• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.25 no.1
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• pp.89-94
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• 2015

Objectives: The objective of this study was to determine characteristics of workers' exposures to airborne total and hexavalent chromium by job title in electroplating processes. Methods: Total Cr was determined through a modified method based on NIOSH Method 7024. Airborne hexavalent Cr, Cr(VI), was sampled and extracted according to NIOSH Method 7600 and analyzed at 520 nm using an ion chromatograph/visible detector. Results: The geometric mean(GM) of total Cr concentrations from all factories was $11.2{\mu}g/m^3$(GSD=4.9). The GM of Cr(VI) concentrations from all factories was $2.84{\mu}g/m$ (GSD=5.2), and the concentrations among factories were significantly different (p<0.05). The Cr(VI) levels were lower than total Cr levels. Total Cr exposure levels were highest among buffing workers ($21.6{\mu}g/m^3$), but Cr(VI) levels were highest among plating workers($4.15{\mu}g/m^3$). The concentrations of Cr(VI) and total Cr from plating tasks was highly correlated(r=0.91). Conclusions: In the electroplating industry, plating workers were mainly exposed to Cr(VI), but others were not. Oxidation-reduction states of Cr and job titles should be considered in the exposure or risk assessments of chrome electroplating factories.

• Preventive Nutrition and Food Science
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• v.9 no.4
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• pp.342-345
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• 2004

This study evaluated the effects of different forms of chromium supplements on serum glucose, insulin and lipid concentrations in rats. Sprague-Dawley male rats were randomly assigned to one of three dietary groups and fed AIN-76 semi-purified basal diets supplemented with 300 ppb Cr from Cr methionine (CrMet) and Cr chloride $(CrCI_3)$ or without Cr (control). By the end of the $4^{th}$ week, all rats were decapitated, blood collected, and serum glucose, insulin and lipid concentrations were determined. The CrMet and $CrCl_3$ supplementation did not affect weight gain and feed efficiency ratio. However, feed intake was significantly higher in CrMet groups than control (p < 0.05). CrMet-supplemented rats had markedly increased insulin levels (p < 0.05) compared with controls. Serum lipids were not significantly different between the control and the CrMet groups. $CrCl_3$ supplementation decreased total cholesterol and triglyceride, but the decreases were only significant for the control group. $CrCl_3$ supplementation was associated with significant decreases in total cholesterol compared with CrMet supplementation. These results indicate that CrMet supplementation is effective for increasing serum insulin, and $CrCl_32$ may improve lipid concentrations, because we observed decreased serum total cholesterol and an improved total cholesterol/HDL-cholesterol ratio (THR).

• Journal of the Korean Society of Food Science and Nutrition
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• v.32 no.5
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• pp.706-709
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• 2003

Chromium (Cr) plays an important role in body composition. Several human and animal studies of Cr supplementation have reported increases in lean body mass, often with concurrent decreases in body fat. The purpose of the current study was to determine the effects of supplemental Cr as chromium methionine (CrMet) on obesity index, body fat and serum lipids in rats. Thirty-six male Sprague-Dawley rats were divided into four groups of nine rats. Rats received a AIN-76 semipetrified basal diet or high fat diet supplemented with 300 ppb CrCl$_3$and CrMet as well as no added dietary Cr (referred to as Control, HF, HFCr, and HFCrMet). After 6 weeks on the respective diets, animals were killed and analyzed for differences in serum lipid concentrations. Rats supplemented with CrMet had a slightly higher naso-anal length and final body weight was decreased. The lowest obesity index and body fat content were found in CrMet supplemented animals (p〈0,05). Supplemental CrMet decreased the total lipid, triglyceride and total cholesterol. The significant differences observed were total cholesterol concentration for CrMet supplementation. These indicate that supplemental Cr, as chromium methionine, resulted in a significant decrease of obesity index and body fat and influence serum lipid concentrations, possibly by decreasing the body fat.

• Journal of Nutrition and Health
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• v.35 no.8
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• pp.834-839
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• 2002

This study aimed to investigate the effects of chromium picolinatec (CrP) supplementation on the glucose and lipid metabolism of rats. Five-week-old male Sprague-Dawley rats were fed a high-fat diet fir 110 days and further treated with CrP or placebos for 6 weeks. The effect of CrP supplementation on body weight, blood glucose, insulin and lipid levels was examined. The results suggested that body weight gain was not significantly different between the control and the CrP supplemented group. Plasma glucose, triglyceride and cholesterol levels in the CrP treated group significantly decreased compared to those of the control group (p < 0.05). The total lipid, triglyceride and cholesterol concentrations in the livers of the CrP treated group significantly decreased compared to those of the control group (p < 0.05). These results indicate that supplementation of chromium picolinate ran reduce triglyceride and glucose concentrations in the blood and total lipid and total cholesterol levels in the liver.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.8 no.2
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• pp.209-223
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• 1998

The aim of this study was to evaluate welders' exposure to hexavalent chromium (Cr(VI)) and nickel (Ni) during welding operations in a Korean shipyard. The airborne Cr(VI) and Ni concentrations were measured during metal inert gas (MIG) welding on mild and stainless steel, and manual metal arc (MMA) welding on mild steel. The geometric mean (GM) of Cr(VI) concentrations inside the welding helmet during MIG welding on mild steel were $0.0018mg/m^3$ inside a ship section, and $0.0015-0.0026mg/m^3$ at the welding shops. All of the personal breathing zone air samples were below the American Conference of Governmental Industrial Hygienists (ACGIH) Threshold Limit Value ($TLV^{(R)}$) of $0.01mg/m^3$. Conversely, eighty-eight percent(21 of 24) of the personal breathing zone air samples exceeded the National Institute for Occupational Safety and Health (NIOSH) recommended exposure limit of $0.001mg/m^3$. Ni was not detected on 20 of 23 air samples collected during MIG welding on mild steel. The three Ni samples above the limit of detection ranged from 0.015 to $0.044mg/m^3$. The GM of Cr(VI) concentrations during MMA welding on mild steel were $0.0013mg/m^3$, but Ni was not detected in the air samples during this operation. It is assumed that the airborne Cr(VI) and Ni during mild steel welding were derived from the base metals which contained about 0.03% Cr and 0.03% Ni. The GM of airborne total Cr, Cr(VI) and Ni concentrations during MIG welding on stainless steel were 4.02, 0.13 and $0.86mg/m^3$, respectively, and the levels of Cr(VI) and Ni were above the ACGIH-$TLV^{(R)}$. Cr(VI) comprised about 35.5% of the total chromium(Cr) from MIG welding on mild steel, and about 8.4% of total Cr from MIG welding on stainless steel. The ratios of Cr(VI) to total Cr were significantly different among welding shops. It was concluded that welders were exposed to high levels of Cr(VI) and Ni during welding on stainless steel, and were exposed to low levels of Cr(VI) even during welding on mild steel.

• Tribology and Lubricants
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• v.38 no.4
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• pp.162-169
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• 2022

Cobalt-chromium (CoCr)-based alloys have been used for wear applications because of their excellent mechanical properties and wear resistance. With growing concern over environmental problems, CoCr alloys are expected to be used for various tribological applications in degraded lubrication states. To expand the applicability of the materials, data should be accumulated across a broad spectrum of experimental parameters. In this work, the friction and wear characteristics of cobalt-chromium-tungsten (CoCrW) and cobalt-chromium-molybdenum (CoCrMo) alloys are investigated experimentally. The tests are conducted using a pin-on-reciprocating-plate tribotester in dry lubrication. CoCrW and CoCrMo are used as pin and plate materials to investigate the effect of the counter material. The results show that the friction coefficients between CoCrW and CoCrMo generally range from 0.4 to 0.5. The friction coefficient between the CoCrW pin and plate is found to be slightly small. However, the total wear between the CoCrW pin and plate is found to be the largest. In contrast, the total wear between the CoCrW pin and plate is relatively small. Furthermore, CoCrW may cause a faster wear progression of CoCrMo, especially for the case in which CoCrMo is used as the pin material. The results of this work provide a better understanding of the tribological properties of CoCrW and CoCrMo alloys. In addition, this work provides a practical guideline for the use of CoCrW and CoCrMo from the tribological design viewpoint.

• Korean Journal of Materials Research
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• v.9 no.4
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• pp.341-344
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• 1999

We reported compositional separation(CS) into Co-enriched and Cri-enriched components inside the grains of Co-Cr based thin films prepared by rf sputtering. CS strongly depends on the sputtering conditions of substrate temperature and target composition. Tuning the microstructure of the Co-Cr films is important in order to employ the CS for high-density magnetic recording. We investigated the origin of CS from thermodynamic viewpoint. We employ a spinodal decomposition-like model to describe the origin of the CS in Co-Cr films. We consider the total free energy of the Co-Cr films as the sum of several free energies of; 1) thermodynamic mixing entropy of a binary solid solution, 2) magnetic ordering interaction(MOI) energy below the Curie temperature, and 3) excess interaction energy(XS) caused by the sputtering process as a function of temperature and composition. Those energies distorted the total free energy like the spinodal decomposition and caused the compositionally separated fine microstructure inside the grains. If the second derivative of the total free energy with respect to Cr composition becomes negative at a given substrate temperature, we may observe a metastable compositional separation inside the Co-Cr alloy films. We expect to exploit the microstructure of CS for ultra-high density magnetic recording.

• Asian-Australasian Journal of Animal Sciences
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• v.26 no.11
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• pp.1609-1613
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• 2013

An experiment was conducted to determine the apparent total tract digestibility (ATTD) and standardized total tract digestibility (STTD) of phosphorus (P) in copra expellers (CE), palm kernel expellers (PKE), and cassava root (CR). Eight barrows (initial BW of 40.0 kg, SD = 4.5) were individually housed in metabolism crates. A replicated $4{\times}3$ incomplete Latin square design was employed involving 4 dietary treatments, 3 periods, and 8 animals. Three experimental diets contained 40% CE, PKE or CR as the only source of P. A P-free diet mainly based on corn starch, sucrose, and gelatin was also prepared to estimate the basal endogenous loss of P. The marker-to-marker method was used for fecal collection. Values for the ATTD of P in the CE and PKE were greater than in the CR (46.0 and 39.7 vs -14.0%; p<0.05). However, the STTD of P did not differ greatly among the test ingredients (56.5, 49.0, and 43.2% in the CE, PKE, and CR, respectively). In conclusion, the ATTD of P values in CE and PKE were greater than that in CR, but the STTD of P did not differ greatly among CE, PKE, and CR.

• Korean Chemical Engineering Research
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• v.44 no.6
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• pp.644-649
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• 2006

In this paper, the Cr(VI) adsorption behaviors of activated carbons (ACs) treated by various ozone treatment conditions were studied. The surface properties of the ACs studied were determined by pH, acid-base, and FT-IR measurements. $N_2$ adsorption isotherm characteristics at 77K were confirmed by BET equation, Boer's t-plot method, and Horvath-Kawazoe's slit pore model. Also, the total Cr adsorption amount onto the ACs was measured by ICP-AES. As a result, the ozone treatment led to an increase of oxygen-containing polar functional groups and total acidity as well. Meanwhile, the specific surface areas or micropore volumes were slightly decreased after the ozone treatment due to the micropore filling or blocking. Nevertheless, the total Cr adsorption of ACs was increased with increasing of the ozone treatment time, attributed to the good interaction between Cr ions and polar functional groups on the ACs.

• Bulletin of the Korean Chemical Society
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• v.30 no.6
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• pp.1252-1256
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• 2009

A simple, selective and sensitive fluorescence quenching method was developed to the determination Cr(VI). The method is based on the oxidation of $I^-\;to\;{{I_3}^-}$ by Cr(VI) in sulfuric acid solution followed by immediate formation of ion association compound between I3 − and rhodamine 6G in Tween-80 micellar media at room temperature. The influence of several surfactants on rhodamine 6G fluorescence signal was studied; particular attention was paid in the aggregation behavior of rhodamine 6G–Tween-80 system. The experimental parameters (e.g., type of surfactant, reagent concentration) were studied and the optimal conditions were established. The linear calibration graph was obtained in the range 2.0 - 100.0 ng m$L^{-1}$ Cr(VI). The detection limit of the method was 0.37 ng m$L^{-1}$. The relative standard deviation (R.S.D.) is less than 5% (n = 5). The efficiency of the method for the determination of Cr(VI) in the presence of Cr(III) in the sample was investigated. The method was applied successfully to the determination of Cr(VI) and total Cr in water, and liver tissue samples.