Based on the provided sources, it is unclear whether the Humira biosimilars are citrate-free. The sources do not explicitly mention whether the biosimilars of Humira contain citrate or not. To obtain accurate information regarding the citrate content in Humira biosimilars, it is recommended to consult the specific product labeling or contact the manufacturers directly for detailed information.

Sources:
[1] Drug Patent Watch: https://www.drugpatentwatch.com/p/biologics/tradename/HUMIRA
[2] NCBI: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8014989/
[3] Cardinal Health: https://www.cardinalhealth.com/en/product-solutions/pharmaceutical-products/biosimilars/humira-biosimilar-landscape-overview.html