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Suspected Endothelial Pencil Graphite Deposition  [PDF]
Adem Gül,Ertu?rul Can,?zlem E?ki Yücel,Leyla Niyaz,Halil ?brahim Akgün,Nur?en Ar?türk
Case Reports in Ophthalmological Medicine , 2013, DOI: 10.1155/2013/369374
Abstract: A 14-year-old male patient had an ocular trauma with a pencil. Biomicroscopic examination revealed a broken part of pencil into the cornea. Foreign body removal and corneal wound closure were performed in the same day. After corneal repair, there was a grade 4+ anterior chamber reaction just like in preoperative examination. Dilated examination showed a very small piece broken tip of pencil on the upper nasal quadrant of the lens. A small and linear deposition was also seen on endothelial surface. Endothelial deposition and foreign body disappeared with intensive topical steroid treatment. 1. Introduction Ocular trauma is not a rare condition which is mostly seen in children and it occupies an important area in ophthalmologic diseases that may result in some degree of vision loss [1]. Foreign bodies can be seen in anterior chamber, lens, iris, vitreous chamber, and retina after trauma. The most seen area of the foreign body is anterior chamber (15%), reported by Han et al. [2]. Although several etiologic factors have been identified, the most common ones are metal, stone, and wooden pieces. Pencil is a very rare etiologic agent [3]. As it is known, pencil is composed of wooden and lead parts. Graphite, which is the major constituent of pencil lead, has been reported to remain inert in the eye for a long time. When an injury to the globe with a pencil tip happens, there may be a deposition of the graphite that may remain inert or reactive, discussed by Honda and Asayama [4]. In this paper, a reactive foreign body will be presented and a deposition seen on endothelial surface will be discussed. 2. Case A 14-year-old male patient was admitted to our hospital with a complaint of decreased vision in the right eye after an ocular trauma with a pencil. Patient was admitted to the hospital, nine hours after trauma. Visual acuity was finger count from two meters in the right eye and 10/10 in the left eye. Slit lamp examination revealed a corneal perforation and a part of pencil in the edges of the wound on the upper temporal region between 9 and 10 o’clock alignment in the right eye. There were no pathologic findings in the left eye. There was a grade 4+ anterior chamber reaction and a membrane formation within the perforated area. The patient was hospitalized and foreign body removal (Figure 1(a)) and corneal wound closure with nylon sutures were performed in the same day. Figure 1: (a) Removed foreign body; (b) endothelial deposits; (c) graphite on the lens in first day; (d) corneal deposits were resolved. Written informed consent was obtained from the patient
Asymptomatic Intracorneal Graphite Deposits following Graphite Pencil Injury
Swetha Sara Philip,Deepa John,Sheeja Susan John
Case Reports in Ophthalmological Medicine , 2012, DOI: 10.1155/2012/720201
Abstract: Reports of graphite pencil lead injuries to the eye are rare. Although graphite is considered to remain inert in the eye, it has been known to cause severe inflammation and damage to ocular structures. We report a case of a 12-year-old girl with intracorneal graphite foreign bodies following a graphite pencil injury.
Asymptomatic Intracorneal Graphite Deposits following Graphite Pencil Injury  [PDF]
Swetha Sara Philip,Deepa John,Sheeja Susan John
Case Reports in Ophthalmological Medicine , 2012, DOI: 10.1155/2012/720201
Abstract: Reports of graphite pencil lead injuries to the eye are rare. Although graphite is considered to remain inert in the eye, it has been known to cause severe inflammation and damage to ocular structures. We report a case of a 12-year-old girl with intracorneal graphite foreign bodies following a graphite pencil injury. 1. Introduction Ocular injuries with graphite pencil lead are rare. There is only one case report of intracorneal graphite foreign bodies following graphite pencil lead injury in literature to date [1]. We report a case of a 12-year-old girl with intracorneal graphite foreign bodies, which remained inert in the eye for the past three years. 2. Case Report A 12-year-old girl came to our outpatient clinic for a routine ophthalmological checkup. She had been using glasses for the past three years. She did not complain of any other problems in her eyes. On examination, her best corrected visual acuity (BCVA) was found to be 6/6?J1 with myopic astigmatism in both eyes. Examination of the anterior segment of the right eye showed a linear anterior stromal corneal scar, which was located at the inferior pupillary margin. The scar measured about 4.5?mm and was studded with refractile particles along its entire length (Figure 1). There was no evidence of any damage to any intraocular structures. There was no evidence of past or present inflammation in the eye. The left eye was normal. Figure 1: Graphite particles seen within the corneal stroma of the right eye. When questioned regarding any past ocular injury, the parents told us that the patient had been accidentally poked in the right eye with a graphite pencil about three years ago. There was mild redness and pain in the eye soon after the injury. This was treated with some topical antibiotics and lubricants. The symptoms resolved with this treatment and she has been entirely asymptomatic to date. Since there was no evidence of active inflammation or progressive damage to the ocular structures, we decided against any further intervention. The patient is currently on followup. 3. Discussion Graphite pencils are made of graphite and clay, mixed with animal oils and fats, with a wooden surround [2]. Although graphite pencils are universally used in classrooms and homes across the world by young children, there are not many reports of injuries to the eye and adnexa with these pencils [3–8]. In the reported cases of ocular injury with graphite pencil lead, the commonly injured sites are the eyelids and orbit [3, 4]. This could be due to the fact that when an object is brought close to the eye, there is
Determination of Dopamine in Presence of Uric Acid at Poly (Eriochrome Black t) Film Modified Graphite Pencil Electrode  [PDF]
Umesh Chandra, B. E. Kumara Swamy, Ongera Gilbert, Sathish Reddy, B. S. Sherigara
American Journal of Analytical Chemistry (AJAC) , 2011, DOI: 10.4236/ajac.2011.22032
Abstract: A simple commercial graphite pencil electrode was used to investigate the electrochemical oxidation of dopamine. The electropolymerised film of eriochrome black t was prepared on the surface of graphite pencil electrode by using cyclic voltammetry technique. The prepared electrode exhibits an excellent electrocatalytical activity towards the determination of dopamine. The effects of concentration, pH and scan rate were investigated. Simultaneous detection of dopamine and uric acid was investigated by using both cyclic voltammetric and differential pulse voltammetry technique. The modified electrode was also used for the detection of dopamine in injection.
Determination of paracetamol at a graphite-polyurethane composite electrode as an amperometric flow detector
Cervini, Priscila;Cavalheiro, éder Tadeu Gomes;
Journal of the Brazilian Chemical Society , 2008, DOI: 10.1590/S0103-50532008000500005
Abstract: a bare graphite-polyurethane composite was evaluated as an amperometric flow injection detector in the determination of paracetamol (apap) in pharmaceutical formulations. a linear analytical curve was observed in the 5.00 x 10-5 to 5.00 x 10-3 mol l-1 range with a minimum detectable net concentration of 18.9 μmol l-1 and 180 determinations h-1, after optimization of parameters such as the detection potential, sample loop volume, and carrier solution flow rate. interference of ascorbic acid was observed, however, it was possible overcome the interference, reaching results that agreed with hplc within 95% confidence level. these results showed that the graphite-polyurethane composite can be used as an amperometric detector for flow analysis in the determination of apap.
Development of an amperometric enzyme electrode based on poly(o-phenylenediamine) for the determination of total cholesterol in serum
Zeybek, Derya Koyuncu;Zeybek, Bülent;Pekmez, Nuran ?z?i?ek;Pekyard?mc?, ?ule;K?l??, Esma;
Journal of the Brazilian Chemical Society , 2012, DOI: 10.1590/S0103-50532012001200011
Abstract: a polymer-based amperometric enzyme electrode (pt/popd/chox) was prepared for the amperometric detection of free cholesterol. firstly, poly(o-phenylenediamine) (popd) polymer film was prepared in acetonitrile-water medium containing o-phenylenediamine (opd) monomer and (±)-10-camphorsulfonic acid (hcsa) on pt electrode by the use of cyclic voltammetry technique. cholesterol oxidase (chox) enzyme was immobilized onto pt/popd electrode surface. the determination of cholesterol was performed via monitoring of the oxidation current of enzymatically produced h2o2 at +0.7 v vs. ag/agcl. optimum buffer concentration, ph and working temperature were found as 0.05 mol l-1, 7.5 and 40 oc, respectively. the working range of enzyme electrode to cholesterol was 9.8 × 10-3-11 μmol l-1 and response time 150 s. the effects of possible interferences present in serum samples on response of enzyme electrode were examined. the determination of total cholesterol in serum samples was performed by using proposed pt/popd/chox enzyme electrode and results were in good agreement with those obtained by spectrophotometric method.
Label-Free Electrochemical Detection of the Specific Oligonucleotide Sequence of Dengue Virus Type 1 on Pencil Graphite Electrodes  [PDF]
Elaine Souza,Gustavo Nascimento,Nataly Santana,Danielly Ferreira,Manoel Lima,Edna Natividade,Danyelly Martins,José Lima-Filho
Sensors , 2011, DOI: 10.3390/s110605616
Abstract: A biosensor that relies on the adsorption immobilization of the 18-mer single-stranded nucleic acid related to dengue virus gene 1 on activated pencil graphite was developed. Hybridization between the probe and its complementary oligonucleotides (the target) was investigated by monitoring guanine oxidation by differential pulse voltammetry (DPV). The pencil graphite electrode was made of ordinary pencil lead (type 4B). The polished surface of the working electrode was activated by applying a potential of 1.8 V for 5 min. Afterward, the dengue oligonucleotides probe was immobilized on the activated electrode by applying 0.5 V to the electrode in 0.5 M acetate buffer (pH 5.0) for 5 min. The hybridization process was carried out by incubating at the annealing temperature of the oligonucleotides. A time of five minutes and concentration of 1 μM were found to be the optimal conditions for probe immobilization. The electrochemical detection of annealing between the DNA probe (TS-1P) immobilized on the modified electrode, and the target (TS-1T) was achieved. The target could be quantified in a range from 1 to 40 nM with good linearity and a detection limit of 0.92 nM. The specificity of the electrochemical biosensor was tested using non-complementary sequences of dengue virus 2 and 3.
Electrochemical Preparation of a Molecularly Imprinted Polypyrrole-modified Pencil Graphite Electrode for Determination of Ascorbic Acid  [PDF]
Levent ?zcan,Mutlu Sahin,Yücel Sahin
Sensors , 2008, DOI: 10.3390/s8095792
Abstract: A molecularly imprinted polymer (MIP) polypyrrole (PPy)-based film was fabricated for the determination of ascorbic acid. The film was prepared by incorporation of a template molecule (ascorbic acid) during the electropolymerization of pyrrole onto a pencil graphite electrode (PGE) in aqueous solution using a cyclic voltammetry method. The performance of the imprinted and non-imprinted (NIP) films was evaluated by differential pulse voltammetry (DPV). The effect of pH, monomer and template concentrations, electropolymerization cycles and interferents on the performance of the MIP electrode was investigated and optimized. The molecularly imprinted film exhibited a high selectivity and sensitivity toward ascorbic acid. The DPV peak current showed a linear dependence on the ascorbic acid concentration and a linear calibration curve was obtained in the range of 0.25 to 7.0 mM of ascorbic acid with a correlation coefficient of 0.9946. The detection limit (3σ) was determined as 7.4x10-5 M (S/N=3). The molecularly-imprinted polypyrrole-modified pencil graphite electrode showed a stable and reproducible response, without any influence of interferents commonly existing in pharmaceutical samples. The proposed method is simple and quick. The PPy electrodes have a low response time, good mechanical stability and are disposable simple to construct.
Determination of 5-aminosalicylic acid in pharmaceutical formulations by square wave voltammetry at pencil graphite electrodes
Uliana, Carolina V.;Yamanaka, Hideko;Garbellini, Gustavo S.;Salazar-Banda, Giancarlo R.;
Química Nova , 2010, DOI: 10.1590/S0100-40422010000400036
Abstract: an analytical method for the determination of the anti-inflammatory drug 5-aminosalicylic acid (5-asa) in pharmaceutical formulations using square wave voltammetry at pencil graphite electrodes was developed. after the optimization of the experimental conditions, calibration curves were obtained in the linear concentration range from 9.78 × 10-7 to 7.25 × 10-5 mol l-1 resulting in a limit of detection of 2.12 ± 0.05 x 10-8 mol l-1. statistical tests showed that the concentrations of 5-asa in commercial tablets and enemas obtained with the proposed voltammetric method agreed with hplc values at a 95% confidence level.
Fabricating an Amperometric Cholesterol Biosensor by a Covalent Linkage between Poly(3-thiopheneacetic acid) and Cholesterol Oxidase  [PDF]
Po-Chin Nien,Po-Yen Chen,Kuo-Chuan Ho
Sensors , 2009, DOI: 10.3390/s90301794
Abstract: In this study, use of the covalent enzyme immobilization method was proposed to attach cholesterol oxidase (ChO) on a conducting polymer, poly(3-thiopheneacetic acid), [poly(3-TPAA)]. Three red-orange poly(3-TPAA) films, named electrodes A, B and C, were electropolymerized on a platinum electrode by applying a constant current of 1.5 mA, for 5, 20 and 100 s, respectively. Further, 1-ethyl-3-(3-dimethylamiopropyl)carbodiimide hydrochloride (EDC?HCl) and N-hydroxysuccinimide (NHS) were used to activate the free carboxylic groups of the conducting polymer. Afterwards, the amino groups of the cholesterol oxidase were linked on the activated groups to form peptide bonds. The best sensitivity obtained for electrode B is 4.49 mA M-1 cm-2,with a linear concentration ranging from 0 to 8 mM, which is suitable for the analysis of cholesterol in humans. The response time (t95) is between 70 and 90 s and the limit of detection is 0.42 mM, based on the signal to noise ratio equal to 3. The interference of species such as ascorbic acid and uric acid increased to 5.2 and 10.3% of the original current response, respectively, based on the current response of cholesterol (100%). With respect to the long-term stability, the sensing response retains 88% of the original current after 13 days.
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