Related Experiment Video
Updated: Jul 25, 2025

High-throughput and Comprehensive Drug Surveillance Using Multisegment Injection-Capillary Electrophoresis-Mass Spectrometry
Published on: April 23, 2019
Comparison of different methods used in drugs of abuse for sample validity testing including pH methods, specific
Ashraf Mina1,2, John Stathopoulos1, Taveet Sinanian1
1NSW Health Pathology, Forensic & Analytical Science Service (FASS), Toxicology Unit, Macquarie Hospital, Sydney, NSW, Australia.
Objectives:
In the absence of sample validity testing, a healthcare provider may fail to identify a patient's adulteration of their urine sample. This study compared different methods for specific gravity (SG), pH, TECO™ Drug Adulteration Test Strip (dipstick) and oxidant assay to explain the differences and also make an informative decision on method selection.
Methods:
Creatinine, SG and pH measurements are essential in sample validity testing. SG and pH automated chemical methods are compared against pH meter method, SG refractometer and dipstick method. Also, oxidant assay was compared against dipstick method.
Results:
SG chemical method agreement with refractometer is 81.9% and with dipstick method is 64.7%. The refractometer method agreement with dipstick method is 66.1%. pH chemical method agreement with pH Meter method is 74.3% and with dipstick method is 81.4%. pH meter method agreement is 85.7% with dipstick method. Results were analysed using Deming regression analysis and F-test. SG chemical method correlated better with refractometer than the dipstick method. Oxidant assay correlated well with dipstick method in detecting adulterants such as pyridinium chlorochromate, nitrite and bleach.
Conclusions:
Varying degrees of differences were seen in the SG and pH measurements. These differences were both method and instrument dependent. The automated chemical methods are recommended alongside oxidant assay for consistency, accuracy and faster turn-around time as part of sample validity testing for drugs of abuse.
Related Concept Videos
Data Validation
Key parameters for method validation include:
Drug Concentrations: Measurements
Plasma...
Sampling Methods: Sample Types
Solid samples include a variety of substances, such as sediments from water bodies, soil, metals, and biological tissues. Two standard methods for extracting sediments from water bodies are grab sampling and piston coring. Grab sampling involves using a device to collect a discrete sediment sample from the bottom of a water body with minimal disturbance. Grab samples do not always represent the entire area due to...
Sampling Methods: Overview
In analytical chemistry, the choice of...
Reliability and Validity

