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Determination of a Lower Limit of Para‐Aminobenzoic Acid (PABA) Recovery for Identifying Complete 24‐h Urine Collections by High‐Performance Liquid Chromatography (HPLC)
Author(s) -
Taylor Brittney R.,
SagiKiss Virag,
Freedman Laurence,
O'Brien Diane,
Johnston Carol,
Tasevska Natasha
Publication year - 2017
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.31.1_supplement.955.12
Subject(s) - chromatography , high performance liquid chromatography , urine , detection limit , chemistry , spectrophotometry , biochemistry
Background Para‐aminobenzoic acid (PABA) is a marker commonly used to assess the completeness of 24‐h urine collections in dietary biomarker studies. [1] Spectrophotometry and High‐Performance Liquid Chromatography (HPLC) are the two techniques applied to quantify the percent recovery of orally administered PABA in urine. While the spectrophotometric method uses instrumentation widely available in laboratories, the HPLC method has higher specificity for quantifying PABA. [2] The lower limit of the acceptable recovery of PABA in urine for identifying complete 24‐h urine collections by the spectrophotometric method is 85%, [1] while an agreed limit by the HPLC method is lacking. Methods Under highly controlled conditions, 12 participants took three tablets of potassium aminobenzoate (POTABA) per day containing 240 mg of PABA in total, and collected 24‐h urine samples every other day over a 15‐day period (8 collections in total). Eighteen of 96 24‐h urine collections were excluded due to being identified as incomplete based on the spectrophotometric method (n=3) or self‐report (n=10), invalid HPLC data (n=1), use of medications with similar structure to PABA by participants (n=3), or missed POTABA tablet (n=1). Seventy‐eight 24‐h urine collections were available for analysis, and were measured for PABA using both spectrophotometry and HPLC. The 5 th percentile of the distribution of the PABA percent recoveries was used as the lower limit for accepting complete 24‐h urine collections by the HPLC method. Results The mean ± SD of 24‐h PABA recoveries measured by spectrophotometry was 108.3 ± 11.9% and 259.9 ± 28.6 mg/24‐h urine, ranging from 86 to 134% and 207 to 322 mg/24‐h urine, respectively. The PABA recoveries as measured by the HPLC method were 87.4 ± 8.6 % and 209.7 ± 20.8 mg/24‐h urine, ranging from 72 to 114% and 173 to 274 mg/24‐h urine, respectively. The 5 th percentile of the distribution of the PABA percent recovery in urine by the HPLC was 76% and 181.7 mg/24‐h urine of the orally administered dose. Conclusion As expected, the mean PABA percent recovery in urine by the spectrophotometric method was higher than by the HPLC. Based on the distribution of PABA recoveries determined by the HPLC method in our study population, the lower limit for accepting a 24‐h urine collection as complete was found to be 76% of the orally administered PABA dose, similar to what has been suggested by other authors. [2] Support or Funding Information NCI R01 CA197902