Fill quan­tity con­trol with an X‑ray vision

When filling highly potent pow­ders for inhala­tion pur­poses, tiny amounts of active sub­stances have to be dosed with pre­ci­sion. Harro Höfliger, always metic­u­lous, is now also using X‑ray tech­nology for ver­i­fying the quan­tity of powder filled in blister strips. The use of the X‑ray module enables 100 per­cent ver­i­fi­ca­tion of the dosed mass –fully auto­matic, in-line and in a closed container.

Normally, the ver­i­fi­ca­tion of powder filled blis­ters is done by means of destruc­tive random sam­pling: An alu­minum strip is removed from the process and opened in a sep­a­rate test unit. If the net weight of the weighed dry powder devi­ates from the defined set value, the dosing process must be re-adjusted and the random test repeated after­wards. This may result in pro­duc­tion losses and delayed batch releases.

When such OOS inci­dents (Out Of Spec­i­fi­ca­tion) happen, short reac­tion times are cru­cial for phar­ma­cists. Harro Höfliger there­fore now offers an inte­grated X‑ray module for con­tin­uous quality con­trol in their blister machines with mem­brane filling tech­nology. An X‑ray beam pen­e­trates the sealed powder cavity and strikes a flat panel detector, con­verting the inten­sity dis­tri­b­u­tion into a dig­ital image with a range of gray-scale gra­da­tions. Light and dark colors cor­re­late with the respec­tive amount of radi­a­tion energy absorbed by powder and alu­minum film.

Com­pact and safe inte­gra­tion of the X‑ray module in the Blister Machine SSP2. Con­ve­nient oper­ator con­trol via the HMi oper­ator panel.

If the absorp­tion rate of the empty blister strip and the powder mass are known in the ref­er­ence pat­tern, the soft­ware sets the gray value in rela­tion to it. That way the system can be cal­i­brated. For every new product with a dif­ferent com­po­si­tion, the cor­re­la­tion value of fill quan­tity and gray value is deter­mined and the system cal­i­brated again. The powder mass is ver­i­fied by Harro Höfliger’s IPC-check­weigher for blister strips. After pro­gram­ming the new coor­di­nates, a fill quan­tity con­trol with auto­matic trend con­trol for the com­plete batch dura­tion is pos­sible. At the same time, seam­less data recording facil­i­tates a smooth batch release.

(Photo: Helmar Lünig)

The system reli­ably ver­i­fies fill quan­ti­ties down to 5 mil­ligrams and without changing machine speed. On the model SSP2 blister machine for small series, 60 to 80 cav­i­ties per cycle are inspected, at up to 15 cycles per minute. The min­imal radi­a­tion inten­sity has no impact on the active phar­ma­ceu­tical ingre­dient or the operator’s health. The new X‑ray tech­nology will not only be used in future blister machines, but existing machines can also be retro­fitted. Another plus: The system detects damage to the alu­minum blister and detects for­eign par­ti­cles in the powder cavities.

X‑ray — This is how it works

Whether used for lug­gage con­trol or at the doctor’s office: X‑ray images are prac­ti­cally a part of everyday life. Inspec­tions and screen­ings ben­efit from the fact that the absorp­tion of X‑rays passing through matter varies. More or less atten­u­ated, they then strike an X‑ray film or a modern detec­tion system, which con­verts the infor­ma­tion into a dig­ital image. The gray scales reflect the degree of absorp­tion. Thus, our radi­olu­cent mus­cles appear almost black, and the robust bones white. In addi­tion to mate­rial den­sity, atten­u­a­tion also depends on the atomic number in the peri­odic table: Due to their higher number of elec­trons (alu­minum: 13, iron: 26), metals absorb less radi­a­tion energy than organic sub­stances (carbon: 6). A mea­sure of atten­u­a­tion is the gray-scale value. The higher it is the more rays are reg­is­tered by the detector.

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Photos: Helmar Lünig