ABSTRACT
The environmental organic pollutant of di-2-ethylhexy phthalate ( DEHP ) was analyzed by extractive electrospray ionization mass spectrometry ( EESI-MS ). Effect of some important experimental conditions were investigated systematically, including the electrospray voltage, temperature of ion-transport tube, sample injection rate and extractant composition. Under the optimal conditions, a method for rapid detection of DEHP in water sample was established. DEHP levels in different samples with complex matrixes were measured, including landfill leachate, urban sewage and lake water. The results showed that DEHP in water samples could be ionized by EESI source and obtained the molecule ion (m/ z 391. 28) at the positive detection mode, and then CID experiment were performed to obtain the secondary fragment ions m/ z 279. 26, 167. 12 and 149. 11. The intensity of characteristic peak m/ z 149. 11 possessed a good linearity with the concentration of DEHP in the range of 5-1000 μg / L with the correlation coefficient of R2 = 0. 9991, and the detection limit (LOD) of 0. 21 μg / L. The recoveries of DEHP at three spiked levels (8, 80, 400 μg / L) were 96. 2％ - 111. 2％ , with RSDs of 5. 6％ - 11. 8％ . With the developed EESI-MS method, the concentrations of DEHP in landfill leachate, urban sewage and Yan lake water were 556. 5, 275. 3 and 37. 8 μg / L, respectively. The EESI-MS method possessed many advantages such as no requirement of sample pretreatment, fast analysis speed ( about 3 min per sample), simple operation and high sensitivity, thus providing a new mass spectrometric method for rapid detection of phthalate esters.
ABSTRACT
<p><b>OBJECTIVE</b>To identify clinical features and diagnostic tests that would alert the otolaryngologist to consider myasthenia gravis (MG) in the differential diagnosis of dysphonia, we reviewed the clinical characteristics of MG whose initial symptom is dysphonia.</p><p><b>METHODS</b>31 patients who presented with dysphonia as their initial and primary complaint are reported, their symptoms and signs are observed and analyzed.</p><p><b>RESULTS</b>Patients with dysphonia as their initial symptom of MG may complain of vocal fatigue, difficulty sustaining or projecting their voices, breathy voice or intermittent hoarseness. These symptoms are characterized by fluctuating weakness and abnormal fatigability. Flexible fibroendoscopic examination revealed that patients had incomplete adduction of the vocal folds, fatigue of the tensors of the vocal fold, incomplete glottic closure, vocal cord paralysis, saliva pooling over the bilateral or unilateral pyriform sinus. Neostigmine test revealed dramatic improvement in all patients. Serum levels of anti-Ach-R antibodies were tested in 19 cases, only 5 cases were abnormality. All patients had improved after treatment</p><p><b>CONCLUSIONS</b>Voice changes can be the first sign of early MG. Based on fluctuating weakness or weak voice at the end of the day, a positive neostigmine test, significantly higher circulating antibody to acetylcholine receptor, a diagnosis of MG could definitively be made.</p>