T h e atomic absorption method has been used for over a year in this laboratory t o analyze both urban and rural lead candles. This method provides a rapid and economical approach for t h e laboratory analysis of lead candles used to evaluate atmospheric sulfation in monitoring and surveillance programs. Approximately 25 lead candles can be analyzed in one man-day using the atomic absorption procedure compared t o a week or more using the gravimetric procedure. T h e atomic absorption method should be applicable to other types of lead dioxide samplers such as sulfation plates. Acknowledgment The authors thank C. S. Nevin of the A. E. Staley Manufacturing Co. for his consultation and initial samples of P3-100 resin. Thanks are also given to Jacqueline Dohm and Lois Fox for sample preparation and handling
during many of the analyses. Special thanks are extended to Robert Jorgen for his contribution t o this study. Literature Cited Am. SOC. Testing Materials, ASTM Standards Industrial Water, Atmospheric Analysis, p 813, 1966. Bowden, S. R., Int. J. Air Water Pollut., 8, 101 (1964). Huey, N . A., “The Lead Dioxide Estimation of Sulfur Dioxide Pollution.” 60th Annual Meeting APCA. Cleveland. Ohio. Paper No: 67-198, 1967. Kanno. S., Int. J . Air Pollut., 1, 231 (1959) Rayner, A. C., J . Air Pollut. Contr. Assn., 16,418 (1966) Vijan, P. N., Enuiron. Sci. Technol., 3,931 (1969). Y
Received for recieu February 8, 1973. Accepted July 20, 1973. Presented a t the 8 t h M i d u s t Regional Meeting of the American Chemical Society, Nocember 8-10, 1972. The use of brand names for specific chemicals or equipment and names of their suppliers does not constitute an endorsement by the Health Department or S t . Louis County.
Levels of Copper, Nickel, Rubidium, and Strontium in Institutional Total Diets Gopala K. Murthy,’ Ulysses S. R h e a , and J a m e s T. Peeler F o o d a n d D r u g Administration, U.S. D e D a r t m e n t of H e a l t h . Education, a n d W e l f a r e , Cincinnati, O h i o 45226
The average trace element content in the diets of institutionalized children, aged 9 to 12, from 28 U.S. cities, expressed as mg/kg of food, varied as: copper, 0.4380.873; nickel. 0.140-0.321; rubidium, 0.601-2.338; and strontium, 0.319-0.957. Similarly. the consumption of food varied from 1.18-2.55 kg/day and the milk content of diet varied from 9.5-63.870. Minerals from drinking water were not included in the study. Statistical analyses of the data (mg/day) showed significant seasonal and geographical variations. hlonthly averages for all elements showed that copper was slightly higher during summer, rubidium and strontium tended to peak during spring and autumn. and no trend could be ascribed to nickel. The low and high levels of trace elements observed in different geographical areas are briefly discussed. In a previous paper (Murthy et al., 1971). we reported the levels of antimony. cadmium, chromium, cobalt, manganese. and zinc in institutional total diets. The present paper is concerned with the levels of copper (Cui. nickel ( X i ) , rubidium (Rb). and strontium ( S r ) in the same samples. Most of the available d a t a on trace elements (Cu, Xi. Rb. and S r ) in foods pertain to individual components of the diet (El-Gindy. 1959; Golvkin and Kraynova. 1969; Gormican. 1970; Il’vitskii and Asmaeva, 1969; Kleinbaum. 1962; Leshchenko et al., 1972; Los and Pjatnickaja, 1962; Malina and Klyachko, 1969; Murthy e t al., 1967; Schlettwein-Gsell and Mommsen-Straub, 1971a,b; Schroeder et al., 1962; Schroeder et al., 1966; Tsvetkova, 1969; Jaulmes and Hamelle. 1971; and Stephanov et al., 1970) with very little data on total diets. Kent and McCance (1941) studied ingestion by humans of Ni from ordinarv diets. Harrison et al. (1960) deter1
To whom corre?pondence should be addressed.
1042
Environmental Science & Technology
mined the Sr balance in children maintained on normal diets and reported S r intake over a 12- to 18-day period. Similarly, Bryant et al. (1958) analyzed various foods in different regions of England and Wales and reported the average dietary intake of Sr. Yamagata (1962) determined R b intake by analyzing the diets of urban and rural adults and children in Japan. Feldman and Jones (1964) determined several trace elements by spectrographic analyses of institutional diets from 10 cities in the Ynited States. Zook and Lehmann (1965) analyzed total diets prepared from basket foods and computed the intake of certain trace elements by children receiving 4200 calories per day. Tipton et al. (1966) reported data on diets and excreta of two human subjects maintained on a normal diet for a 30-day period. Tipton et al. (1969) reported data on diets and patterns of elemental excretion in long-term balance studies. Engle et al. (1967) determined ingestion of certain trace elements by preadolescent girls maintained on measured amounts of diets. Soman et al. (1969) determined total intake of certain trace elements from diets of different ethnic groups in India. Rehnberg et al. (1969) determined Sr in the institutional total diets and milk collected from southeastern Cnited States. Murphy et al. (1971) analyzed type A school lunches for certain trace elements. White (1969) analyzed forty-eight 24-hr weighed samples of diets of high school girls and college women for various trace elements. Meranger and Smith (1972) analyzed various components of the Canadian diet and estimated daily intake of several trace elements. No systematic analyses of diets have been made for extended periods, however. to determine variations attributable to geographic location and season. E x p erim e n t a 1
Materials. Samples used in this study. including description and method of collection. have been described previously ( l l u r t h y et al. (1971)). The samples were homogenized by a n electric blender in a stainless steel con-
tainer or in an environmental residue processing apparatus (U.S. Public Health Service, 1967). A known amount of the homogenized sample (3.5 liters) placed in a Corningware dish was dried in a n electric oven and then ashed a t 550-600°C in a muffle furnace for 48 hr. The ash was ground to a fine powder by the use of a mortar and a pestle. Portions of the well-mixed ash of food samples from the Radiological Health Laboratories, U.S.Public Health Service, were received in our laboratory for trace elemental analyses. Apparatus. The atomic absorption spectrophotometer described previously (Murthy and Rhea, 1967) was used in this study. Procedure. One-half gram of ash placed in a 150-ml beaker was wetted with 3-5 ml of double-distilled water and dissolved by adding 2.0 ml of concentrated H N 0 3 . The solution was evaporated to dryness on a hot plate and treated again with 2.0 ml of concentrated H N 0 3 by warming. The residue was quantitatively transferred to a 35-ml graduated conical-bottom, glass-stoppered centrifuge tube, using 1.ON H X 0 3 . mixed well, and centrifuged a t 825 G to remove any silica particles. The H N 0 3 used in these studies was previously distilled. The Cu, Ni, and Rb contents were determined directly on the supernatant solution; for Sr analysis, however, 3.0 ml of the supernatant solution was pipetted into a 30-ml beaker and the solution was evaporated to dryness. The residue was digested with 2.0 ml of 6 N HC1 and evaporated to dryness. The residue was then dissolved in 5 ml of 6N HC1 and quantitatively transferred to a 15-ml graduated conical-bottom, glass-stoppered centrifuge tube. One milliliter of 10% lanthanum solution was added, and the mixture was diluted to 10 ml with water. The lanthanum was necessary to complex the interfering phosphates. All working standards for Cu. Ni, and Rb were made up in 1.ON H N 0 3 . The Sr standards contained 10,000 ppm La and 2000 ppm Na and HC1; the Na was necessary to adjust the total solids and to improve flame characteristics.
S r contents of the total diets. The average consumption of food in various institutions ranged from 1.18 to 2.55 kg, whereas the percent of milk in the total food ranged from 9.5 to 63.8%, with a weighted average of 37.5%. Similarly, the range of averages of all locations for the various elements, in mg/kg, and the weighted average were: Cu, 0.438-0.873 and 0.610; Ni, 0.140-0.321 and 0.239; Rb, 0.60-2.338 and 1.245; and Sr, 0.319-0.957 and 0.659. For detailed statistical analyses, data oh foods from locations indicated in Table I11 (ACS Microfilm Depository Service) were included. The locations refer to the city in which the institution is situated. Other locations were excluded inasmuch as there was no continuity of samples during the year or because of missing values. Since assessment of body burden is dependent upon the amount of element ingested, all the observed values (mg/kg) were converted to mg/day using food consumption data. Analysis of variance of the data, based on an unequal number of samples from each location and the assumption and calculations of Bankroft (1968), indicated that the amount of Cu, Ni, Rb, and Sr ingested varied significantly from one month to another and from one institution to another (Table IV). Locations and months were assumed to be fixed effects. The significant interaction effect was taken into account in discussing differences noted in months and locations. T o determine whether the observed geographical difference was due to any one location, the
Table I. Analyses of Reference Samples Sr, mg/kg Sample Milk ash ~ 7 6 0 4 ~ Foodash=2480a Milkb Milk Milk
Reported
Observed
0.038 0.103 0.062 0.039 0.054
0.035 0.099 0.060 0.037 0.047 t
R e s u l t s and Discussion
Performance of the atomic absorption spectrophotometer was tested by determining the recoveries of Cu, Ni, Rb, and Sr and the reproducibility of analyses. Known amounts of Cu (5.0 p g ) , Ni (50.0 p g ) , Rb (25.0 p g ) , and S r (40.0 p g ) were added to 0.5-gram portions of food ash, and the samples were processed as described under Procedure. Analyses of eight replicate samples indicated recoveries and standard deviations of Cu, 95.7 f 3.2%; Xi, 97.2 f 0.6%; Rb, 101.0 f 1.6%, and Sr. 95.7 f 3 . 2 7 ~ . In regard to Sr determination, the validity of analysis was further tested by analysis of reference milk and food ash samples provided by other laboratories. The results are found in Table I. Statistical analysis, “t” test, of the reported and observed data showed no significant differences, indicating sufficient accuracy of analysis. Sixteen 1-gram portions of the same food ash were also analyzed; the reproducibility data showed 97.2 f 2.6 p g Cu, 33.5 f 2.6 p g Xi, 135.0 f 3.2 pg Rb, and 100.9 f 6.1 p g Sr, with a coefficient of variation of 2.6, 7.8, 2.4, and 6.170, respectively. The ranges in values represent standard deviation of the mean. Similarly, eight individua! food ash samples, selected a t random every month were analyzed in duplicate and showed coefficient of variation of 2.7, 7.2, 3.8, and 7.2%. respectively. Observed recovery and reproducibility data were assumed satisfactory, considering the levels at which these elements in the food ash were analyzed by atomic absorption. Table I1 (ACS Microfilm Depository Service) costains data by sampling location regarding food consumption, percent of milk in the total food, and the Cu, Ni, Rb, and
= 3.88c
Health and Safety Laboratory. AEC, New York, N.Y. Southeastern Radiological Health Laboratory, Montgomery, Ala. Not significant at u = 0.01.
Table I V . Analysis of Data, Mg/Day Source
Degrees of freedom
Mean square
Variance ratioa
Copper Months ( A ) Location ( B ) A X B
Error
11 18 198 94
0.12698 0.43147 0.09100 0.00071
178.84 607.70 128.17
0.22010 0,17681 0.01 659 0.00078
282.18 226.68 21.27
0.7971 1 7.27089 0.31950 0.00595
133.97 1221.oo 53.70
0.63258 0.78289 0.09804 0.00551
114.81 142.09 17.79
Nickel Months ( A ) Locat ion A X B
Error
11 20 220 99
Rubidium
Months ( A ) Location ( B ) A X B Error
11
20 22 0 101
Strontium Months (A) Location ( B ) A X B
Error a
11 18 198 87
Each value sjgnificant at (Y = 0.01
Volume 7, Number 11, November 1973 1043
mean values were analyzed by Duncan's test [1955 as modified by Kramer (1956)]. It is evident from the results (Table III) that some trends do exist for unequal means. Samples from Omaha, Neb., were high in Cu, Rb, and Sr, whereas those from Tampa, Fla., were high in Cu, Ni, Rb, and Sr. Samples from Columbia, Miss., were highest in Ni and Rb, and samples from Albuquerque, N.M., were second highest in Cu and Ni. Most significantly low values were observed for Ni, Rb, and Sr in samples from Palmer, Alas., and for Ni and R b in samples from Salt Lake City, Utah. Similarly, previous data (Murthy et al., 1971) had shown that, in general, diets from Palmer, Alas., and Salt Lake City, Utah, had the lowest concentrations of Sb, Cd, Cr, Co, Mn, and Zn, whereas those of Tampa, Fla., and Columbia, Miss., had consistently high concentrations. Figure 1 illustrates variations in consumption of food, milk, Cu, Ni, Rb, and Sr. Copper consumption was slightly high during summer, R b and Sr tended to peak in spring and autumn, and no significant trend could be attributed for Ni. The seasonal trend in S r conforms with the literature data (Rehnberg et al., 1969). Observations over several years may be necessary to establish a trend. Further information concerning the supply, distribution, and components of the diet is needed to explore this problem. Data Comparison. It is difficult to compare our data with those in the literature because data on diets are limited and methods differ; however, some d a t a can be compared. Copper. Spectrographic analyses of the normal diets of two individuals gave 0.91-1.04 mg (Tipton et al., 1966), and 0.95-1.70 mg of Cu per day (Tipton et al., 1969). Normal diets of different ethnic groups in India showed intakes of 2.8-13.6 mg per day (Soman et al., 1969), whereas the Cu intake by preadolescent girls, aged 6-10, consuming measured diets, ranged from 1.08-3.87 mg per day (Engel et al., 1967). The Cu content of teen-agers' diets from 10 United States cities varied from 0.345-1.436 ppm, with an average of 0.649 ppm (Feldman and Jones, 1964), whereas the Cu intake through type A school lunches ranged from 0.06-2.19 mg, with a n average of 0.34 mg per lunch (Murphy et al., 1971). Similarly, analyses of forty-eight 24-hr weighed samples of the diet of high school girls and college women showed Cu contents ranging from 0.15-1.12 mg and 0.20-4.40 mg, respectively (White, 1969). Intake based on analyses of commodity foods gave an average of 2.217 mg of Cu in the diet per day (Meranger and Smith, 1972). Similarly, for general menus of hospitals, the computed daily intake of Cu was
