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PubMed1998

Variability of mitomycin C adsorption by activated charcoal.

A saline suspension of mitomycin C adsorbed on activated charcoal and administered intraperitoneally has been reported to be safe and effective in the treatment of gastric carcinoma. Activated charcoal specifically targets tumour and lymph-node tissues and the sustained higher local drug concentration is thought to be beneficial. The charcoal particles used in these suspensions have varied in size from > 147 microm to < 20 nm in diameter, but no data have been published to show how this might affect drug adsorption and delivery. Any variability in drug adsorption could pose a serious clinical risk for drugs with a narrow therapeutic index. We have, therefore, investigated the adsorption of mitomycin C on activated charcoal in-vitro. Activated charcoal was ground and sieved to yield four size-fractions between 180 and 53 microm. Adsorption isotherms (n > or = 3) were constructed and applied to the Freundlich model with 0-l00 microg mL(-1) mitomycin C measured by HPLC with detection at 365 nm. Adsorption of mitomycin C by activated charcoal varied by a factor of three under identical conditions at room temperature (21 degrees C) and at 37 degrees C. The specific adsorption (microg mitomycin C (mg activated charcoal)(-1)) was generally higher at 37 degrees C than at room temperature. The variability of mitomycin C adsorption was greatly reduced by addition of the surface-active agent polyvinylpyrollidone, used to determine that adsorption of mitomycin C was independent of activated charcoal particle size. The characteristics of adsorption of mitomycin C by activated charcoal are complex and should be thoroughly investigated to discover the critical controlling factors before submitting the suspensions for further clinical evaluation.

Adsorption↗
PubMed1986

Effect of purgatives on antidotal efficacy of oral activated charcoal.

The effects of purgatives on the antidotal efficacy of oral activated charcoal were studied in seven volunteer subjects. The volunteer subjects were given 1000 mg of aspirin, 100 mg of atenolol and 50 mg of phenylpropanolamine with 100 ml of water on an empty stomach and were assigned randomly to the following treatment groups: after 5 min 150 ml of water, after 5 min 25 g of charcoal, after 5 min charcoal orally with 20 mg of metoclopramide rectally, followed by 10 mg of bisacodyl rectally 3 h afterwards, after 5 min charcoal with 250 ml of magnesium citrate USP and after 60 min charcoal with metoclopramide followed by bisacodyl 3 h thereafter. The plasma concentrations (0-24 h) and the cumulative urinary excretion (0-72 h) of salicylates, atenolol and phenylpropanolamine were measured. Both magnesium citrate and metoclopramide combined with bisacodyl hastened the gastrointestinal transit but magnesium citrate was more effective. Charcoal alone reduced the absorption of aspirin and phenylpropanolamine by about 50% and that of atenolol by about 95%. The purgatives did not modify significantly the efficacy of charcoal. When the antidotal treatment was delayed by 60 min its efficacy was reduced to some extent, possibly depending on the pharmaceutical formulation of the test drugs. The present results do not support the routine use of purgatives in combination with activated charcoal. In some instances, however, their use may promote the evacuation of, for example, depot formulations from the gastrointestinal tract and thus have a beneficial effect together with activated charcoal in reducing absorption.

Administration, Oral↗
PubMed1992

Prevention of chloroquine absorption by activated charcoal.

1. The ability of activated charcoal to prevent the absorption of chloroquine was investigated in healthy volunteers, and the effect of the charcoal-chloroquine ratio on the completeness of binding was studied in vitro. 2. After an overnight fast, six subjects ingested 500 mg of chloroquine phosphate with water, and another group of six subjects ingested 25 g of charcoal suspension within 5 min of chloroquine intake. The concentrations of chloroquine in plasma and whole blood were measured by high-performance liquid chromatography for 192 h. 3. Activated charcoal reduced the areas under the plasma and whole blood chloroquine concentration-time curves (AUC) from 0 to 192 h, the total AUCs, and the peak concentrations by 99% (P less than 0.001). 4. Chloroquine was very effectively bound by activated charcoal in vitro, even at low charcoal-chloroquine ratios. For example, at a ratio of 5:1, about 98% of chloroquine was bound. 5. Activated charcoal should be very effective in reducing the absorption of that fraction of chloroquine dose which is in the stomach at the time of charcoal administration. Because the acute toxicity of chloroquine is extremely high and death usually occurs within 1-3 h of overdosage, charcoal should be given as early as possible in suspected chloroquine intoxication.

Adult↗
PubMed2002

Charcoal is a sensitive, specific, and stable marker for the diagnosis of aspiration in hamsters.

The diagnosis of recurrent aspiration in young children is a perpetual challenge because there is no specific gold standard test to be used. The finding of lipid-laden alveolar macrophages in bronchoalveolar lavage (BAL) is a sensitive but nonspecific marker for the diagnosis of aspiration. We conducted a short-term study comparing tracheal instillation of saline, milk, or a milk-charcoal mixture in hamsters. BAL cytology, lipid-laden alveolar macrophage index, charcoal alveolar macrophage index, and lung histology were monitored for 10 d. A long-term study was performed, and hamsters were monitored for 92 d after milk-charcoal tracheal instillation. Baseline animals (n = 4) had no tracheal instillation. Saline- and milk-instilled animals had BAL performed after 1 (n = 4), 3 (n = 4), and 10 (n = 4) d. Milk-charcoal-instilled animals had BAL performed after 1 (n = 4), 3 (n = 4), 10 (n = 4), 30 (n = 2), 58 (n = 2), and 92 (n = 2) d after tracheal instillation. Total cell counts and percent neutrophils in BAL fluid increased significantly and similarly after milk and milk-charcoal instillation on d 1 compared with baseline and saline-instilled animals. Lipid-laden alveolar macrophage index increased significantly only on d 3 after milk and milk-charcoal instillation compared with all days in the saline-instillation group. Charcoal alveolar macrophage index increased significantly after milk-charcoal instillation (d 1-58) from baseline or all days in the saline-instillation group. We conclude that charcoal particles instilled in tracheas of hamsters can be easily identified in BAL fluid and in lung parenchyma for as long as 3 mo after a single instillation and could potentially be used as a sensitive, specific, and stable marker for the diagnosis of aspiration, although the issue of its applicability to humans is still unsolved.

Animals↗
PubMed2004

Risk factors for emesis after therapeutic use of activated charcoal in acutely poisoned children.

OBJECTIVES: Vomiting frequently complicates the administration of activated charcoal. The incidence of such vomiting is not defined precisely in the pediatric population. Little is known about the patient-, poison-, or procedure-specific factors that contribute to emesis of charcoal. This study aimed to estimate the incidence of vomiting subsequent to therapeutic administration of charcoal to poisoned children < or =18 years of age and to examine the relative contributions of several risk factors to the occurrence of vomiting. METHODS: Data were collected on a prospective cohort of 275 consecutive children who were treated with activated charcoal for acute poisoning exposure. The study was set in the emergency department of an urban, tertiary-care children's hospital. Sorbitol content of the charcoal was alternately assigned. Potential risk factors for vomiting were recorded prospectively, and the occurrence of vomiting within 2 hours of charcoal administration was measured. RESULTS: A total of 56 (20.4%) of 275 patients vomited. Median time to vomiting was 10 minutes. Previous vomiting (relative risk: 3.41; 95% CI: 1.48-7.85) and nasogastric tube administration (relative risk: 2.40; 95% CI: 1.13-5.09) were found to be the most significant independent risk factors for vomiting. The increased risk among children >12 years of age, compared with younger children, approached significance. Sorbitol content, large charcoal volumes, or fast administration rates did not increase vomiting risk significantly. CONCLUSIONS: One of every 5 children who are given activated charcoal within our pediatric emergency department vomited. Children with previous vomiting or nasogastric tube administration were at highest risk, and these factors should be accounted for in future investigation of antiemetic strategies. Sorbitol content of charcoal was not a significant risk factor for emesis.

Adolescent↗
PubMed1987

In vitro study of boric acid and activated charcoal.

An in-vitro study utilizing a titration assay was performed to evaluate the degree of adsorption of one gram of boric acid by 7.5 g, 15.0 g and 30.0 g of activated charcoal. The mean percentage adsorbed was 5.7 +/- 1.6% for 7.5 g of activated charcoal, 17.6 +/- 3.5% for 15.0 g of activated charcoal and 38.6 +/- 6.3% for 30.0 g of activated charcoal. Analysis of variance showed a significant difference from the control (no activated charcoal) for the 15.0 and 30.0 g samples (p less than 0.05). Although binding of boric acid by activated charcoal increased as the proportion of activated charcoal to boric acid increased, this finding is not clinically significant since the amount of activated charcoal required for 38% adsorption is 30 times the amount of boric acid ingested. Considering the toxic and potentially fatal doses of boric acid in children (5 g) and adults (20 g), doses of activated charcoal of greater than 150 g in children or 600 g in adults would be impractical for the clinical situation.

Adsorption↗
PubMed1992

Carbamazepine overdose--the effects of multiple dose activated charcoal.

We studied five children with carbamazepine overdose. Two patients had acute overdose without previous exposure to carbamazepine while three presented with acute-on-chronic overdose. Multiple doses of activated charcoal were administered to four patients. One acute-on-chronic patient did not receive any activated charcoal. The mean half-life of carbamazepine was as follows: a) Acute vs. Acute-On-Chronic overdose: 8.63 h vs. 12.01 h (p less than 0.05); b) No Activated Charcoal vs. 30-50 g Activated Charcoal vs. 60-90 g Activated Charcoal: 23.3 h vs. 10.17 h vs. 7.21 h (p less than 0.05); c) No Activated Charcoal vs. 2-3 doses vs. 7-12 doses: 23.3 h vs. 8.96 h vs 7.55 h (ns). Although the half-life of carbamazepine decreased in a linear relationship with the total amount of activated charcoal administered (r = -0.86), there was no relationship between the time to complete recovery and administration of multiple doses of activated charcoal. Although multiple doses of activated charcoal increased the clearance of carbamazepine in our patients with overdose, it was not associated with clinical benefits.

Acute Disease↗
PubMed1994

In vitro adsorption of dichlorvos and parathion by activated charcoal.

Accidental and suicidal ingestions of organophosphate compounds continue to be a common occurrence in Turkey. Activated charcoal administration without gastric emptying has been advocated as primary therapy in most acute poisoning cases, although some references do not recommend activated charcoal use in organophosphate poisoning. This study was performed to determine the in vitro adsorption of dimethyl dichlorovinyl phosphate (dichlorvos) and parathion by activated charcoal over a wide range of charcoal:organophosphate ratios (1:1, 2.5:1, 5:1, 10:1 and 20:1, g:g). The charcoal binding ability of dichlorvos and parathion were studied in both pH 1.2 and pH 7 environments. The supernatant was extracted with n-hexane and then analyzed by gas chromatography. Each incremental increase in charcoal dose increased the percent adsorption of dichlorvos and parathion. At the 20:1 ratio, 82.8 +/- 2.0/87.3 +/- 2.9% (pH 1.2/7.0) of dichlorvos and 59.3 +/- 4.5/64.5 +/- 6.1% (pH 1.2/7.0) of parathion were bound by activated charcoal. There were no significant differences in amounts of compound bound in the acid and neutral solutions. Large doses of activated charcoal effectively bind dichlorvos and parathion in vitro. In vivo research should be performed to determine activated charcoal's role in organophosphate poisoning cases.

Adsorption↗
PubMed1979

Sucrose as a sweetener for activated charcoal.

The efficacy of sucrose as a flavor for activated charcoal was studied. In vitro adsorption of sucrose (in Simulated Gastric Fluid, USP, without pepsin) to activated charcoal, and of a 1-g/liter sodium salicylate solution to a 1:1 mixture of sucrose and activated charcoal and to plain activated charcoal, was measured spectrophotometrically. In vitro adsorption of sucroses to activated charcoal was minimal. Sucrose reduced in vitro adsorption of sodium salicylate to activated charcoal by only small amounts. For example, at a ratio of 4 g activated charcoal to 1 g sodium salicylate, sucrose reduced salicylate adsorption to activated charcoal from 99% to 95%. A 1:1 sucrose-activated charcoal preparation provides sufficient flavor without substantial loss of adsorbance.

Adsorption↗
PubMed1976

Specific extraction of antigen in vivo by extracorporeal circulation over antibody immobilized in collodion-charcoal.

A novel extracorporeal immunoadsorbent is described in which anti-bovine serum albumin (anti-BSA) was entrapped in collodion membranes adherent to activated charcoal particles. This immunoadsorbent was capable of specifically removing circulating BSA in vitro and in vivo in an extracorporeal system in dogs. In preparation of the immunoadsorbent, up to 81.2% of added anti-BSA was retained on collodion-charcoal. In vitro circulation studies demonstrated that anti-BSA collodion-charcoal removed 812% more 125I-BSA than control colloidon-charcoal. For in vivo studies, an extracorporeal circulation system was established and arterial blood was passaged through a continuous flow celltrifuge wherein plasma which was separated from formed elements of the blood was circulated over anti-BSA and control rabbit gamma-globulin collodion-charcoal. 125I-BSA was passively infused into mongrel dogs, and plasma was then circulated over extracorpeal immunoadsorbents for 2 hr. Results showed up to 896% greater uptake of circulating 125I-BSA on the charcoal containing immobilized anti-BSA compared to control charcoal. There was no evidence of release of anti-BSA from the immunoadsorbent since 125I-anti-BSA cpm on the charcoal before and after the experiments were unchanged. In addition, there were no significant alterations in hematocrit, leukocyte counts, serum sodium, potassium, calcium, magnesium, or creatinine levels before and after in vivo procedures. These data suggest that this immunoadsorbent consisting of anti-BSA immobilized in collodion membranes adherent to charcoal particles may specifically withdraw circulating antigens in vivo with minimal release of entrapped antibodies and no significant alteration in the host hematologic and biochemical status.

Animals↗
PubMed1981

Increase of ionic strength for charcoal separation of B/F fractions in radioimmunoassays.

The increase in protein adsorption by charcoal as ionic strength increases (salting-out adsorption), was used to separate the bound and free fractions of glucagon, insulin, hGH, hLH and hPRL in the radioimmunoassay. The hormones were labelled with 125I and to express the immunocomplex, gamma-globulin was labelled with 125I. The charcoal used to produce the separation was suspended in magnesium sulfate 3 M (charcoal-SO4Mg). The optimum amount of charcoal and the final concentration of magnesium sulfate determined for each hormone were: glucagon (charcoal 5 mg/tube, 0.125 M); insulin (charcoal 5 mg/tube, 0.131 M); hGH (charcoal 40 mg/tube, 0. 447 M); hLH (charcoal 40 mg/tube, 0.447 M) and hPRL (charcoal 60 mg/tube, 0.321 M). The serum concentration was 1/20 for all hormones, excepting glucagon, where 1/10 was used. The stability of the immunocomplex was studied and it was shown that, under suitable conditions, increased ionic strength does not cause the dissociation of the bound fraction.

Adsorption↗
PubMed1984

Effect of the surface area of activated charcoal on theophylline clearance.

The effect of the surface area of activated charcoal on theophylline clearance was studied. Eight fasting, healthy men received intravenous infusions of either aminophylline (6 mg/kg, N = 3) or theophylline (5 mg/kg, N = 5) over 1 hour followed by either 5 Gm standard activated charcoal every 2 hours, 20 Gm every 2 hours, or 5 Gm PX-21 activated charcoal (with 3.6 times the surface area) every 2 hours. Theophylline t 1/2 and AUC with each regimen were respectively 6.3 +/- 0.5 (S.E.) hours and 88.9 +/- 8.4 mg/liter X hr with 5 Gm standard activated charcoal, 5.3 +/- 0.3 hours and 75.4 +/- 4.9 mg/liter X hr with 5 Gm PX-21, and 4.9 +/- 0.2 hours and 67.7 +/- 3.6 mg/liter X hr with 20 Gm standard activated charcoal. There was a relationship between the activated charcoal surface area and the reduction in theophylline t 1/2 and AUC. We conclude that the clearance of theophylline is related to the surface area of activated charcoal administered and that PX-21 may be a more potent activated charcoal product for enhancing theophylline removal.

Administration, Oral↗
PubMed1992

Reversible adsorption of nicotinic acid onto charcoal in vitro.

The effects of various factors on the adsorption of nicotinic acid onto and desorption from activated charcoal were investigated in vitro. The affinity of nicotinic acid for charcoal was poor both in acidic and neutral media. Adsorption increased with increasing charcoal:drug ratios and decreasing incubation volume:charcoal ratios. Desorption of nicotinic acid from dried drug-charcoal complexes was investigated in a Sartorius dissolution apparatus. The rate of the rapid, initial desorption depended on the pH and the amounts of charcoal and drug. As equilibrium was reached in the dissolution chamber, the release rate of nicotinic acid decreased slowly, depending mainly on the flow of the medium. Thus, nicotinic acid preadsorbed onto charcoal was released in a sustained manner under "continuous flow" conditions. However, because of the poor affinity for nicotinic acid, charcoal may not be a suitable matrix for sustained release of nicotinic acid.

Adsorption↗
PubMed2002

Removal of trivalent chromium from tannery waste waters using bone charcoal.

The ability of bone charcoal to remove Cr(III) from aqueous solutions by adsorption has been investigated. The adsorbent used was first characterised and then the adsorption was studied as a function of time and amount of charcoal. Tests were carried out with synthetic solutions whose Cr concentrations (500 mg L(-1)) were similar to those found in some effluents of Moroccan tannery industries. Cr removal efficiencies higher than 90% were obtained at pH 3.5 using 3 g of bone charcoal and a stirring time of about 30 min. Results of Cr removal by all sieved fractions of bone charcoal had shown the same interesting capabilities for Cr(III) retention. The cross interference with other elements was also investigated. Pre-treatment of bone charcoal by nitric acid led to an increase in its specific surface area but induced a drastic reduction in its Cr elimination abilities. Adsorption tests were also carried out using calcinated bone charcoal. The results obtained showed a similar percentage of Cr retention to those found with untreated bone charcoal. On the other hand, a double treatment of bone charcoal with HCl and NaOH provided an enhancement of Cr(III) retention. The role played by the mineral fraction of the solid phase of bone was thus evidenced.

Adsorption↗
PubMed1996

Measurement of insulin-like growth factor (IGF)-II binding to purified IGF binding proteins 1-6: comparison of charcoal adsorption and high performance size exclusion chromatography.

Insulin-like growth factor (IGF) binding to IGF binding proteins is commonly assessed by adsorbing free IGF to albumin-coated charcoal and quantitating bound IGF in the supernatant, but the validity of this technique has been questioned and many variations have been described. We compared the measurement of binding affinity and capacity of purified IGFBPs 1-6 for IGF-II using charcoal adsorption and Superdex G75 high performance size exclusion chromatography (HPSEC) to separate free and bound 125I-IGF-II. Optimal HPSEC recovery and resolution was obtained for IGFBP-1 and IGFBP-6 with low salt buffer (0.1 M sodium phosphate, pH 7.4), whereas phosphate buffer supplemented with 0.5 M NaCl was optimal for IGFBPs 2-5. Measurement of binding of 125I-IGF-II to IGFBPs 3-5 using the charcoal assay was also increased by the use of high salt buffer. Under optimal conditions, charcoal measurements of 125I-IGF-II binding to IGFBPs 1-5 were consistently lower than HPSEC measurements. By competitive binding using unlabeled IGF-II, the binding affinity of each of the IGFBPs for IGF-II was the same using both methods. Similarly, binding affinities as measured by charcoal assay were not affected by buffer composition. Differences in total binding obtained using the two methods and under different conditions were therefore due to differences in binding capacity. Charcoal adsorbs 15% of cross-linked 125I-IGF-II:IGFBP complexes which may partially explain the lower binding capacity for IGFBPs 1-5 determined by charcoal adsorption. Charcoal adsorption and HPSEC, therefore, are both valid methods for the measurement of binding affinities of IGFBPs for IGF-II, but assay conditions must be validated prior to measurement of binding capacity.

Adsorption↗
PubMed1992

Physicochemical characteristics of drugs and response to repeat-dose activated charcoal.

Although the administration of repeated doses of activated charcoal has been advocated to increase the systemic clearance of many drugs, it is unknown whether a drug's physicochemical properties are associated with enhanced removal by repeat-dose activated charcoal. The English language literature was searched to identify clinical studies evaluating repeat-dose activated charcoal. Percent reduction in plasma elimination half-life during repeat-dose activated charcoal was calculated and correlated with the drugs' characteristics. A step-wise multiple regression analysis with the independent variables of the drugs' molecular weight, pKa, plasma protein-binding, intrinsic plasma elimination half-life, and volume of distribution failed to identify potential predictors (P = .1) of effectiveness of repeat-dose activated charcoal. This analysis suggested that charcoal therapy was more effective for drugs with a longer intrinsic half-life (r2 = .24, P = .04). A uniform framework that evaluates the physicochemical characteristics of drugs and their response to repeat-dose activated charcoal is needed to better define which patients would benefit from repeat-dose activated charcoal therapy.

Adult↗
PubMed1998

A novel charcoal-induced model of obliterative bronchiolitis-like lesions: implications of chronic nonspecific airway inflammation in the development of posttransplantation obliterative bronchiolitis.

OBJECTIVES: In this study, we describe the development of a nonallogeneic animal model of obliterative bronchiolitis-like lesions. Furthermore, we examined whether chronic rejection alone can lead to the development of obliterative bronchiolitis or whether additional nonspecific airway inflammation is required. METHODS: Part I: Rats were intratracheally injected with 0.2 ml of activated charcoal or sorbitol solution (carrier for charcoal control). Animals were put to death beginning at 2 weeks up to 20 weeks. Part II: Animals were divided into three groups: group I, underimmunosuppressed Brown Norway to Lewis lung allografts; group II, charcoal-treated underimmunosuppressed allografts; and group III, charcoal-treated rats. Animals were put to death at 3 months after transplantation. RESULTS: Part I: In charcoal-laden bronchioles, subacute nonspecific airway inflammation was detected at 2 weeks. Slow, subclinical fibroproliferation ensued during the following weeks. Obliterative bronchiolitis-like lesions were observed in 80% of charcoal-treated animals at 12 weeks. Part II: Allografts developed extensive vascular lesions consistent with acute and chronic vascular rejection. Obliterative bronchiolitis-like lesions were scarcely detected. Charcoal-treated allografts demonstrated evidence of diffuse and severe obliterative bronchiolitis-like lesions. CONCLUSIONS: Transtracheal injection of activated charcoal into native lungs results in slowly progressive airway injury and inflammation leading to obliterative airway lesions. Inadequate immunosuppression primarily results in chronic vascular rejection but not obliterative bronchiolitis. Underimmunosuppressed allografts subjected to nonspecific airway inflammation develop obliterative airway lesions that are more prominent than in native lungs. This suggests that a cofactor to chronic rejection is likely necessary for the development of lung transplant obliterative bronchiolitis.

Animals↗
PubMed2005

Characterization of aromatic compound sorptive interactions with black carbon (charcoal) assisted by graphite as a model.

Molecular interactions controlling the sorption of pollutants to environmental black carbons (soot, charcoal) are not well-resolved. Sorption of a series of aromatic compounds was studied to wood charcoal and nonporous graphite powder as a model adsorbent. Issues of concern were the possible involvement of pi-pi electron donor-acceptor (EDA) interactions of electron-poor and electron-rich solutes with the graphene (polycyclic aromatic) surface and size exclusion effects. Sorption of pi-acceptors, benzonitrile (BNTL), 4-nitrotoluene (MNT), 2,4-dinitrotoluene (DNT), and 2,4,6-trinitrotoluene (TNT), and to a lesser extent pi-donor solutes, naphthalene (NAPH) and phenanthrene (PHEN), was greater than predicted by hydrophobic driving forces in accord with their acceptor or donor strength. Hydrophobic effects were estimated using a concentration-dependent free energy relationship between adsorption and partitioning into an inert solvent (n-hexadecane or benzene) for a non-donor/non-acceptor calibration set (benzene and chlorinated and methylated benzenes). Molecular complexation between acceptors and model graphene donors, NAPH, PHEN, and pyrene (PYR), in chloroform and benzene was tracked by ring-current induced upfield shifts in the 1H NMR spectrum and by charge-transfer bands in the UV/visible spectrum. The EDA component of graphite-water adsorption for the acceptors correlated with the NMR-determined complexation constant with the model donors in chloroform, which, in turn, correlated with pi-acceptor strength (TNT > DNT > MNT > BNTL) and pi-donor strength (PYR > PHEN > NAPH). Charcoal-graphite isotherms calculated from charcoal-water and graphite-water isotherms indicated molecular sieving effects on charcoal for tetrasubstituted benzenes (tetramethylbenzenes and TNT) and some trisubstituted benzenes (1,3,5-trichlorobenzene, possibly DNT). When steric effects are taken into account, the order in adsorption among acceptors was qualitatively similar for graphite and charcoal. The results suggest pi-pi EDA interactions of the acceptors-and possibly donors, although the calibration set may underestimate the hydrophobic effect for fused ring systems-with both graphite and charcoal surfaces. For graphite, it is postulated that pi-acceptors interact with electron-rich regions of the basal plane near edges and defects and that pi-donors interact with electron-depleted regions further away. A similar mechanism may operate on the charcoal but would be modified by the (mostly) electron-withdrawing effects of 0 functionality on the edges of graphene sheets.

Adsorption↗