Mercaptosuccinic Acid from Mexico
Mercaptosuccinic acid (thiomalic acid) contains both mercapto and dicarboxylic acid functions in a single molecule. Falls under HTS 2930.90.4920 as 'other mercaptocarboxylic acids' since organo-sulfur takes precedence over oxygen functions per Chapter 29 classification rules. Used in heavy metal detoxification.
Duty Rate — Mexico → United States
100%
Rate breakdown
9903.04.6095.8%Pharmaceuticals Annex IV: patented pharma articles — 100% floor rate
9903.05.900%Articles already subject to Section 232 (steel/aluminum/copper + derivatives, autos + parts, wood, medium/heavy vehicles + parts, semiconductors, patented pharma) — U.S. note 52(f)
Import Tips
• Provide quantitative analysis showing free -SH and -COOH groups for dual-function classification
• Classify as UN 3265 Corrosive solid, pH <2 requires specific packaging
• Document research/pharma end-use to avoid 2917 polycarboxylic acid misclassification