Plomo en orina

Determination of Lead in Urine by
GFAAS–Deuterium and Zeeman
Background Correction
Application Note
Atomic Absorption

Authors

Introduction

Christine Flajnik

A growing number of children in the U.S. are testing positive for lead poisoning.
The Centers for Disease Control (CDC), Atlanta, GA, have set specific guidelines for
corrective action for various levels. Children with bloodlead levels > 24 µg/dL who
show symptoms of lead poisoning are treated with chelation therapy. There are
many chelating agents commercially available today. The basic mechanism is the
same for all of them – to form a stable lead compound which is then excreted in the
urine. The urine is collected and analyzed for lead [1].

Doug Shrader

This study deals with the determination of lead inurine. The method is based on
the work of Dr. Patrick J. Parsons, New York State Department of Health, Albany,
NY[2]. Initially the procedure was created for the measurement of lead in blood,
however, it is found to work extremely well for urine as well. The method permits
these biological samples to be run against aqueous calibration standards.
Both Zeeman and Deuterium background correctionwas used. Methods include
graphite furnace programs for platform atomization (forked platform tube) and wall
atomization (partition tube).

Experimental

Standards Required

Instrumentation

1000 µg/mL stock lead solution (Pb) - atomic absorption
standards can be purchased from any major chemical supplier.

The instrumentation used for the determination of lead in
urine was anAgilent SpectrAA-400Z with Zeeman background correction and an Agilent SpectrAA-400P with
deuterium background correction. Each spectrometer was
equipped with a Agilent GTA-96 graphite tube atomizer and
PSD-96 programmable sample dispenser. Ultra high purity
argon was used as the inert gas.

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Reagents Required

10 µg/mL intermediate Pb standard – Pipet 1.0 mL stock
Pb standard and2.0 mL conc. HNO3 into ~75 mL D.I.
water in a 100 mL volumetric flask. Carefully make up to
volume (100 mL).
Calibration Standards – All prepared weekly in 2% v/v
HNO3. Final volumes are 100 mL, made in volumetric
flasks utilizing glass pipettes.
100 µg/L – Pipet 1.0 mL intermediate standard and
dilute to 100 mL with 2% v/v HNO3.

Triton X-100
Ammonium diHydrogen Phosphate (NH4H2PO4), agrade
suitable for trace metal analysis.

200 µg/L – Pipet 2.0 mL intermediate standard and
dilute to 100 mL with 2% v/v HNO3.

Concentrated Nitric Acid (HNO3), a grade suitable for trace
metal analysis.

300 µg/L – Pipet 3.0 mL intermediate standard and
dilute to 100 mL with 2% v/v HNO3.

Reagent Preparation

400 µg/L – Pipet 4.0 mL intermediate standard and
dilute to 100 mL with 2%v/v HNO3.

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10% Triton X-100 (v/v) – Pipet 10 mL of Triton X-100 into
~ 70 mL D.I. water. Stir for ~1 hour. The solution may
need to be gently warmed or sonicated for complete
dissolution. Make up to 100 mL. (Stable for 1 month.)

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Urine Samples

20% NH4H2PO4 (w/v) – Dissolve 20 g of NH4H2PO4
in ~ 75 mL D.I. water. Make up to 100 mL. (Stable for
6 months.)

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600 µg/L –Pipet 6.0 mL intermediate standard and
dilute to 100 mL with 2% v/v HNO3.

Working Modifier – To ~ 400 mL D.I. water add 25 mL
10% Triton X-100 solution, 5.0 mL 20% NH4H2PO4 solution
and 1.0 mL conc. HNO3. Make up to 500 mL. (Stable for
3 weeks.)

Urine controls were purchased to be used as urine samples.
Controls were prepared per included instructions. The urine
was obtained from New YorkState Department of Health,
Wadsworth Center Lead Poisoning Laboratory, Empire State
Plaza, Albany, NY 12201-0509.

Working Standard and Sample Preparation
All calibration working standards and urine controls were prepared in the same manner. They should be prepared fresh
daily. A glass 1.0 mL pipette (graduated in 100 µL increments)
was used to add 900 µL of the working modifier to a...