Determination of six aromatic compounds by using ...

5 downloads 0 Views 278KB Size Report
thalene(DHN), 2,4-dimethoxybenzaldehyde(DMO), methyl sal- icylate(MSA) and ..... and 2,4,6-trichlorophenol as well as 2,3,4,6-tetrachlorophenol down to 0.1-1 ...
Fresenius J Anal Chem (1995) 351:325-327 - © Springer-Verlag 1995

Determination of six aromatic compounds by using target factor analysis-UV spectrometry

dissolving proper amounts of each aromatic compound in 95% ethanol.

Apparatus. A Varian DMS-200 UV-visible spectrophotometer Si-Qing Xia 1, Pei-Lin X U 1 , Jian-Hui Sun 1, Zhong-Xiao Pan 2, Mao-Sen Zhang 2, Le-Ming Shi 2 i Department of Chemistry, Henan Normal University, Xinxiang, Henan 453002, People's Republic of China 2 Department of Modem Chemistry, University of Science and Technology of China, Hefei 230026, People's Republic of China Received: 17 August 1994/Revised: 27 September 1994/ Accepted: 30 September 1994

Abstract. The UV-spectra solutions containing mixtures of 1naphthylamine(NAA), 1-naphthol(NAP), 2,7-dihydroxynaphthalene(DHN), 2,4-dimethoxybenzaldehyde(DMO), methyl salicylate(MSA) and dibutyl phthalate (DBP), have been measured. The numbers, identities and concentrations of the aromatic compounds in the mixtures have been determined successfully using Target Factor Analysis. Some sample mixtures have been analyzed successfully. The average recoveries are 99% for NAP, 102% for NAA, 102% for DHN, 103% for DMO, 102% for MSA, 101% for DBP.

was used under the following experimental conditions: Scanning range 193.5-306.45 nm; Scanning rate 100 nrrdmin; Smoothing constant 1.0 s; Slit 0.8 nm. An IBM PC/AT microcomputer connected to the DMS spectrophotometer via an IEEE-488 bidirectional interface was used for data acquisition. A software package, purchased from the Varian Corporation, was used for spectral data collection and the programs used were written in BASIC.

Experimental procedures. For each of the aromatic compounds studied, a series of six standard solutions diluted from the stock solution to different concentrations were measured at 226 wavelength points from 193.95 to 306.45 nm every 0.5 nm. Mixture samples were also measured under the same experimental conditions. All the spectral data were collected on a hard disk of the IBM PC/AT microcomputer by using the VatJan's software package. For each aromatic compound, a set of the relative absorptivities calculated by a linear regression program was used as its testing target.

Results and discussion

Factor analysis of mixture data Introduction 1-Naphthylamine, 2,7-dihydroxynaphthalene, 2,4-dimethoxybenzaldehyde, 1-naphthol, methyl salicylate and dibutyl phthalate are six commonly encountered aromatic compounds absorbing in the UV range. The determination of these aromatic compounds by means of direct UV spectrophotometry has been rarely reported. Because the UV spectra of these aromatic compounds severely overlap, it is very difficult to carry out such determinations without the aid of mathematical methods. Factor analysis is a multivariant technique which attempts to express a data matrix [A] as a product of a row matrix [E] and a column matrix [C]

Three data matrices constructed from absorbances of the mixtures of the aromatic compounds were subjected to FA. For one of them, the corresponding eigenvalues and five criteria for deducing true factors are listed in Table 1. As shown in Table 1, the IND function reaches a minimum at n - 6. There is no further reduction in IE upon using more than six eigenvectors. For n = 6 the real error (RE) is less than 0.0010 absorbance unit. The reduced eigenvalues decrease from n = 1 to 6 but remain fairly constant after n > 6. All these criteria give evidence that six species are present in the sample mixtures of aromatic compounds analyzed. From results of the other two matrices analyzed, the same conclusions were obtained.

[A] = [E][C]

Target testing of aromatic components suspected

Since [A] consists of r rows and c columns, its size is r x c. If these are n controlling factors, [E] is an r × n matrix and [C] is an n × c matrix. The first stage in factor analysis involves the use of a mathematical process called principal component analysis, which is used to define the numbers of factor. To complete this tasks, we examine the error criteria such as RE (real error), IE (imbedded error), IND (factor indicator function) [1, 4-6], REV (reduced eigenvalues) [6] and ER (eigenvalue ratio) [7] together. The second stage involves transforming the abstract matrices into physically significant matrices, [E] and [C], which have real chemical meaning, so that [A] = [E][C]. This is achieved by employing target factor analysis [1-3]. In order to determine whether or not a test vector is acceptable as a true factor, criteria such as RELI (reliability function) and SPOIL (spoil function) [1, 4] were used.

The presence of individual suspected aromatic compounds was tested by means of TFA. The absorptivity values of each suspected aromatic compound at the same wavelength and under the same experimental conditions, obtained by utilizing a linear regression technique, are taken as the absorptivity test vectors. The results of criteria related are given in Table 2. As approximate rule it can be stated that a target is considered reliable if its RELI is 0.5 or greater and unreliable if its RELI is less than 0.5; a target is considered acceptable if its SPOIL lies between 0.00 and 3.0, moderately acceptable if its SPOIL lies between 3.0 and 6.0, and unacceptable if its SPOIL is greater than 6.0 [2], all six test vectors are acceptable as true factors of the mixture samples studied.

Experimental section

Materials. A.R. grade compounds (NAP, NAA, DHN, DMO, MSA and DBP) were used. Stock solutions were prepared by

Correspondence to: Si-Qing Xia

Results for synthetic samples Some synthetic sample mixtures were measured using the TFA method. Representative results are listed in Table 3. As shown in Table 3, the results obtained by TFA are in accordance with the experimental results. The standard deviations are within _+ 0.04 for NAP, + 0.03 for NAA, + 0.05 for DHN, _+ 0.06 for DMO, +_ 0.07 for MSA and + 0.13 for DBP, respectively. Recoveries for all of the six aromatic compounds are satisfactory.

326 Table 1. Results of factor analysis of a data matrix

a Eigenvalues

n

)~a (X 10 3)

RE (X 10 3)

IE (X lO3)

IND (X 10 5)

ER

REV (× 106)

1 2 3 4 5 6 7 8 9 10 11 12 13

16736.96 608.25 33.54 2.4759 1.3762 0.1857 0.0071 0.0034 0.0030 0.0025 0.0012 0.0010 0.0006

41.667 10.500 3.618 2.381 0.908 0.295 0.254 0.232 0.207 0.175 0.163 0.143

11.556 4.119 1.738 1.320 0.563 0.200 0.185 0.182 0.172 0.154 0.150 0.138

28.936 8.678 3.618 2.939 1.419 0.602 0.698 0.928 1.294 1.947 4.066 14.320

27.52 18.23 13.55 1.80 7.41 26.06 2.08 1.13 1.23 2.02 1.21 1.58

41531 1689.6 105.15 8.843 5.663 0.8927 0.0407 0.0240 0.0260 0.0280 0.0190 0.0250

Table 2. Target testing of the components suspected SPOIL RELI

NAP

NAA

DHN

DMO

MSA

DBP

0.9020 1.9754

0.5109 2.2445

0.1591 2.0459

1.8404 2.2416

0.9448 2.4176

0.4969 4.1647

Table 3. Results for synthetic samples by TFA (in mg/L) No.

NAP

NAA

DHN

DMO

MSA

DBP

1

True TFA

0.3840 0.388

1.6900 1.712

1.6880 1.774

0.0000 -0.001

0.9240 0.969

0.9410 1.080

2

True TFA

1.1520 1.201

0.3380 0.334

1.0130 1.054

0.0000 -0.003

3.6950 3.734

2.8230 2.807

3

True TFA

1.9200 1.957

1.0140 1.022

0.3380 0.337

0.0000 ~).007

2.3090 2.392

4.7050 4.799

4

True TFA

0.7680 0.700

1.2680 1.309

0.8440 0.834

2.4430 2.508

2.3090 2.364

1.5060 1.434

5

True TFA

1.9200 1.889

0.4230 0.418

0.6750 0.693

1.2210 1.252

1.8470 1.947

3.0110 3.056

6

True TFA

0.7680 0.791

1.6900 1.748

0.6750 0.627

1.2210 1.258

3.4640 3.430

2.2580 2.338

7

True TFA

1.1520 1.146

1.0140 1.046

1.6880 1.718

0.7630 0.780

2.3090 2.308

0.9410 0.922

8

True TFA

0.9600 0.882

0.3380 0.346

1.2660 1.325

3.0540 3.146

1.8470 1.887

2.8230 2.594

9

True TFA

2.4000 2.389

0.6760 0.665

0.4220 0.410

2.2900 2.316

2.3090 2.430

3.0110 3.277

10

True TFA

1.4400 1.361

0.8450 0.858

1.2660 1.296

2.7480 2.801

1.8470 1.954

3.3880 3.446

11

True TFA

0.7680 0.744

0.3380 0.375

0.8440 0.852

2.8180 3.890

4.6180 4.541

4.7050 4.472

12

True TFA

1.7280 1.716

1.1830 1.239

0.8440 0.886

2.7480 2.876

1.3860 1.378

0.0000 -0.437

13

True TFA

1.7280 1.748

1.5210 1.543

1.1820 1.301

0.9160 0.970

2.3090 2.323

0.0000 -0.439

327

Conclusion

References

Target factor analysis was successfully used to determine simultaneously the numbers, identities and concentrations of six aromatic compounds with overlapping UV spectra in mixtures. This work illustrates the potential usefulness of TFA in the direct analysis of the mixtures consisting of compounds similar to the aromatic compounds studied.

1. Malinowski ER, Howery DG (1980) Factor analysis in chemistry. Wiley, New York 2. Malinowski ER (1980) Anal Chim Acta 122:327 3. Malinowski ER (1981) Anal Chim Acta 133:99 4. Malinowski ER (1978) Anal Chim Acta 103:339 5. Malinowski ER (1977) Anal Chem 49:612 6. Malinowski ER (1987) Chemometrics 1 : 33 7. He Xiwen, Li Hong, Shi Huiming (1986) FENXI HUAXUE (China) 14 : 34

Fresenius J Anal Chem (1995) 351:327-330 - @ Springer-Verlag 1995

Comparison of two different derivatization procedures for the determination of urinary chlorophenol excretions Axel Kr~imer, Jiirgen Angerer Institute and Clinic of Occupational, Social and Environmental Medicine of the University of Erlangen-Ntirnberg, D-91054 Erlangen, Germany Received: 5 September 1994/Accepted: 11 October 1994

Abstract. A GC/MS method with enhanced sensitivity and specificity suitable for the determination of various chlorophenols in the urine of persons occupationally and environmentally exposed to diverse chlorinated aromatic hydrocarbons has been elaborated and compared with the method customarily used. After acid hydrolysis and steam distillation, followed by several clean-up steps, the chlorophenols have been derivatized with N-heptafluorobutyrylimidazole (HFBI), yielding ester derivatives. This procedure facilitates the detection of 3and 4-monochlorophenol, 2,4- and 2,5-dichlorophenol, 2,4,5and 2,4,6-trichlorophenol as well as 2,3,4,6-tetrachlorophenol down to 0.1-1 ~tg/1, depending on the number of chlorine atoms. A comparison to the commonly used derivatization procedure with diazomethane revealed, except for 2,4,5-trichlorophenol, satisfactory conformity of both techniques. Due to an improvement of the detection limit by a factor of five for the monochlorophenols, for the first time the quantification of 3-monochlorophenol and the identification of 2-monochlorophenol as constituents of human urine have been possible as HFBI-derivatives. The excretion of mono-, di-, tri- and tetrachlorophenols in the urine of the general population could be confirmed.

Introduction The determination of several mono-, di-, tri- and tetrachlorophenols in the urine of the general population was the unexpected result of two large scaled studies performed between 1989 [1] and 1992 [2]. The stress of the general population caused by these chlorophenols (CPs) is comparable with the exposure to pentachlorophenol, a substance extensively used as an indoor wood preservative in Germany until its ban in 1989. Although these findings were confirmed by subsequent works,

Correspondence to: J. Angerer

the results should be verified by applying an analytical procedure with improved detection limits. Those can 'be achieved by a modified derivatization procedure followed by GC/MS analysis. An additional gain in sensitivity could be expected compared to the mass selective detector (GC/MSD) routinely used in our laboratory. Within the scope of the present study, the urinary excretion of 3- and 4-monochlorophenol (MCP), 2,4- and 2,5-dichlorophenol (DCP), 2,4,5- and 2,4,6-trichlorophenol (TCP) as well as 2,3,4,6-tetrachlorophenol (TECP) was recorded. Prior to analysis, the chlorophenols were either derivatized using diazomethane (DAM), according to the standard procedure of this laboratory, or with N-heptafluorobutyrylimidazole (HFBI).

Material and methods Collective Urine samples from 16 male persons were collected postshift and stored frozen. The workers were occupied in different fields of technical attendance tasks in an incineration plant.

Reagents N-heptafluorobutyrylimidazole was purchased from Pierce, Rockford, IL, USA. All other chemicals used were of the best available analytical grade and supplied from Merck:, Darmstadt, FRG.

Analysis of HFBI derivatives HFBI derivatives were measured using a GC/MS system from Hewlett Packard (Palo Alto, CA, USA) consisting of a HP 5890 Series II gas chromatograph connected to a HP 5989 A mass spectrometer.

GC conditions. Capillary column: HP Ultra 2, 25 m x 0.2 mm x 0.33 gin. Temperatures: injector: 280°C, column:: 70°C, 3 ° C/ rain to 150 °, 50°C/rain to 280°C, isothermal for 5 rain. Carrier gas: helium 5.0, inlet pressure 15 psi, splitless injection of 1 gl. MS conditions. Temperatures: ion source: 200°C, quadrupole 100°C, interface: 300°C. Ion source pressure: 6 x 10-6 torr. Ionization: EI 70 eV, multiplier 2600 V. Mode: selected ion monitoring.

Analysis of methylether derivatives Methylether derivatives were determined with a HP 5890 Series II gas chromatograph equipped with an automatic liquid