Claims:We claim: 1. An improved process for the preparation of Losartan having the formula (1), and its salts wherein the process comprises of: (i) reacting 2-N-butyl-4-chloro-5-formyl imidazole with 4'-(Bromomethyl)-2-cyanobiphenyl in the presence of a phase transfer catalyst to produce a cyano aldehyde, (ii) reducing the formed cyano aldehyde with a reducing agent to produce a cyano alcohol, (iii) treating the formed cyano alcohol with sodium azide and triethyl amine hydrochloride in a polar aprotic solvent to produce Losartan, (iv) Losartan is further treated with potassium hydroxide or sodium hydroxide in presence of organic solvent selected from alcohols or ketones or ethers or combinations thereof to yield the respective salts of Losartan. 2. An improved process for the preparation of Losartan having the formula (1) and its salts, wherein the process comprises of: (i) reacting 2-N-butyl-4-chloro-5-formyl imidazole with 4'-(Bromomethyl)-2-cyanobiphenyl in the presence of a phase transfer catalyst to produce a cyano aldehyde, (ii) reducing the formed cyano aldehyde with a reducing agent to produce a cyano alcohol, (iii) treating the formed cyano alcohol with sodium azide and triethyl amine hydrochloride in a polar aprotic solvent to produce Losartan, (iv) Losartan is further treated with potassium hydroxide or sodium hydroxide in presence of organic solvent selected from alcohols such as methanol, ethanol, n-propranolol or combinations thereof and/or from ketones such as acetone and ethers such as diethyl ether. 3. An improved process for the preparation of Losartan having the formula (1) and its salts, wherein the process comprises of: (i) reacting 2-N-butyl-4-chloro-5-formyl imidazole with 4'-(Bromomethyl)-2-cyanobiphenyl in the presence of a phase transfer catalyst to produce a cyano aldehyde, (ii) reducing the formed cyano aldehyde with a reducing agent to produce a cyano alcohol, (iii) treating the formed cyano alcohol with sodium azide and triethyl amine hydrochloride in a polar aprotic solvent to produce Losartan, (iv) Losartan is further treated with potassium hydroxide or sodium hydroxide in presence of organic solvent selected from alcohols such as methanol, ethanol, n-propranolol or combinations thereof and/or from ketones such as acetone and ethers such as diethyl ether, Wherein the said process contains n-nitrosamines selected from N-Nitrosodimethylamine (NDMA), N-Nitrosodiethylamine (NDEA), N-Nitroso-N-Methyl 4-amino butyric acid (NMBA) or combinations thereof and found to be below level of detection (85%). Step 3: Preparation of (1- ( (2'- (1H-tetrazol-5-yl) biphenyl-4-yl) methyl) -2-butyl- 4-chloro- 1H-imidazol-5-yl)methanol Potassium [Losartan] Potassium salt of Losartan formula (2): To a stirred solution of (1-((2'-(1H-tetrazol-5-yl)biphenyl-4-yl)methyl)-2-butyl-4-chloro-1H-imidazol-5-yl)methanol (Losartan I) obtained by the process described in step 2 in (3.5 - 4 volumes) of methanol and stirred at room temperature (25-35°C) pH was adjusted to 9.0-9.5 with potassium hydroxide (1.15-1.2 mole eq.) and stirred for 30 mins. The reaction temperature was raised to 40-45°C and reflux maintained for 4-5 h, the reaction mixture was cooled to 35-40°C; activated carbon was added and filtered through hyflow bed. The clarified solution was concentrated by vacuum to remove most of methanol at 45-50°C under reduced pressure. The residue was dissolved in acetone (3.5 - 4 volumes) and heated to 55-60°C, the solvent was vacuumed to yield a mass that was cooled to 25-35°C, washed with acetone (2 volumes) and maintained at 0-5°C for 1-2 h, the final mass was washed with acetone and dried at 60-65°C to yield Losartan Potassium of the formula II. (Yield: >87.15%). Methodology for NDMA & NDEA: Objective: To summarize the analytical method validation report for the estimation of N­ Nitrosodimethylamine (NDMA) and N-Nitrosodiethylamine (NDEA) content in Losartan Potassium by GC-MS. Description of method: 1. Diluent: Dimethyl Sulfoxide (DMSO) 2. Sample details: Losartan Potassium Batch numbers: LP 1903007, LP l903008, LP 1903010, LP 1903011, LP 1903012 & LP 1903013 3. Reference Standards and their Specification Limit: a. N-Nitrosodimethylamine (NDMA): NMT 0.64ppm b. N-Nitrosodiethylamine (NDEA): NMT 0.177ppm 4. Instruments: GCMSHS Shimadzu Analytical Balance Radwag 5. Instrument Parameters & Chromatographic Conditions: GCMS system GCMSHS Column DB-WAX, 30m x 0.25 mm, 0.5µm or Equivalent Column Flow 3.0 mL/min Carrier gas Helium Oven Program Rate (°C/min) Temperature (°C) Hold time in mm - 70 4.0 20 240 3.5 Run time 16.0min Injection Mode Split Split ratio 5:1 Sample concentration 500mg/mL Diluent DMSO Head space parameter Oven temperature 120°C Sample line temperature 125°C Tr. line temperature 130°C Shaking level 5 GC Cycle time 23min Vial Equilibrating time 15min Needle flush time l0min Inject time l.0min Pressurizing gas pressure 15psi MS parameters MS source Temperature 230°C Interface Temperature 240°C Solvent delay 4.0 min Detector Off 9.0 min Acq Mode SIM Ch-1 m/z 74 (NDMA) Ch-2 m/z 102 (NDEA) 6. Preparation of Solutions: Diluent: Dimethyl Sulfoxide (DMSO) Preparation of Blank: Transfer l.0 mL of DMSO into a Head space vial and immediately cap and crimp the vial. NDMA Standard Stock Solution (SS-1) (25.60 ppm w.r.t. sample): Accurately weigh and transfer 20mg of N-Nitrosodimethylamine (NDMA) standard into 20mL volumetric flask dissolve and dilute to volume with diluent and mix well. Further, dilute 0.64mL of above solution in 50mL volumetric flask, dissolve and dilute to the mark with diluent and mix well. (Or) Transfer l.0 mL of the commercially available NDMA solution (CAS No: 62-75-9, 5000µg/mL) into l0 mL volumetric flask containing 3 mL of Methanol and make up to volume with methanol and labeled as stock solution. (As such concentration of the standard stock solution is 500ppm). Further, transfer 1.28mL of above standard in to 50mL volumetric flask and make up to volume with diluent. NDEA Standard Stock Solution (SS-2) (7.08ppm w.r.t sample): Accurately weigh and transfer 20mg of N-Nitrosodiethylamine (NDEA) standard into 20mL volumetric flask dissolve and dilute to volume with diluent mix well. Transfer 0.l77 mL of the above Solution into 50mL volumetric flask and makeup to the volume with diluent and mix well. Standard Solution (0.64ppm of NDMA and 0.177ppm of NDEA w.r.t sample) Transfer l .25mL of the NDMA Standard Stock Solution (SS-1) and NDEA Standard Stock Solution (SS-2) into 50ml volumetric flask and makeup to the volume with diluent and mix well. Transfer 1.0mL of standard solution into 20mL individual Headspace vials and seal the vial immediately with PTFE septa. Test Sample Solution Accurately weigh and transfer 500mg of test sample into a 20mL Head space vial and add 1.0mL of diluent and seal the vial immediately with PTFE septa. 7. Procedure Equilibrate the column at 220°C for 20 min and then cool to initial temperature. Inject blank and record the chromatogram. If required inject additional blank to stabilize the baseline. Inject standard solution for six times and record the chromatograms. Check the system suitability criteria, if met the requirement, proceed further Batch Sequence: S. No. Sample ID Number of injections 1 Blank 01 2 Standard solution 06 3 Blank 01 4 Test sample 01 5 Bracketing standard 01 Evaluation of System suitability Calculate the % RSD for the area of NDMA & NDEA from the six replicate determinations should be NMT 20.0. Calculate the cumulative %RSD for the area of NDMA and NDEA from initial six injections and bracketing standard should NMT 25.0. Methodology for NMBA: Objective: To summarize the analytical method validation report for the estimation of N-Nitroso-N-Methyl 4-amino butyric acid (NMBA) in Losartan Potassium by LC-MS. Description of method: 1. Solvents and Diluent: Acetonitrile, Formic Acid and Milli-Q-Water 2. Sample details: Losartan Potassium Batch numbers: LP 1903007, LP l903008, LP 1903010, LP 1903011, LP 1903012 & LP 1903013 3. Reference Standards and their Specification Limit: a. l-Phenylethane-1-amine-4-(methyl(nitroso)amino)butanoate (NMBA.PEA Salt) b. (N-Nitroso-N-Methyl 4-amino butyric acid (NMBA)): NMT 0.64 ppm 4. Instruments: LC-MS/MS Shimadzu Analytical Balance LC-GC Analytical Balance LC-GC Micropipette Thermo 5. Chromatographic Instrument Parameters & Chromatographic Conditions for NMBA: LCMS/MS Make: Sbimadzu Model:8045 Column Develosil C8 UG- 5, 150 x 4.6 mm, 5.0 µm (or) Equivalent Flow rate 0.7 mL/tnin Column temperature 35°C Auto Sampler Temperature 5°C Injection Volume 25 µL Run time 20 Minutes Detection MS Rinsing Solvent Water: Acetonitrile (80:20) Elution mode Gradient MS Parameters Compound NMBA (N-Nitroso N-methyl 4-amino butyric acid) Ionization source ESI Acquisition mode SIM SIM (rn/z) 145.10 [M-H]" Polarity Negative Dwell time 100ms Nebulizer gas flow 3.0 L/min Heating gas flow 10.0 L/min Drying gas flow 10.0 L/min Interface temperature 350°C Heat block temperature 400°C DL temperature 300°C Note: Mass parameters can be adjusted based on the mass tuning of the analyte. 6. Preparation of Solutions: Diluent: Use Milli-Q-Water Preparation of Blank: Use Diluent as Blank Preparation of Buffer: 0.1 % Formic acid in water. Filter and degassing through 0.22µm membrane filter paper. Preparation of Mobile Phase-A: Use buffer solution. Preparation of Mobile Phase-B: Use Acetonitrile solution. Preparation of NMBA Standard stock solution (63.8 ppm w.r.t sample): Accurately weigh and transfer about 9.14 mg of NMBA PEA Standard (equivalent to 5 mg of NMBA) in to 100 mL volumetric flask, dissolve and dilute to volume with diluent and mix well. Transfer 6.0 mL of above solution into a 100 mL volumetric flask and dilute to volume with diluent and mix well. Preparation of NMBA Standard solution (0.64 ppm w.r.t sample): Transfer 1.0 mL of the above standard stock solution into a 100 mL volumetric flask and dilute to volume with diluent and mix well. Preparation of Test Solution: Accurately weigh and transfer about 470.0 mg of test sample into a 10 mL volumetric flask, dissolve and dilute to volume with diluent and mix well. 7. Procedure: Equilibrate the column for at least 20 minutes. Inject blank and standard solution into the system and record the chromatogram. Batch Sequence S. No. Sample ID Number of injections 1 Blank 02 2 Standard solution 06 3 Blank 01 4 Blank 01 5 Test Solution 01 6 Bracketing standard 01 Evaluation of System suitability % RSD calculated for the peak areas of NMBA from six injections of standard solution should be not more than 20.0. Calculation: NDMA content (ppm) = AT-AB x CS x P x 10000 AS-AB CT AT = Area of NDMA in test solution AB = Area response of peak in the chromatogram of the respective blank. AS = Average Area of NDMA peak in the standard solution CS = Concentration of NDMA in the standard solution (mg/mL) CT = Concentration of test solution (mg/mL) P = Purity/Assay/Potency of NDMA standard (%) Note: Similarly the content of NDEA and NMBA is also calculated Batch Analysis Results Sample Batch Number N-Nitrosodimethylamine content (ppm) NMT 0.177 N-Nitrosodiethylamine content (ppm) NMT 0.64 N-Nitroso-N-Methyl 4-amino butyric acid content (ppm) NMT 0.64 ppm LP 1903007 Not detected Not detected Not detected LP l903008 Not detected Not detected Not detected LP 1903009 Not detected Not detected Not detected LP 1903010 Not detected Not detected Not detected LP 1903011 Not detected Not detected Not detected LP 1903012 Not detected Not detected Not detected LP 1903013 Not detected Not detected Not detected Conclusion: The test method for Estimation of N-Nitrosodimethylamine (NDMA) content (ppm), N-Nitrosodiethylamine (NDEA) content (ppm), N-Nitroso-N-Methyl 4-amino butyric acid content (ppm) (NMBA) in Losartan Potassium has been developed. The parameters performed (system suitability, LOD & LOQ Precision, Linearity, Method Precision, Accuracy (LOQ and 100% Level) and Batch analysis) are within the acceptable limit and batch analysis results found to be below LOD level. Advantages of the Invention: 1. The process does not use reagents such as heavy metal azides, tri-n-butyl tin azide, and tri-n-Octyl tin azide, therefore environmentally safe. 2. Consequently there are no disposal problems. 3. The process is easy to perform and in less number of steps and hence economical. 4. The yield of Losartan produced is enhanced (>75%) and the purity of (>99%) 5. The process is commercially applicable. 6. The improved process yields a product free of carcinogenic impurities belonging to the N-nitrosamines family. 7. The process helps control the formation of carcinogenic impurities belonging to the N-nitrosamines family. 8. And also the process yields a stable product.