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CD
Kinds of CD Terms modified by CD Selected AbstractsPerformance of collaborative codes in CSMA/CD environmentEUROPEAN TRANSACTIONS ON TELECOMMUNICATIONS, Issue 5 2006F. Gebali A new medium access control scheme is proposed for implementing collaborative codes in a system using carrier sense multiple access with collision detection protocol (CC-CSMA/CD). We also propose a new backoff algorithm which is simple to implement and to analyse. A discrete-time Markov chain analytical model is developed for CC-CSMA/CD. The resulting model describes the regular CSMA/CD as a special case. Protocol performance measures were studied such as throughput, packet acceptance probability, average packet delay and channel utilisation. It is found that CC-CSMA/CD offers improvements over a system that uses CSMA/CD in terms of throughput, packet acceptance probability, delay and channel utilisation. Copyright © 2006 AEIT. [source] Effects of in utero exposure to 2,2,,4,4,,5,5,-hexachlorobiphenyl (PCB 153) on somatic growth and endocrine status in rat offspringCONGENITAL ANOMALIES, Issue 4 2008Kenichi Kobayashi ABSTRACT Exposure to polychlorobiphenyl (PCB) mixtures at an early stage of development has been reported to affect endocrine glands; however, little is known about the precise toxicological properties of individual PCB. The present study was undertaken to determine whether prenatal exposure to 2,2,,4,4,,5,5,-hexachlorobiphenyl (PCB 153), a di- ortho -substituted non-coplanar congener, affects postnatal development in rat offspring. Pregnant Sprague-Dawley rats (Crj: CD (SD) IGS) were given PCB 153 (0, 16, or 64 mg/kg/day) orally from gestational day (GD) 10 through GD 16, and developmental parameters in the male and female offspring were examined. We found no dose-dependent changes in body weight, body length (nose,anus length), tail length, or the weights of kidneys, testes, ovaries and uterus in offspring at 1 or 3 weeks of age. Liver weights were increased in the PCB 153,treated groups, although we observed a significant difference only in males. Anogenital distance was unaffected in the PCB 153,treated groups. We observed a significant dose-dependent decrease in the plasma concentrations of thyroxine and tri-iodothyronine, whereas those of thyroid-stimulating hormone were not significantly changed. In addition, there were no dose-dependent changes in plasma concentrations of growth hormone and insulin-like growth factor-I in any dose group. These findings suggest that prenatal exposure to PCB 153 (GD 10,16, 16,64 mg/kg/day) may alter the thyroid status in rat offspring to some extent without affecting somatic growth or its related hormonal parameters. [source] Augmentation of skin response by exposure to a combination of allergens and irritants , a reviewCONTACT DERMATITIS, Issue 5 2004Line Kynemund Pedersen Clinical experimental studies on contact dermatitis (CD) often evaluate the effect of one allergen or one irritant at a time. In real life, the skin is often exposed to more allergens, more irritants or allergens and irritants in combination. This combined exposure may potentially influence irritant effects as well as allergenicity of the substances. Mechanisms for a changed response can be immunological effects or enhanced penetration. Knowledge about the influence on skin reaction of combined exposures may influence skin reactivity and is important for prevention of CD. For allergens, threshold values may be influenced by the presence of other allergens or irritants, and prevention of CD by regulation of threshold values may not be sufficient if this is not taken into account. [source] What are adolescent antecedents to antisocial personality disorder?CRIMINAL BEHAVIOUR AND MENTAL HEALTH, Issue 1 2002Rolf Loeber PhD Background This paper fills a gap because there are very few studies that prospectively predict antisocial personality disorder (APD) from psychopathology earlier in life in clinic-referred samples of young males. Method The paper addresses the continuity between conduct disorder (CD) and other forms of psychopathology during ages 13,17 and modified APD at ages 18 and 19 (modified to remove the DSM-IV requirement of pre-existing CD by age 15) in the Developmental Trends Study. Results The results show that 82,90% of APD cases met criteria for CD at least once during ages 13,17, and very few youths who met criteria for ODD during this period progressed to APD without intermediate CD. While CD is a strong predictor of modified APD, when other factors were accounted for in regression analyses, the best predictors were callous/unemotional behaviour, depression and marijuana use. ADHD during ages 13,17 was not significant in the final model. Males with CD during adolescence who progressed to APD tended to commit more violence, as evident from their court records. Conclusions Implications are discussed for the conceptualization of developmental models leading to APD, the strengthening of relevant symptoms of CD predictive of APD, and preventive and remedial interventions. Copyright © 2002 Whurr Publishers Ltd. [source] A question for DSM-V: which better predicts persistent conduct disorder , delinquent acts or conduct symptoms?CRIMINAL BEHAVIOUR AND MENTAL HEALTH, Issue 1 2002Jeffrey D. Burke PhD Background Conduct disorder (CD), a psychiatric index of antisocial behaviour, shares similarities with delinquency, a criminological index. This study sought to examine which factors in childhood predict a repeated diagnosis of CD in adolescence, and whether self-reported delinquent acts enhance the utility of symptoms of CD in predicting later persistent CD. Method Longitudinal data used in this paper come from a clinic-referred sample of 177 boys, along with their parents and teachers, who were assessed using a structured clinical interview. The boys also reported on their delinquent behaviours, as well as a broad range of other family and life events. Results Before age 13, 77 boys met criteria for CD according to their parent, 69 according to their own report, and 36 reported three or more delinquent acts. Forty-eight boys (29%) met criteria for CD three or more times between 13 and 17. In childhood, delinquency overlapped, but was distinct from CD. Both were present in 28 cases, while 41 cases had CD without delinquency, and eight had delinquency without CD. When tested as predictors of later persistent CD, child-reported CD was the strongest predictor of later persistent CD, but self-reported delinquency was stronger than parent-reported CD. A final model of significant predictors included child-reported CD, delinquency, poor child communication with parents, and maternal prenatal smoking. Conclusions It appears that delinquency does add uniquely to the prediction of persistent CD. It may be useful to expand the diagnostic criteria for CD accordingly. Copyright © 2002 Whurr Publishers Ltd. [source] Attention deficit hyperactivity disorder and suicide: a review of possible associationsACTA PSYCHIATRICA SCANDINAVICA, Issue 6 2004A. James Objective:, To review the evidence of a possible association between attention deficit hyperactivity disorder (ADHD) and suicide. Design:, We searched the electronic data bases: Medline, Psych LIT, between 1966 and March 2003 looking for articles on ADHD, attention deficit disorder, hyperactivity and suicide. Results:, An association of ADHD and completed suicide was found, especially for younger males. However, the evidence for any direct or independent link was modest with an overall suicide rate from long-term follow-up studies of ADHD of 0.63,0.78%. The estimated relative risk ratio, compared with US national suicide rates (males 5,24 years) is 2.91 (95% confidence interval 1.47,5.7, ,2 = 9.3, d.f. = 1, P = 0.002). ADHD appears to increase the risk of suicide in males via increasing severity of comorbid conditions, particularly conduct disorder (CD) and depression. Conclusion:, Identification of those at risk, particularly males with comorbid ADHD, depression and CD, may represent a useful clinical means of reducing completed suicide. [source] Prospective screening for biopsy proven coeliac disease, autoimmunity and malabsorption markers in Belgian subjects with Type 1 diabetesDIABETIC MEDICINE, Issue 7 2005M. Buysschaert Abstract Aims To determine prospectively the prevalence of biopsy proven coeliac disease (CD) in an adult Type 1 diabetic population from Belgium with regards to associated auto-immunity and malabsorption. Methods and results Determination in 400 Type 1 diabetic patients of serum anti-endomysial and/or anti-transglutaminase auto-antibodies. All subjects with abnormal serology underwent an intestinal biopsy. Ten patients (2.5%) had positive antibodies. Diagnosis of CD was confirmed by an intestinal biopsy. Eight patients were symptom-free, although laboratory findings suggesting malabsorption were prominent in the presence of CD [microcytic anaemia, iron and folate deficiencies, low levels of 25(OH)vitamin D3, calcium and cholesterol]. Other auto-immune conditions, especially vitiligo, were found in patients with CD. Conclusions Asymptomatic coeliac disease occurs frequently in adult Type 1 diabetic patients, and is often associated with subclinical malabsorption. Screening should be part of routine evaluation, to implement life-long dietary gluten avoidance. [source] Fine-needle aspiration cytology of Castleman disease: Case report with review of the literatureDIAGNOSTIC CYTOPATHOLOGY, Issue 12 2008Majorie Deschênes M.D. Abstract Organs involved by Castleman disease (CD) may be investigated by fine-needle aspiration cytology. No specific cytomorphological criteria are currently described for a definitive diagnosis. The cytological features of three fine-needle aspirations from three different lymph nodes of a patient with histologically confirmed CD of the hyaline-vascular type are herein reported, with a review of the literature. The fine-needle aspirations showed branching capillaries associated with fragments of germinal center. Review of the literature yielded 12 other case reports with over half describing similar findings. Because branching hyalinized small blood vessels penetrating follicular germinal center are characteristic of CD of the hyaline-vascular type on histology, this finding in fine-needle aspirates should raise that diagnostic possibility. Diagn. Cytopathol. 2008. © 2008 Wiley-Liss, Inc. [source] PNET-like features of synovial sarcoma of the lung: A pitfall in the cytologic diagnosis of soft-tissue tumorsDIAGNOSTIC CYTOPATHOLOGY, Issue 4 2001Pascale Hummel M.D. Abstract Fine-needle aspiration (FNA) cytology of soft-tissue tumors is evolving. As more experience is gained, we are becoming aware of potential pitfalls. We describe 2 cases of synovial sarcoma of the lung, primary and metastatic, in patients who had FNA biopsy performed on a lung mass. The cytologic smears showed extremely cellular groups of malignant small round cells, intersected by small blood vessels, with numerous loose single cells, in a background of macrophages and mature lymphocytes. The tumors displayed monomorphic cells forming rosettes and displaying occasional mitoses. A diagnosis of neuroendocrine tumor/primitive neuroepithelial tumor (PNET) was suspected. Furthermore, this suspicion was supported by immunohistochemical stains, which showed positivity for a neuroendocrine marker, Leu 7 (case 1), and for a neural marker, CD 99 (O 13 or HBA 71) (both cases); and negativity for cytokeratins (case 1). The resection specimen of case 1 had mostly tightly packed small round cells, with occasional rosettes, similar to the FNA biopsy, and focal areas composed of spindle cells, organized in a focal fibrosarcoma-like and hemangiopericytoma-like pattern. A balanced translocation between chromosomes X and 18, demonstrated by both karyotyping and fluorescent in situ hybridization (FISH), enabled us to make a diagnosis of synovial sarcoma, which was histologically classified as poorly differentiated. Case 2 was a metastatic biphasic synovial sarcoma of the arm, with a prominent epithelial component. Synovial sarcoma, when composed mainly of small round cells on cytologic smears, is a great mimicker of neuroendocrine/PNET tumors, with light microscopic and immunohistochemical overlap. Awareness of this potential pitfall may aid in preventing a misdiagnosis. Its recognition is of major concern, especially for the poorly differentiated variant, because it is associated with a worse prognosis. Diagn. Cytopathol. 24:283,288, 2001. © 2001 Wiley-Liss, Inc. [source] Evaluation of gastroduodenal mucosal lesions in patients with Crohn's disease and ulcerative colitisDIGESTIVE ENDOSCOPY, Issue 3 2004Kazuhiro Maeda Background:, Patients with Crohn's disease (CD) are reported to suffer from upper gastroduodenal lesions with varying frequency, although concurrent Helicobacter pylori infection is reported to be low. Methods:, A prospective study was carried out on patients diagnosed with CD or ulcerative colitis (UC) in order to evaluate the degree of upper gastroduodenal tract involvement and the prevalence of Helicobacter pylori infection. Results:, Gastroduodenal lesions were found in 18 (78%) of 23 CD patients, the location being the stomach in 18 (78%), the duodenal bulb in 16 (70%) and the descending duodenum in 16 (70%). Bamboo joint-like lesions were found in four cases (17%) in gastric body and cardia. In contrast, gastroduodenal lesions were found in 10 (53%) of 19 UC patients, the location being the stomach in nine (47%), the duodenal bulb in six (32%), and the descending duodenum in three (16%). The H. pylori -positive rate in patients with CD and UC was 0%, and 11%, respectively. Conclusion:, Minute upper gastroduodenal lesions are much more common in CD than in UC patients, especially in the descending duodenum. Accordingly, upper gastrointestinal endoscopy would seem to be a useful means with which to obtain a definitive diagnosis in all suspected IBD cases. [source] Treatment of achalasia: lessons learned with Chagas' diseaseDISEASES OF THE ESOPHAGUS, Issue 5 2008F. A. M. Herbella SUMMARY., Chagas' disease (CD) is highly prevalent in South America. Brazilian surgeons and gastroenterologists gained valuable experience in the treatment of CD esophagopathy (chagasic achalasia) due to the high number of cases treated. The authors reviewed the lessons learned with the treatment of achalasia by different centers experienced in the treatment of Chagas' disease. Preoperative evaluation, endoscopic treatment (forceful dilatation and botulinum toxin injection), Heller's myotomy, esophagectomy, conservative techniques other than myotomy, and reoperations are discussed in the light of personal experiences and review of International and Brazilian literature. Aspects not frequently adopted by North American and European surgeons are emphasized. The review shows that nonadvanced achalasia is frequently treated by Heller's myotomy. Endoscopic treatment is reserved to limited cases. Treatment for end-stage achalasia is not unanimous. Esophagectomy was a popular treatment in advanced disease; however, the morbidity/mortality associated to the procedure made some authors seek different alternatives, such as Heller's myotomy and cardioplasties. Minimally invasive approach to esophageal resection may change this concept, although few centers perform the procedure routinely. [source] Clinical Assessment and Rest and Stress Echocardiography for Prediction of Long-Term Prognosis in African Americans with Known or Suspected Coronary Artery DiseaseECHOCARDIOGRAPHY, Issue 5 2009Stephen G. Sawada M.D. Background: There is limited information on noninvasive risk stratification of African Americans, a high-risk group for cardiovascular events. We investigated the value of clinical assessment and echocardiography for the prediction of a long-term prognosis in African Americans. Methods: Dobutamine echocardiography was performed in 324 African Americans. Two-dimensional measurements were performed at rest, and rest and stress wall motion was assessed. A retrospective follow-up was conducted for cardiac events: myocardial infarction (MI) or cardiac death (CD). Results: The mean age was 59 ± 12 years, and 83% of patients had hypertension. The follow-up was obtained in 318 (98%) patients for a mean of 5.3 years. The events occurred in 107 (33%) subjects. The independent predictors of events were history of MI (P = 0.001, risk ratio [RR] 2.04), ischemia (P = 0.007, RR 1.97), fractional shortening (P = 0.033, RR 0.08), and left atrial (LA) dimension (P = 0.034, RR 1.39). An LA size of 3.6 cm and a fractional shortening of 0.30 were the best cutoff values for the prediction of events. Prior MI, ischemia, LA size >3.6 cm, and fractional shortening <0.30 were each considered independent risk predictors for events. The event rates were 13%, 21%, 38%, 59%, and 57% in patients with 0, 1, 2, 3, and 4 risk predictors, respectively. Event-free survival progressively worsened with an increasing number of predictors: 0 or 1 versus 2 predictors, P < 0.001; 2 versus 3 or 4 predictors, P = 0.003. Conclusion: The long-term prognosis of African Americans can be accurately predicted by clinical assessment combined with rest and stress echocardiography. [source] Sensitive Electrochemical Detection of Native and Aggregated ,-Synuclein Protein Involved in Parkinson's DiseaseELECTROANALYSIS, Issue 13-14 2004Michal Masa Abstract The aggregation of ,-synuclein, a 14,kDa protein, is involved in several human neurodegenerative disorders, including Parkinson's disease. We studied native and in vitro aggregated ,-synuclein by circular dichroism (CD), atomic force microscopy (AFM) and electrochemical methods. We used constant current chronopotentiometric stripping analysis (CPSA) to measure hydrogen evolution catalyzed by ,-synuclein (peak H) at hanging mercury drop electrodes (HMDE) and square-wave stripping voltammetry (SWSV) to monitor tyrosine oxidation at carbon paste electrodes (CPE). To decrease the volume of the analyte, most of the electrochemical measurements were performed by adsorptive transfer (medium exchange) from 3,6,,L drops of ,-synuclein samples. With both CPE and HMDE we observed changes in electrochemical responses of ,-synuclein corresponding to protein fibrillization detectable by CD, fluorescence and AFM. Aggregation-induced changes in peak H at HMDE were relatively large in strongly aggregated samples, suggesting that this electrochemical signal may find use in the analysis of early stages of ,-synuclein aggregation. This assumption was documented by marked changes in the peak H potential and height in samples withdrawn at the end of the lag and the beginning of the elongation phase. Native ,-synuclein can be detected down to subnanomolar concentrations by CPSA. [source] Dual CD system-modified MEEKC method for the determination of clemastine and its impuritiesELECTROPHORESIS, Issue 19 2010Serena Orlandini Abstract A dual system of CDs was used for the first time in MEEKC with the aim of determining clemastine and its three main related impurities in both drug substances and tablets. The addition of methyl-,-cyclodextrin and heptakis(2,6-di- O -methyl)-,-cyclodextrin to the microemulsion pseudo-stationary phase was essential to increase the resolving power of the system to obtain a baseline separation among the compounds. The best microemulsion composition was identified by mixture design and the effects of the factors concentrations of CDs and voltage were investigated by a response surface study applying a Central Composite Design. In both cases, Derringer's desirability function made it possible to find the global optimum, which corresponded to the following combination: microemulsion, 89.8% 10,mM borate buffer pH 9.2, 1.5% n -heptane and 8.7% of SDS/n -butanol in 1:2 ratio; 18,mM methyl-,-cyclodextrin, 38,mM heptakis(2,6-di- O -methyl)-,-cyclodextrin, 17,kV. By applying these conditions, the separation was completed in about 5.5,min. The method was validated following International Conference on Harmonisation guidelines and was applied to a real sample of clemastine tablets. [source] Determination of the binding constants of modafinil enantiomers with sulfated ,-cyclodextrin chiral selector by capillary electrophoresis using three different linear plotting methodsELECTROPHORESIS, Issue 17 2010Khaldun M. Al Azzam Abstract Binding constants for the enantiomers of modafinil with the negatively charged chiral selector sulfated-,-CD (S-,-CD) using CE technique is presented. The calculations of the binding constants employing three different linearization plots (double reciprocal, X -reciprocal and Y -reciprocal) were performed from the electrophoretic mobility values of modafinil enantiomers at different concentrations of S-,-CD in the BGE. The highest inclusion affinity of the modafinil enantiomers were observed for the S -enantiomer,S-,-CD complex, in agreement with the computational calculations performed previously. Binding constants for each enantiomer,S-,-CD complex at different temperatures, as well as thermodynamic parameters for binding, were calculated. Host,guest binding constants using the double reciprocal fit showed better linearity (r2>0.99) at all temperatures studied (15,30°C) and compared with the other two fit methods. The linear van't Hoff (15,30°C) plot obtained indicated that the thermodynamic parameters of complexation were temperature dependent for the enantiomers. [source] Analysis of amphetamine-type substances by capillary zone electrophoresis using capacitively coupled contactless conductivity detectionELECTROPHORESIS, Issue 15 2010Rochelle Epple Abstract CE with capacitively coupled contactless conductivity detection (C4D) was employed for the separation and detection of seven amphetamine analogues as well as amphetamine, dextroamphetamine, methamphetamine and 3,4-methylenedioxymethamphetamine. The separation electrolyte was 30,mM hydroxypropyl-,-cyclodextrin (HP,CD) in a 75,mM acetic acid+25,mM sodium acetate buffer adjusted to pH 4.55. Conductivity detection was compared with UV detection using this same electrolyte. Average detection limits for C4D and UV were 1.3 and 1.0,ppm, respectively. The effects of HP,CD concentration and BGE composition on the selectivity of the separation were also investigated. An illicit, street-grade sample of 3,4-methylenedioxymethamphetamine (Ecstasy) and a prescription dextroamphetamine tablet were also analysed. [source] Separation of propranolol enantiomers by CE using sulfated ,-CD derivatives in aqueous and non-aqueous electrolytes: Comparative CE and NMR study,ELECTROPHORESIS, Issue 9 2010Anne-Catherine Servais Abstract Separations using CE employing non-aqueous BGE are already as well established as separations in aqueous buffers. The separation mechanisms in achiral CE with non-aqueous BGEs are most likely similar to those in aqueous buffers. However, for the separation of enantiomers involving their interaction with chiral buffer additives, the interaction mechanisms might be very different in aqueous and non-aqueous BGEs. While the hypothesis regarding distinct mechanisms of enantiomer separations in aqueous and non-aqueous BGEs has been mentioned in several papers, no direct proof of this hypothesis has been reported to date. In the present study, the enantiomers of propranolol were resolved using CE in aqueous and non-aqueous methanolic BGEs with two single isomer sulfated derivatives of ,-CD, namely heptakis (2,3-diacetyl-6-sulfo)-,-CD and heptakis (2,3-dimethyl-6-sulfo)-,-CD. The enantiomer migration order of propranolol was inverted when an aqueous BGE was replaced with non-aqueous BGE in the case of heptakis (2,3-dimethyl-6-sulfo)-,-CD but remained the same in the case of heptakis (2,3-diacetyl-6-sulfo)-,-CD. The possible molecular mechanisms leading to this reversal of enantiomer migration order were studied by using nuclear overhauser effect spectroscopy in both aqueous and non-aqueous BGEs. [source] CE assay for simultaneous determination of charged and neutral impurities in dexamphetamine sulfate using a dual CD systemELECTROPHORESIS, Issue 9 2010Sudaporn Wongwan Abstract A CE assay for the simultaneous determination of charged and uncharged potential impurities (1S,2S -(+)-norpseudoephedrine, 1R,2S -(,)-norephedrine, phenylacetone and phenylacetone oxime) of dexamphetamine sulfate including the stereoisomer levoamphetamine was developed and validated. The optimized background electrolyte consisted of a 50,mM sodium phosphate buffer, pH 3.0, containing 80,mg/mL sulfobutylether-,-CD and 25,mg/mL sulfated ,-CD. Separations were performed in 40.2/35,cm, 50 ,m id fused-silica capillaries at a temperature of 20°C and an applied voltage of ,10,kV. 1R,2S -(,)-ephedrine was used as internal standard. The assay was validated in the range of 0.05,1.0% for the related substances and in the range of 0.05,5.0% for levoamphetamine. The LOD was 0.01,0.02% depending on the analyte. The assay also allowed the separation of the E,Z-stereoisomers of phenylacetone oxime. The effect of the degree of substitution of sulfobutylether-,-CD was investigated. In commercial samples of dexamphetamine sulfate between 3.2 and 3.7% of levoamphetamine were found. Furthermore, phenylacetone and phenylacetone oxime could be observed at the LOD, indicating the synthetic origin of the investigated samples. [source] Effect of urea on analyte complexation by 2,6-dimethyl-,-CD in peptide enantioseparations by CEELECTROPHORESIS, Issue 21 2009Manuela Hammitzsch-Wiedemann Abstract The aim of the present study was the investigation of the effect of urea on analyte complexation in CD-mediated separations of peptide enantiomers by CE in the pH range of about 2,5. pH-independent complexation and mobility parameters in the absence and presence of 2,M urea were obtained by three-dimensional, non-linear curve fitting of the effective analyte mobility as a function of pH and heptakis-(2,6-di- O -methyl)-,-CD concentration. Urea led to decreased binding strength of the CD towards the protonated and neutral analyte enantiomers as well as to decreased mobilities of the free analytes. In contrast, mobilities of the fully protonated enantiomer,CD complexes as well as the pKa values of the free and complexed analytes increased. The effect of urea on separation efficiency varied with pH and CD concentration. In the case of Ala-Tyr and Ala-Phe, separations improved in the presence of urea at pH 2.2. In contrast, separations were impaired by urea at pH 3.8 and low concentrations of the CD. Decreased separation efficiency was noted for Asp-PheOMe and Glu-PheNH2 at low CD concentrations when urea was added but separations improved at higher CD concentrations over the entire pH range studied. The effect of urea on analyte complexation appeared to be primarily non-stereoselective. Furthermore, the pH-dependent reversal of the enantiomer migration order observed for Ala-Tyr and Ala-Phe can be rationalized by the complexation and mobility parameters. [source] Use of coated capillaries for the electrophoretic separation of stereoisomers of a growth hormone secretagogueELECTROPHORESIS, Issue 21 2009Reine Nehmé Abstract The diastereoisomeric separation of peptidomimetics of hexarelin, a strong growth hormone secretagogue, in CE has been studied. Highly sulfated-,-CD was found to be an appropriate selector for the separation of the stereoisomers. However, non-repeatable analyses were obtained on bare fused silica capillary due to the progressive adsorption of the analytes on the capillary wall. Two types of polyelectrolyte coating agents were tested to prevent this phenomenon. Coating with neutral polyethylene oxide was found to be efficient but resulted in a very long analysis time (about 40,min). Coating with cationic poly(diallyldimethylammonium) chloride was found both to prevent analyte adsorption, reduce analysis time and alter separation selectivity. EOF measurement revealed that the highly sulfated-,-CDs were strongly adsorbed on the poly(diallyldimethylammonium) chloride coating surface yielding a stable strong cathodic EOF, which considerably reduced analysis time (about 12,min). Very good repeatability of analysis was obtained (RSDmigration time<1%). [source] Combined use of chiral ionic liquid and CD for MEKC: Part II.ELECTROPHORESIS, Issue 16 2009Determination of binding constants Abstract A competitive inhibition mechanism is proposed to investigate the interactions among 2,3,6-tri- O -methyl-,-CD (TM-,-CD), cationic ionic liquid type surfactants, N -undecenoxy-carbonyl- L -leucinol bromide (L -UCLB) and profens using affinity CE. The apparent binding constant of TM-,-CD to L -UCLB was estimated by nonlinear and linear plotting methods. The binding constants of one representative profen (e.g. fenoprofen) to TM-,-CD and L -UCLB were estimated by a secondary plotting approach. The R - and S -fenoprofens have different binding constant values, resulting in the enantioseparation due to the synergistic effect of the two chiral selectors, TM-,-CD and L -UCLB. [source] Improved simultaneous enantioseparation of ,-agonists in CE using ,-CD and ionic liquidsELECTROPHORESIS, Issue 6 2009Lu Huang Abstract In this study, approaches to improve chiral resolutions in simultaneous enantioseparation of ,-agonists by CE via a CD inclusion complexation modified with ionic liquids (ILs) are described. Different types of ILs, including tetraalkylammonium-based ILs, alkylimidazolium-based ILs and alkylpyridinium-based ILs, were examined and compared for controlling the EOF in order to improve resolutions of ,-agonists enantiomers. In this regard, tetraalkylammonium-based ILs were more effective because they could be used at much higher concentrations than other types of ILs. N -octylpyridinium hexafluorophosphate gave poor resolutions of ,-agonists enantiomers. In addition, when different ILs were mixed to use, they would present particular properties of their own. Moreover, the presence of ILs was essential in the chiral separations of (±) salbutamol, (±) cimaterol and (±) formoterol, which were reportedly not enantioseparated by using the buffer electrolytes containing only ,-CD as a chiral selector. [source] Fast derivatization of the non-protein amino acid ornithine with FITC using an ultrasound probe prior to enantiomeric determination in food supplements by EKCELECTROPHORESIS, Issue 6 2009Elena Domínguez-Vega Abstract An EKC method for the determination of ornithine (Orn) enantiomers has been developed after a fast pre-capillary derivatization with FITC. The derivatization step was needed to provide a chemical moiety to the Orn molecule, enabling a sensitive UV detection and the interaction with the CDs used as chiral selectors. To accelerate the derivatization reaction, an ultrasound probe was used. For the development of the chiral method, the influence of different experimental conditions (type and concentration of the chiral selector, temperature, and separation voltage) was investigated. Due to the anionic nature of the analyte (FITC-Orn), five neutral CDs were employed as chiral selectors. The native ,-CD showed the highest chiral separation power, observing that a low concentration of this CD (1,mM), using a working temperature of 25°C and a separation voltage of 20,kV, enabled to obtain the highest enantioresolution for Orn and its separation from other amino acids usually present in food supplements. After optimizing the method for the preconditioning of the capillary, the analytical characteristics of the chiral method were established. Linearity, LOD and LOQ, precision, and accuracy were evaluated previously to the determination of Orn enantiomers contained in ten commercial food supplements. No interferences from other amino acids present in these samples were observed. [source] Cyclodextrin-based nonaqueous electrokinetic chromatography with UV and mass spectrometric detection: Application to the impurity profiling of amiodarone,ELECTROPHORESIS, Issue 17 2008Roelof Mol Abstract The potential of nonaqueous electrokinetic chromatography (NAEKC) using cyclodextrins (CD) for the analysis of basic drugs and related compounds was evaluated. Both UV absorbance and mass spectrometric (MS) detection were employed. Addition of neutral CD to the NA background electrolyte did not significantly enhance the separation of a test mixture of basic drugs, and no change in selectivity was observed. In contrast, anionic single-isomer-sulfated CD strongly added to the selectivity of the NAEKC system inducing an improved resolution among the test compounds and increasing the migration time window. The applicability of the NAEKC system using anionic CD is demonstrated by the profiling of a sample of the drug amiodarone that had been stored for 1,year at room temperature. Amiodarone is poorly soluble in water. NAEKC-UV analysis indicated the presence of at least seven impurities in the amiodarone sample. In order to identify these compounds, the NAEKC system was coupled directly to electrospray ionization (ESI) ion-trap MS. The total of detected impurities increased to 12 due to the added sensitivity and selectivity of MS detection. Based on the acquired MS/MS data, three sample constituents could be identified as ,known' impurities (British Pharmacopoeia), whereas for three unknown impurities molecular structures could be proposed. Estimated limits of detection for amiodarone using the NAEKC method were 1,,g/mL with UV detection and 15,ng/mL with ESI-MS detection (full-scan). Based on relative responses, the impurity content of the stored drug substance was estimated to be 0.33 and 0.47% using NAEKC-UV and NAEKC-ESI-MS, respectively. [source] Simultaneous enantioseparation and sensitivity enhancement of basic drugs using large-volume sample stackingELECTROPHORESIS, Issue 19 2007Nerissa L. Deñola Abstract Simultaneous enantioseparation with sensitive detection of four basic drugs, namely methoxamine, metaproterenol, terbutaline and carvedilol, using a 20-,m ID capillary with native ,-CD as the chiral selector was demonstrated by the large-volume sample stacking method. The procedure included conventional sample loading either hydrodynamically or electrokinetically at longer injection times without polarity switching and EOF manipulation. In comparison to conventional injections, depending on the analyte, about several hundred- and a thousand-fold sensitivity enhancement was achieved with the hydrodynamic and the electrokinetic injections, respectively. The simple method developed was applied to the analysis of racemic analytes in serum samples and better recovery was achieved using hydrodynamic injection than electrokinetic injection. [source] Enantioselective analysis of pheniramine in urine by charged CD-mediated CZE provided with a fiber-based DAD and an on-line sample pretreatment by capillary ITPELECTROPHORESIS, Issue 15 2007Jozef Marák Abstract Application potentialities of CZE on-line coupled with capillary ITP and DAD to the identification and determination of trace concentration levels (,g/L) of pheniramine (PHM) enantiomers and their metabolites present in complex ionic matrices of biological origin (urine) are shown. An enhanced (enantio)selectivity of the CZE separation system obtained by the addition of carboxyethyl-,-CD (CE-,-CD) to the carrier electrolyte provided CZE conditions for a reliable identification of similar/identical DAD spectra of structurally related compounds (PHM enantiomers and their metabolites) in clinical urine samples differing in qualitative and quantitative composition of sample matrix constituents. A high sample loadability (a 30,,L sample injection volume), partial sample clean-up (removing macroconstituents from the sample), and preconcentration of the analytes in ITP stage resulted in the decrease of concentration LOD for PHM enantiomers in urine to 5.2 and 6.8,,g/L (2.2×10,8 and 2.8×10,8,mol/L), without using any sample pretreatment technique. The background correction and smoothing procedure applied to the raw DAD spectra provided analytically relevant DAD spectra of PHM enantiomers and their metabolites also when they were present in urine sample (30,,L injection volumes of ten-times diluted urine sample) at a 9×10,8,mol/L concentration. DAD spectra of PHM enantiomers present in urine samples matched their reference spectra with reasonable certainties. DAD spectra of PHM metabolites were compared with the reference spectra of PHM enantiomers and a good match was found which indicates the similarities in the structures of enantiomers and their metabolites detected in the urine samples. This fact allows performing the quantitative analyses of PHM metabolites in the urine samples by applying the calibration parameters of PHM enantiomers also for PHM metabolites and the results show the possibilities of using the ITP,CZE,DAD combination for the direct analysis of PHM enantiomers and/or their metabolites in urine without any sample pretreatment. ITP,CZE,DAD method with oppositely charged selector is suggested to use in clinical research as it provides favorable performance parameters including sensitivity, linearity, precision, recovery, and robustness with minimal demands on sample preparation. [source] Enantioselective analysis of ketamine and its metabolites in equine plasma and urine by CE with multiple isomer sulfated ,-CDELECTROPHORESIS, Issue 15 2007Regula Theurillat Abstract CE with multiple isomer sulfated ,-CD as the chiral selector was assessed for the simultaneous analysis of the enantiomers of ketamine and metabolites in extracts of equine plasma and urine. Different lots of the commercial chiral selector provided significant changes in enantiomeric ketamine separability, a fact that can be related to the manufacturing variability. A mixture of two lots was found to provide high-resolution separations and interference-free detection of the enantiomers of ketamine, norketamine, dehydronorketamine, and an incompletely identified hydroxylated metabolite of norketamine in liquid/liquid extracts of the two body fluids. Ketamine, norketamine, and dehydronorketamine could be unambiguously identified via HPLC fractionation of urinary extracts and using LC-MS and LC-MS/MS with 1,mmu mass discrimination. The CE assay was used to characterize the stereoselectivity of the compounds' enantiomers in the samples of five ponies anesthetized with isoflurane in oxygen and treated with intravenous continuous infusion of racemic ketamine. The concentrations of the ketamine enantiomers in plasma are equal, whereas the urinary amount of R -ketamine is larger than that of S -ketamine. Plasma and urine contain higher S - than R -norketamine levels and the mean S -/R -enantiomer ratios of dehydronorketamine in plasma and urine are lower than unity and similar. [source] Determination of sertraline and N -desmethylsertraline in human plasma by CE with LIF detectionELECTROPHORESIS, Issue 11 2007Alessandro Musenga Abstract A method has been developed for the analysis of the antidepressant drug sertraline together with its main metabolite N -desmethylsertraline (DMS) in human plasma. It is based on CE with LIF detection (,,=,488,nm). A SPE procedure is employed for biological sample pretreatment, followed by a derivatization step with FITC; reboxetine was the internal standard. The effect of CD, acetone and N -methyl- D -glucamine (GLC) as constituents of the BGE for analyte separation was investigated. The final BGE consisted of 20,mM carbonate buffer, pH,9.0, with 2.5,mM heptakis(2,6-di- O -methyl)-,-CD, 50,mM GLC and 20% v/v acetone. With 30,kV applied voltage, the electrophoretic run is completed in 7.5,min. Linearity was observed in the plasma concentration range from 3.0 to 500,ng/mL for sertraline and 4.0 to 500,ng/mL for DMS. Extraction yield was >97.1%, precision , expressed as RSD% , was <3.7, accuracy (recovery) was >95.6%. Due to its sensitivity and selectivity, the method was suited for the analysis of plasma samples from patients undergoing therapy with sertraline. [source] Enhanced electrophoretic resolution of monosulfate glycosaminoglycan disaccharide isomers on poly(methyl methacrylate) chipsELECTROPHORESIS, Issue 3 2007Yong Zhang Abstract To improve the separation of monosulfate glycosaminoglycan disaccharide isomers by microchip electrophoresis, we found that addition of 1,4-dioxane,(DO) dramatically improved analyte resolution, probably due to solvation effects. Methylcellulose,(MC) was tested for the ability to suppress EOF and analyte adsorption to the chip. To improve analyte resolution, buffer pH, ,-CD, and DO were systematically investigated. Fast separation was achieved by increasing the electric field strength, and field-amplified sample stacking occurred with increasing buffer concentrations. Therefore, based on our findings, we describe an efficient method for the separation of monosulfate and trisulfate unsaturated disaccharides (,Di-UA2S, ,Di-4S, ,Di-6S, and ,Di-triS) derivatized with 2-aminoacridone hydrochloride. A mixture of monosulfate disaccharide isomers (,Di-UA2S, ,Di-4S, and ,Di-6S) was baseline-separated within 75,s on a poly(methyl methacrylate) chip using a mixed buffer (DO/running buffer 57:43,v:v), 0.5% MC, pH,6.81, with an Esep of 558,V/cm. The theoretical plate was in the range of 5×105 to 1×106,m,1. [source] Determination of trace cationic impurities in butylmethylimidazolium-based ionic liquids: From transient to comprehensive single-capillary counterflow isotachophoresis-zone electrophoresisELECTROPHORESIS, Issue 23 2006Marek Urbánek Abstract Determination of impurities in ionic liquids (ILs) remains a difficult task. In this work, the hyphenation of isotachophoretic,(ITP) preconcentration to zone electrophoresis,(ZE) has been explored for the trace analysis of the cationic impurities Na+, Li+, and methylimidazolium (MI+) in butylmethylimidazolium (BMI+)-based ILs. Simultaneous detection of UV-transparent and UV-absorbing impurities was ensured by a BGE composed of creatinine-acetate buffer. To induce ITP, three different strategies were evaluated: (i),Sample self-stacking ensured by the addition of ammonium acetate (NH4Ac) to 25,50-fold diluted IL solution (transient ITP). (ii),Complete ITP-ZE separation performed in a single capillary: ITP was realized in discontinuous electrolytes comprising an 80,mM NH4Ac, 40,mM acetic acid, 30,mM ,-CD, pH,5.05, leading electrolyte,(LE) and a 10,mM creatinine, 10,mM acetic acid, pH,4.9, terminating electrolyte,(TE). To create the ZE stage, the ITP stack of analytes was moved back toward the capillary inlet by pressure and simultaneously the capillary was filled with the BGE. This protocol made it possible to accommodate a 2.5-times diluted IL sample. (iii),Complete counterflow ITP-ZE with continuous electrokinetic sample supply: the ITP stage was performed in a capillary filled with a 150,mM NH4Ac, 75,mM acetic acid, 30,mM ,-CD, pH,5.0 LE, with 40-times diluted IL at the capillary inlet. BMI+ from IL acts as the terminating ion. The LODs reached in this latter case were at the 10 and 1,ppb levels for MI+ and Li+ in diluted IL matrix, respectively. [source] | |||||||||||||||||||||||||||||||||||||||||||||||||