Determination of Zn in high-purity GaAs with neutron activation analysis
Neutron activation analysis was used to analyse Zn concentrations in high-purity GaAs. A combination of chemical separation of the neutron-induced 65Zn from the GaAs-matrix with anion-exchange chromatography and ultra low-level gamma-ray spectrometry in an underground laboratory was applied. Zn concentration ranged from 2.1 to 51 ng g(-1), and detection limits from 0.018 to 0.059 ng g(-1) were obtained.
Raman spectroscopic study of residual acceptors in semi‐insulating bulk GaAs
Electronic Raman scattering (ERS) has been used to study residual shallow acceptors in undoped semi‐insulating (SI) GaAs grown by the liquid‐encapsulated Czochralski technique. The dispersion of the cross section for ERS of shallow acceptors, as well as its absolute value, has been measured. It is shown that ERS allows a quantitative analysis of residual shallow acceptors in SI GaAs. Calibration factors for C and Zn acceptors are given. The detection limit of ERS is determined to ∼5×1014 cm−3 for 500‐μm‐thick standard wafers. Spatially resolved measurements show a systematic variation of the residual acceptor concentration across 2‐in. GaAs wafers.
HPLC determination of chlorhexidine gluconate and p-chloroaniline in topical ointment.
A novel fast isocratic reversed-phase HPLC method for simultaneous determination of chlorhexidine and its degradation product p-chloroaniline was developed. Zorbax SB Phenyl column (75 mm x 4.6 mm, 3.5 microm) was used for the separation. Mobile phase composed of acetonitrile and buffer solution of 0.08 M sodium phosphate monobasic containing 5 ml of triethylamine (0.5%) and adjust with 85% phosphoric acid to pH 3.0 in ratio 35:65 (v/v) pumped isocratically at flow rate 0.6 ml min(-1) was used. UV detection was performed at 239 nm, the total analysis time was about 10 min. The method is suitable for practical routine analysis of topical ointment in the quality control laboratory.