Consider the electrophoresis of heparin in Figure 25-21.
(a) Electrophoresis was carried out at pH 2.8, at which sulfate groups are negative. Why was reverse polarity (detector end positive) used?
(b) The ionic strength of 30 mg/mL heparin samples is higher than that of typical samples for electrophoresis. What is the benefit of high buffer concentration (0.6 M phosphate)?
(c) A narrow capillary (25 μm diameter) was chosen to be compatible with the high-ionic strength buffer. What is the advantage of the narrow capillary?
(d) Li+ has lower mobility than Na. Explain why lithium phosphate can be used at higher electric field strength than sodium phosphate to generate the same current. What is the advantage of higher field strength for this separation?