Estimating total sampling error for near infrared spectroscopic analysis of pharmaceutical blends theory of sampling to the rescue

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1 Estimting totl smpling error for ner infrred spectroscopic nlysis of phrmceuticl blends theory of smpling to the rescue A. Romn-Ospino, C. Orteg-Zuñig, A. Snchez-Pternin, S. Ortiz, K. Esbensen b nd R.J. Romñch ndres.romn@upr.edu, crlos.orteg4@upr.edu, driluz.snchez@upr.edu, stephnie.ortiz10@upr.edu, b ke@geus.dk, rodolfoj.romnch@upr.edu doi: /tosf.66 A repliction experiment ws performed to vlidte strem smpling method for phrmceuticl powder blend. A 1.5 kg powder blend ws prepred nd n in-house developed feeder ws used to divide into six sub-smples of pproximtely 250 g. Ech 250 g sub-smple (1/6 totl blender lot volume) ws deposited long rig of 3 meter length. A vlidted ner infrred (NIR) spectroscopic method ws used to determine the drug concentrtion s the powder deposited in the rig moved t liner velocity of 10 mm/sec. The depth of penetrtion of the NIR rdition ws 1.2 mm nd the smple volume nlysed ws pproximtely 180 mg. The MPE (minimum prcticl error) obtined with the system ws 0.04% w/w cetminophen (APAP), which ws considered excellent for the system. The replicte nlysis of the powder deposition provided 390 mesurements of drug concentrtion, with men APAP concentrtion of 14.93% (w/w) nd reltive stndrd devition (RSD) of 5.20%. Replicte mesurements (n = 650) of the powder deposited long single rig of 3 m length 10 provided n RSD of 2.23%, ttributble to deposition (outflow) heterogeneity. Finlly, sttic replicte nlysis of the mesurement error lone mounted to n RSD of 0.14%. The embedded replicte experiments elucidted ll sources of vrition in smpling system for phrmceuticl powder blends, nd proved relible nd highly sensitive in identifying res of non-cceptble residul heterogeneity (ded zones). Bckground The nlysis of drug concentrtion in phrmceuticl blends is mostly done through grb smpling where smpling sper (clled smpling thief in the phrmceuticl industry) is frequently inserted into blender to extrct 6 10 smples. 1,2 The extrcted mteril is then tken to lbortory where the drug concentrtion of the powder blend is determined. The smple thief is used to extrct powder mixture from specific loctions nd trnsects through the blender volume, which bsed on previous studies, hve shown greter likelihood to represent ded spots (res of residul incomplete mixing). 3 Thus, ll the components of the blender volume, the lot, do not hve the sme probbility of being extrcted for nlysis. This is structurl fult of the smpling system. If the res of incomplete mixing re not those selected with this fixed loction pproch the smpling pproch will fil to do wht it is supposed to do nd volumes with lrger residul heterogeneities will go undetected. This is the exct opposite of the objective of end-of-mixing smpling nd nlysis. 1 3 These flwed pproches re currently being complemented by non-destructive ner infrred (NIR) spectroscopic methods developed to nlyse the drug concentrtion within the blender (in-line), or t-line/off-line. The non-destructive spectroscopic methods re so fr usully interfced t single loction within the blending vessel (or intercting through window in the vessel wll). 4 If powder moves in nd out of the smpling interfce there is greter likelihood tht lrger prts of the lot will be nlysed thn with powder thief, depending on the specific combintion of nlysis volume w.r.t. mteril through-flow in reltion to the full vessel volume. But such solutions, despite hving cler potentil of being significntly better thn thief smpling, re by no mens complete solution for the desired blender mteril chrcteristion bsed on the full blender volume. To the degree tht this is not chieved (yet), the present verifiction pproches cnnot be sid to be comprehensive. However the powder mixture cn lterntively be smpled fter it leves the blender, either using physicl smpling pproch or by invoking the rpid, nd more efficient NIR spectroscopic method for nlysis. 1,2 In this pproch the powder flows down chute, or is ducted vi mini-conveyor belt, from which NIR spectrometer cn obtin spectr of the mixture. This is Process Anlyticl Technology (PAT) pproch, of gret potentil nd considerble proved merit. 5 7 Bsed on chemometrics multivrite clibrtion model it is possible to predict the drug concentrtion in the NIR-bem nlyticl volume. 8 This strem smpling pproch hs been followed experimentlly in limited number of pilot studies We here report on pioneering lbortory vlidtion of PAT strem smpling pproch where the ctive drug concentrtion is determined by NIR spectroscopy. Previous studies hve involved thorough vlidtions of NIR nlyticl methods obtining ccurte estimtes of the Totl Anlyticl Error (TAE), but hve not ddressed the ccompnying smpling errors. 4 This study describes the result of first systemtic Repliction Experiment pproch 12 in relistic lbortory setting. The systemtic repliction experiments represent new pproch to the nlysis of blends nd to estimting the effective smpling nd mesurement uncertinty within phrm We re wre of only two other forys within phrm, in which TOS is lso n importnt element, both focusing on product nlysis uncertinty 17,18 Experimentl Mterils: The blends were prepred from lctose monohydrte Grnulc (Meggle Phrm), microcrystlline cellulose Vivpur 102 (JRS Phrm) nd semi-fine cetminophen (APAP) from Mllinckrodt Inc. (Rleigh, NC). The lctose monohydrte ws pssed through U.S. Stndrd Sieve 60 (250 µm opening) before mixing. Clibrtion Model: An experimentl design ws followed to minimize correltion between components nd obtin robust Issue

2 Tble 1. Composition of clibrtion nd test set blends for NIR clibrtion model. Blend Test set APAP (% w/w) MCC (% w/w) LAC (% w/w) clibrtion model. Three component blends were prepred (correltion between mjority components is unvoidble, nd this process reduces the other two). The experimentl design softwre MODDE Umetrics (Umeå, Sweden) ws used. Settings were 14 runs, objective: screening, in D-optiml design liner model. The concentrtion rnge ws 50% bove nd below the 15.0% w/w APAP trget concentrtion, resulting in clibrtion set spnning % w/w. Tble 1 shows the concentrtions of the eight clibrtion blends prepred. Preprtion of Test Set Blend: A 1.5 kg blend with n APAP concentrtion of 15.0% (w/w) ws prepred s shown in Tble 1. This blend ws used for the entire replicte study. Description of Fourier Trnsform Ner Infrred (FT-NIR) system nd softwre to develop the clibrtion model: A Bruker Optics (Billeric, MA) Mtrix FT-NIR spectrometer ws used to obtin spectr. Clibrtion nd test set spectr were obtined t spectrl resolution of 8 cm 1 nd totl of 32 scns were verged. Ech spectrum (verge of 32 scns) requires bout 4.4 seconds. All spectr were obtined s the powder moved t liner velocity of 10 mm/s, except for the sttic repetbility test (see below). Under these conditions, ech spectrum cn be estimted to represent pproximtely 180 mg of powder mixture s shown in Figure Clibrtion models were developed in SIMCA 13.0 Umetrics (Umeå, Sweden), prtil lest squres lgorithm. NIR spectr were pre-treted with stndrd norml vrite trnsformtion nd first derivtive bsed on 17 points. The chemometric model ws performed on the cm 1 NIR spectrl rnge. The performnce of the clibrtion model ws evluted with independent test blends, k test set vlidtion A smpling system ws designed to deposit blends over the conveyor belt for simulting 1-dim industril blender outflow smpling/nlysis system. Ech powder mixture (both clibrtion nd vlidtion blends) ws deposited in 3 m long, 4 cm wide nd 3 cm deep rig by the use of n in-house developed screw feeder, s shown in Figure 2. The feeder ws operted so s to provide thick powder bed on the rig. FT-NIR spectr were obtined long the entire 3 m length rig corresponded to pproximtely 250 g of the 1.5 kg lot powder mixture. The powder surfce ws left uneven nd no ttempt ws mde to obtin flt surfce of powder in the recipient, iming to produce highly relistic industril sitution. Figure 2 shows photogrph of the system for Repliction Experiment studies (six successive rig depositions, 10 times to-nd-fro over just one outflow. The Mtrix FT-NIR spectrometer is situted t height ~10 cm to obtin spectr s the rig moves t 10 mm/ sec. The replicte experiment ws first conducted by performing 6 outflow depositions ech of pproximtely 250 g long the 3 m rig. This setup yielded pproximtely 65 spectr per outflow strem. The APAP drug concentrtion ws predicted for ech spectrum using the vlidted FT-NIR clibrtion model (multivrite clibrtion prediction). 8 The second repliction experiment consisted of moving one of the full length outflow deposition over the conveyor belt to nd fro 10 times, obtining spectr from one end to the other. The finl prt consisted of repetbility study, where six consecutive spectr were obtined t one fixed loction without moving the powder mixture or the spectrometer. This repetbility study ws itself performed totl of 6 times. All repliction experiment results re shown in Tble 2. Results nd Discussion The bove repliction experiment ws performed to vlidte specific PAT smpling/nlysis fcility for relistic 1.5 kg powder blend Figure 1. Schemtic rig illustrtion of PAT smpling by NIR spectrometer long conveyor belt mteril strem. Observe how the NIR bem only intercts with the top lyers of the mteril strem, giving rise to structurl IDE/IME contributions to the totl mesurement system error in the verticl direction[depth of penetrtion is 1.2 mm]. The estimted nlyticl mss is bout 180 mg. Figure 2. Conveyor belt ssembly (totl length 3 m) with FT-NIR spectrometer positioned t height of 10 cm nd powder feeding system (bckground). Note tht the NIR bem covers the entire width of the conveyor belt, suppressing potentil IDE contribution to the totl mesurement system error in the cross-strem direction. 72 Issue

3 Tble 2. Results of Repliction Experiments. Deposition (n = 6) Replictes b of Single Deposition (n = 10) Repetbility Study c (n = 6) Ave Std. Dev RSD (%) Spectr (#) Deposition = one deposition length (3 m) b Spectr were collected 10 times long the complete length of the rig for totl of 647 spectr c Sttic NIR bem footprint on unmoving rig; six replicted NIR spectr cquisition prepred with 15.0% (w/w) APAP concentrtion. The lot in question ws the full 1.5 kg prepred blend, from which the six repetitions of full length (3 m) 250 g rig experiment could be performed. Ech 250 grm sub-smple (1/6 totl blender lot volume) llowed bout 65 nlyses (bsed on NIR spectr) to be mde long the rig length, Figures 1 nd 2. This enbles evlution of both full nd prtil blender outflow nlysis performnce. Tble 2 shows tht the grnd verge concentrtion predicted by the NIR clibrtion model ws 14.93% (w/w), bsed on ll 390 nlyses performed for the lot, i.e. sitution in which the entire outflow mteril strem hs been nlysed. The reltive stndrd devition of this complete lot volume results ws 5.20%. These results must be considered excellent s these involve the mximl combined vrition effects stemming from i) the outflow deposition (flow segregtion), ii) residul blend heterogeneity nd iii) TAE of the PAT NIR nlyticl method. The reltive stndrd devition is termed the reltive smpling vribility (RSV) for the repliction experiment pproch. 12 Tble 2 lso shows the results from replicte nlysis of single deposition (i.e. single conveyor belt pss but repeted to-fro 10 times). This experiment ddresses the specific blend heterogeneity in one 1/6 totl lot strem only (including the ttendnt TAE). As expected, this RSV vrition is significntly lower, 2.23%. The verge drug concentrtion is here 15.21% (w/w). Thus, the verge concentrtion is different from tht when the entire lot ws nlysed. There is thus difference of +0.28% APAP, due to tht only 1/6 prt of the lot is being nlysed. The sttic nlyticl repetbility studies results (the NIR bem ws focused on single unmoving re of the powder blend nd six consecutive spectr were cquired) re lso shown in Tble 2. The reltive stndrd devition in the repetbility study is pproximtely 0.2%, ttesting to TAE only. Vribility lrger thn this nlyticl bseline represents i) residul blend heterogeneity (imperfect mixing), ii) specific outflow vribility ( deposition bove) s well s iii) possible process smpling errors for the PAT sensor system. The vrince of this nlyticl repetbility study (0.2) 2 my be subtrcted from the squre of the stndrd devition of the replicte nlysis of the single deposition to obtin mesure of the blend heterogeneity. The replictes of single deposition show stndrd devition of 0.34, nd fter subtrcting the mesurement repetbility the blend heterogeneity is Figure 3. Prediction of drug concentrtion for the 390 individul nlysis of the complete lot (six 3 m rig lengths) These vlues could be used s bseline level to improvement the smpling nd mesurement systems. Figure 3 shows the plot of the drug concentrtion vlues throughout the entire run, reveling significnt drop in drug concentrtion from pproximtely spectrum #78 to 116. This simple plot is crucil in showing tht certin prt of the blend ws responsible for the overwhelming prt the heterogeneity observed ded spot. The drug concentrtion from spectrum #81 to 100 verged 12.5% insted of the 15.0% trget level. Thus, the strem smpling pproch ws very cpble to identify incomplete mixing process without the use of smpling sper. The min feture of the repliction experiment studies concerns the possibility to pply vriogrphic chrcteristion of the outflow strem. The vriogrm function V(j) ws determined bsed on the drug concentrtion vlues predicted by the NIR clibrtion model. A lg of 1 ws bsed on consecutive predictions of drug concentrtion, ech concentrtion corresponding to pproximtely 180 mg s shown in in Figure 1. The mximum lg shown in the vriogrm is 190, since the totl number of drug concentrtion predictions ws ~390. From Figure 4 it is obvious tht the totl PAT mesurement system error is very smll (nugget effect) compred to the level of drug content vrince (sill) long the full 3m outflow strem. The rnge is pprox , i.e. the distnce within ech predicted drug concentrtion is incresingly uto-correlted for smller lgs thn this. This run lso llows simultion of the vriogrphic outflow pproch for NOC (norml opertion conditions), by excluding the smples in the intervl # (resulting in semless outflow only chrcterised by the NOC residul heterogeneity). A renewed vriogrm for this dt series is presented in Figure 4 (right), in which cn be seen tht the nugget effect is identicl, while there is very notble reduction of the sill level both fetures s expected. Renewed estimtion of the RSV 1-dim results in 2.6%. This run is fully relistic w.r.t. to its industril counterprt to the degree tht the blender used is resonbly up-sclble; ll other system elements Issue

4 Figure 4. Left: Vriogrm bsed on the totl of 390 individul nlyses of the complete lot (six 3 m rig lengths). The rnge is ~30-36; nugget effect = 0.04; sill = 0.7. The totl mesurement system uncertinty, RSV 1-dim, is therefore ~5.2% (rel). 12 Right: Sme vriogrm excluding shded re in Figure 3. would be identicl: outflow fcility, NIR spectrometer, chemometric prediction model. A recently withdrwn drft guidnce which describes the nlysis of powder blends by thief smpling requires the nlysis of drug concentrtion for t lest 10 blends from tumble blender with: 1) reltive stndrd devition 5%, nd 2) ll individul results within 10.0 percent (reltive) of the men drug concentrtion. 16 The 390 determintions of drug concentrtion disply RSD of 5.20% slightly exceeding the first requirement nd did not meet the second requirement due to the ded spot drop in concentrtion shown in Figure 3. Thus, the outflow strem smpling system is eminently cpble of finding res of heterogeneity in the entire blend lot. If the blending process were improved by eliminting the sudden drug concentrtion drop shown in Figure 3, then the RSD in drug concentrtion reduces to pproximtely 2.6% nd ll vlues re now within 10% of the men drug concentrtion stipultion. To the degree tht complete, up-sclble mesurement system cn be estblished in the lbortory, the present pproch will be ble to guide rtionl product development, to some considerble degree without pilot or full scle plnt demonstrtion until the mnufcturing process hs been brought into complete sttisticl control in the lbortory. The vlue of n outflow vriogrphic fcility hs been demonstrted nd its merits exemplified. This is the first time TOS-bsed pproch (vriogrphic nd repliction experiment) for the chrcteristion of phrmceuticl mnufcturing process hs been pplied with illustrtive nd highly stisfctory results. Acknowledgements This collbortion hs been possible thnks to the support of the Ntionl Science Foundtion (ERC reserch grnt EEC ). References 1. R. J. Romñch nd K. H. Esbensen, Smpling in phrmceuticl mnufcturing - Mny opportunities to improve tody s prctice through the Theory of Smpling (TOS)., TOS Forum. 4, 5-9 (2015). 2. K. H. Esbensen nd R. J. Romñch, Proper smpling, totl mesurement uncertinty, vriogrphic nlysis & fit-for-purpose cceptnce levels for phrmceuticl mixing monitoring, in Proceedings of the 7th Interntionl Conference on Smpling nd Blending, Issue 5, (2015). doi: /tosf G. Boehm, J. Clrk, J. Dietrick, L. Foust, T. Grci, M. Gvini, L. Gelber, J.-M. Geoffroy, J. Hoblitzell, P. Jimenez, G. Mergen, F. Muzzio, J. Plnchrd, J. Prescott, J. Timmermns nd N. Tkir, The Use of Strtified Smpling of Blend nd Dosge Units to Demonstrte Adequcy of Mix for Powder Blends1, PDA Journl of Phrmceuticl Science nd Technology. 57, (2003). 4. C. V. Liew, A. D. Krnde nd P. W. S. Heng, In-line quntifiction of drug nd excipients in cohesive powder blends by ner infrred spectroscopy, Interntionl Journl of Phrmceutics. 386, (2010) K. A. Bkeev, Process Anlyticl Technology: Spectroscopic Tools nd Implementtion Strtegies for the Chemicl nd Phrmceuticl Industries, Second. Wiley, (2010) 6. K. H. Esbensen nd P. Psch-Mortensen, in Process Anlyticl Technology (John Wiley & Sons, Ltd, 2010) K. H. Esbensen nd L. P. Julius, Representtive Smpling, Dt Qulity, Vlidtion - A Necessry Trinity in Chemometrics, Comprehensive Chemometrics: Chemicl nd Biochemicl Dt Anlysis, Vols 1-4. C1-C20 (2009). 8. H. Mrtens nd T. Nes, Multivrite Clibrtion, Wiley, (1992) 9. M. Popo, S. Romero-Torres, C. Conde nd R. J. Romnch, Blend uniformity nlysis using strem smpling nd ner infrred spectroscopy, AAPS PhrmSciTech. 3, E24 (2002) /pt A. U. Vnrse, M. Alclà, J. I. Jerez Rozo, F. J. Muzzio nd R. J. Romñch, Rel-time monitoring of drug concentrtion in continuous powder mixing process using NIR spectroscopy, Chemicl Engineering Science. 65, (2010). ces Y. Colón, M. Florin, D. Acevedo, R. Méndez nd R. Romñch, Ner Infrred Method Development for Continuous Mnufcturing Blending Process, Journl of Phrmceuticl Innovtion. 9, (2014) /s DS 3077, Dnish Stndrds Foundtion, (2013) 74 Issue

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