diff --git a/microsetta_private_api/admin/admin_impl.py b/microsetta_private_api/admin/admin_impl.py
index 293756121..1369a7f3d 100644
--- a/microsetta_private_api/admin/admin_impl.py
+++ b/microsetta_private_api/admin/admin_impl.py
@@ -543,7 +543,7 @@ def list_barcode_query_fields(token_info):
                 "sample-has-inconsistencies": "Sample Has Inconsistencies",
                 "received-unknown-validity": "Received Unknown Validity"
             },
-            'operators': ['equal', 'not_equal']
+            'operators': ['equal', 'not_equal', 'is_null', 'is_not_null']
         }
     )
     filter_fields.append(
@@ -571,7 +571,26 @@ def list_barcode_query_fields(token_info):
                 "Torso": "Torso",
                 "Vaginal mucus": "Vaginal mucus"
             },
-            'operators': ['equal', 'not_equal']
+            'operators': ['equal', 'not_equal', 'is_null', 'is_not_null']
+        }
+    )
+    filter_fields.append(
+        {
+            # Note that this id string must match the
+            # latest scan timestamp in the exact
+            # barcode search query.
+            'id': 'scan_timestamp_latest',
+            'label': 'Last Scanned',
+            'type': 'date',
+            'description': "YYYY/MM/DD",
+            'default_value': "YYYY/MM/DD",
+            'validation': {
+                "format": "YYYY/MM/DD"
+            },
+            'operators': ['less_or_equal',
+                          'greater_or_equal',
+                          'is_null',
+                          'is_not_null']
         }
     )
 
diff --git a/microsetta_private_api/repo/admin_repo.py b/microsetta_private_api/repo/admin_repo.py
index 26b0aa988..ec55b59f5 100644
--- a/microsetta_private_api/repo/admin_repo.py
+++ b/microsetta_private_api/repo/admin_repo.py
@@ -1119,13 +1119,13 @@ def search_barcode(self, sql_cond, cond_params):
                         "USING (barcode) "
                         "LEFT JOIN ( "
                         "SELECT barcode, max(scan_timestamp) "
-                        "AS scan_timestamp "
+                        "AS scan_timestamp_latest "
                         "FROM barcodes.barcode_scans "
                         "GROUP BY barcode "
                         ") AS latest_scan "
                         "ON barcode_scans.barcode = latest_scan.barcode "
                         "AND barcode_scans.scan_timestamp = "
-                        "latest_scan.scan_timestamp "
+                        "latest_scan.scan_timestamp_latest "
                         "WHERE {cond}"
                 ).format(cond=sql_cond),
                 cond_params
diff --git a/microsetta_private_api/util/query_builder_to_sql.py b/microsetta_private_api/util/query_builder_to_sql.py
index 819fc3a43..c2ec8a79b 100644
--- a/microsetta_private_api/util/query_builder_to_sql.py
+++ b/microsetta_private_api/util/query_builder_to_sql.py
@@ -26,8 +26,8 @@
     # not_ends_with,
     # is_empty,
     # is_not_empty,
-    # is_null,
-    # is_not_null,
+    'is_null': "is null",
+    'is_not_null': "is not null",
 }
 
 
@@ -59,9 +59,14 @@ def build_condition_helper_rule(root_obj, out_values):
 
         if operator not in supported_operators:
             raise RepoException("Unsupported query operator: " + str(operator))
-        cond = "{id} " + supported_operators[operator] + " {value}"
 
-        out_values.append(value)
+        if operator in ["is_null", "is_not_null"]:
+            cond = "{id}" + supported_operators[operator]
+            # no need to append null to out_values
+        else:
+            cond = "{id} " + supported_operators[operator] + " {value}"
+            out_values.append(value)
+
         return sql.SQL(cond).format(
             id=sql.Identifier(id),
             value=sql.Placeholder())