Optimizing the culture environment in the IVF laboratory: impact of pH and buffer capacity on gamete and embryo quality  Jason E Swain  Reproductive BioMedicine Online  Volume 21, Issue 1, Pages 6-16 (July 2010) DOI: 10.1016/j.rbmo.2010.03.012 Copyright © 2010 Reproductive Healthcare Ltd. Terms and Conditions

Figure 1 Three phases of pH experienced during in-vitro culture. Reproductive BioMedicine Online 2010 21, 6-16DOI: (10.1016/j.rbmo.2010.03.012) Copyright © 2010 Reproductive Healthcare Ltd. Terms and Conditions

Figure 2 pH of culture media is primarily regulated by a balance of CO2 concentration, supplied by the incubator, and by concentration of bicarbonate in the media. Because bicarbonate concentrations are set by commercial suppliers of media, it is easiest to adjust CO2 concentration in the incubator to adjust pH. Raising CO2 lowers media pH, while lowering CO2 raises the pH. Reproductive BioMedicine Online 2010 21, 6-16DOI: (10.1016/j.rbmo.2010.03.012) Copyright © 2010 Reproductive Healthcare Ltd. Terms and Conditions

Figure 3 Combination of various Good’s buffers allows for the fine-tuning and shifting of pKa values, or optimal buffering capacity, while simultaneously reducing individual buffer concentrations and potential toxicity concerns. Data collected at about 25°C. DIPSO=3-(N,N-bis[2-hydroxyethyl]amino)-2-hydroxypropanesulphonic acid; HEPES=4-(2-hydroxyethyl)-1-piperazineethanesulphonic acid; MOPS=3-(N-morpholino)-propanesulphonic acid. Reproductive BioMedicine Online 2010 21, 6-16DOI: (10.1016/j.rbmo.2010.03.012) Copyright © 2010 Reproductive Healthcare Ltd. Terms and Conditions

Figure 4 Demonstration of the fluctuation and inaccuracy of fyrite as an indicator of pH (adapted from Pool (2004)). Reproductive BioMedicine Online 2010 21, 6-16DOI: (10.1016/j.rbmo.2010.03.012) Copyright © 2010 Reproductive Healthcare Ltd. Terms and Conditions