Anal. Chem. 1981,
However, the extended periods of preservation, acid and dichromate should be used and a determination of total mercury can be obtained with a fair amount of accuracy since losses would be minimized. However, the original speciation information for the sample is no longer determinable unless analysis is carried out immediately after preservation.
ACKNOWLEDGMENT We wish to thank Riley Chan and Debbie Zahnale fior carrying out preliminary studies on this research. LITERATURE CITED (1) Trakhtenberg, I. M. ”Chronic Effects of Mercury on Organisms” (translated from Russian). Geographic Health Studies Program of the J. E. Fogaity Interriatlonal Center for Advanced Study In the Health Solenceti, US. Department of Health, Education and Welfare Public Health Service National Institutes of Health, 1974. (2) Ure, (4. M. Anal. Chlm. Acta 1975, 76, 1-26. (3) Hawley, J. E.; Ingle, J. D., Jr. Anal. Chem. 1975, 47, 719-723. (4) Chllov, S. Talilnta 1975, 22, 205-232. (5) Rodriguez-Varquez, J. A. Talanta 1978, 25,299-310. (6) Bachta, Carl A.; Llsk, Donald J. Anal. Chem. 1971, 43, 950-952. (7) Talml, Yair Anal. Chlm. Acta 1975, 74, 107-117. (8) Becknell, D. E.; Marsh, R. H.; Allle, W., Jr. Anal. Chem. 1971, 43,
1230-1233. (9) Farey, B. J.; Nelson, L. A.; Rolph, M. G. Analyst(London) 1978, 103, 565-1580. (10) Omang, Sverre H. Anal. Chim. Acta 1971, 53. 415-420. (11) Velghe, N.; Cempe, A.; Claeys, A. At. Abs. News/. 1978, 77, 37-40. (12) Feldrnan, Cyrus Anal. Chem. 1974, 46, 1606-1609. (13) El-Aw’ady, Abbas, A.; Miller, Robert B.; Carter, Mark J. Anal. Chem. 1976, 48. 110-116. (14) Jlrka, Andrea M.; Carter, Mark J. Anal. Chem. 1978, 50, 91-94.
53,2309-2313
2309
(15) “Methods for Chemical Analysis of Water and Wastes”; U.S. Envlronmental Protection Agency; Cincinnati, OH, 1974;pp 134-136. (16) Matsunaga, Kazuyoshl T.; Ishlda, T.; Oda, T . Anal. Chem. 1976, 48, 1421-1423. (17) Goulden, P. D.; Afghan, 8. K. ”An Automated Method for Determining Mercury In Water”, Technical Bulletin No. 27;Inland Waters Branch, Department of Energy, Mines and Resources: Ottawa, Canada, 1970 p 21. (18) Klemenlj, A. M.; Kloosterboer, J. G. Anal. Chem. 1976, 48, 575-576. (19) Agemlan, Halg; Chau, A. S. Y. Anal. Chlm. Acta 1975, 75, 297-304. (20) Magos, L. Ana/yst(London) 1971, 96, 847-853. (21) Magos, L. J. Assoc. Off. Anal. Chem. 1972, 55, 966-971. (22) Toffalettl, John; Savory, John Anal. Chem. 1975, 47, 2091-2095. (23) Chrlstmann, D. R.; Ingle, J. D., Jr. Anal. Chim. Acta 1976, 86, 53-62. (24) Olson, K. R. Anal. Chem. 1977, 49, 23-25. (25) Oda, C. E.; Ingle, J. D., Jr. Anal. Chem. 1981, 53, 2030-2033. (26) Glovanolhlakubczak, Terasa; Greenwood, Michael R.; Smith, J. C.; Clarkson, T. W. Clln. Chim. ( Winston-Salem, N . C . ) 1974, 20, 222-229. (27) Mueller, Wllllam M., Blackledge, James P., Libowltz, George G., Eds., “Metal Hydrldes”; Academic Press: New York, 1966;p 791. (28) Kamps, Laverne R.; Carr, Richard; Miller, Hanford Bull. Envlron. Contam. roxicol. 1972, 8, 273-279. (29) Rivers, J. B.; Pearson, J. E.; Shultz, C. D. Bull. Environ. Contamin. Toxicol. 1972, 8 , 257-266. (30) WestoijG, G. “Chemical Fallout”; Miller, M. W., Berg, G. G., Eds.; Charles C. Thomas: Springfield, IL, 1969;pp 75,360. (31) Goulden, P. D.; Anthony, D. H. J. Anal. Chim. Acta 1980, 120, 129-139. (32) Katz, Sidney A. Am. Lab. (FairfleM, Conn.) 1979, 1 7 , 44-52. (33) Qulnby-Hunt, Mary S. Am. Lab. (Falrflekj, Conn.) 1978, 70, 17-37.
RECEIVED for review June 22,1981. Accepted September 21, 1981. Presented in part at the 62nd Canadian Chemical Conference, Vancouver, B.C., 1979.
High-,PerformanceThin-Layer Chromatography of Metal Tet raiphenylporphyrin Chelates Koichi SialtOh, Masaru Kobayashi, and Nobuo Surukl” Department of Chemistry, Faculty of Science, Tohoku University, Sendai, Mbagi 980, Japan
The tetraphenyiporphyrln (TPP) chelates of Mg(II), NI(II), Cu(II), Zn(II), Cd( II), Mn(III), and Fe( 111) have been chromatograplhed on cellulose, silica gel, and CB-bonded and C18-bondedslllca thin layers with various organic developing solvents. The separation between the Mg(I1) and Cd(I1) chelates Is not successful wlth thin-layer systems other than cellulose. Wlth thls exceptlon, every chelate pair can be resolved on C,,-bonded slllca layer. Mutual separatlon of seven metal TPP chelates Is demonstrated on C18-bonded slllca layer by a two-dimensional developlng method In which the 20:80 ( v h ) acetone-propylene carbonate mlxture and acetone awe used as the prlmary and the secondary developers, resipectlvely.
Although a great number of liquid chromatographic data have, to data, been reported for a variety of compounds, metal chelates hiave been dealt with in few papers. A very small number of liquid chromatographic studies were carried out on the metal chelates of common chelating ligands, such as @-diketones(1,2),dithizone (3),and diethyldithiocarbamate (4). Considering that the chromatographic behavior of metal chelates depends, in general, on the properties of both the chelating ligand and chelated metal ion in addition to the properties of stationary and mobile phases, systematic study 0003-2700/81/0353-2309$01.25/0
has to be made on the chelates of various types of chelating agents with a given central metal and on the chelates of one or a series of chelating agent(s) with different central metals. In our laboratory, a series of P-diketones and their metal(I1,III) chelates have been investigated in adsorption and size-exclusion chromatographic systems from viewpoints of the effects of ligand, metal ion, stationary phase substance, and mobile phase solvent (5-9). Liquid chromatography has been used as a powerful tool for separation in the field of porphyrin chemistry. Columns packed with silica gel (IO),alumina (11),calcium carbonate (12),or magnesium silicate-cellulose mixture (13),paper (Id), and thin layer of silica gel or alumina (15, 16) have been effectively used for the purification of synthetic porphyrin compounds or separation of naturally occurring metalloporphyrins. However, systematic investigation of chromatography for these compounds has hardly been carried out from the viewpoints of the effects of stationary phase substance and mobile phase solvent. In addition, most of the papers so far published have dealt with porphyrin chelates of limited metal ions, for example, chelates of magnesium or iron, which are known as chlorophyll or hemin. Articles dealing with various metal chelates of a certain porphyrin are rarely found. In the present work, metalloporphyrins have been taken up as the metal chelates of interest, by considering (1) the @ I981 American Chemical Society
2310
ANALYTICAL CHEMISTRY, VOL. 53, NO. 14, DECEMBER 1981
Table I. R f Values of the Metal Chelates of Tetraphenylporphyrin on Cellulosea with Different Single-Component Developers at 25 "C Rf
developer solvent hexane cyclohexane carbon tetrachloride
a
MgTPP
NiTPP
CuTPP
ZnTPP
CdTPP
MnTPP
FeTPP
H,TPP
0.0
0.23 0.49 0.96
0.02 0.08 0.79
0.16 0.37 0.95
0.01 0.03 0.1 1
0.05 0.1 3 0.94
0.16 0.41
0.0 0.0
0.09 HPTLC plate cellulose (Merck no. 5787).
0.53 0.94
0.95
Table 11. R f Values of the Mtal Chelates of Tetraphenylporphyrin on Silica Gela with Various Single-Component Developers at 2 5 "C Rf
a
developer solvent
MgTPP
NiTPP
CuTPP
ZnTPP
CdTPP
MnTPP
FeTPP
H,TPP
hexane ( O . O 1 ) b cyclohexane (0.04) carbon disulfide (0.15) carbon tetrachloride (0.18) m-xylene (0.26) toluene (0.29) benzene (0.32) diethyl ether (0.38) dichloromethane (0.42)
0.0 0.0
0.01
0.01 0.02 0.33 0.49
0.0
0.0 0.0
0.0 0.0
0.0 0.0
0.02
0.0 0.0 0.0
0.03
0.0
0.05 0.83 0.89 0.88 0.83 0.89
0.01 0.03 0.83 0.89 0.88 0.85 0.90 HPTLC plate silica gel 60 (Merck no. 5631).
0.03 0.29 0.47
0.0
0.02 0.0 0.04 0.0 1.0 1.0 0.81 0.82 0.0 1.0 1.0 0.85 0.89 0.0 0.95 0.96 0.80 0.88 0.0 0.83 0.83 0.85 0.83 0.05 0.93 0.92 0.85 0.89 0.01 Solvent strength parameter, E ' , by Snyder ( 2 4 ) .
importance of metalloporphyrins in wide field of chemistry including biological science and petroleum industry, (2) remarkably high stability of metalloporphyrins, and (3) quite few chromatographic data for these compounds in publications. This paper describes the high-performance thin-layer chromatography (HPTLC) of metal chelates of 5,10,15,20tetraphenylporphyrin (TPP) which is one of the typical synthetic porphyrins. Only two publications on TLC of metalTPP chelates were reported (17,18). In both of these articles, the stationary phase materials were limited to silica gel and alumina, and a few kinds of solvent mixture were used as the mobile phases. According to the R, data given in these articles, we cannot expect satisfactory resolution among several metal-TPP chelates. Many more TLC studies are required to realize more successful separation of metal-TPP chelates and to evaluate TLC behavior of these compounds.
In this work, chelating agent TPP and its metal chelates of Mg(II), Ni(II), Cu(II), Zn(II), Cd(II), Mn(III), and Fe(II1) have been chromatographed. Four kinds of high-performance thin-layer stationary phases are chosen by cpnsidering the different separation modes with cellulose and silica gel for normal-phase distribution and two kinds of alkylated silicas for reversed-phase distribution. Different types of mobile phase solvents are carefully chosen for comparison. EXPERIMENTAL SECTION Materials. The free base form of TPP (hereafter abbreviated as H,TPP) was prepared by the method of Adler and co-workers (19), in which benzaldehyde reacted with pyrrole in refluxing propionic acid. The purification of HzTPP was carried out according to the method by Barnett et al. (20). The TPP chelates of Mg(II), Mn(III), Fe(III), Ni(II), Cu(II), Zn(II), and Cd(I1) (hereafter abbreviated as MgTPP, MnTPP,
0.0 0.0 0.0
0.83 0.01
0.0 2
FeTPP, NiTPP, CuTPP, ZnTPP, and CdTPP, respectively) were prepared by the reaction of H2TPP and the chloride of corresponding metal in refluxing N,N-dimethylformamide (21). Identification of the products was carried out according to the C, H, and N analysis and UV-visible spectral studies (22, 23). The TPP chelate of every divalent metal ion was identified as a compound in the form of 1:l complex of the metal ion and TPP ligand, and the MnTPP and FeTPP were identified as those in the form of 1:1:1 complexes of the metal ion, TPP, and chloro anion. HPTLC Plates. Four kinds of precoated HPTLC plates were commercially obtained from Merck (Darmstadt, West Germany): (a) cellulose (Merck product no. 5787), (b) silica gel 60 (no. 5631), (c) RP-8 FZMs(no. 13725),and (d) RP-18 FZMs(no. 13724). Each plate has a chromatographic layer of 10 X 10 cm wide and 200 pm thick. The silica gel plate was activated, prior to use, by heating at 110 OC for 1h and then cooling in a silica gel desiccator for 2 h. The plates other than silica gel were used without preliminary treatment. Solvents. The solvents used were purified by distillation before use. Procedure. Chromatography was carried out in a thermostatically controlled room at 25 "C. The sample solution of HzTPP or its metal chelate was prepared in chloroform at a concentration of about 1 mg/mL. In the case of NiTPP, the concentration of the sample solution was lower than 0.5 m g / d because of its lower solubility. A 0.5-pL portion of each sample solution was put on the start line placed at 15 mm from an edge of the chromatographic plate. In the case of NiTPP, the 0.5-flLamounts of sample solution were applied twice. The chromatogram was developed until the solvent front was 75 mm from the origin by means of a sandwich method with a covering glass plate placed 1.6 mm apart from the TLC plate. Every spot on the chromatogram was easily detected owing to the characteristic intense color of each TPP chelate in day light. Under ultraviolet light (254 and 356 nm), MgTPP, ZnTPP, CdTPP, and HzTPP were fluorescent. RESULTS AND DISCUSSION Tables I-IV show the R, values of HzTPP and its metal chelates on cellulose, silica gel, and C8-bonded and C18-bonded silicas with various single-component developers, respectively. The chromatographic behavior of those compounds on respective HPTLC plates is detailed below. (a) On Cellulose. Most of the compounds showed short migration (RI < 0.2) with hexane. The compounds other than MgTPP, MnTPP, and ZnTPP moved nearly to the solvent
ANALYTICAL CHEMISTRY, VOL. 53, NO. 14, DECEMBER 1981
2311
___-
Table 111. R f Values of the Metal Chelates of Tetraphenylporphyrin on C,-Bonded Silicaa with Various Single-ComponenF Developers at 25 "C
Rf
a
developer sollvent
MgTPP
NiTPP
CuTPP
ZnTPP
CdVP
MnTPP
FeTPP
H,TPP
methanol ethanol 1-propanol 2-propanol 2-butanol acetonitrile propylene carbonate acetone N,N-dimethylforman n ide carbon disulfide dichloromet hane pyridine
0.44 0.59 0.97 0.79 0.89 0.24 0.25 0.81 0.87 0.96 0.91 0.95
0.34 0.53 0.85 0.77 0.89 0.20 0.31 0.80 0.87 0.97 0.96 0.94
0.33 0.51 0.84 0.73 0.87 0.19 0.24 0.77 0.85 0.97 0.95 0.94
0.63 0.70 0.97 0.89 0.95 0.4 5 0.57 0.87 0.89 0.95 0.95 0.96
0.44 0.58 0.96 0.80 0.89 0.23 0.25 0.81 0.86 0.97 0.93 0.94
0.1 5 0.93 1.0 0.95 0.96 0.34 0.36 0.61 0.24 0.24 0.93 1.o
0.12
0.44 0.58 0.95 0.79 0.87 0.23 0.24 0.81 0.85 0.97 0.93 0.94
0.73 0.99 0.83 0.91 0.33 0.39 0.85 0.71 0.96 0.95 0.95
HPTLC plate RP-8 F,,, (Merck no. 13725).
Table IV. R f Values of the Metal Chelates of Tetraphenylporphyrin on C,,-Bonded Silicaa with Various Single-Component Developers at 25 "C
Rf
a
developer solvent
MgTPP
NiTPP
CuTPP
ZnTPP
CdTPP
MnTPP
FeTPP
H,TPP
meth ano 1 etlhanol 1-propanol 2-]propanol 2- butanol acetonitrile propylene carbonate acetone N,N-dimethylformamide carbon disulfide 1,4-dioxane pyridine
0.11
0.05 0.1 5 0.41 0.37 0.63 0.04 0.1 3 0.67 0.70 0.98 0.93 0.95
0.04 0.13 0.35 0.31 0.56 0.04 0.07 0.61 0.65 0.97 0.95 0.94
0.35 0.48 0.78 0.72 0.89 0.21 0.36 0.82 0.80 0.95 0.97 0.95
0.11 0.24 0.57 0.45 0.71 0.11 0.13 0.73 0.73 0.94 0.94: 0.93
0.21 0.52 0.99 0.91 0.96 0.20 0.27 0.64 0.13 0.13 0.96 0.96
0.13 0.27 0.93 0.60 0.80 0.13 0.21 0.79 0.67 0.92 0.96 0.95
0.11 0.24 0.57 0.45 0.69 0.11 0.13 0.73 0.73 0.91 0.93 0.92
0.23 0.58 0.44 0.71 0.1 2 0.13 0.70 0.71 0.95 0.93 0.94
HPTlLC plate RP-18 F,,,, (Merck no. 13724).
0.0
0.2 0.4 0.6 0.8 1.0 Volume fraction of carbon tetrachloride
Flgure 1. Migration ( 4 )of metal TPP chelate vs. volume fraction of carbon tetrachloride in a mixture of hexane and carbon tetrachloride, HPTLC plate cellulose (Merck no. 5787). Compounds: ( 0 )MgTPP, ( 0 )NiTPP, (A)CuTPP, ( 0 )ZnTPP, (0)CdTPP, (0)MnTPP, (A) FeTPP, (0)H,TPP.
front with carbon tetrachloride. Every compound gave a diffused spot on the chromatogram developed even withi a variety of solvent, and this resulted in lowered resolution on the present system. For example, a considerable difference in Rf values with carbon tetfachloride is observed for ZnTPP (Rf = 0,7!3) and NiTPP (Rj= 0.94), but complete separation is unsuccessful. In Figure 1the Rf values of metal TPP chelates and H,TPP are plotted against the composition of the hexane-carbon tetrachloride binary mixture used as developing solvent. The migration sequence of the interesting compounds with the equivolume mixture of this binary developer is CuTPP > NiTPP =' CdTPP N HzTPP > FeTPP > ZnTPP > MnTPP > MgTPP, and the group separation is only successful as
Flgure 2. R, value of metal TPP chelate vs. solvent strength (to) of developer, HPTLC plate silica gel 60 (Merck no. 5631). The marks refer to the compounds as in Figure 1. follows: (1)CuTPP, NiTPP, CdTPP, and H2TPP, (2) FeTRP and ZnTPP, and (3) MnTPP and MgTPP. It is interesting, however, that CdTPP and MgTPP are readily resolved on cellulose, this must be compared with the migration sequence on another stationary phase in which these chelates show quite similar migration tendency. (b) On Silica Gel. Figure 2 shows the relation of the R, values of the metal TPP chelates and the Snyder solvent strength parameter, t o , for the developing solvents listed in Table 11. The t o values on alumina (24) are applied to the present silica gel system, because the t o values on silica gel have not been given for every solvent of the present interest. As a general trend, most of the metal TPP chelates show larger R, values with developing solvent of larger E' value. The TPP compounds are classified apparently into the following three groups: (1)NiTPP and CuTPP, (2) MgTPP, CdTPP, ZnTPP,
2312
* ANALYTICAL CHEMISTRY,
VOL.
53, NO. 14, DECEMBER 1981
1.0,
1
Y . l
0.0 02 0.4 06 0.8 Voluwe f r x t i o n of dichloromethane
Flgure 3. Migration (R,) of metal TPP chelate vs. volume fraction of dichloromethane in the mixture of carbon tetrachloride and dichloromethane, HPTLC plate silica gel 60 (Merck no. 5631). The marks refer to the compounds as in Figure 1.
melhanol
1.0
c
Y
0.0
10
/I
02 04 06 OB 10 Volume f r a d i m of propylene carbanate
Migration (R,) of metal TPP chelate vs. volume fraction of propylene carbonate in the mixture of acetone and propylene carbonate, HPTLC plate RP-18 F254s(Merck no. 13724). The marks refer to the compounds as in Figure 1. Figure 5.
pared with those on a C8-bonded plate with corresponding solvents, where RM is calculated from R f by the following equation: RM = log ( 1 / R f - 1) (1)
RM is related to the distribution coefficient, K , and further to the free energy change, AE, for the solute distribution between mobile and stationary phases RM = log ( A , / A , ) f log K (2)
I 2
O'OI
-1.0
I
- 1.0
0.0
RM, 8
Correlation between the R, values of a metal(I1)TPP chelate or H,TPP on Cia-plate(R,.,,,) and C,-plate (R,,,)with a given developer solvent, HPTLC plates RP-18 F254s(Merck no. 13724) and RP-8 F254s (Merck no. 13725)as the CIS- and C,-plates, respectively. Figure 4.
and H,TPP, and (3) FeTPP and MnTPP. The compounds assigned to the fiist group show high mobility on silica gel even with such weak solvents as carbon disulfide and carbon tetrachloride. In contrast, the last two compounds show very low mobility with a variety of developer solvents. The strong adsorption of FeTPP and MnTPP onto silica gel is presumably due to higher polarity of these chelates with tervalent state of metals. I t is remarkable that FeTPP and MnTPP is resolved specifically with ethyl ether. Mutual separation of foregoing three groups of compounds was easily achieved with an appropriate single-component developing solvent, whereas intragroup separation was unsuccessful. When the binary mixture of carbon tetrachloride and dichloromethane is used as a developing solvent, the migration of the TPP chelates is governed effectively with the solvent composition as shown in Figure 3, but, in general, the resolution was not highly improved by the present binary developer, except that ZnTPP was separated from other second group chelates with 8020 (vol/vol) mixture of carbon tetrachloride and dichloromethane. (c) On Alkylated Silicas. On the plates of the C8-bonded and C18-bonded silicas, most of the metal TPP chelates migrated nearly to the solvent front with such developing solvents as carbon tetrachloride, dichloromethane, and pyridine. The Rf value for a compound is larger on a C8-bonded plate than on a C18-bonded plate. This tendency was not always consistent in the case of FeTPP and MnTPP. In Figure 4 the RM values of metal(I1) TPP chelates and H2TPP on the (&bonded plate with several developing solvents are com-
where (ASIA,) is relative amount of the stationary phase to the mobile one. The RM vs. RM plot for the metal(I1) TPP chelates and HzTPP on the CIS-and C8-bonded plates shows a linear relationship in every solvent system (Figure 4). Since (ASIA,)is approximately constant on each chromatographic plate with a given solvent, the observed linear relationship implies that the free energy change for the distribution of a metal(I1) TPP chelate or H2TPP between C18-bondedphase and a given mobile phase can be correlated simply to that between C8-bonded phase and the same mobile phase. When the separation of two compounds, 1 and 2, is taken into account, a simple modification of eq 2 gives RM,l - R M ,=~ IOg K1 - log Kz
RM,1 - RM,Z = 1%
0112
(4)
where subscripts 1 and 2 refer to the compounds 1 and 2 , respectively, and CY is the separation factor between these two compounds. A comparison between the separation factor on a C18-bonded plate and a (&-bonded one is shown as (log
cyl2)
on C18-plate
(log a12)on C8-plate
- (RMJ - RM,Aon C18-plate ( 5 ) (RM,1- RM,2) on C8-plate
The right-hand side of the above equation corresponds to the slope in Figure 4. The slope observed in every solvent system is larger than unity, which implies that the separation factor for a pair of compounds on a (&-bonded phase is larger than that on the C8-bonded one for a given developing solvent. When the binary mixture of acetone and propylene carbonate is used as developing solvent, the Rf values of metal TPP chelates on a C18-bondedsilica layer varies with a change in the composition of mixture as shown in Figure 5. The migration sequence for the chelates depends on the composition of the mixture. For example, the Rf sequence observed with the 20230 (v/v) acetone-propylene carbonate mixture is MnTPP > ZnTPP > FeTPP > MgTPP N H2TPP N CdTPP > NiTPP > CuTPP, and this must be compared with the case of single developing solvent, acetone: ZnTPP > FeTPP > HzTPP N CdTPP N MgTPP > NiTPP N MnTPP > CuTPP. These facts show that the resolution among these
Anal. Chem. 1981, 53, 2313-2318 F
I
7
2313
further much better resolution has been obtained by the secondary development in another direction with acetone. MgTPP and CdTPP have still shown a blended zone on the chromatogram.
LITERATURE CITED Uden, Peter C.; Blgley, Imogene E.; Walters, Frederick H. Anal. Chlm. Acta 1978. 100. 555-561. Huber. J. F. K.: Kraak. J. C.: Veenlna, Hans Anal. Chem. 1972, 44, 1554-1 559. Henderson, D. E.; Chaffee, R.; Novak, F. P. J. Chromatogr. Sci. 1981, 19, 79-83. Uden, Peter C.; Bigley, Imogene E. Anal. Chim. Acta 1977, 94, 29-34 _
Saitoh, Koichi; Nobuo Suzuki J . Chromatogr. 1974, 92, 371-379. Suzuki, Nobuo; Saitoh, Koichi; Shibukawa, Masami J . Chromatogr. 1977, 138,79-87. Saltoh, Kolchl; Suzuki, Nobuo Bull. Chem. SOC. Jpn. 1978, 51, 116-120. Suzuki, Nobuo; Suzuki, Junichi; Saitoh, Koichi J . Chromatogr. 1079, 177, 166-169. Saitoh, Koichi; Suzuki, Nobuo Anal. Chem. 1980, 52, 30-32. Hanson, Louise K.; Gouterman, Martin; Hanson, Jonathan C. J . Am. Chem. SOC. 1973, 95, 4822-4829. Adler, Alan D.; Longo, Frederick R.; Varadi, V. Inorg. Synth. 1978, 16, 213-220. Felton, Ronald H.; Linschitz, Henry J . Am. Chem. SOC. 1988, 88, 1113-11 16. Wei, Peter E.; Corwln, AlsoDh H.; Arellano, Robert J . Org. Chem. 1962, 27, 3344-3346. Chu, Tseng C.;Chu, Edith J-H. J . Blol. Chem. 1955, 212, 1-7. Chu, Tseng C.; Chu, Edith J.-H. J . Chromatogr. 1976, 28, 475-478. Lamson, Davis W.; Coulson, Andrew F. W.; Yonetani Takeshi Anal. Chem. 1979, 45, 2273-2276. Sato, Mltsuo; Kwan, Takao Chem. Pharm. Bull. 1972, 20, 840-641. Hui, K. S.;Davis, 9. A.; Baulton, A. A. J . Chromatogr. 1975, 175, 581-586. Adier, Alan D.; Longo, Frederick R.; Finavelli, John D.; Goldmackier, Joel; Assour, Jacques; Korsakoff, Leonard J . Org. Chem. 1967, 32, 476. Barnett, Graham H.; Hudson, Mervyn F.; Smith, Kevin M. J . Chem. Soc. Perkin Trans. 11975, 1401-1403. Adler, Alan D.; Longo, Frederick R.; Kampas, Frank; Kim, Jean J . Inorg. Nucl. Chem. 1970, 32, 2443-2445. Albers, V. M.; Knorr, H. V. J . Chem. Phys. 1941, 9 , 497-502. Dorough, G. D.; Miller, J. R.; Huennekens, Frank M. J . Am. Chem. SOC. 1951, 73,4315-4320. Snyder, L. R. "Modern Practice of Liquid Chromatography"; Kirkland, J. J., Ed.; Wiley: New York, 1971; Chapter 4.
Flgure 6. Twodimensional HPTLC separation of metal TPP chelates, HPTLC plate RP-18 F254s(Merck no. 13724). Developers: I (primary), acetone-propylene carbonate (20:80(v/v)) (2-fold development); I1 (secondary),acetone (+, origin; F, solvent front).
compounds can be regulated by changing the composition of the above solvent mixture. Choice of Chromatographic System for Mutual Separation of Metal TPP Chelates. The separation efficiency of these chelates is quite dependent on the stationary phase substance as well as mobile phase solvent, but the mutual separation of metal TPP chelates with different central metals is unsuccessful with either cellulose or silica gel. For example, CuTPP amd Ni'I'PP cannot be completely resolved on either of these stationary phases, and MnTPP and FeTPP show the same migration behavior on silica gel unless ethyl ether is mixed with the developing solvent. On the contrary, alkylated silica, such as the (&-bonded one, is quite effective for the mutual separation of metal TPP chelates of interest. The migration, sequence for the metal TPP chelates on C18-bondled silica is analogous to that on C8-bonded silica, but a larger separation factor for a given chelate pais can be expected on C18-bondedsilica rather than on the C8-bonded one, provided the same solvent is used as the developer. A demonstration of two-dimensional HPTLC separation of seven imetal TPP chelates on a C18-bonded silica layer is shown in Figure 6. These chelates have been primarily resolved into four solute zones by %fold development with the 20:80 (v/v) mixture of acetone and propylene carbonate, and
RECEIVED for review May 15,1981. Accepted September 16, 1981.
Comimsri Orifice Flow for Precision Gas Mixing Wm. Dean WaYlace, * Justin S. Clark, and Christopher A. Cutler' Primary Children's Medical Center, 320 72th A venue, Salt Lake City, Utah 84 103
A new approach is described for dynamlc on-site mixing of gases, which utilizes the princlple of sequential flow of gases, under choked conditions, through a common orlflce. Practical application of the princlple is accomplished by mlcroprocessor control of valve open-times determined by calculations based on the desired gas fractions and the gas flow ratios through the commlon orifice of each gas with respect io the other gases In the mlxture. The resultant varlable gas mlxtures can be used In1 lndustrlal, medlcal, production, and research laboratories. Evaluation of the instrument demonstrates the accuracy to be better than f O . i % absolute for a three-gas system of nitrogen (N2), oxygen (02),and carbon dioxide
(cod. Present address: Medicor,
Inc., Salt Lake City, UT 84103.
Numerous applications exist for accurate, known gas mixture compositions. For example, variable known gas mixtures are needed for instrument calibration of the following: infrared analyzers, gas chromatographs, mass spectrometers, and chemical electrode transducers such as medical blood-gas electrodes. Other applications include regulation of environmental chambers, semiconductor manufacture, vehicle emission control, air pollution abatement, laser mixtures, and uses in industrial, medical, production, and research laboratories. The above list plus other demands for variable, absolute gas fraction compositions has stimulated the growth of a large industry for the preparations of such mixtures. The complexity and safety of this preparation have resulted in several solutions, the most common being a central preparation plant with high-pressure metal cylinders serving as transport containers. The two most common gas mixture techniques
0003-2700/81/0353-2313$01.25/00 1981 American Chemical Society
