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Trace Element Estimation – Methods _ Clinical Context

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					                                             Published Quarterly
                                             Mangalore, South India
                                             ISSN 0972-5997
                                             Volume 4, Issue 1; January-March 2005



Editorial
Trace Element Estimation – Methods & Clinical Context
Ananth N Rao,
Department of Biochemistry, Amrita Institute of Medical Sciences,
Kochi-682 026, Kerala, INDIA.

Address for Correspondence

Ananth N Rao,
Department of Biochemistry,
Amrita Institute of Medical Sciences,
Kochi- 682 026
Kerala, INDIA.
E-mail: drananthrao@medical.amrita.edu

Citation: Mahajan RK, Walia TPS, Sumanjit. Trace Element Estimation – Methods & Clinical
Context. Online J Health Allied Scs. 2005;1:1

URL: http://www.ojhas.org/issue13/2005-1-1.htm

Open Access Archive: http://cogprints.ecs.soton.ac.uk/view/subjects/OJHAS.html



                                                     Key       Words:       Atomic       Absorption
Abstract: Understanding the effects of trace
                                                     Spectrophotometer,      ICP-MS,       Stripping
metals on human health is as complex as it is
                                                     Voltameter, Colorimetry, Electro Thermal
fascinating. As mentioned earlier, the high
                                                     Vaporization, Neutron Activation Analysis, Laser
concentrations may prove toxic, as also,
                                                     Microprobe Mass Analysis
depletion in the concentration of the essential
trace elements may cause various metabolic
                                                     Introduction
instabilities due to enzyme dysfunction. In the
era of rapid industrialization and technological     Several metal ions such as sodium, potassium,
advances, it is imperative to watch keenly for       magnesium, and calcium are essential to sustain
contamination of the environment and its vital       biological life. At least six additional metals,
composition from heavy metal wastes emanating        chiefly transition metals are also essential for
out of industries. Many metabolic disorders in       optimal growth, development, and reproduction,
man are accompanied by alterations in the            i.e. manganese, iron, cobalt, copper, zinc, and
concentration of one or more trace elements in       molybdenum.
some body fluid, especially blood serum or
plasma It is thus important to update ourselves      An element, which is required in amounts
with various techniques available for such           smaller than 0.01% of the mass of the organism, is
determinations, their operational aspects,           called a trace element. Trace metals function
advantages / disadvantages etc. More recently,       mostly as catalysts for enzymatic activity in
element analysis from hair and nail has been         human bodies. However, all essential trace
stated as the best indices of such contamination     metals become toxic when their concentration
and has also been discussed in this article.         becomes excessive. Usually this happens when



                                                                                                     1
the levels exceed by 40-200 fold those required        contamination,    prevent    adoption     of   such
for correct nutritional response. In addition to the   programs.
metals essential for human life, our diet
including the water we drink and the air we            Specimen Collection: Analyses for trace
breathe may contain toxic metals like mercury,         elements in biological fluids are uniquely
lead, cadmium, chromium, silver, selenium,             susceptible to extreme errors unless special
aluminium, arsenic, and barium. These metals           precautions are taken during collection, storage,
can cause chronic or acute poisoning and should        and analysis. The integrity of the specimen may
be eliminated as much as possible from the living      be compromised before it is analyzed, by
environment.                                           contamination during collection and processing
                                                       or by attenuation of the analyte concentration
Understanding the effects of trace metals on           during storage. If this happens, determined
human health is as complex as it is fascinating.       values are not valid even though the method of
As mentioned earlier, the high concentrations          analysis is extremely sensitive and highly
may prove toxic, as also, depletion in the             accurate. Obstacles to obtaining precise and
concentration of the essential trace elements may      accurate analytical data arising from these factors
cause various metabolic instabilities due to           are discussed. Control procedures applicable at
enzyme dysfunction. Equally, industrial-based          all stages for ascertaining the sources of error and
metallic contamination of the air, soil, and water     eliminating them should be considered.
supplies can have a dramatic impact on our well-
being. Added on to this is the toxic accumulation      In recent years, awareness that trace elements
of these elements due to the intake of various         play a very important role, either beneficial or
drugs.                                                 harmful, in human health has increased. Many
                                                       metabolic disorders in man are accompanied by
In recent years, awareness that trace elements         alterations in the concentration of one or more
play a very important role, either beneficial or       trace elements in some body fluid, especially
harmful, in human health has increased. Many           blood serum or plasma. Interest in trace-element
metabolic disorders in man are accompanied by          research     in    clinical  medicine,    biology,
alterations in the concentration of one or more        environmental studies, toxicology, and nutrition
trace elements in some body fluid, especially          has become an exciting frontier, and during the
blood serum or plasma.(1) Interest in trace-           last two decades the number of publications on
element research in clinical medicine, biology,        this subject has progressively increased. Recent
environmental studies, toxicology, and nutrition       developments in instrumentation have lowered
has become an exciting frontier, and during the        the limits for determining many trace elements to
last two decades the number of publications on         the low nanogram or even picogram range, thus
this subject has progressively increased. Recent       enabling determination of parts per billion
developments in instrumentation have lowered           (ng/g) and, in some cases, even less. The present
the limits for determining many trace elements to      needs for trace measurements and techniques for
the low nanogram or even picogram range, thus          micro- and sub microanalysis are already
enabling determination of parts per billion            substantial, and recent reports indicate that the
(ng/g) and, in some cases, even less.(2) The           requirements and demands for such capabilities
present needs for trace measurements and               will increase considerably. Because most essential
techniques for micro- and sub microanalysis are        trace metals are present in biological specimens
already substantial, and recent reports indicate       in very low concentrations, precise and accurate
that the requirements and demands for such             analysis is most essential if meaningful results
capabilities will increase considerably.(3-6)          are to be obtained. In this context, the various
                                                       factors that influence the precision and accuracy
Because most essential trace metals are present in     of trace-metal analysis must be identified and
biological    specimens       in     very     low      controlled. Contamination and the stability of
concentrations(7), precise and accurate analysis is    standards and controls are among the more
most essential if meaningful results are to be         important of these factors.
obtained. Trace-element supplementation is
becoming widely used for patients undergoing           The reliability of any analyte determination is
total parenteral nutrition therapy. Monitoring         affected by the extent of contamination during
these patients for the elements has been               collection, containment, processing, and analysis
recommended, but resource restrictions and             of the specimen. It is also influenced to a
analytical problems, particularly those related to     considerable extent by the accuracy with which a
                                                       value may be assigned to the standards and (or)



                                                                                                         2
controls and the stability of the specimens,           strong base such as tetramethylammonium
standards, and controls during containment. A          hydroxide (TMAH). When sample preparation
general discussion of the techniques and               was factored into the equation, the elevated
methods for preventing contamination may be            blood lead concentration of 60 µg/dL was
found in the literature. Most practical                reduced to 2–5 µg/dL (20–50 ppb)—virtually
information and the descriptions of useful             identical to the FAA detection limit.
techniques, however, are widely scattered and
not readily accessible.(8)                             An accessory called the Delves Cup was
                                                       developed in the late 1960s to improve the
Methods and Estimations: The development of            detection limit of FAA.(9) The Delves Cup
analytical instrumentation over the past 30–40         approach used a metal crucible or boat usually
years has allowed us not only to detect trace          made from nickel or tantalum, which was
metals at the parts per quadrillion (ppq) level,       positioned over the flame. The 10-100µL sample
but also to know its valency state, biomolecular       was pipetted into the cup and the heated sample
form, elemental species, and isotopic structure.       vapor passed into a quartz tube, which was also
Lead was the most commonly studied of all the          heated by the flame. The ground state atoms
trace elements and the techniques that developed       generated from the heated vapor were
early in time are mostly described on the basis of     concentrated in the tube and therefore remained
their lead estimation capacities. As recently as the   in the optical path for a longer period of time.
early 1960s, trace elemental determinations were       This resulted in much higher sensitivity and
predominantly carried out by traditional wet           lower detection capability, which meant that the
chemical     methods     such     as    volumetric,    elevated blood lead level of 60 µg/dL could be
gravimetric, or colorimetric assays. It wasn’t until   detected with comparative ease. Because of its
the development of atomic spectroscopic (AS)           relative simplicity and low cost of operation, the
techniques, in the early to mid-1960s, that the        Delves Cup became the standard method for
clinical community realized that they had a            carrying out blood lead determinations for many
highly sensitive and diverse trace element             years.
technique that could be automated. Every time
there was a major development in AS, trace             Unfortunately, the Delves Cup approach was
element detection capability, sample throughput,       found to be very operator-dependent and not
and automation dramatically improved.(9) The           very reproducible; sometimes, it involved
developments and recent breakthroughs in               complicated sample preparation and required
atomic spectroscopy have directly affected our         calibration with blood matrix standards. For
understanding of the way trace metals interact         these reasons, the approach became less
with the human body. The major element studied         attractive after the commercialization of Electro
in humans was lead for a long time and various         Thermal Atomization (ETA) in the early 1970s.
methods were devised for this purpose.                 This new approach offered detection capability
                                                       for lead of ~0.1 ppb — 200 fold better than FAA.
Lead assays were initially carried out using the       However, its major benefit for the analysis of
dithizone colorimetric method, which was               blood samples was the ability to dilute and inject
sufficient for the time (late 1950s, early 1960s),     the sample automatically into the graphite tube
but was very slow and labor-intensive. It became       with very little off-line sample preparation. In
more automated with the development of anodic          addition, because the majority of the matrix
stripping voltammetry (9), but blood lead              components were "driven-off" before atomization
analysis was not considered a truly routine            at 2700°C, interferences were generally less than
method until AS techniques became available.           with the Delves Cup, which used a much cooler
                                                       acetylene flame to generate the atoms. This
When flame atomic absorption (FAA) was first           breakthrough       meant    that    blood    lead
developed, an elevated blood lead level was            determinations, even at extremely low levels,
considered to be 60 µg/dL (600 ppb), well above        could now be carried out routinely in an
the FAA detection limit of 2 µg/dL (20 ppb) at         automated fashion.
the time. But when preparation of the blood
samples was taken into consideration, FAA              The next major milestone in AS was the
struggled to meet this level. Preparation typically    development of Zeeman background correction
involved either dilution with a weak acid              (ZBGC) in 1981, which compensated for
followed by centrifuging and filtering, acid           nonspecific    absorption   and    structured
digestion followed by dilution and centrifuging        background produced by complex biological
and filtering, or, more recently, dilution with a      matrices like blood and urine. In conjunction



                                                                                                       3
with the stabilized temperature platform furnace       The lead isotope ratios can be measured using an
(STPF) concept, ZBGC allowed for virtually             Electro Thermal Vaporization (ETV) sampling
interference-free graphite furnace atomic analysis     accessory coupled to the ICP–MS. An ETV
(GFAA) of blood samples.(9) The success of the         system uses a heated graphite tube (similar to
ZBGC/STPF approach, primarily due to the fact          that used in a GFAA), to thermally pretreat the
that it could analyze many different kinds of          sample. But instead of using the tube to produce
samples using simple aqueous standards,                ground state atoms, its main function is to drive
launched it as a method for analyzing most types       off the bulk of the matrix before the analytes are
of complex matrices by GFAA.                           vaporized into the plasma for ionization and
                                                       measurement by the mass spectrometer. The
Although GFAA had been the accepted way of             major benefit of ETV-ICP–MS for this application
doing blood lead determinations for more than          is that complex matrices like blood, gasoline, and
15 years, the commercialization of inductively         pottery clay material can be analyzed with very
coupled plasma–mass spectrometry (ICP–MS) in           little interference from the matrix components.
1983, gave analysts a tool that was not only 50–       An additional benefit with regard to taking blood
100 times more sensitive, but suffered from less       samples is that typically only a 20-50µL aliquot is
severe matrix-induced interferences than GFAA.         required for analysis.
In addition, ICP–MS offered multielement
capability and much higher sample throughput,          A rapid survey of the elements in biological
making it very attractive to the clinical              materials, covering most of the elements in the
community. It must be emphasized that these are        periodic table, is possible by using available
approximate aqueous lead detection limits and          software for semi-quantitative analysis (SEMI-
are shown for comparative purposes. They do            QUANT) by inductively coupled plasma mass
not represent detection levels achievable directly     spectrometry. The procedure takes 5 mm after
in the blood.                                          sample preparation and gives results with a
                                                       precision (CV) of ‘20%. At a 10 fold dilution, 13
An added benefit of the ICP–MS technique is that       elements can be consistently and reliably
it also offers isotopic measurement capability.        detected in serum and 15 elements in whole-
This is a very attractive feature to many clinical     blood samples. At present the most important
labs, because it gives them the ability to carry out   limitation of this method is mass overlap by
isotopic tracer, dilution and ratio (9)                polyatomic species for some elements of interest
measurements, which are beyond the realms of           (e.g., Cr, Mn, and V). However, for the set of
the other traditional AS techniques. In fact, the      elements that can be reliably determined at
isotopic     measurement       capability     allows   endogenous concentrations, including Li, B, Mg,
researchers to actually pinpoint the source of lead    Fe, Cu, Zn, Rb, and Sr, the rapid scanning
poisoning by comparing the isotope ratios of           capability may be useful. Although matrix effects
blood lead samples with those of possible sources      limit the direct interpretation of the semi-
of lead contamination. The principle behind this       quantitative output, reasonable estimates of
approach, known as isotopic fingerprinting, is         concentration are attainable by using matrix-
based on the fact that lead has four naturally         matched standards or by adding a multielement
occurring isotopes: 204Pb, 206Pb, 207Pb, and 208Pb.    standard to an aliquot from one sample in the set.
Thus, when lead is ionized in the plasma, it           We also present an example of determination of
generates four ions, all with different atomic         25 elements in saliva from a patient with
masses. All the lead isotopes, with the exception      extensive dental work: Components of many of
of 204Pb, are radiogenic—the products of               his dental alloys were readily identified. The
radioactive decay of either uranium or thorium.        method may also prove useful for screening
Therefore, their relative abundance varies             multiple toxic exposures to heavier elements,
depending on the rock type and geological area.        such as Pb, Ti, Cd, and Hg.
This means that in all lead-based materials and
systems, 204Pb is the only isotope that has            Determination of a growing number of elements
remained essentially unchanged at 1.4% since the       in body fluids places increasing demands on
earth was first formed. The ratios of the isotopic     clinical laboratories. In part, this demand reflects
concentrations of 208Pb, 207Pb, and 206Pb to that of   an increasing range of occupational and
204Pb will therefore vary depending on the source      environmental exposures. To some extent, an
of lead. This fundamental principle is used to         increasing      awareness        of    multielement
match lead isotope ratios in someone’s blood to a      interactions, and their potential clinical impact,
particular environmental source of lead                underscores the need for comprehensive analysis
contamination.                                         of human body fluids. Although determinations



                                                                                                         4
of elements such as Mg, Fe, Cu, and Zn are                viscous, results for such samples cannot be
unquestionably important, much of the current             accurately compared with those for aqueous
interest in multielement techniques is predicated         calibration solutions. In fact, the most substantial
on the belief that a longer list of elements will         measuring error in AAS is ascribable to
gain importance, as their biological significance         differences in viscosity between samples and
becomes known. However, the elaboration of this           standard.(11) To correct for this, it is therefore
potentially important area of medicine currently          necessary to add some relatively viscous
awaits the development of technologies that               substance such as glycerol to the calibration
facilitate acquisition of reliable data in the clinical   solutions. Because no data on the micromethod
setting. The most common method for                       have been reported, we investigated such
quantitative trace element analysis of biological         procedural correction for viscosity. The current
materials is atomic absorption spectroscopy.              method for determining erythrocyte zinc
Good results are obtained at relatively low cost          concentration is a direct measurement, after lysis
with this method, which is, however, incapable            and dilution of the erythrocytes with
of a rapid multielement survey. Several atomic            demineralized water (12) or other lysing agents
emission and mass spectrometric techniques                such as Triton X-100 surfactant.(13) Owing to the
have offered some degree of multielement                  inhomogeneity of sample fluids, a measuring
capability, but none has proven sufficiently              error may occur. Gorsucht (14) found that dry-
flexible and robust for the clinical laboratory.          ashing is not the best technique for preparing
                                                          samples for zinc analysis, because the high
Inductively coupled plasma-mass spectrometry              temperatures cause volatilization and residue
(ICPMS) has emerged as a promising and                    problems. When erythrocytes are decomposed by
versatile    means      of    providing     rapid,        use of traditional wet-chemistry techniques,
multielemental profiles of a wide variety of              losses or contamination can easily contribute to
samples. This technique has been applied to               systematic. Only wet-ashing in a closed system,
serum and blood with emphasis on quantitative             with use of a pressure decomposition device,
analysis of selected elements of biological               gave AAS results that agreed with the relative
interest. Such analyses at present require careful        values determined by direct NAA.
attention to matrix matching and spectral
interpretation, and are improved by differential          Applications In Forensic Medicine:
optimization of instrumental settings in selected
mass ranges. However, ICP-MS also has the                 Current means of detection of facts from forensic
capability of rapidly scanning masses across the          specimens rely heavily upon the `experience' of
periodic table.                                           the investigating pathologist, with corroborating
                                                          evidence often absent. This brings in a lot of
AAS in Comparison with NAA (Neutron                       subjectivity to the calculations and analysis of
Activation Analysis) and its adaptation to                forensic specimens. If radioactive isotope tracing
overcome the pitfalls:(10)                                is to be of forensic interest, then it should meet a
                                                          few criteria:
The method most frequently used to determine
zinc concentrations in plasma and erythrocytes is             1.   To have a half-life commensurate with
flame atomic absorption spectrometry (AAS).                        the time scale of investigation that is
However, accuracy comparable with that with                        required (i.e. <40Years);
neutron activation analysis (NAA) can be
achieved with AAS only if sources of error                    2.   To be abundant enough to be detected
peculiar to this method are taken into account.                    easily by conventional analytical
The major disadvantage of conventional AAS is                      techniques and
the need for a relatively large sample volume:
0.5-1 mL of serum or plasma for each                          3.   To have some biological function, so as
determination. An automated micromethod of                         to be incorporated into the human bone.
AAS that obviates this objection has been
available for sometime as an alternative. It is           The nuclides lead-210 (210Pb) and polonium-210
especially advantageous in analysis for trace             (210Po) are radioactive members of the 238U series
metals when the sample volume is limited- e.g.,           and are widely distributed within the
in dialysis patients-because very little of sample        environment. They enter the human body from
suffices. Plasma zinc is determined in a sample           two main sources, direct ingestion in foodstuffs
diluted with an equal volume of demineralized             and the decay of ingested 226Ra which is
water. Because blood plasma is relatively                 retained in the bone and bony tissue.(15) Direct



                                                                                                            5
inhalation of these nuclides is almost negligible,    concentrations in most tissues and body fluids;
although inhalation of a short-lived parent           therefore, their determination in most clinical
isotope (222Rn) can result in elevated                specimens presents a considerable challenge.
concentrations of 210Pb and 210Po in human
tissue.(16)                                           Manganese: Mn is another element for which
                                                      there is a modest amount of documentation of
Consequently, concentrations of 210Pb and 210Po       results. Mn is a component of stainless-steel
have been determined in human bone mainly to          devices, occurs in air dust, and is present in most
evaluate the contribution to internal radiation       plastics. Because natural Mn concentrations in
doses and little investigation has been               human tissues and body fluids are generally low,
undertaken into the potential for using these         efforts to determine this element without clean-
isotopes as detection tools for dating human          room facilities suitable for "ultra" trace-element
skeletal remains. This is despite concentrations of   analysis is a waste of time and resources.
210Pb and 210Po in bone and tissue samples having
been reported from a number of countries.             Nickel: Values of Ni are poorly documented. The
                                                      values reported mainly refer to milk, liver, and
However, to date there remains an incomplete          hair. Nickel has been extensively investigated in
database and no indication that the method is         blood and urine in the context of occupational
applicable to forensic investigations, although its   exposure. According to recent investigations,
possibilities had been previously suggested by        median concentrations of Ni in serum and urine
Swift.(17) Studies have been conducted to             could be as low as 0.2 (range <0.05 to 1.3) and 1.3
evaluate the potential of using 210Pb and 210Po       (range0.3 to 4.6) pg/L, respectively. Because the
nuclides in conjunction with trace elements to        values are on the microgram per liter or per
provide a meaningful estimate of the post-            kilogram level, the risk of contamination is
mortem interval. Any anatomical site can be           serious. More investigations are needed to be
standardized for this purpose. Trabecular bone        able to formulate reference values for Ni in all the
has a large surface area to volume ratio and          clinical specimens in unexposed adults. Values
multiple cavities, which provides ideal               for hair show wider scatter, a clear indicator of
conditions for adherence of soil particles and        analytical problems. According to a recent
heteroionic exchange. It is thus highly susceptible   investigation, the Ni content of hair is about 1.25
to diagenetic changes. Therefore bones with a         ±0.46 mg/kg in healthy control subjects.
higher ratio of trabecular to cortical bone have an
increased risk of diagenesis, for example, ribs       Chromium, manganese, molybdenum, and fluorine.
and calvaria. Cortical tissue from a long bone is     Frequently used analytical methods for this
durable (18,19), hence improves the likelihood of     group of elements are AAS and NAA for Cr and
recovery, and is less vulnerable to heteroionic       Mn, NAA for Mo, and the ion-selective electrode
exchange. Classically long bones, such as the         technique for F. Except for F, the remaining three
femur, are used within analytical studies.(20) For    elements have been determined in a number of
these reasons, samples of diaphyseal compact          tissues and body fluids and show a wide range of
bone ideal for this purpose, with care taken to       concentrations. Cr is high in hair and low in
ensure that the trabecular component is removed       almost all the remaining specimens; Mn and Mo
before analysis of the sections.                      are more concentrated in hair, kidney, and liver
                                                      than in the fluids; and F is high in bone, with
Reference value for concentrations of some            moderate concentrations, 100 pg/kg or less, in
elements have been detailed in a paper by             many other sorts of specimens. This group of
Margaret et al.(21)                                   elements is very difficult to determine in
                                                      biological systems, because of their both low
AAS for Pb; AAS, fluorometry, and NAA for Se;         concentrations and unresolved methodological
and NAA for I are the most frequently used            problems.
analytical techniques. ICP-AES and polarography
have also been successfully used for                  Aluminum: Al is very sensitive to external
determination of Pb. Except for Pb in blood           contamination. Graphite-furnace AAS is the
serum; in most other tissues and body fluids          technique preferred for its determination. Many
these elements are present in concentrations          erroneous results have been published in the
exceeding 10 pg/kg or 10 ug/L. There still are        literature.
some unresolved problems in determining these
elements in some clinical specimens. Generally,       Boron: B is very poorly documented for almost all
these elements occur at pg/kg or pg/L                 human tissues and body fluids. Earlier



                                                                                                        6
investigations in which colorimetry was used         the body’s internal metabolism; therefore, its
suffered from contamination and other                composition reflects the concentration of
methodological problems, and very high values        elements in blood at the time of formation.
were reported. In contrast, a very recent study by
NAA and MS reports31 ±5.6 pg/kg in whole             Hair grows at 1 cm per month. Researchers
blood, 22 ±5 pg/kg in blood serum, and 2.6 ±2        attempting to trace the intake/exposure history
pg/kg in RBC.                                        of trace elements in individuals have analyzed
                                                     the distribution profile of trace elements along
Mercury: Hg is reasonably well documented in         the length of the hair strand. The methods used
several specimens. Because Hg is ubiquitous in       so far to profile elemental concentration along a
the     environment,      precautions     against    single strand of hair include x-ray fluorescence
contamination of the sample are mandatory. The       spectrometry and proton-induced x-ray emission
dietary intake of Hg is reflected in whole blood     spectrometry. Inductively coupled plasma mass
rather than in serum, because Hg readily binds to    spectrometry (ICPMS) spectrometry is another
RBC. Thus, in populations consuming large            potential method for such analyses.
quantities of fish and other sea foods, median
values for RBC may be as high as 16 pg/kg            The U.S. Environmental Protection Agency
(range 9 to 34 pg/kg). Corresponding findings in     provides a concise, well-researched answer to
whole blood median value of 9.5 pg/L (range 1-       this question with the following summary:
59 pg/L). In serum, Hg concentrations may be as
low as 1 pgf/L, depending on the exposure.           The milk, urine, saliva and sweat measure the
Accumulation in hair is one way that Hg is           component that is absorbed but excreted; the blood
eliminated. Also, hair is the main target for        measures the component absorbed and temporarily in
external exposure.                                   circulation before excretion and/or storage; the hair
                                                     nails and teeth are tissues in which trace minerals are
In analysis for trace elements in erythrocytes,      sequestered and/or stored.
sample treatment can represent a substantial
source of error, in addition to that in the          This same study concluded that human hair
sampling process. When the erythrocytes are          could be used effectively for biological
separated from the plasma, adherent (trapped)        monitoring of the highest priority toxic trace
plasma must be taken into account by either:         metals.

                                                     "...Human hair has been selected as one of the
a)Determining it by adding a tracer substance to
                                                     important monitoring materials for worldwide
the blood sample before centrifugation; even so,
                                                     biological monitoring in the Global Environmental
depending on the molecular weight of the tracer,
                                                     Monitoring System (GEMS) of the United Nations
different values are measured or
                                                     Environmental Program."
b)Washing the erythrocytes: It has been shown
                                                     Concentrations of Lead and other heavy metals
that, with triple washing, 99.5% of the trapped
                                                     in the hair provide an accurate and relatively
plasma can be removed without changing the
                                                     permanent record of exposure, and there is a
intra-erythrocyte   concentration;   thus   this
                                                     strong correlation between concentrations in hair
procedure should be used exclusively.
                                                     and concentrations in internal organs. Hair
                                                     analysis appears to be a reliable, simple, and
Analysis in hair: A method called Flow injection-
                                                     atraumatic method of assessing body Zinc stores.
inductively coupled plasma mass spectrometry
                                                     Furthermore, blood is not a suitable material to
has been evaluated for determining the
                                                     analyze for Cadmium, since the metal remains in
distribution profile of trace elements along a
                                                     blood only very briefly and, in consequence, the
single strand of hair. In this method, hair is cut
                                                     levels are always extremely low. Therefore,
into several mm long sections from follicle to the
                                                     studies of Cadmium and Lead in blood would be
distal end. Scalp hair is considered a suitable
                                                     inadequate to demonstrate associated exposure,
biological sample for estimating the intake of,
                                                     while analysis of hair might lead to important
and (or) exposure to, some trace elements, e.g.,
                                                     findings. Hair is better than blood in reflecting
Hg and As; external contamination and failure to
                                                     long-term exposure of Cadmium. Hair analysis
correlate with body burden limit its usefulness
                                                     appears to be a reliable, simple, and atraumatic
for other trace elements. Hair is formed in the
                                                     method of assessing body Zinc stores.
matrix cell, where it incorporates various
elements from the blood at a relatively constant
                                                     The present sample preparation procedure,
rate. After formation, the hair is separated from
                                                     together with introduction of a small sample into



                                                                                                          7
the ICP-MS detector, provides a highly sensitive     environmental sources of lead contamination.
method for determining trace elements (1 ig/g or     However, such is the power and versatility of
less) in small segments of human hair.               modern instrumentation and its accessories that
Nutritionally and toxicologically important trace    it has also dramatically improved our
elements, e.g., Zn, Cu, Hg, and Pb, can be           understanding of other trace metal-related
determined in a hair segment at their normal or      human diseases. The toxic effects of arsenic and
unexposed level. Some toxic trace elements at        hexavalent chromium or the nutritional benefits
lower concentrations, e.g., Ti, can be determined    of iron and selenium would still be relatively
when the segment is from an exposed individual.      unknown if it were not for the continual
                                                     improvements in instrumentation. Although the
Laser Microprobe Mass Analysis                       techniques have been successfully applied to
                                                     many other application areas, there is no
Histochemical staining is well known to be a         question that its use as a biomedical and
useful procedure for localizing trace elements in    environmental research tool has had a direct
tissues. Such methods contribute substantially to    impact on the quality of many people’s lives.
the diagnosis of (e.g.) overload with aluminum,
iron, or lead and associated toxicity.               Acknowldegements:     I   would    like  to
                                                     acknowledge the invaluable help rendered by
The aluminon technique is widely used to             Ms. Anu Joseph, Final year MBBS student of
monitor or follow aluminum in undecalcified          Amrita Institute of Medical Sciences & the
bone sections of dialysin patients with bone         management of Amrita Institute of Medical
disease. In this way, the demonstration of           Sciences, Kochi.
aluminum      at    the    osteoid/calcified-bone
boundary and in histiocytic bone marrow cells in     References
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