Trivalent Chromium Research Articles

Inhibiting Metal Galvanic and Carbon Corrosion in Aluminum Alloy-Carbon Fiber Reinforced Composite Joints by Spontaneous Deposition of Diazonium Adlayers on Exposed Carbon Fibers

The spontaneous formation of a diazonium molecular adlayer on the exposed fibers of a carbon fiber reinforced polymer (CFRP) composite was investigated as a surface treatment. The purpose of the surface treatment is to reduce the extent of galvanic corrosion on a trivalent chromium process (TCP) conversion-coated aluminum alloy when the two materials are mechanically joined as is common in aircraft structures. The adlayer functions to reduce the rate of dissolved oxygen reduction on the more noble carbon thereby reducing the rate of galvanic corrosion on the more active metal alloy. The formation of the adlayer (4-nitrophenyl (NP), 4-nitroazobenzene (NAB), or 2-fluorene diazonium tetrafluoroborate (FL)) was achieved by immersing the CFRP composite specimen in a solution of 5 mM diazonium salt dissolved in acetonitrile for a specified time (1–24 h) under open circuit conditions (so-called spontaneous deposition). Cyclic voltammetry (CFRP composite) and rotating disk voltammetry (glassy carbon) were used to investigate the oxygen reduction reaction kinetics in naturally aerated 0.5 M Na2SO4 (pH 5–6). The oxygen reduction reaction current was suppressed by greater than 90% by the NP and NAB adlayers and 80% by the FL adlayer. The surface treatment (24 h immersion) with NAB significantly reduced the galvanic corrosion damage on TCP conversion-coated aluminum alloy during a 14-day continuous neutral salt spray (NSS) exposure. The mass loss (mg/cm2) and corrosion intensity (g/m2y) were reduced by over 10×. The spontaneously formed NAB adlayers are stable during the salt-spray exposure and provide better inhibition of galvanic corrosion on the aluminum alloy and resistance to carbon corrosion than do NAB adlayers formed by an electrochemically assisted process reported on previously.

Characterization of sweet corncob polysaccharide-chromium (III) complex and its digestion properties and hypoglycemic effect

Sweet corncobs, an agricultural byproduct, undergo limited processing post-harvest. To enhance the utilization of sweet corncobs and amplify their hypoglycemic activity, polysaccharides (SCP) were extracted, purified, and subsequently modified using trivalent chromium ions, resulting in the formation of SCP-Cr(III) with a weight percentage of Cr(III) at 21.99%. The chemical composition and structure of SCP-Cr(III) were analyzed using various techniques, including SEM-EDS, FT-IR, XPS, XRD, AFM, TG, and HPLC. The findings revealed that the binding mode of SCP-Cr(III) involved the formation of Cr–OH and Cr–O bonds with the glycan chains. The major constituents were glucose, galactose, xylose, and arabinose, with molar ratios of 95.66:1.94:0.43:1.31. Furthermore, it was observed that the fundamental structure of SCP-Cr(III) remained unaltered after simulated digestion. In vitro hypoglycemic experiments demonstrated that SCP-Cr(III) exhibited significant inhibitory effects on α-glucosidase and α-amylase, with a mixed pattern predominantly driven by competitive inhibition. These findings suggest that SCP-Cr(III) possesses greater hypoglycemic potential compared to SCP alone. Thus, this study provides a theoretical basis for the application of sweet corncob, an agricultural byproduct from processing, in the development of hypoglycemic functional food products.

Influence of trivalent chromium process (TCP) concentration on the anti-corrosion protection of 2024-T3 aluminium alloy

ABSTRACT In the present work, the surface of 2024-T3 aluminium alloys was coated with different concentrations (25, 35, and 50 wt.%) of the trivalent chromium process (TCP), and they were evaluated by comparing them to hexavalent chromium coatings (HCC). The findings show that TCP coating had a porous surface regardless of the concentration of TCP coating while the HCC exhibited a cracked pattern. The TCP coating increased the surface roughness as well as the wettability compared to HCC. The immersion test in 3.5 wt. % NaCl solution revealed that the open circuit potential (Eocp) of coated samples was more positive than that of the uncoated sample. However, the HCC coating was slightly more anodic after half of the immersion. The potentiodynamic test confirmed the formation of a passive region for all samples. Furthermore, the corrosion potential (Ecorr) and the critical pitting potential (Epit) were more positive for the lowest concentration coating. The polarisation resistance of the samples suggested that the HCC coating was superior to TCP coatings. In general, the low concentration of TCP coating improved the corrosion protection of 2024-T3 but not better than HCC coating due, probably, to the porous surface morphology.

THE ROLE OF SULFUR-CONTAINING AMINO ACIDS IN THE PREVENTIVE NUTRITION OF WORKERS IN CONTACT WITH CHROMIUM

In the world, a large number of workers are exposed to fumes, mists and dusts containing Chromium and its compounds. One of the ways to prevent chromium intoxication is the enrichment of food rations with substances that have antioxidant and complexing ability. Attention is focused on the recommendations on the use of sulfur-containing amino acids and sulfur-rich proteins in the composition of food products for the prevention of intoxication in workers who come into contact with chromium in production. The mechanism of reduction of hexavalent chromium compounds by cysteine was considered. It has been shown that the process of reduction of chromates with cysteine is accompanied by the oxidation of cysteine to cystine and subsequent complexation with trivalent chromium. The structure of chromium III cystinate was confirmed by IR and electron spectroscopy and elemental analysis. It has been established that in the formed chelate complex [Cr(SNO2C3H6)6Cr], chromium (III) has a bond with cystine through the amino and carboxyl groups, LD50 is 2100 mg/kg and is less toxic than inorganic chromium (III) salts. The article analyzes protein raw materials rich in cysteine, which can be recommended to satisfy the daily requirement of cysteine, or to reduce chromium intoxication of workers working in a work area with a high content of chromium salts.

Aggregation-induced emission-based versatile 3D hierarchical porous nanoprobe for electrochemiluminscence-fluorescence dual-mode detection of Cr(VI)

Owing to the built-in cross reference correction function, dual-mode monitoring platform is conducive to perform the highly precise pollution surveillance and traceability analysis in complicated environmental media. Herein, a novel aggregation induced emission (AIE)-based 3D hierarchical porous nanoprobe COP-TPEN2 was successfully synthesized, as to design a electrochemiluminscence (ECL)-fluorescence dual-mode sensing platform for Cr(VI) detection in environmental water samples. Equipped with many -NH groups, COP-TPEN2 can reduce hexavalent chromium Cr(VI) to low-toxicity trivalent chromium Cr(III). Moreover, different valence states of Cr ions were discovered to consume portions of the reactive intermediates of S2O82- (i.e., SO4-), and the electrons during the reduction of COP-TPEN2 were captured due to the strong oxidation property of Cr2O72-, leading to a decrease in the ECL intensity for COP-TPEN2. Moreover, COP-TPEN2 with AIE properties could be applied for Cr(VI) detection in fluorescence channel through the joint action of inner filter effect and static quenching. On account of the different signal generation mechanisms, two independent signals were selectively triggered by Cr(VI), achieving efficient detection of Cr(VI) with LODs of 0.18 nM and 0.29 nM, respectively. This dual-mode sensor was successfully used to determine Cr(VI) in environmental samples with satisfactory results, thereby showing great potential in environmental monitoring.

Smartphone-enabled colorimetric visual quantification of highly hazardous trivalent chromium ions in environmental waters and catalytic reduction of p-nitroaniline by thiol-functionalized gold nanoparticles

High-efficiency sensing systems for extremely hazardous chromium (Cr(III)) ions are important due to their detrimental effects on human health and the environment. We employed a spectrophotometric method combined with a smartphone (red, green, and blue (RGB) color ratio)-based detection platform to realize the quick, visually quantifiable in situ detection of Cr(III) ions using surface plasmon resonance (SPR)-aided colorimetry. For optical sensing nanoprobes, we synthesized the 2-Mercapto-5-methyl-1,3,4-thiadiazole (MMT)-modified gold nanoparticles (MMT-AuNPs) using a wet chemical method. By way of a coordination reaction, the Cr(III) ions induce the as-prepared MMT-AuNPs to aggregate and subsequently change the SPR wavelength band. The freshly synthesized MMT-AuNPs exhibited a wine-red color. While Cr(III) ions interact with the MMT-AuNPs, the color of the latter evolved from wine red to purple, thus facilitating visual monitoring. The SPR-relevant color change allowed the quantitative sensing of Cr(III) ions in the range of 40–128 nM, with the limit of detection of 6.93 nM when employing the spectrophotometric method and 12.4 nM when using the smartphone RGB color ratio. Furthermore, we developed the spectrophotometric technique that used the smartphone RGB color ratio for on-site analysis of Cr(III) ions in environmental water samples, indicating the possibility of its chemo-sensing applications for portable quantitative detection devices. Additionally, the catalytic performance of the MMT-AuNPs was demonstrated by the reduction of p-nitroaniline in the presence of sodium borohydride. It was interestingly unveiled that the MMT-AuNPs showed outstanding catalytic performance with a catalytic rate constant of 6.31 × 10−3 s−1.

A Comprehensive Review of the Impact of Chromium Picolinate on Testicular Steroidogenesis and Antioxidant Balance.

Low testosterone (T) levels are a major cause of male infertility, as this hormone is crucial for several processes throughout the entire male reproductive tract. Leydig cells (LC) produce T through testicular steroidogenesis. Disrupted LC function can hinder steroid production and fertility. Among the factors that affect steroidogenesis, endocrine-disrupting chemicals (EDCs) raise concerns, as they disturb hormonal signaling. Chromium is classified as an EDC, and its main forms are hexavalent (Cr(VI)) and trivalent chromium (Cr(III)). While Cr(III) is controversially regarded as an essential metal, its compound Cr(III) picolinate (CrPic3) is used as a nutritional supplement due to its antidiabetic and antioxidant properties. This review aims to identify the possible effects of CrPic3 on testicular steroidogenesis and thus, on male fertility. The detriments caused by CrPic3 in LC include the inhibition of enzymes involved in steroidogenesis, and, as in other cells, the induction of mutagenesis and apoptosis. Remarkably, CrPic3 impacts male fertility through the alteration of reactive oxygen species (ROS), T levels, and sperm parameters (sperm motility and abnormal sperm count). However, gaps and inconsistencies exist in the literature concerning its effects on male fertility. Thus, further research is imperative to comprehend the underlying mechanisms of CrPic3 in the physiological processes relevant to male fertility, ensuring the supplement's safety for use by men.

Kinetics and Mechanism of Electrochemical Reactions Occurring during the Chromium Electrodeposition from Electrolytes Based on Cr(III) Compounds: A Literature Review

A literature review was conducted to examine the current understanding of the kinetics and mechanism of electrochemical reactions occurring during the electrodeposition of chromium coatings from electrolytes based on trivalent chromium compounds. The research in this scientific field is crucial, as it addresses the pressing need for an alternative to chromium plating processes that rely on solutions containing highly toxic and harmful hexavalent chromium compounds. Numerous literature data on the kinetics and mechanism of the stepwise reduction process of Cr(III) complex ions were analyzed. The influence of various additives and surfactants on the reaction kinetics of the stepwise reduction of trivalent chromium ions was considered. Special attention was given to the kinetics of the stepwise discharge of trivalent chromium ions in ionic liquids and deep eutectic solvents.

The use of calcium peroxide CaO2 for wastewater treatment from chromium (VI)

The at meant of waste water from hexavalent chromium ions with calcium per oxide CaO2 was investigated. This product is obtained from soda ash production waste. Clarified part of still waste suspension (distillation suspension) contains calcium chloride and sodium chloride. The process of producing calcium peroxide is based on the interaction of calcium chloride with solutions of calcium peroxide and sodium hydroxide. A two-step (reagent) method of purification from hexavalent chromium is proposed. The first stage of the reagent method consists in reducing (conversion) toxic hexavalent chromium to a less dangerous trivalent chromium, and the second - in converting trivalent chromium to an insoluble state (into a hydroxide). The conversion (reduction) of Cr6+ to Cr3+ is carried out using calcium peroxide as a reagent. Reductionis carried out in an acidic medium, and to precipitate trivalent chromium in the form of chromium hydroxide (Cr(OH)3) waste water is neutralized using neutralizer Ca(OH)2. This method of wastewater treatment from hexavalent chromium can be effective in small and medium production, especially in the absence of general treatment facilities.

Cr(VI) removal and mechanism from simulated polluted groundwater by Klebsiella variicola H12-CMC-FeS@biochar assisted permeable reactive barrier

Permeable reactive barrier(PRB) is an attractive technique for in situ polluted groundwater remediation. Klebsiella variicola H12-Carboxymethylcellulose -FeS@biochar (K.variicola H12-CMC-FeS@biochar) was used as filling medium in PRB to remove chromium contamination from simulated groundwater. The results showed that the chromium removal efficiency was 94 %, which was more effective than k. variicola H12 or biochar respectively and the optimal solid-liquid ratio was 30:1. Ionic strength and initial chromium concentration in groundwater have greater influence on the treatment effect. Scanning electron microscopy(SEM) and fluorescence microscopy showed that biofilm covered on the surface of the material. X-ray Photoelectron Spectroscopy(XPS) indicated that most of hexavalent chromium(Cr(VI)) and trivalent chromium(Cr(III)) were adsorbed by k. variicola H12-CMC-FeS@biochar. Cr(III) originated from the reduction of chromium by K. variicola. Furthermore, quantitative real-time polymerase chain reaction(qPCR) results showed that the expression level of ChrA, ChrB and ChrR genes increased, which contributed to relieve cytotoxicity. These changes improved the resistance of k. variicola H12 to Cr(VI), promoting Cr(VI) reduction. In summary, biofilm adsorption and microbe reduction were the two primary ways to enhance the chromium removal efficiency. It provided a new method for treating in-situ groundwater pollution by PRB technology using biochemical materials as mediums.

Self-regulated S-scheme heterojunction for synergistic removal of tetracycline and hexavalent chromium: Synergistic mechanism of trivalent chromium

The limitation of conventional photocatalysts in simultaneously removing Tetracycline (TC), hexavalent chromium (Cr (VI)) and trivalent chromium (Cr (III)) were addressed in mixed pollution treatment. The S-scheme heterojunction of titanate nanotubes/Bi2WO6 (TNTs/BWO) was successfully constructed to achieve efficient removal of TC, Cr (VI), and Cr (III). The theoretical calculations (DFT) demonstrated that TNTs’ ion exchange properties led to the partial replacement of interlayer Na+ by Cr (III), optimizing the S-scheme heterojunction during the photocatalytic reaction. Experimental results revealed that the coexistence of TC, Cr (VI), and Cr (III) had a mutual promotion effect, as evidenced by the apparent rate constant of Cr (VI) reaching 0.7 min−1, which was 87.5 times higher than that of the single pollutant system, while maintaining a high apparent rate constant for TC. The likely intermediate products, degradation pathways, and photocatalytic mechanism were also elucidated using DFT molecular orbitals and Fukui index analysis. This work provides new insights and strategies for simultaneously removing pollutants and contributes to wastewater purification.

Damage Mechanism of Trivalent Chromium Coatings under Tensile Stress

Due to new environmental regulations, hexavalent chromium electrolytes can no longer be used for thick, hard chromium plating. In response to this industrial and environmental challenge, trivalent chromium electrolyte plating has been developed. In this paper, we propose a study of the adhesion of CrIII coatings based on the implementation of numerical models in comparison with an identified experimental scenario. The aim is to dissociate the influence of coating and substrate behaviours from the adhesion work by describing the intrinsic damage of the chromium layer and the coating–substrate interface. Two types of cracking were studied: transverse cracking and delamination. For the former, the crack density was higher for CrIII than for CrVI and increased with deformation and coating thickness. Microtensile tests with scanning electron microscopy (SEM) observations allowed us to highlight the cracking process in the coating (transverse cracking) and at the coating–substrate interface (delamination). The numerical simulation of the test allowed us to estimate a damage-initiation threshold normal stress of 1900 MPa, which occurred at an average applied strain of 2.5%. Delamination of the coating was complete at an average strain of 13.6% and an interfacial normal stress of 2600 MPa.

Insights into the proton-enhanced mechanism of hexavalent chromium removal by amine polymers in strong acid wastewater: Reduction of hexavalent chromium and sequestration of trivalent chromium

Adsorption is a green technology of treating heavy metal-contaminated strong acid wastewaters for the recycling of heavy metal and reuse of strong acid. Herein, three amine polymers (APs) with different alkalinities and electron donating abilities were prepared to investigate the adsorption-reduction processes of Cr(VI). It was found that the removal of Cr(VI) was controlled by the concentration of –NRH+ on the surface of APs at pH > 2, which relies on the alkalinity of APs. However, the high concentration of NRH+ significantly facilitated the adsorption of Cr(VI) on the surface of APs and accelerated the mass transfer between Cr(VI) and APs at strong acid environment (pH ≤ 2). More importantly, the reduction of Cr(VI) was enhanced at pH ≤ 2, due to the high reduction potential of Cr(VI) (E ≥ 0.437). The ratio of reduction to adsorption (α) of Cr(VI) was above 0.70, and the proportion of Cr(III) bonding on Ph-AP excessed 67.6 %. Finally, a proton-enhanced mechanism of Cr(VI) removal was verified by analyzing FTIR and XPS spectra as well as constructing DFT model. This study provides a theoretical basis for the removal of Cr(VI) in the strong acid wastewater.

Characterization and corrosion behavior of Ni-Cr coatings by using pulse current electrodeposition

PurposeThe purpose of this paper is to study the effect of chromium content on the microstructure and corrosion resistance of Ni-Cr coating.Design/methodology/approachNi-Cr coating was prepared by pulse current electrodeposition with trivalent chromium. On the basis of studying effect of electroplating parameters on composition and morphology, Ni-Cr alloy coatings with various chromium contents were obtained. The microstructure was characterized by scanning electron microscopy, X-ray diffractometer and transmission electron microscopy. Corrosion behavior was studied by potentiodynamic polarization and electrochemical impedance spectroscopy techniques.FindingsElectrodeposited chromium was solidly dissolved in nickel and refined the grain of the coating. With the increase of Cr content, the corrosion resistance of Ni-Cr coating was enhanced, which is due to the formation of continuous nickel hydroxide and compact chromium oxide passive films.Originality/valueNi-Cr alloy coating without penetration crack was prepared in trivalent chromium electrolyte, and the mechanism of its excellent corrosion resistance was proposed.

Broadband near infrared luminescent properties of Cr3+ activated SrGa2Si2O8 phosphor

There has been a lot of interest in trivalent chromium ion-doped phosphors for near-infrared (NIR) luminescence in recent years. Here, trivalent chromium-doped NIR emitting SrGa2Si2O8 phosphors were synthesized. The electronic structure was calculated via density functional theory. Although only [SrO7], [SiO4], and [GaO4] polyhedra were found in the host, we still observe broadband luminescence of Cr3+ in the region of 650–950 nm from octahedra site. Due to the doping of Cr3+, a transformation from [GaO4] tetrahedron rearrange into [CrO6] octahedron was produced. The experimental results of X-ray photoelectron spectroscopy and electron paramagnetic resonance spectroscopy demonstrated the presence of Cr3+. A systematic study of the photoluminescence properties of SrGa2Si2O8:Cr3+ was conducted. The luminescent intensity of SrGa2Si2O8:0.005Cr3+ at 420 K can be retained at 83.42% compared to 300 K, indicating its high thermal stability. The electroluminescence of the prepared light emitting diode (LED) based on SrGa2Si2O8:Cr3+ and blue LED chip was measured under various currents. The application as a NIR LED light source was demonstrated in human hands.

Unexpected associations of long-term and excessive exposure to trivalent chromium with hypertension and glycosuria in male tannery workers

Serious health hazards including renal, skin and hearing disorders have been reported in Bangladeshi tannery workers (TWs) who were chronically exposed to a large amount of trivalent chromium [Cr(III)]. However, the effects of Cr(III) exposure on the prevalence of hypertension and the prevalence of glycosuria in TWs remain unknown. Since the Cr level in toenails is an established marker reflecting long-term exposure to Cr(III) in humans, the associations of Cr levels in toenails with the prevalence of hypertension and the prevalence of glycosuria in male tannery and non-tannery office workers (non-TWs) in Bangladesh were investigated in this study. The mean toenail Cr level in non-TWs (0.5 μg/g, n = 49) was comparable to that in the general population reported previously. Mean Cr levels in TWs with a low toenail Cr level (5.7 μg/g, n = 39) and those with a high toenail Cr level (298.8 μg/g, n = 61) were >10-fold and >500-fold higher, respectively, than that in non-TWs. Our univariate and multivariate analyses indicated that the prevalence of hypertension and the prevalence of glycosuria in TWs with a high toenail Cr level, but not in TWs with a low toenail Cr level, were significantly lower than those in non-TWs. This study showed for the first time that long-term and excessive exposure to Cr(III) that is more than >500-fold but not >10-fold higher than the usual exposure level could decrease the prevalence of hypertension and the prevalence of glycosuria in TWs. Thus, this study revealed unexpected effects of exposure to Cr(III) on health.

Evaluation and Assessment of Trivalent and Hexavalent Chromium on Avena sativa and Soil Enzymes.

Chromium (Cr) can exist in several oxidation states, but the two most stable forms-Cr(III) and Cr(VI)-have completely different biochemical characteristics. The aim of the present study was to evaluate how soil contamination with Cr(III) and Cr(VI) in the presence of Na2EDTA affects Avena sativa L. biomass; assess the remediation capacity of Avena sativa L. based on its tolerance index, translocation factor, and chromium accumulation; and investigate how these chromium species affect the soil enzyme activity and physicochemical properties of soil. This study consisted of a pot experiment divided into two groups: non-amended and amended with Na2EDTA. The Cr(III)- and Cr(VI)-contaminated soil samples were prepared in doses of 0, 5, 10, 20, and 40 mg Cr kg-1 d.m. soil. The negative effect of chromium manifested as a decreased biomass of Avena sativa L. (aboveground parts and roots). Cr(VI) proved to be more toxic than Cr(III). The tolerance indices (TI) showed that Avena sativa L. tolerates Cr(III) contamination better than Cr(VI) contamination. The translocation values for Cr(III) were much lower than for Cr(VI). Avena sativa L. proved to be of little use for the phytoextraction of chromium from soil. Dehydrogenases were the enzymes which were the most sensitive to soil contamination with Cr(III) and Cr(VI). Conversely, the catalase level was observed to be the least sensitive. Na2EDTA exacerbated the negative effects of Cr(III) and Cr(VI) on the growth and development of Avena sativa L. and soil enzyme activity.

Rapid photocatalytic reduction of hexavalent chromium over Z-scheme MgIn2S4/BiPO4 heterojunction: Performance, DFT calculation and mechanism insight

The accumulation of highly fluid and biotoxic hexavalent chromium (Cr(VI)) impairs water ecosystems. It is urgent to quickly reduce Cr (VI) to trivalent chromium (Cr (III)) in wastewater. Hereby, Z-scheme MgIn2S4/BiPO4 heterojunction was prepared, and MB-30 (mass ratio of BiPO4 to composite) presented a rapid Cr(VI) (10 mg L−1) removal efficiency of 100% within 10 min, its kinetic rate constant was 9.0 and 30.1 folds that of MgIn2S4 and BiPO4, respectively. After four rounds, MB-30 maintained a high removal rate of 93.18% and stabilized crystal texture. First-principles calculations revealed that the formation of Z-scheme heterojunction could ameliorate charge generation, detachment, migration capability, and light utilization. Meanwhile, the coupling of S and O in the two components produced a tight S–O bond, which acted as an atomic-level access to promote carrier migration. The findings were consistent with the structure superiority and optical and electronic properties of MB-30. The Z-scheme pattern was substantiated based on multifarious experiments, which exhibited an elevated reduction potential while emphasizing the significance of interfacial chemical bond and the internal electric field (IEF) on carrier detachment and migration.

Inhibition of Surface Corrosion Behavior of Zinc-Iron Alloy by Silicate Passivation

The passivation of zinc alloy coating was achieved through the utilization of both silicate and trivalent chromium passivation systems, employing a specific process formula consisting of Co(NO3)2 at a concentration of 2.5 g/L, C76H52O46 at 3 mL/L, Na2SiO3 at 25 g/L, C6H5Na3O7 at 15 g/L, and an appropriate amount of organic accelerator. The composite passivation of silicate and tannic acid was found to be more effective than the trivalent chromium passivation film, as it successfully eliminated the dendrite structure on the coating surface and reduced surface defects. The coordination between negatively charged SiO2− or SiO2 micelles and Zn2+ results in the formation of a passivation film that exhibits lower corrosion current and higher corrosion potential compared to the trivalent chromium passivation film. Additionally, the impedance test fitting results indicate that the silicate passivation film possesses a higher resistance value. Overall, the proposed silicate passivation system presents a viable alternative to the toxic chromate passivation system, offering non-toxicity and superior protective performance relative to the trivalent chromium passivation system.

Separation, speciation and quantification of both chromium (VI) and chromium (III) in tanned leather samples: a comparative study and validation of analytical methods

In the present work, a comparative study of analytical methods for the simultaneous and quantitative determination of trivalent and hexavalent chromium is presented. For the analysis by ion chromatography-inductively coupled plasma-mass spectrometry, two different columns were tested, as well as different mobile phases and different pH of the samples. The optimized analytical method permitted the separation of Cr(III) and Cr(VI) using 75 mmol/L NH4NO3 pH 3 as chromatographic eluent. The method was validated and applied to real samples, allowing the determination of both species simultaneously, even when there is a huge difference of concentration between Cr(III) and Cr(VI). Limit of detection and limit of quantification for Cr(III) were found to be 0.016 and 0.054 upmug/L (0.3 and 1.1 upmug/kg), respectively, and for Cr(VI) 0.13 and 0.43 upmug/L (7 and 22 upmug/kg), respectively. Possible species interconversions were monitored through the use of chromium isotopic standards, which confirmed that the optimized methodology preserves chromium speciation during extraction and analysis. Fourier-transform ion cyclotron resonance-mass spectrometry permitted the structure elucidation of the complex formed during ethylenediaminetetraacetic acid extraction.Graphical