Determination of trace elements in human serum by energy dispersive X-ray fluorescence

Feasibility of Lead Exposure Assessment in Blood Spots using Energy-Dispersive X-ray Fluorescence

Collecting blood spots from newborns is a common procedure used to diagnose multiple health conditions. Fingerstick blood samples are routinely collected from children to diagnose elevated blood lead levels. In our study, we wanted to test the feasibility of using a high-power energy-dispersive X-ray fluorescence (EDXRF) device to accurately measure the concentration of lead in blood spots. We created spotted standards of a known concentration of lead on a filter paper at different volumes and concentrations. We determined the detection limit for lead through repeated measurements of our standards and calibration line slopes. We also tested the variability of the measured lead concentration across procedures and spotted blood volumes and found no significant additions to uncertainty in measurements. Finally, we compared blood lead concentrations measured by EDXRF and atomic absorption spectroscopy (AAS) and found EDXRF to be a significant predictor of blood lead (n = 22, R = 0.98, p value <0.001) with an average detection limit of 1.7 μg/dL of blood lead. This detection limit is similar to that of the AAS technique, which is commonly used in clinical testing laboratories for blood lead surveillance. These findings provide a proof of concept that blood spots measured by EDXRF may be used as a surveillance tool for lead exposure, even at elevated blood lead levels of 2-3 μg/dL.

Investigative Analysis of Lanthanum Oxide Nanoparticles on Elements in Bone of Wistar Rats After 30 Days of Repeated Oral Administration

Accumulation of lanthanum oxide nanoparticles (La₂O₃NPs) in the femur bone of rats after 30 days of oral administration was explored. Also, the influence of La₂O₃NPs on macro and trace elements in the rats' femur bone was assessed. Inductively coupled plasma mass spectrometry (ICP-MS) and inductively coupled plasma optical spectrometry (ICP OES) were used for total element determination in the bone after decomposition while laser ablation-ICP-MS (LA-ICP-MS) was used to investigate element distribution (bio-imaging) in the bone. Some differences in element concentrations in the bone between the rats treated with La₂O₃NPs at 1.0 mg kg^-1 (T1), 10.0 mg kg^-1 (T2), and 100 mg kg^-1 (T3) body weight (bw) and the control rats (CTR) were observed. More differences were observed in the bone of rat treated with 10.0 mg kg^-1 La₂O₃NPs bw. However, the highest change observed was for Mg, which concentration ranged from 5230 ± 12 μg kg^-1 for the CTR group to 4130 ± 138 μg kg^-1 for the T3 group. Minor changes were observed for Ba, Ca, Cr, Cu, Fe, Mg, Na, Pb, Sr, and Zn between CTR and animals treated with La₂O₃NPs at the different levels of concentration. It was possible to observe from LA-ICP-MS analysis that La₂O₃NPs were accumulated only on the surface of the bone, not deeper than about 5 μm. LA-ICP-MS allowed also to investigate the distribution of La and the other elements in a cross section of the femur bone head, where higher amounts of the elements are present at the external part of the bone. Therefore, it was demonstrated that La₂O₃NPs are incorporated on the surface of the bone and it has a small influence on some of the other elements evaluated.

Spatial distribution of the trace elements zinc, strontium and lead in human bone tissue

Trace elements are chemical elements in minute quantities, which are known to accumulate in the bone. Cortical and trabecular bones consist of bone structural units (BSUs) such as osteons and bone packets of different mineral content and are separated by cement lines. Previous studies investigating trace elements in bone lacked resolution and therefore very little is known about the local concentration of zinc (Zn), strontium (Sr) and lead (Pb) in BSUs of human bone. We used synchrotron radiation induced micro X-ray fluorescence analysis (SR μ-XRF) in combination with quantitative backscattered electron imaging (qBEI) to determine the distribution and accumulation of Zn, Sr, and Pb in human bone tissue. Fourteen human bone samples (10 femoral necks and 4 femoral heads) from individuals with osteoporotic femoral neck fractures as well as from healthy individuals were analyzed. Fluorescence intensity maps were matched with BE images and correlated with calcium (Ca) content. We found that Zn and Pb had significantly increased levels in the cement lines of all samples compared to the surrounding mineralized bone matrix. Pb and Sr levels were found to be correlated with the degree of mineralization. Interestingly, Zn intensities had no correlation with Ca levels. We have shown for the first time that there is a differential accumulation of the trace elements Zn, Pb and Sr in BSUs of human bone indicating different mechanisms of accumulation.

Redox-mediated mechanisms and biological responses of copper-catalyzed reduction of the nitrite ion in vitro

During ischemia nitrite may be converted into nitric oxide (NO) by reaction with heme-carrying proteins or thiol-containing enzymes. NO acts as a regulator of vasodilation and protector against oxidative stress-induced tissue injuries. As a result of ischemia-induced oxidative stress, hypoxia and/or acidosis bivalent copper ions (Cu(2+)) can dissociate from their physiological carrier proteins. Reduced by the body's own antioxidants, the resultant Cu(1+) might represent an effective reductant of nitrite. Here we have evaluated in vitro copper-dissociation from copper/BSA (bovine serum albumin) complexes under ischemic conditions. Furthermore, using physiological concentrations, we have characterized the capacity of antioxidants and bivalent copper ions to serve as Cu(1+)-agitated catalytic sites for nitrite reduction and also the biological responses of this mechanism in vitro. We found that as a consequence of an acidic milieu and/or oxidative stress the copper-binding capacity of serum albumin strongly declined, leading to significant dissociation of copper ions into the ambient solution. At physiologically relevant pH-values Cu(2+) ions in combination with physiologically available copper reductants (i.e., ascorbate, glutathione, Fe(2+)) significantly enhanced nitrite reduction and subsequent non-enzymatic NO generation under hypoxic but also normoxic conditions. Our data demonstrate for the first time that upon ischemic conditions carrier protein-dissociated copper ions combined with appropriate reductants may serve as Cu(1+)-driven catalytic sites for nitrite reduction, leading to the formation of biologically relevant NO formation. Thus, in addition to the action of heme proteins, copper-catalyzed non-enzymatic NO formation from nitrite might represent a further physiologically relevant vasodilating and NO-dependent protective principle to ischemic stress.

Potassium in skeletal muscle in untreated primary hypertension and in chronic renal failure, studied by X-ray fluorescence technique

Muscle biopsy specimens form 22 patients with primary hypertension, 10 patients with chronic renal failure and 21 healthy normotensive controls were analyzed using a Kevex 0600 X-ray spectrometer. Muscle potassium (MK), calcium (MCa), sulphur (MS) and phosphorus (MP) were determined. In the patients with primary hypertension, MK was decreased compared to the controls (p less than 0.001), MCa was increased (p less than 0.05), MS was decreased (p less than 0.05) and no difference was seen in MP. In the patients with chronic renal failure, MK was decreased compared to the controls (p less than 0.001), MCa showed no difference compared to the controls, whereas both MP and MS were lower (p less than 0.05 and p less than 0.001). It was concluded that intracellular potassium is low both in primary hypertension and chronic renal failure. In chronic renal failure the potassium decrease is probably secondary to loss of cellular potassium capacity, whereas in primary hypertension an inhibition of the sodium, potassium, adenosine triphosphatase is suggested as the cause of the low potassium.

X-ray fluorescence analysis of geological samples: exploring the effect of sample thickness on the accuracy of results

The accuracy of the simple quantitative method of elemental XRF analysis applied to thick and thin geological samples was investigated with certified reference materials. In the case of thick samples, the intensity of the calcium signal was used as a characteristic of the sample for the dark matrix correction, as it had been found to be inversely correlated with the intensity of the silicon signal. The results of the analysis of thick samples did not depend on the sample form (pressed disc or a powder in a cup), and the absorption factors were very high. In the analysis of thin samples, the detection limits, sensitivity, and accuracy have been improved, particularly for light elements. As the absorption factors are close to unity for thin samples, there is no need for a matrix-effect correction or certified reference materials.

Cadmium, copper and zinc in tissues of deceased copper smelter workers

Workers at a copper and lead smelter in northern Sweden have a multifactorial exposure to a number of heavy metals. The concentrations of cadmium, copper and zinc in liver, lung, kidney and brain tissues have been determined by atomic absorption spectrometry in 32 deceased long-term exposed male lead smelter workers, and compared with those of 10 male controls. Furthermore, copper and zinc levels in hair and nails were determined by energy-dispersive X-ray fluorescence. The highest cadmium concentrations among both workers and controls were observed in kidney, followed in order by liver, lung and brain. The levels in kidney, liver and lung were all significantly higher in the workers than in the controls (p < 0.03). Among the workers relatively strong positive correlations (p < 0.03) were observed between cadmium concentrations in liver and lung, liver and kidney, liver and brain, and lung and brain. In the exposed workers a positive correlation was observed between cadmium and zinc concentrations in the kidney (rs = 0.38; p = 0.034). This is probably mainly due to the protein metallothionein, which is stored in the kidney, binding equimolar amounts of these two metals. The highest concentrations of copper were found in hair and nails among both workers and controls, followed in order by liver, brain, kidney and lung. The tissue concentrations of copper in brain, lung and kidney were all significantly higher among the smelter workers than in the controls (p < 0.036). Copper levels in lung and age at time of death were positively correlated among the exposed workers (rs = 0.39; p = 0.029). In the same group, positive correlations between copper and zinc concentrations in kidney (rs = 0.45; p = 0.009) and nails (rs = 0.68; p < 0.001) were also observed, reflecting possible biological interactions between these two metals. Among both workers and controls, the highest zinc concentrations were found in hair, followed in order by nails, liver, kidney, brain and lung. Significantly higher tissue concentrations among the workers as compared with the reference group were noted in kidney, liver and brain (p < 0.033). Neither copper nor zinc concentrations in hair and nails seemed to provide a useful measure of the trace element status of the smelter workers.

Metal exposure from amalgam alters the distribution of trace elements in blood cells and plasma

Twenty-seven consecutive patients with health problems associated with dental amalgam were recruited. In spite of thorough medical examinations, there were no diagnoses available. The patient group was dominated by women. A healthy age- and sex-matched control group with dental amalgams without symptoms was also recruited. Metal level monitoring in plasma and nuclear microscopy of isolated individual blood cells were carried out. Significant increases of copper, iron, zinc and strontium were found in patient plasma. There was no significant difference in plasma selenium between the groups. Mercury was significantly increased in patient plasma, although there was overlap between the groups. In erythrocytes a significant increase in calcium and a significant decrease in magnesium, copper, manganese and zinc were found. Calcium, magnesium, manganese and copper increased in patient neutrophil granulocytes. A significant decrease was found for zinc. A conspicuous finding was the presence of measurable mercury in a few of the cells from the patient but not in the control group. Thus, nuclear microscopy of isolated individual blood cells might provide a better diagnostic tool for metal exposure than blood plasma measurements.

The effect of dietary selenium deficiency on acute colorectal mucosal nucleotoxicity induced by several carcinogens in the rodent

BACKGROUND

Selenium (SE) has been inversely associated with colon cancer risk. Two potential mechanisms of this effect were examined in a rodent short-term carcinogenesis assay: whether dietary SE deficiency altered the initiation aspect of carcinogenesis in the colon, and whether SE altered carcinogen metabolism.

SETTING

Animal laboratory.

SUBJECTS

52 Sprague-Dawley rats, divided into a SE diet deficient group (0.002 parts per million; ppm) and a SE sufficient (0.2 ppm) group.

ENDPOINTS

Weight, serum SE concentration, and karryorhectic index (KI), which is a measure of acute carcinogen induced nuclear toxicity in the colonic mucosa.

METHODS

After three weeks of acclimation to the diets, eight animals from each dietary group were injected with one of the following: dimethylhydrazine (DMH), a colon specific carcinogen, its metabolite, methylazoxymethanol (MAM), or 0.9% sodium chloride. Twenty-four hours after injection the colons were removed, blood drawn, and the stained colons assayed for nuclear aberrations.

RESULTS

No weight differences were generated by the dietary variations. Low-dietary SE resulted in serum SE declining markedly in the study period to 6 ng/ml versus 33 ng/ml in the SE sufficient group. Diet alone, and variations in weight gain, did not alter the KI. Both carcinogens greatly increased the KI in both the left and right colon. A SE-deficient diet was associated with a higher KI in both carcinogen groups in the right colon, with statistical significance for both the left and right colon in the MAM injection group.

CONCLUSIONS

Dietary SE deficiency is associated with increased KI of the colon in MAM treated rats. SE, therefore, has a protective effect in the initiation phase of carcinogenesis.

Psychological and somatic subjective symptoms as a result of dermatological patch testing with metallic mercury and phenyl mercuric acetate

Sixty patients with a history of malaise over the ensuing weeks following the drilling out of old amalgam fillings were included in the study. They were tested epicutaneously weekly (standard procedure) with either 0.5% metallic mercury in petrolatum or 0.01% phenyl mercuric acetate in water, and, on 2 separate occasions, with only saline or petrolatum as a control according to a randomized double-blind protocol. The presence or absence of an allergic patch test response was read on day 3. Two patients showed allergic cutaneous responses towards metallic mercury and 1 to phenyl mercuric acetate. There was a concurrent 7-day self-registration of subjective psychological and somatic symptoms, using a validated visual analogue scale (minor symptom evaluation profile; MSE). In the group analysis it was clearly shown that the patients reacted with subjective symptoms to phenyl mercuric acetate. A reaction to test doses of metallic mercury seems to exist but could only be visualized when a scoring system was elaborated to individually define those subjects with a psychological and somatic response to test doses of mercury. This psychosomatic reactivity, named intolerance, seems to be unrelated to the cutaneous delayed allergic skin response. Thus, it might be possible to identify patients intolerant to small test doses of percutaneously penetrating mercury (previously considered innocuous). These findings may have a bearing on the systemic side-effects attributed to mercury released from amalgam tooth fillings.

Lead in tissues of deceased lead smelter workers

Smelter workers are exposed to a number of metals and other substances in dust, fumes and gases. The concentrations of lead in liver, lung, kidney, brain, hair and nails were determined in 32 deceased, long-term exposed male lead smelter workers, and compared with those of 10 male controls. The lead levels in liver, lung, kidney and brain were analyzed by atomic absorption spectrophotometry. X-ray fluorescence was used for the determinations in hair and nails. Lead in blood had been determined repeatedly in the lead workers since 1950, which made it possible to calculate a time-integrated blood lead index for each worker. The highest lead levels in soft tissues were found in liver, followed in order of concentration by kidney, lung and brain, among both exposed workers and controls. These organ lead concentrations were all significantly higher among the workers as compared with the control group (p < or = 0.02). The largest difference between workers and controls was found in brain tissue (ratio between median values = 5.6). The lead levels in hair and nails were of the same magnitude in the two groups. The workers showed positive correlations between lead concentrations in liver and kidney (Spearman's rho = rs = 0.59; p < 0.001), liver and hair (rs = 0.51; p = 0.003), liver and nails (rs = 0.52; p = 0.002) and hair and nails (rs = 0.52; p = 0.002). Lead concentrations in kidney correlated well with lead levels in hair (rs = 0.57; p = 0.001) and nails (rs = 0.51; p = 0.003), respectively. The positive correlation between the lead concentrations in liver and kidney indicates that these organs belong to the same soft tissue lead pool in the body. In retired lead workers, positive correlations were observed between the lead concentrations in liver and the cumulative blood lead index (CBLI) (rs = 0.50; p = 0.016), as well as between lead levels in kidney and CBLI (rs = 0.51; p = 0.014).

Markers for vulnerability in acute porphyria. A hypothesis paper

Previously symptomatic and permanently asymptomatic carriers of a gene mutation for acute intermittent porphyria as well as matched controls were screened with regard to a series of variables of possible relevance to the development of porphyric symptoms. The basis for the study was a concept of acute porphyria as a condition of a permanent system overload of oxidative stress, with long term effects on hepatic and renal tissue, and with instances of periodic overload of free radicals giving rise to acute neurologic involvement. Leukocyte concentrations of manganese, calcium, iron and zinc, as well as erythrocyte calcium differed between the groups, acute intermittent porphyria gene carriers, irrespective of previous porphyric illness, showing significantly higher levels than the controls. Manganese was found to be the most discriminative component of all the 78 variables investigated, accounting for about 98 per cent of the variance between the groups. An increment, by a factor of four, in cellular manganese is suggestive of an increase, in acute intermittent porphyria, of a manganese associated enzyme, e.g. glutamine synthetase, pyruvate carboxylase or mitochondrial superoxide dismutase. The best fit into the model considered is provided by a theory focused on superoxide dismutase, induced in response to superoxide anion radical produced from aminolaevulinic acid. In porphyria gene carriers seemingly resistant to porphyric manifestations, an increase in potentially prooxidant cellular iron is matched by a proportional increment in manganese, i.e. presumably by a corresponding mitochondrial superoxide dismutase induction. This mechanism is not operative in porphyric individuals prone to development of neuropsychiatric symptoms. In acute intermittent porphyria with a history of porphyric illness there is a positive correlation between erythrocyte manganese and serum folate and a negative correlation between leukocyte ferrochelatase activity and serum cobalamin concentration. This may mirror a role of the cobalamin-folate system in the acute porphyric process.

Determination of iodine and bromine in plasma and urine by inductively coupled plasma mass spectrometry

The simultaneous determination of iodine and bromine in plasma and urine by inductively coupled plasma mass spectrometry, using a Nermag prototype instrument, is described. The sample preparation involves only a 10-fold dilution with a diluent containing europium as an internal standard followed by direct nebulisation in the plasma. The iodine, bromine and europium ions are measured at m/z = 127, 79, and 153, respectively. The sensitivity of the method, with detection limits of 1.6 and 52 micrograms l-1 for iodine and bromine, respectively, is satisfactory for clinical applications. The calibration graphs were linear over the ranges 0-400 micrograms l-1 and 0-40 mg l-1 for iodine and bromine, respectively, which are wide enough for most assays. The recoveries were close to 100% with coefficients of variation of less than 3%. The within-day and between-day reproducibility was about 5%. The concentrations of iodine and bromine in the plasma of 26 healthy individuals were 58 +/- 12 micrograms l-1 and 4.1 +/- 0.9 mg l-1, respectively. The amounts of iodine and bromine eliminated in urine were 94 +/- 97 micrograms per 24 h (range 27-403 micrograms per 24 h) and 3.6 +/- 1.7 mg per 24 h, respectively. These results are in agreement with reported values.

Screening for selected trace elements in single cell populations by energy dispersive X-ray fluorescence spectrometry

An adaptation of the thin film approach to energy dispersive X-ray fluorescence spectrometry (EDXRF) is described, which provides for a screening analysis for Fe, Ni, Cu, Zn, Se, and Cd in K-562 leukemic cells incubated in various metal-enhanced cultures. Valuable quantitative and semiquantitative data can be obtained on as few as 400,000 cells.

Development of a validation test for self-reported abstinence from smokeless tobacco products: preliminary results

Using X-ray fluorescence spectrometry, 11 heavy elements at concentrations that are easily detectable have been identified in smokeless tobacco products. These concentrations were found to increase in cheek epithelium samples of the user after exposure to smokeless tobacco. This feasibility study suggests that the level of strontium in the cheek epithelium could be a valid measure of recent smokeless tobacco use. It also demonstrates that strontium levels become undetectable within several days of smokeless tobacco cessation. This absence of strontium could validate a self-report of abstinence from smokeless tobacco. Finally, the X-ray spectrum of heavy metal content of cheek epithelium from smokeless tobacco users could itself provide a visual stimulus to further motivate the user to terminate the use of smokeless tobacco products.

Rapid and simple determination of selenium and other trace elements in very small blood samples by XRF

Selenium and other trace elements (Cu, Zn, Br, and Rb) were determined in very small (0.75 microL) human serum and mice whole blood samples, by an XRF method. Accurate results of elemental concentration were obtained without the need of exact volume measurement, because of the backscatter correction used. The XRF method is highly sensitive (M.D.L. = 0.06, 0.13, 0.09, 0.07, and 0.05 ppm for Se, Cu, Zn, Br, and Rb, respectively), rapid (counting time--100 s/sample), easy to perform and therefore suitable for routine trace element analyses. The results obtained are in good agreement with the values reported in the literature.

The role of crevicular fluid iron in periodontal disease

This article presents a brief review of literature on the role of iron in infection and reports the concentration of iron in crevicular fluid (CF) in humans and beagle dogs. Crevicular fluid from human subjects was collected from gingivitis and periodontitis sites. The CF from beagle dogs was collected from gingivitis and active periodontitis (ligature-induced) sites. The results showed that the concentration of iron in human CF was often higher than in human serum. Also, a comparison between CF collected from gingivitis sites and periodontitis sites revealed a significantly higher concentration of iron in CF collected from the periodontitis sites. The studies in ligature-induced periodontitis in beagle dogs revealed at least a 3-fold increase in iron concentration in CF following ligation compared to the preligation values. Based on the available literature it is suggested that high concentration of iron in CF is not due to serum transferrin or polymorphonuclear leukocyte lactoferrin. Also, this high concentration of iron in CF might play an important role in enhancement of growth and virulence of microorganisms of the subgingival plaque and the initiation of active periodontitis.

Analytical approaches for biomedical elemental analysis

Several different analytical systems are available for biomedical elemental analysis related to human nutrition. The principle, detection limits, analytical artifacts, and applications are presented for the following analytical systems for elemental analysis classified by sample volume: macro volume systems--flame atomic absorption spectroscopy (FAAS) and inductively coupled plasma (ICP); micro volume systems--electrothermal atomization (graphite furnace) atomic absorption spectroscopy (ETA-AAS) and x-ray fluorescence (XRF); and ultramicro volume systems--electron probe x-ray microanalysis (EPX) and laser microprobe mass analysis (LAMMA).