Submitted to: Journal of Chromatography
Publication Type: Peer reviewed journal
Publication Acceptance Date: 11/19/2002
Publication Date: 5/20/2003
Citation: GEHRING, A.G., BAILEY, D.G., CAVENG, R.F., VREELAND, R.H. A RAPID METHOD FOR THE ESTIMATION OF BILE SALTS IN COMPLEX TANNING BRINES BY RPHPLC. JOURNAL OF LIQUID CHROMATOGRAPHY & RELATED TECHNOLOGIES. 2003. VOL. 26, NO. 7, p. 1041-1050. Interpretive Summary: Cowhides that are used to make leather are customarily preserved with salt (in large vats of brine solution) in order to prevent decomposition of the hides by bacteria and other microorganisms. Such preservation is required for the short-term storage of hides prior to processing in a tannery. However, this method of preservation is not effective if there is a particular species of "salt-loving" bacteria present. This microorganism can survive in high amounts of salt and, under certain conditions, subsequently damage hides. Hence, poor quality, and therefore low value leather is obtained from those hides. We are testing the effectiveness of a particular chemical, a safe by-product of the meat packing industry, that prevents the growth of these salt-loving bacteria in the brine. Since some of the chemical remains on hides removed from the brine vats, it is desirable to monitor the depletion of this chemical from the brine so that more may be added when necessary in order to achieve an effectively optima amount. In response to this need, we have developed a relatively simple and quick method using high pressure liquid chromatography that remarkably measures the amount of this chemical in brine solutions that are highly contaminated with substances (bacteria, blood, dirt, fats, hair, manure, urine) normally associated with cowhides. The intent of our research is to provide the US industry with a means to prevent this damage and to achieve superior hide preservation.
Technical Abstract: To preserve bovine hides until they are processed into leather, they are often cured in large raceways of saturated brine. This process prevents the growth of most microorganisms, but under some conditions, these hides are still susceptible to decomposition by halophilic archaebacteria. Low amounts of porcine bile added to the brine used for curing, have exhibited control of growth of these primitive microorganisms. Reversed-phase high pressure liquid chromatography has been applied to monitor bile concentration in saturated brine mixtures containing contaminants associated with animal hides (bacteria, blood, dirt, fats, hair, manure, urine, etc.). With minimal sample preparation, this method can be used by either the hide curing, packing, or tanning industry to assess the need to charge brine solutions with additional porcine bile during the continuous process of hide addition and removal. Calibration curves of porcine bile added to highly contaminated raceway brine have demonstrated linearity of detection between 25-340 ppm bile. The method of standard addition was used to identify and quantify a porcine bile component, glycochenodeoxycholic acid. HPLC was also used to determine the relative solubility of porcine versus bovine bile in solutions of varying salt concentration.