The　authors　report　on　a　competitive　potentiometric　immunoassay　for　aflatoxin　B1　(AFB1)　in　food　that　displays　distinctly　improved　sensitivity.　Gold　nanoparticles　(AuNPs;　16 nm　i.　d.)　were　functionalized　with　polyclonal　anti-AFB1　antibody　(pAb),　whilst　the　sensor　electrode　was　prepared　by　immobilizing　AFB1-bovine　serum　albumin　conjugate　(AFB1-BSA)　on　a　glassy　carbon　electrode.　Upon　addition　of　target　AFB1,　competitive　immunobinding　occurs　between　the　analyte　and　AFB1-BSA　for　the　labeled　pAb　on　the　AuNPs.　The　change　in　the　surface　charge　as　a　result　of　the　antigen-antibody　reaction　causes　a　shift　in　the　electrical　potential.　With　increasing　concentrations　of　analyte　(AFB1),　the　quantity　of　pAb-AuNP　captured　by　the　electrode　decreases.　The　shift　in　the　output　potential　is　linearly　proportional　to　the　logarithm　of　AFB1　concentration　in　the　0.1　to　5.0 μg　·　kg−1　range,　with　a　detection　limit　(LOD)　of　87 ng　·　kg−1　(87 ppt).　An　intermediate　precision　of　10.9 %　was　accomplished　in　batch-to-batch　identification.　The　selectivity　over　AFB2　with　similar　chemical　structure　is　acceptable.　The　method　accuracy　was　evaluated　by　analyzing　naturally　contaminated　and　spiked　peanut　samples,　giving　consistent　results　(with　RSD　values　of　<12 %)　between　this　immunoassay　and　the　commercial　ELISA.　[Figure　not　available:　see　fulltext.]　©　2016,　Springer-Verlag　Wien.