Graphite-furnace atomic absorption spectrometric determination of lead, cadmium, cobalt and nickel in infant formulas and evaporated milks after nitric-perchloric acid digestion and coprecipitation with ammonium pyrrolidine dithiocarbamate

A graphite-furnace atomic absorption method, developed for lead and cadmium, was modified to enable simultaneous determination of lead, cadmium, cobalt and nickel in infant formulas and evaporated milks. The method was assessed on the basis of analytical quality assurance results during routine analysis of samples. Detection limits (ng g-1 based on 10 g sample size for ready-to-use formulas) were 0.04-0.21 for lead, 0.004-0.015 for cadmium, 0.04-0.2 for cobalt and 0.06-0.26 for nickel. Within-series repeatability and day-to-day reproducibility (among series) coefficients of variation (CVs) were, respectively, 11.7 and 16% for lead, 2.5 and 7.5% for cadmium, 7.2 and 18.8%for cobalt, and 8.1 and 8.6% for nickel at respective concentrations of 1.89, 0.40, 1.25 and 11.8 ng g-1.     

The effect of surfactants on the extraction-atomic absorption spectrophotometric determination of copper, iron, manganese, lead, nickel, zinc cadmium and cobalt

Nine surfactants representing pure cationic, anionic and non-ionic detergents, three industrially prepared detergents. sodium pyrophosphate. sodium tripolyphosphate, and a soap were investigated for their effect on the extraction-atomic absorption spectrophotometric determination of copper. iron, manganese and lead. Some results are also given for nickel, zinc, cadmium and cobalt. Cations were extracted into 10 ml of MIBK as APDC chelates. To Avoid emulsion formation, maximum concentration of LAS was 1 mg 1⁻¹, and for formulated and non-ionic detergents and washing powders it was 5 mg 1⁻¹.A standard addition procedure was used to obtain correct results for copper and nickel. Two extractions of iron, cobalt and lead, and one extraction of manganese, zinc and cadmium gave a recovery of 100 ± 5%. Soap gave high recoveries for iron and copper. NTA in concentrations up to 25 mg l⁻¹ did not interfere. EDTA in concentrations up to 25 mg l⁻¹ interfered with iron and nickel determinations, but the addition of 3 mg of aluminium removed the EDTA interference in the determination of copper, manganese, lead, zinc, cadmium and cobalt.For the determination of trace metals in polluted natural waters the amount of 4% APDC was increased to 10 ml and for manganese to 25 ml. An addition of 3 mg aluminium as nitrate after the addition of buffer with subsequent 20 min reaction time is required for the determination of all eight metals by the recommended procedures. The effect of humic acid was also investigated.     

The effect of surfactants on the mixed chelate extraction-atomic absorption spectrophotometric determination of copper, nickel, iron, cobalt, cadmium, zinc and lead

Twelve surfactants representing pure cationic, anionic and non-ionic detergents, three commercial detergents, sodium pyrophosphate, sodium tripolyphosphate, a soap, nitrilotriacetic acid (NTA), EDTA, and humic acid were investigated for their effect on the extraction-atomic absorption spectrophotometric determination of copper, nickel, iron, cobalt, cadmium, zinc and lead. Cations were extracted into 10 ml of a solution containing diphenylthiocarbazone, 8-quinolinol and acetyl acetone in ethyl propionate. To avoid emulsion formation, the maximum concentration of linear alkylate sulphonate (LAS) was 10 mg l⁻¹ and for solid industrial LAS-type detergent was 50 mg l⁻¹, but washing powder did not interfere at 100 mg l⁻¹. Cationic and non-ionic detergents gave low recoveries for cobalt. Condensed phosphates at a concentration of 20 mg l⁻¹ did not cause significant interference. NTA interfered with nickel extraction and EDTA with all metals. Humic acid, however, gave no interference. A standard addition procedure can be used to correct the results.A comparison is made between the APDC-MIBK and the mixed chelate-ethyl propionate methods for the determination of trace metals in the presence of various surfactants in natural waters; the latter is preferable.     

Chromium, nickel, copper, zinc, arsenic, selenium, cadmium, mercury and lead in Dutch fishery products 1977-1984

Within the framework of a monitoring programme, carried out by order of the Dutch Ministry of Agriculture and Fisheries, fishery products from Dutch coastal waters, estuaries and inland waters were investigated for the presence of trace elements. In this report the results for the period 1977-1984 are presented. The investigated fishery products included sole, cod, plaice, herring, eel, pike-perch, shrimp and mussel, in which the elements chromium, nickel, copper, zinc, arsenic, selenium, cadmium, mercury and lead were determined. The results are compared with data from the literature and with the trace element levels usually found in other animal products. The daily intake of trace elements in The Netherlands through the consumption of Dutch fishery products is calculated.     

Monitoring of lead, cadmium, chromium and nickel in placenta from an e-waste recycling town in China

Toxic heavy metals are released to the environment constantly from unregulated electronic waste (e-waste) recycling in Guiyu, China, and thus may contribute to the elevation of lead and other heavy metals levels in placenta. We aimed to investigate concentrations of heavy metals, including lead (Pb), cadmium (Cd), chromium (Cr), and nickel (Ni) in placenta from Guiyu and compared them with those from a control area where no e-waste processing occurs. Two hundred and twenty human placentas were collected from Guiyu (n = 101) and the control area (n = 119). The placenta concentrations of Pb, Cd, Cr, and Ni (PCPb, PCCd, PCCr, and PCNi) were determined by graphite furnace atomic absorption spectrometry (GFAAS). Risk factors of high exposure and correlation with adverse pregnancy outcomes were analyzed using Spearman correlation analyses. PCPb from Guiyu ranged from 6.51 to 3465.16 ng/g with a median of 301.43 ng/g, whereas PCPb from the control area ranged from 4.53 to 3176.12 ng/g with a median of 165.82 ng/g (P = 0.010). We also observed that in Guiyu, 41.6% of women (42/101) had PCPb > 500 ng/g wt (wet weight), compared with 24.4% of women (29/119) in the control area (P = 0.006). No significant differences of PCCd and PCCr were found between the two groups. In contrast, PCNi was higher in samples from the control area (median 14.30, range 1.76-593.70 ng/g) than in Guiyu samples (median 7.64, range 1.19-1108.99 ng/g) (P = 0.000), and a negative correlation between PCNi and gestational age was found in this study (P = 0.017). Spearman correlation analyses showed that there was correlation between PCPb and residence in e-waste recycling area. Environmental pollution, resulted from unregulated e-waste recycling activities, may contribute to elevated PCPb in neonates born in Guiyu and threaten their health.     

A comparison of the non-essential elements cadmium, mercury, and lead found in fish and sediment from Alaska and California

Concentrations of three non-essential elements (cadmium (Cd), mercury (Hg), and lead (Pb)) were determined in sediment and fish from several locations in Alaska (AK) and California (CA) and used to examine differences in bioaccumulation within and between geographic locations. We analyzed tissue (liver, muscle, gill, and stomach contents) from white croaker (Genyonemus lineatus) and English sole (Pleuronectes vetulus) in California and flathead sole (Hippoglossoides elassodon) in Alaska, in addition to several species of invertebrates (mercury only). As found in previous work on arsenic (As) [Meador et al., 2004], Cd in fish liver exhibited a negative correlation with sediment concentrations. No such correlations were found for Hg and Pb when fish liver and sediment were compared; however, these metals did exhibit a positive relationship between liver and organic carbon normalized sediment concentrations, but only for the CA sites. Sediment concentrations of Hg at the AK sites were lower than those for the CA sites; however, AK invertebrates generally bioaccumulated more Hg than CA invertebrates. Conversely, Hg bioaccumulation was higher in CA fish. Even though ratios of total metal/acid volatile sulfides (AVS) in sediment were one to two orders of magnitude higher for the AK sites, bioaccumulation of these elements was much higher in fish from the CA sites. Bioaccumulation factors ([liver]/[sediment]) (BAFs) were highest at relatively clean sites (Bodega Bay and Monterey), indicating that elements were more bioavailable at these sites than from more contaminated locations. The observation of high BAFs for As in fish from Alaska and low BAFs for the California fish, but reversed for Cd, Hg, and Pb in this study, implies that differences in fish species are less important than the unique geochemical features at each site that control bioavailability and bioaccumulation and the potential sources for each element. Additionally, these data were also used to examine the metal depletion hypothesis, which describes the inverse relationship between elements and organic contaminants documented in some monitoring studies. Our results suggest that the enhanced bioavailability of the metals at some uncontaminated sites is the main determinant for the inverse correlation between metal and organic contaminants in tissue.     

Intakes of copper,zinc, cadmium,tin, iron,nickel and arsenic in a population exposed to lead from water

Adult diets obtained from a population in Ayr, Scotland, U.K., known to be exposed to lead from water were analysed for arsenic, cadmium, copper, iron, nickel, tin and zinc to assess the intake of these elements. With few exceptions, the concentration of each element varied little from diet to diet, and therefore the range of intakes varied only in proportion to the weights of the diets. With the exception of nickel, the difference between the observed average dietary intakes of the metals studied and those expected on the basis of a nationwide Total Diet Study is largely accounted for on the basis of the difference between the weights of the duplicate diet and the weight for the Total Diet Study.     

Biomonitorization of cadmium, chromium, manganese, nickel and lead in whole blood, urine, axillary hair and saliva in an occupationally exposed population

Heavy metal contamination from occupational origin is a cause for concern because of its potential accumulation in the environment and in living organisms leading to long term toxic effects. This study was aimed to assess Cd, Cr, Mn, Ni and Pb levels in whole blood, urine, axillary hair and saliva from 178 individuals with occupational exposure to heavy metals. Levels of metal compounds were determined by atomic absorption spectrometry. We collected information on occupation, lifestyle habits and food intake by questionnaire. Multiple linear regression analyses for metal ion concentration in whole blood, urine, axillary hair and saliva were adjusted for age, gender, smoking and alcohol consumption, lifetime workplace exposure, residence area and food habits. Overall, blood and urine median concentrations found for the five metals analyzed do not exceed biological exposure indexes, so that they are very similar to a non-occupationally exposed population. Toxicokinetic differences may account for the lack of correlations found for metal levels in hair and saliva with those in blood or urine. For those heavy metals showing higher median levels in blood with respect to hair (Cd, Mn and Pb) indicating lesser hair incorporation from blood, the lifetime working experience was inversely correlated with their hair levels. The longer the lifetime working experience in industrial environments, the higher the Mn and Ni concentration in saliva. Axillary hair and saliva may be used as additional and/or alternative samples to blood or urine for biomonitoring hair Mn, and saliva Ni in subjects with occupational exposure.     

Consumption of homegrown products does not increase dietary intake of arsenic, cadmium, lead, and mercury by young children living in an industrialized area of Germany

The dietary intake of arsenic (As), cadmium (Cd), mercury (Hg), and lead (Pb) was studied among young German children with different food consumption behaviour (consumption of own grown foodstuffs and of products from the supermarket). The study area comprised an industrialized and a rural area of West Germany. Dietary intake of contaminants was measured by the duplicate method according to the WHO guideline. A total 588 duplicate portions were collected daily from 84 individuals between May and September 1998. Intake of food groups was calculated from dietary records. Determination of As, Cd, Hg, and Pb was performed following high-pressure digestion of lyophilized samples by atomic absorption spectrometry (AAS). Geometric mean weekly intake [microg/(kgbw x week)] was as follows: As 1.4, Cd 2.3, Hg 0.16, and Pb 5.3. Geometric mean intake corresponded to the percentage of the provisional tolerable weekly intake (PTWI) as follows: As 9.7%, Cd 32%, Hg 3.3%, Pb 21%. As and Hg intake were mainly influenced by fish consumption. The amount of cereals and bakery wares mainly determined the Cd and Pb intake. Children living in the industrialized area with a substantial food consumption of own grown vegetables or products from domestic animals products had no increased dietary intake of the metals.     

Quantities and associations of lead, zinc, cadmium, manganese, chromium, nickel, vanadium, and copper in fresh Mississippi delta alluvium and New Orleans alluvial soils

The topic of this study is the effect of anthropogenic metals on the geochemical quality of urban soils. This is accomplished by comparing the metal contents and associations between two alluvial soils of the lower Mississippi River Delta, freshly deposited alluvial parent materials and alluvial soils collected from a nearby urban environment. Fresh alluvium samples (n = 97) were collected from the Bonnet Carré Spillway. The urban alluvial soil samples (n = 4026) were collected from New Orleans and stratified by census tracts (n = 286). The Spillway samples tend to have less Pb and Zn than generally noted for the baseline of natural soils. Except for Mn and V, Spillway alluvium contains significantly less metal than urban soils. For Spillway samples, the median metal content (in microg g(-1)) is 4.7 Pb, 11.1 Zn, 0.7 Cd, 164 Mn, 0.8 Cr, 3.9 Ni, 3.2 V, and 3.9 Cu. For urban soils, the median metal content (in microg g(-1)) is 120 Pb, 130 Zn, 3.2 Cd, 138 Mn, 2.1 Cr, 9.8 Ni, 3.8 V, and 12.7 Cu. Metal associations also differ between Spillway alluvium and urban alluvial soils. Fresh alluvium correlation coefficients between individual metals vary from 0.87 to 0.99 (P < 10(-13)) except for Cr which ranges from 0.57 to 0.68 (P < 10(-7)). The urban soil correlation coefficients for metals and the index value are 0.40-0.98. In urban soils, Pb, Zn, Cr, and Cu are dominant metals and highly associated, with a correlation coefficient ranging from 0.83 to 0.98 (P < 10(-25)). Their strong association justifies the use of GIS to map the integrated soil metal index (sum of the medians of metals by census tract) of New Orleans. Although also positively correlated (0.40-0.68, P < 10(-10)), Cd, Mn, Ni and V differ in their distribution in the city compared to Pb, Zn, Cr and Cu. Overall, significantly higher metal values occur in the inner city and lower values occur in outlying areas. The human health impact of the mixture of metals is not well understood. This study provides empirical data about the mixture and distribution of metals in New Orleans alluvial soils. Given common technical development, especially of traffic flows in cities, similar patterns of soil metals are expected for all US cities and probably international cities as well. Primary prevention of urban metal accumulations is necessary to enhance and sustain the development of urban culture.     

Levels of lead,cadmium, zinc and copper in the blood of an urban population

Levels of lead, cadmium, zinc and copper were measured in the blood of normal children and adults of Greater Bombay, India using differential pulse anodic stripping voltammetry. The median concentrations of Pb, Cd, Zn and Cu in the whole blood of children and adults were 11.54, 0.21, 484.2 and 86.2 μg dl⁻¹, respectively. The blood lead concentration showed an increase with age. Children living in industrial zones with high vehicular traffic have significantly higher blood lead concentrations than their counterparts living in the cleaner suburban parts of the city. The mean levels of Pb, Cd, Zn and Cu in blood of Bombay children and adults are compared with those from other countries.     

Blood lead level and its relationship to certain essential elements in the children aged 0 to 14 years from Beijing, China

Objective

To investigate blood lead level and its relationship to copper, zinc, calcium, magnesium and iron in the children aged 0 to 14 years old from Beijing, China.

Methods

We classified 3181 children into one of the four groups: Group A (n = 783, < 1 year old); Group B (n = 1538, 1-3 years old); Group C (n = 443, 3-7 years old); and, Group D (n = 417, 7-14 years old). All these metal elements were determined by atomic absorption spectrometry.

Results

The blood lead level was 0.207 ± 0.105 μmol/L. There was a significant gender difference for zinc (P < 0.05) in Group C, and there was also a significant gender difference for copper (P < 0.05) and lead (P < 0.05) in Group D. Controlling for gender and age, we observed that there was a negative correlation of lead with zinc (r = − 0.052, P < 0.01), magnesium (r = − 0.042, P < 0.05) and iron (r = − 0.031, P < 0.05), respectively. Furthermore, in the children aged 1-7 years old, we also found there was a negative linear correlation of lead with zinc, magnesium and iron, respectively (P < 0.01).

Conclusion

Blood lead level in children from Beijing was markedly decreased. And deficiency of zinc, magnesium and iron is related to the elevated blood lead level in the children aged 1-7 years.     

Levels of cadmium, mercury and lead in otter and mink faeces from the United Kingdom

Over 500 faeces of otter (Lutra lutra) from Britain, with a small sample from northeast Greece, were analyzed for Cd, Hg and Pb. A small sample of mink (Mustela vison) faeces was also analyzed. Mean concentrations of metals (mg kg-1 dry weight) in otter faeces ranged from 1.53 to 3.97 Cd, 0.25 to 0.74 Hg and 12.4 to 20.9 Pb. Mink faeces generally contained less Cd and Hg, but more Pb. Metal concentrations in faeces may reflect both natural and anthropogenic sources. Estimates of daily Cd and Pb intake were made from faecal concentrations and these were in good agreement with concentrations in major fish prey. The estimates of daily Cd and Pb intake are high, but nevertheless most samples came from thriving otter populations. The value of faecal analysis in assessing metal burdens during surveys of otters is discussed.     

Factors affecting the concentrations of cadmium, zinc, copper and lead in the sediments of the Vesdre River

The main factors influencing Cd, Zn, Cu and Pb concentrations in the sediments of the highly polluted Vesdre River (eastern Belgium) have been investigated. Only negative correlations were demonstrated between the clay content and heavy metals. The composition of the clay minerals could partially explain this paradox. However, the pretreatment of the minerals might influence the geochemical data obtained from analysis. Iron-hydroxides and phosphates seem to be the main sinks for Pb, Cd and Zn whereas organic components might play a less important role.     

Zinc, cadmium and lead in water, sediments and submerged plants of the Derwent Reservoir, Northern England

A partial budget is presented of the zinc, cadmium and lead entering the Derwent Reservoir. The mean levels in the water column upstream of the site of inflow are: Zn, 0.216 mg 1⁻¹ ; Cd, 0.003 mg 1⁻¹; Pb, 0.065 mg 1⁻¹; the levels after passage through the 4.1 km² reservoir fall by: Zn, 70.3%; Cd, 98.3%; Pb, 89.2%. Most of these metals are deposited in sediments, the mean values for which are: Zn, 1035 μg⁻¹; Cd, 13μg⁻¹; Pb, 827μg⁻¹. Lead, a higher percentage of which occurs as particulate material, is deposited more rapidly than zinc; this effect is especially obvious when streaming of colder water along the bottom of the reservoir takes place at the time of floods. Macroscopic plants are only occasional in this reservoir, due perhaps in part to heavy metal toxicity. Of the two most common submerged species, Nitella flexilis probably accumulates almost all of its metal content directly from the water, but the data suggest that sediments are a source of some of the heavy metals accumulated by Glyceria fluitans.     

Survey of arsenic and other heavy metals in food composites and drinking water and estimation of dietary intake by the villagers from an arsenic-affected area of West Bengal,India

An investigation of arsenic, copper, nickel, manganese, zinc and selenium concentration in foodstuffs and drinking water, collected from 34 families and estimation of the average daily dietary intake were carried out in the arsenic-affected areas of the Jalangi and Domkal blocks, Murshidabad district, West Bengal where arsenic-contaminated groundwater (mean: 0.11 mg/l, n=34) is the main source for drinking. The shallow large diameter tubewells, installed for agricultural irrigation contain an appreciable amount of arsenic (mean: 0.094 mg/l, n=10). So some arsenic can be expected in the food chain and food cultivated in this area. Most of the individual food composites contain a considerable amount of arsenic. The mean arsenic levels in food categories are vegetables (20.9 and 21.2 microg/kg), cereals and bakery goods (130 and 179 microg/kg) and spices (133 and 202 microg/kg) for the Jalangi and Domkal blocks, respectively. For all other heavy metals, the observed mean concentration values are mostly in good agreement with the reported values around the world (except higher zinc in cereals). The provisional tolerable daily intake value of inorganic arsenic microg/kg body wt./day) is: for adult males (11.8 and 9.4); adult females (13.9 and 11); and children (15.3 and 12) in the Jalangi and Domkal blocks, respectively (according to FAO/WHO report, the value is 2.1 microg/kg body wt./day). According to WHO, intake of 1.0 mg of inorganic arsenic per day may give rise to skin lesions within a few years. The average daily dietary intake of copper, nickel and manganese is high, whereas for zinc, the value is low (for adult males: 8.34 and 10.2 mg/day; adult females: 8.26 and 10.3 mg/day; and children: 4.59 and 5.66 mg/day) in the Jalangi and Domkal blocks, respectively, compared to the recommended dietary allowance of zinc for adult males, adult females and children (15, 12 and 10 mg/day, respectively). The average daily dietary intake of selenium microg/kg body wt./day) is on the lower side for the children (1.07 and 1.22), comparable for the adult males (0.81 and 0.95) and slightly on the higher side for the adult females (1.08 and 1.26), compared to the recommended value (1.7 and 0.9 microg/kg body wt./day for infants and adults, respectively).     

Total arsenic, lead, and cadmium levels in vegetables cultivated at the Andean villages of northern Chile

Various vegetables (broad beans, corn, potato, alfalfa and onion) were sampled in northern Chile, Antofagasta Region. They are the basis of human nutrition in this region and of great relevance to human health. This region is characterized by volcanic events (eruptions, thermal springs, etc.). Most of the vegetables cultivated in this area enter the local markets for a population of approximately 4000 people, whose ancestors were mainly atacame?os and quechuas (local indigenous people). The cadmium and lead in these foods was determined by differential pulse anodic stripping voltammetry (DPASV). Results indicate that the highest concentration of Pb and Cd are in the potato skin, while the edible part of the potatoes contained a lower concentration of these metals. The INAA analyses of As in the vegetables from Socaire and Talabre, two towns located close to active volcanoes (e.g. Lascar), show a very high As content: 1850 microg/kg in corn (Socaire) and 860 microg/kg in potatoes (+ skin) (Talabre). These values exceed the National Standard for arsenic (500 microg/kg) by approximately 400% and 180%, respectively. In general, the data show a concentration of Pb greater than Cd with the potential for some vegetables to accumulate heavy metals, The values, expressed in fresh weight, vary from 0.2 to 40 microg/g for Cd and from 0.6 to 94 microg/g for Pb. These concentration intervals, except that of arsenic, are within the recommended standards in the Food Sanitary Regulation (Decree 977), which, expressed as fresh weight, must be equal to or smaller than 500 microg/kg for Pb. There is no legal standard for Cd.     

综合物探方法在青海祁连泽里镍钴矿勘查中的应用

祁连泽里地区基性—超基性岩较发育,具有形成岩浆型硫化物镍钴矿(化)体的地质条件。由于研究区地表覆盖较厚,本次工作结合区域地质、物化探特征,在其所圈定的镍钴成矿有利地段开展了以地面高精度磁测和激电中梯为组合方式的综合物探找矿应用研究。利用地面高精度磁测来圈定区内基性—超基性岩分布,研究其磁性特征、异常展布规模并配合激电中梯剖面测量成果,提出一套寻找超基性岩镍钴矿的方法组合。此次成果表明找矿方式效果显著,对同类地质成矿背景的隐伏镍钴多金属矿勘查工作具有一定的参考价值。     

Effect of dissolved organic carbon on the mobility of cadmium, nickel and zinc in leachate polluted groundwater

The ability of dissolved organic carbon (DOC) from landfill leachate polluted groundwater to form complexes with the heavy metals cadmium (Cd), nickel (Ni) and zinc (Zn) was investigated. The DOC samples originated from the leachate pollution plume at Vejen Landfill, Denmark and were studied in the original matrix with a minimum of manipulation. The experiments were performed as batch sorption experiments and the metal distribution between the aquifer material and the solution (K_d) was determined in the leachate polluted groundwater samples and in reference solutions of synthetic inorganic leachate. The difference in distribution coefficients was a direct indication of complex formation between DOC and heavy metals. The results showed, that DOC from landfill leachate polluted groundwater has the ability to form complexes with Cd, Ni and Zn, and the distribution coefficients were a factor of 2–6 lower in the presence of DOC. Based on the distribution coefficients, the relative migration velocities of the heavy metals were estimated. The migration velocity of the metals was increased by the presence of DOC but did not exceed 1.2% of the water migration velocity, indicating that the effect of DOC on the mobility of Cd, Ni and Zn may have only minor environmental importance. Conditional complex formation constants (log K_c) were estimated from the K_d-values. The constants for 1:1 complexes increased slightly in the following order Zn < Cd < Ni. However, increasing the metal concentration into the mg l⁻¹ level decreased the constants by about one order of magnitude, showing the importance of determining the constants at environmentally relevant metal concentrations.     

Concentration differences between serum and plasma of the elements cobalt,iron, mercury,rubidium, selenium and zinc determined by neutron activation analysis

The differences in concentrations of cesium, cobalt, iron, mercury, rubidium, selenium and zinc between serum and plasma were examined with the aid of instrumental neutron activation analysis. Eighty serum and plasma samples obtained from 13 donors were compared. Serum was prepared in plastic tubes immediately after clotting, and plasma was separated with heparin as anticoagulant. No significant differences in the concentrations of cesium, cobalt, mercury and selenium were observed. However, the concentrations of iron, rubidium and zinc were significantly higher in serum than in plasma. The average differences were 322, 12 and 20 ng/ml for iron, rubidium and zinc, respectively. The average differences found for cesium, rubidium and zinc were far below that which can be expected from a complete, or considerable release of these elements from platelets which aggregate or disintegrate during the clotting process in preparing serum.