Potential Extension to Other Elements. Other investigators have shown that Bi, Ge, and Sn can be volatilized from acid solution using NaBH4 to generate their hydrides (10-12,21). The authors of this article have not studied the behavior of these elements in the depth necessary to prove that they can all be determined in foods. However, if these elements are not lost during sample oxidation, it is likely that quantitative measurements may be obtained. Analytical calibration curves were obtained using the semiautomatic hydride generator for Bi, Hg, and Sn. BiH3 was quantitatively volatilized from a solution of 30% (v/v) HC1 and 5% (v/v) HzS04. The sensitivity was 0.71 A/pg Bi for the 223.1-nm resonance line using an EDL primary source (8watt, 0.7-nm band pass). Hg was quantitatively generated as the metal from a solution of 30% (v/v) HC1 and 5% (v/v) H2S04. The sensitivity, using a 10-cm cell in place of the hydrogen diffusion flame, was 0.55 A/pg at the 253.7 nm line. An HCL operated a t 6 mA was the primary source (0.7-nm band pass). It should be noted that Hg was generated as the atomic vapor from acid solutions other than H2SO4, or HC104. Sn HCl-HZSOd mixtures, e.g., "03, was generated as SnH4 from 5% (v/v) HC104 using NaBH4 in 1%(w/v) NaOH. The sensitivity was approximately 1.75 A/pg using an EDL operated a t 8 watts (224.6 nm, 0.7-nm band pass). Of the seven elements investigated, only Sn was affected appreciably by variations in acid concentration. This observation has been reported previously (11, 21 1.
CONCLUSION We have shown that the determination of As, Sb, Se, and T e in foods utilizing a semiautomatic hydride generator is accurate, precise, and sensitive. As with fully automated analytical instruments, the semiautomatic hydride generator affords relative freedom from analyst carelessness, relatively high speed of analysis, and excellent precision. The detection capabilities are comparable to those obtainable via instruments based on peristaltic pumping systems which are considerably more complex and costly than the semiautomatic hydride generator described in this paper.
ACKNOWLEDGMENT The authors express their gratitude to Charles M. Berry, Warren Syner, and William A. Malatesta for their help in the design and construction of the hydride generator and flame shield; to James T. Tanner and Melvin Friedman for the confirmatory neutron activation analyses; to Myron Schachter for the confirmatory spectrophotometric and fluorometric analyses; and to the chemists who participated in the method reliability testing: T. C. Raines, M. Epstein, National Bureau of Standards; A. Sulek, National Canners Association; H. Miller, J. Williams, and R. Abel, FDA Baltimore District Laboratory; and A. Zander and G. Anderson, University of Maryland, Department of Chemistry.
LITERATURE CITED (1)I. M. Kolthoff, P. J. Elving, and F. H. Stross, "Treatise on Analytical Chemistry", Part 111, Vol. 2,Wiley-lnterscience, New York, 1971,p 92. (2) I. M. Kolthoff, P. J. Elving, and E. B. Sandell, "Treatise on Analytical Chemistry", Part 11, Vol. 7,Wiley-Interscience,New York, 1961,p 167. (3)G. D. Christian and F. J. Feldman, "Atomic Absorption Spectroscopy", Wiley-Interscience,New York, 1970,Chap. 22. (4)H. L. Kahn and J. E. Schallis, At. Absorpt. Newsl., 7 (l),5 (1968). (5)A. Ando, M. Suzuki, K. Fuwa. and B. L. Vallee, Anal. Cbem., 41, 1974 (1969). (6)W. Holak, Anal. Chem., 41, 1712 (1969). (7)R . M. Orheim and H. H. Bovee, Anal. Chem., 46,921 (1974). (8)F. J. Fernandez and D. C. Manning, At. Absorpt. News/.. 10 (4),86 (1971). (9)D. C.Manning, At. Absorpt. Newsl., 10 (6),123 (1971). (10)F. J. Schmidt and J. L. Royer, Anal. Lett., 6, 17 (1973). (11) F. J. Fernandez, At. Absorpt. News/., 12 (4),93 (1973). (12)E. N. Pollock and S . J. West, At. Absorpt. Newsl., 12 (l),6 (1973). (13)E.J. Schmidt. J. L. Royer, and S. M. Miur, Anal. Lett., 8, 123 (1975). (14)K. T. Kan, Anal. Lett., 6, 603 (1973). (15)E. F. Dalton and A . J. Malanoski, At. Absorpt. Newsl., 10 (4),92 (1971). (16) G. F. Smith, "The Wet Chemical Oxidation of Organic Compositions Employing Perchloric Acid", G. Frederick Smith Chemical Co., Columbus, Ohio, 1965. (17)NBS Publication, "NBS Standard Reference Materials", updated 10/1/ 74,Biological Materials, U S . Dept. of Commerce, Washington, D.C. (18)E. Orvini. T. E. Gillis, and P. D. LaFleur, Anal. Cbem., 46, 1294 (1974). (19)G. H. Morrison and N. M. Potter, Anal. Cbem., 44,839 (1972). (20)R. A. Nadkarni and G. H. Morrison, Anal. Cbem., 45, 1957 (1973). (21)K. C.Thompson and D. R. Thomerson, Analyst, 99,595 (1974).
RECEIVEDfor review April 10, 1975. Accepted September 12, 1975.
Matrix Effects in the Determination of Copper and Manganese in Biological Materials Using Carbon Furnace Atomic Absorption Spectrometry Johanna Smeyers-Verbeke, Yvette Michotte, Pierre Van den Winkel, and Desire L. Massart * Vrije Universiteit Brussel, Farmaceutisch Instituut, Paardenstraat 67, B- 1640 Sint Genesius Rode, Belgium
A systematic investigation of the interference of 1 to 1000 ppm of the chlorides, nitrates, phosphates, and sulfates of H, Na, K, Ca, Mg, Zn, and La (except CaS04) on Cu and Mn is performed. A study of the peak form of the recorded absorption signals is carried out and a comparison is made between peak area and peak height. Sharper and narrower peaks are observed for Interferences resulting in an increase of the absorption signal. This points to a faster atomization of the analyte in these cases. Because the peak form was unaffected in the case of negative interferences, the effect of the times and temperatures for drying, ashing,
and atomization was investigated. This shows that these interferences are at least partially due to occlusion of the anaiyte in the matrix.
In the past few years, matrix effects encountered with nonflame atomization devices have been investigated by several authors (for instance 1-8). Nevertheless, much work remains to be done to elucidate the origin and nature of the different observed interactions. A comparison of the data given by the various authors is difficult because of the diverse atomization designs used, since atomization temANALYTICAL CHEMISTRY, VOL. 48, NO. 1, JANUARY 1976
125
Table I. Experimental Conditions for the Interference Studies on Cu and Mn Sample volume, pl Drying Thermal destruction Atomization
150%
cu
Mn
50
50 100 "C/30 sec 1 1 0 0 "C/30 sec 2600 "C/lO sec
100 "C/30 sec 900 "C/30 sec 2600 "C/10 sec
Table 11. Interferences Observed in the Flameless AAS Determination of Mn and Cu (expressed in %) Effect on 5 0 ppb Mn of
Ion
Ca
Salt
100 ppm ion
CaC1, -8 0 Ca(NO,), + 20 CaHPO, + 10 Mg MgC1, +50 Mg(N0, )2 + 40 MgSO, + 35 MgHPO, + 20 Na NaCl 0 NaNO, 0 Na,SO, + 25 Na,HPO, 0 K KC1 0 KNO, 0 K2SO4 0 K,HPO, 0 La La,O, in -40 HC1 La,O, in 0 HNO, Zn ZnC1, 0 x = effect not investigated.
1000 ppm ion
-9 5 + 30 -25 -8 0 + 40 + 40 -1 5 0 0
Effect on 100 ppb Cu of 100
ppm ion
-2 5 0 0
-20 0 0 0 0
-15 0 -45 0 0 0
-9 5
1000 ppm ion
-40 0 -2 0
-2 0 + 10 + 30 + 10 -20 0
+ 20
- 50%
-60 + 40 +10
-30 0 0 0
-45 0 0 0
-50
-8 0
0
+ 15
+ 15
0
XQ
XQ
EXPERIMENTAL Instrumentation. A double-beam Perkin-Elmer atomic absorption spectrometer Model 305, equipped with a deuterium background corrector, a graphite furnace Perkin-Elmer HGA 7 2 , and a Perkin-Elmer recorder Model 56 were used. The correction was found to be satisfactory since no signal was observed for solutions of interferent without analyte. To integrate the AAS output signal, a network-amplifier combination was used. An A.M. 741 (Advanced Micro Devices Inc.) operational amplifier with open loop dc gain (A, > lo5) is shunted by a high quality capacitor. With a 1-kQ input resistor, an effective decharging time constant of lo2 sec is obtained which meets the requirements for active integration of the actual signals. Careful initial balancing by means of a 110-kR resistor minimizes spurious integration due to dc offset of the amplifier. A shorting switch across 48, NO. 1,
Table 111. Effect of Acids
JANUARY 1976
Analyte: S O ppb Mn
100 ppb Cu
Acid concentration
1%
5%
10%
1%
s%
10%
HC1 H,PO, H,SO, HNO,
0 +15 0 0
0 +15 -25 -20
0 xQ -50 -60
0 +12
0 +12 0
XQ
Q
perature, rate of heating, gas flow, and amount of sample injected vary with the system employed. The most import a n t to date are the graphite tube and carbon rod or filament atomizers. The following kinds of interferences have been observed (9): 1) Physical interferences due to retention by occlusion in a n excess of less volatile matrix compounds or covolatilization with more volatile matrix substances, incorporation of the element in the graphite and nonspecific absorption. 2) Chemical interferences caused by the formation of compounds of different volatility or carbide formation. Both kinds of interference result in an increase or a decrease of the absorption signal and consequently may lead t o erroneous results if the experimental conditions are not strictly controlled. Studies on the occurrence of Cu and Mn in biological calcifications (IO)and tissue samples ( 1 1 ) led us to investigate the effects of different ions important in biological materials-namely, H , K, Na, Ca, Mg, and La salts (NOS-, PO4"-, C1-, so42-, HP04*-)-0n these two elements.
* ANALYTICAL CHEMISTRY, VOL.
centration in ppm of interfering substance
+. MgSOd; 0, NaCI; 8 , CaCI2;X. KCI; 0 ,MgCI2; U, La3+/CI-
-1 0
Q
126
Figure 1. % interaction on the Cu signal as a function of the con-
0
0 -20
irreproducible results
x = effect not investigated.
the capacitor permits integration over the desired time intervals. Simultaneous recording of the in- and output signals of the integrator was done by means of a BD 9 dual pen recorder (Kipp en Zonen) with a full scale deflection time
