Splitting a Seurat Object HTO classification

Hello,
I am trying to split a Seurat object based on HTO classification. I have 3 different HTO based on different stimulation conditions. I want to pull out the unstimulated condition and make it its own Seurat object. I have tried

Sample_1_unstim<- SplitObject(Sample_1@meta.data$HTO_classification, ident= "Unstim")

And get the error

Error in SplitObject(Sample_1@meta.data$HTO_classification, ident= "Unstim") : 

unused argument (ident = “Unstim”)

However I can see the unstim cells in HTO_classification
I have also tried subsetting the Unstim cells first doing

Sample_1[['Unstim']] = Sample_1[['HTO_classification']][grepl('Unstim',rownames(Sample_1[['HTO_classification']])),]

and got this error

Warning: Invalid name supplied, making object name syntactically valid. New object name is Unstim; see ?make.names for more details on syntax validity

Error: Cannot add more or fewer cell meta.data information without values being named with cell names

Any ideas? Thanks!