=====SOP FOR FORMALIN PREPARATION AND BOUIN’S FLUID PREPARATION=====
**1.PURPOSE OF EXAMINATION:** To lay down the procedure for preparation of 10% buffered formalin &Bouin’s fluid for tissue fixation in Histo-pathology section at NCHLS Surat.

**2.PRINCIPLE AND METHOD OF PROCEDURE USED FOR EXAMINATION:** Process by which the constituents of the cells and therefore, of tissues, are fixed in a chemical and partly also in a physical state so that they will withstand subsequent treatment with various reagents with a minimum loss, significant distortion or decomposition and keep the tissue in as life like a manner as possible.  

**3.STAFF RESPONSIBLE:** lab. Technician under supervision of resident doctor/tutor.

**4.PERFORMANCE CHARACTERISTICS:** NA

**5.TYPE OF SAMPLE:** NA

**6.PATIENT PREPARATION:**NA

**7.TYPE OF CONTAINER AND ADDITIVES:** Clean, labeled plastic close container

**8.REQUIRED EQUIPMENT AND REAGENTS:**

**Formalin:** 40% formaldehyde, tap water, K2Hpo4, NaH2po4, 
**Bouin’s fluid:** Picric acid, Formaldehyde, acetic acid.

**9.ENVIRONMENTAL AND SAFETY CONTROLS:**Universal safety precautions

**10.CALIBRATION PROCEDURE ( METROLOGICAL TRACEBILITY):**NA

**11.PROCEDURE(STEPS):**

**A: Buffered Formalin Preparation: (20 liter buffered formalin)**
•	Take 2 liter of 40% formaldehyde solution in one big container

•	Add 18 liter of tap water in container containing 40% formaldehyde.

•	Mix well and add 130 gm K2HPO4 and 80 gm NaH2PO4

•	Mix well till all ingredients have dissolved.

•	Store this solution in closed container for use. 

**B: Bouin’s Fluid: 100 ml	**
•	Take 75 ml picric acid in one beaker.

•	Add 25 ml of 40% Formaldehyde. 

•	Add 5 ml Acetic acid in it.

•	Mix well and store in closed container.	

**12.QUALITY CONTROL PROCEDURE:**NA

**13.INTERFERENCE:** Inadequate quality/improper dilution

**14.PRINCIPLE OF PROCEDURE FOR CALCULATING RESULTS INCLUDING, WHERE RELEVENT, THE MEASUREMENT OF UNCERTAINITY OF MEASURED QUANTITY VALUES:** NA

**15.BIOLOGICAL REFERENCE INTERVALS OR CLINICAL DECISION VALUES OR CLINICAL DECISION VALUES:**NA

**16.REPORTABLE INTERVAL OF EXAMINATION RESULTS:** NA

**17.INSTRUCTION FOR DETERMINING QUANTITATIVE RESULTS WHEN RESULTS IS NOT WITHIN THE MEASUREMENT INTERVAL:**NA

**18.ALERT /CRITICAL VALUES WHERE APPROPRIATE:** NA

**19.LABORATORY CLINICAL INTERPRETATION:**NA

**20.POTENTIAL SOURCE OF VARIATION:** NA

**21.REFERENCE:** Histopathological laboratory techniques by Bancroft, 6th edition