Application
Note: 40835
The Analysis of Clinical Samples by Atomic
Absorption Spectrometry
Key Words
• Atomic
Absorption
• Blood
• Clinical
• Graphite Furnace
• Urine
Introduction
Clinical analysis represents a very important Atomic
Absorption applications segment that shares some
similarities with environmental analysis. The majority of
samples analyzed are taken from the main group of
biological fluids, such as whole blood, plasma, serum and
urine. To a lesser extent, hard and soft tissues, such as
bone, fingernails and hair, may also be used for specific
(mainly toxicity) purposes. Nutritional studies involving
diet mean that faeces may also be analyzed on occasions.
The whole range of atomic absorption techniques can
be employed - flame based analysis for the major and
minor essential elements, graphite furnace analysis for the
trace elements and vapor analysis for the group of toxic,
mostly hydride-forming, elements. Sample preparation
techniques are often important, especially where the
graphite furnace is to be used. The high background levels
of the alkali metals means that high background correction
efficiency may be required for furnace analyses, together
with the ability to use platform cuvettes and matrix
modification procedures. Clinical analysis often uses
screening techniques to speed up throughput. Rapid
methods using STAT flame analysis, for example, can be
used to screen out those samples containing normal levels
of elements, leaving the abnormal samples to be measured
by the longer full analysis procedures.
1) Whole blood and serum:
Blood is a highly specialized tissue consisting of several
types of cell suspended in a fluid medium containing a
variety of dissolved substances that are transported from
one part of the body to another. The cellular components
consist of red blood cells, which carry respiratory gases,
white blood cells, which fight disease, and platelets, which
play an important role in the clotting of blood. Blood
serum is prepared from whole blood by centrifugation,
which separates the fluid from the cellular material. Serum
contains many compounds including water, proteins,
glucose, lipids, amino acids, salts, enzymes, hormones,
antigens, antibodies and urea. Many metallic elements can
combine with these compounds. Blood plasma is separated
from whole blood by allowing the blood to clot naturally,
then separating the fluid from the clot. It is mainly water
and inorganic salts, with traces of organic material remaining.
2) Urine:
Urine is a pale yellow, slightly acidic fluid excreted by the
kidneys and it contains waste products removed from the
blood. Urine composition is studied to understand the
metabolic processes by the identification and quantification
of end products formed and excreted in the urine. You can
also obtain evidence that may be useful in the diagnosis
and treatment of pathological states by the identification
of abnormal substances or substances in abnormal amounts
in the urine.
3) Analytes:
The metallic elements measured in clinical analyses fall
into three groups according to their role in human
metabolism, and they are usually classed as essential, toxic
or therapeutic.
Essential elements
• Essential major elements:
Ca, Mg, Na, K
• Essential minor elements:
Zn, Cu, Fe
• Essential trace elements:
Cr, Mn, Mo, Co, V, Se, Ni
Essential elements fall into three sub groups of major,
minor and trace elements, (shown above) depending on
their normal concentration levels in the samples. The
elements within each sub group are as follows.
Major Essential Elements
Sodium
Sodium is the major cation of extra-cellular fluids.
Approximately two-thirds of the 70 g contained in the
average adult body is found in these fluids; most of the
remainder is in the bone and only a small fraction is
located within the cells. Present in the form of a chloride,
sodium participates in many vital physiological functions.
It is associated with pH control of body fluids, regulation
of acid-base reactions, and adjustment of body fluid
volume. Sodium can be found in all body tissues and its
determination is one of the most frequently performed
clinical procedures. Serum level of sodium is relatively
constant and extreme fluctuations are used in diagnosis.
Low serum sodium levels are found in a variety of conditions,
including severe polyuria, metabolic acidosis, Addison's
disease, diarrhoea and renal tubular disease. Increased
serum sodium levels are found in hyperadrenalism
(Cushing's syndrome), severe dehydration due to primary
water loss, certain types of brain injury, diabetic coma
after therapy with insulin and excessive treatment with
sodium salts. The range of normal values for serum sodium
are 135-148 mmol/L.
Potassium
Calcium
Calcium is an essential mineral element comprising up to
2 % of the human body weight. Bones contain about 1 kg
in the typical human male but only 1 % of the total
calcium content is physiologically active in body fluids.
The calcium ion decreases neuromuscular excitability,
participates in blood coagulation, activates enzymes and
plays an important role in the transfer of inorganic ions
across cell membranes. Essentially all the calcium in blood
is present in the serum and normal adult serum levels of
calcium are in the ranges 2.23-2.60 mmol/L.
Magnesium
Magnesium ions serve as activators for a number of
important enzyme systems engaged in transfer and hydrolysis
of phosphate groups. Diagnosis of 'magnesium deficiency
tetany' is the most important clinical application in serum,
but decreased magnesium levels can be found in cases of
the malabsorption syndrome, acute pancreatitis, hypoparathyroidism, chronic alcoholism and delirium tremens,
aldosteronism, digitalis intoxication, after protracted I.V.
feeding and after excessive loss of magnesium in the urine.
Increased serum magnesium levels have been observed in
dehydration, severe diabetic acidosis and Addison's disease.
Any condition interfering with glomerular filtration results
in retention of magnesium, and thus elevation of serum
magnesium levels. Normal adult levels are in the range
0.75-1.25 mmol/L.
Potassium is the chief intra-cellular cation found in the
human body. Levels in the extra-cellular and intra-cellular
fluid are maintained by an active transport mechanism.
Low potassium levels can cause excitatory changes in
muscle irritability and myocardial function, which are
accompanied by characteristic electro-cardiographic changes.
Deficiencies of the potassium ion may occur as a result of
excessive loss of potassium through prolonged diarrhoea
or vomiting. Increased potassium serum levels may be
observed in cases of oliguria, anuria, or urinary obstruction.
Normal serum potassium levels range from 3.5-5.3 mmol/L.
Flame Atomic Absorption Spectrometry (FAAS) is an
ideal analytical technique for measuring both major and
minor essential elements. FAAS has been used for many
years for routine testing of essential elements as it is a
quick, simple and accurate technique, which rarely suffers
from interference. It can determine most metallic elements
at concentrations of low mg/L and even µg/L for some
elements. Newer instrumentation can provide enhanced
analytical capabilities and increase productivity with complete
automation including quality control checking. It is usual
to measure major and minor essential elements in serum
by flame atomic absorption spectrometry. It is not practicable
to aspirate undiluted serum directly into an atomic absorption
instrument due to the viscosity of serum, and a dilution
factor of at least 1:10 is normally recommended to avoid
blockage problems with the nebulizer and/or burner slot.
Iron
Figure 1: Thermo Scientific iCE 3300 AA Spectrometer suitable for the flame
analysis of major essential elements
Minor Essential Elements
Iron was one of the first of the minor elements to be
recognised as being necessary for both plants and animals.
An average adult male is estimated to contain 4 - 5 g of
iron. Most of the iron exists in complex forms bound to
protein either as haeme or porphyrin compounds, especially
haemoglobin or myoglobin. Iron in blood is found combined
with haemoglobin in the erythrocytes and as transferrin in
the plasma in the ratio of approximately 100 to 1.
Decreases in serum iron levels are generally due to a
deficiency in the total amount of iron present in the body,
which may be caused by a lack of sufficient intake or
absorption of iron. Low values of serum iron are encountered
in hemorragic and hypochromic types of anaemia, in acute
and chronic disease, pregnancy, and iron deficiency states.
High values of serum iron are observed in hemochromatosis,
in forms of anaemia characterized by diminished haemoglobin
formation and often in hepatitis. Normal serum iron levels
for adult males are in the range 9.5 - 23 mmol/L (0.60 1.50 mg/L), while for adult females the range is 8 - 20 mmol/L
(0.50 - 1.30 mg/L). Serum iron levels decrease in the elderly
to 6.2 - 12.5 mmol/L (0.40 - 0.80 mg/L).
Zinc
Zinc is essential for the growth and propagation of cell
cultures and for the functioning of several enzymes. It
constitutes about 0.003 % of the normal human body.
Zinc is present in serum, plasma, erythrocytes and leucocytes.
It exists in the plasma both as loosely bound and firmly
bound fractions associated with serum albumins and
globulins. Zinc levels are an important indication of various
pathological conditions. The normal values of zinc in
serum are in the range of 11 - 24 mmol/L (0.7 - 1.60 mg/L).
There is little variation with gender or age but there is a
diurnal variation with peak concentration occurring about
10.00 am.
Copper
Copper is an extremely widespread minor element and can
be found in almost all forms of life. A deficiency in copper
results in severe derangements in growth and metabolism.
The most significant clinical application of copper
determination is in its diagnosis of hepatolenticular
degeneration (Wilson's disease), in which the total serum
copper level is significantly reduced. High blood copper
levels occur in most chronic and acute infections, and in
leukaemia, Hodgkin's disease, various anaemias,
hemochromatosis, rheumatoid arthritis, pregnancy,
cirrhosis, and myocardial infarction. Normal levels in
serum vary with age and sex. Newborn children are in the
range 3 - 11 mmol/L (0.2 - 0.7 mg/L), children over 6 months
and adults 11 - 20 mmol/L (0.7 - 1.3 mg/L). Adult males
are in the range 11 - 20 mmol/L (0.7 - 1.3 mg/L) whereas
females are slightly higher, in the range 12.5 - 24 mmol/L
(0.80-1.55 mg/L). In pregnancy, from 16 weeks to full
term, the female values are elevated to 27 - 40 mmol/L
(1.7 - 2.5 mg/L).
Figure 2: STAT Accessory,which may be used for measuring minor essential
elements
The minor essential elements are present at a
concentration that is at the lower end of the normal flame
range. They can be determined using the STAT accessory
(see Figure 2) or by the graphite furnace technique.
Trace Essential Elements
Chromium
possible partial paralysis. The concentrations of selenium
in whole blood reported as normal vary from 50 to 350 mg/L
and are dependent on several dietary factors.
Chromium is considered to be an essential element, but is
also known to be toxic when present at elevated
concentrations. The metal has been shown to be biologically
active in trace amounts, and the chromium-containing
molecule known as the 'glucose tolerance factor' is
thought to be an insulin co-factor, and hence has been
implicated in glucose metabolism. The analysis of blood
chromium is used as a reflection of long term exposure,
whereas urinary chromium better reflects recent uptake.
Normal concentrations of chromium in human whole
blood are in the range of 0.5-5.0 mg/L.
Manganese
Manganese is recognized as an element that is essential to
human nutrition. It influences normal growth, and serves
an important role in activation of an enzyme (arginase)
necessary to the formation of urea. High levels of manganese
are considered to be toxic. Symptoms observed in cases of
manganese poisoning include psychomotor instability and
hallucinations. The rigidity and movements of the limbs
are akin to those of Parkinsonism and also suggest a
similarity to Wilson's disease.
Figure 3: Thermo Scientific iCE 3500 AA Spectrometer enables both flame
and graphite furnace analysis to be carried out with automated software
changeover
Molybdenum
Nickel
The importance of molybdenum as an essential element
has long been established. The molybdenum ion catalyses
xanthine and aldehyde oxidase activity. Molybdenum
deficiency in man has not been recognized, but instances
of both toxicity and deficiency in animals are widely
reported.
Nickel is considered an essential trace element. The
concentration in soft tissue is relatively low, although
higher levels are found in the skeleton. It is also reported
to be present in RNA and DNA. Nickel deficiency can
affect the reproductive process and decrease the 'in vitro'
liver oxidation of glycerophosphate.
Cobalt
Toxic elements
Toxic elements are often defined as those that interfere
with metabolic processes. The elements usually included in
this group are as follows: Lead, Mercury, Arsenic, Thallium,
Cadmium, Aluminium, Boron, Antimony.
Cobalt is recognized as an essential trace element. Cobalt
is required in the body for vitamin B12 synthesis. Other
important functions of this metal involve the activation of
certain enzymes and the formation of haemoglobin. High
levels of cobalt induce nausea and vomiting due to the
local irritation of the gastric mucosa.
Lead
The normal adult has 10 - 25 mg of vanadium mainly in
teeth, bones and fat. Most of the ingested vanadium is
rapidly excreted in urine; the remainder is retained in the
liver and bones. Vanadium is believed to inhibit cholesterol
levels 'in vitro'. Vanadium deficiency is reported to cause
retarded bone development and impaired reproductive
performance.
Lead is a poisonous element, which tends to accumulate in
the tissues and bones of exposed individuals. It can be
absorbed by inhalation from air or by ingestion of solids
or liquids. Most of the lead is excreted in the kidneys, but
the process of elimination is much slower than the rate at
which it is absorbed. Prolonged exposure to lead may result
in anorexia, leadline on gum margin, nausea, severe
abdominal pain, paralysis, mental confusion, anaemia,
convulsions and brain damage.
Selenium
Mercury
Selenium was first recognized as an essential element in
human metabolism in the 1950's. Deficiencies of selenium
are associated with heart disease, muscular dystrophy and
reproductive disorders, and the element is an essential
component of the mammalian enzyme glutathione peroxidase.
As with many essential elements selenium is also known
to be toxic when present at higher concentrations. Symptoms
of selenium poisoning include abdominal pain and
Mercury is an environmental contaminant, which has
severe toxic implications. Mercury compounds and especially
organic mercury compounds, even in low concentrations,
are capable of inactivating sulfhydryl bonds and thus
interfering with cell function. Alkyel mercury compounds
may cause irreversible damage to the central nervous
system while inorganic mercury compounds cause reversible
damage to tissues such as kidneys and intestines.
Vanadium
Arsenic
The toxicity of arsenic is well known historically. Arsenic
combines readily with proteins due to its great affinity for
sulfhydryl groups. This results in the precipitation of proteins,
producing gastro-intestinal irritation and irreversible inhibition
of important enzyme systems, which are important toxic
effects of arsenic. The great affinity of arsenic for tissue
proteins is also responsible for the rapid removal of arsenic
from the blood. Blood, therefore, is not a good specimen,
except in cases in which a large overdose of this substance
has been ingested.
Therapeutic elements
Therapeutic elements are used to treat certain diseases,
and their levels in patients undergoing the treatment are
monitored to control the dosage and progress of the
treatment.
Gold
Gold complexes are used in the treatment of rheumatoid
arthritis and certain other collagen diseases. Radioactive
gold has application in treatment of cancer and charged
gold leaf has been utilised for neurosurgical procedures as
a device for closure of the fragile pia mater.
Thallium
Thallium toxicity has been a frequent worldwide occurrence
in man and domestic animals. Thallium salts were used as
rodenticides and also, both internally and externally, as a
depilatory. The characteristic feature of thallium poisoning
is loss of hair or occasionally, loss of nails and the skin of
the feet. Since this metal is not present in biological material,
any amount demonstrated in urine is significant.
Cadmium
Cadmium is an extremely toxic element. Acute exposure
to cadmium leads most commonly to pulmonary oedema.
Prolonged exposure may lead to emphysema, proteinuria,
and anosmia. Another problem associated with cadmium
is its tendency to replace zinc in the body. This can be
serious since zinc serves a vital role in the function of
many enzymes.
Aluminium
The determination of aluminium in biological fluids has
been the subject of many publications. Most of the
attention has been given to the analysis of serum, since
serum levels can be used for the diagnosis and monitoring
of dialysis patients at risk of aluminium intoxication. In
patients with renal failure treated by means of dialysis, it
is well established that besides the ingestion of aluminium
containing phosphate binders, aluminium contaminated
water and dialysis fluids can cause aluminium toxicity.
Boron
The main cause of human intoxication with boric acid,
except for oral ingestion, is resorption through injured or
burned skin and mucous membranes. The majority of
ingested or resorbed boron is eliminated through the kidneys,
however, in cases of boron intoxication it can be detected
in blood, spinal fluid, fractions of peritoneal dialysate, brain,
liver, spleen and heart tissues.
Antimony
Antimony and its compounds are extremely toxic. Physical
contact, fumes or dust are known to cause dermatitis,
keratitis, conjunctivitis and nasal septal ulceration. The
volatile hydride derivative of antimony, stibine, is very
dangerous and can be responsible for haemolysis and
abdominal pains.
Platinum
Platinum salts, especially cisplatin
(cisdiamminedichloroplatinium (II)), is a potent anticancer
agent with substantial clinical activity against testicular
cancer, ovarian cancer, head and neck malignancies, and
other tumours. Cisplatin's antitumour effect is mediated
through its binding to DNA to form a number of different
molecular species and total platinum binding to DNA is
directly related to tumour cell kill.
Lithium
Lithium is widely used in the control of the manic stage of
depressive psychosis. Therapeutic levels during the initial
treatment are 1.0-1.5 mmol/L of serum, until the threshold
of the effectiveness is reached after 6-10 days. The serum
level during maintenance therapy is generally kept at 0.51.0 mmol/L. Increased lithium levels are toxic, although
toxic reactions are rarely seen with serum levels below
1.5 mmol/L. However, they become progressively more
severe as the levels increase above 2.0 mmol/L. It is therefore
mandatory to regularly monitor serum lithium levels of
patients undergoing this treatment.
Graphite Furnace Atomic Absorption Spectrometry
(GFAAS) is an ideal technique to measure all trace essential
elements. Although GFAAS is a slower and more complicated
technique than FAAS, it has the distinct advantage of
analyzing trace elements at low µg/L and even ng/L for
some elements. Another benefit of this technique is that
only small sample volumes, of the order of 50-100 µL, are
required. Background (non specific) absorption of the
atomic radiation by the sample matrix components can
cause large errors, but these can usually be corrected
instrumentally, using one or other of the two complementary
forms of background correction available, QuadLine
(continuum source) or Zeeman effect. Automation of this
technique is readily available and is beneficial due to
improved measurement and precision. This technique is
ideal for the analysis of all trace elements except mercury,
for which the sensitivity is poor because of the high volatility
of the element. The most frequently used analyses involve
one or more of the following procedures:
(i) Direct injection into the graphite tube or platform.
(ii) Dilution with water, Triton X-100 or dilute acids.
(iii) Deproteinisation with stronger acid.
(iv) Use of matrix modification.
It is rarely necessary to completely digest the sample,
unless it is a soft tissue or bone. Chelation/extraction
techniques previously used to concentrate the analyte and
remove interfering matrix components are seldom required
with modern instruments due to their improved performance.
Hydride generation AAS is an attractive technique for
the hydride forming elements, as the capital cost of the
equipment is much less than GFAAS, yet the sensitivities
are similar. However, sample digestion is more likely to be
required, and precautions have to be taken to ensure that
oxidation state interferences are eliminated.
4) Sampling:
There are a number of well-defined sampling technologies
used for clinical situations.
Blood Samples
Gel separation systems - Release zinc and other elements.
Septum type stoppers/caps - Can also cause lead contamination.
To minimize contamination it is best to collect blood
in a plain plastic tube and forward the serum. For certain
assays, particularly aluminium, polycarbonate tubes are
preferred. The separation of serum or plasma from red
cells is best done using a clear polythene Pasteur pipette
with integral bulb. Glass Pasteur pipettes with rubber teats
should never be used because talc or dust inside the teat
contains zinc, which can be blown into the pipette during
separation thus causing contamination. Release of aluminium
from the glass of the pipette can also invalidate assays for
this element. Aluminium is so ubiquitous that it is best to
send the sample unseparated. For those assays requiring a
whole blood specimen, potassium EDTA is the preferred
anticoagulant, although some batches may contain significant
amounts of manganese and cobalt, as already noted. In
order to detect possible contamination, it is generally
advisable to send an empty tube with each specimen or
batch of specimens forwarded to the laboratory.
Urine Samples
The skin surface is usually cleaned with a disposable alcohol
swab before any blood sample is taken. This precaution is
particularly necessary in the industrial environment and
where a specimen is being taken for analysis of an element
such as aluminium, which is subject to a major contamination
problem. Capillary blood sampling is best avoided, as it is
more subject to contamination. In general, it is normal to
collect a venous blood sample through a standard metal
disposable needle but for certain analyses, such as manganese,
chromium, and nickel, contamination may arise from this
procedure. For these elements the blood should be taken
through a plastic cannula and the initial 5 mL discarded
or reserved for non-trace element analysis. For each element
a specific type of container and anticoagulant is recommended.
For some trace elements these are significant sources of
contamination and selection of the wrong type can completely
invalidate the assay. Some examples are listed below:
Heparin - May contain zinc, copper and manganese
accumulated during chemical separation and purification.
Potassium EDTA - Leaches zinc from erythrocytes into plasma.
May contain significant amounts of manganese and cobalt.
Rubber stoppers/caps - Release significant amounts of zinc.
Orange plastic stoppers/caps - Release cadmium.
In general, 24 hour urine samples are collected. The collection
is made into a container that has been thoroughly washed
with dilute nitric acid (M or 2M) followed by thorough
rinsing with de-ionized water. Any 'black rubber' cap seals
should be removed prior to washing and use. Polythene
containers are not suitable for urine mercury collections
and polycarbonate containers should be used. A sterile
'Universal' tube containing 20 ml of the collection is
normally forwarded to the laboratory for analysis.
Other Samples
Biopsy and larger samples of tissue are sectioned with a
clean stainless steel scalpel or needle, placed into a dry
polycarbonate tube and stored at -20 °C until used.
Tissues are not stored in formalin as this can cause gross
contamination and also leach substantial amounts of
cadmium and other elements from the tissue. All specimens
that contain, or are suspected to contain, organisms, viruses
or substances such as hepatitis B or HIV which are liable
to pose a serious infection hazard to laboratory personnel
must be clearly identified.
5) Sample preparation:
One of the distinct advantages of atomic absorption
spectrometry in the analysis of clinical samples is that in
most cases very little, or no, sample preparation is required.
If sample preparation is required it should involve a minimum
of handling and as few reagents as possible. It is essential
that all reagents used are of the highest grade available.
The difference between 'normal' and 'pathological' levels
in biological samples can be quite small; therefore, the danger
of contamination must always be borne in mind. It should
be remembered that the first requirement for accurate
results is cleanliness. Care should be exercised, at all stages,
to avoid contamination. The cleaning of all laboratory ware
is of prime importance. After use, all glassware should be
washed using a phosphate free surfactant detergent, such
as Decon 90, and left soaking in 10 % v/v nitric acid until
required.
6) Units of measurement:
In the typical clinical chemistry laboratory a variety of units
are used but the majority of hospital laboratories use the
SI molar unit system as the prime unit of reporting.
However, for non-clinical users mass units per liter are
also quoted. The appropriate relationships are shown
below for commonly encountered units.
1 µg/mL = 1 mg/L = 1 part per million (ppm)
1 ng/mL = 1 µg/L = 1 part per billion (ppb)
Concentrations of trace elements in urine may be
reported per volume, per 24 hour urinary output or per
mmol of creatinine or per gram of creatinine. Tissue sample
concentrations may be reported as mg or µg per gram or
kilogram of wet weight, dry weight or ash weight.
7) Typical results:
The following section contains a number of examples of
clinical analyses using the various techniques. Appendices
1 and 2 list the reference values for the elements.
(a) Simple flame analysis of major elements - using a
simple dilution by appropriate factor and addition of
La+ as a buffer for Ca and Mg determinations or
excess Na+ as an ionization buffer for K measurements.
Element
Ca
Na
Results mM/L
Measured
Certified
2.27
2.27
1.6
3.15
3.12
2.3
2.22
2.32
2.25
1.6
3.2
3.17
2.3
2.27
1.72
148
148
151
151
139
139
131
131
1.67
147
147
150
151
138
137
133
132
Element
Mg
K
Results mM/L
Certified
Measured
0.86
0.95
0.96
0.87
0.65
0.25
0.74
0.82
0.9
0.98
0.85
0.64
0.3
0.76
0.9
2.8
3.9
3.9
2.6
5.7
6
2.5
5.1
0.95
2.6
4
3.9
2.4
5.7
6.1
2.4
5
(b) Flame analysis using the STAT accessory for rapid
screening of minor elements - uses a simple 1 + 20
dilution with deionized water. Sample size may be
minimized by using aliquot microsampling.
Sample
QC Scheme Results
Mean
SD
µmol/L
µmol/L
QC1
QC2
QC3
QC4
QC5
QC6
QC7
QC8
QC9
QC10
QC11
QC12
35.5
39
35.5
22.5
18.7
37.2
30
23.5
32
45
40.5
27.8
34.7
38.3
34.5
22.9
16.9
37.7
26.6
22.6
31.9
42.4
36
26.6
Precipath
Precinorm
19.9
21.1
20.5
20.8
2.47
3.25
2.35
1.98
1.71
4.02
2.55
2.96
3.63
2.91
2.33
1.7
Table 3: Analysis of a number of QC sera for the minor element Cu using
flame AAS and the STAT accessory
(c) Graphite furnace analysis using the GF95Z Zeeman
furnace for Pb determination. 100 mL portions of
whole blood are mixed with 900 mL of matrix
modifier (which contains 0.1 % v/v HNO3, 0.2 % m/v
ammonium dihydrogen phosphate and 0.5 % m/v
Triton X-100.
Reference Material
Certified Value (µg/L)
Measured Value (µg/L)
NIST SRM 955a-1
NIST SRM 955a-2
NIST SRM 955a-3
NIST SRM 933a-4
5.01± 0.09
13.53 ± 0.13
30.63 ± 0.32
54.43 ± 0.38
5.02 ± 0.33
13.43 ± 0.74
30.33 ± 0.72
54.58 ± 1.57
Table 4: Analysis of a number of certified reference sera for the trace
element Pb using a Zeeman furnace system
(d) Vapour analysis using the VP100 hydride accessory in the example below the sample is acid-digested,
treated with concentrated HCl to reduce Se (IV) to Se
(III) and determined using 0.1 % m/v sodium borohydride.
Sample
Table 2: Analysis of a number of QC sera for the major elements Ca, Mg,
Naand K using flame AAS
STAT - FAAS
µmol/L
Serum 1
Serum 2
Se Reference Value (µmol/L)
Se Measured Value (µmol/L)
1.1 ± 10 %
0.5 ± 10 %
1.02
0.52
Table 5: Analysis of two certified reference sera for the trace element Se
using a VP100 hydride system
In addition to these
offices, Thermo Fisher
Scientific maintains
a network of representative organizations
throughout the world.
The VP100 Vapor/Hydride generation Accessory
8) Conclusions:
Atomic Absorption is a technique that is ideally suited to
the analysis of clinical samples. Using the range of
accessories, (flame, furnace and vapor) it is possible to
analyze major, minor and trace level concentrations of all
the clinically significant elements in a wide range of
sample types. Modern AAS systems have the detection
power and are easy to use, with Wizard-driven software
to guide the user through method setup and analysis with
the minimum of effort.
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