The total organic carbon (TOC) test is a fast and effective analytical technique to evaluate the cleaning of biopharmaceutical manufacturing equipment. This technique can help ensure that the cleaning processes meet predetermined cleanability criteria for single and multiproduct production areas. This article presents a case study describing the use of the TOC test to validate the cleaning processes used for two types of biomanufacturing equipment.
MATERIALS AND METHODS
MATERIALS Biological Samples
The cells and proteins used in the swabbing recovery study included Escherichia coli bacterial cells, Saccharomyces cerevisiae yeast cells, recombinant streptokinase (SK), recombinant epidermal growth factor (EGF), recombinant human alpha interferon (IFNα), and pegylated recombinant human alpha interferon (IFNα–PEG).
TOC Vials and Swabs
Glass 40-mL autosampler vials with caps were used for TOC measurements. For the recovery study a TX3340 TOC cleaning validation kit, containing 12 Eagle Picher 03464 40-mL clear vials, 24 Texwipe TX714K large SnapSwabs, and 12 blank vial labels was used. The 40-mL vials were certified as having TOC levels <10 ppb and the TOC levels of the swabs were certified at <50 ppb.
METHODS TOC Measurement Method Validation
The TOC test involves full oxidation of organic carbon and detection of the resulting CO2. In this study, a TOC analyzer equipped with an auto-sampler was used. The analyzer measures TOC according to ASTM method D6317.8 It determines the amount of total carbon (TC), inorganic carbon (IC), and TOC in water in the range of 10 to 1,000 μg/L. The test method used persulfate and ultraviolet (UV) oxidation of organic carbon, coupled with a CO2 selective membrane to recover the CO2 in deionized water. The change in conductivity of the deionized water was measured and compared with the carbon concentration in the oxidized sample. IC was determined in a similar manner, but without the oxidation step. In both cases, the sample was acidified to facilitate CO2 recovery through the membrane.
The relationship between the conductivity measurement and carbon concentration is described by a set of chemometric equations for the chemical equilibrium of CO2, HCO3–, and H+, and for the relationship between the ionic concentrations and conductivity. The chemometric model includes the temperature dependence of the equilibrium constants and the specific conductance, resulting in a linear response of the method over the stated range of TOC.
in which Σ is the sum of each result and n is the number of measurements in a set (number of replicates – number of rejections). The RSD = (SD/measured TOC concentration) x 100.