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New Kit, Calibrator and Controls for Clinical Mass Spectrometry

Alcohol is one of the most frequently consumed drugs that is quickly absorbed in the small intestine of the human body. It is metabolised in the liver to acetaldehyde and then to acetic acid. The elimination is very rapid, subsequently, the detection time is limited to < 12 hours. Typically, less than 0.1 % of the consumed ethanol is present as the glucurono- or sulfo conjugated configuration, which is excreted as ethyl glucuronide (EtG) and ethyl sulfate (EtS), both detectable for a sustained period in comparison to ethanol. Thus, EtG and EtS close the gap between short-term markers (i.e. ethanol itself) and long-term markers such as CDT.

The MassChrom® kit from Chromsystems allows the reliable determination of EtG and EtS from urine with robustness and precision. The assay is validated according to the guidelines of the GTFCh (Society of Toxicological and Forensic Chemistry) for quality assurance and enables the determination of both parameters with one sample preparation and one single injection with an analysis time of 6 minutes. The straightforward and efficient sample preparation consists of a single pipetting step that includes the instrument-specific dilution. The human-matrix based 6PLUS1® Multilevel Calibrator Set and MassCheck® controls ensure precision and accuracy of results.

Chromatogram

Specifications

Limit of quantification: EtG 35 µg/l
EtS 20 µg/l
Recovery EtG 97-100 %
EtS 95-98 %
Intraassay: Vk < 3 %
Interassay:
Vk < 4 %
Analysis time: 6 min

LC-MS/MS-Parameter

Injection volume up to 20 µl
Ionisation ESI negative
MS/MS-Mode MRM
Flow rate: 0.5-1.0 ml/min

It is recommended to set the scan time to a value that allows a minimum of 10 data points over the whole peak width.

Pre-analytic treatment

Urine is used for analysis. Samples are stable up to 5 days at +2 to +8°C. For longer storage up to 3 months keep samples frozen below -18°C.

Sample Preparation

    • Place 50 μl sample/calibrator/MassCheck® control in autosampler vial.
    • Dilute as required by the instrument with Master Mixture (minimum dilution of 1:5).
    • Vortex briefly.
    • Inject up to 20 μl into the LC-MS/MS system.

Master Mixture
Example for 100 samples and a target dilution of 1:10:
Add 2.5 ml Internal Standard Mix to 42.5 ml Dilution Buffer. Add 450 μl of this mixture to 50 μl sample.