19
well as updating methods is critical to ongoing research and service development.
GC-MS vs. LC-MS
Gas chromatography mass spectrometry (GC-MS) is the traditional approach to toxicological drug screening using general unknown analysis, but has steadily been overshadowed by the rapid turnaround time, ease of use and high sensitivity of innovative LC-MS methods. Despite the increased popularity of LC-MS, Dr Böttcher’s laboratory still uses GC-MS for screening certain samples, as some substances are not visible using LC-MS. For routine work the laboratory now uses the Toxtyper™ - an LC-MSn Daltonics.
library-based solution from Bruker
“For routine general unknown analysis, we don’t use GC- MS anymore but in some cases, particularly in post-mortems where the matrix may be decomposed, it is still a useful backup technique. Post-mortems produce a lot of ion suppression in LC-MS, and the results are less honest than GC-MS results. The Toxtyper™ is a better way to handle the samples and get more satisfied customers – our customers have learned that we’re quicker now, and have more sensitive techniques for most substances,” explained Dr Böttcher.
Before switching to LC-MS, general unknown analysis using GC-MS on oral fluid was not cost-effective, and therefore not offered to customers. If customers are unaware that a certain type of screening is possible, they will not generate demand for it. The introduction of the Toxtyper™ allowed the laboratory to lower the cost of general unknown analysis, and therefore offer this service. To herald this, last year at the German Addiction Medicine Conference, the group’s presentation won the first prize – an unusual accomplishment for a laboratory topic in addiction medicine. “They were convinced that this was a very nice approach, because with one shot you can see so many substances,” commented Dr Böttcher.
Another reason LC-MS is increasingly favoured over GC- MS is the reduction in sample preparation time. Dr Böttcher explained how these time savings occur:
“With GC-MS, you have to complete three sample preparation steps – hydrolysis, extraction and derivatisation – before you can run the samples, all of which are very time consuming. All these steps are very selective and this is why we have a loss of substances. In addition, the samples must be run in batches as sample prep is so cumbersome, so if an urgent sample arrives late it is uneconomical to add to the routine. This is disadvantageous for general unknown analysis, as you don’t know what you are searching for in the first place. The Toxtyper system does not require these selective sample preparation steps and therefore, random access is possible. Post-run time is also greatly reduced compared to GC-MS and data-mining is more efficient, and you don’t need as much experience.”
Screening Capabilities
In some cases, customers might know which drug they want to screen for, in which instance a multi-targeted screening approach can be used. The sensitivity of this method is much higher than
Sensitivity
general unknown analysis (untargeted approach), but in cases of intoxication where the drug group involved is not known, general unknown analysis is required (Table 1).
Table 1: LC-MS drug screening capabilities at the MVZ Laboratory Dessau, Limbach Group.
General unknown screening
Number of substances
Sample type
Screening capabilities
>4000
Oral fl uid, urine, blood, vitreous humor, gastric contents
General Unknown Screening
Screening for the complete broad range of drugs including:
Opiates/opioids Benzodiazepines
145 Synthetic cannabinoids Amphetamines Antidepressants and many more
1-25 ng/ml
Multi-target screening (LC-MS/MS)
68
Oral fl uid, urine, blood, vitreous humor, hair, meconium
Dedicated methods
Ø Opiates/opioids = 65 substances
Ø Benzodiazepines and set substances = 75 substances
Ø Synthetic cannabinoids = 100 substances
Ø Amphetamines/designer drugs = 70 substances
0.1-2 ng/ml
Multi-target analysis is conducted and embedded in the laboratory’s multi-target analytical system with LC-MS/MS. This can be modifi ed and adapted to the customer’s individual needs, and currently holds the capability to screen for 68 different substances. The laboratory’s dedicated multi-target methods, for example an opiate method or a benzodiazepine method, are comprehensive for that specifi c substance class.
“The customer usually decides when we conduct multi-target analysis or general unknown analysis, but this can depend on the case. For example, if a certain case cannot be solved using one dedicated analysis, general unknown analysis is implemented. But if a customer requests an opioid test, we would use the dedicated opioid method. For the opioid method we can test for over 60 substances, the benzodiazepine method, 50 substances and with the synthetic cannabinoid method we can test for approximately 100 substances. This can be applied to oral fl uid, but also other body fl uids,” commented Dr Böttcher.
In addition to ultra-high performance liquid chromatography (UHPLC), the LC-MS solution draws upon a comprehensive drug library for toxicological analysis. Dr Böttcher describes how the availability of such a library facilitates their work:
“When we heard that a library is available, which is at least the same size as the GC-MS library, but with the addition of glucuronides, we were immediately interested. If the library contains all the important glucuronides, hydrolysing isn’t necessary. To establish such a library on your own is very complicated, because you can’t buy these glucuronide molecules. Hydrolysing cleaves the glucuronides, which is time-consuming and selective because some substances are not cleaved 100%, and you can’t buy these substances to verify your methods. This is not widespread knowledge, and is an important issue in urine toxicology. The combination of the library containing the glucuronides and the Toxtyper™
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