stability studies of amphetamine and ephedrine derivatives in urine
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Stability studies of amphetamine and ephe
drine derivatives in urine
อาจารย์�ที่ปร�กษา อ.ดร.พั�ลลพั คั�นธิ�ย์งคั�
นางสาวดร�ณร�ตน� แก�วมู ล รหั�สน�กศึ�กษา 51312305
Stability studies of amphetamine and ephedrin
e derivatives in urine
By C. Jim enez , R. de la Torre
M. Ventura ,J. Segura ,R. Ventura
Introduction
Knowledge of the stability of drugs in biological fluids is critical for proper interpretation of
analytical results
• thermal
• chemical
• degradation, matrix degradation
• metabolism, hydrolysis
• transport,
• handling or sample
• storage conditions
Lossesof analys
Stability testing can be used
Stability testing can be used
• explain discrepancies between reanalyses long after initial analyses
• determine time limits that must be imposed between the collection and analysis of samples for pharmacokinetic studies
• identify the optimal storage conditions
DHHS Guidelines for Federal Workplace Drug Testing
(USA) 1998
retain all confirmed drug positive urine
least 1 year
in frozen storage
Introduction
None psychostimulants like
ephedrine derivatives.
Ephedrine / amphetamine derivatives
are included in the list of prohibited substances
Sample
• ephedrine derivatives
ephedrine, norephedrine, methylephedrine, pseudoephedrine, and norpseudoephedrine
• amphetamine derivatives
(amphetamine, methamphetamine, 3,4-methylenedioxyamphetamine (MDA),
and 3,4-methylenedioxymethamphetamine (MDMA))
Sample
Sterile sample– Long term– Shot term
Non Sterile sample
(MDMA and methamphetamine)– Long term– Shot term
Sterile samples
• Long-term stability
4 ◦C and -20 ◦C / at - 80 ◦C as reference
1, 2, 3, 6, 10, 12, 18 and 24 months.
• Short-term stability
37 ◦C / at −20 ◦C for comparison purposes.
3 and 7 days.
non Sterile samples
• Long-term stability
4 ◦C and -20 ◦C / at initial concentration as reference value for comparison
6 months
• Short-term stability
37 ◦C / at −20 ◦C for comparison purposes.
7 days.
Preparation of Sterile samples
Blank urine 2 ml + sodium azide (0.1%, w/v)
clarified by filtration (three different filters)
spiked standard
distributed in aliquots under sterile conditions
Preparation of non Sterile samples
Blank urine 2 ml + sodium azide (0.1%, w/v)
clarified by filtration (three different filters)
spiked standard
distributed in aliquots under sterile conditions in a laminar
Samples analyzed
• Calibration samples were prepared in duplicate
• A control sample (three replicates) was analyzed in
each analytical batch
• replicates of each aliquot of sample
were analyzed at random in the analytical batch
Precision and accuracy
• three different concentration
three replicates of control urine samples
• Precision was expressed as the relative standarddeviation (R.S.D.%)
• accuracy was expressed as the relative standard error (R.E.%)
Calculations
• The Dixon’s test (α = 5%)
detect outliers in the replicates (n = 5) of each aliquot
• ANOVA test (α = 5%)
Homogeneity, adsorption of the analytes on the sterilizing filter and stability compare concentrations obtained at each storage condition with a reference value (concentration of aliquots of sample stored at the reference condition).
Analysis of ephedrine derivatives
gas chromatograph (HP 5890 series II)
Analysis of amphetamine derivatives
HP 6890 series gas chromatograph
HP 5973 mass selective detector
Results
• coefficients (r 2) up to 0.990 in all calibrations• ephedrine derivatives LOQ 0.4 u g/mL - 27 ug/mL• 50% 70%.
• coefficients( r 2 ) up to 0 .9 9 0• amphetaminederivativesLOQ71.0ng/mL- 834. ng/mL• uuu uuuuuuuuuuuuuuu uuu uuuuu>60% ,>90%.
Precision and accuracy
• Both methods good precision and accuracy
• <20 % for the low-concentration control urine samples
• <15 % for the medium and high concentration control urine samples.
adsorption of the analytes on the sterilizing filter
3210
not statistically significant (p > 0.05) (data not shown), indicating that all the sample batches prepared for stability testing were homogeneous.
4
Long-term stability
-10 %
-12 - 5 %
MDA 4 C 4%
Shot -term stability
Long-term stability
did not show a significant decrease (p < 0.05)
Discussion
Moody et al.
no significant change in analytes concentration for up to 17 months. Other studies have also demonstrated the stability of these drugs in non-preserved urine at different time and temperature conditions.
Hughes et al.
• reported t he stability of amphetamine and methamphetamine in spiked urine samples stored at 4 ◦C for up to 6 months
Discussion
• For long-term stability
statistically significant only observed for the ephedrine derivatives at some of thestorage conditions tested
not exceed the intra-assay precision of the corresponding analytical methods
Dugan et al
studied the stability in clinical samples tested
before and after 1 year of storage at −20 ◦C, [8]
Paul et al.
investigated the effect of freezing (at −16 ◦C to −18 ◦C) on the concentration of amphetamine and methamphetamine in spiked urine samples stored for 45 days. In the same way, our observations are also in accord
ance with those obtained by
Clauwaert et al.
• who demonstrated the stability of MDMA and MDA in non-preserved urine samples stored at −20 ◦C, 4 ◦C and 20 ◦C for 21 weeks.
ephedrine and amphetamine derivatives
• sterile samples
• can be stored at the least. 4 ◦C
• for up to 24 months for
• non-sterile samples
• can be stored at the least. 4 ◦C
• for up to 6 months for
Discussion
• The methodology presented when applied to other analytes
• may help to determine optimal storage conditions for urine samples
• to be used as reference materials and for positive urine
• samples that should be retained in drug-testing and antidoping
• control laboratories
• The study demonstrates the feasibility of• preparing certificate reference materials of successfully s
tudied• analytes. This is of special interest for those analytes for
which a• cut-off concentration has been established as positivity c
riterion• for reporting adverse analytical findings, such as amphet
amine• derivatives in drugs of abuse testing, and ephedrine, met
hylephedrine• and cathine in antidoping control.
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