Yu. I. Turkin

Selective determination of lead on the basis of spectral phase effects

The selective of optimal mechanisms of spectral phase effects and the modulation frequency and temperature of the radiation source to achieve the best limits of detection of lead in air were studied. A block diagram of the experimental setup is shown. Relations of phase characteristics to spectral characteristics were presented for the 283-nm Pb resonance line and results of calibration of an experimental prototype of a selective analyzer for lead vapors in air are given. Results obtained for the modulation frequencies 1-15 and 400 kHz are presented. It is shown that selective determination of lead in air is possible and a procedure for its optimization is given.

LIGHT SOURCE WITH A COOLED HOLLOW CATHODE FOR EXCITATION OF SPECTRA OF MONOLITHIC DIELECTRIC SAMPLES

In addition to its use in isotopic spectral analysis [i] and high-revolution spectroscopy [2], a discharge in a cooled hollow cathode is used even more for high-resolution spectroscopy in elemental analysis of material [3]. In these experiments samples have been employed which differ widely in their structure, aggregation state, and in the chemical state of the sample. As found from experience with cooled hollow cathodes in steady-state work, the sputtering and spectral excitation of the object analyzed depends significantly on its chemical state [4]. In the analysis of metallic samples, the emission spectrum stabilizes almost immediately after the discharge begins. For the excitation of spectra of samples which are chemical compounds it is usually necessary to run the discharge for at least 30 min in order to obtain a stable emission spectrum intensity.

Spectral analysis with an interferometer

Spec t ra l ana lys i s with an i n t e r f e r o m e t e r has been used to i n c r e a s e the spec i f ic i ty f ac to r in f lame photomet ry [1] and a lso to e l imina te the influence of th i rd components and uncontrol led lo s ses in the c h e m i cal en r ichment of the spec imen on the r e su l t s of the ana lys i s [2, 3]. When a spec t rog raph or monoehro m a t o r is c r o s s e d with a F a b r y P e r o t i n t e r f e r o m e t e r there is an i nc rea se in the ra t io of the luminosi ty of the line spec t rum to the continuous spec t rum [4, 5]. The luminosi ty of the line spec t rum usual ly changes l i t t le in the p r o c e s s . This fea ture can be used to i n c r e a s e t h e r e l a t ive and absolute sens i t iv i ty and accu racy of the ana ly s i s . We should a lso expect an inc rease in the absolute sens i t iv i ty when use is made of an i n t e r f o r o m e t e r , c r o s s e d with a s p e c t r o g r a p h of medium d i spe r s ion , re la t ive to that for p rocedure s requ i r ing the use of long-focus spec t rog raphs with high d i s p e r s i o n (e.g., the DFS-13 ins t rument) .