title: Novel spot tests for detecting the presence of zinc sulfate in urine, a newly introduced urinary adulterant to invalidate drugs of abuse testing.
abstract: OBJECTIVE
  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.
authors.affiliation: 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.
authors.forename: Kerry J
authors.initials: KJ
authors.lastname: Welsh
authors.forename: Jennifer E
authors.initials: JE
authors.lastname: Dierksen
authors.forename: Jeffrey K
authors.initials: JK
authors.lastname: Actor
authors.forename: Amitava
authors.initials: A
authors.lastname: Dasgupta
mesh_terms: D016477:Artifacts; D002241:Carbohydrates / Q000737:chemistry; D019411:Clinical Laboratory Techniques / Q000379:methods*; D004340:Drug Contamination; D005188:False Negative Reactions; D005189:False Positive Reactions; D006801:Humans; D019163:Reducing Agents / Q000737:chemistry; D015813:Substance Abuse Detection / Q000379:methods*; D016482:Urinalysis / Q000379:methods*; D019287:Zinc Sulfate / Q000032:analysis / Q000652:urine*
chemical_list: D002241:Carbohydrates; D019163:Reducing Agents; D019287:Zinc Sulfate
keywords: Adulterated urine; False negative; Spot test; Zinc sulfate