6Q 7.

8.

Y. Naruse et al., Ibid., 47-49. Y. Naruse et al., Ibid., NS-27, 252-257 (1980). I. Lacer et al., Ibid., NS-28, 161-166 (1981).

LASER MASS-SPECTROMETRIC MEDICAL MICROANALYSIS A. A. Komleva, N. E. Benyaev, and I. M. Aref'ev

UDC 615.471.03:[616.633+614.7]-074+ 615.9.074]:543.42.062.063

Various physicochemical methods -- spectrophotometric, optical emission flurometric, etc. -- are presently used in medicine and biology for microanalysis of the elemental composition of biomedical objects [i0]. For conducting the analysis the method is generally selected on the basis of a number of criteria: sensitivity, accuracy, selectivity, etc. Preparation of the samples and standardizing are important stages in obtaining quantitative results. For multicomponent biomedical specimens standardization and quantitative interpretation of the results cause considerable difficulties owing to the specific characteristics of biological systems and absence of suitable standard specimens. Since the concentrations of the investigated elements in the sample are small, when creating an internal standard an addition at the level of concentration of the trace element in the sample leads to large errors [ii]. Therefore, for quantitative measurements of the microcomposition of biomedical specimens a method is needed which would permit conducting the analysis with a high sensitivity without the use of standards, Works on a standardless microanalysis of solid by means of a laser mass spectrometer have recently appeared in the literature [12]. Standardlessanalysis uses the fact that as a result of the interaction of laser radiation with a power density of more than 2 ×109 W/cm 2 with the surface of the sample, fractionless vaporization of the material and ionization of the vaporization products occur [8]. In this case a correspondence of the ion component recorded on the detector to the composition of the sample being analyzed is achieved [7]. Figure 1 shows the ion-optical scheme of the EMAL-2 laser dobule-focusing energy-mass analyzer [5]. The beam of the laser 4 operating in a Q switched mode is focused on the object 5 by means of optical system 1-3, 6, 7. The laser radiation at the site of interaction with the object causes vaporization and ionization of the vapors of the investigated substance. The plasma forming, having reached the grid of the focusing system 8, 9, breaks down into ion and electron components. The ions are focused on the object slit i0 and accelerated by the electric field. Passing through the main slit i0 and e-slit ii, the parallel beam strikes spherical electrostatic analyzer 12, where focusing of the ions according to energies occurs. The focused ions, passing through system of slits 13, 14, strike the magnetic analyzer 15~

~\

3v

I

4

10

I

II

B

Fig. i.

Ion-optical scheme of the EMAL-2 laser energy-mass analyzer.

All-Union Scientific-Research and Testing Institute of Biomedical Engineering, Moscow. Translated from Meditsinskaya Tekhnika, No. i, pp. 25-28, January-February, 1985. Original article submitted July i0, 1984.

0006-3398/85/1901-0011509.50

© 1985 Plenum Publishing Corporation

Ii

where the ions are distributed according to masses and then recorded on photographic film 16. The design characteristics of the instrument permit conducting local analysis at a prescribed point in the interval 50-100 ~m with integration over the depth or in the scanning band; layerby-layer local line analysis to a depth of 2-500 ~m; and simultaneous analysis of the entire composition with respect to all elements of the periodic table [6]. The error of the microanalysis is 30% without the use of standards. The resolving power of the instrument is 2500, the range of recordable masses 1-500, the concentration sensitivity 10 -7 at.%, the absolute sensitivity 10 -12 g. The EMAL-2 energy-mass analyzer was tested for the purpose of investigating the possibilities of a microanalysis of the elemental composition of biomedical samples. The tests were conducted for solving problems of hygiene and sanitation, monitoring environmental pollution, toxicology, and forensic medicine. In thefield of hygiene the laser mass-spectrometric method of elemental analysis was used for studying the development of occupational diseases in workers of industrial plants using laser technology for processing articles and workers of the mining industry. As is known, the majority of industrial aerosols, the prolonged effect of which on workers can lead to changes in the state of health and to the development of occupational diseases, has a complex chemical composition. The degree of harmfulness of individual components of industrial dust for workers has been inadequately studied, and in a hygienic assessment the reliability of the prediction of the harmful effect of dust will in many respects depend on the completeness of the data on the elemental composition and distribution of the components in relation to the disperse composition of dust. For analyzing dust samples by the mass-spectrometric method, techniques were developed for preparing samples by their precipitation on organic filters under conditions corresponding to the conditions of the work zones. The quantitative results of the elemental analysis of aerosols showed a good agreement with the results obtained in parallel determinations of the same samples by other methods [2]. The laser mass-spectrometric method was used for a comparative evaluation of the elemental composition of the acting dust and dust altered i n t h e organism and the response of the organism to an aggressive factor - d u s t ....was studied. An investigation of the distribution of elements in various dust fractions (respirable, coarse, total) made it possible to determine the range of toxic elementssettling in individual parts of the respiratory tract. For the first time hy means of the laser mass-spectrometric method tissues were analyzed in a native form without freeing from the organic part and the development of pneumoconiosis was studied on the basis of the change in the elemental composition of the tissue (22 elements were analyzed). Figure 2 shows a typical photogram of the mass spectrum of 0 0

% ~7 Cl

/7

M,g I zf M9

17 18/820

28 Z 4 ~ 2 6 Z T ~ 3 0 3 1 ~ Z ~ 3 5 37 ~ I

~

~M

Fig. 2. Photogram of the mass spectrum of liver tissue obtained in an elemental analysis on the EMAL-2 instrument (a fragment of the mass spectrum).

12

i u n a r m i i i

iii

I_.., L~ L. ~

c /~ o

i m

~ ii

m

i i i i i g N J m l i i i i

i m

i ~

ii

m

-

iii i - - ~ R !1 iii

IVa'.-~AI,..,.-,P~ ,.~ K'-.,-'SC

M~ si

scz

ca

i ~

o

Lt~L.~LL

i

i iiiii

I )re]~

f/t4o

~J"

Oe"

:

Sn

Fig. 3 tissue obtained in the analysis on the EMAL-2 instruments. The spectrum of the organic tissue sample is not contaminated by complex and polyatomic ions, the mass lines are resolved and easily identified. The absence in the spectrograms of lines of multiply charged ions is related to the possibility of energy focusing of the ions. The standard deviation of the results of the analysis without the use of standards is 0.1-0.2. A generalization of the data obtained [2, 4] made it possible to obtain data for improving the criteria for a hygienic evaluation of the dust factor with consideration of its material and disperse composition, which increases the reliability of the diagnosis of occupational diseases in industries with a high dust content in the air of work zones. On the basis of the results of the investigations obtained, the EMAL-2 instrument is recommended by the USSR Ministry of Health for use at sanitary-hygienic and sanitary-epidemiological institutions. The solution of problems of forensic medicine requires identification of traces left at the site of an incident. These are usually traces of spots, fragments of various objectsevidence. Identification can be made on the basis of comparable elemental compositions. In [3] a method is given for determining the elemental composition of blood spots on metal, which can be generalized for an analysis of any biological media in a liquid phase. The method of preparing liquid biological media suggests the application of the liquids on a substrate (spectrally pure metals with a large atomic number to avoid superposition of the lines of the main elements is desirable) and drying. In the case of spots left on objects-carriers an elemental analysis o[ a sample from the substrate and separately of the substrate is carried out. The elemental composition of the investigated spots is determined by comparing the mass spectra° The mass spectrum of blood on metal (tin) is given in Fig. 3. Analogous to the photogram (see Fig. 2), the spectrum is simple in composition, not contaminated by complex ions, and is easily identified. Bone, hair, and various blood groups were analyzed for identification in forensic medicine 19]. Samples in a solid phase did not require special preparations for analysis. For toxicological investigations it is necessary to conduct accurate quantitative analysis to determine with a high sensitivity small amounts of toxic elements in the investigated objects (medical implantable materials~ pharmaceutical preparations, etc.). A long time is needed for conducting such analysis by traditional methods~ since a determination of elements with various properties requires the use of various methods~ For a toxicological conclusion about a new polymer material for dentistry based on a stannous 2-etb:ylhexoate composition~ the elemental composition of an extract from the model medium was analyzed [i]. The extract was prepared from extracts of the liquid contacting the inves%igated sample of polymer material and then applied on a filter. At first the elemental composition of the clean filter was determined and then with a sample of the extract of the model medium. The presence of the toxic component tin was recorded at the level 10 -11 g in 1 ml of extract. Mass-spectrometric methods of determining the toxicity of medical materials can be recommended for new articles being introduced into medical practice. CONCLUSIONS i. Results of investigations into the microanalysis of biomedical specimens by the laser mass-spectrometry method showed the possibility of using this method for a quantitative analysis without using standards° 2. The method of preparing the biomedical specimens for analysis does not require special adaptation. LITERATURE CITED I. 2.

Io M. Aref'ev, N. E. Benyaev, A. R. Boriskin, et al., Metrological Provision of Measurements in Medicine and Biology [in Russian]~ Tallin (1983)~ p, 3. I. M. Aref'ev~ A. T. Boriskin~ A. So Bryukhanov, et al., Gig. Truda, No. 6, 54-56 (1983).

13

3. 4. 5.

I. M. 35-36 I. M. A. I.

Aref'ev, A. I. Boriskin, A. S. Bryukhanov, et al., Sud.-Med. Ekspert., No. 3, (1982). Aref'ev, A. A. Komleva, and L. A. Lutsenko, Lab. Delo, No. 9, 525-528 (1984). Boriskin, V. M. Eremenko, I. S. Lyal'ko, et al., Prib. Sis. Upravl., No. i, 26-29

(1983). 6. 7. 8. 9. i0. ii. 12.

A. I. Boriskin, High-Resolution Mass Spectrometer with a Laser Ion Source, Author's Abstract of Candidate Dissertation (1984). A. Yu. Bykovskii, T. A. Basova, V. I. Belousov, et al., Zh. Tekh. Fiz., 46, No. 6, 1338-1341 (1976). Yu. A. Bykovskii, G. I. Zhuravlev, V. I. Belousov, et al., Zavod. Lab., 44, 701-705 (1978). Yu. A. Bykovskii, A. A. Komleva, I. D. Laptev, et al., Measurements in Medicine and Their Metrological Provision [in Russian], Moscow (1983), p. 135. Spectroscopic Methods of Determining Traces of Elements [in Russian], Moscow (1979). Physical Methods of Analyzing Traces of Elements [in Russian], Moscow (1967). F. J. Conzemius and J. M. Cappelen, Int. J. Mass Spectrometry Ion Phys., 34, 197 (1980).

INVESTIGATION OF THE STATISTICAL CHARACTERISTICS OF LATEX SUSPENSIONS BY MEANS OF THE MAGISCAN-2 IMAGE ANALYZER A. A. Opalev, V. S. Eletskii, V. I. Marasev, and N. E. Yakovleva

UDC 615.471.03:616-074

The present work was devoted to an investigation of the statistical characteristics of latices for the purpose of determining the possibility of using these suspensions in works on the metrological provision of flow-type cytometers. The work was performed on the Magiscan-2 set (Joyce-Loebl Company, England) according to standard programs. These same programs can be used for advanced development of the technology of making latices and other particles with prescribed parameters. A program making it possible with a sample size of 2000-3000 particles to increase the number of measured parameters to 6-7 was used in the work. The sample size was not limited by the possibilities of the processing system and interval of moving the scanning stage of the microscope. It was established that an increase of the sample size from 2000 to 3000 particles changes the statistical characteristics by no more than 1%, and therefore a further increase of the sample is not expedient. The first part of the work was devoted to measurements without sampling recording of the objects. It was required to obtain the necessary data for measuring the geometric parameters with sampling recording and to determine the performance of the standard programs. The projection of the area of the particles onto the scanning plane, perimeters of the particles, and maximum size (diameter) were measured. Histograms of the distribution of these quantities and their statistical characteristics were obtained and the degree of correlation among them was determined. Histograms of the distribution of the optical density of the particles were also obtained and the degree of correlation of the optical characteristics with their geometric parameters, orientations (the angle in radians between the axis of the abscissas and diameter), and correlation between the optical density of the particle and their location on the microscope stage were determined. An increase of the sample size increases the requirements imposed on specimen preparation, and for a sample of 2000-3000 particles the specific characteristics of the measurements on the Magiscan-2 set required the fulfillment of a number of conditions. Two methods were most acceptable: i) placement of the investigated particles in glycerol and examination under a cover glass; 2) use of 0.22-~m nucleopore filters as a substrate. All-Union Research and Development Institute of Medical Laboratory Equipment, Leningrad. Translated from Meditsinskaya Tekhnika, No. i, pp. 29-33, January-February, 1985. Original article submitted April 4, 1984.

14

0006-3398/85/1901-0014509.50

© 1985 Plenum Publishing Corporation