Carbon Black Adsorbents Research Articles

Simultaneous Determination of Five Organotins in Tropical Fruits Using Modified QuEChERS Combined with Ultra-high Performance Liquid Chromatography-Tandem Mass Spectrometry.

A sensitive, confirmatory ultra-high performance liquid chromatography-tandem mass spectrometry based on modified QuEChERS was developed and validated to detect five organotin compounds (tributyltin chloride (TBT), triphenyltin chloride (TPT), trimethyltin chloride (TMT), azocyclotin and cyhexatin) in classical tropical fruits (mango, pineapple and banana). Fruits samples were ultrasonically extracted with methanol and subsequently purified by graphitized carbon black adsorbents. Five organotins were separated on a C18 column with the mobile phase of a mixture of methanol and 0.1% (v/v) aqueous formic acid, and detected by MS/MS under multiple reaction monitoring mode. The developed method was validated in terms of linearity, limit of detection (LOD), recovery and precision. Results were linear in their corresponding concentration ranges, with coefficients of determination (r) bigger than 0.999. The average LODs (S/N = 3) of the method for TBT, TPT, TMT, azocyclotin and cyhexatin were 1.3, 3.5, 3.2, 5.1 and 1.7 μg/kg, respectively. The average recoveries (n = 5) at three spiked levels (0.01, 0.1 and 0.2 mg/kg) ranged from 69 to 103% with relative standard deviations of 2.1-11.9%. The method is simple, effective, accurate and non-derivatized, and meets the routine monitoring requirements for trace organotins in tropical fruits.

PH swing adsorption process for ambient carbon dioxide capture using activated carbon black adsorbents and immobilized carbonic anhydrase biocatalysts

Adsorbent-based carbon capture is only feasible if adsorption-desorption cycles are both fully regenerating and efficient. This work proposes a regenerative pH swing process and a pH swing regenerative adsorbent that are inspired by natural CO2 conversion by carbonic anhydrase biocatalysts found in mammalian red blood cells. The main objective is to develop, test and analyze a synthetic pH Swing Adsorption (pHSA) system as well as a pHSA compatible solid adsorbent to capture CO2 from a simulated ambient air gas stream. The lead developed adsorbent is a carbon black co-activated with potassium carbonate and nitrogenous copolymer that is impregnated with immobilized bovine carbonic anhydrase and thereby deemed “BCA/KN-CB”. BCA/KN-CB has preliminarily demonstrated both competitive CO2 adsorption capacity and limited regenerative ability under experimental pHSA conditions. In addition, BCA-based adsorbents achieved higher adsorption capacities than non-BCA adsorbent counterparts. The BCA/KN-CB adsorbent displayed both large point of zero charge (PZC) swings and regenerative stability. The proposed pHSA system requires essentially zero energy expenditure to achieve intended environments for capture and regeneration. With 1 kg of adsorbent, pHSA has the ability to capture 1 kg CO2 in less than 4 h of cycling. The tested pHSA adsorbent can also capture more than 96% of total CO2 in a given raw gas stream flowing through the capture chamber. This proof-of-concept study of a pH swing adsorption/biocatalytic adsorbent system suggests the potential to effectively operate under ambient conditions and exhibit advantageous operational efficiencies to other high-profile CO2 capture systems.

Detection of Glyamifop residues in rice and its environment by the QuEChERS method combined with HPLC–MS

Glyamifop is a new herbicide developed by Jiangsu Zhongqi Technology Co., Ltd. (Nanjing, China). No analytical method has previously been reported for determining its residual concentrations in rice and its related environmental samples. This work established a method for the determination of Glyamifop residues in various matrices using high-performance liquid chromatography–tandem mass spectrometry (HPLC–MS) with sample pretreatment by the optimized quick, easy, cheap, effective, rugged, and safe (QuEChERS) method. All samples were extracted with acetonitrile and purified with octadecyl bonded silica gel, N-propylethylenediamine, and graphitized carbon black adsorbents. Chromatographic separation was performed on an Agilen ZORBAX Eclipse XDB-C18 column, and Glyamifop in the samples was detected by electrospray ionization mass spectrometry in positive ion mode. Results demonstrated this method has good linearity for Glyamifop assessment in all matrices over a wide concentration range (0.01–1 mg L−1), with a coefficient of determination >0.99. At levels of 0.01, 0.1, and 0.5 mg kg−1, the mean recoveries of Glyamifop in various matrices varied between 84.15% and 105.76%, with relative standard deviations of 1.3%–9.8%. The detection and quantification limits of this method in each matrix are 1.3–3.6 μg kg−1 and 4.89–12.48 μg kg−1, respectively. All matrices had a moderate matrix effect (between −21.63% and 14.21%), which could be calibrated using respective matrix standard curves. The proposed method is simple and sensitive, and appears suitable for the determination of Glyamifop residues in rice and its environment.

Simultaneous determination of sibutramine and its derivatives in weight loss dietary supplements by LC-MS/MS

The liquid chromatography tandem mass spectrometry method (LC-MS/MS) was used to determine the content of sibutramine (SB), N-desmethyl sibutramine (DSB) and N-didesmethyl sibutramine (DDSB) illegaly mixed in weight loss dietary supplements. Sibutramine and its derivatives were extracted by methanol; impurities in the extract were removed by graphitized carbon black (GCB) adsorbent. The chromatographic separation of analytes took place on C18 column (100 mm x 2.1 mm, 3.5 µm) with a gradient mobile phase of acetonitrile and 2 mM ammonium acetate in 0.1% formic acid solution. Multiple reaction monitoring (MRM) in the positive mode was used to detect and quantify SB, DSB and DDSB at m/z 279.9/124.8; 266.0/124.8 and 252.1/125.0, respectively. The method was validated following the AOAC requirements for specificity, repeatability and recovery. Calibration curves lineared from 0.002 to 0.1 µg/mL for SB, DSB and DDSB. The method was successfully applied to determine the content of SB, DSB and DDSB in weight loss dietary supplements that were randomly collected from phamacies in Hanoi of three formulations of hard capsule, soft capsule and teabag. The results shown that six samples had SB and DSB with the content in the range of 0.817 - 31.7 mg/g.

Efficient Removal of the Toxic Lead Ions from ContaminatedSandy Soils using Newly Engineered Carbon Black Nanoadsorbent

Soils contaminated with heavy metals can embarrass a fatal risk to the environment and human life via the direct uptake of the heavy metal-contaminated agricultural crops. Hence, the treatment of metal-contaminated soils is attracting a lot of research activities to reduce the negative impact on the environment. In the current study, I have activated the surface of the carbon black (CB) adsorbent by introducing functional groups capable to efficiently capture the lead (Pb) metal ions from a Pb-contaminated sandy soil. The soil properties (e.g. electrical conductivity, acidity, carbon and nitrogen content, and organic matter) were studied before and after the treatment with the CB adsorbent. I also showed a comprehensive adsorption study in soil-batch extraction experiments, evaluating a series of factors such as the effects of soil pH (pH 3.0 to pH 7.0), Pb concentration into the soil (5-100 mg/L), and the soil temperature (15-50 °C).Furthermore, the recyclability of the adsorbent was highlighted to evaluate adsorption efficiency upon use. The results of the study were remarkable where a 100 % removal efficiency of Pb ions was obtained using only a 40 ppm of the oxidized CB compared to a 60% removal efficiency when using a pristine CB at the same concentration. The adsorption capacity of Pb ions was as high as 100 mg/g at 30 mg/L of oxidized CB adsorbent. The life cycle of oxidized CB adsorbent was also remarkable compared to that of pristine adsorbent. The recyclability data of the functionalized CB has showed an easy regeneration process with an efficient reusefor 5 cycles with 30 %a performance decline of 30 % only from the initial adsorption efficiency

Determination of 105 pesticide residues in vegetables by QuEChERS-liquid chromatography-tandem mass spectrometry

After optimization of the QuEChERS pretreatment method, combined with liquid chromatography-tandem mass spectrometry (LC-MS/MS) technology, a multi-residue determination method was established for 105 typical insecticides, bactericides, herbicides, and plant growth regulators in vegetables. The target compounds were extracted by acetonitrile, purified with 150 mg primary secondary amine (PSA), 150 mg EC-C18, and 30 mg graphitized carbon black (GCB) adsorbents. The standard curves of 105 target compounds were linear in the concentration range of 0.010-0.200 mg/L, with correlation coefficients (r)>0.99. The limit of quantification was 0.010 mg/kg, the recoveries were between 68.2% and 108% at three spiked levels, and the RSDs of the method were between 1.02% and 11.8%. The method is suitable for the rapid determination of the common pesticides in vegetables owing to its advantages of rapidity, simplicity, and better purification.

An efficient cleanup method coupled with gas chromatography and mass spectrometry for multi-pesticides residue analysis in complex plant matrices.

We aimed to develop an efficient cleanup method for multi-pesticides residue analysis in complex plant matrices, shallot, ginger, garlic, onion, leek, and celery. Column chromatography was used as the cleanup method and fabricated with florisil and graphitized carbon black as the adsorbents. The amount of the graphitized carbon black adsorbent and the choice of the elution solvent were systematically investigated for exploring the best combination. The target pesticides covered organochlorine, pyrethroid, and organophosphorus pesticides, and were 38 in total. The method validation and comparison were performed to verify its feasibility and advantages in operation convenience and purification efficiency. The method limit of quantitation varied from 0.01 to 0.03mg/kg, which depends on the pesticides and the sample matrices. The recoveries of the pesticides ranged from 60.5 to 128% (RSD≤19.0%) at the spiked concentration level of 0.01 (or 0.03) mg/kg and 62.9 to 130% (RSD≤13.0%) at 0.1mg/kg. Compared with the commercial cleanup solid-phase extraction cartridges, the present adsorbent combination displayed better purification effect and shorter sample pretreatment time, demonstrating potential application prospect in the complex matrix sample analysis.

Determination of pesticides in seaweeds by pressurized liquid extraction and programmed temperature vaporization-based large volume injection–gas chromatography–tandem mass spectrometry

A rapid method for the simultaneous identification and quantification of pesticide residues in edible seaweed has been developed. Target analytes were three pyrethroid, a carbamate and two organophosphorus pesticides. The procedure consists of a pressurized liquid extraction (PLE) with integrated clean-up, followed by gas chromatography coupled to tandem mass spectrometry. Five PLE parameters were investigated using a screening design: temperature, static extraction time, number of cycles, percent of flush volume and quantitative composition of the n-hexane/ethyl acetate extraction solvent. The effect of the in-cell clean-up with Florisil ® and graphitized carbon black adsorbents was investigated using a Doehlert response surface design. Large volumes of sample extracts were injected using a programmed-temperature vaporizer (PTV-LVI) to improve both sensitivity and selectivity of measurements. Quantification was carried by the internal standard method with surrogate deuterated standards. The method showed excellent linearity ( R 2 > 0.999) and precision (relative standard deviation, RSD ≤ 8%) for all compounds, with detection limits ranging from 0.3 pg g −1 for chlorpyrifos-ethyl, to 3.0 pg g −1 for carbaryl (23.1 pg g −1 for deltamethrin). Recoveries in real seaweed samples were within the range 82–108%. The method was satisfactory validated for the analysis of wild and cultivated edible seaweeds. The presence of pyrethroid and organophosphorus pesticides in some of the samples was evidenced.

06/01394 Calculating latent frequencies of systems with local damping: Kolonits, F. Nuclear Engineering and Design, 2005, 235, (17–19), 2003–2008

The retention characteristics of 18 ethane-based chlorofluorocarbon, bromochlorofluorocarbon and fluorocarbon fluids have been studied as a function of temperature on a stationary phase consisting of a 5% (mass/mass) coating of a low-molecular-mass polymer of hexafluoropropylene epoxide on a graphitized carbon black adsorbent. Measurements were made at −20, 0, 20 and 40°C for hexafluoroethane (R-116), pentafluoroethane (R-125), 1,1,2,2-tetrafluoroethane (R-134), 1,1,1,2-tetrafluoroethane (R-134a), 1,1,2-trifluoroethane (R-143), 1,1,2-tri-fluoroethane (R-143a), 1,1-difluoroethane (R-152a), and fluoroethane (R161). Measurements were made at 40, 60, 80 and 100°C for 1,2-dichlorotetrafluoroethane (R-114), 1,1-dichlorotetrafluoroethane (R-114a), chloropentafluoroethane (R-115), 2,2-dichloro-1,1,1-trifluoroethane (R-123), 2-chloro-1,1,1- trifluoroethane (R-133a), 1,1-dichloro-1-fluoroethane (R-141b), 1-chloro-1,1-difluoroethane (R-142b), and 1-chloroethane (R-160). Measurements were performed at 60, 80, 100 and 120°C for 1-bromo-2-chlorotetrafluoroethane (R-114B1). Net retention volumes, corrected to a column temperature of 0°C, were calculated from retention time measurements, the logarithms of which were fitted against reciprocal thermodynamic temperature. The relative retentions, also as a function of temperature, were calculated with respect to the retention of tetrafluoromethane and hexafluoroethane. Qualitative features of the data are examined, and trends are identified. In addition, the data were fitted to linear models for the purpose of predicting retention behavior of these compounds to facilitate chromatographic analysis.

Comparative analysis of methods for determination of structural characteristics of carbon adsorbents

Experimental data on the equilibrium adsorption of sulfur hexafluoride, methane, carbon dioxide, and benzene on carbon adsorbents of different porosity obtained in a wide pressure range at 298–408 K were analyzed. The adsorption volumes, surface areas, and sizes of slit-shaped pores of the carbons were determined using several independent methods. A method for determination of the adsorption volume from the experimental isotherm of excessive adsorption of gases and the total content equation was proposed. The resulting values are similar to the adsorption volumes calculated from the data for vapors. A new method for the calculation of the adsorbent surface area is described. The method is based on the dependence of the adsorption volume of adsorbent pores on the effective size of adsorbate molecules. A possibility to determine the average size of narrow slit-shaped carbon pores from the difference of the initial heats of adsorption of the gas under study on the carbon black and porous carbon adsorbent is considered.

Dissolution and demetallation treatment of asphaltene in resid using adsorbent and oil-soluble Mo complex

Dissolution and demetallation behaviors of vacuum residues (Arabian Heavy:AH-VR and Brazilian Marlim: Ma-VR) were investigated using carbon adsorbent and/or an oil-soluble Mo complex (Mo-DTC: Modithiocarbamate) with an aromatic solvent (LCO: Light cycle oil) at variable temperatures of 60–200 °C under the atmospheric pressure. An Arabian-Light atmospheric residue (AR) was also treated under the same conditions without addition of solvent and oil-soluble Mo complexes for the comparison of adsorption behaviors of the asphaltene fraction, in which metallic and heteroatom-containing compounds are concentrated. Heating of VRs up to around 150 °C during the adsorption treatment enhanced the selective adsorption of the polar asphaltene fraction as the irreversibly adsorbed THF-insoluble (THFI) component. The adsorbed amount as THFI fraction was always higher with carbon black adsorbents than with active carbons. Active carbons with relatively high surface area and mesoporous structure were found to be favorable for the selective removal of the polar and heavy asphaltene. Addition of 20–40% LCO (light cycle oil) solvent was also effective for the selective adsorption of the heavy asphaltene of THFI fraction with the less amount as low as 1 wt%, being the similar level to the adsorbed amount with AR. It is noted that heating of VRs and solvent addition to VRs may keep the viscosity of the VR solution to the same level of AR, facilitating the selective adsorption of the polar and heavy component in the asphaltene. A small amount of Mo-DTC (0.1–0.5 wt% based on VR) decreased the amount of HI-THFS fraction in AH-VR from 17.7 to 14.9 and 13.1 with 0.3 and 0.5% addition, respectively. It is revealed that some portions of aggregated asphaltene may be liberated through the interactions with carbon adsorbent of meso-porous surface and/or oil-soluble Mo complex with the aid of aromatic solvent.

LIQUID CHROMATOGRAPHY TANDEM MASS SPECTROMETRY APPLIED TO THE ANALYSIS OF NATURAL AND SYNTHETIC STEROIDS IN ENVIRONMENTAL WATERS

A multiresidue analytical method for the determination of the most common and biologically active natural and synthetic steroids (four estrogens: estriol, 17β-estradiol, 17α-ethynylestradiol, estrone; one progestagen: progesterone and six androgens: trenbolone, boldenone, nandrolone, testosterone, 17α-methyltestosterone, stanozolol) in environmental waters was developed. The analytes were isolated from water samples by solid phase extraction (SPE) utilizing a graphitized carbon black adsorbent (Carbograph-1). The final samples were analyzed by reversed-phase high performance liquid chromatography with tandem mass spectrometry using atmospheric pressure chemical ionization (LC-APCI-MS-MS). Ionization was performed in a heated nebulizer (HN) interface operating in the positive ion mode. The protonated ions [M+H]+ and the dehydrated ions [M+H-H2O]+ (for estriol, 17α-estradiol, 17β-estradiol, and 17α-ethynylestradiol) were used as precursor ion for collision-induced dissociation (CID), and two diagnostic product ions for each analyte were identified for the unambiguous steroid confirmation by multiple reaction monitoring (MRM) mode. Method performance, for this analytical procedure, was validated by analyzing groundwater and river water samples fortified at level of 20 ng/L. The average recovery for each analyte exceeded 82%. Good method precision was demonstrated with percent relative standard deviation of less than 7.2% for all analytes.

Novel family of multi-layer cartridges filled with a new carbon adsorbent for the quantitative determination of volatile organic compounds in the atmosphere

The ability of a new graphitized carbon black adsorbent (Carbograph 5) to retain volatile organic compounds (VOCs) in air has been investigated through laboratory experiments performed by frontal chromatography. An artificial mixture containing 19 different compounds from C 1 to C 7 at levels of 50 ppb (v/v) each was used as eluent. The amounts of VOCs retained by Carbograph 5 were determined by high-resolution GC–flame ionization detection after thermal desorption at 250°C. The retention features of this adsorbent were compared with those provided by Carbograph 1 and Carbograph 2, two graphitic carbons equivalent in specific surface area and adsorption properties to Carbopack B and Carbopack C, respectively. It was found that Carbograph 5 exhibits safe sampling volumes of VOCs much higher than those of Carbograph 1 and is the only hydrophobic material providing performances comparable to those of some molecular sieve adsorbents. Results obtained indicate that Carbograph 5 can be used alone or in combination with other materials. When combined with lighter adsorbents, it allows the quantitative collection of polar and non-polar VOCs with carbon number higher than 3 in air volumes larger than 5 l at any relative humidity. In combination with stronger carbon molecular sieve adsorbents, it makes possible the quantitative collection of components with volatilities ranging from C 2 to C 7 in small samples.

Retention of halocarbons on a hexafluoropropylene epoxide modified graphitized carbon black Part 6: Eleven fluoroethers and two iodofluoroalkanes

The retention characteristics of 11 ether-based and 2 iodinated halocarbon fluids related to alternative refrigerant research have been studied as a function of temperature on a stationary phase consisting of a 5% (by mass) coating of a low-molecular-mass polymer of hexafluoropropylene epoxide on a graphitized carbon black adsorbent. Measurements were performed at 0, 20, 40, 60, and 80°C for R-E125 and R-E134; at 40, 60, 80, and 100°C for R-E143a, R-CE216, R-E236ea1, R-E245fa1, R-E263fb1, and R13I-1; at 80, 100, 120, and 140°C for R-E235ca2, R-E235da1, R-E347, and R-217I-1; and at 100, 120, 140, and 160°C for R-E280. Measurements were attempted for several other more chlorinated ether-based compounds, but the chromatographic conditions could not be optimized sufficiently to allow standard retention parameters to be measured reliably. Relative retentions as a function of temperature were calculated with respect to the retentions of tetrafluoromethane (R-14) and hexafluorethane (R-116). Qualitative features of the data are examined, and trends are identified. In addition, the relative retention data were fitted to linear models for the purpose of predicting retention behavior of these compounds to facilitate chromatographic analysis.

Retention of halocarbons on a hexafluoropropylene-epoxide modified graphitized carbon black Part 5: heavier ethane- and ethene-based compounds

The retention characteristics of thirteen heavier ethane-based and eight ethene-based halocarbon fluids related to alternative refrigerant research have been studied as a function of temperature on a stationary phase consisting of a 5% (by mass) coating of a low molecular mass polymer of hexafluoropropylene epoxide on a graphitized carbon black adsorbent. Measurements were performed at 0, 20, 40, and 60°C for R-152, and at 20, 40, 60, and 80°C for R-124. Measurements were performed at 40, 60, 80, and 100°C for R-123a, R-152, and R-115I-1, and at 60, 80, 100 and 120 for R-132b and R-1130a, R-1121 ( cis), and R-1121 ( trans). Measurements were performed at 80, 100, 120 and 140°C for R-113, R-123B1, R-141, R-1130 ( cis), and R-1130 ( trans). Measurements were performed at 100, 120, 140, and 160°C for R-113a, R-121, R-122, R-131, R-131a, R-1110, R-1111, and R-1120. Relative retentions as a function of temperature were calculated with respect to the retentions of tetrafluoromethane (R-14) and hexafluoroethane (R-116). Qualitative features of the data are examined, and trends are identified. In addition, the relative retention data were fitted to linear models for the purpose of predicting retention behavior of these compounds to facilitate chromatographic analysis.

Retention of halocarbons on a hexafluoropropylene epoxide-modified graphitized carbon black IV. Propane-based compounds

The retention characteristics of 25 propane-based bromofluorocarbon, chlorocarbon, chlorofluorocarbon, and fluorocarbon fluids have been studied as a function of temperature on a stationary phase consisting of a 5% (m/m) coating of a low-molecular-mass polymer of hexafluoropropylene epoxide on a graphitized carbon black adsorbent. Measurements were performed at 0, 20, 40 and 60°C for R-245ca and R-245cb. Measurements were performed at 20, 40, 60 and 80°C for R-227ca, R-227ea, R-236ea, R-236fa, R-245fa, R-263fb. Measurements were performed at 40, 60, 80 and 100°C for R-217ba, R-254cb and R-1243b, and at 60, 80, 100 and 120°C for R-280da and R-217caB1. Measurements were performed at 80, 100, 120 and 140°C for R-215aa, R-216ba, R-253fb, R-262da, and R-270aa. Measurements were performed at 100, 120 140 and 160°C for R-215ba, R-225ca, R-225cb, R-243db, R-270da, R-270fa, and R-270fb. Relative retentions as a function of temperature were calculated with respect to the retentions of tetrafluoromethane (R-14) and hexafluoroethane (R-116). Qualitative features of the data are examined, and trends are identified. In addition, the relative retention data were fitted to linear models for the purpose of predicting retention behavior of these compounds to facilitate chromatographic analysis.

Retention of halocarbons on a hexafluoropropylene epoxide-modified graphitized carbon black: III. Ethene-based compounds

The retention characteristics of 11 ethene-based chlorofluorocarbon, bromochlorofluorocarbon and fluorocarbon fluids have been studied as a function of temperature on a stationary phase consisting of a 5% (m/m) coating of a low-molecular-mass polymer of hexafluoropropylene epoxide on a graphitized carbon black adsorbent. Measurements were performed at −20, 0, 20 and 40°C for trifluoroethene (R-1123), 1,1-difluoroethene (R1132a), and fluoroethene (vinyl fluoride, R-1141). Measurements were performed at 40, 60, 80 and 100°C for 1,1-dichloro-2,2-difluoroethene (R-1112a), chlorotrifluoroethene (R-1113), 2-chloro-1,1-difiuoroethene (R-1122), 1-chloro-1-fluoro-ethene (R-1121a), 2-bromo-1,1-difluoroethene (R-1122B1) and bromoethene (vinyl bromide, R-1140B1). Measurements were performed at 60, 80, 100 and 120°C for trans-1,2-dichloro-1,2-difluoroethene (R-1112t) and cis-1,2-dichloro-1,2-difluoroethene (R-1112c), Net retention volumes, corrected to a column temperature of 0°C, were calculated from retention time measurements, the logarithms of which were fitted against reciprocal thermo-dynamic temperature. The relative retentions, also as a function of temperature, were calculated with respect to the retentions of tetrafluoromethane (R-14) and hexafluoroethane (R-116). Qualitative features of the data are examined, and trends are identified. In addition, the data were fitted to linear models for the purpose of predicting retention behavior of these compounds to facilitate Chromatographic analysis.

Retention of halocarbons on a hexafluoropropylene epoxide-modified graphitized carbon black II. Ethane-based compounds

The retention characteristics of 18 ethane-based chlorofluorocarbon, bromochlorofluorocarbon and fluorocarbon fluids have been studied as a function of temperature on a stationary phase consisting of a 5% (mass/mass) coating of a low-molecular-mass polymer of hexafluoropropylene epoxide on a graphitized carbon black adsorbent. Measurements were made at −20, 0, 20 and 40°C for hexafluoroethane (R-116), pentafluoroethane (R-125), 1,1,2,2-tetrafluoroethane (R-134), 1,1,1,2-tetrafluoroethane (R-134a), 1,1,2-trifluoroethane (R-143), 1,1,2-tri-fluoroethane (R-143a), 1,1-difluoroethane (R-152a), and fluoroethane (R161). Measurements were made at 40, 60, 80 and 100°C for 1,2-dichlorotetrafluoroethane (R-114), 1,1-dichlorotetrafluoroethane (R-114a), chloropentafluoroethane (R-115), 2,2-dichloro-1,1,1-trifluoroethane (R-123), 2-chloro-1,1,1- trifluoroethane (R-133a), 1,1-dichloro-1-fluoroethane (R-141b), 1-chloro-1,1-difluoroethane (R-142b), and 1-chloroethane (R-160). Measurements were performed at 60, 80, 100 and 120°C for 1-bromo-2-chlorotetrafluoroethane (R-114B1). Net retention volumes, corrected to a column temperature of 0°C, were calculated from retention time measurements, the logarithms of which were fitted against reciprocal thermodynamic temperature. The relative retentions, also as a function of temperature, were calculated with respect to the retention of tetrafluoromethane and hexafluoroethane. Qualitative features of the data are examined, and trends are identified. In addition, the data were fitted to linear models for the purpose of predicting retention behavior of these compounds to facilitate chromatographic analysis.

Use of thermally modified carbon black and carbon molecular sieve adsorbents in sampling air contaminants

Abstract

Enthalpy of displacement of binary liquid mixtures on solid surfaces part II. Analysis of S-shaped excess isotherms

The adsorption and enthalpy of displacement in methanol—benzene mixtures have been studied on adsorbents with different surface polarities: hydrophobic silica, activated carbon and graphitized carbon black. An investigation of systems producing S-shaped excess isotherms was conducted to determine which function transformations can be used to transform the integral enthalpy of displacement isotherms into the function ψ s 1 = f (ø 1), the shape of which corresponds to the function ø s 1 = f (ø 1) calculated from the excess isotherms. It has been established that, in the event of ideal behaviour of the adsorption layer (Δ H se = 0), the composition of the interfacial layer (ø s 1) is identical to the displacement factor (ψ s 1), i.e. the composition of the surface layer can be determined merely from calorimetric data. The excess enthalpy of the adsorption layer (Δ H se≠ 0) on the surface of the graphitized carbon black adsorbent with a homogeneous surface energy distribution agrees to a good approximation with that of the bulk phase measured experimentally.