Sampling is the process of obtaining a representative sample of a bulk material that cannot be analyzed as a whole. There are two types of samples - homogeneous samples, like blood or urine, which can be analyzed directly, and heterogeneous samples, like shipments of grains, which require taking small samples from various locations and combining them. A gross sample consists of portions from various locations that are combined to make a homogeneous laboratory sample, from which a small analysis sample is taken for testing. Different techniques are used for sampling solids like grains or powders compared to liquids like blood or urine, with the timing and methods of collection being important for biological samples.

1. SAMPLING
 SAMPLING IS THE PROCESS OF OBTAINING A REPRESENTATIVE SAMPLE
(WE CANNOT ANALYZE THE WHOLE THING!) • A SAMPLE IS THE
REPRESENTATIVE OF THE WHOLE BULK.

2.  Sample May be Homogeneous or
Heterogeneous
 HOMOGENOUS SAMPLE:
 A GRAB SAMPLE IS OFTEN OK. FOR INSTANCE, IN CLINICAL LAB,
GROSS SAMPLE (BLOOD, URINE) CAN BE ANALYZED DIRECTLY AS IT IS
HOMOGENOUS.

3.  HETEROGENEOUS SAMPLE
 SEVERAL INDIVIDUAL SAMPLES ARE TAKEN. E.G., ANALYZING AVERAGE PROTEIN CONTENT OF
SHIPMENT OF GRAINS, ONE HAS TO COLLECT LITTLE GRAIN FROM EACH BAG DURING
LOADING/UNLOADING USING A SAMPLING SPEAR (SACK SAMPLER) AND COMBINE TO OBTAIN A
GROSS SAMPLE.

4. Gross Sample
 CONSISTS OF SEVERAL PORTION OF THE MATERIAL TO BE TESTED
LABORATORY SAMPLE CONSISTS OF A SMALL PORTION OF GROSS SAMPLE
MADE HOMOGENOUS ANALYSIS SAMPLE IS THAT WHICH IS ACTUALLY
ANALYZED GROSS SAMPLE LABORATORY SAMPLE ANALYSIS SAMPLE (FEW
G TO KG) BULK OF MATERIAL (FEW G) (A DROP, FEW MG, FEW ML)

5.  GRAB SAMPLE

6.  Sampling From Bags
 SIMPLE BAG SAMPLING SPEARS (SACK SAMPLERS) ARE MOST COMMONLY
USED FOR TAKING SAMPLES FROM BAGS BECAUSE THEY ARE RELATIVELY
CHEAP AND SAMPLE QUICKLY. TO OBTAIN A GOOD CROSS SECTION OF
SAMPLE, THE SPEAR SHOULD BE 40 TO 45 CM IN LENGTH. TAPERED TYPE OF
SAMPLING SPEARS PENETRATES BAGS EASILY.

7.  Sampling of powder:
 SMALL PARTICULATE MATERIALS SUCH AS POWDER ARE BEST
COLLECTED WITH A SAMPLE THIEF. SAMPLE THIEF ALLOW MATERIAL
TO BE COLLECTED SIMULTANEOUSLY FROM SEVERAL LOCATIONS.

8.  Biological Fluids:
TIMING FOR BIOLOGICAL SAMPLES IS IMPORTANT. E.G., BLOOD COMPOSITION
CHANGES BEFORE AND AFTER MEAL. SAMPLING AFTER 12H FASTING IS OFTEN
RECOMMENDED. 24H URINE COLLECTION IS BETTER THAN A SINGLE
SPECIMEN. IN CASE OF BLOOD, A GRAB SAMPLE IS OK. SYRINGES ARE USED TO
COLLECT BLOOD SAMPLES. GLASS OR PLASTIC WITH STAINLESS STEEL
NEEDLE ARE AVAILABLE.