Objective:
To
determine the uniformity of weight of tablets and capsules.
Introduction:
Uniformity
of Content is a pharmaceutical analysis technique for the quality control of capsules
or tablets. Multiple capsules or tablets are selected at random and a suitable
analytical method is applied to assay the individual content of the active
ingredient in each capsule or tablet. In weight variation test, measurement of
contents is done by estimation of contents based on weight. Pharmacists often
use and misuse this WV test by doing this test on all dosage units. If it is
used correctly, this WV test can be used to measure content uniformity (CU).
There are some conditions in which the weight difference can determine the
percentage difference in the API in the individual dosage units. Hence this WV
test can be useful in the quality control of drug production. This is an
important test in technology of pharmaceutical.
Apparatus
and materials:
Capsules
, tablets , Weighing boats, Weigh balance
Procedures:
Tablets:
Paralgin tablet 500mg
1.
20 tablets were selected randomly and weighed. The average weight was
determined.
2.
The tablets were weighed individually and for each tablet, the percentage
deviation of its weight from the average weight was determined.
3.
The deviation of individual weight from the average weight should not exceed
the limits given below.
Average weight of
tablet
|
Deviation (%)
|
Number of tablets
|
Less than 80 mg
|
±10.0
±20.0
|
Minimum 18
Maximum 2
|
80 mg to 250 mg
|
±7.5
±15.0
|
Minimum 18
Maximum 2
|
More than 250 mg
|
±5.0
±10.0
|
Minimum 18
Maximum 2
|
Capsules:
Ampilin antibiotic capsule 250mg
1.
20 capsules were selected at random.
2.
One capsule was weighed. The capsule was then opened and the contents were
removed as completely as possible. The emptied shells were weighed. The net
weight of its contents was determined, that is by subtracting the weight of the
shells from the weight of the intact capsule.
3.
The procedure was repeated with the other 19 capsules.
4.
The average net weight was determined from the sum of the individual net
weights.
5.
The percentage deviation was determined from the average net weight for each
capsule. The deviation of individual net weight should not exceed the limits
given below.
Average
net weight of capsule
|
Deviation
(%)
|
Number
of tablets
|
Less
than 300 mg
|
±10.0
±20.0
|
Minimum
18
Maximum 2
|
300 mg
or more
|
±7.5
±15.0
|
Minimum
18
Maximum 2
|
Results
And Calculations:
Tablets
No.
|
Individual
weight of tablets (g)
|
Percentage
of deviation (%)
|
1.
|
0.6740
|
-0.43
|
2.
|
0.7038
|
+3.97
|
3.
|
0.6890
|
+1.79
|
4.
|
0.6762
|
-0.10
|
5.
|
0.6820
|
+0.75
|
6.
|
0.6656
|
-1.67
|
7.
|
0.6570
|
-2.94
|
8.
|
0.6726
|
-0.64
|
9.
|
0.6868
|
+1.46
|
10.
|
0.6808
|
+0.58
|
11.
|
0.6853
|
+1.24
|
12.
|
0.6811
|
+0.62
|
13.
|
0.6796
|
+0.40
|
14.
|
0.6712
|
-0.84
|
15.
|
0.6806
|
+0.58
|
16.
|
0.6611
|
-2.33
|
17.
|
0.6573
|
-2.90
|
18.
|
0.6770
|
+0.15
|
19.
|
0.6884
|
+1.70
|
20.
|
0.6684
|
-1.26
|
Results:
Total
weight of 20 tablets = 13.5380 g
Average
weight = 13.5380g/20
= 0.6769 g
**Percentage of deviation = [ (𝑖𝑛𝑑𝑖𝑣𝑖𝑑𝑢𝑎𝑙 𝑤𝑒𝑖𝑔ℎ𝑡)/(𝑎𝑣𝑒𝑟𝑎𝑔𝑒 𝑤𝑒𝑖𝑔ℎ𝑡) x 100] -100
Capsules
No.
|
Individual
weight of capsules (g)
|
Weight
of emptied shells (g)
|
Net
weight of the contents (g)
|
Percentage
deviation (%)
|
1.
|
0.3510
|
0.0606
|
0.2904
|
+3.74
|
2.
|
0.3537
|
0.0641
|
0.2896
|
+3.47
|
3.
|
0.3543
|
0.0629
|
0.2914
|
+4.11
|
4.
|
0.3646
|
0.0625
|
0.3021
|
+7.93
|
5.
|
0.3531
|
0.0590
|
0.2941
|
+5.07
|
6.
|
0.3592
|
0.0614
|
0.2978
|
+6.40
|
7.
|
0.3631
|
0.0631
|
0.3000
|
+7.18
|
8.
|
0.3570
|
0.0631
|
0.2879
|
+2.86
|
9.
|
0.3628
|
0.0675
|
0.2953
|
+5.50
|
10.
|
0.3516
|
0.0617
|
0.2899
|
+3.57
|
11.
|
0.3667
|
0.0654
|
0.3013
|
+7.65
|
12.
|
0.3393
|
0.0617
|
0.2776
|
-0.82
|
13.
|
0.3596
|
0.0624
|
0.2972
|
+6.18
|
14.
|
0.3479
|
0.0625
|
0.2854
|
+1.97
|
15.
|
0.3642
|
0.0590
|
0.3052
|
+9.04
|
16.
|
0.3504
|
0.0630
|
0.2874
|
+2.68
|
17.
|
0.3652
|
0.0619
|
0.2973
|
+6.22
|
18.
|
0.3520
|
0.0618
|
0.2902
|
+3.68
|
19.
|
0.3630
|
0.0613
|
0.3017
|
+7.79
|
20.
|
0.3595
|
0.0648
|
0.2947
|
+5.29
|
Total
net weight of the content of 20 capsules = 5.5989 g
Average
net weight = 5.5989/20
= 0.2800 g
Discussion:
For
tablets, since our average weight is
676.9 mg, the deviation of individual net weight should not exceed the limits
given below:
More
than 250 mg
|
±5.0
±10.0
|
Minimum
18
Maximum
2
|
From
the results, we can see that the all the tablets are having standard deviation
of ± 5.0. This is shows that 20 tablets having this type of deviation. This may
indicate the uniformity of the capsules production.
However,
the variation in the weight of the tablets may be explained by the following.
Factors such as the flowing properties of the powder, the speed of tableting
machine, the pressure used in compression and the type of machines used in
tableting may affect the weight of a tablet. However the two most common causes
of weight variation are the differences in the bulk densities and particle size
distribution during compression
For
capsules, since our average weight
is 280.0 mg, the deviation of individual net weight should not exceed the
limits given below:
Less
than 300 mg
|
±10.0
±20.0
|
Minimum
18
Maximum
2
|
From
the results, all our capsules are having a deviation of ± 10%, which means that
all capsules have uniform weights. This may indicate the uniformity of the
capsules production. At the same time, this uniformity may also be caused by
the usage of a good weighing balance. The weighing balance used for measuring
the weight of capsule is more accurate as it is a more advanced balance.
If
the weight variation in capsule exceeds the limit, this may be due to the
defect of the capsule filling machine. The machine may have misalignment of the
upper and lower capsule segments or problem in filling the capsule with the
target fill weight.
Conclusion:
Both
tablets and capsules tested have passed the test of weight uniformity. This
uniformity may also be caused by the usage of a good weighing balance. The
weighing balance used for measuring the weight of capsule is more accurate as
it is a more advanced balance.
References:
2.
Donald K. Lightfoot. (n.d.) Answers To 10 Common Questions About Capsule
Filling. Retrieved date. 21st December 2013.
From http://capsugel.com/media/library/answers-to-10-common-questions-about-capsule-filling.pdf
3. Dshravani. (2013) Citing Websites. Quality
Control Of Capsules. Retrieved date. 21st December 2013. From http://www.pharmainfo.net/quality-control-capsules
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