Interaction of nickel with 4-(2'-benzothiazolylazo) salicylic acid (BTAS) and simultaneous first-derivative spectrophotometric determination of nickel(II) and iron(III).

The solution properties of nickel complex with 4-(2'-benzo-thiazolylazo) salicylic acid (BTAS) have been studied by zero-order absorption spectrophotometry in 40% (v/v) ethanol at 20 degrees C and an ionic strength of 0.1 mol dm(-3) (KNO(3)). The equilibria that exist in solution were established and the basic characteristics of complexes formed were determined. A new direct spectrophotometric method for the determination of trace amounts of the nickel is proposed based on the formation of the Ni (BTAS) complex at pH 7.0. The absorption maximum, molar absorbtivity, and Sandell's sensitivity of 1:1 (M:L) complex are 525 nm, 0.6 x 10(4) l mol(-1) cm(-1) and 2.824 x 10(-9) microg cm(-2), respectively. The use of first-derivative spectrophotometry eliminates the interference of iron and enables the simultaneous determination of nickel and iron using BTAS. Quantitative determination of Ni(II) and Fe(III) is possible in the range (0.59-7.08) and (2.1-8.4) microg ml(-1), respectively with a relative standard deviation of 0.5%. The proposed method has been successfully applied to the simultaneous spectrophotometric determination of nickel and iron in steel alloys and aluminum alloys.

Electronystagmography: how helpful is it?

Two hundred and sixty patients tested with electronystagmography (ENG) for evaluation of complaints of disequilibrium were the representative sample for this study. As all new dizzy patients currently receive an ENG, the goal of this project was to determine how much an ENG adds to the diagnostic acumen, and which patients really needed an ENG in order to maximize efficiency and minimize patient cost. Results indicate the suspected diagnosis prior to ENG is assisted by its use only when the cause is thought to be central or is uncertain. The percentage of unknown causes of disequilibrium decreased from 34.2 to 13.8 per cent and the percentage of central causes increased from 13.1 to 23.1 per cent. Electronystagmography does not significantly aid in the diagnosis of peripheral lesions except as confirmation. Specific findings and recommendations are discussed.

Evoked potentials and electroencephalography in stuttering.

The study was aimed at finding what factors in evoked potentials and EEG related to stuttering in subjects 6-25 years of age. Thirty-seven subjects who stuttered and 25 nonstuttering subjects, matched for age, sex and education, were evaluated employing visual evoked potentials, auditory evoked potentials, event-related potentials (P(300)), WISC-(IQ), and electroencephalography. A significant reduction of amplitude of P(100) of visual evoked potentials was found in stutterers with a significant prolongation of wave latencies I, III, V and interpeak latencies I-III and I-V in brainstem auditory evoked potentials. No significant abnormalities were recorded in P(200), N(200) and P(300) of event-related potentials in stutterers compared with the control group. The dominant EEG rhythm was slower in stutterers with a significant interhemispheric asymmetry compared with the control group. Fifty-four percent of the stutterers had pathological EEG. Epileptiform activities were recorded in 16.2% of stuttering subjects. Focal left temporal spike activity was recorded in 5.4% of stuttering subjects. The findings of this study point to a possible role of an organic etiopathogenesis of stuttering.

Value of otoacoustic emission in monitoring hearing acuity in chronic renal failure patients.

To evaluate hearing acuity in chronic renal failure (CRF), we studied 48 patients of age less than 40 year as well as 15 years age and sex matched healthy subjects as controls by using the conventional pure-tone audiometry and evoked otoacoustic emission (TEOAE). Twenty-two of the study patients were treated conservatively and 26 patients by regular hemodialysis (HD). The dialyzed patients were further classified according to the duration of HD into 14 patients dialyzed for < 1 year and 12 patients dialyzed for> 1-year. TEOAE was applied only for patients proved to have normal pure tone thresholds. Sensorineural hearing loss was more in CRF patients treated conservatively than in those treated by dialysis (22.7%) and 15.3%, respectively), but the difference was not statistically significant. TEOAE was more sensitive than pure-tone audiometry in detecting sensorineural hearing loss in these patients (27.2% Vs 19.2%, respectively) and in the whole reproducibility of the test. However there were no significant statistical differences in the CRF subgroups and the controls. Furthermore, there was no correlation between TEOAE parameters and serum urea and creatinine. In conclusion, hearing acuity was found to be impaired in chronic renal failure patients whether treated conservatively or hemodialyzed. The transient evoked otoacoustic emission is more sensitive than the conventional pure-tone audiometry for evaluation of hearing acuity in this setting. Although the parameters of TEOAE seem to be better in hemodialyzed than in conservatively treated patients, but it did not reach statistical significance.

Complexation equilibria and spectrophotometric determination of iron(III) with 1-amino-4-hydroxyanthraquinone.

The complex equilibria of iron(III) with 1-amino-4-hydroxyanthraquinone (AMHA) were studied spectrophotometrically in 40% (v/v) ethanol and an ionic strength of 0.1M (NaClO(4)). The complexation reactions were demonstrated and characterized using graphical logarithmic analysis of the absorbance-pH graphs. A simple, rapid, selective and sensitive method for the spectrophotometric determination of trace amounts of Fe(III) is developed based on the formation of Fe(AMHA) complex at pH 2.5 (lambda(max) = 640 nm, epsilon approximately = 2.1 x 10(4) L. mol(-1) . cm(-1)) in the presence of a large number of foreign ions. Interferences caused by palladium(II) was masked by the addition of cyanide ions. The method has been applied to the determination of iron in some synthetic samples and polymetallic iron ores.

Spectrophotometric study of the complexation equilibria of iron(III) with 3-hydroxypicolinic acid and determination of iron in pharmaceutical preparations.

The complexation equilibria of iron(III) with 3-hydroxypicolinic acid (hypa) have been studied spectrophotometrically in 40% (v/v) ethanol-water medium at 25 degrees C and an ionic strength of 0.1 M NaClO4. The equilibria occurring in solution were established and the basic characteristics of the complexes formed were determined. The spectral study of the reaction solutions containing equimolar concentrations or an excess of one component in the pH range 1.5 to 10.5 gave the evidence for the formation of [FeLH]2+, [FeL]+ and [FeL2]- complex species, depending upon the pH of the medium (LH2 symbolising the molecular form of hypa). The possible complex transitions that occur in solution were demonstrated using graphical and logarithmic analysis of the absorbance-pH graphs. A simple, rapid, sensitive and selective method for spectrophotometric determination of trace levels of iron(III) was proposed based on the formation of Fe(hypa)2 complex at pH 5.5 (lambda = 440 nm, epsilon = 1.5 x 10(4) dm3 mol-1 cm-1). The interference of a large number of foreign ions was investigated. The method has been applied successfully to the analysis of multivitamin and mineral preparations containing iron.