Article

Liquid digesta markers: A method for synthesis of crystallized chromium-EDTA and comparison of its degree of complexation with an uncrystallized preparation

Authors:
To read the full-text of this research, you can request a copy directly from the authors.

Abstract

Markers of liquid digesta are an essential tool for determination of in vivo nutrient digestibility and passage as they move with and mark passage of the liquid fraction through the gut. Such markers are ideally biologically and chemically unreactive so they do not affect the digesta or animal. Two issues encountered with the liquid marker chromium (III)(Cr)ethylenediaminetetraacetic acid (EDTA; Cr-EDTA): 1)the Cr acetate·monohydrate required for preparation of the crystallized lithium salt of Cr-EDTA (Li·Cr-EDTA; Udén method; J. Sci. Food Agric. 31, 1980, 625–632)has become largely unavailable, and 2)as an ionic salt, the degree of complexation of Cr and EDTA in solution of an uncrystallized preparation of Cr-EDTA has not been evaluated. Accordingly, the objectives of this study were to develop a method for preparing Li·Cr-EDTA using Cr (III)acetate hydroxide, and to compare the degree to which Cr is complexed with EDTA in solutions made with crystallized Li·Cr-EDTA and in preparations in which Cr-EDTA is not crystallized for purification (Binnerts method; Vet. Rec. 82, 1968. 470). The new Li·Cr-EDTA preparation method which uses Cr acetate hydroxide gave product yields of 901 to 870 g actual/kg theoretical which was similar to the 900 g actual/kg theoretical yield reported for the original Udén method. The Cr concentrations were 928–961 g actual/kg theoretical for the salt. Solutions of both the crystallized preparation of Li·Cr-EDTA and the liquid preparation of the Binnerts method gave visibly similar absorbance patterns at wavelengths from 300 to 750 nm and showed maximum light absorption at 541 nm, the reported wavelength of maximum absorption for Cr-EDTA. Comparison of absorbances at 541 nm to a Li·Cr-EDTA generated standard curve showed that uncrystallized Cr-EDTA produced with the Binnerts method gave a recovery of Cr in Cr-EDTA of approximately 993 g/kg, which did not differ from the 992 g/kg value for preparations of Li·Cr-EDTA; this indicates that Cr and EDTA for both preparation methods were almost completely complexed in solution. In conclusion, the new method for preparing Li·Cr-EDTA gave results comparable to the Udén method, and Cr and EDTA were ionically bound to a high degree and comparably in both the uncrystallized solution of the Binnerts method and solutions of crystallized Li·Cr-EDTA. Verification of the degree of Cr and EDTA complexation in Binnerts preparations can be accomplished with spectrophotometric comparison against a purified standard such as Li·Cr-EDTA.

No full-text available

Request Full-text Paper PDF

To read the full-text of this research,
you can request a copy directly from the authors.

... Researchers have used several external markers to trace both the fluid and particulate phases of digesta in the ruminant GIT (see Table 1 for definitions used henceforth). There is no ideal marker, but Cr, lanthanides (rare earths), and soluble complexes of Cr and Co have been used in studies regarding digestion kinetics (Ellis and Huston, 1968;Hartnell and Satter, 1979;Udén et al., 1980;Ellis et al., 2002Ellis et al., , 2005Hall and Van Soest, 2019). In ruminants, fecal excretion profiles of such external markers are characterized by a time delay followed by a sharp increase in the concentration of the marker in the feces that peaks within few hours after dosing, and then by a smooth decrease asymptotically to zero (Uden et al., 1982). ...
Article
We used the information-theoretic (I–T) approach to evaluate the quality of fit of nonlinear mixed-effects models fitted to fecal profiles of the particulate markers Cr and La, and Co-EDTA as a fluid marker pulse dosed to cattle and sheep. Experiments with dry and lactating dairy cows, steers, and sheep fed tropical forages including corn silage ad libitum or at multiples of maintenance were the sources of the fecal marker profiles. We fit nonlinear compartmental models of one (GN), two (GNG1), or multiple compartments (MC) to those markers by animal species/category. The animal was the random effect introduced in the nonlinear mixed-effects model. Variance and correlation functions accounted for heterogeneity of variance. The model averaging technique was necessary to summarize inferences from the fit of the several compartmental models according to the I–T approach. Some models presented an overall excellent fit, with model probabilities ≥0.9. This probability threshold leaves a low level of uncertainty for choosing such models to represent reality, given the data, and for those fits, there was no need for model averaging. For many profiles, however, there was a need for model averaging to improve predictive accuracy. The Cr-fiber and Co-EDTA travelled at different transit times (τ) in steers; however, the confidence intervals for τ overlapped for dry, lactating cows, and sheep. Chromium-labeled forage particles remained within retention segments during overlapping residence times for steers, sheep and dry cows, whereas Cr-labelled forage fiber and La-labelled concentrate fiber segregate with respect to residence times for sheep. The liquid phase Co-EDTA marker for lactating cows had the shortest residence times if compared to other markers fed to dry cows, steers, and sheep. The total mean residence times of Cr-labelled particles were shorter for lactating cows, intermediate for dry cows and sheep, and were longer for steers. The I–T approach was useful for selecting models within the nonlinear mixed models' framework, by combining the ability of different models to fit marker excretion profiles, and by combining the predictive powers of the fitted models by averaging solutions whenever necessary.
... The lithium salt of CrEDTA was prepared using Cr (III) acetate hydroxide (Hall and Van Soest, 2019), and that of CoEDTA prepared according to the method of Udén et al. (1980). Solutions of CrEDTA (0.206 g/100 mL with water) and CoEDTA (0.185 g/100 mL of MES buffer; MES) were prepared. ...
Article
An ideal digesta marker for use in feeding studies is inert, unabsorbable, and moves with the portion of the digesta it is intended to mark. Both chromium (III) and cobalt (III) salts of EDTA (CrEDTA and CoEDTA, respectively) have been used as digesta liquid markers in studies with dairy cattle. Although a small portion of these markers is known to be absorbed and excreted in urine, the markers are assumed to remain ionically bound in the digesta. The degree to which these salts remain bound in solution can be determined through spectrophotometric measurement at the wavelength (λ) of peak absorbance of these colored compounds. The objective of this study was to evaluate whether CrEDTA and CoEDTA dissociate during incubation in autoclaved, clarified rumen fluid (ACRF), as indicated by changes in absorbance. In a complete block design with separate replicated analytical runs, approximately 40 mg/L of Cr from CrEDTA or Co from CoEDTA were incubated in 2 separate preparations of ACRF from 2 lactating Holstein cows, in water (CrEDTA), or in MES buffer (CoEDTA), and appropriate reagent blanks. Solution pH were approximately 6.0. Samples were incubated for 24 h at 39°C with absorbance measurements recorded at 0, 1, 2, 4, 6, 22, and 24. The CrEDTA was measured at λ = 541 nm, CoEDTA at λ = 535 nm, and both were measured with wavescans of λ = 330 to 700 nm. At their peak λ, both CrEDTA in water and CoEDTA in MES buffer maintained absorbance values throughout the incubation, whereas, in ACRF, CrEDTA absorbance decreased by 9% at 0 h, and by up to 14% by 24 h; CoEDTA showed a gradual decline over time, with approximately 4% loss in absorbance by 24 h. Responses differed by ACRF preparation. Both markers in ACRF showed increases and decreases over time in absorbance at λ = 330 and 380 nm, though the changes were more marked for CrEDTA; markers not in ACRF showed no change in absorbance at these λ. Changes in the absorbance values at λ = 330 and 380 nm suggest that soluble phenolic compounds may be involved in the exchange of metals with EDTA, but that does not preclude involvement of other components in rumen fluid. Both CrEDTA and CoEDTA incubated in ACRF showed declines over time in absorbance at their peak λ, suggesting that the metals dissociated from EDTA. The apparent dissociation indicates that these liquid markers are not inert as had been assumed.
Article
Concentration of volatile fatty acid (VFA) provides an imprecise view of VFA dynamics due to the confounding effects of fluid pool size and dynamics. Determination of VFA flux using isotope is expensive and a complex methodology. Therefore, a rapid and affordable approach to explore VFA dynamics may allow comprehensive characterization of VFA availability. The objective of this study was to explore the use of VFA dynamics generated by meal feeding to derive time-series rates of VFA apparent appearance and disappearance driven by different protein and fiber sources. Six ruminally cannulated wethers were fed diets containing timothy hay or beet pulp (TH, BP) and soybean meal (SBM) or heated soybean meal (HSBM). Diets were, TH + HSBM; TH + SBM; BP + HSBM; and BP + SBM and the experimental design was a partially replicated 4 × 4 Latin Square. Concentrations of VFA and polyethylene glycol (PEG) in rumen fluid samples were estimated. Concentrations of PEG were used to estimate fluid passage and volume to calculate VFA mass, and fluid-mediated exit. Maximum apparent appearance rate (mmol/h), the rate of apparent appearance decline (mmol/mmol/h), mean apparent appearance flux (mmol/h), mean apparent disappearance (mmol/h) and apparent disappearance rate (mmol/mmol/h) were estimated by deriving a 1 pool model for each VFA on a mass basis where appearance was assumed to follow an exponential decay pattern and disappearance followed mass action kinetics. Statistical analyses were conducted using a linear mixed effect regression with fixed effects for fiber source, protein source, and their interaction, as well as random effects for animal and period. Rumen fluid volume (L) was greater in HSBM diets (P = 0.033) and fluid passage (%/h) was greater in SBM diets (P = 0.048). Concentrations (higher acetate and butyrate, P = 0.002 and 0.004, respectively) and molar proportions (higher valerate, P = 0.035) of VFA were affected only by fiber source; however, protein source and fiber source interacted to significantly influence apparent appearance rates and absorption rates of many major VFA. On a flux basis, HSBM supported significantly elevated mean disappearance of propionate (P = 0.033). This data demonstrate that time-series evaluation of fermentation dynamics, including fluid dynamics and VFA concentrations can be used to estimate apparent appearance and disappearance of VFA. Although further work is needed to confirm the alignment of these estimates with measurements of VFA supplies to the animal, this modelling approach may provide a simpler way to better understand the kinetics of rumen.
Article
Full-text available
Increasing ruminal starch digestibility has the potential to improve microbial protein synthesis (MPS), milk production, and feed efficiency. Enogen corn (Syngenta Seeds LLC) expresses high α-amylase activity, and we evaluated effects of Enogen corn silage (CS) and grain (CG) on ruminal starch digestibility, MPS, and milk production in lactating dairy cows. Fifteen Holstein cows (6 ruminally cannulated and 9 noncannulated; average ± standard deviation at the beginning of the trial: 170 ± 40 d in milk; milk yield, 37.2 ± 7.73 kg/d; body weight, 714 ± 37 kg) were used in a replicated 3 × 3 Latin square design (28 d per period) with 3 treatments: a diet containing isoline CS and CG (control, CON); a diet with Enogen CS and isoline CG (ECS); and a diet with Enogen CS and CG (ECSCG). Dry matter (DM; 30%), starch (35% of DM), and particle size distribution of the isoline and Enogen CS were similar. However, the mean particle size of Enogen CG was larger (1.05 vs. 0.65 mm) than that of the isoline CG. Cannulated cows were used for digestibility and nutrient flow measurements, noncannulated cows were used for enteric CH4 measurements, and all cows were used for production evaluation. Dry matter intake (DMI) and milk yield were greater for ECS and ECSCG compared with CON (26.7 and 26.6 vs. 25.1 kg/d and 36.5 and 34.1 vs. 33.1 kg/d, respectively) without a difference between ECS and ECSCG. Milk protein yield was greater (1.27 vs. 1.14 and 1.17 kg/d) for ECS compared with CON and ECSCG. Milk fat content was greater (3.79 vs. 3.32%) for ECSCG compared with ECS. Milk fat yield and energy-corrected milk did not differ among treatments. Ruminal digestibilities of DM, organic matter, starch, and neutral detergent fiber were not different among treatments. However, ruminal digestibility of nonammonia, nonmicrobial N was greater (85 vs. 75%) for ECS compared with ECSCG. Total-tract apparent starch digestibility was lower (97.6 and 97.1 vs. 98.3%) for ECS and ECSCG compared with CON, respectively, and tended to be lower (97.1 vs. 98.3%) for ECSCG compared with ECS. Ruminal outflows of bacterial OM and nonammonia N tended to be greater for ECS than for ECSCG. Efficiency of MPS tended to be greater (34.1 vs. 30.6 g of N/kg of organic matter truly digested) for ECS versus ECSCG. Ruminal pH and total and individual short-chain fatty acid concentrations did not differ among treatments. Concentration of ruminal NH3 for ECS and ECSCG was lower (10.4 and 12.4 vs. 13.4 mmol/L, respectively) compared with CON. Methane per unit of DMI decreased for ECS and ECSCG compared with CON (11.4 and 12.2 vs. 13.5 g/kg of DMI, respectively) without a difference between ECS and ECSCG. In conclusion, ECS and ECSCG did not increase ruminal or total-tract starch digestibility. However, the positive effects of ECS and ECSCG on milk protein yield, milk yield, and CH4 per unit of DMI may show potential benefits of feeding Enogen corn. Effects of ECSCG were not apparent when compared with ECS, partly due to larger particle size of Enogen CG compared with its isoline counterpart.
Article
EDTA-complexed heavy metals (EDTA-CHMs), one of the typical contaminants in industrial effluents, present challenges for wastewater purification because of their stability and high solubility over a wide pH range. Selective adsorption of various EDTA-CHMs coexisting in industrial wastewater is crucial for the recovery of heavy metal resources. Hence, investigating the competitive behavior and selective adsorption mechanisms of coexisting EDTA-CHMs during the effluent removal process is worthwhile. In this study, we chose Ferrihydrite (Fh) as the adsorbent and focused on the competitive adsorption behavior of two common EDTA-CHMs (EDTA-Cu(Ⅱ) and EDTA-Cr(Ⅲ)) on the Fh surface, as well as their removal mechanisms. For binary systems (EDTA-Cu(Ⅱ) and EDTA-Cr(Ⅲ)), the maximum adsorption capacity of Fh for EDTA-Cu(Ⅱ) was 17.32 mg/g, but because of the coexisting EDTA-Cu(Ⅱ), adsorption of EDTA-Cr(Ⅲ) by Fh was severely inhibited. In a competition experiment with binary contaminants of different EDTA complexes, Fh consistently exhibited stronger adsorption performance on EDTA-Cu(Ⅱ) when the ratio and addition order of EDTA-Cu(Ⅱ) and EDTA-Cr(Ⅲ) in the coexisting system was changed, and the valence state of the EDTA-CHMs was the key factor. The adsorption mechanism indicated that Fh could directly adsorb EDTA-CHMs through electrostatic interaction and surface complexation. The recycling rate of EDTA-Cu(Ⅱ) was still approximately 70.63% after five cycles of treatment with Na2SO4 solution. This study provides new insights into the adsorption behavior of coexisting EDTA-CHMs on adsorbents and the selective removal of related pollutants.
Article
Industrial wastewater containing organic ligands and heavy metals is considered a serious public health threat, and its treatment and purification have become challenging tasks. Moreover, the organic-chelated heavy metals formed by common organic ligands and free heavy metals can cause many problems and concerns because of their poor biodegradability, high solubility, and extreme stability. In this study, aluminum-containing ferrihydrite (Fh-Al) adsorbents of different composition molar ratios were prepared and utilized to remove typical EDTA-Cr(III) in an aqueous system, and the associated removal mechanism was examined. The experimental results show that adding Al not only enhances the removal rate of EDTA-Cr(III) by the Fh-Al adsorbent in a wide pH range (pH = 3–9) but also increases the maximum adsorption capacity of EDTA-Cr(III). In addition, the specific surface area of Fh-Al can be increased by adding aluminum with different molar ratios, thus promoting its adsorption performance for EDTA-Cr(III). Furthermore, surface complexation and electrostatic attraction were proposed as possible mechanisms of EDTA-Cr(III) adsorption by Fh-Al. This study shows that Fh-Al-6 adsorbent can adsorb common EDTA-chelated heavy metals (such as EDTA-Pb, EDTA-Cr, EDTA-Cu and EDTA-Cd) in one step, with maximum adsorption capacities of 41.47, 32.33, 16.51 and 31.27 mg/g at pH = 3. The Fh-Al-6 adsorbent can be reused after being regenerated in a 2 g/L Na2SO4 solution. This study provides new expectations for treating wastewater containing organic groups and heavy metals.
Article
Purification of various types of industrial wastewater containing chelated heavy metals (CHMs) remains a challenging task due to the easy dissolution, poor biodegradation and extremely high stability over a wide pH range. Compared with the common CHMs, the attention of Cr(III) complexes is greatly insufficient. Especially, Cr(III) of the wastewater is easily reoxidized and converted into Cr(VI) with high biotoxicity during the transferring process, so the treatment of Cr(III) complexes needs to be treated more strictly. Obviously, compared with previous advanced oxidation and replacement-coprecipitation technologies, adsorption method could directly remove Cr(III) complexes in one step, thus avoiding the accumulation of secondary toxic Cr(VI). Considering that ferrihydrite (Fh) materials are widely distributed on the nature, excellent adsorption performance, low cost, and environmentally friendly, this paper proposes a novel strategy that uses the common Fh as an efficient adsorbent to realize one-step elimination of typical EDTA-Cr(III) complexes without introducing secondary pollution. Batch experiment results illustrated that more than 93% of EDTA-Cr(III) was removed at pH=3 or 6 (a final concentration of < 1 mg/L EDTA-Cr(III) was detected in the residual solution within one hour). In particular, Fh retained good performance for the removal of EDTA-Cr(III) after desorption reactions in 2 g/L Na2SO4 solution. A series of experiments and characterization results suggested that EDTA-Cr(III) was adsorbed on Fh materials mainly through electrostatic interactions and surface complexation. In general, this study also demonstrated Fh for the outstanding remediation of various Cr(III)-organic complexes from multicomponent environment.
Article
Ideal digesta markers used for feeding studies are inert, unabsorbable, and move with the digesta they are intended to mark. Both chromium (III) and cobalt (III) salts of EDTA (CrEDTA and CoEDTA, respectively) are used as markers of liquid digesta in dairy cattle research. A small portion is absorbed and excreted in urine, but the markers are assumed to remain unreactive and as inert salts in the digesta and animal. The degree to which these colored salts remain bound in solution can be estimated through spectrophotometric measurement at their wavelength (λ) of peak absorbance. The objective of this in vitro study was to evaluate whether CrEDTA and CoEDTA dissociate under reducing conditions that could be experienced in the rumen. In a completely randomized design with 2 replicate analytical runs and samples in duplicate within run, approximately 26 mg/L Cr from CrEDTA or Co from CoEDTA was incubated in a 26-mL reaction volume containing 20 mL of Goering and Van Soest medium without tryptone, 3 mL of CoEDTA or CrEDTA solutions, or water (reagent blanks), and 3.0 mL of a combination of distilled water with 0, 0.25, 0.50, 0.75, or 1.00 mL of reducing solution (RedSol). After incubation for 0.5 h at 39°C, absorbance was read at λ = 535, 465, and 560 nm, the peak λ for EDTA salts of Co(III), Co(II), and Cr(III), respectively. Mean reagent blank values were subtracted from CoEDTA and CrEDTA data. The absorbance data at peak λ were analyzed by marker in models that included RedSol with analytical run as a random variable. Contrasts were used to detect linear through quartic effects of RedSol. Samples with RedSol had redox potentials of -250 to -328 mV, which are within the range of reported ruminal measures. As RedSol increased, CoEDTA showed a linear decline of 75% in ABS at 535 nm and a quadratic 4-fold increase followed by a 60% decline at 465 nm. These responses indicate a reduction of Co(III) to Co(II) and subsequent dissociation of Co(II)EDTA. The absorbance of CrEDTA at 560 nm showed a tendency for an 8% linear decrease as RedSol increased. Wavescans from λ = 330 to 700 nm showed CrEDTA retaining its characteristic 2-peak pattern as RedSol increased, whereas CoEDTA curves deformed entirely. We conclude that CoEDTA is not a stable, inert digesta marker under reducing conditions achievable in the rumen and is therefore unsuitable for use in studies with ruminants. Reexamination of the suitability of available liquid digesta markers is advised.
Article
Full-text available
Widely cited and accepted explanation of reaction mechanism of the case study reaction of chemical kinetics between Cr(III) ions and ethylenediaminetetraacetic acid (EDTA) contradicts modern chromium(III) coordination chemistry data. Absorption UV and visible light spectra were recorded during the reaction between aqueous solution of Cr(NO3)3 and EDTA in order to obtain new information about this reaction. Analysis of the spectra showed that only very small fraction of intermediates may be present in solution during the course of the reaction. The reaction scheme was established and according to it calculations based on a simplified model were carried out. Literature data for constants were used if known, otherwise, adjusted values of their sound estimates were applied. Reasonable agreement of the model calculations with the experimental data was obtained for pH values 3.8 and 4.5 but the model failed to reproduce measured rate of reaction at pH 5.5, probably due to the use of the oversimplified model.
Article
Full-text available
Four lactating Friesian cows with permanent cannulas in the rumen and proximal duodenum were given early (EC)- or late (LC)-cut grass silage ad lib., each with either 3 or 9 kg concentrate dry matter (DM)/d in a 4 x 4 Latin square design starting about 10 weeks after calving. Feed was offered twice daily at 08.30 hours and 15.30 hours. Periods lasted 5 weeks and measurements were made in the last 15 d. The higher amount of concentrates increased total DM intake but reduced silage DM intake and the fractional rate of degradation of silage-fibre DM. Later cutting date of silage had no effect on DM intake or the fractional rate of degradation of silage-fibre DM but reduced potential degradability of silage fibre. Dilution rate of CoEDTA in rumen fluid was greater during the day (eating period) than during the night (resting period). Dilution rates measured at the duodenum were lower than those measured in the rumen, but neither was affected by diet. Silage-particle passage rates were measured by use of ytterbium-labelled silage fibre (Yb-fibre) and chromium-mordanted faecal particles (Cr-faeces) and samples were taken at the duodenum and in the faeces. Values for slower rate constant (k1) and transit time were higher and for faster rate constant (k2) were lower for Yb-fibre than for Cr-faeces, but differences in total mean retention time were inconsistent. Values for k1 for both markers and k2 for Yb-fibre only were similar at both sampling sites, but values for k2 for Cr-faeces were lower in the faeces. No diet effects were established with Yb-fibre but, with Cr-faeces, k1 was reduced by more concentrates and EC-silage. Daily mean weights of wet digesta, liquid, neutral-detergent fibre (NDF) and indigestible NDF in the rumen were greater with LC-silage but were unaffected by the amount of concentrates whereas weight of rumen DM was increased by the amount of concentrates only. Maximum rumen fill occurred at 18.00 hours with all diets. Particle-size distribution of rumen contents did not vary markedly during the day. Mean particle size was generally greater with LC-silage than EC-silage. Very small particles, passing through the 0.3 mm screen, constituted about half the rumen DM. It is concluded that rumen fill could have limited intake of LC-silage but not EC-silage.(ABSTRACT TRUNCATED AT 400 WORDS)
Article
Full-text available
Four ruminally and duodenally cannulated multiparous Finnish Ayrshire cows were fed on diets consisting of grass silage (0.6 kg/kg DM) and one of four concentrates: barley, barley + urea, barley + rapeseed meal and barley + rapeseed cake. The objective of the present study was to compare omasal canal and duodenal digesta flows. Values for digesta flow into the omasal canal and duodenum were determined using a triple-marker method based on Co-EDTA, Yb-acetate and indigestible neutral-detergent fibre (NDF) markers. Microbial non-NH3 N (NAN) flow was assessed by purine flow. Microbial samples to determine the bacterial purine:N ratio were harvested from the rumen, omasum and duodenum. Organic matter flow was significantly lower into the omasum than the duodenum, indicating an endogenous organic matter secretion into the abomasum. In contrast, NDF and acid-detergent fibre flows were significantly higher into the omasum indicating digestion of fibre in the omasum. Microbial NAN flows were significantly different (P < 0.001) when estimates were based on bacterial samples harvested from different sites. Differences in total NAN, microbial NAN and dietary NAN flows entering the omasal canal and duodenum were non-significant. The results indicated that the omasal sampling technique provides a promising alternative to the duodenal sampling technique to investigate forestomach digestion in dairy cows and offers an alternative means to study rumen N metabolism.
Article
Full-text available
Ruminal administration of a triple indigestible marker system comprised of cobalt EDTA (CoEDTA), ytterbium acetate (YbAc), and chromium-mordanted straw (CrS) decreases product:substrate ratios for Delta9-desaturase in bovine milk fat. This experiment was designed to identify the marker(s) responsible and develop an alternative system for simultaneous determination of nutrient flow in the gastro-intestinal tract and milk fatty acid composition. Five lactating dairy cows were used in a 5 x 5 Latin square with 21-d periods to evaluate the effects of YbAc, CoEDTA, and CrS independently or as part of a triple marker system (TMS), and CrEDTA as an alternative to CoEDTA on milk fat composition. Markers were administered in the rumen over a 7-d interval and samples of milk were collected on d -1, 3, 7, and 11. Both TMS and CoEDTA alone reduced the concentrations of milk fatty acids containing a cis-9 double bond, whereas YbAc, CrS, and CrEDTA had no effect. Reductions in product:substrate ratios for Delta9-desaturase were time dependent and evident within 3 d of administration. Ruminal infusion of CoEDTA for 7 d induced mean decreases in milk cis-9 14:1/14:0, cis-9 16:1/16:0, cis-9 18:1/18:0, and cis-9, trans-11 conjugated linoleic acid/trans-11 18:1 concentration ratios of 47.7, 26.7, 40.3, and 42.6%, respectively. In conclusion, ruminal infusion of CoEDTA alters milk fatty acid composition and appears to inhibit Delta9-desaturase activity in the bovine mammary gland. Results indicate that a TMS based on CrEDTA, YbAc, and indigestible neutral detergent fiber can be used for estimating nutrient flow without altering milk fat composition in lactating cows.
Article
Chromium(III)-phosphate reactions are expected to be important in managing high-level radioactive wastes stored in tanks at many DOE sites. Extensive studies on the solubility of amorphous Cr(III) solids in a wide range of pH (2.8–14) and phosphate concentrations (10−4 to 1.0 m) at room temperature (22±2)°C were carried out to obtain reliable thermodynamic data for important Cr(III)-phosphate reactions. A combination of techniques (XRD, XANES, EXAFS, Raman spectroscopy, total chemical composition, and thermodynamic analyses of solubility data) was used to characterize solid and aqueous species. Contrary to the data recently reported in the literature,(1) only a limited number of aqueous species [Cr(OH)3H2PO−4, Cr(OH)3(H2PO4)2−2), and Cr(OH)3HPO2−4] with up to about four orders of magnitude lower values for the formation constants of these species are required to explain Cr(III)-phosphate reactions in a wide range of pH and phosphate concentrations. The log K o values of reactions involving these species [Cr(OH)3(aq)+H 2PO −4⇌Cr(OH)3H 2PO −4; Cr(OH)3(aq)+2H 2PO −4⇌Cr(OH)3(H 2PO 4)2−2; Cr(OH)3(aq)+HPO 2−4⇌Cr(OH)3HPO 2−4] were found to be 2.78±0.3, 3.48±0.3, and 1.97±0.3, respectively.
Article
The absorption spectra of both the violet and the blue forms of the ethylenediaminetetraacetic acid complex with chromium(III) ion and the dependence of these forms on the hydrogen ion concentration are reported. It was found that the formation of the complex involves several slow steps. The rate of the first slow step in the formation of the violet compound was followed spectrophotometrically and is first order with respect to chromium and inversely proportional to the hydrogen ion concentration. The entropy and heat of activation for this first step are calculated from the data on temperature dependence.
Article
Deuteron NMR spectroscopy has been shown to be a valuable method for the structural characterization of simple Cr(III) complexes in solution. In order to explore the potential of this technique in more complex systems, [Cr(edta)]- and [Cr(medtra)(H2O)] have been investigated, where 2H is selectively substituted for 1H on the methylene carbons of the acetate arms. The 2H NMR spectrum of the Cr(III)-edta complex is pH independent between pH 3.5 and pH 6.5. In this pH range edta forms a sexidentate complex with Cr(III), a structure that is not currently widely accepted. At pHs outside this range significant changes occur in the spectra. At high and low pHs the spectrum of the complex is similar to that of the quinquedentate [Cr(medtra)(H2O)] complex. The 2H NMR spectrum of [Cr(medtra)(H2O)] shows only minor changes with variations in pH.
Article
Critical values at the 95% confidence level for the two-tailed Q test, and related tests based upon subrange ratios, for the statistical rejection of outlying data have been Interpolated by applying cubic regression analysis to the values originally published by Dixon. Corrections to errors In Dixon's original tables are also Included. The resultant values are judged to be accurate to within ±0.002 and corroborate the fact that corresponding critical values published in recent statistical treatises for analytical chemists are erroneous. It Is recommended that the newly generated 95% critical values be adopted by analytical chemists as the general standard for the rejection of outlier values.
Article
A new liquid marker, cobalt-ethylenediamine tetraacetic acid (EDTA), and two solid markers, chromium (Cr) and cerium (Ce) mordanted plant cell walls, were investigated. Synthesis and methods of analysis are described for the markers. The Cr- and Ce-cell wall complexes were tested for stability to EDTA, hydrochloric acid and rumen microorganisms. Plant cell walls were rendered indigestible by mordanting with Cr and 98% of the marker remained on the fibre after a simulated sequence (in vitro) of digestion. Ce-mordanted cell walls were 35% digestible in vitro using a rumen culture, and 56% of the marker could be washed off the remaining fibre. Treatment with EDTA removed all Ce and 15% of the Cr. Hydrochloric acid (0.01M) had a negligible effect on the removal of Cr from the cell walls, whereas 0.1M acid removed, on average, 10% of the marker. Losses of Cr from the mordant may be related to the quality of the preparation. Co-EDTA was found to be comparable to Cr-EDTA. The urinary excretion of Cr and Co was 2–3% in most animals except in rabbits, which excreted as much as 30% of the liquid markers in the urine.
Formation of the chromium-EDTA complex
  • Hedrick