The specimens underwent erosive demineralization by immersion in 1.0% citric acid (pH 3.6, 10 mL/specimen) for 90 seconds, four times a day for five days under constant agitation (70 rpm) (Shaker,
Isolab Laborgerate GmbH, Wertheim, Germany) [18, 26, 27].
Supernatant (5.5 [degrees]L/well) was loaded onto precast, agarose isoelectric focusing (IEF) gels (
Isolab, Akron, OH).
and
Isolab, both members of the Acrolab Group of companies.
To confirm this observation, we compared the Hb [A.sub.2] values obtained by HPLC and anion-exchange microchromatography (Quik-Sep;
Isolab) in nine samples from Hb D heterozygotes.
Subsamples were sent to the laboratory
Isolab (Netherlands) for carbon and hydrogen stable isotope analyses.
Supernatant (5.5 [micro]L/well) was loaded onto precast, agarose isoelectric focusing (IEF) gels (
Isolab, Akron, OH).
For the past 9 years, this laboratory has used isoelectric focusing (IEF;
Isolab) to screen neonates for hemoglobin disorders.
Microcolumn anion-exchange chromatography (MAEC; Quik-Sep[TM] Hemoglobin [A.sub.2] Test System;
Isolab) was used as the comparison method for Hb [A.sub.2] only.
In the cord-blood study Hb types, including Hb Bart's and Hb Constant Spring (Hb CS), were also confirmed by isoelectric focusing (
Isolab).
Recent development of quantitative determination of phenylalanine with the Wallac Quantase phenylalanine screening assay kit [2,3] and the
Isolab phenylalanine test kit has provided other methods for newborn PKU screening.
Erythrocyte lysates were analyzed by starch gel- or cellulose acetate electrophoresis [1] or by isoelectrofocusing [2] with commercial agar plates (
Isolab).