Amniotic fluid phospholipids. Study of the cold acetone precipitation effect

Amniotic fluid phospholipids were extracted and separated with chloroform: methanol (2:1 by vol). These phospholipids were also precipitated with cold acetone and the percentage of each phospholipid precipitated was calculated. The precipitation percentage of the six phospholipids studied ranged from 33.78 +/- 0.70 (mean +/- SEM) for lecithin to 93.77 +/- 1.40 for phosphatidylserine. The variation of L/S, PG/S and PI/S ratios depending on the precipitation step was also studied. We observed that cold acetone precipitation decreased L/S and PG/S ratios, whereas PI/S remained unchanged. Our results indicated that: (1) cold acetone precipitation affected each phospholipid in a different way; (2) the precipitation step was not an effective way of completely separating surfactant and non-surfactant material; (3) a new predictive value should be established if the L/S ratio without precipitation is to be used in the clinic on a daily basis.