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Journal of Chromatography A, 1518 (2017) 70–77

Contents lists available at ScienceDirect

Journal of Chromatography A

jo ur nal ho me pag e: www.elsev ier .com/ locate /chroma

eneric gas chromatography-flame ionization detection method foruantitation of volatile amines in pharmaceutical drugs and synthetic

ntermediates

abriel C. Graffiusa,∗, Brandon M. Jochera, Daniel Zewgea, Holst M. Halseya, Gary Leeb,rank Bernardonia, Xiaodong Bua, Robert Hartmana, Erik L. Regaladoa,∗

Process Research & Development, MRL, Merck & Co., Inc., Rahway, NJ 07065, USAAgilent Technologies, Incorporated, Wilmington, DE 19808, USA

r t i c l e i n f o

rticle history:eceived 25 July 2017eceived in revised form 16 August 2017ccepted 17 August 2017vailable online 23 August 2017

eywords:as chromatography-flame ionizationetector

a b s t r a c t

Volatile amines are among the most frequently used chemicals in organic and pharmaceutical chem-istry. Synthetic route optimization often involves the evaluation of several different amines requiringthe development and validation of analytical methods for quantitation of residual amine levels. Herein,a simple and fast generic GC-FID method on an Agilent J&W CP-Volamine capillary column (using eitherHe or H2 as the carrier gas) capable of separating over 25 volatile amines and other basic polar speciescommonly used in pharmaceutical chemistry workflows is described. This 16 min method is successfullyapplied to the analysis and quantitation of volatile amines in a variety of pharmaceutically-related drugsand synthetic intermediates. Method validation experiments showed excellent analytical performance

ethod developmentolatile aminesasic compoundsharmaceutical analysisapillary column

in linearity, recovery, repeatability, and limit of quantitation and detection. In addition, diverse examplesfor the application of this method to the simultaneous determination of other amine-related chemicals inreaction mixtures are illustrated, thereby indicating that these GC-FID method conditions can be effec-tively used as starting point during method development for the analysis of other basic polar speciesbeyond the validated list of amines described in this study.

© 2017 Elsevier B.V. All rights reserved.

. Introduction

Volatile amines are among the most frequently used compoundsn pharmaceutical chemistry due to their basic properties andow boiling point which allow the chemist to control the pH ofeaction mixtures and improve product yield [1–3]. Optimizationf the synthetic route in drug development and manufacturingnvolves constant change and the screening of numerous reactionariables [4–7] including volatile amines. The selection of the “opti-al” amine by the synthetic chemist requires a combination of

) improvement in reaction performance and 2) how effectivelyhe amine itself can be removed during the subsequent chemicalrocesses. In this regard, the time spent developing new analytical

ethods for quantitation of residual amine content prior to each

nalysis session becomes a constraining bottleneck in syntheticoute development.

∗ Corresponding authors.E-mail addresses: gabriel graffius@merck.com (G.C. Graffius),

rik.regalado@merck.com (E.L. Regalado).

ttp://dx.doi.org/10.1016/j.chroma.2017.08.048021-9673/© 2017 Elsevier B.V. All rights reserved.

A wide spectrum of extraction procedures combined withchromatographic techniques have been previously developed forthe quantitation of amines including liquid chromatography-mass spectrometry (LC–MS) [8], ion chromatography-conductivitydetection (IC-CD) [9], IC-MS [10], gas chromatography-flame ion-ization detection (GC-FID) [11–15] and GC–MS [16–18] amongothers. Derivatization prior to chromatographic separation withabsorbance [19–23], fluorescence [24,25] or MS [26] detection hasalso been extensively used. However, most of previous proceduresrequire detailed sample preparation techniques and specific instru-mentation. In addition, previous methods are focused on a verynarrow group of volatile amines and do not have the potentialto be used universally when working with the diverse group ofamines commonly used during pharmaceutical research and devel-opment. Additionally, the highly polar nature of the amines leadsto poor peak shape, limiting the quantitation and linear ranges ofthe analyses under most conditions.

In the last decade, the development and validation of genericor more universal chromatographic methods that cover multiplerelated analytes in a single experimental run has gained favor inboth academia and industry [10,18,19,27–33]. This approach can

omatogr. A 1518 (2017) 70–77 71

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Table 1GC-FID operation conditions for the generic amine method.

Parameter Setting

Analytical columnType Agilent J&W CP-VolamineLength 30 mInternal diameter 320 �mFilm thickness 5 �mCarrier gas He (99.999%)Carrier gas flow rate 2.0 mL/min

Oven temperatureInitial temperature 40 ◦CInitial holding time 2 minFirst temperature ramp 11 ◦C/minSecond temperature 120 ◦CSecond holding time 0 minSecond temperature ramp 33 ◦C/minFinal temperature 250 ◦CFinal holding time 3 minAnalysis time 16.21 min

Injector parametersa

Pre- Wash 1 3 times with ACN/H2O (50/50, v/v)Pre- Wash 2 3 times with DiluentPost- Wash 1 3 times with DiluentPost-Wash 2 3 times with ACN/H2O (50/50, v/v)Sample wash 3Injector pumps 5Type SplitTemperature 200 ◦CSplit ratio 50Split flow 100 mL/min

DetectorType FIDTemperature 260 ◦CMake-up gas flow 25 mL/min

*At the end of a sequence, the flow rate decreased to 1.0 mL/min and the split ratio to2:1 as a standby method to reduce the total gas consumption. For long-term storage,lower the temperature and turn off the detector flame.a

G.C. Graffius et al. / J. Chr

reatly enhance the speed at which chemists can generate accu-ate and quality data to support the development of new syntheticoutes. In this study, we report a new systematic approach for thenalysis of over 25 volatile amines and other basic polar species in aingle 16 min chromatographic run using conventional and readilyvailable GC-FID instrumentation. The use of this simple and fasteneric GC-FID method using either He or H2 as carrier gas for thenalysis of residual amine content in pharmaceuticals is demon-trated with full validation data provided to enable this method toe immediately applied in a regulatory setting.

. Experimental

.1. Chemicals and reagents

Methylamine, dimethylamine, ethylamine, tert-butylamine,iethylamine, ethylenediamine, ethanolamine, pyridine,imethylformamide (DMF), piperidine, morpholine, 3-dimethylamino)propylamine, N,N-dimethylacetamideDMAc), N-propylamine, o-anisidine, p-anisidine, m-nisidine, dimethylcyclohexane-1,2-diamine (DMCHDA),,3-dimethyl-3,4,5,6-tetrahydro-2-pyrimidinone (DMPU) andetramethylenediamine were obtained from Sigma-Aldrich, Inc. (Stouis, MO, USA). Trimethylamine, isopropylamine, n-butylamine,nd 2-phenylethylamine were obtained from Tokyo Chemicalndustry Co. (Portland, OR). Ethylmethylamine and sec-butylamine

ere obtained from Acros Organics (Fair Lawn, NJ, USA). Ace-onitrile and triethylamine were obtained from Fisher ScientificFair Lawn, NJ, USA). 3-(methylamino)propylamine, N-methyl-2-yrrolidone (NMP), and 1,3-dimethyl-2-imidazolidinone (DMI)ere obtained from Honeywell Fluka (St. Louis, MO, USA). 1,3-iaminopropane was obtained from MP Biomedicals (Solon, OH,SA).

.2. GC-FID conditions

Residual amine analyses were performed primarily on an Agi-ent 6890N GC-FID with an Agilent 7683 B injector. The system

as controlled by EmpowerTM 3 Chromatographic System (Waters,ilford, MA, USA). All amines were separated on an Agilent J&W CP-

olamine (30 m x 0.32 mm, 5.0 �m film thickness column, CP7447).C-FID experimental conditions are detailed in Table 1.

.3. Validation experiments

The GC experiments were designed to satisfy all requirementsor pre-filing and original filing validation. The primary diluent forhese experiments was ACN/H2O (50/50, v/v) as it had the leastnterference and/or contamination with the amines of interest. Sev-ral other diluents planned for future validation work not includedn this paper are THF, DMAC, DMAC/H2O, DMF, DMSO, DMI, andMP. Precision: Repeatability was evaluated for 6 injections of stan-ards prepared at 0.1% v/v, an intermediate level (typically 0.01%/v), and the LOQ. The intermediate and LOQ concentrations wereelected for each amine based on its linear range. Valid precisionas claimed if the% relative standard deviation (RSD) was below

0% at the intermediate and 0.1% v/v level. Linearity: Linearity forach amine was established by a minimum of 5 data points, specifico each amine, ranging from the LOQ to 0.1% v/v, with an additionaloint taken at 0.2% v/v. For example, linearity points for Pyridine

ncluded: 0.0002% v/v (LOQ), 0.0004% v/v, 0.001% v/v, 0.002% v/v,.01% v/v, 0.04% v/v, 0.1% v/v, and 0.2% v/v. A minimum of three

njections of each dilution were made and the average was taken.cceptable linearity was determined based on correlation coeffi-ient (R) ≥ 0.9900. A summary of the linearity for each amine ishown as part of Table 2. LOQ/LOD: the Limit of Quantitation (LOQ)

ACN/H2O (50/50, v/v) used in the washing procedure dramatically reduces carry-over, yet diluent is used immediately prior to the sampling. The validation containedhere-in also utilized ACN/H2O (50/50, v/v) as the diluent.

was determined as (a) the concentration that had a minimum sig-nal to noise ratio (S/N) of 10:1, and (b) had a maximum of 25%RSD for area counts over 6 injections. The LOD was established bydetermining the concentration that yielded a minimum signal-to-noise ratio of 3:1. A summary of the LOD and LOQ is also shownas part of Table 2. Specificity: The resolution of all analytes wasestablished with respect to each other. The method was consideredspecific to a particular amine if the resolution factor between it andany other possible interference was greater than 1. Minor adjust-ments to the recommended temperature gradient program may bemade to improve resolution between specific pairs of amines. Theauthors note that interactions between amines may occur duringthe sampling and analysis and therefore impact the specificity ofthe method.

2.4. Preparation of standards and samples

Stock standards and dilutions were prepared following GMPprocedures in volumetric flasks using Grade A glass pipettes. A 1%v/v stock standard solution was typically prepared by diluting 1 mLof the neat compound into a 100 mL volumetric flask and dilutedto the mark with diluent. From the stock standard preparation,serial dilutions were performed to prepare the linearity standards,specific to the linear range of each amine. Standards used for quan-

titative analysis are prepared at similar concentration to that ofthe target concentration in the sample. For sample analysis, solidsare weighed and diluted at a concentration necessary to obtain thedesired LOQ (see Table 2 for example calculations). To determine

72 G.C. Graffius et al. / J. Chromatogr. A 1518 (2017) 70–77

Table 2Summary of Validation Results for the Generic Amine Method.

No Analyte Rt (min)±RSDa Density (g/mL) 50 mg/mL dilution

LOD [2]Weight% (s/n)

LOQ [3]Weight% (s/n)

Linear rangeWeight% (R2)

1 Methylamine(40% wt in water)

2.62 ± 0.05% 0.662 0.013(46)

0.026(164)

0.026–1.3(0.999)

2 Dimethylamine(40% wt in water)

3.49 ± 0.09% 0.706 0.014(50)

0.028(203)

0.028–1.4(0.999)

3 Ethylamine(2.0 M in THF)

3.63 ± 0.06% 0.689 0.014(44)

0.028(121)

0.028–1.4(0.999)

4 Trimethylamine(28% in water)

3.78 ± 0.05% 0.630 0.006(85)

0.013(365)

0.013–1.3(0.999)

5 Isopropylamineb

(99%)4.58 ± 0.02% 0.689 0.003

(22)0.007(56)

0.007–1.4(0.999)

6 Ethylmethylamine(97%)

4.95 ± 0.05% 0.688 0.014(14)

0.028(49)

0.028–1.4(0.999)

7 tert-Butylamine(99.50%)

5.32 ± 0.04% 0.696 0.003(7)

0.006(27)

0.006–1.4(0.999)

8 n-Propylamine(99%)

5.67 ± 0.02% 0.719 0.007(10)

0.014(55)

0.014–1.5(0.999)

9 Diethylamine(99.5%)

6.60 ± 0.02% 0.707 0.007(15)

0.014(60)

0.014–1.4(0.999)

10 sec-Butylamine(99%)

6.90 ± 0.04% 0.724 0.003(17)

0.007(84)

0.007–1.4(0.999)

11 Tetrohydrofuran(99%)

7.85 ± 0.01% 0.883 0.002(17)

0.004(34)

0.004–1.8(1.000)

12 n-Butylamine(99.0%)

7.99 ± 0.01% 0.733 0.007(63)

0.015(278)

0.015–1.5(0.999)

13 Ethylenediamine(99.5%)

8.39 ± 0.01% 0.898 0.036(74)

0.072(155)

0.072–1.8(0.999)

14 Ethanolamine(99%)

8.40 ± 0.08% 1.012 0.020(11)

0.040(34)

0.040–2.0(0.999)

15 Triethylamine(99%)

9.28 ± 0.02 0.726 0.001(7)

0.003(17)

0.003–1.5(0.999)

16 Pyridine(99.80%)

10.11 ± 0.02% 0.978 0.002(32)

0.004(72)

0.004–2.0(0.999)

17 1,3-Diaminopropane(99%)

10.47 ± 0.02% 0.888 0.018(10)

0.036(180)

0.036–1.8(0.999)

18 DMF(99.90%)

10.38 ± 0.01% 0.944 0.002(9)

0.004(26)

0.004–1.9(1.000)

19 Piperidine(99%)

10.54 ± 0.02% 0.862 0.003(14)

0.009(98)

0.009–1.7(0.999)

20 Morpholine(99.0%)

10.84 ± 0.02% 0.996 0.002(9)

0.004(30)

0.004–2.0(0.999)

21 3-(methylamino)propylamine(97%)

11.21 ± 0.02% 0.844 0.017(20)

0.034(140)

0.034–1.7(0.999)

22 3-(dimethylamino)propylamine(99%)

11.40 ± 0.02% 0.812 0.016(42)

0.032(184)

0.032–1.6(0.999)

23 DMAc(99%)

11.53 ± 0.02% 0.937 0.002(21)

0.004(50)

0.004–1.9(0.999)

24 Tetraethylenediamine(99%)

11.77 ± 0.01% 0.877 0.009(5)

0.018(37)

0.018–1.8(0.999)

25 NMP(99.9%)

13.13 ± 0.01% 1.027 0.002(37)

0.004(81)

0.004–2.0(1.000)

26 DMI(99%)

13.67 ± 0.01% 1.052 0.002(28)

0.004(60)

0.004–2.1(0.999)

27 2-Phenylethylamine(98.0%)

13.72 ± 0.01% 0.964 0.002(19)

0.004(68)

0.004–1.9(0.999)

28 DMPU(98%)

14.71 ± 0.01% 1.064 0.004(27)

0.011(57)

0.011–2.1(0.999)

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Stability of the column stationary phase is limited when using diluent with high wa Repeatability in RT was performed at 0.01% v/v.b Isopropylamine was validated using DMI as diluent due to the ACN diluent inte

he weight% of residual amine in an actual sample, the followingquation can be used:

P =(Asmpl) (VPstd)

(Vsmpl

)(Dslvnt)

(Astd)(

Msmpl

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WP = weight percent of the amine in the drugAsmpl = area counts for the sampleVPstd = volume percent of the standardVsmpl = volume of sample diluent used (mL)

ontent.

ce.

Dslvnt = density of solvent to be determined (g/mL)Astd = area counts of the standardMsmpl = mass of the sample (g)

2.5. Accuracy study (Spike and recovery)

The amines utilized in the synthesis of four separate MSD pro-grams and four generic Active Pharmaceutical Ingredients (API)were spiked into the sample matrix of the API at levels rangingfrom a minimum of the filed specification. Grazoprevir, Sitagliptin,

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G.C. Graffius et al. / J. Chr

erubecestat, Ceftolozane (Merck & Co., Inc., Rahway, NJ, USA),pinephrine, ibuprofen, 4-flavanone and quercetin (Sigma-Aldrich,nc.) were all prepared individually at approximately 20 mg/mL.CN/H2O (50/50, v/v) was used as diluent for all drugs, except

or Sitagliptin, Verubecestat and Ceftolozane (DMI). Each analyteas spiked into the sample matrix at three concentrations levels

0.002, 0.01 and 0.1%). Duplicate injections of two sample prepara-ions were analyzed, and the experimental result was compared tohe theoretical spiked value to assess recovery using the followingquation:

Recovery

= Wt% of Solvent Analyte Determined Experimentally

Theoretical Wt% Based on Spike× 10

. Results and discussion

The development and validation of a generic GC-FID methodor chromatographic separation and analysis of multiple volatilemines in a single experimental run is vital for a fast and reli-ble turnaround of analytical results. All the analytes selected inhis investigation (Table 2) form part of a comprehensive list ofolatile amines and other basic polar species that have been used byedicinal and process chemists in pharmaceutical laboratories for

rug research and development during the last decade. Fig. 1 illus-rates a new optimized method on a CP-Volamine capillary columnsing a gradient temperature program capable of separating over5 amines and other basic polar species in less than 16 min usingonventional GC-FID instrumentation. This is a fused silica column,oated with a base deactivated non-polar siloxane type station-ry phase (SP) which creates a highly inert coating surface with ainimum degree of adsorption for difficult basic compounds that

enerally tail on traditional gas chromatography stationary phases.High-boiling-point solvents (e.g. DMAc, DMSO, DMF, NMP and

MI) are typically the preferred choice of diluents for GC analysisecause they often afford excellent solubility and minimal inter-erence with earlier eluting analytes in the GC assay. However,C-FID and GC–MS analyses of some of these diluents clearly show

number of high-boiling point impurities, interfering with somef the amines targeted in this method. Interestingly, this methods capable to separate a lot of impurities from the diluent peakndicating that it can be used to test the quality of diluents usedn synthetic reactions, which is very useful to help establish theource of unexpected impurities that may be observed in the finalPI and synthetic intermediates. Overall, 50/50 ACN/H2O (v/v) was

ound to be a good diluent choice to demonstrate this method as iteduced carryover (see pre/post-wash cycles in Table 1) and mini-ized potential coelution with strongly retained amines that elute

lose to the high-boiling point diluents. Isopropylamine (5) is thenly component that elutes too closely to the ACN diluent peak. Forhis particular case, a high-boing point diluent (DMI) was selectedor method validation.

With the selection of diluent and GC-FID conditions, we nextocused on the validation experiments. Table 2 summarizes the lin-arity range, precision, and LOQ/LOD experiments performed forll amines and some additional low and high boiling point solventsypically used as diluents during GC-FID analysis. Response factorsf standards were determined to be linear within the range stud-ed, having a correlation coefficient (R) ≥0.990. The% RSD for allested standard solutions was ≤5%, with the majority ≤3%. Thesealidation experiments serve as the basis for the method used in

he initial stages of drug development, prior to expanded valida-ion of the method for the specific product. The quantitation ranges0.007–0.013% w/w) and the weight% (wt%) calculations for a the-retical 50 mg/mL sample preparation are also listed in Table 2.

gr. A 1518 (2017) 70–77 73

However, the detection range for a particular amine is usuallydependent upon the solubility of the drug substance in the dilu-ent. For example, the quantitation limit of residual pyridine in adrug substance that is soluble at 50 mg/mL is 5 times lower thanthe quantitation limit of pyridine in a drug substance that is solubleat only 10 mg/mL.

The reliability of the method was confirmed by recovery exper-iments performed in multiple pharmaceuticals containing diversefunctional groups (Table 3): MSD APIs (Grazoprevir, Sitagliptin,Verubecestat and Ceftolozane), as well as generic drugs and nat-ural products (epinephrine, ibuprofen, 4-flavanone and quercetin).Three different concentrations across the linear range (0.1, 0.01 and0.002% v/v) were spiked into each drug. Analytes spiked into MSDAPIs are the same used during drug synthesis and manufactur-ing, e.g. triethylamine (TEA) and N,N-dimethylacetamide (DMAc)in Ceftolozane, 1,3-dimethyl-3,4,5,6-tetrahydro-2-pyrimidinone(DMPU) in Verubecestat, isopropylamine in Sitagliptin, and pyri-dine in Grazoprevir. However, a diverse group of amines wererandomly selected for recovery experiments in the case of genericdrugs and natural products, e.g. sec-butylamine and TEA inepinephrine, DMAc and pyridine in ibuprofen, diethylamine, n-butylamine and n-propylamine in 4-flavanone, and DMAc andpyridine in quercetin. The average recovery (%) was calculated fromduplicate injections of two sample preparations as described in theexperimental section. The results depicted in Table 3 show recover-ies that meet the GMP requirements (75–125%) across all differentspiking levels in all drugs, with overall relative standard deviationbelow 5%. It is important to point out that spike and recovery is avery important criteria in method validation and it is recommendedto perform these experiments in cases where this method is usedfor quantitation of volatile amines in any other pharmaceuticals. Incase of low recovery values and/or analyte interference, the use ofhead-space sampling prior to GC-FID analysis can help minimizepotential matrix effects. Finally, determination of pyridine, THF,isopropylamine, ethylendiamine, DMAc and TEA content (% w/w)in MSD drugs and synthetic intermediate show results that meetthe specifications set for batch release, as can be seen in Table 3.

This method covers a diverse set of volatile amines and high-boiling point diluents commonly used by medicinal and processchemists in the synthesis of new synthetic intermediates and phar-maceutical ingredients. These GC-FID conditions can also serve asa starting point for method development in order to analyze otherchallenging polar amines not represented in Table 2. Fig. 2 illus-trates numerous cases where minor modifications of this method(using other diluent instead of ACN/H2O) allowed us to solvedifficult analytical separations for quantitative analyses of otheramine-related chemicals used during process development.

In the example shown in Fig. 2a, the same method conditionsusing DMAc as the diluent are effectively employed to the anal-ysis of 1,3-dimethyl-3,4,5,6-tetrahydro-2-pyrimidinone (DMPU),a polar aprotic solvent used as an additive to minimize aggre-gation of lithiated species [34] for the synthesis of intermediate3 via flow chemistry [35]. Fig. 2b provides an example from arecent project of how this method can also be used for simul-taneous determination of ethylenediamine (EDA) and the ligand(dimethylcyclohexane-1,2-diamine) levels in the copper catalyzedcoupling of an amide (intermediate 5) with an aryl bromide inter-mediate 4 [36]. In another example (Fig. 2c), a method was requiredfor starting material testing [37]. Once again, the exact methodconditions delivered baseline resolution and excellent peak shapefor the separation of anisidine isomers which also happen to bepotential mutagenic impurities (PMIs 30-32). Interestingly, all tar-

get analytes presented in Fig. 2a-c are baseline resolved from oneanother without the need of method optimization. It is impor-tant to point out that having many of these species in the samereaction mixture is highly unlikely. However, having a validated

74 G.C. Graffius et al. / J. Chromatogr. A 1518 (2017) 70–77

Fig. 1. GC-FID method for analysis and separation of over 25 amines and other basic polar species. Method conditions are detailed in Table 1 (Experimental section).

Table 3Quantitation of amine in pharmaceutical drugs and synthetic intermediates.

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eneric method in place capable of resolving complex multicom-onent mixtures of volatile basic species increases the simplicitynd speed of troubleshooting process development.

The cumulative solvent use and waste from chromatographicystems have been a very important topic targeted in recent greenhemistry investigations [38–46] including the replacement ofelium with hydrogen as the carrier gas for routine GC analysis47–50]. Fig. 3 illustrates the GC-FID profile of separation of all 27olatile amines using H2 instead of He as the carrier gas. H2 carrieras was able to provide excellent separation of the amines with noodifications to the chromatographic parameters used with He.verall, the H2 method elution is one minute faster and providesetter chromatographic performance including sharper peaks, lessailing, and better separation of critical pairs. It is important to notehat the H2 method demonstrated improved separation of amines3 (ethylenediamine) and 14 (ethanolamine), two components that

oelute using He as carrier gas. The overall better chromatographicerformance of H2 over He in terms of speed and separation helpso illustrate the power of H2 as carrier gas for high linear velocity

methods. Full method validation using H2 as the carrier gas whilefollowing standard operating procedures (SOPs) and good manu-facturing practice (GMP) requirements will be carried out either bythis or another laboratory in the future.

4. Conclusions

Process chemistry investigations in the pharmaceutical industryoften involve optimization of numerous reaction variables, includ-ing volatile amines. Consequently, the analytical chemists have tospend time and resources developing and validating chromato-graphic methods for determination of residual amine content priorto each analysis session. To better meet these needs, a simpleand fast generic method using conventional GC-FID technology(using either He or H2 as carrier gas) capable of separating over 25

volatile amines and other basic polar compounds commonly used inpharmaceutical chemistry workflows was developed and validated.Validation experiments showed excellent sensitivity, precision, lin-ear correlation, and accuracy for all of the amines. This method has

G.C. Graffius et al. / J. Chromatogr. A 1518 (2017) 70–77 75

Fig. 2. Direct application of GC-FID method to the separation and analysis of other volatile basic compounds. a) Analysis of 1,3-dimethyl-3,4,5,6-tetrahydro-2-pyrimidinone(DMPU: 28) in a synthetic intermediate using DMAc as diluent. b) Simultaneous monitoring of ethylenediamine (EDA: 13) and the ligand (dimethylcyclohexane-1,2-diamine:29) levels in a copper catalyzed reaction mixture using DMAc as diluent. c) Separation of potential mutagenic impurities (PMIs 30-32).

Fig. 3. GC-FID method using hydrogen as carrier gas for the separation of volatile amines. Method conditions are equivalent to those detailed in Table 1 (Experimentalsection).

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een successfully implemented for quantitation of volatile aminesn pharmaceutical drugs and synthetic intermediates. In addition,iverse examples of the use of this method for simultaneous deter-ination of other amine-related chemicals in reaction mixturesere illustrated indicating that these GC-FID conditions can be

ffectively used as a starting point for solving challenging sepa-ations and analysis of volatile polar species beyond the validatedist described in this study.

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