyacrylamides indicated that in some mixtures suppression was additive while in other mixtures, particularly those containing both anionic and cationic polymers, the suppression was greatly reduced. Aqueous extracts of chosen coals contained various interfering substances which could be removed most efficiently using Sephadex G-75, although this resin was only compatible with anionic and neutral polymers.