WHAT TYPE OF INTERPOLATION TOOL TO USE FOR 26 LOCATIONS THAT HAVE METAL CONCENTRATION

[AsifZaman1]

I have data of 26 sampling stations along a coast. At each of the 26 sampling stations, metal concentrations of various metals were taken measured in (ug).  So far, I uploaded the points of the 26 stations and converted to shapefile with relevant information. I have the base map as well. My goal is to use some sort of interpolation tool to show the different concentration of the metal between the 26 stations. 
Question: What type of interpolation tool should I use?  Or is there another tool to use in arcmap?
And is it possible to the 26 points )sampling  stations showing their relation of all types of metal concentration on one map?

[MarcoBoeringa]

I am afraid that the answer may end up being "none", but maybe some of the ESRI folks active here in the Forums, can point you in another direction.

26 stations, stretched along a corridor beside the coast, is a far from ideal situation for the interpolation methods in ArcGIS, that usually assume or require some sort of basic 2D distribution of sample points, instead of just measurements stretched along a 1D coast line.

Your sample, with just 26 points, is also very small. An advanced interpolation method like Kriging, and the necessary semivariogram estimation it involves, as implemented in for example Geostatistical Analyst, usually requires at least some 50-100 sample points to create a reliable semivariogram, and thus reliable interpolation. See for example this post I made in another thread, for some more background to this.

There may be specialized interpolation routines for "line" type interpolation along something like a coast (or things like oil well bore holes), but I can't point you to one right now. Google if necessary.

Another option though, might be to convert the coast line to a Linear Referencing "Route", and assign the 26 stations as M values to the route at the appropriate sample station location. You could than have ArcGIS estimate a value for you by selecting a point along the line, and have ArcGIS do a linear interpolation between the two most nearby stations to estimate the value at that particular point along the line.

See:
What is linear referencing?
and
Dynamic Segmentation

[DanPatterson_Retired]

use projected data and determine whether there is any pattern plotted as a function of distance between the points.  Are you looking for a trend?  is there an expected pattern?  Interpolation, as pointed out is not going to work if you have a linear pattern of points, perhaps a simple map showing the concentrations via symbology might work.