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Am J Clin Pathol. 2013 Oct;140(4):572-8. doi: 10.1309/AJCP2FJ9VBPXJYTQ.

Novel spot tests for detecting the presence of zinc sulfate in urine, a newly introduced urinary adulterant to invalidate drugs of abuse testing.

Author information

1
Dept of Pathology and Laboratory Medicine, University of Texas-Houston Medical School, 6431 Fannin, MSB 2.292, Houston, TX 77030; e-mail: amitava.dasgupta@uth.tmc.edu.

Abstract

OBJECTIVES:

To find a suitable method for detecting zinc sulfate in adulterated urine.

METHODS:

Two rapid spot tests to detect the presence of zinc sulfate in urine were developed.

RESULTS:

Addition of 3 to 4 drops of 1N sodium hydroxide solution to approximately 1 mL of urine containing zinc sulfate led to the formation of a white precipitate, which was soluble in excess sodium hydroxide. In the second spot test, addition of 3 to 4 drops of 1% sodium chromate solution to 1 mL of urine containing zinc sulfate followed by the addition of 4 to 5 drops of 1N sodium hydroxide led to formation of a yellow precipitate (zinc chromate). Detection limit of these visual spot tests was 10 mg/mL of zinc sulfate in urine. Twenty drug-free urine specimens and urine containing high amounts of sugar or reducing substances were tested with no false-positive spot test results observed. However, if lead is present in high amounts in urine, it may cause false-positive spot test results. When aliquots of urine controls for drugs of abuse testing were supplemented with different amounts of zinc sulfate, false-negative drug test results were observed except for amphetamine. Zinc sulfate also falsely reduced measured urine alcohol level in urine.

CONCLUSIONS:

Zinc sulfate can invalidate urine drug and alcohol testing but can be detected using the novel spot tests developed.

KEYWORDS:

Adulterated urine; False negative; Spot test; Zinc sulfate

PMID:
24045556
DOI:
10.1309/AJCP2FJ9VBPXJYTQ
[Indexed for MEDLINE]
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