Introduction
The United States Pharmacopoeia has established guidelines for determining system suitability and established the acceptance of Water For Injection (WFI) purposes and Purified Water (PW) (USP Method <643>).
Shimadzu’s TOC-LC*H analyzer is perfectly adapted to meet the requirements of USP Method <643>. The TOC-LC*H analyzer utilizes 680°C heat and platinum catalyst to provide a lower maintenance instrument with a detection limit of 0.0040 mg per liter.
USP <643>
In the system suitability test, the response from a solution of sucrose, a relatively easily oxidized compound, is compared to the response from 1,4 benzoquinone, a more difficult compound to oxidize. The response of the reagent water is subtracted from each response to yield a corrected response.
The requirement for passing the system suitability test is to obtain results for the control standard (1,4 BQ) minus the reagent water that are within +/- 15% of the sucrose standard minus the reagent water as shown in equation 1.
%R = [(rss-rw) / (rs-rw)] * 100 (equation 1)
Table 1 - Key to equation 1
Samples are acceptable for Purified Water (PW) or Water For Injection (WFI) if equation 2 is satisfied.
(Sample Area Counts) ≤ (rs-rw) (equation 2)
Procedure
First 25.0 mg of glucose was accurately weighed out and brought to 100 mL with purified water; this yields a 100 mg per liter carbon solution. 0.5 mL of this solution was then diluted to 100 mL yielding a 0.5 mg per liter carbon solution. This was used as the high standard for calibration.
Standard Analysis
Prepared System Suitability Standards were purchased from Shimadzu (PN 220-95282- 00). The standards were analyzed on the Shimadzu TOC-LC*H. The instrument parameters are shown in Table 2.
Table 2 - Parameters
Standard Results
Table 3 - Results
System Suitability
%R = [(rss-rw) / (rs-rw)] * 100 (equation 1)
%R = [(43.63-8.51) / (43.50-8.51)] * 100 = 100.4 % (equation 3)
Conclusion
According to the requirements outlined by USP, the Shimadzu TOC-LC*H is suitable for the analysis of Purified Water and Water For Injection. 1,4-Benzoquinone is more difficult to oxidize than sucrose, therefore it is used as a system suitability solution. As shown in table 3 the area counts are very similar, and the recovery was 100.4%, validating the instrument’s ability to accurately measure TOC in the ranges of 0.5000 mg per liter TOC.