ISSN 1061-9348, Journal of Analytical Chemistry, 2008, Vol. 63, No. 11, pp. 1094–1106. © Pleiades Publishing, Ltd., 2008. Original Russian Text © V.P. Fadeeva, V.D. Tikhova, O.N. Nikulicheva, 2008, published in Zhurnal Analiticheskoi Khimii, 2008, Vol. 63, No. 11, pp. 1197–1210.

ARTICLES

Elemental Analysis of Organic Compounds with the Use of Automated CHNS Analyzers V. P. Fadeeva, V. D. Tikhova, and O. N. Nikulicheva Vorozhtsov Institute of Organic Chemistry, Siberian Division, Russian Academy of Sciences, pr. akademika Lavrent’eva 9, Novosibirsk, 630090 Russia Received July 9, 2007; in final form, October 31, 2007

Abstract—Results of many years’ worth of studies on the determination of carbon, hydrogen, and nitrogen on automated CHNS analyzers were summarized. Catalytic oxide compositions were selected that allow for the analysis of synthetic and natural organic compounds and materials of any elemental composition and structure: polycyclic, condensed aromatic, heterocyclic, carbonaceous (graphites and carbons), organometallic, organoelement, etc. DOI: 10.1134/S1061934808110142

New compounds and materials, which appear as a result of the development of organic chemistry, such as different polycyclic, nitrogen containing, heterocyclic (imidazoles, oxazoles, triazoles, pyrroles, stable nitroxyl radicals, nitrones, pyrimidines, quinazolines, etc.), polyhalogen-containing aromatic including polyfluoroaromatic, organometallic, carbonaceous, etc., are characterized by a complex elemental composition and structure, a variety of properties, thermal and chemical stability, incombustibility, volatility, hygroscopicity, instability in light, etc. A necessary condition of their reliable identification and the verification of their purity is still the determination of the elemental composition of the compound performed by methods of organic elemental analysis. Its problems in the determination of carbon, hydrogen, and nitrogen in complex hardly degradable compounds by both classical and automated methods are well known. For example, in the determination of nitrogen in heterocyclic compounds containing nitrogen in the cycle or in groups such as azide, nitrile, nitro, nitrone, and amine groups in concentrations >30%, the incomplete conversion of different forms of nitrogen to elemental nitrogen was observed and, hence, underestimated results were obtained. Of significant difficulty is the analysis of polyfluorinated compounds, e.g., polyfluoroaromatic compounds, fluoropolymers, fluoroelastomers, lubricants, fluorine-containing graphites, polyfluorocarbons, etc. Many of these compounds contain peripheral >CF2 and –CF3 groups along with the C–F bonds constituting a rigid fluorinated framework, and different fluorinated graphites contain, e.g., intercalated halogen fluorides ClF3, ClF5, and BrF3 or alkali fluorides. The elemental analysis of these fluorides is complicated by the aggressiveness of fluorine and HF formed during the course of the decomposition, which leads to the corrosion of analytical instruments. Many fluorine-containing compounds

require more stringent decomposition conditions, because they are thermally stable, and the removal of fluorine as an interfering element from the combustion zone. The major elements of an organic substance, namely, carbon, hydrogen, and nitrogen, are commonly determined using commercially available CHN and CHNS analyzers, in which the organic substance undergoes oxidative decomposition and the subsequent reduction of nitrogen and sulfur oxides with the formation of the final products: carbon dioxide, water, elemental nitrogen, and sulfur dioxide. Currently, both old types of analyzers (Carlo Erba, models 1106 and 1108; Hewlett-Packard, model 185; Perkin Elmer, model 240; etc.) and new types (Euro EA 3000; Perkin Elmer 2400, series II; CE 440; Vario EL III; etc.) are used in the practice of organic elemental analysis. It is known that the oxidants and catalysts developed and proposed in classical methods of elemental CHN analysis also find application in automated analyzers. Co3O4, the product of the thermal decomposition of silver permanganate [1], Cr2O3 [2, 3], NiO [4], WO3 [5, 6], V2O5 [7], SnO2 [8, 9], ëeO2 [10], MgO [11], or their mixtures are used as additives to samples including hardly combustible substances containing, e.g., B, P, Si, and alkali metals; oxide additives improving the combustion of pyrimidines and triazoles (Co3O4–V2O5) [12], and polycyclic and organometallic compounds (V2O5, MnO2, K2Cr2O7, etc.) were also proposed [13– 15]. The reagents added to a portion of a sample were calculated for a single effect and are removed before the analysis of the next sample. These are oxygen donors, oxidation catalysts, and absorbers of the interfering compounds. The functions of these reagents can hardly be separated. Commonly, in both classical and automated methods, the sample is not completely oxidized in the pyrol-

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ysis zone. Therefore, the reagents facilitating the complete oxidation of the pyrolysis products are placed downstream in the reaction tube. Among these are compounds providing the long-term oxidizing effect and acting as a catalyst or an oxygen donor. The main reagents that were proposed in classical methods are Cr2O3, CuO, CeO2, SnO2, AgVO3 [16–18], MnO2 + Cr2O3 + WO3 [19], WO3 [20], WO3 + Ag2WO4 + AgMnO4 [21], Co3O4 on Al2O3, with Ag on pumice, and CeO2 [22], Pt/asbestos + Ag2WO4 + MgO + ZrO2 + Pt/asbestos + Ag + Au [23], etc. All of these compositions can also be used in automated analyzers. To improve the analysis of fluorine-containing compounds in Carlo Erba automates, using CeO2–MgO [24], WO3, or WO3 in a mixture with Al2O3 was proposed [25, 26]. In the reaction unit of automated elemental analyzers, interfering C, H, and N compounds were also absorbed with the use of selective absorbing reagents. Combined reagents Co3O4 + Ag [27], SnO2 + Ag [9], AgVO3, and Ag with Al2O3 [28] are efficient in the analysis of substances containing halogens and sulfur; the mixed reagent 3MgO·Al2O3 more intensely absorbs hydrogen fluoride than individual MgO. These reagents are placed either in the additional oxidation zone or in the reduction zone according to the optimum temperature required for their action. Oxide additives proposed by the companies producing automated elemental analyzers to provide the complete decomposition of the substance are sometimes insufficiently efficient in the analysis of complex multielement hardly degradable organic compounds; therefore, substantial improvements are required, primarily at the step of substance decomposition. The aim of this work was to consider the efficiency of the use of our universal catalytic oxide compositions; the use of these compositions in elemental CHNS analyzers provides the complete decomposition of organic compounds and the successful determination of C, H, and N in substances of any elemental composition and structure: polycyclic, condensed aromatic (naphthols, anthraquinones, ceramidonines, etc.) including polyfluoroaromatic, organometallic (containing any metals), graphites, humic acids, and nitrogenous heterocyclic compounds like pyrimidines, pyrazolones, triazoles, etc. EXPERIMENTAL Reagents and Instruments. Preparation of catalytic oxide compositions. For the preparation of catalysts and oxides, we used reagents of the chemically pure or analytical grade from Reakhim. Catalytic oxide composition for filling the oxidation reactor of the CE analyzer. The composition was prepared by mixing Ag2WO4, ZrO2, and MgO (analytical grade) in the mass ratio 2 : 8 : 1 or 2 : 7 : 2, cautiously ground in a mortar with a small amount of water to form a thick homogeneous paste, which was forced JOURNAL OF ANALYTICAL CHEMISTRY

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through a sieve with a mesh diameter of 2 mm. The obtained granules were kept for 2 h at a temperature of 120°ë in a drying oven, screened from dust, and, next, baked in a muffle furnace for 2 h at 500–600°ë. The granules were stored in a glass-stoppered bottle. The ratio of the ZrO2 and MgO components in the composition can be changed depending on the composition of the analyzed substances. To obtain Ag2WO4 33 g of Na2WO4 · H2O was dissolved in 1 L of distilled water and heated, an equal amount of a solution containing 34 g of AgNO3 was added with stirring, and the mixture was boiled for 10–15 min. The precipitate was washed on the filter with hot and then cold, distilled water until silver ions were removed and next dried at 105–110°ë in a drying oven for at least 2 h. ZrO2 was obtained by the cautious decomposition of ZrO(NO3)2 · 2H2O or Zr(NO3)2 in a porcelain crucible heating it on an electric hotplate until the evolution of nitrogen oxides stopped. Next, it was baked in a muffle furnace at 1000°ë for 3 h. Cr2O3 was prepared from (NH4)2Cr2O7 as described in [29]. Co3O4 of an analytical grade was used. Catalytic oxide composition for addition to a portion of a substance in the HP analyzer. As the addition to a portion of a substance in combustion in the automated analyzer Hewlett-Packard, model 185, we used a catalytic oxide composition developed by us, which consisted of four components (mass %): MnO2 – 64%, Cr2O3 –13%, PbO2 –13%, SiO2, 10. The procedure for the preparation of the composition was described in [29]. The oxidation zone in the reactor of the EA analyzer was filled with tungsten anhydride (WO3) provided by the producing company or prepared from powdered WO3 by pressing it with alumina, subsequent comminution in a porcelain mortar, and screening to a particle size of 1–2 mm. The lifetime of the filled vertical oxidation reactors (in CE and EA analyzers) was determined by the amount of ash accumulated in the combustion zone; it was 300 combustions at the average Copper that was used in the reduction zone of analyzers was prepared by the reduction of “wire” copper oxide in a hydrogen flow at a temperature of ∼500°ë. As standard (reference) compounds for the calibration of instruments, we used acetanilide, 4-nitroaniline, benzoic acid, cyclohexanone 2,4-dinitrophenylhydrazone, 2,5-bis-(5-tert-butyl-2-benzoxazolyl)thiophene, S-benzylthiuronyl chloride, sulfanilamide, and cystine provided by Carlo Erba and enterprise standards (Vorozhtsov Institute of Organic Chemistry): pentafluorobenzoic acid, toluene sulfochloride, urea, and decafluorophenyl disulfide previously purified by recrystallization and analyzed. Elemental analysis was performed in the following analyzers: Hewlett-Packard, model 185 (United States) (HP); Carlo Erba, model 1106 (Italy) (CE); and Euro EA 3000 (Italy) (EA). Samples were weighed on a balance Mettler Toledo AT-20 (Switzerland) or Sartorius CP2P (Germany).

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CE analyzer, calculations were performed using the areas of these peaks obtained on the integrator. In the EA analyzer, calculations were performed using the Callidus program supplied with the analyzer.

(b)

3

RESULTS AND DISCUSSION

2

2

1

1

Fig. 1. Filling of the oxidation tube in the Carlo Erba automated analyzer: (a) (1) Co3O4, 25 mm; (2) Ag2WO4 + ZrO2 + MgO, 50 mm; (3) Cr2O3, 60 mm; (b) (1) Ag2WO4 + ZrO2 + MgO, 65 mm; (2) Cr2O3, 70 mm.

Analysis. Portions of samples with a mass of no more than 1 mg were weighed in tin containers (aluminum boats can be also used in the HP analyzer). In the HP analyzer, the holder with the sample was completely covered with the catalytic oxide additive described above and introduced into the horizontal tube in the combustion zone at 1100°ë, where samples were burned in the static mode for 50 s. The pyrolysis products were afteroxidized at the end of the tube with copper oxide and blown with the carrier gas (He) into the reduction tube filled with reduced-wire Cu (580°ë), in which nitrogen oxides were reduced to elemental nitrogen and excess oxygen was absorbed. Resulting N2, CO2, and H2O were separated on a column with Porapak Q and determined with a heat conductivity detector (catarometer). In CE and EA automated analyzers, a sample was burned in a vertical reactor (oxidation tube) in the dynamic mode (at 1020°ë in CE and at 1050°ë in EA) in an He flow with the addition of O2 (10 mL) at the instant of sample introduction. Portions of the sample in tin capsules were placed in the automated sampler, from which they were transferred to the oxidation tube at regular intervals. After the pyrolysis, the resulting products were afteroxidized in the lower part of the reactor filled with a catalytic oxide composition and then passed through the reduction zone. In the EA analyzer, the mixture of sulfur oxides was quantitatively converted to SO2 on reduced copper. The end of the analysis is analogous to that described above for HP. The concentration of each element in the HP instrument was calculated after the measurement of the corresponding peak heights in the chromatogram. In the

Determination of carbon, hydrogen, and nitrogen on the Carlo Erba analyzer. For the CE analyzers, the company supplies reagents, fillers of the oxidation reactor: Cr2O3, Ag Co3O4, and WO3. We used two types of fillings of the oxidation reactor of the analyzer presented in Fig. 1. Filling a involved three components: Co3O4, combined catalytic oxide composition Ag2WO4, ZrO2 + MgO, and Cr2O3. Filling b consisted of two components and involved no Co3O4. ZrO2 and MgO involved in the composition are highly active afteroxidation catalysts and, in addition, excellent absorbers of fluorine-containing products [30] produced on burning organofluorine compounds. The Ag2WO4 component absorbs halogens, sulfur oxides, and other interfering elements, which is favored, along with oxidizing properties, by Co3O4. Filling a was found to be optimum; it forms the basis of the approved procedure, and the results presented in Tables 1 and 2 were obtained with the use of this three-component filling. To obtain calibration coefficients with this filling, it is not necessary to bring the quantitative elemental composition of reference samples close to the analyzed samples, as done by some researchers [24]. Figure 2 presents the dependences of the calibration coefficients on the percentage of the determined elements. As seen in Fig. 2, this dependence is absent for the studied concentration ranges (H, from 1 to 12%; C, from 30 to 90%; N, from 0 to 60%). With the used of the proposed catalytic oxide composition, the analyses of synthetic organic and natural compounds with different elemental composition and a rather wide concentration range of the determined elements were preformed on the Carlo Erba analyzer for many years (Table 1). For example, a specific feature of compound 1 is the high concentration of carbon (above 80%), and the specific feature of compounds 2 and 3 is the high concentration of nitrogen in different forms (35 and 64%, respectively). Compounds 5 and 6 contain more than 50% fluorine, which is specified in the second column of Table 1. Other compounds presented in Table 1 contain heteroelements in different combinations: sample 2, more than 64% sulfur; sample 4, iodine and sulfur; sample 8, phosphorus; sample 9, bromine and sulfur; sample 10, fluorine and chlorine; samples 11 and 12, bromine, chlorine, and a metal atom (copper and cobalt, respectively). Table 2 presents the results of the analysis of samples of chalcogenide cluster compounds (1–3) and samples of the complexes of metals with organic ligands (4–6). Measurements of the concentrations of carbon, hydrogen, and nitrogen in samples of organic sub-

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0.12

(‡)

0.08 0.04 0

30

40

50

0.05

Coefficients

stances with the use of the Carlo Erba automated elemental analyzer (MVI NIOKh SO RAN No. 01-95) were performed by the procedure approved according to GOST R8.563 by FGUP Ural Research Institute of Metrology. Determination of carbon, hydrogen, and nitrogen on the Hewlett-Packard analyzer. With the use of oxide additives supplied by the company for the HP CHN analyzer, the results for carbon and nitrogen in the case of complex substances in an elemental composition were underestimated commonly by 1–5% and above. The errors are evidently related to the properties of the analyzed compounds and the character of their thermal decomposition. The decomposition of nitrogen-containing substances, depending on the speciation of nitrogen in the substance, can yield such nitrogencontaining pyrolysis products as ammonia, dicyan, hydrogen cyanide, dinitrogen monoxide, nitrogen oxide, nitrogen dioxide, and free nitrogen; however, in the case of the complete oxidation, only nitrogen and nitrogen oxide and/or dioxide are formed. In the combustion of some compounds, there is a possibility of the underoxidation of the resulting hydrocarbons, which affects the results of the determination of carbon and hydrogen, or the formation of the nitrile group, which leads to their binding to copper cyanide (in the zone of the formation of nitrogen oxides), and the results of the analysis for nitrogen are underestimated. We studied oxides and their mixtures (NiO, V2O5, MnO2, PbO2, Cr2O3, WO3, etc.) as oxidizing additives to a sample and developed a catalytic oxide composition (MnO2, 64 mass %; Cr2O3, 13 mass %; PbO2, 13 mass %; SiO2, 10 mass %), which is suitable for the analysis of a wide range of compounds of different classes including hardly combustible compounds [29]. The selection of this composition was justified by the fact that Cr2O3 is a strong catalyst of the surface action stable up to a temperature of 2000°ë and MnO2 and PbO2 are oxygen donors, which are necessary for oxidation without oxygen additions. In addition, PbO forms at a temperature above 500°ë; it melts at a temperature of 886°ë and occurs in the molten state in the combustion zone providing favorable conditions for the rapid oxidation of carbon in substances of a complex composition, because PbO can form melts with oxides of heteroelements interfering with the oxidation. Silica, on the one hand, is used as a dilutant, which imparts the flowability to the composition, and, on the other hand, at 600– 850°ë interacts with many elements to form silicates or molecular compounds of the type (MO)y(SiO2)x [31]. Along with the role of an oxidant, the developed catalytic oxide composition provides the retention of such elements as halogens, sulfur, phosphorus, arsenic, antimony, boron, selenium, tellurium, osmium, and alkali and other metals, which interfere with the determination of carbon, hydrogen, and nitrogen, in the combustion zone. This additive was insufficiently efficient only in the case of the combustion of graphite, which was oxidized by only 50%, because an excess of oxygen

1097

60

70

80

90 %C

(b)

0.03

0.01 0

2

4

6

8

10

12 %H

40

50

60 %N

(c) 0.4

0.2

0

10

20

30

Fig. 2. Dependence of calibration coefficients on the percentage of the determined elements: (a) carbon, (b) hydrogen, and (c) nitrogen; average values are 0.1104, 0.0449, and 0.3905, respectively.

provided in the CE and EA analyzers is necessary for its successful analysis. The developed catalytic oxide composition has been used for the analysis of different compounds for many years. Table 3 presents examples of the results of the analysis of some compounds, which are difficult for analysis and, however, were successfully analyzed: organofluorine, nitrogenous heterocyclic, polycyclic, etc. Determination of carbon, hydrogen, nitrogen, and sulfur on the Euro EA 3000 analyzer. The EA analyzer is a completely automated complex for the determination of four elements: C, H, N, and S. As mentioned above, the principle of the method is the same as in the CE analyzer; however, the use of a common on-line scheme, which includes a microbalance, a high-temperature main unit, and computer control, makes it possible to increase the speed of analysis, to automatically take into account the mass of the intro-

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F

F

Cl

N

3

4

HS

2

1

Code

No. 11

S

S

O

S

F

F

C6H5

N3

SH

C18H37

N

S

64.4% S

S

N N

N C O C16H33

64.6% F

J– C18H37

N+

C(CF3)3

CH3

N

S

N N

O

O

C(CH3)3

Analyzed compound

Cl

34.60

65.23

60.91

16.10

80.65

calculated*

34.88 ± 0.28

65.08 ± 0.51

60.54 ± 0.40

16.08 ± 0.04

80.58 ± 0.59

found ϖ(C) ± δ**

Mass fraction of C, %

0.79

8.07

3.69

0.07

8.21

calculated*

0.78 ± 0.01

7.92 ± 0.16

3.69 ± 0.54

0.08 ± 0.01

8.36 ± 0.24

found ϖ(H) ± δ**

Mass fraction of H, %

Table 1. Results of the determination of carbon, hydrogen, and nitrogen on a Carlo Erba automated analyzer, model 1106

0

2.52

35.83

18.77

2.00

calculated*

0

2.39 ± 0.15

35.83 ± 0.06

18.39 ± 0.38

2.16 ± 0.20

found ϖ(N) ± δ**

Mass fraction of N, %

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9

8

7

6

Code

F

Br

N

Br

N

O

H3C NH

F

F

F

Table 1. (Contd.)

N

S

N

NHNH2

55.7% F

S

N

N

49.1% Br 19.6% S

P(C6H5)3

N

CH3

O

C C6F5

CH CF3

F

Analyzed compound

22.10

80.63

38.95

40.65

calculated*

22.36 ± 0.23

80.98 ± 0.64

39.15 ± 0.28

40.75 ± 0.30

found ϖ(C) ± δ**

Mass fraction of C, %

0.62

4.54

6.54

0.27

calculated*

0.61 ± 0.02

4.44 ± 0.25

6.60 ± 0.33

0.30 ± 0.03

found ϖ(H) ± δ**

Mass fraction of H, %

8.59

5.53

54.51

0

calculated*

8.44 ± 0.25

5.46 ± 0.16

54.70 ± 0.35

0

found ϖ(N) ± δ**

Mass fraction of N, %

ELEMENTAL ANALYSIS OF ORGANIC COMPOUNDS 1099

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Br

Br

F

F

O N

O N

F

F

F

N

O

NO2

N

O

NO2

F

C C

Cl Cl

Co

Cu

F

F

O2N

O

N

O2N

O

N Br

N O · 0.5 CHCl3

44.3% F 16.5% Cl

Br

N O · 0.5 CH2Cl2

F

F

Analyzed compound

39.19

38.09

39.19

calculated*

39.05 ± 0.33

37.71 ± 0.61

39.47 ± 0.66

found ϖ(C) ± δ**

Mass fraction of C, %

Notes: * Mass fraction of the element (%) calculated from the molecular formula of the compound. ** δ is the confidence interval calculated for n = 5, P = 0.95.

12

11

10

Code

Table 1. (Contd.)

3.59

3.44

0

calculated*

3.46 ± 0.39

3.33 ± 0.51

0

found ϖ(H) ± δ**

Mass fraction of H, %

10.33

10.06

0

calculated*

10.40 ± 0.11

9.75 ± 0.59

0

found ϖ(N) ± δ**

Mass fraction of N, %

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F

Bi

S

F

CF3

Sb CH2

S

CH2

F

F

F

CF3

CH2

CF3

3

3

S

46.4% F 8.7% S

41.7% F 10.1% S

C4H9 3

OH

C4H9

found ϖ(C) ± δ**

3.31 3.32 0.92

18.10 ± 0.35 18.00 ± 0.40 6.69 ± 0.23

26.00

63.79

26.37

25.30 ± 0.75

63.70 ± 0.29

25.70 ± 0.74

8.50

Complexes of metals with organic ligands

6.28

17.88

17.85

8.20 ± 0.33

1.20 ± 0.30

3.49 ± 0.15

3.46 ± 0.21

found ϖ(H) ± δ**

Mass fraction of H, % calculated*

Chalcogenide cluster compounds

calculated*

Notes: * Mass fraction of the element (%) calculated from the molecular formula of the compound. ** δ is the confidence interval calculated for n = 5, P = 0.95.

6

5

Bi

(H3O){Nd(DMF)3(H2O)3}[Re6Se8(CN)6] (27.0 % Se)

3

4

((n-Bu)4N)2Mn(H2O)4[Re6Se8(CN)6] · 2H2O (24.8 % Se)

2

F

((n-Bu)4N)2Ni(H2O)5[Re6Se8(CN)6] · 2H2O (24.6 % Se)

1

F

Analyzed compound

Code

Mass fraction of C, %

5.49

4.39

4.38

calculated*

5.79 ± 0.39

4.45 ± 0.15

4.39 ± 0.10

found ϖ(N) ± δ**

Mass fraction of N, %

Table 2. Results of the determination of carbon, hydrogen, and nitrogen in complex organometallic compounds on a Carlo Erba automated analyzer, model 1106

ELEMENTAL ANALYSIS OF ORGANIC COMPOUNDS 1101

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3

2

1

Code

O2N

AcO

F3C

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N

C6H5

O

N

N3

N H

N N

N

Cl

F

F

SH

N

N

18.1% F

NO2

C NHCH2CH2COOCH3

O

N3

F

33.7% F 19.0% S

Analyzed compound

60.40

72.32

49.53

21.30

calculated*

60.40 ± 0.18

72.37 ± 0.15

49.24 ± 0.35

21.57 ± 0.31

found ϖ(C) ± δ**

Mass fraction of C, %

4.09

9.27

1.28

1.18

calculated*

4.27 ± 0.25

8.98 ± 0.37

1.28 ± 0.25

1.10 ± 0.10

found ϖ(H) ± δ**

Mass fraction of H, %

Table 3. Results of the determination of carbon, hydrogen, and nitrogen on a Hewlett-Packard automated analyzer, model 185

16.26

2.34

31.11

24.84

calculated*

16.26 ± 0.01

2.63 ± 0.30

31.31 ± 0.21

24.92 ± 0.33

found ϖ(N) ± δ**

Mass fraction of N, %

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Br

Br

H3C

CN

N

O

NH2

N

N

O

NO2

O

O N

O N

CH3

N

N

O

O

Ni

Cu

N

C

H

Br

Br

N O · 0.5 CH2Cl2

N O

O2N

O

N

O2N

O

N

CH2C6H5

Analyzed compound

39.19

45.53

61.67

76.27

39.26 ± 0.28

45.64 ± 0.54

61.78 ± 0.11

76.56 ± 0.31

Mass fraction of C, % found calculated* ϖ(C) ± δ**

Notes: * Mass fraction of the element (%) calculated from the molecular formula of the compound. ** δ is the confidence interval calculated for n = 5, P = 0.95.

8

7

6

5

Code

Table 3. (Contd.)

3.59

4.41

4.71

6.40

3.83 ± 0.49

4.52 ± 0.18

4.69 ± 0.34

6.49 ± 0.36

Mass fraction of H, % found calculated* ϖ(H) ± δ**

10.33

8.17

26.16

8.09

9.89 ± 0.49

8.23 ± 0.10

26.15 ± 0.23

8.08 ± 0.27

Mass fraction of N, % found calculated* ϖ(N) ± δ**

ELEMENTAL ANALYSIS OF ORGANIC COMPOUNDS 1103

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Br

Br

F

COOCH3

3

4

F

F

F

F

Br

F

F

F

F

F

F

F

F

2

F

F

F

F

F

1

Code

F

F

Br

Br

81.5% Br 3.9% F

34.1% F

COOCH3

47.7% F

F

47.7% F F

F

F

F

F

F

51.9% F

O

S

F

F

F

F

F

F

F

F

F

S

F

F

S

O

S

S

F

Analyzed compound

14.68

36.19

43.05

36.19

39.37

calculated*

Mass fraction of H, %

Mass fraction of N, %

Mass fraction of S, %

14.44 ± 0.46

36.30 ± 0.22

43.34 ± 0.35

36.31 ± 0.14

39.15 ± 0.20

0

0

1.35

0

0

1.49 ± 0.22

0

0

0

0

0

0

8.05

7.17

16.10

8.76

7.90 ± 0.15

7.13 ± 0.05

15.96 ± 0.36

8.67 ± 0.46

found found found found calculated* calculated* calculated* ϖ(C) ± δ** ϖ(H) ± δ** ϖ(N) ± δ** ϖ(S) ± δ**

Mass fraction of C, %

Table 4. Results of the determination of carbon, hydrogen, nitrogen, and sulfur on a Euro automated analyzer, model EA 3000

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F

H

F

H

F

F

F

F

F

F

F

N N

N

Se

F

F

F

F

N 29.4% Se S 21.2% F

F

F

F

F

52.5% F

F

F

H 34.6% Se 33.3% F

42.3% Se

50.6% Se

N S N Se

Se Se

Se

Se Se

F

F

Analyzed compound

26.78

31.60

38.72

46.17

39.79

calculated*

Mass fraction of H, %

Mass fraction of N, %

Mass fraction of S, %

26.61 ± 0.26

31.94 ± 0.36

39.05 ± 0.38

45.94 ± 0.28

39.50 ± 0.33

0.37

0.44

2.73

3.23

0

0.38 ± 0.01

0.55 ± 0.11

2.72 ± 0.09

3.19 ± 0.08

10.41

0

7.53

0

7.74

10.25 ± 0.25

7.46 ± 0.41

7.50 ± 0.28

11.91

0

8.62

0

0

11.94 ± 0.04

8.67 ± 0.39

found found found found calculated* calculated* calculated* ϖ(C) ± δ** ϖ(H) ± δ** ϖ(N) ± δ** ϖ(S) ± δ**

Mass fraction of C, %

Notes: * Mass fraction of the element (%) calculated from the molecular formula of the compound. ** δ is the confidence interval calculated for n = 5, P = 0.95.

10

9

8

7

6

Code

Table 4. (Contd.)

ELEMENTAL ANALYSIS OF ORGANIC COMPOUNDS 1105

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duced sample, and to automate the calculation of the results of the analysis. The use of an oxide layer consisting of WO3 in the reactor and the addition of V2O5 to the portion of the sample made it possible to solve the rather complex problem of elemental analysis: the determination of sulfur (along with carbon, hydrogen, and nitrogen) in selenium-containing substances (Table 4). As seen in Table 4, under the conventional conditions of the operation of this analyzer, selenium-containing substances are completely oxidized; the presence of Se in the range from 29 to 50% does not affect the quantitative determination of carbon and hydrogen; and selenium oxides are completely absorbed in the reactor, do not arrive at the chromatographic column, and, consequently, do not change the determined concentration of sulfur in the studied substances. The EA analyzer was also successfully used for the analysis of substances containing different metals, phosphorus, halogens (including fluorine), sulfur, silicon, boron, etc. Thus, based on the results of many years of work, we can state that carbon, hydrogen, nitrogen, and sulfur can be determined on automated element analyzers in substances of any elemental composition and structure with the selection and use of particular catalytic oxide compositions and absorbers of interfering elements. The catalytic oxide compositions that were proposed and used by us allow the successful analysis of complex multicomponent hardly combustible substances. REFERENCES 1. Rezl, V. and Janak, I., J. Chromatogr., 1973, vol. 81, no. 2, p. 233. 2. Pella, E. and Colombo, B., Mikrochim. Acta, 1983, no. 5, p. 697. 3. Kirsten, W.J. and Hesselins, A., Microchem. J., 1983, vol. 28, no. 4, p. 529. 4. Culmo, R.F., Mikrochim. Acta, 1969, vol. 57, no. 1, p. 175. 5. Pella, E. and Colombo, B., Mikrochim. Acta, 1978, nos. 3–4, p. 271. 6. Kissa, E. and Seepex-Yllo, M., Mikrochim. Acta, 1967, no. 2, p. 287. 7. Gel’man, N.E. and Kiparenko, L.M., ZhVKhO Im. D.I. Mendeleeva, 1980, vol. 25, no. 6, p. 641. 8. Rezl, V. and Uhdeova. J., Mikrochim. Acta, 1979, vol. 71, nos. 5–6, p. 349.

9. Rezl, V. and Buresova, A., Mikrochim. Acta, 1982, vol. 78, nos. 1–2, p. 95. 10. Monar, I., Iikrochim. Acta, 1972, vol. 60, no. 6, p. 7 84. 11. Kirsten, W.J., Microchem. J., 1971, vol. 16, no. 4, p. 610. 12. Tefft, M.L. and Gustin, G.M., Microchem. J., 1966, vol. 10, nos. 1–4, p. 175. 13. Larionov, V.P., Al’yanov, M.I., Khlyupin, Yu.M., Borodkin, V.F., Yashin, Ya.I., and Smirnov, R.P., Trudy Ivanovskogo Khim.-Tekhnol. In-Ta, 1973, no. 15, p. 71. 14. Miroshina, V.P. and Dubina, E.M., Zh. anal. khim., 1991, vol. 46, no. 3, p. 493. 15. Kiparenko, L.M., Gel’man, N.E., Maslennikova, N.D., and Smirnova, V.I., Zh. anal. khim., 1980, vol. 35, no. 2, p. 328. 16. Ebeling, M. and Malter, L., Microchem. J., 1963, vol. 7, p. 179. 17. Lebedeva, A.I., Nikolaeva, N.A., and Orestova, V.A., Izv. Akad. Nauk SSSR, Otd. Khim. Nauk, 1961, no. 7, p. 1350. 18. Macdonald, A.M.G.. and Turnton, G.G., Microchem. J., 1968, vol. 13, no. 1, p. 1. 19. Celon, E. and Bresadola, S., Anal. Chem., 1968, vol. 40, no. 8, p. 972. 20. Mizukami, S. and Jeki, T., Microchem. J., 1963, vol. 7, no. 4, p. 485. 21. Fildes, J.E., Mierochim. Acta, 1970, vol. 58, no. 5, p. 978. 22. Binkowski, J. and Levy, R., Bull. Soc. Franne, 1968, no. 10, p. 4289. 23. Yeh, C.S., Microchem. J., 1963, vol. 7, no. 3, p. 303. 24. Borda, P.P., Z. Analyt. Chem., 1989, vol. 334, no. 7, p. 715. 25. Maslennikova, N.D., Kiparenko, A.M., Buyanovskaya, A.G., and Terent’eva, E.A, Zh. anal. khim., 1993, vol. 48, no. 3, p. 547. 26. Baccanti, M. and Colombo, B., JOP, 1990, vol. 18, no. 1, Ref. zh. chem., 1990, no. 15A337. 27. Kainz, G. and Horvatitsch, H., Mikrochim. Acta, 1962, vol. 50, no. 1, p. 7. 28. Padowertz, W., Microchem. J., 1969, vol. 14, no. 1, p. 110. 29. Fadeeva, V.P. and Moryakina, I.M., Izv. Sib. Otd. Akad. Nauk SSSR, Ser.: Khim., 1981, vol. 6, no. 14. p 113. 30. Gel’man, N.E. and Korshun, M.O., Dokl. Akad. Nauk SSSR, 1953, vol. 38, no. 4, p. 685. 31. Gel’man, N.E., Terent’eva, E.A., Shanina, T.M., et al., Metody kolichestvennogo organicheskogo elementnogo mikroanaliza (Quantitative Methods for Organic Elemental Micronalysis), Moscow: Khimiya, 1987.

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