Abstract: Reagents and methods for determination of calcium within a sample. Specific embodiments include a reagent for determination of calcium comprising a mono-nitro substituted BAPTA-type chelator (BAPTA=1,2-bis(2-aminophenoxy)ethane-N,N,N?,N?-tetraacetic acid). Methods for accurate determination of calcium in a sample, such as a blood, whole blood, plasma or serum or any other aqueous liquid sample including cerebrospinal fluid, lymph, salivary juice or urine. Embodiments are also useful for clinical diagnoses.

Abstract: The present invention relates to the use of a polar organic solvent for the stabilization of a cholinesterase substrate solution, wherein at least one substrate is stabilized by at least one species of a polar organic solvent in a buffered solution, and to the use of said solution for determining the activity of cholinesterase in a sample. Also within the scope of the present invention is a stabilized cholinesterase substrate solution for determining the activity of a cholinesterase in a sample, wherein at least one substrate is stabilized by at least one species of a polar organic solvent. Furthermore, the invention relates to a method for determining the activity of a cholinesterase in a sample, as well as a kit for determining the activity of a cholinesterase in a sample and a kit for conducting a method for determining the activity of a cholinesterase in a sample.