1950
ANALYTICAL CHEMISTRY, VOL. 50, NO. 13, NOVEMBER 1978
for acetone and a Chromosorb 102 column for methanol or water. Neither carbon disulfide nor nitrogen-containing solvents can be used because of the extreme response and slow recovery of the detector to these solvents. T h e application of this technique to direct analysis of air samples without preconcentration on a charcoal tube should present no difficulty (although these tests have not yet been performed in this laboratory). A 1.0-mL gas sample injection of air containing 1.0 ppm of ACN will contain 2.3 ng of ACN. Since the detection limit of ACN is 10 pg per injection, direct air analysis should be applicable a t concentrations as low as 10 ppb ACN in air.
0 z
4
0,
A
'
< _
ACKNOWLEDGMENT The authors thank Michael D. Kelly for his technical assistance and suggestions. LITERATURE CITED (1) (2) (3) (4) L0 1 2 3 TIME (MIN I
(5)
Figure 3. Chromatograms resulting from ~-I.LLwater injections on Chromosorb 102 column: (A) 8.8 nglpL standard, (B) extract from spiked enamel paint
(6) (7) (8)
T h e N P D will yield a positive or negative response to the solvent depending on the bias voltage and the cleanliness of the crystal (8), thus necessitating the separation of the solvent from the ACN. This is accomplished using an SPlOOO column
R. J. Steichen, Anal. Chem., 48, 1398 (1976). M. E. Hall and J. W. Stevens, Jr., Anal. Chem., 49, 2277 (1977). J. F. Finklea, Am. Ind. Hyg. Assoc. J . , 38, 417 (1977). NIOSH method and data report No. S-156 supplied by C. S. McCammon; National Institute for Occupational Safety and Health, Cincinnati, Ohio, March 1978. C. A. Burgett, "The Gas Chromatographic Determination of Residual Acrylonitrile Monomer", Hewlett-Packard Note ANGC8-76 (1976). C. W. Rice, U S Patent 2,550,498 (April 24, 1951). "NIOSH Manual of Analytical Methods", HEW Publication No. (NIOSH) 75-121, U.S. Government Printing Office, Washington, D.C. 1974, P 8 CAM 127 (1975). H. B. Bente, "Evaluating and Optimizing the Performance of the Nitrogen-Phosphorus Detector", Hewlett-PackardNote 5950-3535 (February, 1977).
RECEIVED for review June 8, 1978. Accepted July 6, 1978.
Pepperbush Powder, a New Standard Reference Material Kensaku Okamoto, * Yuko Yamamoto, and Keiichiro Fuwa National Institute for Environmental Studies, P.O. Yatabe, Ibaraki, 300-2 7, Japan
T h e importance of standard reference materials for metal analysis has been recently well-recognized by scientists in many fields. T h e authors, in a cooperative study with NBS research groups, have performed some research for new biological reference materials, and t h e work includes t h e preparation of Japanese Tea Leaves (1) and "wet" Shark Meat samples (2). Pepperbush tree is known to accumulate Zn, Mn, Co, Ni, and Cd in t h e leaves ( 3 ) ;thus the elemental composition of pepperbush leaves is significantly different from that of other botanical reference materials such as Kale Powder ( 4 ) ,Orchard and Pine Needles Leaves (5), Tomato Leaves (6),Spinach (9, (8). We have, therefore, prepared pepperbush powder as a new biological standard reference material.
EXPERIMENTAL Sampling a n d Drying. The leaves of pepperbush (Clethra barbineruis), collected in September 1975, at Mikouchi in the Ashio district and free from stems, were washed with deionized water and dried in an air oven at 60 "C overnight. About 30 kg of the dry leaves were used in this work. Grinding and Sieving. The dry leaves (about 700 g) were ground for about 1 h in a ball-mill (95'70 Al2O3,7 L) which had been previously ground well with the leaves to minimize contamination with metals. The pulverized samples were placed on 0003-2700/78/0350-1950$01.OO/O
Table I. Homogeneity of Pepperbush Samples p g l g dry wt
maximum value minimum value average re1 std dev, %
Zn 345 325 337 1.5
Fe 172 161 166
2.2
Mn 2110 2020 2090 1.0
a set of sieves; a 50-mesh (297 pm) nylon sieve (top), a 60-mesh (177 wm) nylon sieve (middle), and a reservoir made of vinyl chloride (bottom), and vibrated mechanically for 15 min. Mixing. The powder which passed through a BO-mesh sieve was divided into two parts with a riffle sampler (JIS No. 2) made of vinyl chloride. The powder was piled up in two layers and again divided by passing through the riffle sampler. Pepperbush samples were homogenized by repeating this procedure ten times. Metal Determinations for Assessment of Homogeneity. Samples were dry-ashed as follows: One gram of pepperbush powder (dried at 105 "C to constant weight) was ashed in a platinum crucible at 450 "C overnight, dissolved in 2 mL of 6 M HC1 and made up to 100 mL with doubly-distilled water. Samples were also wet-digested with nitric acid and hydrogen peroxide as described previously (3). Zn, Fe, Mn, and Mg were determined by atomic absorption spectrometry using an air-acetylene flame. Co, Cd, Pb, and Cu were determined by atomic absorption 22 1978 American Chemical Society
ANALYTICAL CHEMISTRY, VOL. 50, NO. 13, NOVEMBER 1978
Table 11. Elemental Composition of Pepperbush Powder and Comparison with Other Botanical Reference Materials Pepperbush Orchard Tomato Pine NIES Leaves Leaves Spinach Seedles (?), (61, (7), ( 8 ), No. 1, pg/g hBS NBS NBS NBS 1571 1573 1570 1575 drywt K 1.57 (5%) 1.47 (%) 4.46 (5%) 3.56 (5%) 0.37 (%) Ca 1.45(%) 2.09 ( 7 0 ) 3.00 ( % ) 1.35 (%) 0.41 (%) Mg 4090 6200 (7000)
Fe
172 2050 (21)' (8)" (8)" 11 328
Mn Co Pb Cd
cu Zn a
300
91 (0.2) 45 0.11 12 25
690 238 (0.6) 6.3 (3) 11 62
550 165 (1.5) 1.2 (1.5) 12 50
200 675 (0.1) 10.8 (
