Page:NIOSH Manual of Analytical Methods - 9106.pdf/19

 METHAMPHETAMINE. . .on Wipes by Liquid-Liquid Extraction: METHOD 9106, Issue 1, dated 17 October 2011 - Page 19 of 31

Table 9a. Recommended internal standards and best application(1) COMPOUND NAME

CAS

(±)-Amphetamine-D11 (±)-Amphetamine-D8 (±)-Amphetamine-D6 (±)-Methamphetamine-D14 (±)-Methamphetamine-D11 (±)-Methamphetamine-D9 N-Methylphenethylamine Phencyclidine-D5 MDEA-D6(2) N-Propylamphetamine(2)

Not available 145225-00-9 Not available Not available 152477-88-8 Not available 589-08-2 60124-86-9 160227-44-1 Not available

MW as free base 146.12 143.15 141.16 163.12 160.15 158.16 135.23 248.35 213.22 177.29

Quant. Ion

Secondary Ion

COMMENTS

128 159(3) 123 128 126 123 104 247 165 156

Preferred analog for amphetamine Alternate for amphetamine-D11 Alternate for amphetamine-D11 Preferred methamphetamine analog Alternate for methamphetamine-D14 Alternate for methamphetamine-D14 Alternate for methamphetamine-D14 Use only for phencyclidine. Use only for MDEA. Alternate for MDEA-D6

160 126(3) 160 177 176 177 156 205 190 198

(1)	 Care must be exercised in the selection of internal standards for each analyte because of differences in derivatization efficiencies due to structural differences. a.	 Deuterated analogs of each target analyte may be acceptable as internal standards if they are isotopically pure enough and their ions do not interfere with the quantification ions (usually base peaks) of the target analyte, especially at the limit of detection for the target analyte. Conversely it is also important that ions in the target analyte, especially at high concentrations, do not interfere with the quantification ion (usually base peaks) of any deuterated analog used as the internal standard. b.	 The more highly deuterated an analog, the more it will chromatographically separate from the target analyte, reducing interference from common ions. c.	 Phentermine and mephentermine have been used as internal standards. Such use is not advised in this method because of their reported occasional use as adulterants in certain illicit drugs such as MDMA. (2)	 N-Propylamphetamine and MDEA-D6 are only applicable to MDEA and other hindered amines (e.g. fenfluramine and MBDB) due to similar steric hindrance at the nitrogen (N-ethyl or N-propyl substitution) which affects derivatization efficiency. (3)	 It is better to use m/z 126 because at high concentration levels unlabelled amphetamine contributes significant interference to m/z 159 of amphetamine-D8.

Table 9b. Recommended best application of internal standards Recommended Deuterated Internal Standards

TARGET ANALYTE Amphetamine Caffeine Ephedrine MDEA MDMA Methamphetamine Phencyclidine Phentermine (±)-Norephedrine(4) Pseudoephedrine

Amphetamine-D11(2) X X

Methamphetamine-D14(2) X X X

MDEA-D6(1)

Recommended Alternate Non-deuterated Internal Standards(3) Phencyclidine-D5

N-Methylphenethylamine X X X

4-Phenyl-1butyl-amine

X

X X

X X X

X X

N-Propyl-amphetamine(1)

X

X

X X X X X

X

X

(1)	 N-Propylamphetamine and MDEA-D6 are only applicable to MDEA and other hindered amines (e.g. fenfluramine and MBDB) due to similar steric hindrance at the nitrogen (N-ethyl or N-propyl substitution) which affects derivatization efficiency. (2)	 The alternate deuterated compounds listed in part A above may be used. Avoid ring-labeled amphetamine-D5 (CAS 65538-33-2) since the primary (quantification) ion is the same as for amphetamine and GC peaks overlap significantly. Also avoid methamphetamine-D5 (CAS 60124-88-1) since GC peaks significantly overlap and secondary ions for the chlorodifluoroacetyl derivative are not baseline resolved. (3)	 The listed non-deuterated compounds are effective as internal standards for the listed target analytes. Non-deuterated internal standards might not be permissible. (4)	 (±)-Norephedrine is the same as (±)-phenylpropanolamine.

NIOSH Manual of Analytical Methods (NMAM), Fifth Edition

Method rev. 1.1.1