Pilar Bermejo-Barrera,. *. Antonio. Moreda-Pi#{241}eiro,Teresa Romero-Barbeito
,. Jorge Moreda-Pi#{241}eiro, and Adela Bermejo-Barrera. (Dept. of Anal.
Clinical Chemistry
Traces of Cadmium in Human Scalp Hair Measured by Electrothermal Atomic Absorption Spectrometry with the Slurry Sampling Technique, Pilar Bermejo-Barrera, * Antonio Moreda-Pi#{241}eiro,Teresa Romero-Barbeito, Jorge Moreda-Pi#{241}eiro, and Adela Bermejo-Barrera (Dept. of Anal. Chem., Nutrition, and Bromatob., Faculty of Chem., Univ. of Santiago de Composteba, Av. das Ciencias s/n, E - 15706 Santiago de Compostela, Spain; *author for correspondence: fax 34 81 595012, e-mail
[email protected]) Cadmium induces toxic effects in humans, even at low concentrations, and is concentrated in specific organs [1]. Blood and urine samples are most often used to assess cadmium burden in humans [1]. Hair analysis has also been used for measurement of nutritional deficiencies [2, 3], for biological monitoring [4, 5], and as an index of environmental exposure [6, 7]. Hair is readly available and easily collected, shipped, stored, and handled, and it can be obtained with little or no pain [7]. In addition, trace element concentrations in hair are -10-fold greater than in blood or urine /7-9]. Sample decomposition procedures for hair [3, 10, 11] are often tedious and time consuming and allow the possibility of sample contamination and loss of volatile metals, such as cadmium. Electrothermal atomic absorption spectrometry (ETAAS) allows the determination of metals in solid samples by introducing the sample as a slurry [12], so the problems related to conventional sample decomposition procedures are avoided. In our experience [13, 14], results of ETAAS methods based on the slurry sampling are comparable with the conventional wet-digestion sample pretreatments. Among the problems of ETAAS is the high background signal seen with poor matrix volatilizations, especially when low charring temperatures must be used for volatile elements such as cadmium. This problem can be addressed by use of the Zeeman effect background correction. We developed a slurry sampbing-ETAAS method for measuring cadmium in human scalp hair using D2 arc background correction and (NH4),HPO4 as chemical modifier. We used a Perkin-Ebmer (Norwalk, CT) Model 1 lOOB atomic absorption spectrometer equipped with a deuterium lamp, a HGA-400 graphite furnace atomizer, and an AS-40 autosampler. Spectrometric operating conditions are given in Table 1. A Laser Coulter Series LS100 Fraunhofer Optical Model particle sizer (Coulter Electronics, Hiabeah, FL) was used to obtain the particle size distribution. A vibrational mill ball, Retsch (Haan, Germany) ISO-900 1 equipped with zirconia cups (1.5 mL in size) and zirconia balls (7 mm diameter), was used to pulverize samples and to reduce the particle size of the powdered hair samples. An Agimatic magnetic agitator from Selecta
Table 1. GraphIte furnace temperature program and spectrometer Temperature, Stage
operating
conditions.
Ramp time,
Hold time,
$
S
Ar flow-rate, mL/min
300
Drying
150
15
20
Charring
900
10
10
Atomization
2200
Cleaning
2500
1 1
2 3
300
0 (Read) 300
Conditions: Cd hollow cathode lamp (4 mA): wavelength, 228.8 nm: spectral bandwidth. 0.7 nm: integration time. 3 s: peak-areameasurements: 02 lamp backgroundcorrector: injection volume, 20 xL: pyrolytic graphite tubes.
42, No. 8, 1996
(Barcelona,
1287
Spain) was used to suspend the slurry particles just before measurements. All solutions were prepared from analytical reagent-grade chemicals with ultrapure water, resistivity 18 M[I/cm (Millipore, Bedford, MA). Acetone was from Carlo Erba Analyticabs, Milan, Italy; cadmium nitrate stock calibration solution, 1 gIL, from BDH, Poole, UK diammonium hydrogen phosphate stock calibration solution, 20 gIL, prepared from diammonium hydrogen phosphate, was from Scharlau, Barcelona, Spain; glycerol was from Sigma Chemical Co., St. Louis, MO; lanthanum chloride stock calibration solution, 1 g/L, prepared from banthanum chloride, was from Merck, Darmstadt, Germany; magnesium nitrate stock calibration solution, 2 g/L, prepared from magnesium nitrate, was from BDH; and nitric acid, 350 g/L, prepared from nitric acid Anabar, 69.0-70.5% with a maximum cadmium content of 0.005 mgIL, was from BDH. Palladium stock calibration solution, 3 g/L, was prepared by dissolving powdered palladium (Aldrich Chemicals, Milwaukee, WI) in concentrated nitric acid. Reference Material CRM 397, human hair, was from the Commission of European Communities Community Bureau of Reference (BCR), with a certified cadmium content of 0.521 ± 0.024 tg/g. Triton X-b00 was from Merck, and Viscalex HV3O from Allied Colboids, Bradford, UK. Approximately 0.5 g of hair was cut with stainless steel scissors from the scalp region [5]. The samples were washed as proposed by the International Atomic Energy Agency [15], beginning with ultrapure water, three washes with acetone, and three washes with ultrapure water. The samples were oven-dried at 100 #{176}C and kept in polyethylene containers. The washed hair samples were pulverized for 20 mm at 75% power and sieved to achieve a particle size
